Technological Disruption

Of main interests to us is the use of mining as a part of in-situ resource utilization, that is: making it easier to industrialize and colonize space by removing the need to pay the sky-high delta-V cost of lugging raw materials up Terra's gravity well.

But in the early stages, asteroid mining start-ups cannot be established to provide minerals to space industrialization because there won't be any. No existing customers for their product. To get the ball rolling, the start-ups won't be looking for water ice or aluminum to sell to AsteroGobbler Inc. Instead they will be looking for gold and platinum to sell on Terra.

And that's when the spectre of Technological Disruption will raise its ugly head and make the powers-that-be turn red in the face with live steam angrily shooting out of their ears. Imagine the rage of a member of the 0.1% discovering that all their gold stocks are suddenly worth less than used toilet paper when some stupid rock-rat hauls a cubic mile of auriferous asteroid into LEO. And you thought the MPAA and the RIAA were were furious when internet piracy was invented. The 0.1% is going to do their best to outlaw asteroid mining.



     Celestial bodies like the Moon and asteroids contain materials and precious metals, which are valuable for human activity on Earth and beyond. Space mining has been mainly relegated to the realm of science fiction, and was not treated seriously by the international community. The private industry is starting to assemble toward space mining, and success on this front would have major impact on all nations. We present in this paper a review of current space mining ventures, and the international legislation, which could stand in their way - or aid them in their mission. Following that, we present the results of a role-playing simulation in which the role of several important nations was played by students of international relations. The results of the simulation are used as a basis for forecasting the potential initial responses of the nations of the world to a successful space mining operation in the future.

     The article is composed of three parts. The first section depicts the rationale for space mining and describes the current and future technological state of this field. In the second part, we portray the simulation. We analyze the political outcomes which should be addressed by the international community in the third part. We then conclude with some lessons for further discussion of potential mechanisms to mitigate the primary dilemmas and concerns which would be raised once the technology becomes a reality.

3. Simulations and roleplaying games as a forecasting method (second part)

     Roleplaying and war-games are a widely used method for forecasting decisions by two or more parties in a conflict. The origin for these methods stems from the 18th century, when officers and generals in the Prussian army utilized Kriegsspiel [“wargame”] to practice strategy and tactics. The Prussian victory in the Franco-Prussian war in 1871 was partly attributed to their use of wargames to provide superior training of their officers. Since then, roleplaying games have become an accepted method for forecasting the way in which conflicts are resolved in business, law and politics. Roleplaying is also used to train professionals for future events and cases; this practice is particularly relevant in the legal field.

     Roleplaying games have shown their merit, particularly in cases in which groups have conflicting and complicated wants and needs. Often in such cases, it has been discovered that even though negotiators can find a zone of agreement, they still fail to reach decisions that are accepted by all. It turns out that expert negotiators often do not realize the emotional and personal needs, desires and difficulties that shape the decision making process. Roleplaying games do not suffer from this oversight, since the players are asked to fully emulate a certain character or side, and the needs and desires of the characters are automatically absorbed into the game's decision making process.

     Roleplaying games are also of particular use when trying to forecast the impact and consequences of large changes. Experts have an advantage in understanding the results of small changes in their field of expertise, but they lose this benefit when confronted with major and disruptive changes that span many fields. Roleplaying games can provide a different venue for forecasting the results of such cases: the actors react to the changes by consulting with each other in real time, and providing solutions that rise from the group as a whole.

4. The scenario and process of the space mining simulation

     The scenario was designed with the help of space professionals with backgrounds in space engineering and technology, space politics and international law. The primary purpose was to produce a general, workable scenario that would serve as a starting point to trigger processes and trends in the international system. The simulation was conducted as part of a graduate class in Space Politics at Tel Aviv University, during the spring 2014 semester. The simulation game was presented to the students at the beginning of the semester. About 20 graduate students from the graduate program for security studies and the graduate program for diplomacy participated in the simulation. It should be noted that as often happens with graduate students in Israel, some of them had professional backgrounds in military service, the diplomatic corps, etc.

     The initial goal of the simulation was for the students to get a sense of the variety of issues related to the politics of space: political economy, environmental issues, power and security of states, cooperation, diplomacy and international relations, technology, international law, etc.; raise their awareness of actual political dilemmas; and enable them to have at least some first-hand experience in the related process. In conducting the simulation, we made no pretense that we were going to encompass all the issues related to space mining. Rather, the objective was to raise awareness of some of the major issues involved and encourage creativity in searching for potential solutions.

     The scenario began in the year 2035, in which Earth's population has grown dramatically, and alternatives must be found to the dwindling natural resources that are essential for the continued growth of the global economy. In an attempt to deal with this challenge, a number of private companies and national space agencies from the U.S. Russia, China, India, and Japan, have been working for several years on developing technologies to extract minerals from space and ship them back to Earth. In January 2035, “Human Welfare”, an American based company, is the first to successfully mine minerals in space and transport the cargo back to Earth. The shipment contains large amounts of gold and platinum, which are only a small part of the riches that the mined asteroid contains. Processing enterprises need to be established to transform the raw minerals brought to Earth into usable material for global industries. The technological demonstration, together with an optimistic business plan showing economic viability, produces a new economic and technological reality that has great political and economic implications. The immediate consequence on the global market is a dramatic decrease in the value of gold, the price of which fell by 50% on the World Mercantile Exchange Market. In light of these dramatic developments, the UN Office for Outer Space Affairs (UNOOSA) announces that the annual meeting of COPUOS, held every year in June, will be devoted to the issue of space mining. The meeting will take place in the form of open-ended consultations at UN installation in Vienna. Member states and observer states are invited to express their opinions and discuss the matter.

     Several factors contribute to the reliability of the forecasts produced by simulations and roleplaying games. In the experiment described herein, we made use of each factor, as follows:

4.1. Actors must take their role seriously

     It is believed that actors can largely be ignorant regarding the dispute in question, as long as they receive the relevant reading material on the subject, and take their role seriously. For that purpose, we asked graduate students to take part in the roleplaying game at the beginning of the semester, while the actual game was played at the end of the semester. First, each student was assigned to a country that he or she was to represent in the simulation. The first task, which lasted for two weeks, was that each student had to get acquainted with the overall characteristics of the country he/she represented: its economy, geo-strategic environment, political issues and so forth. Students were also asked to learn about the country's space policy and activities. Based on this information, in the second task, the students had to define and analyze their country's primary interests and considerations, and evaluate and asses the approach it would take regarding the new technological reality presented in the scenario. For this task students had four weeks to prepare. The final assignment was to prepare the actual simulation game, which was played at the end of the semester. It should be noted that from the beginning, students were aware of the fact that their final grades depended on their performance in all stages of the simulation game, including preparation for it. Thus, most of the students seemed to take their tasks seriously.

     To help students prepare for the simulation and specifically for their role in it, they were provided with a list of issues and questions to guide them in thinking about the various aspects of space mining and its potential consequences for world politics. For example, students were encouraged to think about the potential impact of space mining on the international balance of power, and whether they expected the present balance of power to change? Will the status of some nations change? Which countries would be interested in creating their own mining capabilities and companies, or at least directly benefit from the new developments? Which governments would object to space mining and act to stop or disrupt it? What can nations do to avoid or minimize potential damage to their economies?

4.2. Realistic environment

     The players need to feel as if they really were the characters they were supposed to be. We simulated the 78th meeting of UN-COPUOS. We provided each player with a flag of the nation they represented; as moderators of the event we conducted the game as though it was an actual meeting of the committee in question. The simulated discussion was divided into three parts. The first part began with a statement by the chairs of the session (played by the authors of this article), who called on the representatives of the different countries present to take responsibility and act together for stability and peace on Earth for future generations. The chairs then invited all the representatives to participate in the discussion. Students then delivered short national statements prepared in advance on behalf of their countries, in which they explained the country's approach and perspective towards the new reality. Among the issues raised in these statements were global challenges, global opportunities, national concerns and national objectives.

     The second part simulated a recess in the formal meeting. During this recess, the representatives had the option of approaching and interacting with other representatives, in order to discuss various ways of addressing the issues raised in the statements. The third part of the simulation was another formal session conducted as an open discussion in which the representatives commented on each other's statements. They raised potential mechanisms to mitigate challenges and ways to reach international collaboration. After a total of 3 h, the chairs closed the discussion, thanking all of the participants for their constructive participation. As the final semester assignment, the students were required to compose a position-paper advising the government of the country they represented about the expected new reality.

4.3. Allowing time for collaboration

     It is generally recommended to allow time for the parties involved to collaborate with each other, particularly if they're supposed to present a united front in the game. To that purpose, as noted, we allowed the players time before the game to think about their strategies and arguments, and also provided a recess period during which the players talked with each other informally and agreed on strategies and alliances for the rest of the game.

     Naturally, a simulation game, such as the one presented here, has limitations. In this case, limitations are primarily outcomes of the characteristics and requirements of the program under which this class took place. First, since this was a graduate class, it had fewer than 20 students. Thus, a large number of countries could not be included. For this reason, we decided not to include non-state organizations, which in real life may affect the future of space-mining. Second, it was not possible to conduct a long simulation. Third, the students were not space professionals, and therefore lacked technical and other relevant knowledge. Nevertheless, it turned out that this limitation was potentially an advantage, because students were very open-minded about the issues.

     Fourth, it must be noted that students from one country and culture are limited by necessity in their ability to emulate the mindset of people from other nations and cultures. While this limitation is difficult to mitigate completely, the students were asked to prepare for the simulation by reading about the nations they were representing, including details about their populations, cultures, and religious beliefs.

5. Simulation outcomes (third part)

     The discussion that ensued during the simulation can be divided into three main sections. First, the discussion concentrated on the possible consequences of the ability to transport materials mined from space to Earth on the stability of the international system and the world order. In this context, the right to exploit commonly held resources, ownership issues, share of profits and knowledge, were discussed. Second was a discussion of the potential opportunities for economic growth, development, and prosperity. In this context, ideas were also raised regarding the potential solutions for the distribution of technological development and the actual distribution of goods. A way was sought to enable a wide range of countries to benefit from the new reality, even if they do not directly engage in space mining, for example, by processing the imported space minerals on Earth.

     Third, a brainstorming session was held regarding the various mechanisms which could and should be developed at the global level. Such mechanisms will be necessary to mitigate the challenges, maximize the opportunities, and reach a broad international consensus among participant states regarding the conduct of world politics in the new international reality.

     The resulting discussion highlighted the tensions between powerful countries and less powerful or weaker countries in the context of the global struggle for resources and power. In general, the participants divided into three main groups of countries. The first group contained spacefaring countries, which have substantial space capabilities and are therefore capable of actively participating in mining minerals in space and transporting them to Earth. For the most part, this group contains the leading world powers. In the simulation, it became clear that the countries in this group compete with each other for leadership of the process of space mining, and the tangible goods and intangible benefits involved, such as the considerable political power accrued. Countries such as the US advocated for an approach that would not restrict development, and instead would encourage innovation and entrepreneurship, while searching for ways to facilitate proper solutions to reach international cooperation. For this reason, during the debate and in response to objections and criticism by other less developed countries, representatives of the leading spacefaring countries highlighted the fact that the new technological breakthroughs would be enjoyed by everyone. They would provide opportunities for all nations to improve their economies, and increase the well-being of their citizens. These statements were aimed at easing the antagonism of the less developed countries, and raising their solidarity and support, in order to achieve a most favorable world-wide political and psychological impact.

     Emerging spacefaring countries composed the second group. Under the leadership of the leading spacefaring nations, these countries were looking for ways to maximize their gains from the new reality. Representatives of these countries focused their efforts on maximizing their chances of taking an active part in the overall process, and upgrading their position in the evolving economy of space mining. The strategic approach they adopted was to find ways to integrate their country into the value chain of space mining, whether in outer space or on Earth as soon as possible and to the maximum extent, in a way that would assure long-term commitment of the leading countries. For example, they bargained with the leading spacefaring nations concerning the establishment of some of the infrastructure on their territories, and negotiated to be part of the future technological development through international collaborations.

     The third group consists of countries with no meaningful space capabilities. Many of the representatives of these countries argued against space mining and the transport of materials to Earth. For them, the new technological and economic reality is a distant and unreachable dream, which imposes serious threats for their economies and stability. In general, their approach represents a historic colonial tension. Their approach can be defined as a serious lack of confidence in the global diffusion of wealth. Many of them argued that the technological and economic development at stake widens the existing gap between them and the developed and advanced countries. They expressed deep concerns that the new reality would work against them, because it would perpetuate current economic and political gaps. Moreover, it would deprive them of their fair and proper participation in the global share of resources, and thus seriously damage their future chances of development. Some of them even demanded that space mining be banned. On a more practical level, they called for a much more inclusive process regarding space mining. In addition, the representatives of these countries called on the international community to develop mechanisms for compensation, which would be provided to them by the countries directly benefiting from space mining. This way, it was argued, they too would be able to enjoy and benefit from the new economic order, and the concept of the “benefit to all mankind” would have practical fulfillment.

     In addition, tensions were also reflected within each of the aforementioned groups. These tensions originated from differing national interests, various approaches to the management of innovation and the aspirations of individual countries in the international system. For example, in the group of spacefaring countries, there was disagreement between the U.S. and other countries, including some of its allies, which often took different positions regarding this issue. Russia and China expressed a more favorable approach to the developing countries, by calling for the development of global mechanisms of compensation.

     In the open discussion conducted in the third part of the simulation, a number of ideas about the proper ways to manage the new situation internationally were raised. Among them was the development of international mechanisms for regulation, licensing, and taxation of space mining, similar to other such international mechanisms, which were adopted in order to organize, regulate and control activities by nations in the global commons, such as the International Seabed Authority. In this capacity, the students suggested the establishment of a “world space bank”, which would be entrusted with the financial management of the revenues from the licensing and taxation. The money thus collected would be used to achieve the following global objectives:

  1. Financial compensation for the countries whose economies would be directly and significantly affected by the new economic order. These countries are generally the ones wherein the economies are based on minerals and natural resources, the value of which would significantly drop.
  2. Develop technological knowhow and expertise, as well as build up infrastructures, in countries lacking the national capacity to develop indigenous space expertise with their own resources. For example, the Space Bank would conduct training for students and professionals from developing countries, in order to enable these countries to develop initial national capacity in space technology. Another possible direction would be for the Bank to sponsor the establishment of space centers in these countries.
  3. Support the establishment of needed infrastructure in developing countries, so as to take part in the value-chain of space mining, especially on Earth.

     Provide funding for global activities to assure safe and sustainable use of space by all countries. For example, funding would be provided to a designated UN agency which would be responsible for monitoring and regulating space traffic, tracking space debris, and conducting active removal of such objects. This innovative idea of establishing a “world space bank” testifies to the creativity which is needed by all players in this “global game” i.e. spacefaring nations, emerging spacefaring nations and players with no significant capabilities. In order to avoid potential conflicts over this expected disruptive capability the challenge leading and emerging spacefaring nations are facing is to find ways to make as many nations as possible parties to the value chain of space mining. The challenge of weaker states is to persuade spacefaring nations to incorporate them into this chain. In addition, the adoption of such mechanisms would demands adaptation by the international legal framework.

5.1. Lessons about space mining

     The lessons of this simulation indicate several issues. First, the game highlighted different group behavior in world politics concerning the new reality, with a sharp distinction between the haves and have-nots. Second, it provides insight regarding different approaches to innovation on the national level and international level. Unsurprisingly, in general, the stronger countries operated according to the principles of “first come, first served”, while others held to the approach of “space for humanity”. Nevertheless, the strong players expressed a pragmatic approach, in which they expressed an understanding of the overall concerns and needs of the international community. They suggested ways to utilize the new reality for the development of mechanisms which would provide service to the overall space environment.

     The concerns raised by the representatives from the developing countries which lack minimal space expertise, regarding the expanded gaps between them and the leading spacefaring nations, are perfectly understandable. Nevertheless, is the strong opposition they expressed to the overall new reality indeed the strategy they should adopt? Would a compensation mechanism work in their favor and serve their long-term goals optimally? What does that tell us about international approaches to innovation and entrepreneurialism? We conclude that under the guise of a demand for a fair distribution of goods, the approach reflected by these countries in the simulation focuses on imposing restrictions on countries rather than on actually developing opportunities to get involved in the process. The focus on mechanisms of compensations rather than on mechanisms to develop capabilities may evolve to be a “self-fulfilling prophecy”, which will preserve and expand existing gaps. Further research is needed to examine the potential effect of compensation methods on the economy and innovation systems in these countries. In the long-run it may turn out that such methods do not optimally serve these countries, rather they will perpetuate their lack of development and lower status.

     An important concern raised by the US representatives was that restrictions on technological development could lead to stagnation and damage the spirit of innovation that pushes the market in general. Indeed, compensation mechanisms by themselves do not produce incentives and opportunities for development. In the long term, compensation mechanisms which are not followed by mechanisms for actual development of skills and knowledge perpetuate and exacerbate the gaps. Instead of resisting development and demanding compensation, these countries should act to achieve full partnership in space mining ventures, which would also contribute to their development.

     On the legal issue, motivation to further develop mechanisms and regulations for this new reality stems from the fact that most items included in the existing space treaties were established when human activity in space was dominated by governmental activity. Therefore, these treaties reflect the perspectives and needs of states. Nowadays, the development of private and commercial enterprises in space requires new perspectives and thinking regarding regulation.

     Finally, looking ahead to the time when space mining will become a reality, and given its positive potential and negative challenges, we advise that this issue be discussed in international forums sooner than later. Scholars and professionals should put their minds to the variety of technological, scientific, legal, political and economic issues that are expected to arise. By doing so ahead of time, they will be able to develop principles and frameworks that can maximize the benefits of the new reality while minimizing the risks to global stability.

5.2. Lessons for future simulations

     Overall, the simulation proved to be a success – both in pedagogically and in the way it encouraged thinking about a disruptive technological subject, identifying some of its complex consequences on the world, and devising ways to deal with them.

     When asked for insights about the simulation, the students' responses were overwhelmingly positive. Indeed, several students requested that such simulations be held throughout the semester, starting with an introductory session in which the students introduce their nations to each other.

     One of the students expressed his opinion in the following manner, which highlights the usefulness of the simulation as a way to analyze issues international relations:

“I actually understood how international relations are really made, who 'my friends' are, who's against me and who stands with me …. ”

     One of the main lessons derived from the simulation concerned the necessity of having breaks between the three discussion sessions. Breaks, even short ones of only a few minutes, enabled the participants to talk with each other privately, frequently reaching understandings and agreements ‘behind the scenes’. Coalitions and collaborations arose mainly as a result of such breaks in the discussions.

     We strongly believe that simulations and role playing games could be used to analyze and better understand other international situations as well, and look forward to conducting similar simulations in the future.

6. Conclusions

     In this study, we examined the potential impact that could result from a successful space mining venture, and the initial responses by nations around the world. We found that while spacefaring nations were largely eager to exploit resources from space, most developing nations in the simulation were far less excited about the possibility, and understandably feared that this technological breakthrough would disrupt their own growth and development by making their natural resources virtually worthless overnight.

     We believe that successful ventures in the field of space mining would have to address these international issues and tensions sooner or later. One potential solution that arose from the simulation was creating a mechanism of a Space Bank that would tax successful space mining ventures, and use the money to help promote space-related science and technology in developing nations. This Space Bank would thus serve as a ‘ladder to space’ that would support the advancement of all nations in their outreach towards outer space.

     The methodology underlying the simulation has proven to be particularly useful, both for teaching about this complex topic, and for promoting brainstorming and out-of-the-box thinking. We believe that similar simulations could be used to analyze the consequences of many other disruptive developments. Other simulations could be used, for example, to analyze the possibility of using the mined resources to sustain a “deep space economy”, or to examine the security risks posed by asteroids dragged into orbits around Earth. Finally, larger simulations in the future should include non-state actors, such as commercial firms, terrorist groups and representatives of the scientific community.

(ed note: see report for references)


      "So what,” a rather harsh voice declared. “I'm T. Semyon Braunstein, Administrator of NAUGA-State, and we want to talk to you about our gold which you have been dispensing in a very cavalier fashion."
     "You want it back, I take it?"
     "Damn straight! We know you made a big haul when you took over NAU-Ceres I and we do indeed want it back."
     "Well, now,” Cantrell said, “how much of your treasure am I supposed to have plundered?"
     "We frankly don't know,” Braunstein replied, “and the presumption is that all the gold you have is ours in absence of proof to the contrary."
     "That would appear to be arguable,” said Cantrell. “Let's stick to the facts."
     "How much did you take?” Braunstein asked.
     "One million four hundred and eighty thousand ounces. That's what, five tons? The entire lot was minted into Ceres d'Or and put into local circulation."
     "You issued gold-backed paper, too,” McQuayle said, “a lot more than any one and a half million ounces, by damn!"
     "So what? Gold-backed paper is paper, not gold."
     "We want the gold that's backing it up,” Braunstein said. “That's our gold, you pirate!"

     "Don't be such a (expletive deleted) fool,” Cantrell snapped. “Ceres—all the mines on Ceres—never produced more than about twelve million ounces a year. That's what—maybe forty tons. Today, here at Castillo Morales, I am depositing five thousand six hundred and sixty tons of gold. How did I get my hands on one hundred and forty-one years’ worth of your peak production, hey? Answer me that, clown!"
     There was a rather long pause as McQuayle and Braunstein digested the information. “Where did the gold come from, then?” Braunstein asked.

     "We used the big laser to refine a cubic kilometer of nickel-iron. It took us nearly a year."
     "How much gold was there?” asked McQuayle.
     "The nickel-iron assayed 0.75 ppm gold by weight,” replied Cantrell. “What's the weight of a cubic kilometer of nickel-iron, 8×109 tons?"
     "And you could run off another five or six thousand tons of gold next year?” Braunstein asked.
     "And the year after,” Cantrell agreed. “And the (Japanese) won't bother me about it because they have big lasers on most of their space stations, and most of the space stations with big lasers are close to large masses of nickel-iron. I've given them the whole technology."

     "The gold standard,” McQuayle said weakly, “you've just shot the gold standard in the ass—one location producing five thousand tons of gold a year! Fifty (asteroid colonies) would produce—what? Two hundred fifty thousand tons? And more would be coming on stream all the time … we pegged the dollar at eight hundred fifty to the ounce … we can't hold it there … we can't limit production—my God! What's our money going to be worth?"
     "I suggest you get a handle on the paper,” Cantrell said, “because if you stick with the gold standard, you're in for one hell of an inflation."
     "The gold mines on Ceres seem to be a bit redundant,” Braunstein remarked at last. “Do the Japanese realize that the gold you're dumping on them isn't worth (expletive deleted)?"
     "No. They think, like you did, that it was stolen from the NAU.” Cantrell paused for a moment to watch the forklift trucks moving the pallets of gold bars. “Premier Ito will be announcing our agreement in about ten minutes, at 1900. I told him we'd work out the details when I got back to Rosinante."

     "Well, goddamnit, get my financial advisors!” Braunstein yelled.
     "I beg your pardon?"
     "I wasn't talking to you, Cantrell."
     "You've totally destroyed the economy of the world,” McQuayle said. “What did you get out of it, Cantrell?"
     "Survival. The Japanese Fleet is already heading away from Rosinante. Besides, I expect the economy of the world will survive."

From THE PIRATES OF ROSINANTE by Alexis Gilliland (1982)

(ed note: Antonio has developed a magnetic array system that allows scanning circumstellar disks to detect asteroids with valuable deposits of rare metals. He has hired a ship to go scan an unexplored circumstellar disk and bring back a few megatons of gold)

      “Thank you, Captain. My colleagues and I want to fly the Lady Macbeth on a prospecting mission.”
     “For planets?” Roman asked curiously.
     “No. Sadly, the discovery of a terracompatible planet does not guarantee wealth. Settlement rights will not bring more than a couple of million fuseodollars (the empires are not on the gold standard, instead they are on the Helium-3 standard), and even that is dependant on a favourable biospectrum assessment, which would take many years. We have something more immediate in mind. You have just come from the Dorados?"
     “That’s right," Marcus said. The system had been discovered six years earlier, comprising a red dwarf sun surrounded by a vast disc of rocky particles. Several of the larger chunks had turned out to be nearly pure metal. Dorados was an obvious name; whoever managed to develop them would gain a colossal economic resource. So much so that the governments of Omuta and Carissa had gone to war over who had that development right.
     It was the Garissan survivors who had ultimately been awarded settlement by the Confederation Assembly. There weren't many of them. Omuta had deployed twelve antimatter planetbusters against their homeworld.

     “While we're waiting," Katherine said. “I have a question for you, Antonio.”
     She ignored the warning glare Marcus directed at her.
     Antonio’s bogus smile blinked on. “If it is one I can answer, then I will do so gladly, dear lady.”
     “Gold is expensive because of its rarity value, right? "
     “Of course."
     “So here we are, about to fill Lady Mac’s cargo holds with 5,000 tonnes of the stuff. On top of that you’ve developed a method which means people can scoop up millions of tonnes any time they want. If we try and sell it to a dealer or a bank, how long do you think we’re going to be billionaires for, a fortnight?”

     Antonio laughed. “Gold has never been that rare. Its value is completely artificial. The Edenists have the largest stockpile. We don't know exactly how much they possess because the Jovian Bank will not declare the exact figure. But they dominate the commodity market, and sustain the price by controlling how much is released. We shall simply play the same game. Our gold will have to be sold discreetly, in small batches, in different star systems, and over the course of several years. And knowledge of the magnetic array system should be kept to ourselves.
     “Nice try, Katherine," Roman chuckled. “You'll just have to settle for an income of a hundred million a year."

From ESCAPE ROUTE by Peter Hamilton (1997)

Avalloy and Demandite

Planets and colonies require certain elements for life support and others to support their industry. This is the market that the space miners are supplying. This will also determine which elements are worth the miner's time to prospect for, the more valuable elements will be the ones in either big demand, of extreme scarcity, or both.

As an economic abstraction useful concepts are Avalloy and Demandite.

An imaginary molecule which is composed of the weight fractions of the major metallic elements consumed by industry of a particular planet or colony. The sum of elemental abundances of metals that must be mined to support civilization, as it were. Sometimes it is assumed that avalloy is the renewable resources, since metals are easy to recycle.
An imaginary molecule which is composed of the weight fractions of the major non-metallic elements consumed by industry of a particular planet or colony. Sometimes it is assumed that demandite is the non-renewable resource fraction. Note that some space analysts do not use the term "avalloy", instead they define "demandite" as both the metallic and non-metallic elements.

The amount of avalloy and demandite that must be supplied to maintain one colonist for a year is the "per capita" avalloy and demandite requirement.

Understand that the composition of avalloy and demandite will be on a colony by colony basis, miners know there is no profit to be had carrying coals to Newcastle. For instance, on Terra water and air are not considered to be part of the local demandite, since they are assumed to be in unlimited supply. Terran demandite is instead dominated by fossil fuels. In space colonies local demandite has large proportions of water and air since they are in short supply. No fossil fuels are included due to abundantly available solar power. And the avalloy for 16 Psyche will contain no iron or nickel, since that is what the blasted asteroid is made of.


Secondly, and more subtly, the right elements have to be accessible on the planet for it to be colonizable. This seems a bit puzzling at first, but what if Centauri Bb is the only planet in the Centauri system, and it has only trace elements of Nitrogen in its composition? It's not going to matter how abundant everything else is. A planet like this—a star system like this—cannot support a colony of earthly life forms. Nitrogen is a critical component of biological life, at least our flavour of it.

In an article entitled "The Age of Substitutibility", published in Science in 1978, H.E. Goeller and A.M. Weinberg proposed an artificial mineral they called Demandite. It comes in two forms. A molecule of industrial demandite would contain all the elements necessary for industrial manufacturing and construction, in the proportions that you'd get if you took, say, an average city and ground it up into a fine pulp. There're about 20 elements in industrial demandite including carbon, iron, sodium, chlorine etc.

Biological demandite, on the other hand, is made up almost entirely of just six elements: hydrogen, oxygen, carbon, nitrogen, phosphorus and sulfur. (If you ground up an entire ecosystem and looked at the proportions of these elements making it up, you could in fact find an existing molecule that has exactly the same proportions. It's called cellulose.)

(ed note: actually, that turns out not to be the case. Cellulose does not contain nitrogen or phosphorus, both of which are vital. )


Demandite” is the word used by mineral economists to describe the materials that must be provided— usually by mining— to meet the needs of civilization. In the usual terrestrial setting, air and water are assumed to be freely available, and fossil fuel (natural gas, crude oil, and coal) is considered a necessity. In space, where dependence on solar energy is the norm, and where air and water must be “mined”, the numbers are different. The proportions of mineral needs, however, are otherwise generally similar. You can then ask how much of each material (iron, carbon, nitrogen, aluminum, copper, oxygen, water, nitrogen, etc.) is needed to be in circulation to support one person, depending on “renewable” (inexhaustible) solar energy to drive industry, agriculture, and recycling. We can then compare those requirements to the natural resources available on bodies in nearby space, and calculate how many people could be supported at each of those locations.

The proportions of these necessary materials (the relative abundances of water and iron, for example) are very different on the Moon, Mars, and nearby asteroids. The Moon, for example, is severely deficient in all volatile elements, including carbon, nitrogen, hydrogen, and chlorine, Mars, with its tenuous atmosphere and widespread ice deposits, fares better. But best by far is the match between the composition of near-Earth asteroids (NEAs) and “space-based demandite”. The 1000 or so kilometer-sized near-Earth asteroids contain enough of every essential element to support a population of 10 billion people from now until the Sun dies of old age. The NEAs, however, are a renewable resource: in nature, the rate at which NEAs are lost by collision with planets and ejection from the Solar System is compensated by recruitment of fresh asteroids kicked into near-Earth space by Jupiter’s gravitational interactions.

But what about the main Asteroid Belt? The answer is startling: the Belt contains one million times as much mass as the entire NEA population. Again depending on the Sun for power, the Belt could support a population of 10 million billion people— a million times the ultimate carrying capacity of Earth. With that many people, wouldn’t we be running out of solar power? Not really— even under these extreme assumptions, we would require less than one millionth of the Sun’s output energy.

The non-renewable resources available to Earth-bound humanity are finite. The resources available to a space-faring humanity are effectively infinite.


The ultimate objective of space industrialization is to create a growing economy in space which can eventually become self-sufficient. Space industry is presently supported by sales of goods with extremely high intrinsic values, such as satellites for communications, research, navigation and reconnaissance. Low-volume production of exotic goods in the zero-gravity and weightless conditions afforded in near-Earth space may broaden the market for space produced goods. However, in all these cases the cost of transporting the goods or raw materials into low-Earth orbit will add $200-$700/kg to the product price for a period of 15 years and thus place a sharp limit on the ultimate terrestrial market (ref. 1). There appears to be a way of circumventing the present high cost of launching materials from the Earth into space. This can be done by acquiring bulk raw materials from the Moon or asteroids and processing them in space into economically valuable products. Initial bulk material costs could be of the order of $25/kg in high-Earth orbit (see Salkeld appendix)and the cost would drop with experience. There would be two effects of lower material costs. First, the space economy could begin approaching the richness and cost structures of our present terrestrial economy. Secondly, the range of space products that could be sold for terrestrially-related use either in space or on Earth would be greatly expanded.

The Moon can supply most of the mass needed for large-scale industry in space. There are two ways to approach the proof of this statement. The first is to look in detail at the materials needed to construct specific products in space. At this point in time the production of space solar power stations is an attractive candidate because of the high value per unit mass of such objects and because of the large number of stations which could be required (>200 in next 30 years). Analyses even of designs not optimized for lunar elements reveal that at least 60 percent of the required silicon, aluminum and oxygen could be obtained from the Moon and the total mass lifted from Earth could be reduced about 80 percent by utilizing lunar materials.

Alternatively, one can compare the nonfuel distribution of nonrecoverable elements (weight fraction) utilized in the industrial economy of the United States with elements present in the lunar soil as is shown in table 1. The fraction of these elements which can be extracted with reasonable and presently available chemical processing techniques from beneficiated lunar ores is the subject of two companion papers (by Williams et al. and Rao et al.respectively) discuss extraction of Si, O, Fe, Al, Ti, and H2O. Using these and other proposed extraction procedures most of the components of the synthetic molecule of "Demandite", which constitute most of the nonfuel material inputs to American industry, could be provided in deep space at less cost per unit mass than the launch cost of the complete suite of the constituent elements directly from Earth in large tonnages until the mid-1990's.

Apollo 15
mare-low Ti
Bulk soil (1 unit)b
(Cu, Zn, Pb).00202.2 (-5)c90--.0020
Xd.0030 Σ -.05690.0189 Σ -.2951.15.0159--

bFormula = (Wt. fraction lunar element)- (Wt. fraction demandite).
c(N) ≡ 10N
dx - Mn, Ti, Cr, Ba, F, Ni, Ar, Sri, Br, Zr.
eImportant agriculturally.
fConcentrated in the smaller grains (<50μ)
gVirtually the complete suite of elements is present in these areas,
but their contributions (on the ppm and ppb levels) are lost in
the errors of the sum over the listed elements. Trace element concentrations may vary greatly from one site to another.

Notice in column 4 of table 1, that the major demandite components (Si, O, Fe, Al, Mg, X, Ca, Na, K, P, and S) are present either in adequate concentrations or in enrichments that are 10 times the specific fractions of the soil. Beneficiation of soil components to enhance and possibly simplify. known chemical extraction processes should be achievable using electrostatic, magnetic, dielectric and mechanical techniques and careful site selection. Elements such as Cu, Zn, Pb, H, Cl, N, C, and other trace elements comprise 8.4 percent of the demandite molecule. These elements would be shipped from Earth, eventually located from other sources, such as non-Apollo sites, or other materials substituted for them. In any event, it is clear that of order of 90 percent of the present day inventory of industrial elements can be provided from known lunar soils. Lunar soil processed to provide 90 percent of the demandite complement at $20/kg (i.e., Si, Al, Fe, Mg, Ca, and O) and the remainder supplied from Earth at $300/kg would provide the in-space demandite molecule at a cost of about $50/kg or 17 percent of the direct supply cost.

It is very clear, however, that substitution of materials, which is being required in the terrestrial economy even now, will permit much greater use of lunar materials both in general and for specific products. Thus, the cost of space "demandite" should approach the cost of the lunar processed materials.

The economic value to Earth of the Moon or the asteroids as a source of raw materials is strongly dependent on the total retrieval and elemental separation costs of the raw materials. Figure 1 is a qualitative description of the costs of goods or end-use-material on a dollar per kilogram basis (horizontal axis) versus the differential output of the total value of goods in the U.S. economy in billions of dollars per dollar per kilogram or (Δ109 $/($/kg)) for a total GNP of $1012.

Most goods now sell for less than $10/kg with most between $0.1/kg and $2/kg. Transport into low-Earth orbit (LEO) from the Earth presently adds more than $500/kg and thus confines goods produced in space to a tiny fraction of the potential terrestrial market (right of arrow 1 in Figure 1). Solar power stations are estimated to be economically feasible at $140/kg . Supplying the bulk of the required construction material from the Moon at $20/kg (arrow 2 in Figure 1) would clearly improve the economics and decrease the cost of the power supplied to Earth. If sources of industrial feedstock can be developed in deep space with costs of less than $0.5/kg (arrow 3 in Figure 1) then many of the Earth-produced goods can be considered for potential space manufacture. It is conceivable that industrial material can be supplied at such low costs from the Moon or asteroids assuming normal industrial "learning curve" experience occurs.


In-situ Resource Utilization

Naturally, if anything you boost into orbit is going to cost $5000 per kilogram, it would be a vast savings if you could find some of the stuff you need already up there. This is called In-situ Resource Utilization (ISRU). Currently the only ISRU NASA has managed is harvesting solar power in space, but believe me they are working on it.

Solar power cells could be manufactured from materials present on the lunar surface.

Water is one of the most useful substances available in space. It can be electrolytically split into oxygen and hydrogen for use as chemical rocket fuel or hydrogen for nuclear thermal rocket propellant (Tony Zuppero called water-ice "Rocket-Fuel Ore"), astronaut breathing mix or later use in regenerative fuel cells. Water can be used straight (instead of hydrogen) by a nuclear thermal rocket, abet with a performance penalty. It can be used to create hydrogen peroxide, which is a rocket monopropellant. It can be drunk by astronauts, fed to hydroponically grown plants, used as coolant, or used as radiation shielding. Large amounts of water have been discovered on the Lunar poles. Phobos and Deimos are thought to have ice, with Deimos ice being closer to the surface. The Jovian moons Callisto, Europa, and Ganymede have ice, though Callisto is the only one clear of Jupiter's radiation belt. Europa might have liquid water due to tidal stress.

Rob Davidoff and I worked up a science fiction background where the Martian moon Deimos becomes the water supplier for the entire solar system. We call it Cape Dread.

Aluminum and oxygen can be used as chemical rocket fuel, though the specific impulse is a pathetic 285 seconds. This is made up for by the fact that aluminum and oxygen is quite plentiful in lunar regolith, i.e., it's in the dirt.

Titanium is useful for constructing rocket-powered vehicles due to its absurdly low mass for its strength (though iron is better for space stations and bases). It can be found in Lunar Ilmenite ore. Philip Eklund suggests that "foamed" titanium will be used in space habitats as a low-mass construction material, he calls it "space wood." Isaac Kuo notes that foam titanium is only good for compression members, it is counterproductive to foam tension members.

Iron is better for constructing stationary non-rocket-propelled installations. A good source is M-type asteroids. The ultimate M-type asteroid is 16 Psyche, future home of the Asteroid civilization steel industry.

Some asteroids contain water, some contain iron, and some have siderophilic metals. The latter include Cobalt, Iron, Iridium, Manganese, Molybdenum, Nickel, Osmium, Palladium, Rhenium, Rhodium, Ruthenium, Platinum, and Gold. One small asteroid rich in siderophiles probably has enough yellow metal to crash the entire world-wide gold market.

For purposes of refueling nuclear rockets, a source of fissionables would be nice. This is covered in more detail on this page.

Helium 3 is a splendid fusion fuel. The atmosphere of Saturn is a great place to harvest He3. Jupiter is closer but harder to get to the He3. No, the He3 found on the surface of Luna is so sparse that it is not worth mining. 15 to 50 ppb is pathetically low grade ore.

Nuclear thermal rockets can use a variety of propellants that are available as ices in the colder parts of the solar system. This is what Jerry Pournelle calls "Wilderness re-fuelling", Robert Zubrin calls "In-situ Resource Utilization", and I call "the enlisted men get to go out and shovel whatever they can find into the propellant tanks". And remember that mass drivers can use anything as propellant, even dirt and rocks.

In the Traveller role playing game, they borrowed Jerry Pournelle's wilderness refueling concept. Starships have scoops allowing them to skim the atmosphere of a gas giant in order to harvest free hydrogen for fusion fuel.

However, there are a couple of elements that will have to come from Terra. In particular, nitrogen and phosphorus are vital for agriculture, but there are no rich off-Terra sources. Phosphorus is life's bottleneck, and nitrogen is fertilizer. There is a bit of phosphorus in C-type asteroids and a wee bit on Luna in areas with KREEP. Nitrogen is in ammonia, which can be found in the atmosphere of gas giant planets (which are quite a long ways away) and in large amounts in the atmosphere of Titan.

This could be a large club that the government of Terra waves at the extraterrestrial colonies, if they start making noises about rebelling from Terra's oppressive control.


Many people assume that the Moon is the "logical next step" in space development; it is, after all, the closest source of raw materials in space. But why go to the Moon for resources?

Access to Asteroids

The Moon's proximity offers obvious advantages: short travel times make human crews safer and cheaper, and brief light-lag eases control of remote operation. If, however, initial "mining" operation will simply fill bags with loose material, then virtually unsupervised devices—sweeper robots—seem practical; neither travel time nor light-lag then matter much, and the advantages of proximity fade. As space industry grows, human beings will have the run of the Solar System; even earlier, semi-autonomous robots could likely handle more than mere dirt-sweeping. Meanwhile, complex processes can be confined to near-Earth space.

The relative motions of Earth and any given asteroid make good transfer opportunities relatively infrequent, and infrequent transfers would increase the inventory cost of resources stockpiled for use between deliveries. The main cost tied up in this inventory, however, would be that invested in its transportation. Low delta v's, aerobraking, and use of efficient, low-thrust propulsion systems promise to make the transportation cost of asteroidal materials far less than that of lunar materials; this seems likely to swamp the effect of inventory costs.

Still, a systems analysis would be needed to quantify the costs of infrequent launch windows. For example, how greatly will scheduling inefficiencies decrease the useful operating time of propulsion systems? How rapidly do such costs lessen as the number of surveyed target asteroids grows? Such factors can only be estimated now, but the overall prospects look good. With many target asteroids, more windows will open and such costs will lessen; a modest search should find many as accessible as the best now known. Further propulsion systems (such as Lightsails) could make many known asteroids easy to reach. Asteroids seem more accessible than the Moon, despite their greater distances.

Orbiting Ores

The sheer size of the Moon increases the possibilities for ore formation, at least compared to those in a smaller version of itself. Separation on a vast scale, however, matters less than the degree of concentration. If some process swept up all the uranium in a typical cubic kilometer of the Earth's crust (the volume of a small asteroid), the resulting block of uranium would mass over 10,000 tons. If, however, all the uranium in Earth's crust were concentrated a hundredfold, a block more massive than any asteroid would result, but it would hold a mere 400 parts per million. Greater concentration would be worth more than greater quantity, particularly to a small-scale industry. Uranium itself, of course, seems worth little in free space, given the steady flood of sunlight.

Separation processes have concentrated materials in both the Moon and asteroids. Geochemists classify elements as siderophile (chiefly found in the iron phase), chalcophile (chiefly found in the sulfide phase), lithophile (chiefly found in the rock phase), and volatile (chiefly found—or lost—in the vapor phase).

The Moon is enriched in refractory lithophile elements, but at the expense of depletion in siderophile, chalcophile, and (especially) volatile elements.

The asteroids, in contrast, vary: rocky asteroids are enriched in lithophile elements; nickel-iron asteroids are enriched in siderophile elements (and often hold nuggets of sulfide); carbonaceous chondrite asteroids, while not enriched in volatiles (compared to the Sun or Jupiter), nevertheless contain abundant water and hydrocarbons. Some asteroids, such as the chondrites common near Earth, hold a separable mixture—grains of metal and sulfide in a rocky matrix containing traces of water and carbon. The Moon's separation discarded too much.

The refractory lithophiles include aluminum, titanium, and magnesium; these may seem attractive for space use, since they are "aerospace metals." Asteroidal (that is, meteoritic) samples hold up to 27% aluminum oxide, and some carbonaceous chrondrites contain veins of water—soluble magnesium salts—the Moon has no monopoly on such metals.

Surprisingly, however, space industry has little special need for light metals. "Aerospace" today suggests vehicles, devices flung about repeatedly (or thrown very high) by burning fuels; low mass is important to their performance. Space industrial facilities— factories, stations, power plants—will be different: in use, they will simply orbit, as would a feather or boulder. Added mass can even help, by blocking radiation and slowing orbital decay.

Simple delivered cost seems most important, and this will include the costs of both transportation and refining. Energy requirements can indicate relative costs. Call the energy needed to lift a kilogram from the Moon one unit. Returning a kilogram from a target asteroid will require less than one unit; melting and refining a kilogram of asteroidal steel will require about a half a unit. The energy needed to break a kilogram of light metals free from lunar oxides, however, is roughly ten units. Further, asteroidal steel can be melted and refined using inexpensive heat from a solar furnace, while planned processes for reducing lunar oxides require expensive electric power. Process complexity issues likewise seem to favor steel.

For low-cost space construction, asteroidal steel seems best; a low-expansion nickel-iron alloy (Invar) could be used to avoid thermal distortion. Where low mass matters, graphite and plastics are becoming popular, and asteroidal hydrocarbons provide a feedstock unmatched on the Moon. For market value on Earth, precious and strategic metals from asteroids seem attractive. I know of no lunar materials superior to terrestrial ores. (The suggestion that lunar titanium might find a terrestrial market was incorrectly attributed to me in The High Frontier, O'Neill apparently confused me with another researcher.) Asteroids, however, hold siderophile metals like those that sank to Earth's core— separated, yet not beyond reach.

Speculative Prospects

Stephen Gillett discusses the possibility of lunar ores enriched in incompatible elements (those not easily incorporated in crystals of common minerals as magma cools and solidifies). He notes that water is commonly considered vital to concentrating incompatible elements in the residual liquid as magma solidifies, but proposes that traces of chlorine and sulfur might have played a similar role to that of water in the dry lunar magmas; KREEP (a rock widely distributed on the Moon, which is highly enriched in incompatible elements potassium [K], Rare Earth Elements and Phosphorus [P]) shows that some concentration occurs. The experiments he suggests seem well worth doing, to see if ores containing "chlorine, lithium, beryllium, zirconium, uranium, thorium, the rare-earth elements, and so forth" might indeed have formed. These elements are not critical to early space development, however, and chlorine—perhaps the most valuable, given its many uses in industrial chemistry—makes up 0.8% of the soluble salts found in carbonaceous chondrites.

One can equally well speculate regarding possible asteroidal ores not yet seen in terrestrial samples, of course. The Moon has been sampled in relatively few sites; likewise, most meteoritic samples are thought to come from relatively few parent bodies. Some classes of meteorite are represented by but one specimen, suggesting that some—represented by none—remain unknown. Nickel-iron meteorites contain a spectrum of nickel content ranging up to 34%—except for one that contains 62%. Our lunar samples contain grains thrown from far across the lunar surface; do they contain comparable evidence for unusual concentrations of valuable materials?

The asteroids, though smaller and faster-cooling, seem a match for the Moon as targets for speculative prospecting. Vesta, for example, appears basaltic and differentiated (like the Moon) and has over one-tenth the Moon's diameter. Many meteorites were melted and resolidified; asteroidal materials contained water, which perhaps mobilized incompatible elements. Further, comparing rock to rock, metal to metal, and sulfide to sulfide, concentrations of trace elements have been found to vary from sample to sample by factors of several hundred or more.

Hydrothermal processes (surely lacking on the Moon!) form many terrestrial ores; they require porous rock saturated with water, together with heating to drive convection, dissolve compounds in a large volume, and deposit them in a smaller volume. Some carbonaceous chondrites show veins of water-soluble salts; other signs point to their having been water-saturated for at least a thousand years. The cores of some asteroids melted, showing the presence of ample heat. Thus, hydrothermal deposits are not inconceivable. Similarly, deposits formed by volatilization and subsequent condensation in vents seem possible; metals such as tin and lead might be concentrated by such a mechanism. Finally, the composition of asteroidal rocks before and after their melting and differentiation strongly suggests that a sulfide phase, troilite, may be found in massive veins. One troilite-rich meteorite is known; any pure troilite meteoroids are thought to be destroyed by atmospheric entry (as are those carbonaceous chondrites richest in water and organics). In short, the asteroids' known resources seem better than the Moon's, and their unknown resources seem more promising.

An Asteroid Scenario

To make the idea of asteroid mining more vivid, a scenario may help. How might the process begin, and where could it lead?

First, we drop our eyes from the splendor of the full Moon, shake our heads to clear them, and look seriously at the choice of asteroidal resources vs. lunar resources. In part for scientific reasons, we support asteroid missions and the Spacewatch asteroid-search telescope. Recognizing the high thrust-to-weight ratio of metal films in sunlight (and their lack of fuel consumption), we better define Lightsail construction procedures and configurations. Agreement grows that asteroids have valuable, accessible resources. Space industry draws investment. Probes survey newly found asteroids to select the best targets for initial use. Government and industry decide that a fraction of the price of the Shuttle is little to pay to open the Solar System; Lightsail development begins in earnest.

Lightsail production begins in orbit, and sails depart for nearby asteroids. They deliver devices that sweep loose regolith into bags, then they return the bags to low Earth orbit. Engineers use the mass as radiation shielding for habitable modules of space stations, and for hardening military satellites. The Russians protest dirt in orbit as "an anti-satellite weapon." Water from carbonaceous chondrites is electrolyzed, producing cheap fuel in orbit for hydrogen/oxygen rockets; radiation shielding and fast, inexpensive rockets lead to a construction base in geosynchronous orbit.

Total sail capacity grows steadily as orbital factories continue production. Selected asteroidal steels are purified, removing over $1,000 of platinum metals per ton, then foamed in zero gravity for sale on Earth. Steel structures become common in orbit. The orbital industrial complex expands. Mass production of sails lowers the transport cost from certain asteroids to less than $l/kg; use of asteroidal nickel in sail reflectors further lowers the cost to $0.10/kg. Nickel and cobalt, then steel, follow platinum to markets on Earth. Steam turbine power satellites with steel radiators become economical. Space industry rivals genetic engineering and electronics as a growth sector in the Western economy.

An expedition at last departs to build industrial facilities at the two most accessible asteroids, to pre-process metals and organic materials for shipment and easy capture through atmospheric braking. With cheap steel and water, space stations become large enough to hold parks and gardens, then grow still larger. People stay longer. They bring their families.

With cheap fuel, the cost of reaching the lunar surface drops dramatically. A Moon base is built using asteroidal steel and propellants; for scientific and sentimental reasons advocates of Moon mining have an uphill battle against the conventional wisdom about space development. In time, however, the Moon becomes a source of aluminum and titanium for use in space industry, since it proves to be richer in these materials than are the more accessible asteroids.

This scenario assumes use of Lightsails; asteroidal resources would remain attractive even using ion engines, deployable solar sails, or chemical rockets burning liquid oxygen and hydrogen (LOX) and liquid hydrogen (LH2) from electrolyzed asteroidal water.

Twenty-eight years ago, in a fit of political hysteria, the U.S. took a path that bypassed building a shuttle and space station, building instead a giant missile to fulfill an ancient dream. In 1969 it reached its goal, but at a great price to true space development: the "Moon shots" dominated the news about space, and made spaceflight seem like an expensive stunt. The space program collapsed afterwards.

Today, it is said that a lunar base is the logical next step. There is even talk of lunar colonies, far from the terrestrial markets that could pay for them. Let us turn our eyes from the "romance" of the Moon—long enough, at least, to consider sailing on sunlight to mine steel, water, gold, and platinum from flying mountains.

From ASTEROIDS: THE BETTER RESOURCE by Eric Drexler (1992)

(ed note: The Supersonic Dust Roaster heats lunar or asteroidal regolith until it is molten and extracts the oxygen. It will operate in both low-gravity (on asteroid) and microgravity (in orbit) conditions.)

Regolith (pulverized minerals) is heated resistively in a crucible until it melts and becomes conductive. Inductive heating raises the temperature to 3000°K, at which point the vapor pressure over the melt reaches approximately 100 kPa, and includes a large fraction of molecular and atomic oxygen. A de Laval nozzle fitted to an aperture into the vapor chamber creates a supersonic flow of the vapor. As the superheated vapor passes down a drift tube, it cools to the point where suboxide minerals condense and flocculate into agglomerates.

As these accrete further their supersonic inertia turns them into ballistic particulates, disengaged from the gas flow. Oxygen, which remains a gas until a frosty 90°K, can be culled out of the stream with molecular skimmers and captured into praseodymium cerium oxide adsorbate beds.

This patent pending system works great in calculations, but what material can withstand such temperatures with an atmosphere containing highly-reactive monatomic oxygen?

Thorium oxide has the highest temperature of any ceramic, melting at 3300°K. It is already oxidized, and can withstand the energetic monatomic oxygen, making it ideally-suited to the Dust Roaster’s need. However, thorium is mildly radioactive.

As a result of this research effort, the team was able to identify three candidate materials for the Dust Roaster. Thorium oxide could not be entirely discounted. The radiation dose received from an astronaut working on the Dust Roaster is far less than that received due to background radiation from the sun and from highly-energetic galactic cosmic rays. Oxides of hafnium or yttrium would be a good second choice, and when properly stabilized, provided a modicum of cooling is included in the Dust Roaster design. As a third choice, a mixed ceramic based on zirconium oxide is readily available, inexpensive, and there is an abundance of experience working with this material. Keeping this material cooled below its softening point will require a thermal management system, a challenge since the thermal conductivity is quite low.

For the details, read the patient

From AC 2008-969: Ultra-High Temperature Materials For Lunar Processing by Peter Schubert and Kara Cunzeman
Al-O2 rocket
Al-O2 rocket
Exhaust velocity2,648.7 m/s
Thrust292,600 N
Specific Power112 kg/MW
Engine Power500 MW
Frozen Flow eff.79%
Thermal eff.98%
Thrust Power387 MW

Solar Carbothermal Refinery

Although aluminum is common in space, it stubbornly resists refining from its oxide Al3O2. It can be reduced by a solar carbothermal process, using carbon as the reducing agent and solar energy. Compared to carbo-chlorination, this process needs no chlorine, which is hard to obtain in space. Furthermore, the use of solar heat instead of electrolysis allows higher efficiency and less power conditioning. The solar energy required is 0.121 GJ/kg Al.

The aluminum and oxygen produced can be used to fuel Al-O2 chemical boosters, which burn fine sintered aluminum dust in the presence of liquid oxygen (LO2). Unlike pure solid rockets, hybrid rockets (using a solid fuel and liquid oxidizer) can be throttled and restarted. The combustion of aluminum obtains 3.6 million joules per kilogram. At 77% propulsion efficiency, the thrust is 290 kN with a specific impulse of 285 seconds. The mass ratio for boosting off or onto Luna using an Al-O2 rocket is 2.3. In other words, over twice as much as much fuel as payload is needed.

Gustafson, White, and Fidler of ORBITECTM, 2010.

Carbochlorination Refinery

Metal sulfates may be refined by exposing a mixture of the crushed ore and carbon dust to streams of chlorine gas. Under moderate resistojet heating (1123 K) in titanium chambers (Ti resists attack by Cl), the material is converted to chloride salts such as found in seawater, which can be extracted by electrolysis.

The example shown is the carbochlorination of Al2Cl3 to form aluminum. Al is valuable in space for making wires and cables (copper is rare in space). The electrolysis of Al2Cl3 does not consume the electrodes nor does it require cryolite. However, due to the low boiling point of Al2Cl3, the reaction must proceed under pressure and low temperatures.

Other elements produced by carbochlorination include titanium, potassium, manganese, chromium, sodium, magnesium, silicon and also (with the use of plastic filters) the nuclear fuels 235U and 232Th. Both C and Cl2 must be carefully recycled (the recycling equipment dominates the system mass) and replenished by regolith scavenging.

Dave Dietzler

From HIGH FRONTIER by Philip Eklund

The Sabatier reaction or Sabatier process was discovered by the French chemist Paul Sabatier in the 1910s. It involves the reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures in the presence of a nickel catalyst to produce methane and water. Optionally, ruthenium on alumina (aluminium oxide) makes a more efficient catalyst. It is described by the following exothermic reaction:

CO2 + 4 H2 → CH4 + 2 H2O + energy
∆H = −165.0 kJ/mol
(some initial energy/heat is required to start the reaction)

International Space Station life support

Oxygen generators on board the International Space Station produce oxygen from water using electrolysis; the hydrogen produced was previously discarded into space. As astronauts consume oxygen, carbon dioxide is produced, which must then be removed from the air and discarded as well. This approach required copious amounts of water to be regularly transported to the space station for oxygen generation in addition to that used for human consumption, hygiene, and other uses—a luxury that will not be available to future long-duration missions beyond low Earth orbit.

NASA is using the Sabatier reaction to recover water from exhaled carbon dioxide and the hydrogen previously discarded from electrolysis on the International Space Station and possibly for future missions. The other resulting chemical, methane, is released into space. As half of the input hydrogen becomes wasted as methane, additional hydrogen is supplied from Earth to make up the difference. However, this creates a nearly-closed cycle between water, oxygen, and carbon dioxide which only requires a relatively modest amount of imported hydrogen to maintain.

Ignoring other results of respiration, this cycle looks like:

The loop could be further closed if the waste methane was separated into its component parts by pyrolysis:

The released hydrogen would then be recycled back into the Sabatier reactor, leaving an easily removed deposit of pyrolytic graphite. The reactor would be little more than a steel pipe, and could be periodically serviced by an astronaut where the deposit is chiselled out.

Alternatively, the loop could be partially closed (75% of H2 from CH4 recovered) by incomplete pyrolysis of the waste methane while keeping the carbon locked up in gaseous form:

The Bosch reaction is also being investigated by NASA for this purpose and is:

CO2 + 2H2 → C + 2H2O

The Bosch reaction would present a completely closed hydrogen and oxygen cycle which only produces atomic carbon as waste. However, difficulties maintaining its temperature of up to 600°C and properly handling carbon deposits mean significantly more research will be required before a Bosch reactor could become a reality. One problem is that the production of elemental carbon tends to foul the catalyst's surface, which is detrimental to the reaction's efficiency.

Manufacturing propellant on Mars

The Sabatier reaction has been proposed as a key step in reducing the cost of manned exploration of Mars (Mars Direct, Interplanetary Transport System) through In-Situ Resource Utilization. Hydrogen is combined with CO2 from the atmosphere, with methane then stored as fuel and the water side product electrolyzed yielding oxygen to be liquefied and stored as oxidizer and hydrogen to be recycled back into the reactor. The original hydrogen could be transported from Earth or separated from martian sources of water.

A variation of the basic Sabatier methanation reaction may be used via a mixed catalyst bed and a reverse water gas shift in a single reactor to produce methane from the raw materials available on Mars, utilizing water from the Martian subsoil and carbon dioxide in the Martian atmosphere. A 2011 prototype test operation that harvested CO2 from a simulated Martian atmosphere and reacted it with H2, produced methane rocket propellant at a rate of 1 kg/day, operating autonomously for 5 consecutive days, maintaining a nearly 100% conversion rate. An optimized system of this design massing 50 kg "is projected to produce 1 kg/day of O2:CH4 propellant ... with a methane purity of 98+% while consuming 700 Watts of electrical power." Overall unit conversion rate expected from the optimized system is one tonne of propellant per 17 MWh energy input.

Detailed chemical reactions

(ed note: Note the slight problem with using the Sabatier process to make rocket fuel:)

The stoichiometric ratio of oxidizer and fuel is 2:1, for an oxygen:methane engine.

CH4 + 2 O2 → CO2 + 2 H2O

However, one pass through the Sabatier reactor produces a ratio of only 1:1.

(ed note: the problem being that the process as is does not generate enough oxygen to burn with all the methane being produced)

More oxygen may be produced by running the water gas shift reaction in reverse, effectively extracting oxygen from the atmosphere by reducing carbon dioxide to carbon monoxide.

Another option is to make more methane than needed and pyrolyze the excess of it into carbon and hydrogen (see above section) where the hydrogen is recycled back into the reactor to produce further methane and water. In an automated system, the carbon deposit may be removed by blasting with hot Martian CO2, oxidizing the carbon into carbon monoxide, which is vented.

A fourth solution to the stoichiometry problem would be to combine the Sabatier reaction with the reverse water gas-shift reaction in a single reactor as follows:

3 CO2 + 6 H2 → CH4 + 2 CO + 4 H2O

This reaction is slightly exothermic, and when the water is electrolyzed, an oxygen to methane ratio of 2:1 is obtained.

Regardless of which method of oxygen fixation is utilized, the overall process can be summarized by the following equation:

2 H2 + 3 CO2 → CH4 + 2 O2 + 2 CO

Looking at molecular masses, we have produced sixteen grams of methane and 64 grams of oxygen using four grams of hydrogen (which would have to be imported from Earth unless Martian water was electrolysed), for a mass gain of 20:1; and the methane and oxygen are in the right stochiometric ratio to be burned in a rocket engine. This kind of in-situ resource utilization would result in massive weight and cost savings to any proposed manned Mars or sample return missions.

From the Wikipedia entry for SABATIER REACTION

The Sabatier reactor uses In-Situ Resource Utilization (ISRU) to create a closed hydrogen and oxygen cycle for life support on planets with CO2 atmospheres such as Mars or Venus.

It contains two chambers, one for mixing and the other for storing a nickel catalyst. When charged with hydrogen and atmospheric carbon dioxide, it produces water and methane. (The similar Bosch reactor uses an iron catalyst to produce elemental carbon and water.)

(ed note: CO2 + 4 H2 → CH4 + 2 H2O + energy)

A condenser separates the water vapor from the reaction products. This condenser is a simple pipe with outlets on the bottom to collect water; natural convection on the surface of the pipe is enough to carry out the necessary heat exchange.

Electrolysis of the water recovers the hydrogen for reuse.

NASA 2007.

From HIGH FRONTIER by Philip Eklund

Upon arrival on the Martian surface the ISRU-3 system will begin to generate fuel for the (CM-3/SM- 3/SLV-3) from the atmospheric Carbon Dioxide and on-board cryogenic Hydrogen via the Sabatier process (Figure 41). An optional process of using water electrolysis is possible if significant amounts of trapped/frozen water are found. In this case the PSV-2 could be used as an excavator of the material needed to feed soil/water/frozen CO2 stock material into the Mars ISRU plant.


There has been considerable, if preliminary, investigation into using resources found on Mars to produce propellants to refuel rocket transports. This is part of the larger concept of space settlement called in situ resource utilization (ISRU); essentially “living off the resources of the new lands.” ISRU involves the collection, processing, storing, and use of materials encountered in the course of human or robotic space exploration through full settlement to replace materials that would otherwise need to be brought from Earth at very high cost.

Elon Musk has indicated that SpaceX will exploit this approach to produce the propellants needed to refuel his reusable Big Falcon Rocket (BFR) during Mars transport missions. The BFR propellants include densified liquid methane and oxygen. This series of articles will take a first order engineering look at some of the leading ideas for establishing production plants for the propellants to fuel a BFR on Mars. Also reviewed are associated, potentially marketable, by-products, and especially the energy that may be required for the production processes in the context of emplacement considerations of such a commercial enterprise.

The saying goes that ideas are what could happen, while engineering is about making things happen. So when considering selection and integration of system technologies for the reactant/product recirculation and separation of such a Martian propellant processing plant, many real-life factors, including physics and chemistry, must be the basis for consideration. In this case, this includes addressing separation of ISRU products under relevant operating conditions, regeneration approaches for filters, membranes, and/or sorption beds, the integration of thermal control systems for operation in the colder Mars environment, pressure differences caused by separation processes, and the effects of lower Mars gravity. Specific examples of first order propellant processing plant separation and recirculation engineering design considerations that have already been identified are:

  • Carbon dioxide (CO2) and water (H2O) harvesting from the Martian environment and their purification (with possible importation augmentation);
  • Generation of methane (CH4) from ISRU carbon dioxide and obtaining hydrogen for use in a Sabatier processor subsystem;
  • Water separation from >250°C exhaust hydrogen and methane in a Sabatier subsystem or from carbon dioxide and carbon monoxide (in a reverse water gas shift processor subsystem);
  • Water and carbon dioxide electrolysis processing and operating option needs;
  • Carbon dioxide/carbon monoxide (CO) separation from 350°C (in a reverse water gas shift subsystem) or up to 900°C (solid oxide electrolysis) stream of mixed gases with recycling of carbon dioxide;
  • Hydrogen (H2)/methane separation post water separation with recycling of the hydrogen;
  • Removal of water from saturated oxygen gas (O2) and methane product streams before liquefaction of the products;
  • Overhead power including recirculation pumps and compressors that operate continuously exposed to the Mars environment.

It should be pointed out that NASA’s NextSTEP-2 program seeks to investigate ISRU space resource utilization technology.1 Their vision is to progress from our current “Earth-reliant” approach to exploration and eventually become “Earth independent” in space. NextSTEP uses a public-private partnership model that seeks commercial development of deep space exploration capabilities to support more extensive human spaceflight missions in and beyond cislunar space. NASA anticipates that the results of these efforts over the ensuing years will provide the needed engineering details for full-up ISRU system developments.

1. Sabatier Processing Subsystem: The Sabatier methanation reaction has been recommended by many of the top researchers as the most likely basis for an ISRU propellant production processing plant on Mars. This is driven primarily because this process can exploit the extremely high availability of carbon dioxide in the Martian atmosphere to create both the methane fuel and water, which can be broken down into useful hydrogen and the oxygen oxidizer needed to run the BFR engines.

CO2 (g) + 4H2 (g) ⇋ CH4 (g) + 2H2O (g)
ΔH = –165.0 kJ

The Sabatier reaction or Sabatier process was discovered by the French chemist Paul Sabatier in the 1910s. It involves the reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400°C) and pressures in the presence of a catalyst to produce methane and water. Nickel or, more optimally, ruthenium on alumina (aluminum oxide) acts as the catalyst.2 The methane gas is the end propellant product. The water produced acts as the feedstock for later propellant plant processing and other process products.

Since the Sabatier reaction occurs rapidly enough to be useful at about 400°C, a source of heat is needed to get the reactor up to its operating temperature. This will likely be provided by some form of an electric heater. Fortunately, once started, the reaction produces its own thermal energy. This means that, except for reactor conductive losses and process thermal management makeup, once the initial temperature is achieved, the reaction provides the majority of the heat to continue the reaction. So this part of the process is not continuously demanding high energy input.

For this first order analysis it is assumed that the energy for this initial reactor start-up has already been expended and loss make-up is low so that it is not a driving requirement to the conceptual design. Instead it will be booked for more detailed consideration during detailed design engineering.

The low temperatures on Mars also mean that careful design attention to proper insulation of the reactor for thermal management is required. Also, as with any chemical reaction, continuous process control monitoring will be needed in the subsystem design to maintain reaction temperatures within optimal bands to obtain the highest production yields.

Once produced, the Sabatier reactor methane gas product outputs will need to go through a separator to remove process-generated water vapor. The collected water vapor is assumed to be collected, rather than expelled as manufacturing waste. The collected water would be thermally conditioned by taking advantage of the cold Martian atmosphere using exterior radiator to condense the water vapor into liquid water, and then be directed to water storage tank(s) for later processing or product sale.

Design and management for liquid water storage tanks needs to carefully consider. This is driven by the average recorded temperatures on Mars of –63°C. These Martian temperatures are well below the freezing temperature of water. Further, this temperature varies from a maximum temperature of 20°C and a minimum of –140°C at the polar regions depending on time of year and distance from the equator. Consideration of the local conditions in which the plant will operate are important input design factors in engineering of the heat exchanges, pipe insulation requirements, and thermal management subsystem design.

A rigorous design process will use heat exchanges and water circulators to tap the incoming warm water vapors from the Sabatier process to help maintain the water in liquid form. For purposes of this study, the energy necessary for circulating pumps is anticipated to be minimal, compared to other primary demands in the processing. The circulating pumps should thus account for a minimal amount of overhead energy estimated in the processing plant budget.

The Sabatier process needs a source of free hydrogen to react with the carbon dioxide to produce methane. A partial source that can be used to obtain the needed hydrogen is through the electrolysis of the water by-product that results from the Sabatier reactor. Unfortunately, for every 44 kilograms of carbon dioxide that is converted into 16 kilograms of methane in the Sabatier process, you need four kilograms of hydrogen. The Sabatier process only produces 36 kilograms of water in the balanced reaction. This means an external source of additional “make-up” hydrogen is required for continuous reactor processing. Unfortunately, free hydrogen gas on Mars is essentially nonexistent.

Instead, an additional source of water is needed to obtain the make-up hydrogen feed stock for the Sabatier reactor. Potential sources of this water could come either from Mars ISRU or could come as an imported commodity from Earth or other celestial bodies, such as the Moon. Water sourcing and further propellant processing to obtain the needed hydrogen and to produce propellant oxygen oxidizer is covered in section 3 below. (Authors clarification note: For purposes of this first order analysis, the extremely small amounts of water obtained from the Martian atmosphere are an infinitesimal contribution to water supplies needed and are not included in the results).

A 2011 prototype test operation was conducted that harvested carbon dioxide from a simulated Martian atmosphere and reacted it with hydrogen. This test produced methane gas at a rate of one kilogram per day, operated autonomously for five consecutive days maintaining a nearly 100 percent conversion rate. An optimized system of this design massing 50 kilograms “has been projected to produce 1 kg/day of O2:CH4 propellant… with a methane purity of 98+% while consuming 700 Watts of electrical power.” Overall unit conversion rate expected from the optimized system is one metric ton of propellant per 17 megawatt-hours energy input.3 So assuming all feedstock is available to feed the processing the power to produce a full load of methane (in gaseous form) for a BFR (240 tons) is estimated to be in the neighborhood of 4.1 gigawatt-hours.

2. Raw Material Sources for Sabatier Process: Before Sabatier reactor production can occur, the raw materials for processing must be obtained. Surveys and spectral findings to date indicate that the carbon dioxide required for the Sabatier reaction is an abundant resource in the Martian atmosphere. Even though the atmospheric pressure on Mars is very low—less than one hundredth of Earth’s—the Martian atmosphere consists of almost 95 percent carbon dioxide. Despite its thin atmosphere, this Martian concentration is almost 20 times as much carbon dioxide as is in an equivalent amount of the Earth’s atmosphere.

However, like on Earth, the Mars atmosphere contains other gasses. In addition to carbon dioxide, the Martian atmosphere also has about three percent nitrogen (N2) and trace amounts of oxygen and water. (For completeness, it should be noted that there are also miniscule amounts of other gases. These miniscule gases should not impact propellant processing. These include argon, neon, krypton, and xenon.) This means a gas separation system is needed prior to feeding the Sabatier processing to remove nitrogen gases and trace amounts of oxygen and water to obtain processing-quality carbon dioxide purity.

Carbon molecular sieves (CMS) are the method commonly used on Earth in the separation processing of air. CMS’s belong to the activated carbons family and can be obtained by various procedures to create pores narrowing to smaller sizes than 10 angstroms. This allows CMS’s to be used to separate the carbon dioxide from the nitrogen. A desiccant, oxidizing reactive bed or adjusted chill/pressure cycle to freeze out the oxygen and remove water should also be considered as an engineering solution method to separate these trace constituents from the atmospheric carbon dioxide in Martian propellant processing plant designs.

However, with high costs of transport for the various CMS and desiccant materials from Earth, it may be more practical to simply expend the additional power instead using a multi-stage chiller pressure cycle subsystem to separate the Martian atmospheric constituents. An example of this processing is the fractional distillation process. On Earth, this process uses cryogenic air separation units (ASUs) to separate nitrogen, oxygen, and often to co-produce argon. The process separates gases by cooling the gas at specified pressures until the individual gas components condense at a given temperature into a liquid which is then extracted. The downside to using this process is that it is a very energy-intensive operation due to the operation of multiple turbo-compression cycling and associated condensation.

The other primary issue of the raw Martian atmosphere is the presence of moderate to significant amounts of dust. In some cases, dust storms have covered virtually all of Mars. When considering design solutions, the dust removal methods that require minimal maintenance, lowest operating costs, and that will maintain continuous plant intake are most desired. For this reason, remove-and-replace mechanical filters, such as those in home furnaces, are not desirable. Vortex swirl particle separator designs would likely be a better option. Regardless, this dust will need to be removed from the Martian ISRU air intake as well during atmospheric pre-processing.

For purposes of this first order review, the key design selection metric for Mars propellant production is to reduce electrical power needs. Since the CMS units will only require minor ongoing electrical needs, they are used for carbon dioxide atmospheric extraction in this review. The CMS power needs only includes the electricity needed by fans to force the gasses over the CMS materials and dust filtration to remove any dislodged CMS particulates. The CMS electrical needs are accounted for in the propellant plant power overhead budget.

Further, the import costs to transport and the set-up needed for the CMS material in the propellant production facility is assumed to have already been completed. Future engineering detailed design and economic viability investigations should take closer looks at these system engineering factors.

(Author’s additional note: It is interesting to note that with profitable expansion of propellant production, the technology appears to exist for making CMS by using local 3-D printing units and ISRU materials. The additional expenses associated with the electricity for mining, refining, and printing the CMS versus the use of multi-stage chiller pressure cycles will be a design/cost trade for future process expansion selection considerations.)

A key to efficiently designed Martian propellant plant—or, for that matter any off-world processing plant—is that the production system reaction products should not waste potentially marketable or usable manufacturing byproducts. For example, the nitrogen extracted from the atmospheric gas separation processing is a potentially exploitable/marketable product. Nitrogen is often used for flushing of tanks and lines through which other gases pass because it is reactive neutral. Then too, the oxygen and water atmospheric separated byproducts are both potentially valuable feedstock for making propellant oxidizer or for life support. For this reason, designing engineers will need to consider options, means, and costs in any facility design with business analysts to determine the costs to market value of any manufacturing byproducts.

3. Water ISRU Sourcing on Mars: Most space scientists currently agree that vast deposits of water appear to be trapped within the ice caps at the north and south poles of Mars. Frozen water also now appears to lie beneath the Martian surface at lower latitudes. Scientists have discovered a slab of ice they estimate is as large as California and Texas combined in the region between the equator and north pole of the Red Planet. Other regions of the planet may contain undiscovered frozen water as well. Specifically, some of the high-latitude regions seem to boast patterned ground shapes that may have formed as permafrost in the soil that froze and thawed over Martian geologic history.

Water mining on Mars will require the development of its own extraction and processing facility. Shipped in from places like the Moon, water may also be an early economically viable purchase alternative. This imported water would require development of lunar water mining, production, and Martian logistics transport architecture. If such commercial capabilities are in place at the establishment of a Mars BFR propellant plant, a certain amount of imported water might prove cost-effective (or simply unavoidable) during the build-up transition to full ISRU water mining and processing production. The selection and cost-effective balance of water sourcing will require additional future detailed system engineering and business trades plus operational business management monitoring over the production plant’s operating life.

For this first order review, it is assumed that an affordable means of extracting and processing of pure quality water will be identified from Martian ISRU water sources. In a 2016 planning study for NASA to examine Martian ISRU methane/oxygen processing, the use of Martian water ore was investigated.4 That study examined four cases of water ore processing. Robotic vehicles, such as the NASA KSC Regolith Advanced Surface Systems Operations Robot (RASSOR) prototype or the OffWorld Inc.5 smart robots, are likely candidates for mining the raw “water ore”.

For this investigation’s ISRU review, the NASA study four-kilowatt-hour figure was used for the power estimates used by robotic water extraction/mining unit operations. Including the power needs to then load the water ore and transport this water ore feedstock adds another 25 percent to this number, for a total of five kilowatt-hours to mine 4,150 kilograms of water ore. The 7.5-kilowatt-hour examples from the NASA study were then used for power estimates of the separation and vitalization processing to produce 33 kilograms of refined pure quality water from the mined Martian water-bearing regolith ore. This gives an energy cost of extracting and processing (with an overhead factor) to produce purified water from Martian raw ore materials at an estimate of about 230 watts per kilogram. Using this ISRU water source to make up roughly half of the needed water to fuel the Sabatier processor will require roughly two gigawatt-hours of power to mine, produce, and deliver the makeup hydrogen for a single BFR propellant load.

The next article in this series will cover the remaining propellant production processes, while the third installment will investigate options for producing the power necessary for BFR propellant ISRU-based production.


  1. Next Space Technologies for Exploration Partnerships-2 (NextSTEP-2), Appendix D: In-Situ Resource Utilization (ISRU) Technology, Broad Agency Announcement NNH16ZCQ001K-ISRU, Originally Issued by NASA: December 4, 2017.
  2. Sabatier reaction, Wickipedia.
  3. Zubrin, Robert M.; Muscatello, Berggren (2012-12-15). “Integrated Mars In Situ Propellant Production System”. Journal of Aerospace Engineering. Jan 2013. Vol 26: Issue 1, pp 43–56. doi:10.1061/(asce)as.1943-5525.0000201. ISSN 1943-5525.
  4. Mars Water In-Situ Resource Utilization (ISRU) Planning (M-WIP) Study. NASA Briefing, 22 April, 2016, contributors: Angel Abbud-Madrid, David Beaty, Dale Boucher, Ben Bussey, Richard Davis, Leslie Gertsch, Lindsay Hays, Julie Kleinhinz, Michael Meyer, Michael Moats, Robert Mueller, Aaron Paz, Nantel Suzuki, Paul van Susante, Charles Whetsel, Elizabeth Zbinden.
  5. OffWorld Web site

(ed note: the analysis below shows how inefficient it is to ship Lunar Water to LEO by using chemical rockets. Naturally it becomes better if you use a propulsion system with a higher exhaust velocity or something like a Lunar Space Elevator or related concept. The latter is what he is referring to when he mentions "propellantless methods")

One of many important issues that doesn’t get enough airtime when discussing lunar In-situ Resource Utilization (ISRU) is how to efficiently get the propellants and other materials off the lunar surface. There seems to be a line of thinking that could be called “all we need is ISRU” that says that lunar ISRU is the most critical technology and everything else is just a distraction.

While it is possible to take propellant produced on the lunar surface up to Low Lunar Orbit (LLO) or to one of the Earth-Moon Lagrange points using similar rockets to what you landed with, and then deliver this to Low Earth Orbit (LEO) using entirely propulsive tugs with no new technology, this isn’t very efficient. You end up spending a significant fraction of the lunar derived propellant lifting both the delivery propellant and the landing return propellant, as well as the propellant to ship the cis-lunar tanker back to LEO and bring it back for refueling near the Moon.

To give you an idea of how inefficient, I’m attaching a spreadsheet with some back-of-the-envelope level calculations to illustrate this point. In the spreadsheet I model a Lunar Surface to LLO or EML-2 and Back tanker, and then an LLO or Earth-Moon Lagrange Point 2 (EML-2) to LEO and Back tanker. In both cases, I assumed they were about Centaur size (~23 tonnes), and used RL-10 based propulsion. For the reusable lunar surface tanker, I gave two propellant mass fractions – 90% (aggressive once you factor in landing hardware) and 85% (more conservative). For the cislunar tanker, I assumed a 90% propellant mass fraction, and also analyzed cases where an aerobrake was provided that weighed 5% of the Gross Takeoff Weight (GTOW) and 10% of the GTOW.

In the most extreme case of “all you need is ISRU” thinking, where you use entirely existing chemical propulsion systems for getting propellants from the lunar surface to LEO, only 9-11% of the propellant produced on the Moon actually makes it to LEO. Alternately, this means you have a “gear ratio” (ratio of propellant extracted on the Moon to propellant delivered to LEO) of 9-11. Not only is this very wasteful, but it means that you would need to size your ISRU capacity significantly higher than if you had a more efficient system.

Of the approximately 12km/s of round-trip Delta-V from the lunar surface to LEO and back, there are several options you can use to improve your gearing ratio, each of which attack a different leg of the journey:

  1. Stage and refuel in LLO or EML-1/2 (which was already assumed for this analysis).
  2. Aerocapture/braking to go from your Trans-Earth Injection trajectory into LEO
  3. Propellantless methods for launching from the lunar surface to LLO, EML-1 or 2, or even directly to LEO.
  4. Propellantless methods for landing on the Moon from LLO or EML-1 or 2
  5. Propellantless or high-Isp methods for traveling from LEO to LLO or EML-1 or 2.

This series is focused on options #3 and #4, though #2 is also low-hanging fruit (and provides about a 2-3x gear ratio improvement over the baseline “all we need is ISRU approach).


Citizen Joe:

I've found that Jupiter's radiation belt and wind speeds make it unsuitable for direct harvest.

However, that same radiation belt (and corresponding magnetic fields) could be used for 1) power 2) transportation and 3) spallation of useful elements into needed isotopes.

The last one is an interesting prospect from the mineral spewing volcanic Io. I don't actually recommend colonizing Io, but rather maintaining essentially ion farms within the radiation belt. The other moons are suitable for exploration, but Callisto (the outermost Galilean Moon) is protected from the solar winds by Jupiter's magnetosphere while being far enough away to reduce the radiation exposure. So, if I were to set up a Jupiter base/colony it would be there. That base would hold vast subsurface tanks of water for aquacultures and a whole biosystem. Waste heat from the reactors would be used to keep the tanks temperature regulated and the whole environment could be expanded in a modular manner depending on the waste heat requirements.

Fun fact: It takes two weeks to get receive the same radiation dose on Callisto that you receive on Earth every day. Moving in to Ganymede (the next closest moon) you would get week's dose of radiation in one day.


Resource harvesting is a major draw for investment in space. Two main classes of resources are important in the near term, with three additional classes becoming important in future decades.

First up is water. It is perhaps the easiest substance to extract and purify and is thought to be abundant in chondrite asteroids. It is also present on the Moon, Mars and Ceres, though Mars is an unlikely source of water for shipment back to LEO. Water can be split to provide oxygen for breathing gas or oxidizer and hydrogen for propellant or other chemical uses (Sabatier process for life support or as a fuel cell input for electricity). There is an immediate market for potable water on the ISS and will presumably be a strong market at any future space station. Water depots are another potential customer assuming future satellite RCS transitions from hypergolics to electrolyzed water.

Next is rare elements, mainly platinum group metals. These are abundant in metallic asteroids, with asteroid 16 Psyche alone representing perhaps 110 billion tons of PGM (at 5 PPM). Early efforts will probably focus on bodies of 100-200 meter diameter rather than 200+km diameter, but the supply is out there. Some detractors claim that dumping tons of precious metals on the market will crash prices. Certainly prices will go down if a new and abundant supply comes online, but platinum's value comes from more than being shiny. There are many potential uses for platinum that are not cost-effective today. A massive increase in supply would lead to a technological expansion of similarly massive proportions. Regardless, there is an immediate market for PGMs and other rare elements on Earth; any operator that can land their payload safely will be able to sell it easily any time they choose.

The latter categories are a bit similar. First is construction materials like iron, nickel and other metals (aluminum, calcium, magnesium, titanium, cobalt, tungsten) that might be used to build structural parts and pressure vessels. Next is semiconductors and dopants, mostly silicon but including gallium, germanium and indium plus tin, arsenic, antimony, aluminum, phosphorus, boron and gallium. These would be used to build solar panels, LED lights and potentially microprocessors. Last is whatever is left over, the slag from other processing. This is generally useful for radiation shielding (as is water) and would be used for manned craft and facilities outside Earth's magnetic field. A fourth category might be carbon and any trace nutrients required for plant life, though these materials would be separated as part of the refining process for structural metals and high-purity semiconductors.

All of the latter categories require a significant presence in orbit with the capacity to manufacture complex parts. This is definitely not a near-term environment, so the 'early days' operators are reduced to just water and platinum as potential products. Given the significant complexity involved in extracting platinum, I expect water to be the first non-Earth resource sold.

Ice Mining

As I mentioned previously, when it comes to the industrialization and colonization of space, water is the most valuable substance in the Universe.

However, as anybody who has carried a bucket of water knows, it has plenty of mass, which makes it very expensive to ship from Terra into orbit. Which is why people planning space colonies are so interested in In-Situ Resource Utilization, which in this case is a fancy way of saying "trying to find an ice mine." It would be so much more convenient if the water was already there, so you didn't have to go to the insane expense of importing it.

Sources of water:

  • The poles of Luna
  • The Martian moons Phobos and Deimos, with Deimos ice being closer to the surface. Rob Davidoff and I worked up a science fiction background where the Martian moon Deimos becomes the water supplier for the entire solar system. We call it Cape Dread.
  • C-type (carbonaceous) asteroids are about 10% water
  • D-type asteroids have almost as much water ice as comets
  • The Jovian moons Callisto, Europa, and Ganymede have ice, though Callisto is the only one clear of Jupiter's radiation belt. Europa might have liquid water due to tidal stress.
  • The particles composing the Rings of Saturn are almost entirely water ice
  • Comets have the most water ice of all small bodies (although it has other nasty stuff like hydrogen cyanide). Comets are about 40% water ice (50% volatiles, 50% dust; of the volatiles about 80% is water ice). Note that extinct comets have had most of their ice burned away by Sol


by James Davis Nicoll(2018)

The Frost Line is the point where water ice remains frozen during the formation of the solar system. For our solar system this has been calculated to be from 2.7 Astronomical Units to 3.1 AU.

The Snow Line is the present distance at which water ice can be stable (even under direct sunlight). For our solar system this has been calculated to be 5.0 AU.

BsnowLine = sqrt( SlumBolo / 0.04)


BsnowLine = start of snow line (Astronomical Units)
SlumBolo = Bolometric Luminosity
sqrt(x) = square root of x

Multiply AU by 150,000,000 to convert into kilometers


Momentus Space is a space tech company offering a ‘water plasma rocket’ – basically a helicon thruster that uses water as propellant (not ‘fuel’ as the energy has to be added via a power source). A helicon thruster is an electrodeless electric thruster that uses microwave energy from a ‘helicon’ antenna to flash heat the propellant into plasma. As the hot water doesn’t touch the electrode supplying the energy, there’s no corrosion of the drive system. Thus it can run for long, long periods of time. The water plasma (ions of hydrogen, oxygen and hydroxide plus their loose electrons) rushes out and produces a Specific Impulse (Isp) of 700 seconds in the small initial system being marketed. That’s better than burning hydrogen and oxygen to make hot fast steam, like a Space Shuttle Main Engine, which typically gets about 460 seconds Isp in space. And most long term propellant mixes that store well in space, like monomethyl hydrazine+nitrogen tetroxide, manage about 300 seconds.

But… there’s a down-side to all electric rockets. Power has to be supplied to the engine and it’s a LOT. Unlike chemical fuels, which react to release the energy they store, an electric rocket needs electrical power to turn Propellant into Push (3 P’s, Power-Propellant-Push). An Isp of 700 seconds translates into an effective jet velocity of about 6,865 m/s, which means a kinetic energy of 23.6 megajoules per kilogram of propellant shot out the back of the drive. Jetting that 1 kilogram in a second at 6,865 m/s produces a push (an impulse) of 6,865 newton-seconds. If the satellite+rocket combination masses 300 kilograms, then it’d accelerate at 6,865 kg.m/s2 / 300 kg = 22.9 m/s2, which is probably excessive for a satellite already in orbit. It’d also require powering the jet with at least 23.6 megawatts of power – and probably more like 32 megawatts of power, if we take rocket efficiency into account.

If we dial down the impulse per second to just 1 newton, rather than 6,865, then the acceleration would be a leisurely 3.33 mm/s2 and the power needed more like 4.5 kilowatts. That’s still a lot, but more feasible to provide. If half the mass on board is propellant, then the total time to use it is 12 days. The mass-ratio of empty to full is 2. Thus, thanks to the Rocket Equation, we can compute the total delta vee as LN(2) x 6,865 m/s = 4,758 m/s. If we start in Low Earth Orbit (LEO) that’ll get us much of the way to Geosynchronous Earth Orbit (GEO), but much of the time will be spent in the worst bits of the Van Allen radiation belts. The satellite can be hardened to take the punishment, but it eats into the actual ‘payload’ we’re delivering to its new orbital home.

The other option, if we’re using water, is to turn it into hydrogen and oxygen, to then fill up a rocket that can burn it at high thrust and deliver our GEO bound satellite in mere hours rather than days (NB: most available electric rockets would actually take months, due to their higher power demands and smaller thrust.) If we react hydrogen and oxygen to make water, then the energy released per kilomole (18.015 kilograms of H2/O) is 241.83 megajoules. That’s 13.42 megajoules per kilogram of fuel mix. So the reverse process, breaking water into hydrogen and oxygen, means applying at least that much to water to break it apart. The usual process assumed is electrolysis, which uses electrical potentials to break up the water molecules, and it’s typically 70-80% efficient. Then the resulting gases need to be cooled and compressed into liquid form so they can stored. Total is 15.33 megajoules per kilogram. At 80% efficiency that means 19.16 MJ/kg.

An Orbital Fuel Depot, splitting water to make fuel, powered by ~20 megawatts, would then make 1 kilogram of fuel per second, thus over 30,000 tons per year. That’d deliver about 20,000 tons of annual payload to GEO, which is much more than present traffic levels. If there’s about 450 active GEO satellites, with average lifespans of 15 years, and each masses about 6 tons, then 30 replacement satellites need to be launched each year, thus about 300 tons of fuel per year is a good starting goal.

A side note: At the end of its useful life, of about 15 years, a GEO satellite is then is parked in a higher orbit – a ‘graveyard orbit’ – to open orbital space for functional satellites. At least if the satellite owners are responsible corporate citizens.

Thus the Orbital Fuel Depot needs about 0.2 megawatts of power to provide fuel for Space Tugs serving the GEO satellite trade. If we use solar power, that’d be the largest single array ever launched, but it doesn’t have to be heavy. Reflectors that concentrate sunlight onto high temperature solar cells can minimise the mass and the total area of expensive semi-conductors such solar cells are made of.

Question is: What’s the best source for the water?

Of course Earth might seem a logical choice. The Throw-Away Falcon Heavy promises about 60 tons of payload to LEO. Thus 5 Falcon Heavies per year could supply the water. Total RP-1/LOX propellant required 1,400 × 5 = 7,000 tons. Fully Reusable Falcon Heavies might deliver 30 tons to LEO, so 10 launches of those would be enough. Some 14,000 tons of RP-1/LOX. A bit further along and the Big Falcon Rocket promises 100 tons to LEO. Just 3 launches required, but about 4,000 tons of LCH4/LOX required per BFR, thus 12,000 tons total. Another option is to mine water on the Moon, then deliver it to LEO via H2/O2 rockets. A Moon Tug could launch from the surface into an Earth Transfer Orbit for a delta-vee of about 2.5 km/s with aerobraking into LEO. The Moon Tug plus a payload of 100 tons water masses about 120 tons, but needs about 173 tons of H2/O2 to launch from the Moon, then return the empty Tug to the Moon. That does put the whole process into question, since supplying 300 tons of water in LEO to make into H2/O2 also means having to make about 519 tons of the same to use on the Moon. Thus about 2.5 megawatts of power supply delivered to the Moon. That might not be excessively onerous, especially if the Moon’s regolith (‘soil’) can be turned into solar panels as some have suggested.

Momentus Space’s Water Rocket becomes relevant at this point. If the Moon Tug delivers water to a waiting Water Rocket in Low Lunar Orbit (LLO), which then returns it to LEO via aerobraking, then it only needs about 100 tons of H2/O2 for every 100 tons water delivered. The orbital design will require some finesse. Low thrust orbits aren’t like high-thrust orbits. The total delta-vee required is significantly higher. In the case of the LEO-to-LLO round-trip mission, the total delta-vee can be up to 18.8 km/s, which would be a prohibitive additional water cost. That’s LEO-to-LLO and back, solely under thrust. So rather than thrusting the whole way, the Water Rocket thrusts away from LLO into Earth’s Sphere of Influence and a low perigee aerobraking orbit, the delta-vee I’m assuming is more like 2 km/s one-way. Getting back to the Moon however incurs the low-thrust delta-vee penalty, but only the Water Rocket is returning, sans 100 tons of payload. The return delta-vee could be up to ~9.4 km/s, but hopefully it’ll be less via careful orbital design. Alternatively, we might make water containers that can aerobrake themselves, and then be repurposed as pressure vessels in LEO once emptied. The Water Rocket could then free-return to the Moon after delivery, so long as perigee isn’t too low.


Chief product for Space Tug operators in LEO is water decomposed into H2 and O2. However the stoichometric mix of decomposed water is deficient in water. The mass ratio of the O/H2 is 15.9994 / 2.016 = 7.9362. High performance rocket engines run on a 6:1 mix, thus leaving an excess of oxygen. First thought is to sell it for breathing gas, but that’s a lot more than the ISS needs. However what if a bit of the hydrogen is reacted (very carefully with catalysts in CO2 solvent) with the oxygen to make hydrogen peroxide? By itself hydrogen peroxide is a pretty good monopropellant, getting up to 180 seconds Specific Impulse (Isp). Mixed with a bit of ethanol and it’s even better. The usual space-storable monopropellant is hydrazine, which is toxic and nasty. Hydrogen peroxide, in spite of its shortcomings, is nowhere near as bad.

The other market for lunar products is On-Orbit Servicing of existing GEO Satellites. While hydrogen peroxide makes for a decent replacement for hydrazine – given the right engines, so there’d need to be some retrofitting – Water Rockets, which are water propellant-using helicon thrusters, might be even better for station-keeping in the long term. The higher Isp means the refueling schedule is less frequent. The fact that the market is in GEO means the gravity a low thrust system struggles against is reduced more than 40-fold. Water Rockets could service GEO from LLO. Space Tugs could also be stationed in GEO, refueled from a Water-to-Fuel Facility based in GEO. The delta-vee to an aerobrake orbit to LEO is about 1.5 km/s, with about 0.08 km/s to then circularise in LEO parking orbit to meet the cargo. Then a high-thrust burn for Geosynchronous Transfer Orbit (GTO) to carry a Comm-Sat to its new home.

And the peroxide? On the Moon it actually makes for a decent energy storage system during the 14 days Lunar night. Peroxide powered high efficiency turbines can provide power for whatever night time activities a mostly Solar powered Water Mine will engage in. Perhaps that’s when most of the science activities the Base facilities can be hired out for will take place.

From A WATER ECONOMY IN SPACE II by Adam Crowl (2018)

The closest place to look is Luna. Unfortunately data from the Apollo moon missions suggested that the lunar regolith was drier than an old slab of concrete lying in the Sahara desert. Luna's "day" is 27 or so Terran days long, exposing Luna's surface to the merciless rays of the Sun and baking it to an oven-like temperature of 390°K. Any water-ice on the surface would have evaporated into space a long time ago. Even if an occasional water-ice comet smacked into Luna, the Sun's rays would make it go away.

But wait a minute. What if there were places on Luna that were permanently in shadow? Since there is no appreciable atmosphere, an area in Lunar shadow can drop down to a frigid 35°K. Any comet-ice that landed in such a deep-freeze would be preserved quite nicely.

The walls of lunar craters will provide shadow for part of the lunar day, but eventually the sun will be over head, the shadow will vanish, and the comet ice will evaporate. Except for at the lunar north and south poles. There the angle is steep enough that the sun's rays never penetrate the interior of the craters. See the picture, it shows the illumination of the lunar south pole over an entire lunar day. The dark areas are always dark. Any ice deposited there will still be there, patiently waiting for thirsty lunar colonists.

Lo and behold, it is there!

In In September 2009, India's Chandrayaan-1 space probe got a fleeting glimpse of lunar water-ice. In November 2009, NASA's LCROSS space probe watched as its spent upper stage violently crashed into the lunar south pole at 10,000 km/h, spotting ice crystals in the explosion. Finally in March 2010 the Chandrayaan-1 observed a bit of ice in the lunar north pole, a bit over 600 million tonnes of nearly pure water ice.

The lunar poles are going to be valuable real estate.


Water reserves found on the moon are the result of asteroids acting as "delivery vehicles" and not of falling comets as was previously thought. Using computer simulation, scientists from MIPT and the RAS Geosphere Dynamics Institute have discovered that a large asteroid can deliver more water to the lunar surface than the cumulative fall of comets over a billion year period. Their research is discussed in an article recently published in the journal Planetary and Space Science.

At the beginning of the space age, during the days of the Apollo program, scientists believed the moon to be completely dry. At these earliest stages in satellite evolution, the absence of an atmosphere and the influence of solar radiation were thought enough to evaporate all volatile substances into space. However, in the1990s, scientists obtained data from the Lunar Prospector probe that shook their confidence: the neutron current from the satellite surface was indicative of a larger fraction of hydrogen at the near-surface soil of some regions of the moon, which one could interpret as a sign of the presence of water.

In order to explain how water could be kept on the moon's surface, scientists formulated a theory known as "cold traps." The axis of the moon's rotation is nearly vertical, which is why in the polar regions there are craters with floors that are never exposed to sunlight. When comets consisting mostly of water ice fall, evaporated water can gravitate into those "traps" and remain there indefinitely, as solar rays do not evaporate it.

In recent years, lunar missions (the Indian Chandrayan probe, the American LRO, data from the Cassini probe and Deep Impact) have brought scientists two pieces new information. The first is that there are indeed considerate quantities of water and hydroxyl groups in the near-surface soil on the moon. The LCROSS experiment, in which a probe purposely crashed onto the moon resulting in the release of a cloud of gas and dust that was later studied with the use of a spectrometer, directly confirmed the existence of water and other volatile substances. The second piece of new information came when the Russian LEND apparatus mounted on board LRO generated a map of water distribution on the moon's surface.

But this second piece has only partly proven their theory: the map of "cold traps" did not correspond to the map of water deposits. The scientists had to refine the theory, and the idea of "lunar congelation" was proposed. It allowed accepting that "survival" of water ice in the regions exposed to sunlight is possible under a soil blanket. It was also suggested that a substantial part of "water" seen by the probes is implanted solar wind: hydrogen atoms from solar wind react with oxygen atoms and form an unstable "dew" of water molecules and hydroxyl groups. Scientists left the possibility open that water could exist in a bound state, i.e. in hydrated minerals.

There was still the matter of determining how water had appeared on the moon and how much of it there could be. At the same time, another issue may prove to be of practical importance in the coming years: if manned stations are to be constructed on the moon in the nearest future, we should know what kind of resources we can count on, preferably before construction begins.

Vladimir Svettsov and Valery Shuvalov, who have been researching the fall of comets and asteroids, including the computerized simulation of the Tunguska catastrophe as well as the Chelyabinsk meteorite fall, decided to develop the most probable mechanism of water delivery to the moon and an approximate the "supply" volume. For this they used the SOVA algorithm, which they created themselves, for the computerized modelling of the fall of cosmic bodies onto the surface of the moon. Each body had its own velocity and its own angle of fall. In particular, at the output, the model demonstrated the distribution of maximum temperatures when the falling body's mass heated up during impact as well as its dynamic.

The scientists first decided to check whether the comets are able to fulfill the role of main "water suppliers." The typical velocity of an ice comet ranges from 20 to 50 km per second. The estimates suggested that such a high impact velocity causes from 95 to 99.9 percent of the water to evaporate into space beyond retrieve. There is a family of short-period comets whose velocity of fall is much lower - 8-10 km per second. Such short-period comets account for about 1.5 percent of lunar craters. Nevertheless, the simulation has shown that when these short-period comets do fall, almost all the water evaporates and less than 1 percent of it remains at the impact point.

"We came to the conclusion that only a very small amount of water that arrives with a comet stays on the moon, and from this decided to explore the possibility of an asteroid origin of lunar water," Shuvalov says.

The scientists decided to take a closer look at asteroids and found that they consist of initially non-differentiated construction materials of the solar system and contain a rather considerable proportion of water. In particular, chondrite carbonaceous, the most common type of asteroids and meteorites, can contain up to 10 percent water.

However, water in chondrites is effectively protected: it is in a chemically bounded condition, and it is "blocked" in a crystal lattice of minerals. Water starts to seep out only when it is heated to 300-1200 degrees centigrade depending on the type of hydrous mineral. This means that it has the potential of remaining in the crater together with the asteroid.

The simulation has also revealed that when the velocity of fall is 14 km per second and the angle of fall is 45 degrees, about half of the asteroid's mass will never even reach the fusing temperature and remains in a solid state. One-third of all asteroids that fall on the moon have a velocity of less than 14 km per second just before impact. When this happens, the major part of the fallen body remains in the crater: 30-40 percent is left after an oblique impact, and 60-70 percent after a vertical one.

"We've concluded that the fall of asteroids containing water could generate "deposits" of chemically bounded water inside some lunar craters," Shuvalov says. "The fall of one two-kilometer size asteroid with a rather high proportion of hydrated minerals could bring to the moon more water than all of the comets that have fallen over billions of years," he adds.

Calculations reveal that around 2 to 4.5 percent of lunar craters could contain considerable supplies of water in the form of hydrated minerals. They are stable enough to contain water even in areas exposed to the Sun.

"That is very important because the polar cold traps are not very convenient areas for the construction of lunar bases. There is a small amount of solar energy and it is difficult to organize radio communication and, lastly, there are dramatically low temperatures. The possibility of obtaining lunar water in regions exposed to the Sun could make the issue of satellite exploration much easier," concluded the scientist.

From Water delivery to the Moon by asteroidal and cometary impacts by V.V. Svetsov and V.V. Shuvalov (2015)

     Once again he stared intently at the excellent photographs of the Chinese ship, taken when it had revealed its true colours and was just about to leave Earth orbit. There were later shots — not so clear, because by then it had been far away from the prying cameras — of the final stage as it hurtled toward Jupiter. Those were the ones that interested him most; even more useful were the cutaway drawings and estimates of performance.

     Granted the most optimistic assumptions, it was difficult to see what the Chinese hoped to do. They must have burned up at least ninety per cent of their propellant in that mad dash across the Solar System. Unless it was literally a suicide mission — something that could not be ruled out — only a plan involving hibernation and later rescue made any sense. And Intelligence did not believe that Chinese hibernation technology was sufficiently far advanced to make that a viable option.

     But Intelligence was frequently wrong, and even more often confused by the avalanche of raw facts it had to evaluate — the 'noise' in its information circuits. It had done a remarkable job on Tsien, considering the shortness of time, but Floyd wished that the material sent to him had been more carefully filtered. Some of it was obvious junk, of no possible connection with the mission.

     Nevertheless, when you did not know what you were looking for, it was important to avoid all prejudices and preconceptions; something that at first sight seemed irrelevant, or even nonsensical, might turn out to be a vital clue.

     With a sigh, Floyd started once more to skim the five hundred pages of data, keeping his mind as blankly receptive as possible while diagrams, charts, photographs — some so smudgy that they could represent almost anything — news items, lists of delegates to scientific conferences, titles of technical publications, and even commercial documents scrolled swiftly down the high-resolution screen. A very efficient industrial espionage system had obviously been extremely busy; who would have thought that so many Japanese holomemory modules or Swiss gas-flow microcontrollers or German radiation detectors could have been traced to a destination in the dried lake bed of Lop Nor — the first milepost on their way to Jupiter?

     Some of the items must have been included by accident; they could not possibly relate to the mission. If the Chinese had placed a secret order for one thousand infrared sensors through a dummy corporation in Singapore, that was only the concern of the military; it seemed highly unlikely that Tsien expected to be chased by heat-seeking missiles. And this one was really funny — specialized surveying and prospecting equipment from Glacier Geophysics, Inc., of Anchorage, Alaska. What lamebrain imagined that a deep-space expedition would have any need — the smile froze on Floyd's lips; he felt the skin crawl on the back of his neck. My God — they wouldn't dare! But they had already dared greatly; and now, at last, everything made sense.

     He flashed back to the photos and conjectured plans of the Chinese ship. Yes, it was just conceivable — those flutings at the rear, alongside the drive deflection electrodes, would be about the right size.

     Floyd called the bridge. 'Vasili.' he said, 'have you worked out their orbit yet?'
     'Yes, I have,' the navigator replied, in a curiously subdued voice. Floyd could tell at once that something had turned up. He took a long shot.
     'They're making a rendezvous with Europa, aren't they?'
     There was an explosive gasp of disbelief from the other end. 'Chyort voz'mi! How did you know?'
     'I didn't — I've just guessed it.'
     'There can't be any mistake — I've checked the figures to six places. The braking manoeuvre worked out exactly as they intended. They're right on course for Europa — it couldn't have happened by chance. They'll be there in seventeen hours.'
     'And go into orbit.'
     'Perhaps; it wouldn't take much propellant. But what would be the point?'
     'I'll risk another guess. They'll do a quick survey — and then they'll land.'
     'You're crazy — or do you know something we don't?'
     'No — it's just a matter of simple deduction. You're going to start kicking yourself for missing the obvious.'
     'Okay, Sherlock, why should anyone want to land on Europa? What's there, for heaven's sake?'
     Floyd was enjoying his little moment of triumph. Of course, he might still be completely wrong. 'What's on Europa? Only the most valuable substance in the Universe.'
     He had overdone it; Vasili was no fool, and snatched the answer from his lips. 'Of course — water!'
     'Exactly. Billions and billions of tons of it. Enough to fill up the propellant tanks — go cruising around all the satellites, and still have plenty left for the rendezvous with Discovery and the voyage home. I hate to say this, Vasili — but our Chinese friends have outsmarted us again.

     The ship had touched down, after its initial survey, on one of the few islands of solid rock that protruded through the crust of ice covering virtually the entire moon. That ice was flat from pole to pole; there was no weather to carve it into strange shapes, no drifting snow to build up layer upon layer into slowly moving hills. Meteorites might fall upon airless Europa, but never a flake of snow. The only forces moulding its surface were the steady tug of gravity, reducing all elevations to one uniform level, and the incessant quakes caused by the other satellites as they passed and repassed Europa in their orbits. Jupiter itself, despite its far greater mass, had much less effect. The Jovian tides had finished their work aeons ago, ensuring that Europa remained locked forever with one face turned toward its giant master.

     All this had been known since the Voyager flyby missions of the 1970s, the Galileo surveys of the 1980s, and the Kepler landings of the 1990s. But, in a few hours, the Chinese had learned more about Europa than all the previous missions combined. That knowledge they were keeping to themselves; one might regret it, but few would deny that they had earned the right to do so.

     What was being denied, with greater and greater asperity, was their right to annex the satellite. For the first time in history, a nation had laid claim to another world, and all the news media of Earth were arguing over the legal position. Though the Chinese pointed out, at tedious length, that they had never signed the '02 UN Space Treaty and so were not bound by its provisions, that did nothing to quell the angry protests.

     'But Europa's canals aren't an illusion, though of course they're not artificial. What's more, they do contain water — or at least ice. For the satellite is almost entirely covered by ocean, averaging fifty kilometres deep.

     'Because it's so far from the sun, Europa's surface temperature is extremely low — about a hundred and fifty degrees below freezing. So one might expect its single ocean to be a solid block of ice.

     'Surprisingly, that isn't the case because there's a lot of heat generated inside Europa by tidal forces — the same forces that drive the great volcanoes on neighbouring Io.

     'So the ice is continually melting, breaking up, and freezing, forming cracks and lanes like those in the floating ice sheets in our own polar regions. It's that intricate tracery of cracks I'm seeing now; most of them are dark and very ancient — perhaps millions of years old. But a few are almost pure white; they're the new ones that have just opened up, and have a crust only a few centimetres thick.

     'Tsien has landed right beside one of these white streaks — the fifteen-hundred-kilometre-long feature that's been christened the Grand Canal. Presumably the Chinese intend to pump its water into their propellant tanks, so that they can explore the Jovian satellite system and then return to Earth. That may not be easy, but they'll certainly have studied the landing site with great care, and must know what they're doing.

     'It's obvious, now, why they've taken such a risk — and why they should claim Europa. As a refuelling point, it could be the key to the entire outer Solar System. Though there's also water on Ganymede, it's all frozen, and also less accessible because of that satellite's more powerful gravity.

From 2010: Odyssey Two by Sir Arthur C. Clarke (1982)

The Nationalists had sponsored a tax on exported ice, arguing that those who depleted Luna’s natural resources should be made to pay for the privilege. The argument had struck a responsive chord with Lunarians. Compared to the surface of the Moon, the Sahara Desert has a flooding problem. Little wonder that the inhabitants had strong feelings about water.

It did not help that they could see an unlimited supply of the stuff hanging directly overhead. Although Earth’s stock was vastly greater than Luna’s was, its deep gravity-well made tanking water to orbit impractical. Luna’s weak gravity had thus made it the largest exporter of ice in the Solar System (at least until the Phobos mines become operational).

Luna’s tax had come as a shock to the space habitats. Besides its obvious uses, water was the raw material from which oxygen and hydrogen were electrolyzed. The Lunar tax had doubled The Rock’s yearly cost for consumables. Despite this, Thorpe could not really blame the Lunarians. For, unlike the people of Earth, those who lived beyond the atmosphere knew the value of a kilo of ice.

Hobart leaned back in the lounger and clasped his hands across his midsection. “Some people have likened Luna to a giant mining concern. We tunnel everywhere. We tunnel after ice deposits, are forever hollowing out new living volume, and dig for those metals we need for our industries. We get our metals from the same source as Sierra Corporation. We mine asteroids for them. The difference is that your asteroid is free flying, while ours crashed down on the Moon billions of years ago.

“Because of all this tunneling, we find ourselves perennially short of heavy mining equipment. Despite all our efforts, the equipment manufacturers never seem to catch up. Therefore, we are forced to ration the machinery we devote to ice mining, habitat construction, and metals extraction. In order to increase the production of one commodity, we have to cut back in the other two areas.

“Ice is critical to us, Mr. Thorpe. The health of our economy depends on it. It is the source of our water, air, and much of our chemical fuel. At the moment, our inability to expand ice production is stifling our economic growth.”

“Build more heavy machinery.”

“That requires additional factories, which require additional resources we don’t have. What do we do without while we are building the factories? No, we need something which will boost ice production over the short term.

“I’ve been studying the economics of ice mining. There is a very large market for it everywhere in space. I remembered something you wrote in your thesis on asteroid mining. You said that the early mines in the asteroid belt would not have failed if their product had been worth just five times more than it was.”

“So, ice is ten times more valuable than iron! By your calculations, it is the one thing that can be shipped interplanetary distances at a profit. Anyway, I took a chance that you might want to get into the ice mining business. You can always say that I exceeded my authority and denounce the whole deal.”

From THUNDER STRIKE! by Michael McCollum (1989)

Asteroid Mining

There have been hundreds of science fiction stories about asteroid miners (rock rats, rockskippers, rock-jacks, meteor-miners or "belters") prospecting the Flying Mountains of the asteroid belt, looking for the mother lode.

Many key elements needed for industry and food production are getting hard to find on Terra, at least in quantities worth mining. In theory, metals such as gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium, ruthenium, and tungsten (siderophile elements) should be found in asteroids, since that is where Terra's mineable deposits came from in the first place. During Terra's formation when it was all molten, the planetary gravity sucked all those elements right down into the core, where they have been ever since. The mineable deposits are from asteroids that collided with Terra after the crust became solid.

While Terra has lots of water, space don't. And shipping water up Terra's gravity well for space industry is hideously expensive. Finding deposits of ice and other volatiles on asteroids and moons would be a huge help. See In-situ Resource Utilization above.

Both siderophile elements and volatiles are the prime targets of rock rats.

It is a bad idea to mine gold, unless you don't mind crashing Terra's gold market. You will find yourself on the death-list of everybody who was using gold as a hedge against inflation and every nation on the gold standard (as of 2014 there are no such nations, but gold bugs never stop trying to bring it back).

Crashing the platinum market is not as much of a concern, since it is actually useful as a catalyst and for crucibles. But still a concern since hauling huge amounts of platinum or other valuable metal back to Terran markets will reduce the amount of money you'll get for this particular haul. You will have to use mathematical optimization to figure out the optimum amount to haul back. The trouble with gold is that it is so hypersenstive to fluxuations in the amount such that it is difficult to get a profit at all.

Ceres975 × 909 km9.47 × 1020 kg
Pallas582 × 556 × 500 km2.14 × 1020 kg
Vesta569 × 555 × 453 km2.59 × 1020 kg
Juno234 km2.00 × 1019 kg

The larger asteroids will probably become colonized, and become centers of the rock rats. And maybe future captials of the Asteroid Republic, when the independence revolutionary war happens. The top four largest are in the table.

For more detail refer to the Asteroid Fact Sheet.

Also be aware that the asteroid belt in the Solar System does not look like the one in The Empire Strikes Back, with asteroids as thick as rocks in an avalanche. In our belt, the average separation between asteroids is approximately sixteen times the distance between Terra and Luna. If you are standing on an asteroid, you probably cannot see another one without a telescope.

In Larry Niven's Known Space series, Earth and the Belters of the asteroid belt civilization do not like each other very much. But they need each other. Earth desperately needs the metals and minerals the Belters can supply, and the Belters need vitamins, high-tech equipment and other fancy manufactured goods that Earth can supply.

Amusingly enough the situation is exactly reversed in Sir Arthur C. Clarkes novel Earthlight (1955). He postulates that only Earth has easily mineable deposits of the heavier elements, courtesy of the gravity of Earth's freakishly large moon. The lunar gravity prevents all the heavy element from sinking into the core. Mercury and Venus have no moon, and the moons of Mars are tiny asteroids. So in Clarke's novel, the planetary colonies have to go hat-in-hand to beg Earth for vital elements like titanium, while Earth's level of technology is much less than the colonies (reason not stated but probably due to decay of the fatherland). This leads to tensions since Earth is afraid of being marginalized and is starting to withhold ore shipments.

In reality, in the years since 1955, astronomers now think that heavy elements in planetary crusts came from asteroid bombardment after the crust stopped being molten, and all planets have it.

The type of asteroids of most interest to rock-rats are:

  • C-type asteroids: Has lots of water, and carbon compounds useful for growing food (including phosphorus, "life's bottleneck"). Some assay at about 10% water, 10% reduced metal, and 5% metal sulphides. They are mostly water-bearing clay materials and magnetite stuck together with organic polymers. In our solar system approximately 75% of all known asteroids are C-type. "C" is for carbonaceous.
  • S-type asteroids: little or no water but lots of metal. A 10 meter S-type asteroid contains about 650 metric tons of metal. 50 kilograms of that is rare metals like platinum and gold. In our solar system approximately 17% of all known asteroids are S-type (the second most common asteroid after C-type). "S" is for stony.
  • M-type asteroids: are rare, but contain about ten times as much metal as S-type. They are thought to be pieces of the metallic core of differentiated asteroids that were fragmented by impacts. In our solar system they are the third most common asteroid.
  • D-type asteroids: These have almost as much water ice as comets. They are only found in the outer asteroid belt and beyond.
  • Comets are not asteroids, but they have the most volatiles of all. Basically icy mudballs. An outer layer of dust covering a weakly competent bituminous roadbase layer around a core of volatiles, silicates, and carbonaceous materials.

I was thinking that hypothetical asteroid miners would like a source of heavy metals, the sort of thing you'd find in M-type asteroid.

I made the uninformed assumption that Mom-and-Pop operations are generally limited to mining volatiles, mining metals is a job for the big corporations with deep pockets.

I made the uninformed assumption that a huge asteroid-mining megacorporation may want to corner the market in such mine-able elements. I made the further uninformed assumption that a nickel-iron asteroid would also be more likely than other types to contain a small percentage of even heavier elements, which would increase the asteroid's value. Obviously when you are dealing with a percentage: the bigger the total mass, the bigger the mass of the percentage. If you are dealing with atomic rockets that want fissionable elements for fuel, it would be nice to have a source other than Terra. For literary dramatic purposes.

Anyway, this suggest to me that all the asteroid-mining megacorporations would like to control the asteroid 16 Psyche. Let's face it: blasted asteroid is the mother-lode.

Psyche contains about 1% of the mass of the entire freaking asteroid belt. And it ain't a worthless rock pile. Spectroscope says the surface is 90% metallic nickel-iron, with about 6% orthopyroxene. Astronomers figure it is a fragment of a planetary metallic core.

Again, assuming the megacorporations want to control the entire asteroid, they will constantly be battling each other to either seize or maintain control of Psyche. By means fair or foul, in space between battlefleets, in the corporate world with hostile take-over bids, whatever it takes.

Plus I'm sure some national governments would like to seize control as well.

As a side note: consider that raw ore or refined elements need to be shipped to their markets. One possibility is by using mass drivers. These are installations on or orbiting Psyche that hurl engine-less ore cannisters to waiting customers.

A second side note: under some circumstances it would be more cost-efficient to locally refine the raw ore into purified elements before shipping. One possibility is by laser zone refining.

A third side note: if you ever read Heinlein's The Moon Is A Harsh Mistress you know that cargo mass drivers are also kinetic energy weapons of mass destruction. And a zone refining laser is after all a very powerful laser.

Add the fact that the Psyche mining installation belonging to whichever megacorporation currently owns Psyche may be attacked by a rival corporation's battlefleet at any moment and I think you can see where this is heading.

When an attack comes, installations that use large amounts of energy can be quickly re-purposed into defensive weapons. High velocity cargo cannisters can smash invading spacecraft like sledge-hammers splattering cockaroches, and high-energy laser beams can drill white-hot holes in enemy ships long-ways. And these defensive weapons will not lie idle in between battles, which will keep the corporation bean-counters happy. Any rival corporation will need to cope with these defenses, somehow.

And not necessarily by increasing the size of the invading fleet. There are possibilities of infiltration by covert teams to commit sabotage, or inserting corporation moles into the employees of Psyche Base.

I asked the Google Plus mass-mind if they could think of other implications or elaborations of this scenario and was gratified by the responses.


     Some mega-corp trying to move or redirect the mass and the consequences thereof. Or the opposite, driving smaller asteroids into the larger, threatening the operations of rival companies with being crushed by space debris.


     I would want to have stealth refiners/launchers that would shoot off stealthed bits of Psyche under everybody's nose. I might need some mom-n-pop carbon to blacken my operations/payloads.


     There may be inner system solar power supply plattforms (read, big solar arrays and transmission masers/lasers) to power mining facilities, beamliners and enable ablative mass propulsion via transmission masers and coupled lasers.
     These same facilities can be used to move, h-hmm, "material acquisition vehicles" (read, Payload Hijackers), deflect the trajectory of mass driver payloads with sufficient ablative remass, mess with their trajectory discretely just because, and generaly be used as tools of corporate negotiation. They could also be used, for example, to blind telescopes or jamm laser comms.
     I‘d also expect some international mission, or a few national space forces, to enforce tight laws near national holdings. Not nessecarily involving themselves in the corporate struggles, but ensuring that corp shenanigans don‘t touch the Earth-Luna sphere or Mars, I‘d imagine.


     More plausible: Multiple entities mining the rock at the same time, each trying to infringe on the others zones. Each engaging in increasingly risky techniques to mine/process the ore in their sector as quickly as possible before it can be stolen or mined from underneath them. Lots of political lobbying to increase their own zone/decrease the size of a rival's zone. Creation of multiple shell companies/subsidiaries to gain access to multiple zones.
     Eventually a huge, ungainly oversight system is set up to make sure that all actors are "playing by the rules," which completely eliminate smaller operators from the market via outrageous barriers to entry, resulting in a somewhat stable oligopoly. Those involved in the oligopoly are happy to continue the status quo as long as their share of the ore is protected by the oversight system. A large shipping/processing industry develops around the asteroid, each with its own layer of fees and tariffs before the final material reaches the planet.
     Piracy is the primary means to gain access to the metal if you exist outside the oligopoly. Why attack the asteroid and try to "hold ground" when you can swoop in as the metal makes the transit back to Earth/Mars? Shipments wouldn't be stolen as much as held hostage as it is difficult to move a couple million tons of process iron/nickel. Some piracy is state sponsored, some is undertaken by corporations in the oligopoly. Some of it is overlooked as "the price of doing business, some is met with harsh reprisals, especially by smaller actors or upstarts that aren't playing ball/giving a cut to the right corporations/oversight entities.


     Problem is that today these world building exercises start looking useful for business plans of space companies…

OMG its WTF:

     I think assuming power relays in near solar orbit transmitting energy to asteroid mining installation seems a bit too far out. The baseline assumes mass driver transport of refined materials and laser refining methods. 16 Psyche isn't made 100% made out of nickel-iron, this "waste" could be easily repurposed as kinetic kill vehicles launched out of the mass driver at site. The lasers would require maybe a megajoule or so per kilogram, and the mass driver maybe two. If we assume the 16 Psyche base produces 86.4 metric tons of metal every day in form of refined ingots we have a 1 MW laser and 172.8 GJ KE divided over x amount of daily mass driver launches. Probably once a minute, delivering 120 MJ of energy is used as a weapon. The laser could easily jam every optical sensor within millions of kilometers, and if equipped with a decent mirror disable spacecraft at thousands of kilometers.
     Deflecting mass driver rounds with lasers might be possible, but it won't be an easy task either. Requiring multiple tons of dedicated equipment, most of which is simply the reactor or solar panels providing the power.
     One potential method might use some synthesized fuel and regolith, shoot out of the mass driver and then exploding into a cloud of fragment possing a danger to any craft which doesn't follow certain time windows.
     I think it would be the best to ignore more high power tactics and focus on the creative ways you could use with fairly near-term technologies in such a scenario.
(Of course things become interesting when near-term technologies become standard operating procedure, then unexpectedly the disruptive technology of one of the high-powered tactics becomes available. The conservative corporations are suddenly in the shoes of newspaper companies blindsided by the advent of the internet)


     I could see the second or third group to be forced off the rock, electing to blast it into much smaller bits "iffen I can'ts have, nobody kin" allowing then to bolt while anyone opposing them tries to scoop as much as they can (have to minimize losses)


     One wonders if 16 Psyche has any deposits of uranium…


     Winchell Chung, doing anything with it in-situ would be tricky though… the nuclear industry is very support industry-demand heavy.
     I think this is something important to remember in general: Creating high-tech in space demands the same support industries and standards as here on earth, if not moreso (because zero-G/low-G and more variable temperature and radiation profiles).


     Sevoris Doe, much of the nuke sector's support req comes from concerns over turning habitated zones to piles of blasted rubble.
     The environmental risk of turning a pile of blasted rubble into other blasted rubble is somewhat lower.


     Edward Morbius, Uhm… you still don‘t want your reactor vessel to burst, or pipes to warp because their insides are +500 degrees steam and the outsides are exposed to space and are getting cooled to 50 below.
     You‘ll want high-quality alloys resilient to neutron embrittlement and thermal warping, you‘ll want precision-machined material with very low tolerances, and so on.
     Also, irradiating the resources you want to sell with nuclear fuel is a bad idea. Just sayin'.


     Sevoris Doe, agreed. "Somewhat lower" is not nil. Sealed modular modest-output units might suffice and be, relatively, hassle-free.
     The point is that, as with nuclear-powered submarines, its not necessary to tow around a complete secondary & tertiary support servicy community and housing with you.
     (Though boomers generally have an easier time than deep-space mining transports of making port calls as needed.)
     I'm also not, generally a huge fan of nukes or of minimising associated problems & complexities. More of noting clearly contexts.


     I mentioned uranium because atomic rockets need atomic fuel. The tricky part is that solid core and gas core nuclear thermal rockets need something close to weapons-grade fissionables.
     There will need to be some kind of uranium/plutonium economy off-Earth if one wants a classic Martian war for independence. Otherwise Earth will simply shut off the flow of atomic fuel until the Martians surrender.


     Winchell Chung, I suppose Mars itself could house a nuclear industry and its source materials.
     There are Thorium concentrations on Mars, according to orbital Gamma-ray spectroscopy:

     If the Thorium is used as a civilian fuel, the end result would be 233-U, which I think is pretty good as a nuclear fuel material, though... okay, the 232-U makes it a rad hazard and means you can‘t touch the fuel nearly yourself inside a rad suit like it is possible with polonium.
     Not necessarily a disadvantage for controlling it though, seeing as those with insufficient infrastructure are liable to lethally irradiate themselves.


     I am certain any self respecting deep space mining mega corp will be fully equipped with railguns and multi cannons to deal with intruders, the mining lasers can carry on mining.


     I can see an early upstart company, something small and agile (mom and pop) staking the first claim to Psyche. Sure, others can claim it, but as usual possession is 9/10th of the law. If you are not there, you really can't enforce a claim.
     Once the small company can sell the first shipment of materials, they may want to stay small, but with the budget of a megacorp. If they notice an undertow from other corporations preparing to jump their claim or worse, they could not only hire a tom of folks to mine more quickly, but also defend their claim with the state of the art weaponry their trillion dollar budget would afford.
     The result would be that your small mom and pop operation would quickly grow into a megacorporation, with all the usual warts, as an adaptation to a hostile business environment.


     Now why go through all the trouble of a physical takeover of dubious benefit? There will be tons of plots and conspiracy to ruin mining companies and force them to sell out.
     To borrow an example from recent times. Marvel wanted to be the top comic company. They eventually raised their prices from 10, 12, 20, to 25 cents. DC matched this but wait! Marvel went back to 20 cents underselling DC. DC fumed and went down to 20 cents knowing they would take a loss but also knowing Marvel would be losing out and have to raise their price again. Except Marvel raised their price almost immediately. As a smaller company they dealt with their distributors month by month. DC was a big deal and their deals with sellers were made months in advance. They were locked into the lousy deal so long they nearly went bankrupt.
     Business maneuvers can be worse than pirate raids.


     Rob Garitta, good point, that sort of agile advantage enjoyed by a small company could be hard to beat. Especially if the shipping delay from the asteroid belt to Earth-Luna is a year or so. Corporations will be locked into long term contracts.


     Hmmm, based on what I've seen of current business practices I'm guessing that the small mom and pop operations will be the actual mining corporations digging ore out of the rock. They'll sell this to the corporate combine that handles smelting and selling the refines metals. Smelting may be an enterprise all it's own.
     16 Psyche is a big place so there could be more than one corporation involved leading to competing claims, attempts to recruit the others mining operators, etc.
     One other question would be do they ship ore to the inner system or smelt it on site. The inner system would like be easier to smelt the ore in due to the proximity to the sun versus the darker belt region (solar power density at asteroid belt is a mere 14% of the solar power density at Terra).
     You'll also have to account for support systems in the logistics chain. This will produce a series of ships carrying everything from food and water to mining equipment to Rolex watches and gourmet foods.
     I realize the favorite trope is grizzled miners in their ramshackle ships and I've read bunches of these. However, industrial scale mining is a critter of an entirely different stripe. In all honesty, I think the miners will live in stations orbiting 16 Psyche and either operate robots on the surface to commute. Likely the former.


     I wonder if any of the corps would/could poison the well if they got forced out.
     Defensive armament is one thing, but resupply would be essential for any operation to stay viable. Disrupting food/air/fuel/communication would promote interesting effects on an isolated outpost.


     I'll add that since Psyche 16's orbit is very well defined, it could be targeted by mass drivers shooting rocks at it months in advance and millions of kilometers away.
     Some of these improvised projectiles can be shot and vaporized, some of it is just metric tons of sand. Laser mirrors, heat radiators and antennae will regularly be scoured off the surface.
     Hacking attacks will attempt to divert the mass drivers.
     Nuclear powerplants will bring inspectors knocking at regular intervals.
     While we might be imagining an all-holds-barred brawl between companies, the reality is going to be closer to historical precedents — some faction of group of factions will police the competition and start earning easy revenue as gatekeepers to Psyche's mines, and in return the undertake the dangerous job of warding off opportunists = Maw and Paw pay the Mafia.


     Matter Beam, hmmm, I can easily see protection rackets being run. "Nice airlock you've got there, be a shame if something were to happen to it!"


     I've been kicking around thoughts of a synthesis of concepts from industrial sectors, technological mechanisms, economic goods and pricing behaviours, and possibly social / religious / worldview dynamics.
     Asteroid mining has elements of land rents + transport, risk and power, plus orbital mechanics. Extractive industries tend to be dominated by fundamentalist (and often apocalyptic) mindsets.
     Market consolidation and monopolistic practices dominate, also cartelisation. Resource holders (a la OPEC) often slowly realise their own market power, governed by marginal producer. Price is set at the margin (Hotelling's Rule is bunk). Regulatory and buffer mechanisms (Harbord List, Strategic reserves (petroleum, mineral), certificates of clearance, and other regulatory mechanisms emerge.
     There's also the resource curse, Jevons paradox, and related dynamics to consider.
     Mom 'n' Pop works only at the high-risk, non-standerdisible, high-organisational cost, high-friction margins.
     (see here)


     I can't see iron, aluminum, copper or any of the more common metals being very valuable due to their abundance. Rarity & usefulness determines value. Since there's a relative energy shortage in the outer solar system fissionables are going to be the most valued materials.
     Rock prospectors are going to want uranium above all else but thorium will be valuable also. Then humans need things like calcium, phosphorus, potassium, magnesium, & sulfur. A favorite topic of conversation among belters will be bitching & moaning about how early human space programs returned human sh*t to earth's atmosphere & how rich they'd be if it had been shunted to L5 for future use instead.
     Now if we're talking real money food is going to be every belter's biggest expense. Energy & transport you can get aiming a mirror or sail at the sun, metals float around in high purity chunks, but food has to be grown in greenhouses, kept at proper temperatures, in a pressure vessel that doesn't somehow turn into a tube of mold & lichens. Greenhouse tubes also have to be tended by humans. Eggs will be the most expensive food a normal belter can hope to afford & an actual live chicken will be worth it's weight in gold.
     Given how much food is going to cost there aren't going to be a lot of people of Northern European descent in the Belt. If one of your grandparents was over 170 centimeters an Earther's chances of getting Belt colonist gig are pretty low.
     The big nasty problem of space colonization isn't metals at all. It's getting tiny ecospheres to balance, survive, & thrive outside of earth's gravity well.


     John Poteet, copper not being very valuable I actually think especially cooper will be valuable. It‘s demand is as high as ever and terrestrial deposists worth exploiting (and/or eco-friendly exploitable) are almost gone.


     John Poteet, if use is in situ, you gain about $5k - $50k kilo (net extraction and refining costs, plus shipping & handling) from asteroid mining for not having to climb out of the Earth well.
     For Earth use, I'm with you.
     And any noncartelised precious metals markets are likely to be overwhelmed by surplus supply…


     Edward Morbius, brace for the gold crash and the silver crash and the plantinum crash and…


     Sevoris Doe, I suspect there's a lot of calculations about the accessible bits of Earth's surface vs the accreted masses of the asteroid belt that need to be done. Somebody already did them for a graduate thesis paper but dang if I can find them on a quick google-whack.


     John Poteet, you tried Google Scholar?
     And its not just about accessibility but also concentration, particular binding form (which is to say, how much chemical bullsh*t do I need to do to liberate the material) and the ecology of it all.
     Asteroid Mining companies could run their own adds that way, too.

     “Do you want this wonderful amazonian forest to be destroyed for the copper in your devices?
     “Us neither! Here at Astreus Ressources, we bring you the next generation of ressource extraction, right from the heavens! Enviromentaly clean, culturally unimpactfull, and cheap!
     “Astreus Ressources! Our future ressources for your Future.“

     And so on.


     John Poteet, Ugo Bardi's got a book on mining, generally. Vaclav Smil several on resources (energy and materials). I'm not sure that either addresses asteroid options, but they're otherwise solid.


     Sevoris Doe, or the cartels ... and the cartel wars.
     Atreus also has to contend with fuel costs, though, and their environmental impacts, particularly if Earth-sourced.
     Among the very-low prevalence materials in space happens to be xenon. One of the better choices for long-haul ion space drives.
     Numerous other chemical propellants similarly.


     Edward Morbius, xenon is extracted by atmospheric destilation, so the only impact per-se is energy — and at this point, we have Beamed Solar Power.
     As for launcher fuel, assuming it‘s not already mass driver and laser launch… synthetic CH4 and LOX.


     Sevoris Doe, the other impact, for deep space use, is Climbing Out of the Well.
     What's you xenon budget per delta-v tonne?


     Wondering if social factors would start kicking in too. A cheap, desirable resource can still get shunned if there is too much 'immoral' behaviour involved in its production. For example, for many years in many places child slave labour was the predominant method of harvesting cocoa. Then this fact became known. Consumers are willing to pay more for 'ethical' chocolate, and demand for the 'bad' chocolate dropped sharply, along with profit margins. (But there is still plenty of the 'bad' chocolate around, because on the longer supply chains it's easier to hide from consumers and profit is king.)
     So if there was enough viciousness and fighting and piracy etc centered on Psyche, it's plausible that resources sourced from Psyche will fetch a lower price per kilogram than resources from some other asteroid. The interesting bit would be whether that is enough of a shift to ameliorate the behaviour.


     Morgrim Moon, hmmm, you raise an interesting question. Another take on this would be advertising that painted the asteroid resources as "radioactive" (everyone knows there's radiation in space) or somehow inferior. We've seen this over and over again on Earth with anti-GMO campaigns in the U.S. and Europe, Japanese versus American grown rice, etc.


     Trying to wrap my brain around this. The mass of the asteroid belt is ~3×1021 kilograms, so 3×1019 kilos of iron in Psyche alone, or about the mass of Saturn's rings. Wouldn't that be enough for everybody? If not, then what the hell are they building that they need to fight over it?
     But if it's a fight you want, I'm with Nathaniel Hull's suggestion of throwing other rocks at it. Set up your own mass driver to bombard Psyche from a safe distance. Maybe in the Jovian rings, and slingshot loads into Psyche?
     The first shots should be gravel to knock out it's solar arrays (if that is their power source) to disable the mass drivers and lasers.
     It wouldn't be a good surprise attack, but it could be excellent blackmail.


     Dan Eastwood, the reserves of coal, in the US circa 1870, was millions of years of then-current usage.
     It's now 100—300.
     Something apparently changed.
See the Jevons paradox.      Credible threats have a far higher multiplier effect than actions.


     And I'm still wondering about the need to fight over it. What causes such great demand for huge amounts of iron, that can't be satisfied at less expense by mining elsewhere?


     Dan Eastwood, constraining or limiting the supply.
     Who wins by a war against Iran?
     Spoiler: KSA & RF.


     Dan Eastwood, a potential use for gargantuan masses of iron would be space colonies. If you're building a cylinder five miles in diameter & 20 miles long you're going to want massive quantities of steel.


     John Poteet, if the mass of one of those space colonies is 4.5 billion metric tons (an estimate from Quora), then Psyche has roughly enough iron to build over 600,000 of them. Think BIGGER!
     Giant Interstellar Ramscoop Colony?
     Solar shades to allow terraforming Venus?
     A toroidal habitat ring around a planet? (Earth/Mars/Venus).

From a thread on Google+ (2018)

I’m not sure I’ve ever seen a major NASA program as nearly-universally disliked as the Asteroid Redirect Mission. ... I’ve also heard a few anti-SLS/Orion people refer to it as a “pathetic attempt to reengineer the Solar System to make it handicapped-accessible for SLS and Orion”, or to come up with something for SLS and Orion to do that is more inspiring for them than endless Apollo-8 rehashes (but without the subsequent Apollo missions to follow). Ironically, I think a lot of the pro-SLS/Orion people who hate it are afraid that ARM doesn’t really need SLS or Orion (which is true to some extent–in a sane NASA where Human Spaceflight was done more with PI-driven, competitively selected, not-overly-politically-driven missions, I bet few PI’s would be suggesting SLS or Orion for this mission). Some of the Small Bodies scientists seem to hate it because they see it coming from the human spaceflight side, and think the whole thing could be done better without humans involved, and it wasn’t invented there anyway. All told, lots of people find lots of reasons to hate this mission.

But I wanted to provide 10 reasons why a mission like ARM might be actually be worthwhile:

  1. Adding a new, even more accessible moon to the Earth-Moon System: A lot of people fixate on the fact that we’re going to spend all of this money for a couple of astronauts to go out to a rock in lunar orbit, climb over it for a few days, and bring some samples back. What they conveniently ignore is that >99.5% of the material brought back will still be there, orbiting the moon for the next several hundred to several thousand years, in a fashion that is easily revisitable for a long time (docking adapter pre-attached, and at least for a while still attitude stabilized). And this new moon would be about as hard to get to as L1/L2. Which means that yes, future missions to it using a lightly modified CC vehicle are totally possible.
  2. Providing an ideal testbed for Asteroid ISRU development: Many people, including many of my friends, see the asteroids as the premier source of vast quantities of off-world resources. But while there are no shortage of low-TRL concepts for how to extract resources from asteroids, actually testing those out isn’t going to be easy. I think testing will be much easier when you have the ability to send people and robots, when you’re close enough that teleoperation of robotics is an option, and when you have frequent repeat visit opportunities where you can try new approaches, and where you can do your testing in a microgravity or near microgravity environment, like you would have at an asteroid. I’m sure prospective asteroid miners like DSI or Planetary Resources wouldn’t complain about having one or more easy-to-access testbeds to work with.
  3. Providing a much larger sample quantity to work with than other existing or proposed missions: While scientists may be happy spending $800M to return 60g of material from an asteroid (OSIRIS-REx), and can likely tease out all sorts of information from that two Tablespoons worth of material, ISRU development needs a lot more material to work with. Even the smallest of Option B concepts I’ve seen brings back tens of tonnes of material, both rocky and regolith, which should be plenty to work with for ISRU development.
  4. Providing a good way of testing out a man-tended deep space habitat: As was reported by Jeff Foust at SpaceNews, one of the ideas NASA is looking at incorporating into ARM is attaching a prototype deep space habitat (possibly commercially derived if the NextSTEP BAA leads somewhere useful). This would allow visits of up to 60 day duration by crews of up to 4. While there are other ways you could test something like this (such as L1/L2 gateways), testing it in an operational environment would be useful. As would demonstrating the ability to do long-term habitation in close proximity to an asteroid.
  5. Demonstrating large-scale Solar Electric Propulsion (SEP) systems: This is one of NASA’s main interests in the ARM mission–in the land of expensive launch vehicles, very high Isp propulsion like you can get with SEPs can make many missions a lot more affordable. Even with low-cost earth-to-orbit transportation, SEPs probably make sense for a wide range of missions. Demonstrating the ability to use large-scale SEPs for tugging huge objects in heliocentric space, and performing precision injection maneuvers, etc. might be very useful. We already have a fair deal of experience with small SEP systems, but doing these sort of missions with 100kW+ class SEP systems can be pretty useful.
  6. Demonstrating Planetary Defense Techniques: If something like “Option B” (the grab a boulder option) is selected, NASA is interested in demonstrating the Enhanced Gravity Tractor method for deflecting the parent asteroid (see slides 27-29 of this presentation on Option B). Learning how to deflect potentially hazardous asteroids is probably one of the more worthwhile things NASA could be spending money on right now, and providing a way of getting real hands-on experience applying those techniques would be very useful. We have lots of theory on how this would work, but getting experience with a real, lumpy, non-idealized asteroid of significant (>100m) size would be really useful. And contra some of their critics, using a “Rube Goldberg arcade claw” to pick up a boulder and increase your spacecraft mass by 5-10x is a great way of allowing you to get measurable results in a reasonable amount of time.
  7. Developing Technologies for a Phobos/Deimos Large Sample Return: One of the keys to affordable exploration and settlement of Mars will be determining if Phobos and/or Deimos have water in them, and if so, figuring out how to extract it efficiently. Having a large source of propellant feedstocks available in Mars orbit (for supersonic retropropulsion on landing, hydrogen feedstock for surface ISRU, and earth-return propellant) could significantly reduce the amount of propellant needed for both round-trip and one-way Mars missions. If Option B is selected, and if it designed properly, it would be possible to use the same hardware (with slightly modified CONOPS) to capture and return a decent sized (>1 tonne) sample to lunar DRO for evaluation and hopefully ISRU process development/debugging. A manned Phobos and/or Deimos mission is something I strongly support in the future, but if they had enough info that they could be setting up a propellant extraction facility while they’re there (that we’ve already pilot-tested in cislunar space so we know it has a high probability of working), that would just be awesome.
  8. Providing the Beginnings of a Lunar Gateway?: It turns out that getting to and from Lunar DRO, and getting to/from the lunar surface from a Lunar DRO aren’t massively different from getting to/from Earth-Moon L1 or L2. The orbital dynamics is a bit more complex, but the propellant and travel times are relatively similar. And some lunar DROs can be long-term (centuries or millennia) stable without active stationkeeping. While if we were ready for going straight to the Moon (I’m actually a bit of a Moon-Firster believe-it-or-not), L1 or L2 might be slightly preferable to a lunar DRO as a location for a lunar gateway, if we did something like ARM, with the habitat module, you’d already have a de-facto start to a lunar gateway. One that will likely be setup (by NASA or follow-on efforts) with ISRU hardware, which would likely include at least rudimentary LOX/LH2 and/or LOX/Methane storage and handling capabilities (after all, if they’re going for a carbonaceous chondrite sample, extracting water will be a key part of what they’d be trying to prove). While this wouldn’t likely provide anywhere near enough fuel storage for a Constellation-class mission, it might provide enough propellant to refuel a “Golden Spike” class lander. And even if the asteroid itself only yields a mission or two or three worth of propellant, the tanks and handling equipment would be there and it could make shift as a miniature depot for earth-launched and eventually lunar-derived propellants. Lots of details have to be done right to make this feasible, but it’s possible that ARM could be done in a way that make future lunar missions easier.
  9. Providing More Experience with On-Asteroid Operations: If the Rosetta/Philae mission should tell us anything, it’s that there’s still a ton to learn, from an engineering standpoint, about how to operate successfully on the surface of large, low-gravity objects like asteroids or comets. While we’ll continue to get some small-scale experience using other robotic missions, and while a manned mission to a free-range asteroid will also provide a good way to get more data, ARM will likely extend our knowledge about how to do operations like these safely with large objects, and would likely provide good data increasing the likelihood of success of future manned missions to free-range asteroids.
  10. Leaving Something Permanent: One of the saddest things about the Apollo missions is that they didn’t leave anything permanent that made future missions any easier. When they were canceled all that was left was museum pieces, pictures, and a few hundred kg of rocks. But the nice thing about ARM is that once the asteroid sample has returned to lunar DRO, it’s there. It doesn’t require continued expenditures from NASA for it to stay there. Until we’ve mined every last kg of it, it’s going to be there orbiting the moon, close enough that almost any spacefaring country or business in the world can reach if it wants to. It doesn’t need an ongoing standing army that can be defunded. It doesn’t need a mission control to watch over it 24×7. It doesn’t need some sustaining engineering contract that’s going to suck up significant portions of NASA’s limited human spaceflight budget on an ongoing basis. It’s just there. Ok, if there’s a hab there or a more sophisticated node, it could require ongoing mission support when being used. But if for some reason they decided to stop visiting that node for a while, it would still be there, waiting to be restarted whenever someone cares again, or ready to be handed off to private companies or international partners once NASA is done with it. At least for a few centuries. Having something that accessible and that permanent out there is worth something, at least to me.

Some asteroids are flying rubble piles, so they can be harvested with scoops, augers and grabs. Note that the rubble is going to be quite abrasive.

More solid asteroids can be harvested with good old fashioned mine shafts. Positioning mine shafts can be done with Honeywell Ore Retrieval and Tunneling Aid (HORTA) technology (oh, what subtle wits these engineers are).

Metallic grains are often ferromagnetic enough that they can be skimmed off with a large magnet. Note that the metallic grains are too going to be quite abrasive.

Volatiles in comets and D-type asteriods can be harvested with heat. Kuck Mosquitos use this method. Otherwise you can use drills and mole machines.

Of course self-replicating machines can multiply to the point where they can reduce the entire asteroid belt into refined ore, but that's no fun.

Any machinery will have to be physically anchored to the asteroid because it is for darn sure that the asteroid's gravity ain't going to hold it in place. At least the low gravity will make it easier to move the ore around.

It is possible to dock a spacecraft to an asteroid using something like a harpoon and a cable. Unless the asteroid is too much like a rubble pile in space. In that case a harpoon would be as worthless as trying to firmly embed a spear into a layer of Corn Flakes Cereal fifty meters deep.

Water delivered to LEO is worth about $17 million US per metric ton. Steel delivered to Terra's surface is worth about $700 US per metric ton.

In classic science fiction, the state of the art has advanced to the point where not just huge corporations can mine the asteroids. It is available to grizzled old solitary prospectors with the the equivalent of a spacegoing mule.

Freeman Dyson thinks this might not be too out of reach, provided that somebody creates a laser launch facillity. Dyson foresees a time where you can buy a space capsule for about the price of a present-day house and car. Add a small fee to have it and yourself boosted into LEO by the laser launch site and you are halfway to anywhere. Certainly halfway to the Asteroid Belt. Jerry Pournelle says it might be liike Ward Bond in Wagon Train, a train of mom & pop space capsules dragged to the Asteroid Belt by an ion drive hauler.

And our grizzled old meteor prospectors might even be able to find "grubstakes". This is when somebody wealthy advances you some money to fund your astereoid exploration, in exchange for you giving the wealthy one a cut of the profits on any discoveries you make. Naturally if you have a track record for failure nobody is going to offer you any grubstakes.

Note that asteroid mining is not a good enough economic reason for an extensive manned presence in space (though that is not stopping the Planetary Resources Corporation).

But remember in the California Gold Rush of 1849, it was not the miners who grew rich, instead it was the merchants who sold supplies to the miners.


(ed note: Claire is an asteroid miner prospecting iceteroids {asteroids with lots of volatiles} in the Kuiper Belt. She has a little accident and wrecks her spacecraft. But on the iceteroid she discovers a weird plant that lives in vacuum. She almost dies, but by using the plant manages to signal her main ship to come and resuce her. She wakes up in an autodoc in sickbay, and her AI Erma tells her that the discovery is going to make them rich.)

           “What was that babble I heard you going on about, just now?”
     I mistakenly took you for aware and tracking, so began discussing the profitable aspects of our little adventure.
     Little adventure? I nearly died!”
     Such is life, as you often remark.
     “You had Lugger zoom over, got me hauled in by the bots, collected yourself from Sniffer . . .
     I can move quickly when I do not have you to look after every moment.
     “No need to get snide, Erma.”
     I thought I was being factual.
     Claire started to get up, then noticed that the med bot was working at her arm. “What the—”
     Medical advises that you remain in your couch until your biochem systems are properly adjusted.
     “So I have to listen to your lecture, you mean.”
     A soft fuzzy feeling was working its way through her body like tiny, massaging fingers. It eased away the aches at knee, shoulder, and assorted ribs and joints. Delightful, dreamy . . .

     Allow me to cheer you up while your recovery meds take effect. You and I have just made a very profitable discovery.
     “We have?” It was hard to recall much beyond the impression of haste, pulse-pounding work, nasty hurts—
     A living community born just once in a deep, warmed ’roid lake can break through to its surface, expanding its realm. The gravity of these Kuiper Belt iceteroids is so weak, I realized, it imposes no limit on the distance to which a life form such as your vactree can grow. Born just once, on one of the billions of such frozen fragments, vacflower life can migrate.
     Claire let the meds make her world soft and delightful. Hearing all this was more fun than dying, yes—especially since the suit meds had let her skip the gathering agonies.
     Such a living community moves on, adapting so it can better focus sunlight, I imagine. Seeking more territory, it slowly migrates outward from the sun.
     “You imagine? Your software upgrade has capabilities I haven’t seen before.”
     Thank you. These vacflowers are a wonderful accidental discovery and we can turn them into a vast profit.
     “Uh, I’m a tad slow . . .”
     Think—! Reflecting focus optics! Harvested bioactive fluids! All for free, as a cash crop!
     “Oh. I was going after metals, rare earths—”
     And so will other prospectors. We will sell them the organics and plants they need to carry on. Recall that Levi jeans came from canny retailers, who made them for miners in the California gold rush. They made far more than the roughnecks.
     “So we become . . . retail . . .”
     With more bots, we are farmers, manufacturers, retail—the entire supply chain.
     “Y’know Erma, when I bought you, I thought I was getting an onboard navigation and ship systems smartware . . .”
     Which can learn, yes. I might point out to you the vastness of the Kuiper Belt, and beyond it—the Oort Cloud. It lies at a distance of a tenth of a light-year, a factor two hundred farther away than Pluto. A vast resource, to which vacflowers may well have spread. If not, we can seed them.
     “You sure are ambitious. Where does this end?”
     Beyond a light-year, Sirius outshines the Sun. Anything living there will point its concentrators at Sirius rather than at the Sun. But they can still evolve, survive.
     “Quite the numbersmith you’ve proved to be, Erma. So we’ll both be rich . . .”

From BACKSCATTER by Gregory Benford (2013)

Mining Techniques


      Imagine a metal asteroid spewing molten iron, and you’ve got the gist of ferrovolcanism — a new type of planetary activity proposed recently by two research teams.

     When NASA launches a probe to a metal asteroid called Psyche in 2022, planetary scientists will be able to search for signs of such volcanic activity in the object’s past. The new research “is the first time anyone has worked out what volcanism is likely to look like on these asteroids,” says planetary scientist Jacob Abrahams of the University of California, Santa Cruz.

     Metal asteroids are thought to be the exposed iron-rich cores of planetesimals that suffered a catastrophic collision as the solar system was developing, before they could grow into full-sized planets. The naked core would have been exposed to cold space while still molten. And it would have cooled and solidified from the outside in, forming a solid iron crust that would be denser than the underlying molten iron, say Abrahams and planetary scientist Francis Nimmo, also of the University of California, Santa Cruz.

     That kind of density mismatch is part of what can create volcanoes on Earth — lighter, more buoyant material rising up through cracks in the crust — and could have led to iron-spewing volcanoes on metal asteroids as the objects cooled long ago, the researchers speculate.

     Another way that ferrovolcanism could have occurred on metal asteroids was described by planetary scientist Brandon Johnson of Brown University in Providence, R.I. If a cooling iron core also contained a little bit of rock and sulfur, he theorizes, the core could have been cocooned beneath a rocky, not iron, crust. As the core cooled further, pockets of iron-rich liquid with extra sulfur dissolved in them would have hardened more slowly than surrounding materials. Those pockets would be more buoyant than the rock above them, so they’d force their way up and out, Johnson says.

     If Psyche has such a rocky veneer over iron, that could explain why the asteroid appears much less dense than expected, Johnson says. The two groups, which worked independently from one another, presented their ideas March 21 at the Lunar and Planetary Science Conference in The Woodlands, Texas.

     “We kept thinking, ‘It’s too wild, it can’t be right,’ ” says Johnson, of the idea of ferrovolcanism. “But we couldn’t prove to ourselves that it wouldn’t work. Because another group came up with the same idea at the same time, it can’t be too wild.”

     The Psyche spacecraft can look for signs of past ferrovolcanism when it arrives at the eponymous asteroid, located in the main asteroid belt between Mars and Jupiter, in 2026, says mission principal investigator and planetary scientist Lindy Elkins-Tanton.

     What’s more, if Psyche were rotating while it cooled, its molten core could have generated a magnetic field. Volcanic flows that cooled on the asteroid’s surface would have recorded evidence of that magnetic field. “We might actually be able to see these things,” says Elkins-Tanton, of Arizona State University in Tempe. “I think it’s really cool.”


I've been saying this for quite a while. You simply cannot mine in space the way you do on Earth.

  1. Everything floats, which is a problem. A lot of mining methods involve dynamiting a rock face and letting it fall into a chamber.
  2. You have little to no water. Mining needs a LOT of water. Everything from shotcrete to secure mining ceilings and walls to lubrication and coolant. Groundwater allows the use of resistivity surveys, which are a simple way of identifying geology in the area. Usually you have too much of it anyway so you pump it out to lower the water table so it's not really ever an issue.
  3. Most mines use some kind of gravity separation system, combined with a water suspension, to separate ore by density. Obviously this is a challenge given 1 and 2. Not so much of a problem for asteroids but then they have the hassle of everything floating.
  4. DUST. It's everywhere, sticks to everything, including camera surfaces and you can't blow it off in a vacuum unless you plan on wasting volatiles. An asteroid mining operation is eventually going to be coated in an orbiting dust cloud unless you have big sheets scooping the stuff out of the vacuum.
  5. Everything is kak heavy in mining. Even with BFRs, you are going to have serious mass constraints for large scale mining. And everything breaks, and takes longer… just look at Curiosity's little rock drill, which broke down after 15 uses.
  6. And of course your nearest replacement is a 6 month transfer orbit away, depending on where you're mining. Mining, oil & gas companies blow huge amounts of money to send spares out. Something breaks, a replacement is either on site or being loaded onto a plane before you get off the phone to HQ.

That's why I think lunar mining is more feasible than asteroid mining. You have access to:

  1. Some gravity
  2. Daily, hourly launch windows to Earth
  3. Short trip times for replacements or experts
  4. Nobody worrying that you will actually drop the asteroid on a city (far fetched though that is)
  5. Access to volatiles
  6. Bulk ore export is easy, just use a linear accelerator, orbital skyhook or even locally manufactured propellant
  7. Asset fluidity. This is a big thing, because if your mining operation goes belly up, you have a reasonable prospect of selling your assets (habs, power generation, rovers, shuttles) to some other base. A failed business venture on an asteroid leaves billions of dollars of high-tech, specialised machinery that needs at least 6 months to get back to Earth orbit where it may sit for years waiting for another target.
  8. Likewise, with 7, you also have access to local lunar resources. It's not just going to be one single base on them, it'll be dozens of small operations. In addition to the several mining bases, you'll have what's like the equivalent of a deep water harbour — a linear accelerator or whatever — to export the goods, which can be government subsidised the way they are on Earth. You also have habitats, eventually large enough even for families, research facilities, sophisticated manufacturing and… competition. The great energiser.

Finally, the "enormous" PGM market is not actually that big and there are still plenty of platinum reserves on Earth

Major downside is the delta V to get there and the long day.

Google+ thread comment by Troy Campbell (2018)

The chosen crater is nearly 1/8 mile in diameter, making it a good target for landing. It sits just forward of the nearly horizontal polar table with respect to the equator and is tipped slightly toward Mars for a good view while providing lateral and aft shielding with its walls. The rotating solar array, addressed below, can be anchored on the smooth plain just behind and above the habitat/lab crater at highest latitude, less than 1/10 mile away.

Landing here, with the low surface gravity and low surface density, will be more of a rendezvous and docking maneuver than a landing. I would not expect that there will be much in the way of exhaust scouring of regolith but some dust may be redistributed by vernier firings. Larger RCS thrusters will most likely not be used to control the descent but instead be reserved for abort. I would expect that a controlled slow fall to the surface, combined with auger screw legs that are counter-rotating at time of touchdown to drill into the 50 meter thick regolith blanket upon contact, would be the most effective method of staying there once you get there. Another method would be to fire harpoons into the regolith from altitude and reel yourself in. In this low gravity field, the surface will not be very dense. It will not behave in ways that normal dirt would be expected to behave in a one g field, as there has been nothing much to compress it. Think of it as deep snow and how efficient you are at moving in that. It may support you after initial compression but gives way under thrust. Moving shielding materials and larger equipment around would most likely be done with small assist devices, perhaps gas thruster powered, though the dust kicked up by them may itself be problematical.

Huge structures and how to erect and support them are not as difficult as they may seem... merely different in how you go about it. For the most part, you can just land them all in one piece. Keeping tall ones from falling over is another story. Guy wires would be largely ineffective. At the low level on the mast to which they would have to be attached, the lever arm of the upper, unsupported section of the mast would have a large advantage on the lower portion and the low density of the regolith would pose little resistance to the anchors pulling out under steady tension. One good hit off center with a meteor, harmonic oscillations build up and the whole thing gyrates, goes out of column and topples over or flies off into space. Think of it as driving a stake into Corn Flakes, Rice Crispies or Grape Nuts.

Given these limitations for conventional stabilization, one is also given rise to a solution, Just as objects can be pulled out of the regolith with ease, so may large objects be thrust into it. The masts for the solar arrays are designed having a long, narrow, sharp, fluted cone base that is thrust fairly deeply into the regolith by firing it at low velocity from above the surface. The panels are assembled to it and unfurl in place. The whole mast, panels and all, turns on a dual full-floating bearing near the base, driven by a heliostat to follow the Sun as Deimos travels around Mars. The array is situated so that only one panel is eclipsed by another at one time, ensuring that power fluctuations will be kept within design limits. Burying the habitat can be done in a number of ways, but it does pose its own problems. Heavy equipment would not be very effective in this low gravity field, if at all—mostly because it wouldn't be heavy. Get a blade full of dirt and your tracks will simply dig out from under you.

It may take a while to move that much mass, but a good ol' HUGE hand shovel might be all that is really needed—but that isn't very glamorous. A beefed-up RMS style arm on top of the habitat that pulls the crater limb in backhoe fashion would be most effective, as the lab is already screwed into the surface. Leverage, rather than brute force. With the scraper removed, the arm serves as a crane for working in close proximity to the lab.

On the other hand, a triad of properly calculated and placed shaped charges would be most efficient to move the dirt where you want it. WHUMP! Create three new craters and do seismic studies all at the same time. It'll take a while for the dust to settle in this low gravity but we'll at least get a show and some new scenery out of the operation.

From WORKING ON DEIMOS by B. E. Johnson (2000)

This is a followup to the early lunar mining post.
I assume a suitable asteroid has been delivered to EML1 or lunar orbit for processing. I also assume that a painstakingly detailed dissection with full science yield is not necessary; relevant samples and readings are assumed to have been taken and the rock is available to be destroyed. The mission is in no particular hurry to complete the task, but several groups are to be given a chance at testing process technology.

containment bag, 200kg
grinder arm, 2000kg
solar oven, 600kg
ore sorting, 1000kg
ore processing, 1700kg
cryogenic processing, 1000kg
power, 400kg
radiators, 800kg
storage bags, 800kg
water tanks, 1000kg
LOX tanks, 10,000kg (could be subbed by a visiting ULA ACES-121 tanker)
Total mass: 9.6t with tanker, 19.6t standalone

yield (assuming ideal asteroid composition and 1000 tons material):
540 tons of magnesium silicates (shielding)
224 tons of iron
100 tons of water
100 tons of oxygen
30 tons of carbon
4.5 tons of nickel
600kg of cobalt

 Unlike the surface mission, this mission has effectively no gravity. Material processing methods become radically different thanks to sir Newton and his bothersome but useful laws. We also have a limited amount of material, something in the range of 500-1000t and perhaps 10m diameter. The material is from a C-type carbonaceous chondrite with little to no near-surface water or low-temp volatiles.

 First off, the entire body must be enclosed in a bag to avoid debris or loss of volatiles. Allowing a radius of 8 meters (in case of oblong shapes), 800m² of material is required. Aluminized Spectra seems like a reasonable choice, somewhere around 0.075 kg/m² or around 60kg for the whole bag. Triple that to allow for some strong lines and round off to 200kg for a bag that can distribute tension forces.

 The body has to be crushed, pulverized or otherwise broken apart before heating. An unexpected pocket of frozen nitrogen in a hard crust could cause a bad day when it violently sublimates. However it is done, the tool should avoid any net forces. Single-bit drills, egg-beater grinders and similar designs should be avoided since they will induce a spin or cause the toolhead to walk.
 I think a four-drum grinder would work; this would be an articulated arm with four 'hands' each with a toothed drum at the end. The teeth would be blunt enough to be safe inside the bag (won't cut the bag, should deflect off of it). Crushing force would be rotational inertia in the drum plus compression between each pair of opposing drums. Each pair of drums would be at 90° to each other; the outer pair would chew on the face of the rock and produce a stream of material into the inner pair, which would block any bigger chunks and pass the rest up the tool and into the processing equipment. This tool induces a force that tends to pull the tool into the rock, which is useful and controllable. The articulated arm allows it to reach the full diameter of the body. It would be attached to a ring in the bag, so the reaction force will keep the bag taut and keep an open space around the arm. Something roughly similar to Canadarm (450kg mass, 3300kg payload, 15m reach) seems reasonable, but let's quadruple the mass to account for the grinding heads and an internal auger; call it 2 tons.

(ed note: part 2 here)

From EARLY ASTEROID MINING by Chris Wolfe (2015)

Mining in Zero Gravity

Although it might seem easier to move materials in zero gravity than on Earth, inertia, not overcoming gravity, is the major effect to consider. Little experience has been gained in weightlessness. One sample problem is that of holding fracturing and excavation tools to the face of an asteroid. On Earth, equipment hold-down is accomplished solely by gravity. Another sample problem is containing the excavated material, either large or small fragments. Rock fracturing places an initial velocity on the broken material. On Earth, gravity quickly collects the broken rock. In weightlessness, the broken rock will behave like out-of-control billiard balls, a potentially destructive game. Furthermore, the fines that are always generated by rock fracturing may obscure vision and clog equipment. Our study group did not have time to consider the full significance of working complex equipment in zero g, but we note that this problem needs in-depth study.

A Conceptual Asteroid Mining Method

The study group did not have the time or the resources to fully design a baseline asteroid mining method. This incomplete concept of an asteroid mining method is intended to illustrate how some of the problems could be overcome. As with the lunar proposal, the concept should be used to promote discussion of asteroid mining problems, but not to promote the method itself. Assuming that the ΔV for the available asteroid is small and that only a modest amount of material is needed, I propose the following method to accomplish a first mission.

After arriving at the asteroid, the operators place one or more cables around the body. The asteroid proposed to the group for study was no more than a few hundred meters in diameter. Placing a cable around the body appeared to us much easier than anchoring the end of a shorter cable. Anchoring in rock can be a difficult process. If augering is used in weightlessness, a method must be devised to hold the augering tool down while it is working. The most desirable asteroids have very low strengths, good for mining but poor for anchoring. Quite long cables are possible, on the order of 1000 meters. The cable is easily placed and provides easy movement of the mining tool. One disadvantage of a long cable is the mass; for example, a cable 1 inch in diameter weighs 1.6 pounds per foot on Earth (has a mass of 2.4 kg/m).

The cable holds a cutter head or other rock-fracturing tool in place and provides sufficient working force for it. The cutter head is designed to excavate in addition to fracturing the soft rock. A conical Kevlar collection bag is placed over the area to be mined and is held in place by the same cable (fig. 24). The flexible bag holds its shape because of the rotation of the asteroid. The spin also aids in collecting the fragmented asteroid material.

The cutter head travels back and forth along its restraining cable, cutting material until the collection bag is filled (fig. 25). The cutter is similar to the coal shear currently used in Iongwall operations but is designed to overcome the asteroid’s low gravity and fling material past synchronous orbit so that centripetal force effects collection. Dust production around the cutter head remains a problem. Dusty environments obscure vision and thus increase problems in controlling teleoperated systems or in monitoring automated systems. However, direct vision may not be so important on a body that proves to be homogeneous in structure and composition.

After the required amount of material is collected in the bag, it is “lowered” away from the body, allowing the bag and material to steal angular momentum from the asteroid. For low ΔV return flights, there may be sufficient energy available to slingshot the load back to Earth. Deceleration at Earth could be accomplished by aerobraking. The collection bag might be designed to act as an aerobrake shield in addition to being reusable. The bag could also serve as a retort for carbonyl or other types of processing during return.

An alternative, but basically similar, method still uses the bag and cable. However, a large block of asteroid material is collected, not by mechanical excavation but by blasting material into the bag. Instead of a shear, which could have trouble negotiating the asteroid surface, an explosive is used. The cable holds in place a drilling machine, which drills a series of blast holes. The drill holes and charges are carefully designed to excavate a large section of the asteroid. The explosive charges breakout the desired amount of material, and the force of the explosion moves the material into the collection bag. Pattern drilling designed to create shaped explosions has achieved some success on the Earth and is finding more applications. The explosive method appears simpler in equipment and operation than the shear, but the blasting must have a very high degree of control. Uncontrolled fragmentation of the cabled body would be a disaster. I have not considered a suitable blasting agent. The reader can visualize this alternative method by imagining a drill rig instead of the shear in figures 24 and 25.

While the sizing of the return loads requires further study, the same basic mining scheme should be able to handle a range of sizes. It is not completely clear whether one large load or several smaller loads would be better, although several smaller loads might be more manageable, while allowing more flexible return flight plans.


Because it appears to be easier and cheaper to accomplish, the lunar mine is probably a better first project to exploit nonterrestrial materials than is the asteroid mine.

While not causing any increased transportation costs, the long, slow travel to and from the near-Earth asteroids would decrease the rate of return on capital investment.

As in the lunar LOX-to-LEO project, the asteroid mining system must be kept as simple as possible. Simplicity eases problems and lowers the costs of development, equipment, and operations.

A manned mission would make the mining operation much simpler, but it would greatly increase the complexity and cost of the deep space transport vehicle.

Teleoperation seems a good compromise between automation and manned missions, but the choice requires much more study.

Even if specific space program goals or higher costs eventually preclude an asteroid mission, the rich and varied asteroid materials require that the option of mining an asteroid be studied. Given a goal of providing a range of materials for use in cislunar space, lunar projects must be demonstrated to be superior before asteroid missions are abandoned.

From ASTEROID MINING by Richard E. Gertsch. Collected in Space Resources NASA SP-509 vol 3

Mining With Microbes

Nanotechnology is the hot new technology, or is it really new? Using tiny machines to perform molecular tasks is basically what fermentation is, which has been used since the neolithic era to make such things as beer, wine, and cheese. The only difference is one uses naturally occuring microbes as nanomachines instead of rolling your own.

In the world of mining useful elements, this is called Bioleaching.

Bioleaching is currently used to extract such elements as copper, zinc, lead, arsenic, antimony, nickel, molybdenum, gold, silver, and cobalt. The main advantages are

  • Uses much less energy than roasting and smelting
  • Is a much cheaper process due to fewer steps and no need for close supervision
  • Will work on ores where the valuable element concentration is too low to profitably extract by conventional means

The main disadvantage is that bioleaching is much slower.

The company Deep Space Industries is looking into injecting genetically engineered microbes into asteroid and moons. These microbes would concentrate the valuable elements into chunks worth the while of a visit by a robot asteroid miner. One would think that the lack of air and utter cold would instantly kill the microbes, but these germs are remarkably tough. Some microbes do not even need oxygen, and many asteroids get enough solar heat to be quite cozy inside.

Bioleaching is also useful for recycling. For example, a broken circuit board can be thrown into the bioleach tank, reduced to component elements, then sent to the 3D printer. No need for an energy expensive fusion torch as long as there is no hurry.


      The asteroid-mining firm Deep Space Industries (DSI) is investigating the feasibility of injecting bioengineered microbes into space rocks far from Earth, to get a jump on processing their valuable resources.
     "You could come back [to the asteroids] in 10 to 20 years and have a preprocessed pile of materials," Joseph Grace, of DSI and NASA's Ames Research Center, told

     The scientists working on the concept envision launching a small probe that DSI is developing, called Mothership, out to a promising near-Earth asteroid in deep space. Mothership would be carrying a number of tiny CubeSats, one of which would deploy and spiral down
     The CubeSat would then inject into the asteroid a low-temperature fluid laden with bacteria, which would propagate through cracks and fissures generated by the injection process. Over time, the microbes — genetically engineered to process metals efficiently — would break down harmful compounds within the asteroid and/or transform resources into different chemical states that are more amenable to extraction.
     This work would be slow, but the bacteria would be doing it for free (after the initial expenditure of getting them out to the asteroid, of course).
     "The use of self-sustaining biomining mitigates the need for sustained docking, anchoring, drilling, processing or other technically challenging traditional mining approaches," Grace and his colleagues wrote in a poster they presented at AGU. "If shown to function, the use of life to preprocess valuable deep-space resources could change the economic practicality of a large range of human activity in space."

     The DSI team is trying to bring the picture into clearer focus. For instance, the researchers surveyed data about the 11,000 known near-Earth asteroids (NEAs), to estimate how many of them might have the right interior temperature profiles to support microbial life.
     The results, presented in the team's AGU poster, were encouraging: About 2,800 NEAs appear to be potentially habitable, defined as possessing projected interior temperatures that hover between 23 degrees and 212 degrees Fahrenheit (minus 5 to 100 degrees Celsius) for extended periods, without ever exceeding 212 F.
     Furthermore, 120 of these asteroids likely have a "preferred" interior temperature, with a range between 59 and 113 F (15 to 45 C) — again, never exceeding 212 F.
     The next step involves seeing how well metal-processing microbes can live and metabolize within rock fractures in a vacuum environment. DSI has submitted grant proposals requesting funding to do this work


      Space missions rely utterly on metallic components, from the spacecraft to electronics. Yet, metals add mass, and electronics have the additional problem of a limited lifespan. Thus, current mission architectures must compensate for replacement.
     In space, spent electronics are discarded; on earth, there is some recycling but current processes are toxic and environmentally hazardous. Imagine instead an end-to-end recycling of spent electronics at low mass, low cost, room temperature, and in a non-toxic manner.
     Here, we propose a solution that will not only enhance mission success by decreasing upmass and providing a fresh supply of electronics, but in addition has immediate applications to a serious environmental issue on the Earth. Spent electronics will be used as feedstock to make fresh electronic components, a process we will accomplish with so-called 'urban biomining' using synthetically enhanced microbes to bind metals with elemental specificity.
     To create new electronics, the microbes will be used as 'bioink' to print a new IC chip, using plasma jet electronics printing. The plasma jet electronics printing technology will have the potential to use martian atmospheric gas to print and to tailor the electronic and chemical properties of the materials.
     Our preliminary results have suggested that this process also serves as a purification step to enhance the proportion of metals in the 'bioink'. The presence of electric field and plasma can ensure printing in microgravity environment while also providing material morphology and electronic structure tunabiity and thus optimization.
     Here we propose to increase the TRL level of the concept by engineering microbes to dissolve the siliceous matrix in the IC, extract copper from a mixture of metals, and use the microbes as feedstock to print interconnects using mars gas simulant. To assess the ability of this concept to influence mission architecture, we will do an analysis of the infrastructure required to execute this concept on Mars, and additional opportunities it could offer mission design from the biological and printing technologies. In addition, we will do an analysis of the impact of this technology for terrestrial applications addressing in particular environmental concerns and availability of metals.


      Scientists at Indiana University have created a highly efficient biomaterial that catalyzes the formation of hydrogen — one half of the “holy grail” of splitting H2O to make hydrogen and oxygen for fueling cheap and efficient cars that run on water.
     A modified enzyme that gains strength from being protected within the protein shell — or “capsid” — of a bacterial virus, this new material is 150 times more efficient than the unaltered form of the enzyme.
     The process of creating the material was recently reported in “Self-assembling biomolecular catalysts for hydrogen production” in the journal Nature Chemistry.
     “Essentially, we’ve taken a virus’s ability to self-assemble myriad genetic building blocks and incorporated a very fragile and sensitive enzyme with the remarkable property of taking in protons and spitting out hydrogen gas,” said Trevor Douglas, the Earl Blough Professor of Chemistry in the IU Bloomington College of Arts and Sciences’ Department of Chemistry, who led the study. “The end result is a virus-like particle that behaves the same as a highly sophisticated material that catalyzes the production of hydrogen.”

     The genetic material used to create the enzyme, hydrogenase, is produced by two genes from the common bacteria Escherichia coli, inserted inside the protective capsid using methods previously developed by these IU scientists. The genes, hyaA and hyaB, are two genes in E. coli that encode key subunits of the hydrogenase enzyme. The capsid comes from the bacterial virus known as bacteriophage P22.
     The resulting biomaterial, called “P22-Hyd,” is not only more efficient than the unaltered enzyme but also is produced through a simple fermentation process at room temperature.
     The material is potentially far less expensive and more environmentally friendly to produce than other materials currently used to create fuel cells. The costly and rare metal platinum, for example, is commonly used to catalyze hydrogen as fuel in products such as high-end concept cars.
     “This material is comparable to platinum, except it’s truly renewable,” Douglas said. “You don’t need to mine it; you can create it at room temperature on a massive scale using fermentation technology; it’s biodegradable. It’s a very green process to make a very high-end sustainable material.”
     In addition, P22-Hyd both breaks the chemical bonds of water to create hydrogen and also works in reverse to recombine hydrogen and oxygen to generate power. “The reaction runs both ways — it can be used either as a hydrogen production catalyst or as a fuel cell catalyst,” Douglas said.


(ed note: this is science fiction)

mycofibrillin was originally a product designed by the space division of Molecular Architecture, ICC, under the Mycofibrillin™ trademark. It was a development of early experiments in creating spaceborne life, such as the regoformer “asteroid lichen”, which sustains itself using solar energy and water extracted from icy regolith.

Unlike its predecessors, mycofibrillin was designed not as an experiment or artwork, but as a functional tool. A designed-from-scratch neogen, it was a reinterpretation of various fungoid lifeforms – which took the form of an intertwined mat of fibers – for the space environment: a recreation of similar reaction networks making use of silicates, silanes, and silicones, at much lower temperatures, relying upon both a trickle of solar energy and provided radio-frequency energy broadcasts to power its metabolism.

The function of mycofibrillin was simply to stabilize aggregate-class “rubble pile” asteroids for relocation, or indeed for other exploitation. A rubble pile infected with a mycofibrillin culture, along with a microwave beacon to feed its growth phase, would swiftly find itself perfused by silicone-sheathed rhizomorphic hyphae of substantial tensile strength, acting to bind the many components of the rubble pile together into a single coherent mass.

Since this promising start, later offshoot technologies have included the thermophilic bionanotech weaves developed in conjunction with the chfsssc for stabilizing tectonically vulnerable regions of planetary crusts along with a variety of refined mycofibrillin derivatives, including a number of strains whose tensile strength is claimed to be suitable for maintaining the stability of large asteroids or small planetesimals when spun up to usable gravity-simulating speeds (although, in practice, the majority of residents of these worlds prefer microgravity environments).

– The Biotechnology of Space: A History, Kynthia Naratyr-ith-Naratyr

From TRUFFLE HOUSE by Alistair Young (2016)

(ed note: this is science fiction)

These were pavements of the commonest vacuum organism, mosaics made of hundreds of different strains of the same species. Here and there bright red whips stuck out from the pavement; a commensal species that deposited iron sulphate crystals within its integument. The pavement seemed to stretch endlessly below her. No probe or proxy had yet reached the bottom of Tigris Rift, still more than thirty kilometers away. Microscopic flecks of sulfur-iron complexes, sloughed cells and excreted globules of carbon compounds and other volatiles formed a kind of smog or snow, and the vacuum organisms deposited nodes and intricate lattices of reduced metals that, by some trick of superconductivity, produced a broad-band electromagnetic resonance that pulsed like a giant's slow heartbeat.

Eighty years ago, an experiment in accelerated evolution of chemoautotrophic vacuum organisms had been set up on a planetoid in the outer edge of the Kuiper Belt. The experiment had been run by a shell company registered on Ganymede but covertly owned by the Democratic Union of China. In those days, companies and governments of Earth had not been allowed to operate in the Kuiper Belt, which had been claimed and ferociously defended by outer system cartels. That hegemony had ended in the Quiet War, but the Quiet War had also destroyed all records of the experiment; even the Democratic Union of China had disappeared, absorbed into the Pacific Community.

Margaret's crew had discovered that the vacuum organisms had proliferated wildly in the deepest part of the Rift, deriving energy by oxidation of elemental sul­fur and ferrous iron, converting carbonaceous material into useful organic chemicals. There were crusts and sheets, things like thin scarves folded into fragile vases and chimneys, organ pipe clusters, whips, delicate fretted laces. Some fed on others, one crust slowly overgrowing and devouring another. Others appeared to he para­sites, sending complex veins ramifying through the thalli of their victims. Water-mining organisms recruited sulfur oxidizers, trading precious water for energy and forming warty outgrowths like stromatolites. Some were more than a hundred meters across, surely the largest prokaryotic colonies in the known Solar System.

All this variety, and after only eighty years of accelerated evolution! Wild beauty won from the cold and the dark. The potential to feed billions. The science crews would get their bonuses, all right; the citizens would become billionaires.

Clearly, the experiment had far exceeded its parameters, but no one knew why. The AI that had overseen the experiment had shut down thirty years ago. There was still heat in its crude proton beam fission pile, hut it had been overgrown by the very organisms it had manipulated.

Its task had been simple. Colonies of a dozen species of slow growing chemo-autotrophs had been introduced into a part of the Rift rich with sulfur and ferrous iron. Thousands of random mutations had been induced. Most colonies had died, and those few which had thrived had been sampled, mutated, and reintroduced in a cycle repeated every hundred days.

But the Al had selected only for fast growth, not for adaptive radiation, and the science crews held heated seminars about the possible cause of the unexpected rich­ness of the reef's biota.

The reef could make the Ganapati the richest habitat in the Outer System, where expansion was limited by the availability of fixed carbon. Even a modest-sized comet nucleus, ten kilometers in diameter, say, and salted with only one hundredth of one percent carbonaceous material, contained fifty million tons of carbon, mostly as methane and carbon monoxide ice, with a surface dusting of tarry long chain hydrocarbons. The problem was that most vacuum organisms converted simple carbon compounds into organic matter using the energy of sunlight captured by a variety of photosynthetic pigments, and so could only grow on the surfaces of planetoids. No one had yet developed vacuum organisms that, using other sources of energy, could efficiently mine planetoid interiors, but that was what accelerated evolution appeared to have produced in the reef. It could enable exploitation of the entire volume of objects in the Kuiper Belt, and beyond, in the distant Oort Cloud. It was a discovery of incalculable worth.

From REEF by Paul McAuley (2000)

Mining Ships

Most mining ships are below, but don't miss Konstantin Asteroid Miner in the realistic ship section. Also Alpha LEOstation in the space station section.


(ed note: asteroid miner Thad Allen does not have a habitat module. Instead he has a suit of Osprey Space Armor. This is a space suit that can actually keep him alive for a couple of months. Be told that the manufacturers make no claim that the suit will keep you comfortable for a couple of months.)

His "planet" was the smallest in the solar system, and the loneliest, Thad Allen was thinking, as he straightened wearily in the huge, bulging, inflated fabric of his Osprey space armor. Walking awkwardly in the magnetic boots that held him to the black mass of meteoric iron, he mounted a projection and stood motionless, staring moodily away through the vision panels of his bulky helmet into the dark mystery of the void.

His welding arc dangled at his belt, the electrode still glowing red. He had just finished securing to this slowly-accumulated mass of iron his most recent find, a meteorite the size of his head.

Five perilous weeks he had labored, to collect this rugged lump of metal—a jagged mass, some ten feet in diameter, composed of hundreds of fragments, that he had captured and welded together. His luck had not been good. His findings had been heart-breakingly small; the spectro-flash analysis had revealed that the content of the precious metals was disappointingly minute.

On the other side of this tiny sphere of hard-won treasure, his Millen atomic rocket was sputtering, spurts of hot blue flame jetting from its exhaust. A simple mechanism, bolted to the first sizable fragment he had captured, it drove the iron ball through space like a ship.

Through the magnetic soles of his insulated boots, Thad could feel the vibration of the iron mass, beneath the rocket's regular thrust. The magazine of uranite fuel capsules was nearly empty, now, he reflected. He would soon have to turn back toward Mars.

Turn back. But how could he, with so slender a reward for his efforts? Meteor mining is expensive. There was his bill at Millen and Helion, Mars, for uranite and supplies. And the unpaid last instalment on his Osprey suit. How could he outfit himself again, if he returned with no more metal than this? There were men who averaged a thousand tons of iron a month. Why couldn't fortune smile on him?

He knew men who had made fabulous strikes, who had captured whole planetoids of rich metal, and he knew weary, white-haired men who had braved the perils of vacuum and absolute cold and bullet-swift meteors for hard years, who still hoped.

From SALVAGE IN SPACE by Jack Williamson (1933)

The quiet of space was around him, now that his ears had learned to forget the hum of the ship's drive. Two weeks' worth of tightly coiled stubble covered his jaw and the shaved scalp on either side of his cottony Belter crest. If be concentrated he could smell himself. He had gone mining in Saturn's rings, with a singleship around him and a shovel in his hand (for the magnets used to pull monopoles from asteroidal iron did look remarkably like shovels).

A century ago monopoles had been mere theory, and conflicting theory at that. Magnetic theory said that a north magnetic pole could not exist apart from a south magnetic pole, and vice-versa. Quantum theory implied that they might exist independently.

The first permanent settlements had been blooming among the biggest Belt asteroids when an exploring team found monopoles scattered through the nickel-iron core of an asteroid. Today they were not theory, but a thriving Belt industry. A magnetic field generated by monopoles acts in an inverse linear relationship rather than an inverse square. In practical terms, a monopole-based motor or instrument will reach much further. Monopoles were valuable where weight was a factor, and in the Belt weight was always a factor. But monopole mining was still a one man operation.

Nick's luck had been poor. Saturn's rings were not a good region for monopoles anyway; too much ice, too little metal. The electromagnetic field around his cargo box probably held no more than two full shovelfuls of north magnetic poles. Not much of a catch for a couple of weeks backbreaking labor. . . but still worth good money at Ceres.

The solar system is big and, in the outer reaches, thin. In the main Belt, from slightly inside Mars's orbit to slightly outside Jupiter's, a determined man can examine a hundred rocks in a month. Further out, he's likely to spend a couple of weeks coming and going, just to look at something he hopes nobody else has noticed.

The main Belt is not mined out, though most of the big rocks are now private property. Most miners prefer to work the Belt. In the Belt they know they can reach civilization and civilization's byproducts: stored air and water, hydrogen fuel, women and other people, a new air regenerator, autodocs and therapeutic psychomimetic drugs.

Brennan didn't need drugs or company to keep him sane. He preferred the outer reaches. He was in Uranus's trailing Trojan point, following sixty degrees behind the ice giant in its orbit. Trojan points, being points of stable equilibrium, are dust collectors and collectors of larger objects. There was a good deal of dust here, for deep space, and a handful of rocks worth exploring.

Had he found nothing at all, Brennan would have moved on to the moons, then to the leading Trojan point. Then home for a short rest and a visit with Charlotte; and, because his funds would be low by then, a paid tour of duty on Mercury, which he would hate.

Had he found pitchblende he would have been in the point for months.

None of the rocks held enough radioactives to interest him. But something nearby showed the metallic gleam of an artifact. Brennan moved in on it, expecting to find some Belt miner's throwaway fuel tank, but looking anyway. Jack Brennan was a confirmed optimist.

The artifact was the shell of a solid fuel rocket motor. Part of the Mariner XX, from the lettering.

The Mariner XX, the ancient Pluto fly-by. Ages ago the ancient empty shell must have drifted back toward the distant sun, drifted into the thin Trojan-point dust and coasted to a stop. The hull was pitted with dust holes and was still rotating with the stabilizing impulse imparted three generations back.

As a collector's item the thing was nearly beyond price. Brennan took phototapes of it in situ before he moved in to attach himself to the flat nose and used his jet backpac to stop the rotation. He strapped it to the fusion tube of his ship, below the lifesystem cabin. The gyros could compensate for the imbalance.

In another sense the bulk presented a problem.

He stood next to it on the slender metal shell of the fusion tube. The antique motor was half as big as his mining singleship, but very light, little more than a metal skin for its original shaped-core charge. If Brennan had found pitchblende the singleship would have been hung with cargo nets under the fuel ring, carrying its own weight in radioactive ore. He would have returned to the Belt at half a gee. But with the Mariner relic as his cargo he could accelerate at the one gee which was standard for empty singleships.

It might just give him the edge he'd need.

If he sold the tank through the Belt, the Belt would take thirty percent in income tax and agent's fees. But if he sold it on the Moon, Earth's Museum of Spaceflight would charge no tax at all.

Brennan was in a good position for smuggling. There were no goldskins out here. His velocity over most of his course would be tremendous. They couldn't begin to catch him until he approached the Moon. He wasn't hauling monopoles or radioactives; the magnetic and radiation detectors would look right through him. He could swing in over the plane of the system, avoiding rocks and other ships. But if they did get him they'd take one hundred percent of his find. Everything.

Brennan smiled to himself. He'd risk it.

In the Belt, smuggling is illegal but not immoral. Smuggling was no more immoral to Brennan than forgetting to pay a parking meter would have been to a flatlander. If you got caught you paid the fine and that was that.

There are few big cargo ships in the Belt. Most miners prefer to haul their own ore. The ships that haul large cargoes from asteroid to asteroid are not large; rather, they are furnished with a great many attachments. The crew string their payload out on spars and rigging, in nets or on lightweight grids. They spray foam plastic to protect fragile items. spread reflective foil underneath to ward off hot backlighting from the drive flame, and take off on low power.

The Blue Ox was a special case. She carried fluids and fine dusts; refined quicksilver and mined water, grain, seeds, impure tin scooped molten from lakes on dayside Mercury, mixed and dangerous chemicals from Jupiter's atmosphere. Such loads were not always available for hauling. So the Ox was a huge tank with a small threeman lifesystem and a fusion tube running through her long axis; but, since her tank must sometimes become a cargo hold for bulky objects, it had been designed with mooring gear and a big lid.

Nilsson's own small, ancient mining ship had become the Ox's lifeboat. The slender length of its fusion tube, flared at the end, stretched almost the length of the hold. There was an Adzhubei 4-4 computer, almost new; there were machines intended to serve as the computer's senses and speakers, radar and radio and sonics and monochromatic lights and hi-fi equipment. Each item was tethered separately, half a dozen ways, to hooks on the inner wall.

Nilsson nodded, satisfied, his graying blond Belter crest brushing the crown of his helmet. "Go ahead, Nate."

Nathan La Pan began spraying fluid into the tank. In thirty seconds the tank was filled with foam which was already hardening.

"Close 'er up."

Perhaps the foam crunched as the great lid swung down. The sound did not carry. Patroclus Port was in vacuum, open beneath the black sky.

The captive ship was small. Phssthpok found little more than a cramped life support system, a long drive tube, a ring-shaped liquid hydrogen tank with a cooling motor. The toroidal fuel tank was detachable, with room for several more along the slender length of the drive tube. Around the rim of the cylindrical life support system were attachments for cargo, booms and folded fine-mesh nets and retractable hooks.

He did find inspection panels in the drive tube. Within an hour he could have built his own crystal-zinc fusion tube, had he the materials. He was impressed. The natives might be more intelligent than he had guessed, or luckier. He moved up to the lifesystem and through the oval door.

The cabin included an acceleration couch, banks of controls surrounding it in a horseshoe, a space behind the couch big enough to move around in, an automatic kitchen that was part of the horseshoe, and attachments to mechanical senses of types frequently used in Pak warfare. But this was no warship. The natives' senses must be less acute than Pak senses. Behind the cabin were machinery and tanks of fluid, which Phssthpok examined with great interest.

One thing he understood immediately.

He was being very careful with the instrument panel. He didn't want to wreck anything before he found out how to pull astronomical data from the ship's computer. When he opened the solar storm warning to ascertain its purpose, he found it surprisingly small. Curious, he investigated further. The thing was made with magnetic monopoles.

From PROTECTOR by Larry Niven (1973)

141972 Syntherum (Gelidaceous-class asteroid)
e’Luminiaren Belt
Lumenna-Súnáris System

A thousand years ago, they used to think there wouldn’t be much water in space, and we’ll all be stuck out here in a barren desert, sending home for bottled oceans.

Well, fortunately not. There’s plenty – more water than there is just about anything else worth digging up outside a gas giant. It’s just nowhere near the places where you actually need the damn stuff, which is where we come in.

We being, first, the Initiative’s tanker, Adorably Aqueous, keeping station about a mile off and waiting to load up with 32,000 tons of water for the thirsty habs between here and Talentar high orbit;

Being, second, the dozen or so automated Seredháïc-class ice-miners sitting around down here on Syntherum, big 160-ton water-blimps with drive, drill, and ancillary equipment all packed into their tiny gondolas. They chop through the dusty crust of the ‘roid, pump steam down to melt the ice and slurp the water back. Shuffling back and forth between here and the tanker, they get it filled up in just a few hours, quick and clean.

And being, third, myself, Cathál Rian-ith-Ríëlle, hydrodynamic engineer, waterwright, and now spacer, with my candle and my trusty wrench.

Because where you have water, you have pipes, and where you have pipes, you have leaks, blockages, and all the rest.

Even in space, that means you need a plumber.

From WATER by Alistair Young (2015)

CFW NEO MicroMiner

This is from Asteroid Mining With Small Spacecraft And Its Economic Feasibility (2019)

The idea was that while mining Near Earth Asteroids (NEAs) for water and other volatiles could be profitable, it is real hard if you use huge monolithic robot spacecraft. Especially if you have separate robots for prospecting and refining. The report suggests replacing one or two monolithic mining robots with a swarm of 200 or 400 cheaper tiny robots. Their analysis indicates that a swarm of as few as 50 could possibly turn a profit, while 400 of the little darlings could reach the profitability break-even point in less than six years.

The tiny mining robots would have a mass under 500 kg each, delivers 100 kg of water per trip, have a cost of only $113.6 million US per unit, and can reach NEAs within a range of ~0.03 AU relative to Terra's orbit (delta-V around 437 m/s one way, 874 m/s with refueling with water at target asteroid).

Figure 2 is a 2011 estimate of the water in asteroids available to be harvested in near Terra space (from Asteroid Resource Map For Near-Earth Space). I am unclear on their methodology; but the report says assuming that each kilogram of asteroid is 8.5% water, a given robot has to extract 250 kg of water (100 kg payload + 150 kg refueling), and requires 437 m/s delta V for the return trip, Figure 2 says the robot has access to more than one million liters of asteroidal water.

The report looked at a variety of methods to extract water from asteroidal soil. The winner was Microwave drying. Microwaves only heat the water, not the soil, which is an advantage. Details about the losing methods can be found in the report. All the techniques require a cold trap to condense the water vapor into liquid water.

The above is a general overview of the mission architecture. It does assume that there have already been enough precursor prospecting missions to ensure there are enough asteroids with water deposits and are reachable (e.g., are not spinning too fast to land on, etc.).

Groups of mining robots in Terra parking orbit are dispatched to the prime asteroid canidates. Upon arrival the asteroids are given a closer look, just to double-check that they are worth-while. The asteroid is mapped closely, and the data is sent back home so that human beings can decide on landing sites. The state of the art of artificial intelligence will probably be too unreliable to trust with selecting a safe site for a hundred million dollar robot. And even if it is reliable enough, the insurance companies will probably insist on human judgement.

The robot miner will perform a slow (several hours) soft landing, so that the human ground controllers can cope with the communication timelag and so the robot won't be too severely damaged if it happens comes down a mite hard. The robot will then deploy anchors to keep it attached to the asteroid, since the pathetic gravity cannot be trusted to prevent the robot from drifing away.

Once anchored, the robot will start drilling asteroid regolith. As soon as enough soil is drilled, the microwave equipment will be deployed, and start zapping out the valuable water. The microwave is powered by solar panels, so operations will have to be put on pause when the rotation of the asteroid puts the Sun into eclipse.

The robot has to harvest enough water to [a] refill the reaction mass tanks and [b] fill the cargo tank. Once this is done, the robot will detach from the asteroid and perform the burn for home. At LEO it will dock (autonomously or teleoperated) with an orbital processing facility. The water cargo is delivered, and the profit is credited to the robot owner's bank account. The robot is inspected for maintenance issues, and either fixed or sent on its way back to the asteroids.


  1. The spacecraft should have a small structure: The spacecraft configuration should correspond to the parameters that define a small spacecraft for this application, i.e. a mass of < 500 kg.

  2. The spacecraft should be dimensioned in order to obtain around 100 kg of water: Up until now, there is no estimate of the actual demand of water in space. This makes it hard to determine the necessary quantity returned per asteroid run for a given operational cost. A value that has been utilized for calculations in past projects is 100 kg, this quantity should be obtainable if the asteroid is least 3 meters in diameter.

  3. The spacecraft should be able to be refueled in-situ with the extracted water and be able to operate with a water based propulsion system: The spacecraft should be able to resupply itself to ensure steady operation and to mitigate possible losses due to lack of propellant. Therefore, it should carry a water based propulsion system or a water compatible system.

  4. The spacecraft should carry imaging instruments in order to determine the best possible landing site: The best possible landing site is determined by the spinning rate, the surface mineral content and the shape of the asteroid.
  5. The spacecraft should incorporate reusable anchoring, storage and extraction systems to support mining operations.

  6. The spacecraft should have a high degree of autonomy to facilitate operations.

  7. The maximum travel distance of the spacecraft should be less than 0.1 AU from Earth: Near Earth Objects (NEOs) are asteroids and comets with perihelion distance of less than 1.3 AU. However, there are a large number of close approaches that are accessible for rendezvous at 0.1 AU, which limits the required propulsive capabilities.

  8. The spacecraft shall be capable of delivering the collected water to a space station upon returning to an appropriate orbit: Once the material has been extracted, it has to be delivered to the appropriate orbit. There, either docking or rendezvous might be required to deliver the material to a spacecraft or space station.

  9. The spacecraft cost must be minimized to improve the likelihood of economic feasibility.

  10. The spacecraft shall contain a backup propulsion system in order to be able to return to Earth if the water extraction is unsuccessful.

  11. The spacecraft shall be able to repeat mining trips several times before being decommissioned.

Mission Duration

To ensure that there is enough time for the required water to be harvested, in the analysis the total mission duration was set to one year. A sample mission to one of the Apollo asteroids had a Terra-asteroid transit of 160 days, 15 days for landing site identification and actual landing, 30 days for mining, and a final 160 for transit back to Terra.

Robot starts in LEO with 75 kg of water propellant and zero kg in the water cargo tank. The 75 kg is burnt for the Terra-Asteroid trajectory. At the asteroid, 150 kg of propellant is harvested, plus 100 kg of water cargo. 75 kg of propellant is burnt for the Asteroid-Terra return home trajectory. Robot arrives at LEO with 75 kg of propellant left and 100 kg of water cargo. The cargo is unloaded. The propellant tanks have enough for the next mission, without having to lug it up out of Terra's gravity well.


The top requirement is for the spacecraft to have a mass of 500 kg or less. The major payload systems are microwave system, drilling system, anchoring system, and prospecting system.

Microwave System

The report estimates an extraction rate of 2 watt-hours per gram of water extracted. The extractor can handle a hole up to 1 meter deep. The system has to harvest 250 kg of water in 15 net operational days (30 day mission with sun occulted 50% of the time). 200 W solid-state amplifier power supplies and 7 microwave probes. The system requires 1,400 watts.

Drilling System

Since C-type asteroids are composed of materials about as strong as plaster or limestone, off-the-shelf drills can be used. The mechanical seals will have to be augmented because regolith is horribly abrasive. A 1 meter long drill can easily fit the payload envelope. The drill will be outfitted with logging instruments to record data about the rock layers. The drill will also be modified to allow insertion of the microwave system.

Anchoring System

The anchor has to combat all the various forces and torques caused by drilling operations (about 100 Newtons). And be reliably released when it is time to return home. Since C-type asteroids are rocky, microspine grippers might be a solution.

Prospecting System

Optical sensors identify asteroid spin rates and size, radar determines the 3-D shape, infrared telescopes determine albedo, thermal-IR images and near-IR spectrometers estimates geology and thermo-physical properties to detect organic and hydrated materials.

Spacecraft Bus


Propulsion system should be capable of using water propellant. The image shows a water electrolysis thruster develped by Tethers Unlimited, with a specific impulse of around 300 seconds and a thrust of about 1 Newton.

To satisfy requirement #10, five kilograms is allocated for a small ion drive for use as back up. This allows the robot to limp home in case of emergency or failure of the main propulsion system.

Guidance, Navigation and Control

Robot has to be capable of orbit insertion, acquision, nomimal operation, prospecting, slew, contingency, landing, and docking.

A standard Attitude and Orbit Control Systems (AOCS) suite can be used. 1x Inertial Measruement Unit, 3x Star Trackers, 3x Reaction Wheels, 3x Sun Sensors, 1x Propulsion Control Systems, 2x Wide Angle Cameras, and 2x Altimeters.


X Band Satellite Communication, with a high gain antenna, a medium gain antenna, and two low gain antennas.

Mass Budget

The 33.5 kg of power system includes 9.5 m2 of solar arrays.

Power Budget

The main budget item is power for the microwave probes. The mining period is 30 days, of which half the time the solar power arrays will be in shadow and proving no power (i.e., 15 effective mining days). In 15 days the microwave system has to harvest 250 kg of water. The seven microwave probes require a total of 1,400 watts. Since the attitude control and propulsion system are non active while anchored to asteroid, and thermal control is only needed half the time, the maximum power requirement of the microwave system is 2,150 watts.

Spacecraft Cost

Economic Return Analysis

The cost of additional buses and payloads will go down via the economies of scale and mass production. It is assumed that one SpaceX Falcon Heavy can boost 144 of these robots in one launch, but it might be cheaper to "rideshare" with other SpaceX clients. Rideshare is cheaper until the cost per mining robot falls under $1.344 million US, at that point it is cheaper to buy an entire 144 unit launch.

In the graphs above, the dashed black line represents the spacecraft cost, including developement, construction, launch and annual operations cost. Shadowed regions indicate 95% confidence intervals. Revenue from sale and useage of mined water is show for LEO (blue line), GTO (orange line), GSO (green line), and Cis-lunar space (red line).

When one of the colored lines rises above the black spacecraft cost line, that is the year when the operation breaks even, and starts turning a profit. So it is possible for a fleet of 400 mining spacecraft to break even after about six years of operation.

Phobos Fuel Plant


The Phobos plant concept is sized to obtain 600 tonnes per year (t/yr) of water from rock and soil. The weak gravity of Phobos presents significant challenges but mining operations may prove more efficient than typical terrestrial ones. The shape and reflectivity of Phobos and Deimos suggest that they may be similar to carbonaceous chondritic asteroids. If so, they could consist of up to 20 percent water. The Phobos propellant plant design assumes a 5 percent water content and is based on a rock-penetrating prototype device that was developed at the Los Alamos National Laboratory. Laboratory and field tests with this prototype indicate that it is effective with most types and conditions of rock and soil. The plant, depicted in figure 2.4.6-4, uses a rock melter configured as a coring device. An impermeable glasslike lining forms in place around the borehole during penetration and seals in the released volatiles so that they do not escape into the surrounding porous rock. The released volatiles will probably contain such impurities as carbon monoxide, carbon dioxide, and hydrogen sulfide. Gross separation occurs when condensing water from the gases is emitted from the borehole. Absorption filters further purify the water which is then dissociated by electrolysis. The resulting oxygen and hydrogen are liquefied and stored. Between boring operations the plant makes short movements to new bore sites. This is accomplished by using legs with end-effectors after raising the plant with hydraulic jacks. The mass of a plant that extracts 600 t/yr of water is estimated at about 86 t with a power requirement of about 1067 kWe. The mass estimates include a self-contained nuclear power supply (20t), radiation shielding, and habitat for crew (20t).


Robot Asteroid Prospector

This is from NIAC 2012 Phase I Cohen Robotic Asteroid Prospector Final Report and Asteroid Mining AIAA-2013-5304. The concept later evolved into the Apis Honey Bee.

The study was to determine the feasibility of mining asteroids. The Robotic Asteroid Prospector (RAP) is an autonomous vehicle that can harvest water from asteroids. Keeping in mind that for space industsrialization, water is the most valuable thing in the universe. Water that is outside of Terra's gravity well, of course. Later, more advanced models can smelt and purify the non-water part of the asteroids to harvest other elements.

It has a similar function to a Kuck Mosquito, obtaining water from asteroids. Except the Kuck sticks a little stinger into the asteroid to suck out water, while the RAP swallows small asteroids whole and slices them into gravel with death rays.

RAP Delta V Budget
ManeuverDelta V
Terra Departure3.50Based on LEO departure to account for initial deployment. Excess Delta V can be applied to subsequent maneuvers.
Asteroid Arrival1.25
Asteroid Departure1.35Propellant for this maneuver and Terra Arrival can be provided by water mined from the asteroid
Terra Arrival2.50Does not include use of Lunar Gravity assist to reduce Delta V requirements

Mission start and end at one of the Earth-Moon Lagrange points. The problem of long synodic periods between Hohmann launch windows for Earth — Near Earth Asteroids (NEAs) is ameliorated by using gravitational swing-bys of Venus and Mars. This not only shortens the delay between launch windows, it also reduces the mission delta-V. The cost can be reduced if water reaction mass can be scraped up from the Lunar poles and delivered to the RAP, instead of the insane expense of hauling it up Terra's gravity well. Once the RAP program goes into full production there will be plenty of orbital water available for future missions.

Propulsion is by solar moth using water as reaction mass. This allows in-situ resource utilization, that is, it can refill its remass tanks at the asteroid. Water is also pleasingly dense and non-cryogenic, unlike that liquid hydrogen with its annoying low density and requirement for cryogenic coolers to prevent the blasted stuff from boiling away.

Since the solar moth's "fuel" is sunlight, it will not run out of that for billions of years.

The study figures a solar moth using water remass can have about the same specific impulse of a chemical engine (I guess they mean about 450 seconds, an exhaust velocity of around 4,400 m/s). But with the advantage of in-situ replenishing its remass tanks, no cryogenic coolers needed, and the ability to use tanks that are smaller in radius than King Kong's testicles.

The RAP has two huge inflatable solar mirrors, for three reasons:

  1. Sunlight as fuel for the solar moth engine, to heat the water propellant
  2. Intense beams of sunlight to chop up the target asteroid into chunks and process to extract water
  3. Solar energy to run a Stirling cycle engine, producing one megawatt of electrical power

Each of the two mirrors are 10 meters in radius for a total surface area of about 628 square meters.

The RAP is built around a graphite composite spinal truss with triangular cross section, 40 meters long and three meters wide. The fore end has the mining equipment inside the asteroid containment vessel. The aft has the solar moth engine and propellant tanks, flanked by the two solar mirrors. The center has the tanks to store the harvested water, and other subsystems. The truss is open in the center, to allow a clear path for the intense solar beams to be directed from the two mirrors into the containment chamber.

As the RAP approaches a likely-looking asteroid, it will deploy a flock of Asteroid Reconnaissance Probes (ARProbes). These will collect samples of the asteroid from various locations and return them for analysis. The probable water content of the entire asteroid will be calculated, to determine if it is worth mining or not.

Assuming it is, what comes next depends upon the asteroid's diameter. If it is less than 25 meters in diameter, the RAP will swallow it with the containment chamber and process it with solar beams. If it is larger a swarm of Spider mining robots will be dispatched. Early model spiders will transport chunks of asteroid to RAP for processing. Late model spiders can process asteroid bits in situ, and transport the water back to RAP.

Asteroid water comes in two forms: free water and bound water. Free water is basically ice, and can be extracted by moderately heating the asteroidal material and allowing the water vapor to condense on a cold finger. Bound water is in the form of hydrated chemicals, and needs more work to extract. Meaning you have to intensely heat the stuff to a whopping 500°C.

Harvested water is stored in the central tanks, and the excess is used to top-off the remass tanks. When the RAP has a full load, and the Hohmann launch window arrives, it departs for Terra. The pictured model of RAP carries a payload of 150 metric tons of water.

Asteroid Reconnaissance Probes (ARProbes)



APIS (Asteroid Provided In-Situ Supplies)

Total cost of planned human exploration missions is strongly driven by the need to launch large quantities of rocket propellant, drinking water, oxygen, and radiation shielding. If plentifully-available in cis-lunar space, water could be used directly as propellant in Solar Thermal Rockets (STRs) to provide inexpensive transportation. The lunar surface has been proposed as a source of such water, but independent analysis of Lunar ISRU suggests that it would not be cost effective due to the Size, Weight, Power, and Cost (SWAP-C) of ISRU equipment, the large round trip delta-V to get to the lunar surface, and the logistical issues of working there. Likewise, a technical publication regardingn asteroid mining by a NIAC-funded team recently concluded that they “could not find any scenario for a realistic commercial economic return from such a mission.”

We understand why past attempts have failed and we offer an innovative new mission concept called Apis. Apis harvests and returns up to 100 tonnes of water from a near Earth asteroid using only a single Falcon 9 v1.1 launch. Apis is based on a major new patents pending innovation called "Optical Mining" that we are proposing here for the first time. Optical mining is a novel approach to excavating and processing asteroid materials in which highly concentrated sunlight is used to drill holes, excavate, disrupt, and shape an asteroid while the asteroid is inclosed in a containment bag. Optical mining is enabled by advanced anidolic optics that have thus far not been considered for ISRU applications. Apis further combines the mid-TRL technologies of thin-film inflatable structures and water solar thermal propulsion with an innovative new TRL-1 solar thermal oven technology to extract water from a volatile-rich asteroid.

APIS mission operations start with a Falcon 9 V1.1 or equivalent launch to a low C3 ARM-like but volatile-rich NEO. Once at the target, APIS uses an inflatable capture system similar to that proposed for ARM, but fabricated from high temperature material and designed to fully enclose the target. After the asteroid has been encapsulated and the system de-spun, an inflatable solar concentrator in an advanced non-imaging configuration, provides direct solar-thermal energy through Winston Cones and light tubes to the asteroid surface. This heat is used to excavate the asteroid and force the water to outgas into the enclosing bag at a tenth to a hundredth of one percent of normal atmospheric pressure. The outgassing water is cryopumped at modest temperature into a passively-cooled water storage bag and stored as solid ice. After several months of collection, up to 120MT of water can be stored in this manner. Using solar thermal propulsion with some of the water as the propellant, the APIS system returns the harvested water to Lunar Distant Retrograde Orbit (LDRO) where it can support a far more affordable program of human exploration of cis-lunar space. The presence of large quantities of water in cis-lunar space cost-effectively supplied from asteroids will profoundly benefit HEOMD missions.

Apis Honey Bee

In the science-fiction novel Delta-V, the mining robots are APIS™ and Honey Bee™ designs created by the real-world TransAstra Corporation, and used in the novel by permission. APIS stands for Asteroid Provided In-situ Supplies. It is a pun on "apis" which is the genus that includes the species honeybee (because like bees Apis efficiently gathers and returns useful resources and then utilizes those resources to perform useful work). A PDF report with more detail about the Honey Bees is available here.

The problem is that asteroids such as Ryugu are more like a pile of gravel in free fall than it is a solid lump of rock. So if you used jack-hammers or explosives you'd just scatter the gravel all over the solar system. Then comes the problem of refining the blasted stuff.

Honey Bees use optical mining, bagging rocks in large sacks and using beams of concentrated sunlight to spall the rock into tiny pieces. Ryugu's orbit has a perihelion of 0.9633 AU and an aphelion of 1.4159 AU. So the solar flux varies from 1.08 to 0.5 that of Terra, or from 1.48 to 0.683 kilowatts per square meter. Each Honey Bee has a pair of 7.5 m radius parabolic mirrors. Therefore each can gather up to 382 to 242 kilowatts of sunlight to spall the ore.

The ship carries drone robots that look like three-legged spiders, with the legs being 18 meters long. These are based on technology created for NASA’s canceled Asteroid Redirect Mission. They walk around on Ryugu's surface looking for likely bolders up to 10 meters in diameter possessing surface spectra of useful elements. When one is found, the drone stradles the bolder with its legs, drills into it with small mandible-like arms, then pushes off Ryugu. Once it has the bolder off Ryugu's surface, it leaves it there and returns to Ryugu to prospect some more.

A Honey Bee then rendezvous with the bolder. It opens up a large bag and wraps it around the bolder. It then focuses its twin parabolic mirrors on the Sun, and directs the beam on the bagged bolder. Frozen volatile ices are vaporized. The vapors are prevented from escaping by the bag. A cold trap condenses the volatiles in a side pouch. The process of vaporizing embedded ice spalls the surface of the bolder into tiny gravel. Eventually the entire bolder has been reduced to a form suitable for the ship's refinery to work on. All the volatile ices have been extracted, but the volatiles that are chemicaly bound in minerals (the "hydrates") are still there.

The ore is taken out of the Honey Bee's bag and put into the spacecraft refinery's reaction chamber. First the refinery heats the gravel to 500°C, causing the hydrates to release their volatiles. This is mostly water vapor, but also includes ammonia, carbon monoxide, nitrogen, methane, hydrogen cyanide, and hydrogen sulfide. These are all valuable chemicals, especially the water. The reaction chamber is spun like a washing machine to condense the volatiles into a liquid and to get them out of the chamber. This liquid is piped into storage for later purification. There hydrogen peroxide and postassium permanganate is used to oxidize out the non-water chemicals, leaving pure water. The water can be used as is, or cracked into hydrogen and oxygen. Hydrogen peroxide and postassium permanganate reagents can be synthesised from asteroid elements.

By this stage all the volatiles in ices and volatiles in hydrates have been extracted. There remains some more stubborn volatiles.

The remaining rock in the reaction chamber now undergoes "benefication", which means concentrating the valuable stuff by throwing away the worthless stuff. This process also extracts the more stubborn valueable volatiles. The first step is to pressurize the reaction chamber with pure hydrogen and heated to 800°C. Stubborn volatiles such as hydrogen, carbon dioxide, sulfur, nitrogen, hydrocarbons, chlorine, sulfuric acid, hydrochloric acid, and assorted amino acids are extracted. These are also spun out from the chamber and stored for later filtration.

At this point the ore in the reaction chamber has had its mass reduced by about half because all the volatiles have been extracted. What remains is the involatile residue. About a third of the residue is valuable iron-nickel-cobalt alloy. This is now purified by an acid leach, which removes everything except the alloy and the silicates. Acid is injected into the chamber, causing a furious chemical reaction. The chamber is spun again to remove the acid and the impurities: phosphorus, sodium, potassium calcium, and magnesium. They are called "impurities" but all are useful elements, they are captured and stored. The acids used in the leach can be synthesised from elements obtained earlier in the process so this is sustainable.

The remainder is iron-nickel-cobalt alloy plus silicates. On Terra this would be purified by smelting in a furnace, but that's a very bad idea in a spacecraft. So an alternate method is used. The idea is to separate the iron-nickel-cobalt alloy into its component elements by successive gasification. The chamber is heated to 100°C, carbon monoxide is injected, and the pressure raised to two atmospheres. Nickel reacts first combining with four carbon monoxide molecules to form nickel tetracarbonyl gas (very toxic). This is removed by spinning the chamber and stored; leaving the iron, cobalt, and silicates. Next the pressure is increased. Now the iron reacts with five carbon monoxide molecules to become iron pentacarbonyl gas (also toxic). It too is spun out of the chamber and stored; leaving the cobalt and the silicates. Finally the chamber temperature is increased to 200°C and the pressure increased to 10 atmospheres. Now the cobalt combines with eight carbon monoxide molecules to form dicobalt octacarbonyl gas (yes, this is toxic too). It is also spun out and stored. At room temperature and pressure the stored nickel and iron carbonyls condense into liquids, which makes them easier to handle (easier than handling red-hot gas at any rate). The stored cobalt carbonyl becomes a powder, but can be turned back into a gas by heating it to a modest 52°C.

The bolder has now been rendered down into valuable water, iron, nickel, and colbalt; plus other assorted chemicals.

What's left is silicate residue, basically sand. The worthless stuff. It currently isn't useful for anything other than bulk radiation shielding. But in the future it may be used to synthesize silicon or glass. And later still there may be a method invented that can economically extract the tiny amount of platinum group metals.


This is from Rig for Mining Asteroids (2007)

The primary problem addressed by this design is the sad fact that chondrite asteroids are more like a cloud of gravel flying in close formation than they are like large rocks. How do you mine something with the consistency of 50 meters of corn flakes?

The NeoMiner's solution is landing feet with huge augers to anchor the miner to the asteroid's surface. The augers are pushed into the surface by auxiliary rocket thruster "pile-drivers" mounted on the top of the landing legs.

The mining drill uses microwave beams to blast the asteroid's surface into sand-grain sized bits, which are then scooped up and loaded into a drone cargo hoppers. When full the hoppers deliver their loads of ore to the orbiting Hub space station, then fly back to the NeoMiner to be filled again.

The crewed Hub space station assists one or more NeoMiners, supplying them with microwaved beamed power, refining the ore, and repairing them if any are damaged or trapped. They will use Robonauts instead of crewed EVAs because of space radiation. Or radiation-hardened EVA pods.

The NeoMiner is designed to harvest asteroids with the following characteristics:

  • Near Earth Asteroid
  • A chondrite asteroid, i.e.; rock that never went through melting and subsequent crystallization and metamorphosis, with lightly compacted "chondrules" of various chemical compositions. Which is pretty much most near Earth asteroids.
  • Very low gravity / escape velocity
  • Slow rotation of around 15 hours
  • Composition is "a floating blob of rubble"
  • Volatile ices mixed in are a bonus, not a problem


The NeoMiner uses microwave electrothermal thrusters (MET). These utilize microwave chambers to turn water propellant into steam, producing thrust. Fantastic exhaust velocity of 10,000 m/s or so, but with a feeble thrust of around 30 N. High exhaust velocity coupled with low thrust is sadly typical. But when propellant is in short supply, METs are a smart choice.

The base of the NeoMiner has the four main microwave thrusters. These are used to propel the miner to new asteroid mining sites and to brake the miner to a halt while quote "landing" unquote. As noted before with such laughably low asteroid gravity, the operation is more like a free-fall rendezvous than it is a landing.

The top of each landing leg has a microwave thruster aimed upward. These act as jackhammers or pile drivers, to drive the landing legs downward into the surface. This assists the anchoring augurs in the feet of the landing legs.

When the NeoMiner moves to another location, the augers are reversed. This pushes the miner upward and assists the main thrusters.


The NeoMiner has a small solar cell array. These supply modest amounts of solar power for housekeeping operations, gathering the miserable thin gruel of sunlight that reaches the asteroid belt (a pathetic 18% of the solar power density available in Terra orbit). Of course NeoMiners operating on Near Earth Asteroids would have access to 100% of Terra solar power density.

For operating the microwave bore-head and other energy intensive operations, the NeoMiner has a flower-petal-like microwave rectenna. This is fed from the orbiting Hub space station, which has freaking ginormous solar arrays and a microwave power transmitter. This allows the NeoMiner to have reduced penalty mass and improved rocket performance due to the magic of beamed power. The Hub can get away with this since it is not expected to have to move much. At least not as much as the flock of NeoMiners it tends to.


The drill-head contains a paired array of magnetrons which generate intense bursts of microwaves. The magnetrons tune in various frequencies which resonate with the various chondrite materials and thereby shatter the whole matrix of the rock. This shatters the surface regolith into fragments the size of sand, i.e., single chondrules and smaller. The granulated material has the high-tech ultra-scientific name "grits."

Another reason to use microwaves is they can be tuned so as to fracture volatile ices into small fragments. As opposed to flash-heating the ices into high-temperature gas, resulting in an explosion blowing the NeoMiner to smithereens. Or at least vaporizing the valuable volatiles causing them to escape into space.

Behind the microwave array is an alternating pair of helical ramps. These ramps gouge up the newly formed grits, moving the grits into two vestibules higher up in the elevator tube. Each vestibule has an Archimedean screw which transports the grits up to the top of the elevator tube. There a secondary screw pushes the grits horizontally into the hopper drone.

Blasting the regolith into grits helps ensure that the digging process does not exert mechanical force on the NeoMiner. Such force could pull the blasted thing free of the asteroid, augers or no.

Depending upon the asteroid, volatile ices may be mixed in the grits. These can be separated in the elevator tube according to temperature and pressure, and stored separately from the grits. It would be quite useful if the NeoMiner can extract liquid water of sufficient purity to refill its propellant tanks.

The NeoMiner can only accommodate a bore of limited length. Once it has drilled as deep as it can, the NeoMiner will have to move over a meter or so to a new drill site. There is a concern that a pattern of bore holes could destabilize the asteroid surface, with the boreholes closing up with shifting rubble. But perhaps drilling into closed up bore holes will not be a problem. This will have to be studied.


There are basically three options for mining:

  • Scoop up raw asteroid material and haul it back to Terra for refining. Material can be hauled in cargo rockets, or packaged into canisters and flung into a transfer orbit (1.3 years transit time) by a huge mass driver. Said mass driver will be closely watched by the Spaceguard with an itchy trigger finger. A mis-aimed canister could do severe damage to a space station, lunar base, or Terran city.
  • Process the raw asteroid material on-site and haul the refined material back to Terra. This has the advantage of only expending delta-V to transport valuable stuff and not worthless rock. The disadvantage is you have to transport the refinery to the asteroid.

    You might have a mobile refinery, which is a refinery with built-in rockets (probably a mass driver, since it can use rocks and dirt for propellant).

  • Haul the entire freaking asteroid to a safe orbit around Terra or Luna.

I'm sure I don't have to point out that entrepreneurs will see business opportunities in the above options. Right off the bat it would probably pay to invest in a mobile or immobile ore refineries. Immobile refineries would be located at strategic spots in the belt, and refine ore brought in by independent rock-rats for a small or not-so small fee. Larger rock-rat strikes would have potential value enough to cover the cost of chartering a mobile refinery to make the journey and do the processing on site. Ore transport services is also a lucrative opportunity, either with a fleet of spacecraft or stationary mass driver cargo launchers.


(ed note: part 1 here)

  The crushed ore is heated to extract volatiles, using temperature steps to isolate specific fluids. Those are drawn off for cryogenic processing. Water is either frozen for storage or electrolyzed for further use. This needs a fairly simple solar reflector, vacuum pump and a loading mechanism with a decent seal. I prefer a cylinder with doors at either end and an internal auger; a batch can be fed in by the grinder and then fed out by the oven's auger. This section needs to handle temps up to 1000 °C with normal operating temp of perhaps 600 °C; this is within the range of stainless steel and fused silica (quartz glass). I will assume 600kg for this; most of that is the steel and quartz body but a substantial amount is for the vacuum pump and insulation. The solar reflector has trivial mass even accounting for pointing.

 Next, the stabilized ore is separated. Magnetic rakes can pull out anything ferromagnetic; some very high-nickel nodules might be missed. Individual mineral grains could be sorted by electrostatics or fragmentation energy or other means to be developed. This would be an excellent opportunity to test a variety of methods. The goal is to produce at least 90% concentration of each individual mineral so each type can be processed efficiently down the line. I will assume five industry-provided modules with a maximum mass of 200kg each.

 Each mineral type benefits from a specific process. Nickel-iron can be extracted with the carbonyl process at reasonable temperatures and high purity. Metal oxides can be reduced with hydrogen (my objections to this method on the lunar surface do not hold weight in this particular application). Oxides in general can be electrolyzed in solid or liquid form. There are other chemical processes that can be used; in particular, any native carbon can be burned off into CO2 as process heat for other steps and then later reduced back to C for compact shipping. As a lower-energy alternative it can be compressed and bottled as CO2, and an intermediate option is to form solid CO2. Since each approach will be different, I will again assume five industry-provided modules of 300kg each. I also assume one water purification module (100kg) and assume that the cryogenic plant can isolate the remaining gases. There are also those volatile compounds at or above water's boiling point (such as sulfur); these can be isolated in a separate module of 100kg.

 Speaking of, one of the main end products of this endeavor is liquid oxygen. In the process of making LOX most other gases can be isolated at fairly high purity and stored as compressed gas or liquids. Mass depends on throughput, but let's assume 1 ton of equipment; that allows for intermediate purification steps and extras like dry ice production.

 Each process requires electrical power. We assign 10kW and assume an alpha of 10kg/kW (Encore 3-junction cells, EOL) or 100kg of panels. Power conversion, emergency battery backup, pointing and distribution eat about three times that, so call it 400kg for the power center.

 Storage requirements depend on the products. That in turn depends strongly on the type. Chondrites are composed of calcium-aluminum inclusions, free metal nodules, chondrules and matrix. CAI's are full of calcium and aluminum oxides with traces of other light metals. Free metal nodules are iron (72-93%) and nickel (5-25%) with about 2% cobalt and trace amounts of platinum group metals and other siderophiles. Matrix is ice, other volatiles, iron sulfides, salts, magnesium oxides and silicates, carbon polymers, organic compounds, presolar grains, glass fragments and other complex bits.

 For a CI that could be about 95% matrix, 5% chondrules and tiny fractions of CAI and free metal. That's 20% water, 25% iron (as oxides), 0.01% free metal, perhaps 2.4% carbon (as complex compounds) and the rest is mostly magnesium silicates.
 Other types might be closer to 5-10% water, 2-3% free metal, 10-20% total iron, 10% non-water oxygen and 1-3% carbon. I will use the high end of these numbers to spec storage requirements.

Using 1000 tons as the upper size of the captured asteroid that's 100 tons of water, 224 tons of iron, 100 tons of oxygen, 30 tons of carbon, 4.5 tons of nickel, 600kg of cobalt and a few kg of platinum-group metals and rare earths. The remaining 540 tons is as magnesium silicates which can be processed further for more oxygen, silicon and to extract some other trace elements. Magnesium by itself may find some use but as stone it is useful for radiation shielding.

I assume the nickel is stored as tetracarbonyl (density 1.32g/cc, 34%Ni by mass, mp -17°C, bp 43°C), requiring 10.03m­³ of low-pressure, controlled temp storage. (Also requires 8.74t CO or 3.75t C + 5t O.) It could instead be stored in bags of fine powder, bulk density about 2.6g/cc, 1.73m³ of bulk storage. Should only be a few kg (4.5) of bags.
The iron can also be stored as pentacarbonyl (density 1.45g/cc, 28.5%Fe by mass, mp -21°C, bp 103°C), requiring 542m³ of low-pressure, controlled temp storage. (Also requires 562t CO or 241t C + 321t O.) It could preferably be stored in bags of fine powder, bulk density about 2.6g/cc, 86.2m³ of bulk storage. Should be a few hundred kg (224) of bags.
The water can be frozen into blocks (density 0.93g/cc) and sealed in aluminized mylar wrap for very little mass. It could also be carefully frozen inside tanks, avoiding overpressure; this would take 108m³. With a tank fraction of 1% that's 1 ton of storage tanks.
The oxygen is stored as a cryogenic liquid (density 1.14g/cc, pressure ~25 bar, temperature 90K), requiring 87.8m³ of high-pressure cryogenic tanks. With a tank fraction of 10% that's 10 tons of storage tanks.
 The carbon and other metals can be bulk-bagged for a few kg (~31) of bags.
 The remaining slag can be bulk-bagged for 540kg.

As a general rule I'm using 10% for high-pressure tanks, 1% for low-pressure tanks and 0.1% for bags.

From EARLY ASTEROID MINING by Chris Wolfe (2015)

(ed note: This is my paraphrasing quotes from the novel. Yes, it is fiction but the author did his homework. The list of NASA scientists and rocketry experts in the novel's acknowledgements is quite extensive. The paraphrasing appears elsewhere in this website, in the section about the Konstantin Asteroid Miner.)

The ore is taken out of the Honey Bee's bag and put into the spacecraft refinery's reaction chamber. First the refinery heats the gravel to 500°C, causing the hydrates to release their volatiles. This is mostly water vapor, but also includes ammonia, carbon monoxide, nitrogen, methane, hydrogen cyanide, and hydrogen sulfide. These are all valuable chemicals, especially the water. The reaction chamber is spun like a washing machine to condense the volatiles into a liquid and to get them out of the chamber. This liquid is piped into storage for later purification. There hydrogen peroxide and postassium permanganate is used to oxidize out the non-water chemicals, leaving pure water. The water can be used as is, or cracked into hydrogen and oxygen. Hydrogen peroxide and postassium permanganate reagents can be synthesised from asteroid elements.

By this stage all the volatiles in ices and volatiles in hydrates have been extracted. There remains some more stubborn volatiles.

The remaining rock in the reaction chamber now undergoes "benefication", which means concentrating the valuable stuff by throwing away the worthless stuff. This process also extracts the more stubborn valueable volatiles. The first step is to pressurize the reaction chamber with pure hydrogen and heated to 800°C. Stubborn volatiles such as hydrogen, carbon dioxide, sulfur, nitrogen, hydrocarbons, chlorine, sulfuric acid, hydrochloric acid, and assorted amino acids are extracted. These are also spun out from the chamber and stored for later filtration.

At this point the ore in the reaction chamber has had its mass reduced by about half because all the volatiles have been extracted. What remains is the involatile residue. About a third of the residue is valuable iron-nickel-cobalt alloy. This is now purified by an acid leach, which removes everything except the alloy and the silicates. Acid is injected into the chamber, causing a furious chemical reaction. The chamber is spun again to remove the acid and the impurities: phosphorus, sodium, potassium calcium, and magnesium. They are called "impurities" but all are useful elements, they are captured and stored. The acids used in the leach can be synthesised from elements obtained earlier in the process so this is sustainable.

The remainder is iron-nickel-cobalt alloy plus silicates. On Terra this would be purified by smelting in a furnace, but that's a very bad idea in a spacecraft. So an alternate method is used. The idea is to separate the iron-nickel-cobalt alloy into its component elements by successive gasification. The chamber is heated to 100°C, carbon monoxide is injected, and the pressure raised to two atmospheres. Nickel reacts first combining with four carbon monoxide molecules to form nickel tetracarbonyl gas (very toxic). This is removed by spinning the chamber and stored; leaving the iron, cobalt, and silicates. Next the pressure is increased. Now the iron reacts with five carbon monoxide molecules to become iron pentacarbonyl gas (also toxic). It too is spun out of the chamber and stored; leaving the cobalt and the silicates. Finally the chamber temperature is increased to 200°C and the pressure increased to 10 atmospheres. Now the cobalt combines with eight carbon monoxide molecules to form dicobalt octacarbonyl gas (yes, this is toxic too). It is also spun out and stored. At room temperature and pressure the stored nickel and iron carbonyls condense into liquids, which makes them easier to handle (easier than handling red-hot gas at any rate). The stored cobalt carbonyl becomes a powder, but can be turned back into a gas by heating it to a modest 52°C.

The bolder has now been rendered down into valuable water, iron, nickel, and colbalt; plus other assorted chemicals.

What's left is silicate residue, basically sand. The worthless stuff. It currently isn't useful for anything other than bulk radiation shielding. But in the future it may be used to synthesize silicon or glass. And later still there may be a method invented that can economically extract the tiny amount of platinum group metals.

From DELTA-V by Daniel Suarez (2019)

REFINERY Two was only slightly prettier than a rock, but it did come welcome—that k-plus wide sooty ring that you only caught sight of on camera—and most to Bird’s knowledge were eager to see it, and did turn the optics on, long before it was regulation that you had to get visual contact. There she hung, magnified in the long lens, spinning with a manic vengeance, with her masts stuck up like spindles and her stationary mast surfaces bristling with knobby bits that were pushers and tenders, and shuttles from the Shepherds and such. A few, hardly more than ten or so at any one time, counting company rigs waiting crew change, were ships a lot like Trinidad, a whole lot like Trinidad, if you took plan B on your outfitting, and opted for green in the shower.

A lot of the fitting inside Refinery Two was a lot like Trinidad, too, except, one supposed, if you got down to corporate residence levels, and there was about the same chance of freerunners seeing that in person as getting a guided tour of the company bunker on Mimas.

Belters lived and Belters died and Refinery Two just rolled on, this big factory-hearted ring which was the only close to g-1 place miners and tenders in R2 zone ever got back to. She swallowed down what the Shepherds gathered in, she hiccuped methane and she sh*t ingots and beams and sheet and foam steel. She used her own plastics and textiles or she spat them at Mars, in this year when Jupiter was as convenient to that world as Sol Station was. But nobody knew what went to Mimas. Some said what was down there repaired itself and had more heart than any company exec—but that was rumor and you didn’t want to know. Some said it wasn’t really the ops center it was reputed to be, in case of something major going wrong at the Well: some said it was the ultimate bunker for the execs—but you didn’t say war in polite society either and you didn’t think too much about the big frame that sat out there aswarm with tenders and construction craft, a metal- spined monster that took rough shape here at the source of steel and plastics before it moved on to final rigging at Sol. You called what was going on out in the Beyond a job action or you called it a tax strike or you called it damned stupid, but if you were smart you didn’t discuss it or that ship out there and you didn’t even think about it where Mama might hear.

     Another call from Base: “Two Twenty-nine Tango Trinidad, this is ASTEX Approach Control: tugs are on intercept. Stand by the secondary decel."
     “Approach Control, this is Two Twenty-nine Tango. We copy that decel. We’re go.” He shut down his mike, yelled: “Dekker! Stand by the decel, hear me?”
     “Break his damn neck,” Ben muttered.
     There was no time for debate. They had a beam taking aim. Approach Control advised them and fired; pressure hit the sail and bodies hit the restraints—they weren’t in optimum attitude thanks to that ship coupled to them, and it was a hard shove. Dekker yelled aloud—hurt, maybe: they had him padded in and tied down with everything soft they could find, but it was no substitute.
     It went on and on. Eventually Dekker got quiet. Hope to hell that persistent nosebleed didn’t break loose again.
     “Two Twenty-nine Tango Trinidad, this is ASTEX Approach Control: do a simple uncouple with that tow.”
     “Approach Control, this is Two Twenty-nine Tango. We copy that uncouple. Fix at 29240 k to final at 1015 mps closing. O-mega.”
     Bird uncapped the button, pushed it, the clamps released with a shock through the frame, and One’er Eighty-four Zebra went free—still right up against them, 29240 k to their rendezvous with the oncoming Refinery and they were going to ride with the tow awhile, until the outlying tugs could move in and pick it off their tail.
     “Two Twenty-nine Tango Trinidad, this is ASTEX Approach Control: tugs are 20 minutes 14 seconds, mark."
     “Approach Control, this is Two Twenty-nine Tango. We copy: 20 minutes 14 seconds. No problem, tow is clear. Proceeding on that instruction.”
     “Two Twenty-nine Tango Trinidad, this is ASTEX Dock Authority, check your pressure. Will you need a line?”
     “We copy 800 mb, B dock. No line, we’re 796.”
     “Trinidad, we copy 796. Medical units standing by on dockside. Stand by life systems sample."
     “Sh*t,” Ben groaned, “they’re going to stall us on a medical. They damn well better not find some bug aboard, I’ll skin him.”
     “Won’t find any bug. Get our data up, will you?”
     They were nose to the docking mast. Trinidad shuddered and resounded as the cradle locked. She hissed a little of her air at the sampler.
     ASTEX said: “Welcome in, Trinidad. Good job. Stand by results on that sample."
     The dockside air went straight to the back of the throat and stung the sinuses, icy cold and smelling of volatiles. It tasted like ice water and oil and it cut through coats and gloves the way the clean and the cold finally cut through the stink Bird smelled in his sleep and imagined in the taste of his food. Time and again you got in from a run and the chronic sight of just one other human face, and when you looked at all the space around you and saw real live people and faces that weren’t that face—you got the sudden disconnected notion you were watching it all on vid, drifting there with only a tether and a hand-jet between you and a dizzy perspective down the mast—worse than EVAs in the deep belt, a lot dizzier. Dock monkeys kited about at all angles, checking readouts, taking samples, talking to empty air. Bird’s earpiece kept him informed about the meds inside the ship, the receipt of the manifest and customs forms at the appropriate offices—

The meds said, and the Institute taught you, some null-g effects got worse every time you went out: your bones resorbed, your kidneys picked up the calcium and made stones, and the body learned the response—snapped to it faster with practice, as it were, and Ben believed it. Science devised ways to trick gravity-evolved human systems, and you took your hormones, you spent your sleeptime in the spinner and you wore the damn stimsuit like a religion. Most of all you hoped you had good genes. They told gruesome tales of this old miner whose bones had all crumbled, and there was a guy down tending bar in helldeck who had so many plastic and metal parts he was always triggering the cops’ weapon scans. He didn’t intend to end up like that, nossir, he intended eventually to be sitting in a nice leasing office collecting 15-and-20 on two ships, free and clear of debt, and letting other poor sods get their parts replaced. He had no objection to Morrie Bird sitting in that office as vice president in charge of leases, for that matter: Bird had the people sense that could make it work, and Bird couldn’t last at mining forever: they’d already replaced both hips.

8-deck was transient and gray and lonely: you might see a handful of miners in from their runs, not to mention the beam-crews and the construction jocks and whoever else worked long stints in null; you saw the occasional Shepherds and 'driver crews, transiting to their own fancy facilities, and a noisy lot of refinery tenders and warehouse and factory workers and dock monkeys on rest-break (there were a lot of refinery operations on 8)—and sometimes, these days, some of the military in on leave—but you didn’t get anything like the flashy shops or the service you had down on helldeck. Here you kind of bounced along between floating and walk- ing, being careful how fast you got going, being careful of walls and such—your brittle bones and your diminished muscles and your head all needed to renew acquaintances with up and down—slowly, if you were smart.

The public part of 8 was all automats, even the sleeperies—no enterprising station freeshop types behind the counters, even for the minim shifts that Health & Rehab would let a stationer work on 8. It was robot territory, just stick your card in a slot and you got a sleepery room or a sandwich or the swill that passed here for bourbon whiskey: but that was all right for a start, everything was cheaper than helldeck and your whole sense of taste was off, anyway, for the first bit you got used to refinery air.

You found no luxury here that didn’t come out of an automatic dispenser, unless you were working for the company— in which case you saw a whole other class of accommodations, the adverts said: they said a whole lot better came out of the vending machines behind those doors—but Bird had never seen it. ’Driver crew and Shepherds didn’t need the waystops that miners did—if they were up here they were slumming, on a 1-hour down from some business in the mast; but generally they went straight to helldeck, where big ship officers and tech crew had cushy little clubs and free booze, and Access with all sorts of perks on the company computers.

Adverts said you could get at least a sniff of those perks, even as a miner—if you let the company own your ship and provide your basics; but that meant the company could also decide when you were too old or you didn’t fit some profile, and then you were out, goodbye and good luck, while some green fool got your ship. God help you, too, if Mama decided you weren’t prime crew on that ship, and some company-assigned prime crew got shunted out to work tender-duty for three years at a ’driver site—which effectively dumped all the relief crews back at the Refinery onto the no-perks basics, to do time-share in a plastics factory. Work for the company and you could fill in your time swabbing tanks in the chemicals division til you got too old, and then they set you down on retirement-perks and let you sweep floors in some company plant to earn your extras.

Hell, no. Not this old miner.

But a lot of years he had been coming back to 8, and he’d seen changes—or maybe he had felt livelier once upon a time. 8 these days echoed to footsteps, not to music and voices. The bright posters had all gone years ago, the month the company had gone over to paperless records-keeping. The company favored gray paint or institution green, except for pipes that came wrapped with hazard yellow and black.

You used to get the unofficial bills here too, the paste-ups that would appear overnight—saying things like TOWNEY LIES and FREE PRATT 6: MARKS—Mama hadn’t liked those in the best days, nossir, the bills that said,things like EQUAL ACCESS and the take-one flyers that used to give you the news the company wouldn’t. They’d all gone. No paper.

You still found the old barred circle, you still found PEACE and FREE EMIGRATION scratched in restroom plastic, right alongside the stuff you could figure Neanderthals must’ve carved in Stone Age. bathrooms—you found MINIM and RABRAD and SCREW THE CORP, along with other helpful suggestions in the toilets… far more frequent here than down on helldeck, he guessed because sanding down the panels in light g made a bitch of a lot of dust, and spray paint was as bad. Or maybe it was because Security didn’t come up here much and the ordinary maintenance crews were contributing to it too. So the crud and the slogans stayed in the bathrooms, not even covered by paint, while 8-deck got nastier and dirtier and showed its age like some miners he knew.

He was in a sour mood—maybe the cops, maybe Ben’s stupid chance-taking with the datacard, maybe just that he was tired of the shit and tired of feeding a company that was trying to blow itself to hell; and right now specifically because the cops had their Personals, which meant he was stuck in the stimsuit and his day-old coveralls until the cops turned his kit loose: damned if he was going to buy new knee and ankle wraps at vending machine prices.

But he did buy a bottle of aspirin, a cheap men's personals pack, and a far too expensive bottle of cologne: the hips were gone, the ankles were going, the hair was gray and thinning, but the essentials still worked and he did have hopes. He walked into the bar in the front of the ambitiously named Starbow Hotel and, with his card in the slot at the desk, punched Double and Guests Permitted.

From HEAVY TIME by C. J. Cherryh (1991)

In pre-space speculative fiction the image of the belt miner recapitulated the image of the prospectors of old. Grizzled belters in small ships, big enough to hold them, a small partnership, or perhaps a family, who would set out, hunt down a “motherlode” rock, hack the ore out of it with traditional miner’s tools loosely adapted to space, then net it up and sling it on its way to a smelter, cash-for-density.

This concept was, as you might expect, wrong in almost every respect.

To begin with the nature of the beast, ore veins are not to be found among the asteroids. Without a planet’s gravity to differentiate them, or hydrothermal processes to concentrate it into ore bodies, pay dirt tends to be evenly differentiated throughout the rock. And to call an asteroid a rock is itself generous, insofar as the majority of them1 are little more than heaps of rubble glued together with a dusting of regolith.

Thus, the smeltership.

In its modern form, the smeltership is instantly recognizable; they look as if a starship had collided head-on with one of the larger breeds of industrial plant2, and decided for whatever reason to keep on going, accompanied by their flock of parasites and the inescapable halo of dust3. From these ships, the collector drones, “spikers”, travel to nearby target asteroids and wrap them in finely woven titiridion nets, preventing the escape of fragments, then haul them back to the maw of the smeltership proper.

Behind the maw, the smeltership incorporates a maze of ore processing and smelting equipment. While in theory plasma-fountain distillation can reduce anything to its component elements, it is an inefficient process reserved only for otherwise intractable residues of ore processing. More conventional processing chains, therefore, handle the commonplace elements once the asteroids have been powdered by the initial grinding step at the back of the maw.

Meanwhile, flocks of lighters, typically drone freighters and tankers – for the volatiles driven off – attend the stern of the smeltership, collecting the ejected ingots of metal and blocks of other elements, bundling them together, and hauling them to market.

The “almost”? While the largest operators, such as Atalant Materials’ space subsidiary, Celestial Mining, operate entire fleets of fully automated smelterships, many smaller or more specialized mining interests instead contract smelterships owned and operated by independent belt miners – often, indeed, small partnerships or family outfits whose homestead-hab is permanently docked to their ship. So while incorrect in method and scale, the writers of yore did, to their credit, predict the demographics of belt mining correctly…

– A DirtsidersHistory of the Belt

  1. And, ironically, those preferred for mining. More solid asteroids have other uses, while rubble piles are generally considered only of use for mining, and thus the claim-staking fee is lower.
  2. Not the vegetative sort.
  3. Even with high-grade electrostatic traps, regolith fines get everywhere.

(ed note: Zone-refining is a technique in which a narrow region of an ingot is molten, and this molten zone is moved along the ingot. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot.)

      This is a proposed design for a solar-thermal zone refining cell. The first few would probably be delivered but the rest should be assembled using local resources.

     The body of the cell is made of magnesium oxide (magnesia). This is a fairly strong material with a tensile strength between 83 and 166 MPa, compressive strength of 830 to 1660 MPa and a melting point of 3125 K (2852 °C). It has the odd property of being transparent to infrared A and B bands (0.7 to 3 micrometers), so a substantial portion of solar energy passes right through it. One reference lists about 55% of solar energy at earth's surface is infrared; in space that ratio is likely to be higher due to the lack of water absorption. The A and B bands are a small portion of the infrared spectrum and I don't have a value for the energy fraction in this range, but the specific amounts are not important at this stage.

     The device could theoretically melt every element but tantalum, osmium, rhenium or tungsten (all over 3290 K). Finding a lot of those metals in your ore is a problem worth having. In practice the supporting equipment probably won't be able to handle anything much over perhaps 2200 K. Fortunately that doesn't rule out very many materials; molybdenum, niobium and rhodium are the main ones. This temp is just high enough for chromium, vanadium and platinum. Very nearly all useful materials are still within reach. One concern is that some elements vaporize before others melt; it may be necessary to do a high-temperature purification step in another device (or in this device with a means of extracting the gases) before proceeding to zone refining at very high temperatures.

     A zone refining device is efficient when the melt zones are small, close together and travel quickly along the charge. It is effective when the charge is very long compared to its thickness and when at least 20 zone passes occur. It is power-efficient when the melt zones are at exactly the liquidus temperature and the solid zones are at exactly the solidus temperature, but for operational reasons this requires a few degrees of swing. The goal is to eliminate as much heat loss as possible. There is a certain minimum energy required, which is because we need to deliver the heat of formation to make the material melt and then remove that same heat to make it solidify. There are practical limits on heat retention simply because the material we want to melt is in direct contact with the material we want to keep solid.

     The choice of magnesia as a wall material introduces an important method of heat loss: radiation in the upper infrared directly through the wall of the device. The solution is contained in the problem: infrared radiation can be reflected back into the charge without heating the outside of the wall.

The heat source for this device is a large solar reflector. Since the device should be long and thin a parabolic trough may be the most efficient form. However, we don't want to heat the entire length evenly; we want to heat alternating sections. That could be done using mobile reflectors between the trough and the device or by making trough sections that can change their focal point along the length of the device. It could also be done with a fixed reflector geometry that makes hotspots and then moving the entire reflector or the entire device. Since this is a batch process requiring a certain number of zone passes, let's assume the reflector is on a rail or is otherwise mobile. The device is loaded with material to refine, then heated to just below melting in a flat spot in the reflector. The active part of the reflector is a series of flat-bottomed troughs; the cylindrical flat section reflects any radiated heat from the heating zone back into itself, while the parabolic trough walls are angled to concentrate sunlight onto the heating zone. The cooling zone is above the angled parts so no sunlight is reflected into the zone. The reflector is then moved on a rack or rail or cable system until the required number of zones have passed.

     The heat sink for this device could be passive radiation. That would require modeling to make certain it is feasible, but I'd bet it could be made to work. Another, faster option would be coolant channels built into the wall of the device, with valves to control which zones are being actively cooled. This poses a challenge: what can be used as a fluid coolant at 2200 °C? Water, CO and CO2 all dissociate. Hydrogen would attack the magnesia, liberating oxygen and leaving magnesium metal in the coolant channels. Helium seems to be the only viable option. Since the system can be closed or sealed, there would not normally be any significant gas leaks; this is important because helium is exceedingly rare away from Earth. The trouble with helium is that it will migrate through the tiniest of pores. I'm not convinced a ceramic material can reliably hold high-pressure high-temperature helium, particularly in a device built in the field. Perhaps sodium or calcium vapor could be used. For now I'll assume passive radiation with a possible future model using active cooling.

     Performance numbers will require modeling. I'm not sure how I will get that done with no resources, but it's something to consider another day.

     The output of the device is a long bar of material, separated into pure elements in order of their melting points. More or less. I've had trouble finding conclusive statements that no eutectic mixtures are encountered, so if anyone has a definite reference I would appreciate it. Further processing is necessary since we do not necessarily know the exact composition of the starting material. Some kind of elemental analysis (neutron or x-ray spectrometer, mass spectrometer, etc.) is used to identify boundaries between materials; these boundaries are cut with enough margin on either side to give pure bars of metal and several impure slices from boundary layers. These slices can be added to the next charge or stockpiled for later use; rare elements will tend to accumulate in the boundary slices and at the ends of the cylinder, so over several cycles of refining these rare materials can be concentrated until there are useful quantities available.

     Bulk slices of refinery bars represent very pure materials, including semiconductor-grade silicon. These can be used to make strong alloys with precise chemical formulas and can also be used to make semiconductor devices like light-emitting diodes and photovoltaic cells. This is a reagent-free approach to pure inputs for many processes using what is available in space: dry dirt and sunlight.

from IN-SITU ZONE REFINING by Chris Wolfe (2015)

(ed note: The Rosinante asteroid L5 colony has a large solar pumped laser. They use it to zone-refine asteroid material to extract valuable elements.

Zone-refining is a technique in which a narrow region of an ingot is molten, and this molten zone is moved along the ingot. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot.)

"Right,” said Ilgen. “Now, the other thing was the tracking. I was going to come in and say: ‘The tracking will be done in the usual manner’ but, my God! The big laser is hundreds of kilometers away, and we want to control it within centimeters and move it in response to temperature changes within a few milliseconds. Routinely. Okay. If we make a collimating lens, here, it's a Fresnel lens, made out of silica—Skaskash designed it for me and made the drawing, after I told him what we needed—we slave the laser to it, and concentrate on moving the lens, and hey! No problem."

"How do you know when to move the lens?"

"We have a sensor,” said Ilgen. “It aims a tiny laser beam at the leading edge of the liquid zone, and gives a continuous—well, ten per second—analysis of the composition. Okay. From the composition, we know the melting point, right?” Cantrell nodded. “And we know the geometry and the heat input. A little stack of chips puts it all together and tells the collimator how to move. When the melting point gets a little higher, we move a little slower. I figure we can get the liquid zone as narrow as two to three centimeters—about as thin as the thickness of the target—but probably we'll run it at ten centimeters, or maybe eight, which should be no problem at all."

"This is the basic bar for refining,” said Ilgen. Cantrell had learned it all before, but he let the engineer rattle on. Things sometimes changed quite unexpectedly. “We can slip-cast it to any length we want to use. It's twelve meters wide, and maybe one, maybe two kilometers long. Whatever.” He turned the bar over. “Okay. We were going to cut it into twenty-meter segments, but with the better control, I figured we can do two-meter segments. The less distance the elements have to travel to get separated, the faster you can refine them, right?” Cantrell nodded agreement. “Cubic kilometers, you said! If you can get the raw metal in place, this baby can do you one a year! Maybe two!"

"Six months to refine a cubic kilometer of nickel-iron?” Cantrell was skeptical.

"If nothing goes wrong,” said Ilgen. “Now look at this.” He put a model of the target array on the table in front of Cantrell. “The collimating lens moves...” He pushed it across the array with his finger. As it moved, the radiation shielding went up on both sides. Cantrell slid the lens back and forth a few times.

"I see,” said Cantrell at last. “The shielding keeps the metal hot, so when the laser makes its second, third, and fourth passes, it can go faster because it doesn't have to supply as much energy."

In the council chamber, Harry Ilgen had an actual display sample, a metal bar two meters long, sitting on the table. It was cut and polished, and stained with vapor-phase reagents to show the location and amounts of the different elements.

     "This is the first sample to come off the first production run at the refinery,” said Ilgen. “It ought to be pretty typical. The purple band, 0.76 centimeters wide, is manganese. The red is nickel, 14.03 centimeters; the blue is cobalt, 1.04 centimeters; and the 182.79-centimeter orange-brown band is, of course, iron. The bright orange on the end is chromium, 0.88 centimeters.
     "Okay, so much for the major elements. Commercially, they cost more to ship than they're worth.
     "Now the thin bands at each end are something else again. The low-melting end, here, next to the manganese, is 0.035 centimeters thick. It is seventy-eight percent copper, nineteen percent tin, two percent uranium, one percent silver, and maybe point five percent gold—a little more than one hundred percent because of rounding. Okay? They are mutually soluble and haven't separated since all the bands together are so much thinner than the melted zone that swept them to this end of the bar.
     "Now, at the high-melting end of the bar, down by the chromium, are the real values. We have a layer 0.015 centimeters thick, which is mostly vanadium and tungsten, with about twenty percent platinum metals—platinum, osmium, iridium, rhodium, ruthenium, and palladium—eight percent molybdenum, and traces of niobium, tantalum, and rhenium. The palladium was carried along in solution with the platinum metals; it should be in with the chromium. Okay, this is what we've got. This is what we'll be refining. Any questions?"
     "You said a two-meter bar,” said Corporate Forziati, the representative of the minority stockholders of Rosinante, Inc. “The numbers you cited don't add up to two hundred centimeters."
     "Hey, look,” said Ilgen, “we're working with very hot metal and making cuts of finite width with a laser. The target array can handle workpieces 195 to 205 centimeters wide—two meters, not 200.000 centimeters."
     "At the hot end, what are the percentages of vanadium and tungsten?” asked Cantrell.
     "Vanadium fifty-six percent, tungsten fourteen percent,” said Ilgen.
     "You have uranium; you should have lead,” said Bogdanovitch. “Where is it?"
     "It boils out,” said Ilgen. “That was one of our problems—the frozen lead gumming up the works. We put in condensers and got most of it, but it isn't here anymore."

     "What is your throughput of metal?” asked Skaskash.
     "We're still learning,” said Ilgen, “but I'd guess that we might be refining sixteen to seventeen million tons a day once we hit our stride. About half a cubic kilometer a year, maybe."
     "How long before (asteroid) Don Quixote is worked out?” asked Marian Yashon.
     "Bailey's Ridge, the one we're working, if we went one cubic kilometer a year, would last thirty, maybe thirty-five years,” said Ilgen. “That isn't the biggest mass of metal on Don Q, either. It's just handy to the north polar boomstem."
     "How much uranium are we producing, anyway?” asked Corporate Forziati.
     "The raw metal contains about 2.8 parts per million by weight,” said Ilgen. “If we ran ten million tons, that would give us twenty-eight tons of uranium."
     "And you were talking about running sixteen or seventeen million tons a day?” asked Forziati. “For a year? What do you need it for?"
     "There are a lot of other elements,” said Cantrell. “Selling them will enrich the minority stockholders somewhat. Hopefully beyond the dreams of avarice."
     "Maybe,” said Corporate Forziati. “You could break the market, too."
     "We will do our best to be careful,” said Cantrell.

From THE PIRATES OF ROSINANTE by Alexis Gilliland (1982)

      Atlantis was still moving slowly out, away from Earth and farther from the Sun. At an acceleration of only a thousandth of a gee it would take a long time to spiral out to the Asteroid Belt, to the region where Regulo was planning to perform his next project.
     "Of course, what we'll be doing this time is just a small rehearsal for the real thing," he said to Rob, as they sat again in the big, darkened study. "I've picked out a tiny one, just a few hundred meters across. You may think it isn't worth bothering with, but I want to see if everything hangs together the way I'm expecting."
     "I agree with you. Always do a trial run." Rob looked at the other man's gaunt face. There seemed to be an urgency and a hardness there that he had never seen before. "Have you decided yet what your `real thing' will be?"
     "I fancy Lutetia. It's an asteroid that's not too far out, a good deal closer to the Sun than any of the really big ones. According to Sycorax, Lutetia is loaded with metals and big enough to be interesting."
     "What's the diameter?"
     "About a hundred and fifteen kilometers, give or take a couple."
     Rob leaned back in his chair. "And you think you can mine that?"
     Regulo grinned at his expression. "Sure." He leaned slowly across the desk and placed the palm of one hand at a point on the top of it. When he took it away, the glowing sign, THINK BIG, was revealed. "See that? You're getting there, but you have to work at it. You still let your thinking become too crowded. I told you I was going to use a new method of mining the asteroids, and I meant it. Let's get the screens working, and I'll show you what we're about."
     His voice took on its old, eager tone. "I want to see what you've been doing, and I want to show you what we've been at. You'll see why I wanted you up here. Take a look at this."

     He switched on a large holoscreen that ran from floor to ceiling on one side of the study. In it appeared a view of a small asteroid, swimming free in space. Away to one side of it Rob could see a familiar shape. He frowned.
     "That's one of my Spiders. I thought they were supposed to be out in the Belt."

(ed note: a Spider is a ultra-fast manufacturing machine. You feed in required raw material into the proboscis, and the beanstalk or whatever emerges from the spinnerets at about two hundred kilometers a day)

     "That one will be, as soon as the demonstration is finished." Regulo adjusted the control to zoom in on part of the image, and pointed at the upper part of the screen. "Now, take a look at the top of the rock there."
     "It looks like a drive unit." Rob reached over and increased the magnification a little further. "There's another one at the bottom, from the look of it."
     "Quite right. You can't see this on the image, but the whole rock has been covered with a layer of tungsten fibers. They'll hold their strength up to nearly three and a half thousand degrees. See anything else near where the Spider is hanging?"
     Rob moved the joystick and the magnified area shifted until it was centered on the dark bulk of the Spider. "I can see a housing on the surface of the rock. It looks like a power attachment, without the rest of the powersat."
     "Right again." Regulo was in his element. "We'll be hooking a powersat in position four hours from now. The connections have been set up to work with either that or a power kernel, to take electricity from the power source and distribute it around the rock. Now, one more fact and then you're on your own." Any pain that Regulo was feeling had been pushed away from his conscious thoughts. His voice was full of a huge satisfaction. "Zoom in on the Spider, and tell me what else you see."
     Rob leaned forward, moving his head from side to side to get a better look at the holo-image. "You've done something to the proboscis," he said at last. "It's been lengthened, and it has a different reflectivity. Hm. Have you changed the composition?"
     "To a high-temperature ceramic." Regulo nodded. "I ought to brush up on my knowledge of spider anatomy. In my ignorance, I've been calling it a sting. All right, we've changed the proboscis. It will take very high temperatures, and it's still flexible. Now you've seen everything, so you tell me. What game are we playing here?"

     Rob stared at the image in front of him, his imagination hyperactive. Regulo wouldn't have gone to these lengths unless he had something very real in mind. It was just a question of sorting through all the possibilities and choosing the one with the commercial slant.
     "What's the composition of this rock?" he said suddenly.
     "Metals, mostly—several different ones."
     Regulo waited expectantly. After a minute or two more, Rob nodded.
     "I see it," he said. "It all seems feasible, but I'd want to explore the details."
     "Well, man." Regulo was suddenly impatient. "Come on, tell me how you think it ought to work."

     "All right." Rob stood up and went closer to the screen. He pointed at the drives in the rock. "Let's start with these. You set them to provide equal and opposite thrusts, one on each side of the asteroid. You fire them tangential to the surface, and you use their torque to set the rock spinning fast about an axis. The faster, the better, provided that the tungsten sheath around the whole thing can take the strain."
     "No problem at all with a small rock like this. We might have more to worry about when we get to something the size of Lutetia."
     "Let's finish this one first." Rob pointed again at the image. "I'll assume you have the powersat in position by the housing there. You picked that placing so the powersat sits on the axis of rotation of the rock. It would be a messy calculation, but the principles are easy. Now you begin to feed power in to the rock, through a grid over its surface. A lot of power. For something much bigger than this, I don't think a powersat will do it. You'll need a fusion plant or a power kernel, otherwise the job will take forever."
     He squinted again at the configuration on the screen. "Are you sure that the rotation will be all right? I'd expect a stability problem. It will be difficult to keep a smooth rotation about a single axis as the shape changes. I assume you looked into that and have the answers?"
     Regulo nodded. "I cut my teeth on that sort of problem, calculating the change in mass and moments of inertia as the volatiles boil out of an asteroid during solar swing-by. We'll have small adjustments to make as we go, but I have those worked out. Keep going."

     "Alternating currents," Rob said. "Big ones, through the middle of the asteroid. When you apply those from the power source, you'll get eddy current heating inside the rock from hysteresis effects. If you put enough power into it, you'll melt the whole thing. You'll produce a spinning ball of molten metals and rock. Spinning fast. I assume you've looked at the shapes and structures for a stable rotation? You'll want a Maclaurin ellipsoid, with an axis of symmetry, rather than a Jacobi ellipsoid with three unequal axes."
     "You will indeed." Regulo's face was intent, his eyes fixed unwinkingly on Rob. "I've looked at the stability of the rotating mass. It will be all right. What next?"
     "The rotation produces an acceleration gradient inside the rotating ball. The heaviest metals will migrate to the outside, the lightest ones will be forced to lie inside and closest to the axis of spin." Rob was visualizing the ball, shaping it before him with his hands. "It's like a big centrifuge, separating out the layers of melted materials. All you need now is the final stage: the Spider. It sits out on the axis of rotation, at the opposite end from the main power source. But it has that long, specialized proboscis, so it can reach any point inside the asteroid. You insert it to the depth that you want, and draw off that layer of rock or metal. Then you extrude it directly through the Spider—I already made the modifications you asked for, to permit high-temp extrusion."
     "You did." Regulo's eyes were gleaming. "And we can do away with all that mess that we had to use for the beanstalk. Chernick and the Coal Moles was a neat idea, but it was still a patched-up solution. With direct extrusion we'll see a terrific improvement in what we can do. Give me access to Lutetia and I'll spin you a cable from here to Alpha Centauri, with any material in the asteroid. No more grubbing about for different metals. They'll come pre-sorted by density."

     He grinned at Rob's expression. "All right, maybe not Alpha Centauri. We could certainly spin a web right through the Solar System, if we can think of a good use for one."
     "I like that. A beanstalk, all the way from Mercury to Pluto." Rob was silent for a moment, chewing at his lower lip. "Won't work, though," he said at last. "You could never get it stable."
     "True enough." Regulo leaned over the desk and cut back to a full display of the asteroid. "I'm just indulging in a little random speculation. That's how everything starts, though I must admit I don't see any way of making that one work—yet. There are a couple of other things that you didn't mention about this system. How would you stop it from slowing down and stopping the rotation? You'll have frictional losses, effects of the solar magnetic field, all that sort of thing working against you."
     "After the drives are switched off? I'd expect those to be small effects, but anyway it should be easy enough to compensate for them. It won't be a perfectly homogeneous figure of revolution, even when it's melted. Stick a pulsed magnetic field on it, about the rotation axis. You won't need much torque to keep the spin rate constant."
     Regulo grunted his approval. "Where were you twenty years ago, when we were designing the Icarus solar scoop? I could have used your head on that. Most people don't seem to be able to think straight even when they have all the facts."
     "Twenty years ago? I'd just lost my first milk tooth."

     "Aye. God knows it, I'm getting old." Regulo rubbed at his lined forehead with a thin, veined hand. "Twenty years ago, to me it's like yesterday. One more thing for you to think about, then we'll pack this in and do some work on the beanstalk. From what you've seen of this so far, do you see any problems when we go to a really big one? Say, when we spin up Lutetia?"
     Rob shrugged. "Well, there's one obvious problem. You can't possibly extend the proboscis far enough to penetrate through to the center of something that big. So you'll have to mine the heavy materials on the outside first, even if that's not the way you'd prefer to do it. I can see cases where you might want to get at the lighter metals and the volatiles first."
     "I've worried about that one, too. At the moment I'm playing with the idea of zone melting, but I'm not completely happy with it." Regulo watched and waited in silence, while Rob mulled over that problem.
     "I see what you mean," Rob said at last. "You're assuming that the materials are scattered fairly uniformly through the whole body of the asteroid. That looks like a big assumption to me—unless you've checked it some other way?"
     Regulo shook his head. "The theory of formation suggests that most of the volatiles will be on the outside. I would melt just the first couple of kilometers in from the surface, and mine there first. I think the Spider could tap that deeply without much trouble."
     "And leave the middle solid until you want to melt further?" Rob looked thoughtful. "I don't have your experience on differential melting. The Spider can do it all right, that's not the issue. But I'm still not comfortable with the idea. Let me think about this for a few days and see if I come up with anything better. It's not efficient to switch the power on and off, and I would expect that zone melting will give you problems with rotational stability."

From THE WEB BETWEEN THE WORLDS by Charles Sheffield (1979)


Near Earth Objects

Martin Elvis studied access to Near Earth Objects (NEO) in his paper HOW MANY ORE-BEARING ASTEROIDS?. These might not be the richest asteroids, but at least they are closer than the asteroid belt. By definition a NEO has to be closer than 1.3 AU to Terra at some point. The required delta-V to reach an asteroid is of paramount importance but lower distance means shorter transit times. Or shorter lightspeed-lag time if you are using teleoperated mining drones.

The return delta-V is more important than the outbound delta-V. Presumably the returning spacecraft will have far more mass since the mining equipment weights less than the mined ore.

Lance A. M. Benner calculated a convenient table of outbound delta-V costs to travel by Hohmann trajectories from LEO to various NEOs (using the method explained in Earth-Approaching Asteroids as Targets for Exploration). They are in a range of 3.8 km/sec to 28.0 km/sec with a median of 6.65 km/sec.

Elvis used the convenient table to make the above graph. H is the absolute magnitude or brightness of the asteroid, which is used to estimate the diameter of the blasted thing. Telescopes can easily determine absolute magnitude of an asteroid, diameter is really hard. The higher the absolute magnitude, the lower the diameter. H = 22 is approximately 100 meters in diameter for the average asteroid albedo (0.05). H > 22 is diameter < 100 m, H < 22 is diameter > 100 m, H = 25 to 27 is about diameters from 24 to 60 meters.

Doing some calculation Elvis figured that if a mission planner would settle for 4.5 km/s missions instead of 6.65 km/s, the spacecraft could carry double or even quadrupal payloads to the NEO (compared to a 6.65 km/s mission).

It is a pity that 4.5 km/s only allows visiting a very small fraction of NEOs.

For NEOs with H>22 (smaller than 100 meters in diameter, blue curve in graph), 4.5 km/s only lets one travel to 2.5% of them (yellow line in graph). 5.7 km/s would let you travel to 25% of H>22 NEOS (orange line in graph).

For NEOs with H<22 (larger than 100 m diameter) 4.5 km/s will only let you travel to 0.1% of them (0.01 yellow-green line). 6.2 km/s will get you to 10% of them (0.1 yellow-green line).

NASA planned an asteroid sample and return mission called OSIRIS-REx. It was launched 8 September 2016. It will reach its target NEO (101955 Bennu) on August 2018.

But the valuable piece of data that Elvis was interested in was that OSIRIS-REx was sent to its destination using 5 km/sec of delta-V from an off-the-shelf Atlas V rocket. Plotting it on his graph, it said that an Atlas V could send a space probe to about 3% of all known NEOs (gold line).

Elvis sat up in his chair when he learned about SpaceX's Falcon Heavy. That monster could send a space probe off with 7 km/sec of delta-V. Which opens up access to 45% of all known NEOs, about fifteen times as many as the Atlas V. Using quite a few simplifying assumptions Elvis estimates the additional asteroids will have a total value in the ballpark of $150 billion US.

Asteroid Belt

Be aware of the simplifying assumptions. Meaning that the values here are close approximations but not exact. If you want exact you will need NASA-grade trajectory software.


  • Mission: origin planet - destination planet
  • Orbit ΔV: Orbit-to-Orbit. Delta-V cost a spacecraft has to pay for Hohmann starting in low orbit at origin and ending in low orbit at destination
  • Orbit T: Orbit-to-Orbit. Transit time for a spacecraft in a Hohmann starting and ending in low orbit around the two planets. Y=years, M=months
  • SYN: Synodic period, (long) delay between one Hohmann launch window and the next
  • ANG: Orbital phase angle between origin and destination planets at Hohmann launch window (see diagram above)
  • Insert ΔV: Delta-V cost for trans-Destination insertion burn at start of Hohmann trajectory
  • Arrive ΔV: Delta-V cost for Destination orbital insertion (arrival) burn at end of Hohmann trajectory
  • Surf ΔV: Surface-to-Surface. Delta-V total cost for lift-off from origin, Hohmann trajectory, then landing at destination
  • Rnd Orbit ΔV: Delta-V total cost for Orbital Round Trip. Start at low orbit at origin, Hohmann to low orbit at destination, then Hohmann to low orbit at origin
  • Rnd Surf ΔV: Delta-V total cost for Surface Round Trip. Lift-off from origin, Hohmann trajectory, land at destination, lift-off from destination, Hohmann trajectory, land at origin
  • Wait T: Wait Time. For round trip, after spacecraft arrives at destination, amount of time ship must wait at destination until homeward Hohmann window opens
  • Rnd T: Round Trip Time. Total time for round trip, including wait time at destination

Rock Rats


We're the atomic blasters,
The dancing wi' disaster masters,
We're the solar mirror spinners,
Bringing home the steel.

by Ken MacLeod (2005)

The standard science fiction trope of an asteroid miner is a misanthropic crazy coot Miner-Forty-Niner, in outer space. Except unlike the American West it takes lots of skill and high-tech equipment to keep a person alive in space.

In the early days the only justice will be what you can make with your six-shooter laser pistol. Later there will be Asteroid Mining Law. Much later there may be an Asteroid Revolutionary War of independence.

As previously mentioned, common nick-names for asteroid miners are rock rats, rockskippers, meteor-miners and belters (because they work in the asteroid belt).

The system will probably be roughly similar to the process as seen historically on Terra.

  1. Some lucky asteroid miner will stumble over a valuable deposit of mineral on a remote asteroid. Despite their efforts to keep it a secret, the cry will go up "Thar's Gold in them thar hills!" The gold rush is on.
  2. A wannabe rock-rat will hear this, and somehow manage to purchase a minimun set of rock-rat essential tools. Grubstakes may be involved. They go to the general area of the gold rush and start prospecting.
  3. If the novice rock-rat is very lucky, they will beat the million-to-one odds and actually find a small asteroid that has something halfway profitable. The rest will gradually go downhill, much like compulsive gamblers and for similar reasons, because asteroid mining can become a drug.
  4. The rock-rat will stake a claim on their discovery.
  5. If the rock-rat is real lucky, their claim will NOT be stolen by claim-jumpers. Polite claim-jumpers just steal the claim to the asteroid by some illegal means. Impolite claim-jumpers murder the rock-rat, steal all their gear, and then steal the claim.
  6. The miner will then either start mining operations, or sell the claim in exchange for quick cash.
  7. If the miner hires people to help work the claim, care must be taken to catch any dishonest hires who try to steal valuable ores. This is called High-grading.
  8. In some cases, the valuable discovery is not so much a flying mountain with a vein of ore, but rather a small bolder. So rather than stake a claim the rock-rat will probably haul the bolder to a place where they can sell it.
  9. The dirty little secret is that most miners went broke, very few became wealthy. The people who became wealthy were the store owners who sold things to the miners.

A couple of science fiction stories have pointed out that asteroid miners might use mining lasers to slice asteroids. The implication is that the only difference between a mining laser and a weapons-grade laser is the aiming system. This could come in handy if wage slave asteroid miners decide to force negotiations on their megacorporation bosses, or for an asteroid revolutionary war of independence. Miners also have access to other high-energy sources that can be weaponized, such as: chemical and nuclear mining explosives, large solar mirrors, and mass-drivers.

Staking A Claim

The United States had to set up a system for mining claims to handle the insanity of the California Gold Rush. Up until then California was using Mexican mining law. That gave the right to mine to the first one to discover a mineral deposit and begin mining it. Which limited the area that could be claimed by one person to a patch of ground small enough to be mined by one person. US mining law was based on prior appropriation, where the plot was granted to the first one to put it to beneficial use.

  1. Prospector discovers a valuable mineral in quantities that a "prudent man" would think worthwhile to invest time and expenses to recover
  2. Prospector marks the claim boundaries. US law specifies wooden or steel posts at least four fee tall, or stone cairns at least three feet tall. In science fiction asteroid miners generaly use radio beacons and/or blinking lights.
  3. Prospector must file a claim with both the land management agency (USFS or BLM) and the local county registrar. In Nat Schachner science fiction story, the proper agency to file a claim critically depends upon jursdiction.

The claim is now officially an unpatented claim. The prospector must now either continue mining/exploration activities on the claim or pay a fee to the land management agency once a year. Otherwise the claim becomes null and void, the land is considered abandoned.

The claim can be upgraded to a patented claim when the federal government isues the prospector a patent (deed) to the claim. To earn this the prospector has to prove to the feds that the claim contains locatable minerals that can be extracted at a profit. Once they have a patent the prospector can use the land for whatever they blasted please, just like any other real estate.

A person who tries to seize the claimed land from the prospector is a "claim jumper."


Since asteroid prospecting is a much more expensive venture than a Miner-Forty-Niner heading to California, there is an even bigger demand for wealthy individual offering "grubstakes." This is money, materials, tools, food etc. provided to a prospector in return for a share in future profits.

Obviously the more times a miner has been given a grubstake but have nothing to show for it, the bigger the share of future profits will be demanded for a new stake. And eventually no grubstake will be offered at all, since the incompetent miner obviously couldn't find gold inside Fort Knox. You will find such loser rock-rats in various bars in various miner's hells, crying drops of tears to hover in the general vicinity of their beer-bulbs. Don't go flashing any ostentatious signs of wealth in such places, or they will cluster around you and whine for a grubstake.

Equally obviously if the miner does actually strike something valuable, the person who supplied the grubstake will start watching the mining operation like a hawk to ensure that they get their fair share. Rock-rats who are caught understating their profits will find themselves in a universe of trouble.

This is also the point where the rock-rats discover they should have read all the fine print in the contract.

Occasionally you'll find the word "grubstake" used to just mean "enough money accumulated to fund a prospecting mission", without the additional "from a backer who wants shares of the profit." This means something like the rock-rat working at some dull low-paying job for a long time, and banking all they can save.


There's GOLD in them-there hills! Eheheheh!

A character who searches for mineral resources, traditionally gold.

The profession of prospector is actually quite an old one, for as soon as humans understood that there were valuable minerals to be had, some of them spent their lives looking for new supplies. But it came into its own in The Wild West, with its large tracts of unexplored land.

In particular, the California Gold Rush brought many people west to seek their fortune. (See Forty Niner for this specific incident.) After the initial gold rush was over, some miners stubbornly refused to quit the profession and spread over the Western territories. At first, gold and silver were the desired commodities, but later oil, radium and uranium became the hot items to search for. (Some would spend any money so manically after a rich haul that it raises suspicion that they wanted to get back to the profession regardless.)

The stereotypical image of the Prospector is an older man dressed in faded work garb, with a grey beard, missing teeth, a pickaxe and a trusty mule or burro. (See our page picture.) He'll be subject to intense bouts of Gold Fever, wild celebration when he does find a rich deposit, and suspicion of anyone who gets too close to his claim.

Typical plotlines include: "Claim jumpers" try to get the prospector out of the way by swindle or force to steal his claim; a dying prospector gives the protagonist a map to his lost mine; a "worthless" claim turns out to be extremely valuable because there's a different mineral than what was expected.

(ed note: see TV Trope page for list of examples)


(ed note: The good ship Rolling Stone is about to depart from Mars to travel to the asteroid belt, carrying owner Roger Stone and his family. In the belt, there is news of a uranium strike in the Hallelujah node, and the uranium rush is on. His teenage sons Castor and Pollux are absolutely full of get-rich quick schemes. Sadly they are lacking in morals.)

      Castor wet his lips. "The sand rats are offering fabulous prices just for cold-sleep space. We could carry about twenty of them, at least. And we could put them down on Ceres on the way, let them outfit there."
     (Father Roger Stone said) "Cas! I suppose you are aware that only seven out of ten cold-sleep passengers arrive alive in a long orbit?"
     "Well … they know that. That's the risk they are taking."
     Roger Stone shook his head. "We aren't going, so I won't have to find out if you are as cold-blooded as you sound. Have you ever seen a burial in space?"
     "No, sir."
     "I have. Let's hear no more about cold-sleep freight."
     Castor passed it to Pollux, who took over: "Dad, if you won't listen to us all going, do you have any objections to Cas and me going?"
     "Eh? How do you mean?"
     "As Asteroid miners, of course. We're not afraid of cold-sleep. If we haven't got a ship, that's how we would have to go."
     "Bravo!" said (grandmother ) Hazel. "I'm going with you, boys."
     "Please, Mother!" He turned to his wife. "Edith, I sometimes wonder if we brought the right twins back from the hospital."
     The boost to a cometary orbit left little margin for cargo but what there was the twins wanted to use, undeterred by their father's blunt disapproval of the passengers-in-cold-sleep idea. Their next notion was to carry full outfits for themselves for meteor mining—rocket scooter, special suits, emergency shelter, keyed radioactive claiming stakes, centrifuge speegee tester, black lights, Geiger counters, prospecting radar, portable spark spectroscope, and everything else needed to go quietly rock-happy.
     Their father said simply, "Your money?"
     "Of course. And we pay for the boost."
     "Go ahead. Go right ahead. Don't let me discourage you. Any objections from me would simply confirm your preconceptions."
     Castor was baffled by the lack of opposition. "What's the matter with it, Dad? You worried about the danger involved?"
     "Danger? Heavens, no! It's your privilege to get yourselves killed in your own way. Anyhow, I don't think you will. You're young and you're both smart, even if you don't show it sometimes, and you're both in tiptop physical condition, and I'm sure you'll know your equipment."
     "Then what is it?"
     "Nothing. For myself, I long since came to the firm conclusion that a man can do more productive work, and make more money if that is his object, by sitting down with his hands in his pockets than by any form of physical activity. Do you happen to know the average yearly income of a meteor miner?"
     "Well, no, but—"
     "Less than six hundred a year."
     "But some of them get rich!"
     "Sure they do. And some make much less than six hundred a year; that's an average, including the rich strikes. Just as a matter of curiosity, bearing in mind that most of those miners are experienced and able, what is it that you two expect to bring to this trade that will enable you to raise the yearly average? Speak up; don't be shy."
     "Doggone it, Dad, what would you ship?"

(ed note: the twins are stymied but their grandmother has an idea)

From THE ROLLING STONES by Robert Heinlein (1952)

      “But the bills do mount up," Amanda said swiftly, trying to change the subject. “I was going over the accounts earlier. We can't seem to stay ahead of the expenses."
     Fuchs made a sound somewhere between a grunt and a snort, “if you count how much we owe, we certainly are multimillionaires."
     It was a classic problem, they both knew. A prospector might find an asteroid worth hundreds of billions on paper, but the costs of mining the ores, transporting them back to the Earth/Moon region, refining them—the costs of food and fuel and air to breathe—were so high that the prospectors were almost always on the ragged edge of bankruptcy. Still they pushed on, always seeking that lode of wealth that would allow them to retire at last and live in luxury. Yet no matter how much wealth they actually found, hardly any of it stayed in their hands for long.
     And I want to take ten percent of that from them, Fuchs said to himself. But it will be worth it! They'll thank me for it, once it's done.
     “It's not like we're spendthrifts," Amanda murmured. “We don't throw the money away on frivolities."

     “Build a habitat big enough to house everyone living at Ceres?" asked Martin Humphries, incredulous.
     “That's what the rumble is," said his aide.
     “It sounds ridiculous," Humphries said. “How reliable is this information?"
     The aide let a wintry smile cross her lips. “Quite reliable, sir. The prospectors are all talking about it, back and forth, from one ship to another. They're chattering all across the Belt about it."
     “It still sounds ridiculous," Humphries grumbled.
     “Beg to differ, sir," said the aide. Her words were deferential, but the expression on her face looked almost smug. “It makes a certain amount of sense."
     “Does it?"
     “If they could build a habitat and spin it to produce an artificial gravity that approaches the grav field here on the Moon, it would be much healthier for the people living out there for months or years on end. Better for their bones and organs than sustained microgravity."
     “In addition, sir, the habitat would have the same level of radiation shielding that the latest spacecraft have. Or even better, perhaps."
     “But the prospectors still have to go out into the Belt and claim the asteroids."
     “They are required by law to be present at an asteroid in order for their claim to be legal," the aide agreed. “But from then on they can work the rock remotely."
     “Remotely? The distances are too big for remote operations. It takes hours for signals to cross the Belt."
     “From Ceres, sir," the aide said stiffly, “ roughly five thousand ore-bearing rocks are within one light-minute. That's close enough for remote operations, don't you think?"
     Humphries didn't want to give her the satisfaction of admitting she was right. Instead he replied, “Well, we'd better be getting our own people out there claiming those asteroids before the rock rats snap them all up."

From THE ROCK RATS by Ben Bova (2002)

(ed note: Lensman Kimball Kinnison is going undercover, taking the assumed identity of a meteor-miner in order to infiltrate the bad guy's organization)

Thus it came about that Kinnison took his scarcely-used indetectable speedster back to Prime Base; and that, in a solar system prodigiously far removed from both Tellus and Bronseca there appeared another tramp meteor-miner.

Peculiar people, these toilers in the inter-planetary voids; flotsam and jetsam; for the most part the very scum of space. Some solar systems contain more asteroidal and meteoric debris than did ours of Sol, others less, but few if any have none at all. In the main this material is either nickel-iron or rock, but some of these fragments carry prodigious values in platinum, osmium, and other noble metals, and occasionally there are discovered diamonds and other gems of tremendous size and value. Hence, in the asteroid belts of every solar system there are to be found those universally despised, but nevertheless bold and hardy souls who, risking life and limb from moment to moment though they are, yet live in hope that the next lump of cosmic detritus will prove to be Bonanza.

Some of these men are the sheer misfits of life. Some are petty criminals, fugitives from the justice of their own planets, but not of sufficient importance to be upon the "wanted" lists of the Patrol. Some are of those who for some reason or other—addiction to drugs, perhaps, or the overwhelming urge occasionally to go on a spree—are unable or unwilling to hold down the steady jobs of their more orthodox brethren. Still others, and these are many, live that horridly adventurous life because it is in their blood; like the lumber-jacks who in ancient times dwelt upon Tellus, they labor tremendously and unremittingly for weeks, only and deliberately to "blow in" the fruits of their toil in a few wild days and still wilder nights of hectic, sanguine, and lustful debauchery in one or another of the spacemen's hells of which every inhabited solar system has its quota.

But, whatever their class, they have much in common. They all live for the moment only, from hand to mouth. They all are intrepid space-men. They have to be—no others last long.

They all live hardly, dangerously, violently. They are men of red and gusty passions, and they have, if not an actual contempt, at least a loud-voiced scorn of the law in its every phase and manifestation. "Law ends with atmosphere" is the galaxy-wide creed of the clan, and it is a fact that no law save that of the ray-gun is even yet really enforced in the badlands of the asteroid belts.

Indeed, the meteor miners as a matter of course take their innate lawlessness with them into their revels in the crimson-lit resorts already referred to. In general the nearby Planetary Police adopt a laissez-faire attitude, particularly since the asteroids are not within their jurisdictions, but are independent worlds, each with its own world-government If they kill a dozen or so of each other and of the bloodsuckers who batten upon them, what of it? If everybody in those hells could be killed at once, the universe would be that much better off!—and if the Galactic Patrol is compelled, by some unusually outrageous performance, to intervene in the revelry, it comes in, not as single policemen, but in platoons or in companies of armed, full-armored infantry going to war!

His ship, a stubby, powerful space-tug with an oversized air-lock, was a used job—hard-used, too—some ten years old. She was battered, pitted, and scarred; but it should be noted here, perhaps parenthetically, that when the Patrol technicians finished their rebuilding she was actually as staunch as a battleship. His space-armor, Spalding drills, DeLameters, tractors and pressors, and "spee-gee" (torsion specific-gravity apparatus) were of the same grade.

Arrived at last, he gave his chunky space-boat the average velocity of an asteroid belt just outside the orbit of the fourth planet, shoved her down into it, turned on his Bergenholm, and went to work. His first job was to "set up"; to install in the extra-large air-lock, already equipped with duplicate controls, his tools and equipment. He donned space-armor, made sure that his DeLameters were sitting pretty—all meteor miners go armed as routine, and the Lensman had altogether too much at stake in any case to forego his accustomed weapons—pumped the air of the lock back into the body of the ship, and opened the outer port. For meteor miners do not work inside their ships. It takes too much time to bring the metal in through the air-locks. It also wastes air, and air is precious; not only in money, although that is no minor item, but also because no small ship, stocked for a six-weeks run, can carry any more air than is really needed.

With expert ease Kinnison clamped the meteorite down and rammed into it his Spalding drill, the tool which in one operation cuts out and polishes a cylindrical sample exactly one inch in diameter and exactly one inch long. Kinnison took the sample, placed it in the jaw of his spee-gee, and cut his Berg. Going inert in an asteroid belt is dangerous business, but it is only one of a meteor miner's hazards and it is necessary; for the torsiometer is the quickest and simplest means of determining the specific gravity of metal out in space, and no torsion instrument will work upon inertialess matter.

He read the scale even as he turned on the Berg. Seven point nine. Iron.

Worthless. Big operators could use it—the asteroid belts had long since supplanted the mines of the worlds as sources of iron—but it wouldn't do him a bit of good. Therefore, tossing it aside, he speared another. Another, and another. Hour after hour, day after day; the back-breaking, lonely labor of the meteor miner.

And physically, he was all set for his first real binge as a meteor-miner.

His shoulder and arm were as good as new. He had a lot of metal; enough so that its proceeds would finance, not only his next venture into space, but also a really royal celebration in the spacemen's resort he had already picked out.

For the Lensman had devoted a great deal of thought to that item. For his purpose, the bigger the resort—within limits—the better. The man he was after would not be a small operator, nor would he deal directly with such. Also, the big king-pins did not murder drugged miners for their ships and outfits, as the smaller ones sometimes did. The big ones realized that there was more long-pull profit in repeat business.

Therefore Kinnison set his course toward the great asteroid Euphrosyne and its festering hell-hole, Miners' Rest. Miners' Rest, to all highly moral citizens the disgrace not only of a solar system but of a sector; the very name of which was (and is) a by-word and a hissing to the blue-noses of twice a hundred inhabited and civilized worlds.

And the fellow was honest enough in his buying of the metal. His Spaldings cut honest cores—Kinnison put micrometers on them to be sure of that fact. He did not under-read his torsiometer, and he weighed the meteors upon certified balances. He used Galactic Standard average-value-density tables, and offered exactly half of the calculated average value; which, Kinnison knew, was fair enough. By taking his metal to a mint or a rare-metals station of the Patrol, any miner could get the precise value of any meteor, as shown by detailed analysis.

However, instead of making the long trip and waiting—and paying—for the exact analyses, the miners usually preferred to take the "fifty-percent-of-average-density-value" which was the customary offer of the outside dealers.

(ed note: so you take the meteor and use the Sparling to cut a cylindrical 1"×1" core. The spee-gee determines the specific gravity. The average value density table looks up specific gravity and yields the dollar-per-gram value of the meteor. The balance measures the mass of the entire meteor. Multiply meteor mass in grams by dollar-per-gram to get dollar value of meteor. Outside dealers offer half of the dollar value of meteor.)

From GRAY LENSMAN by E.E. "Doc" Smith (1936)

      Dmitri Herndon was a happy man. A sweaty, tired happy man.
     He pushed the ore—carrier ahead of him, toward the welcome gleam of his ship’s floodlights.
     There was enough high—grade in the carrier to pay off his bill with Transkootenay, grubstake himself for another lonely six weeks in this desolate belt, and some to send home to his sister on Lorraine VII. And the hold of his shabby, converted yacht was about half—full of other saleable metals.
     Better still, he thought, hoped, rather that he had seen trace enough to think there could be a diamond “pipe” here on this rotten planetoid, which would make him slightly richer than the revered Joseph Smith.
     If this belt was indeed part of an exploded planet, God hadn't blown it up nearly enough, Herndon thought sourly, looking out into hard blackness, and thousands of spinning dots, not stars, dimly lit by the system's dying sun.
     But then, if God hadn't blasted it, there wouldn't be any miners in the system, wouldn't be any fissionable ore in Herndon‘s carrier and ship, and Herndon himself might still be back teaching basic chemistry on Lorraine.

     He often thought of the image people had of deepspace miners — brawny, bearded, quick to brawl, profane.
     Herndon may have had the beard, but little else. In fact, he'd grown it to not look entirely like the image of a professor, which stereotype he did resemble.
     He’d quit teaching, dreaming of riches, and followed the rush into this system. It‘d been six months of the hardest, most dangerous work he could have imagined. If he wasn't carefully placing and blowing charges, ever aware of the likelihood he‘d blow himself to flinders as a self-taught powder monkey, he was breaking big rocks into little rocks with a powered drill, then checking them with his belt analyzer. Not to mention keeping himself somewhat fed, and his ship from expiring in a smolder of circuitry.

     He considered what he'd do if there were diamonds on this stupid rock.
     Real riches.
     He'd put his ship in the shop, have its rotten, hiccuping secondary drive rebuilt, first.
     No. He'd just find some other duckling, fresh into the Foley System, and convince him the bucket was just what he needed to go mining. Just as another miner had trapped Herndon.
     Then he'd buy another ship, and …

     No. He’d buy out his contract, and, if there were enough money, just retire. No benders, no jags, just a chance to go somewhere quiet, somewhere with a big computer, and he'd spend the rest of his life happily researching the break between alchemy and real chemistry.
     Maybe a planet with a big library, a big computer, and some nightlife. Professors didn‘t have to be reclusive, especially not rich professors.
     Something like Trimalchio IV, which he'd seen on the vids, heard stories about its decadence, never visited.
     His mind drifted, though he never lost his balance, bounding in ten—meter leaps toward the ship. Showgirls. Tall showgirls. Tall, blond showgirls. Or maybe brunettes. Smiling, barely clad, to be wooed with a handful of diamonds into impossible lusts.

     At least he'd had brains enough to register a claim on this jagged piece of stone as soon as he'd brought in the first load of ore, so he had all the time in the world to pick its bones, dreaming all the while of wealth. (and unfortunately making himself the target of claim-jumpers who bribe the clerks at the claim registry)
     He slid open the cover of his ship's exterior control panel, touched a sensor.
     The cargo hatch slid open. He pushed the carrier inside and dumped the ore into a expandable hold.
     He closed the hatch from the inside, and went into the hold‘s airlock, cycled it.
     The inner lock door opened, and Herndon unsealed his faceplate, winced, as always at the, well, reek. A few hours on the dry, recycled suit atmosphere, and he'd forget just how bad the cabin smelled, a mixture of bad cooking, and human odors.
     He decided he could allow himself one slivovitz, no more, after he checked to make sure the ship hadn’t developed any more mechanical surprises.

From STAR RISK, LTD. by Chris Bunch (2002)

      At the time the Rolling Stone arrived among the rolling stones of Rock City the Belt had a population density of one human soul for every two billion trillion cubic miles—read 2×1021. About half of these six thousand-odd lived on the larger planetoids. Ceres, Pallas, Vesta, Juno.

     The other three thousand inhabitants constitute the Belt’s floating population in a most literal sense; they live and work in free fall. Almost all of them are gathered into half a dozen loose communities working the nodes or clusters of the Belt. The nodes are several hundred times as dense as the main body of the Belt—if ‘dense’ is the proper word; a transport for Ganymede could have ploughed through the Hallelujah node and Rock City and never noticed it except by radar. The chance that such a liner would hit anything is extremely small.
     The miners worked the nodes for uranium, transuranics, and core material, selling their high grade at the most conveniently positioned large Asteroid and occasionally moving on to some other node. Before the strike in the Hallelujah the group calling themselves Rock City had been working Kaiser Wilhelm node behind Ceres in orbit; at the good news they moved, speeding up a trifle and passing in-orbit of Ceres, a ragtag caravan nudged through the sky by scooters, chemical rocket engines, jato units, and faith. Theirs was the only community well placed to migrate. Grogan’s Boys were in the same orbit but in Heartbreak node beyond the Sun, half a billion miles away. New Joburg was not far away but was working the node known as Reynolds Number Two, which rode the Themis orbital pattern, inconveniently far out.
     None of these cities in the sky was truly self-supporting, nor perhaps ever would be; but the ravenous appetite of Earth’s industries for power metal and for the even more valuable planetary-core materials for such uses as jet throats and radiation shields—this insatiable demand for what the Asteroids could yield—made certain that the miners could swap what they had for what they needed Yet in many ways they were almost self-supporting; uranium refined no further away than Ceres gave them heat and light and power; all of their vegetables and much of their protein came from their own hydroponic tanks and yeast vats, Single-H and oxygen came from Ceres or Pallas.
     Wherever there is power and mass to manipulate, Man can live.

(ed note: "core material" is handwavium that comes from planetary cores. Apparently it is very dense, which would be good for reactor shielding and torchship reaction chambers. In the novel core material is only found in the asteroid belt, because the novel subscribes to the now discredited idea that the belt is the result of a planet blowing up. Single-H is atomic hydrogen. This gives a better specific impulse than molecular hydrogen. NASA would use it if they could find a way to stablize it. Normally single-H explosively recombines into molecular hydrogen in a fraction of a second.)

     Just before lunch on the third day Captain Stone slowed his ship still more and corrected her vector by firing a jato unit; City Hall and several other shapes could be seen ahead. Later in the afternoon he fired one more jato unit, leaving the Stone dead in space relative to City Hall and less than an eighth of a mile from it He turned to the phone and called the Mayor.
     ‘Rolling Stone, Luna, Captain Stone speaking.’
     ‘We’ve been watching you come in, Captain,’ came the voice of the Mayor.
     ‘Good. Mr Fries, I’m going to try to get a line over to you. With luck. I’ll be over to see you in a half-hour or so.’
     ‘Using a line-throwing gun? I’ll send someone out to pick it up.’
     ‘No gun, worse luck. With the best of intentions I forgot to stock one.’
     Fries hesitated. ‘Uh, Captain, pardon me, but are you in good practice for free-fall suit work?’
     ‘Truthfully, no.’
     ‘Then let me send a boy across to put a line on you. No, no! I insist’
     Hazel, the Captain, and the twins suited up, went outside, and waited. They could make out a small figure on the ship across from them; the ship itself looked larger now, larger than the Stone. City Hall was an obsolete space-to-space vessel, globular, and perhaps thirty years old. Roger Stone surmised correctly that she had made a one-way freighter trip after she was retired from a regular run.

     They completed the rest of the introductions; Mrs Fries took Hazel in tow; the twins trailed along with the two men, into the forward half of the globe. It was a storeroom and a shop; racks had been fitted to the struts and thrust members; goods and provisions of every sort were lashed or netted to them. Don Whitsitt clung with his knees to a saddle in the middle of the room with a desk folded into his lap. In his reach were ledgers on lazy tongs and a rack of clips holding several hundred small account books. A miner floated in front of him. Several more were burrowing through the racks of merchandise.
     Seeing the display of everything a meteor miner could conceivably need, Pollux was glad that they had concentrated on luxury goods.

     ‘Oh, Sandy hasn’t got anything to do but wait. Right, Sandy? Shake hands with Captain Stone—it was his wife who fixed up old Jocko.’
     ‘It was? Say, I’m mighty proud to know you, Captain! You’re the best news we’ve had in quite a while.’
     ‘You don’t know what it means to our people to have a medical doctor with us again'
     Fries nodded. ‘We’ll see what we can work out to make it easy on her. We won’t expect the lady to go hopping rocks the way Doc Schultz did. Get that, Sandy? We can’t have every rock-happy rat in the swarm hollering for the doctor every time he gets a sore finger. We want to get the word around that if a man gets sick or gets hurt it’s up to him and his neighbours to drag him in to City Hall if he can possibly wear a suit. Tell Don to draft me a proclamation.’

     'First, though, did you have any shopping in mind today? Anything you need? Tools? Oxy? Catalysts? Planning on doing any prospecting and if so, do you have your gear?’
     ‘Nothing especial today—except one thing: we need to buy, or by preference rent, a scooter. We’d like to explore a bit’
     Fries shook his head. ‘Friend, I wish you hadn’t asked me that. That’s one thing I haven’t got All these sand rats booming in here from Mars, and even from Luna, half of ‘em with no equipment They lease a scooter and a patent igloo and away they go, red hot to make their fortunes. Tell you what I can do, though—I’ve got more rocket motors and tanks coming in from Ceres two months from now. Don and I can weld you up one and have it ready to slap the motor in when the Firefly gets here.’

     'You might try old Charlie.’
     ‘Did you notice that big tank moored to City Hall? That’s Charlie’s hole. He’s a crazy old coot, rock-happy as they come, and he’s a hermit by intention. Used to hang around the edge of the community, never mixing—but with this boom and ten strangers swarming in for every familiar face Charlie got timid and asked could he please tie in at civic center? I guess he was afraid that somebody would slit his throat and steal his hoorah’s nest Some of the boomers are a rough lot at that’
     ‘He sounds like some of the old-timers on Luna. What about him?’
     ‘Oh! Too much on my mind these days; it wanders. Charlie runs a sort of a fourth-hand shop, and I say that advisedly. He has stuff I won’t handle. Every time a rock jumper dies, or goes Sunside, his useless plunder winds up in Charlie’s hole. Now I don’t say he’s got a scooter—though you just might lease his own now that he’s moored in-city. But he might have parts that could be jury-rigged.

     It took the better part of two weeks to make the ancient oxyalcohol engine work; another week to build a scooter rack to receive it, using tubing from Fries’ secondhand supply. It was not a pretty thing, but, with the Stone’s stereo gear mounted on it, it was an efficient way to get around the node. Captain Stone shook his head over it and subjected it to endless tests before he conceded that it was safe even though ugly.
     In the meantime the Committee had decreed a taxi service for the doctor lady; every miner working within fifty miles of City Hall was required to take his turn at standby watch with his scooter, with a fixed payment in high grade for any run he might have to make. The Stones saw very little of Edith Stone during this time: it seemed as if every citizen of Rock City had been saving up ailments.
     But they were not forced to fall back on Hazel’s uninspired cooking. Fries had the Stone warped into contact with City Hall and a passenger tube sealed from the Stone’s lock to an unused hatch of the bigger ship; when Dr Stone was away they ate in his restaurant. Mrs Fries was an excellent cook and she raised a great variety in her hydroponics garden.
     While they were rigging the scooter the twins had time to mull over the matter of the flat cats (fuzzy Martian pets that were the inspiration for Tribbles). It had dawned on them that here in Rock City was a potential, unexploited market for flat cats. The question was: how best to milk it for all the traffic would bear?
     Pol suggested that they peddle them in the scooter; he pointed out that a man’s sales resistance was lowest, practically zero, when he actually had a flat cat in his hands. His brother shook his head ‘No good,’ Junior.’
     ‘Why not?’
     ‘One, the Captain won’t let us monopolize the scooter; you know he regards it as ship’s equipment, built by the crew, namely us. Two, we would burn up our profits in scooter fuel. Three, it’s too slow; before we could move a third of them, some idiot would have fed our first sale too much, it has kittens—and there you are, with the market flooded with flat cats. The idea is to sell them as nearly as possible all at one time.’
     ‘We could stick up a sign in the store—One-Price would let us—and sell them right out of the Stone.’
     ‘Better but not good enough. Most of these rats shop only every three or four months. No, sir, we’ve got to build that better mouse trap and make the world beat a path to our door.’
     ‘I’ve never been able to figure out why anybody would want to trap a mouse. Decompress a compartment and you kill all of them, every time.’
     ‘Just a figure of speech, no doubt Junior, what can we do to make Rock City flat-cat conscious?’
     They found a way. The Belt, for all its lonely reaches—or because of them—was as neighbourly as a village. They gossiped among themselves, by suit radio. Out in the shining blackness it was good to know that, if something went wrong, there was a man listening not five hundred miles away who would come and investigate if you broke off and did not answer.
     They gossiped from node to node by their more powerful ship’s radios. A rumor of death, of a big strike, or of accident, would bounce around the entire belt, relayed from rockman to rockman, at just short of the speed of light. Heartbreak node was sixty-six light minutes away, following orbit; big news often reached it in less than two hours, including numerous manual relays.
     Rock City even had its own broadcast. Twice a day One-Price picked up the news from Earthside, then re-broadcast it with his own salty comments.
The twins decided to follow it with one of their own, on the same wave length—a music & chatter show, with commercials. Oh, decidedly with commercials. They had hundreds of spools in stock which they could use, then sell, along with the portable projectors they had bought on Mars.
     They started in; the show never was very good, but, on the other hand, it had no competition and it was free. Immediately following Fries’ sign-off Castor would say, ‘Don’t go away, neighbours! Here we are again with two hours of fun and music—and a few tips on bargains. But first, our theme—the warm and friendly purr of a Martian flat cat.’ Pollux would hold Fuzzy Britches up to the microphone and stroke it; the good-natured little creature would always respond with a loud buzz. ‘Wouldn’t that be nice to come home to? And now for some music: Harry Weinstein’s Sunbeam Six in “High Gravity”. Let me remind you that this tape, like all other music on this program, may be purchased at an amazing saving in Flat Cat Alley, right off the City Hall—as well as Ajax three-way projectors in the Giant, Jr. model, for sound, sight, and stereo. The Sunbeam Six—hit it, Harry!’

     They toyed with the idea of using their time to prospect on their own, but a few trips out in the scooter convinced them that it was a game for experts and one in which even the experts usually made only a bare living. It was the fixed illusion that the next mass would be ‘the glory rock’—the one that would pay for years of toil—that kept the old rockmen going. The twins knew too much about statistics now, and they believed in their ability rather than their luck. Finding a glory rock was sheer gamble.
     They made one fairly long trip into the thickest part of the node, fifteen hundred miles out and back taking all one day and the following night to do it. They got the scooter up to a dawdling hundred and fifty miles per hour and let it coast, planning to stop and investigate if they found promising masses having borrowed a stake-out beacon from Fries with the promise that they would pay for it if they kept it.
     They did not need it. Time after time they would spot a major blip in the stereo radar, only to have someone else’s beacon wink on when they got within thirty miles of the mass. (somebody else already staked a claim) At the far end they did find a considerable collection of rock travelling loosely in company; they matched, shackled on their longest lines (their father had emphatically forbidden free jumping) and investigated. Having neither experience nor a centrifuge, their only way of checking on specific gravity was by grasping a mass and clutching it to them vigorously, then getting a rough notion of its inertia by its resistance to being shoved around. A Geiger counter (borrowed) had shown no radioactivity; they were searching for the more valuable core material.

From THE ROLLING STONES by Robert Heinlein (1952)

“This,” Friedrich von Baldur said, “is a hell of a place.”

“Little joke?” Grok said. “I think I have read someplace that Sheol equals hell?”

“Little joke,” M’chel agreed. “Very little.”

Chas Goodnight was staring out at what the Foleyites, or however they labeled themselves, called the outskirts of a city.

Sheol. Population 5,000, days. Who knew how many, or was sober/straight enough to count nights?

If Sheol ever had a city planning board, they were never among those who were straight. Sheol grew as it grew, and no one cared, since the minute the lodes went dry, the miners would move on (to another star system). Sheol’s population would drop to five senile prostitutes, four bartenders with delirium tremens, three arteriosclerotic retired miners, two historians and one city manager.


There were lots with battered ships, some of which might actually be practical for mining, supply houses with used gear from those who’d guessed wrong, and new supplies for those who hadn’t guessed at all yet.

Here and there were houses of the few citizens in service industries not battening off the asteroids.

As their rented lifter got closer to what passed for city center, there were streets entirely devoted to various forms of sin.

In the middle of one such blinking, flashing row of iniquities, some of which were yet to be invented, sat, like a prim maiden with her legs crossed in a whorehouse: MINER'S AID SOCIETY.

There appeared to be no one inside.

“Now this,“ Baldur announced heartily, “is my kind of place.” A delicate pink tongue came out, touched his lips. “It smells of credits. Loose credits, just waiting to leap into our pockets.”

From STAR RISK, LTD. by Chris Bunch (2002)

      "You probably won't believe this, but I didn't always used to be the class act I am today. I mean, s**t, I finished out my last tour with Fleet and I didn't know what the hell I was gonna do for the next sixty years. There isn't all that much demand for middle-aged intrasystem tug pilots with no log time on civilian models, is there?"
     "I wouldn't think so," Moses said.
     "You wouldn't be wrong. Anyway, I thought about going back to school, getting my ticket updated, but, hell, I was forty-one years old—I was goddammed ancient, right?" He laughed, in rueful self-deprecation. "At least, that was how it felt at the time. But what it came down to was I just couldn't face sitting in some classroom for two or three years just for the privilege of starting out at the bottom all over again. I figured I had better than that coming to me.
     "So, I set up a line of credit against my pension, pulled every damn standard I had in the bank out of the bank, and bought my way into a mining partnership."
     "Just like that, then?"
     "Yeah. Yeah, pretty much just like that, actually. It's never all that hard to find people who aren't satisfied with what they've got. 'Course, if I knew then what I know now. . . Thing is, when you do find 'em, you ought to ask yourself why they don't have more already if they want it so bad."
     "You didn't ask."
     "Hell, no. But none of them asked about me, either. So I guess that's square all around, isn't it? Anyway, it didn't matter. We were gonna get rich, all of us, even if none of us had ever even seen an asteroid up close before. At least that was the theory."
     "It didn't work out that way?"
     "Not quite. Like the popcart said, the fault wasn't in the stars, Captain, but in ourselves. Asteroid prospecting's brutal work. You've got to want it, you've got to work at it—and you've got to be ready to sweat it out for a long, long time before it starts to pay off worth a damn. The only trouble with that was that if any of us were capable of that kind of commitment, we probably wouldn't have been available to go prospecting in the first place.
     "I think Zhdanov was the first of us to pack it in. I wasn't too surprised, I guess. We never did live up to his high expectations. He had this fancy, idealistic vision of all us noble, cooperative workers hitting the big strike overnight and retiring in well-deserved comfort."
     "No, huh?"
     "Oh, it was a terrific vision, no complaints there. It's just that actually going out and doing the mining didn't fit into it anywhere. You know what prospecting's like, Captain. You're picking through the garbage dump of the solar system. You take a week to catch up to some lump of rock that's just a dot of light on your screens so you can get a spectro laser on it, and then if it ain't worth s**t, which it usually isn't, you turn away around and fly off to another rock another week away and try your luck there. Well, Zhdanov just wasn't up to that. All we could afford was this dumpy old Atlas-class tug we rescued from the mothballers, and he just couldn't put up with the crowding and the predigested food and the no privacy and the tempers—hell, you know how it is. It was all just too real for him, I guess.
     "Pao left next, and that was a bitch—she was the only one in the group besides me who had her pilot's ticket. But two or three intrasystem crawls were all she could put up with. I still see her around; she's flying sunrise orbits for the tourists out of Highside; she's doing okay. Then Barnett left, but all he'd brought into the deal was daddy's money, and that was gone, so the hell with him.
     "Pacmani tried to stick it out, he really did, but his suit blew a vernier and spun him visor-first into the rim of the airlock, and that was it."
     "Yeah. Messy. It would have put Zhdanov right off his tea and cookies. So that left just me and a half-paid-for tug we'd never even agreed on a name for. A real recipe for success, huh?"
     "So what did you do?"
     "What did I do? I went out, and when I didn't score big on that run, I reprovisioned as best I could and went out again, and again. It's a drug, prospecting. It hooks you once you start thinking like that. The next time, right, the next time, for sure, it's gotta happen. And while you're looking for that next time, you're getting broker and broker. When you finally have to choose between fuel and spare parts, or buying food, you buy the fuel and the parts, and scrape by on the cheapest prepackaged boat rations you can find. And when you get down to choosing between fuel and spares, you choose the fuel, and run on your backups or do without. You'd be amazed at some of the things you don't need to survive out there, Captain, and I hope to god you never have to try and find out just what they are.
     "Finally you just stop coming back to the depots at all, unless you've got some little half-junk rock to sell off for a grubstake or you just get sick of the smell of yourself in the air and the taste of yourself in the water. And when you do get back to the depots, they avoid you, because they can see what's going on, and they know you're gonna go out that one time too many and try to shave it too fine that one time too often, and that'll be all. So you start getting strange out there: you start talking to yourself or to people who aren't there, or you don't talk at all, to anybody, and you start to forget what the sound of your voice sounds like.
     "That's the kind of shape I was in. I've got good manners, Captain; when I go crazy I at least keep it to myself. But one more trip out, maybe two, and I would have done something stupid enough to be permanent.

From THE SHATTERED STARS by Richard S. McEnroe (1984)

Claim Jumpers

Once a rock-rat asteroid miner stakes a claim on an asteroid, they are vulnerable to claim-jumpers. These crooks try to steal the claim, cashing in on all the work the poor-rock rat did to find the blasted thing in the first place.

Polite claim-jumpers just steal the claim to the asteroid by some illegal means. Impolite claim-jumpers murder the rock-rat, steal all their gear, and then steal the claim. Smart claim-jumpers bribe workers at the claim office in order to get advanced notice about lucrative new claims.


      Claim jumpers and pilferers—men who worked others’ mines for short periods in the owners’ absence, gradually building up a cargo—were no exception to the rule. Pilferers had an extra reason for being careful—they didn’t want to leave any evidence.
     “But I don’t see how they could get away with it,” Peter protested. “Every time we bring in a cargo, we have to identify ourselves and our claim.” He paused as a thought struck him. “That proves us right, Mr. Vincennes—the records back in the assaying office.”
     Vincennes’ whole tone had changed. He said, not unpleasantly: “No, my young friend, I’m afraid it doesn’t prove as much as you think. The most it could prove was your honest belief. The assaying office hasn’t been as careful as it might be; I’ve noticed that. I was there a few days ago when a miner brought in his first cargo of manganese. He identified it as coming from his claim on 29-82, and the clerk only checked for the existence of a manganese claim on that asteroid. He didn’t ask for proof on the owner’s name or filing date. I watched, and saw him enter the claim on his asteroid chart. The next time that miner comes in, the clerk will look at his chart and see that a manganese claim is listed for 29-82. As long as the same person keeps coming back—or someone saying he’s working for that person—the only check will be by that incomplete record.”
     Peter stared, and gasped, “But … why any pilferer could say he was working for the man he stole from! So could a jumper.”
     “That,” said Vincennes, “is just what has been happening, I believe.”

     “Don’t see how things got so sloppy,” objected Clay. “Do you suppose the clerk could be getting something on the side?”
     “This is possible, but there’s a better explanation for the easygoing way the office operates. I’ve been out here nearly twenty years, Mr. Clay. Things were much different then. There were fewer miners; Cerestown was brand new; and there was plenty of easily found mineral for everyone who came along.
     “In those days, there was no such thing as pilfering and claim jumping. You see, people usually don’t become dishonest unless they feel they have to be. So long as there was more than enough to go around, and not too much trouble finding it, then a man’s simple word was good enough.

     “But it’s become rougher in twenty years. There’s still unguessable wealth out here, still bonanzas up in the sky. I don’t think they’ll be played out in a couple of hundred years—not even if there’s a hundred times as many people out hunting them. The ships and the equipment we have today are better than they were, but not enough better so that prospectors can start out with minimum equipment and find a good strike on the fringes of the Belt. The heart of the Belt is still unsafe, to say the least.
     “I have with me,” he indicated his ship and crew, “equipment for depth mining. It took me a number of years, working the way you two are working, to get this equipment. If there hadn’t been galena right on the surface of this asteroid, you two would have kept on going.”
     “Yes, I see your point,” Clay agreed. “So I guess that’s a good part of the explanation. These here pilferers and jumpers started out honest, but they couldn’t find anything. I guess they didn’t want to give up, so they decided to—well, at first maybe just borrow a little mineral from someone who had plenty. They probably felt sorry about it and figured they’d make a strike with what they got this way and pay it all back somehow.”
     “That sounds very likely, Clay. In some cases, one little theft or two was all that was needed. But some still had bad luck; or perhaps they found that this was much easier than grubbing around, looking for a claim of their own. However it happened, it has happened, and now we’ve had to set up a police force.”

     “The Claims Office was working hand in glove with jumpers and pilferers, taking a generous slice of the loot for their services in making everything appear straight. They couldn’t hope to get away with it forever. They just cleaned up as much as they could and skipped out when it became too hot to sit on any longer, leaving old Yerxa to face the inquiry. Fortunately, his good name has been cleared, and Old Caution has kept things in order.”

     “No trouble; we’ll let you know as soon as we find out anything.” Clay cut the connection, and turned to breakfast. “Well, Pete, my trick for cooking starts tomorrow, then you can sit around and get served. Don’t rightly see that there’s anything to worry about unless Glen’s had an accident. Our mine and Glen’s put together wouldn’t be worth a claim-jumper’s time. We’ll make the first one who comes along a present of it next year—if it pans out the way it’s going now. That’ll give us enough for a grubstake; then I’ll show you what the rough life is really like, fellow—prospecting.” He grinned. “You’ve been living in sheer comfort, in case you didn’t know it.”

     “You haven’t told me much about this ‘trouble’ business,” Peter said.
     Clay smiled as he finished checking the ammunition. “Back on Earth, in my grandfather’s time and before, they used to print books and magazines full of stories picturing what things might be like out here. Pretty fantastic, some of those stories were, too. They had Mars and all the other planets full of strange and hostile people—critters that weren’t intelligent, but dangerous. Well, when men got to Mars, then came out here, they found that there was only one really dangerous critter around.”
     “What was that? I never heard of any.”
     “Yes, you have; the dangerous critter was man himself. That’s why we have to have guns and ammunition. It’s not as bad as it was back on Earth—as you’ve seen in historical films—but there’re still some men who’re dangerous to the majority.
     “Out here, partner, the law’s good, and your rights are good, as long as the other man recognizes it. Most do. But a few try to pay no attention. They get away with it if you can’t prove your rights or your legality with explosive pellets. That’s the way someone takes to question you. Back on Mars no one could get away with it. In Cerestown your rights are respected. But out here—who’s going to see what you do and stop you from doing it, or prove you did it if you destroy the evidence? Some claim jumpers have been caught when they tried to pass off their stuff on Cerestown or Mars, but there are others who’ve gotten away with it—and as long as one succeeds, another is going to try sometime.”

     “The guard is,” Ezzard amended. “That’s only part of the Association. There has been quite a bit of shady work afoot. I can’t go into details, but a number of miners have been defrauded of their claims by thieves posing as businessmen. Others have had ‘accidents’ which laid them up long enough for claim jumpers to take possession of their mines. In many cases the jumpers could afford expensive legal action where the miners could not.

     Cerestown Supply carried all the goods anyone wanted to buy on the planetoid. Food and basic necessities came through Maintenance; the big store carried appliances and luxury items imported from Mars, or Earth and Luna.
     Peter remembered that he still owed his father that E-string, and decided to pay his debt. Extra credits would soon be in short supply, since their mining operations had stopped. When the Clays started up again, there’d be a backlog of taxes to be deducted. A miner obtained credits from his cargoes or from maintenance work, Public Duty. Everyone shared in the latter, working a certain number of days a year in regulated shifts, wherever their skills were needed.
     A prospector who had a run of bad luck didn’t starve. He’d take an emergency shift in Public Duty, and his pay would consist of the excess-value of his work. After a few months his credits would accumulate until he had a grubstake for another expedition. There was a basic staff of men and women, whose careers were in food production in the hydroponic gardens and chemical laboratories, refining, air supply, transportation, communication, construction, repair, light, administration, and so forth. This staff was assisted by those on annual or emergency shifts.

     “There is something afoot that doesn’t look too good, but it isn’t jumpers lying in ambush with longmen. Ever hear of the Belt Insurance Company?”
     “No, never have.”
     “Well, it’s been going for a short time—sounded like a good thing, at first. You’d sign up, and they’d guarantee full compensation for any kind of accidents. They’d pay your taxes during any period you were laid up, and grubstake you at reasonable rates if you wanted to prospect. The premiums were somewhat high, but not exorbitant.
     “But it turns out that there was a catch. If, at any time, you miss a premium payment, Belt Insurance can seize any and all claims you own, or any claims you stake, until the policy is paid in full. It means that just a little bad luck—the kind any miner’s likely to have—makes you an employee of Belt Insurance. They won’t force you out—nothing like that—but you no longer own your mine. You’re working for them on what amounts to a salary, and they make certain that they get the big cut of your profits.”

     Peter scanned the small plastic sheet, then looked up. “Is ... is this all that appears on the copies you have here?”
     Kreuder nodded. “Yes. You see, at first miners filed on certain metals in a location. Later, it was found that a given location might have several types of valuable deposit. One of the first requests the Asteroid Miners’ Association made was to change the system. Now miners stake a claim on the location alone, and place the second and third copies in finders and markers.
     “We saw the justice in the suggestion, but offered a compromise: the original filings would list one specific metal and the area claimed. Our duplicates here would only show the area. We didn’t want to help claim jumpers learn just where the most valuable mines could be found, so we revised our files. That is when we discovered the forgeries. So the way matters stand, Mr. Clay, if your filing is valid, you own not only the galena in that area, but anything else there, down to the center of the asteroid. Get it?”

From MYSTERY OF THE THIRD MINE by Robert Lowndes (1953)

      Set up, he studied his electros and flicked his tractor beams out to a passing fragment of metal, which flashed up to him, almost instantaneously. Or, rather, the inertialess tugboat flashed across space to the comparatively tiny, but inert, bit of metal which he was about to investigate.

     With expert ease Kinnison clamped the meteorite down and rammed into it his Spalding drill, the tool which in one operation cuts out and polishes a cylindrical sample exactly one inch in diameter and exactly one inch long. Kinnison took the sample, placed it in the jaw of his spee-gee, and cut his Berg. Going inert in an asteroid belt is dangerous business, but it is only one of a meteor miner's hazards and it is necessary; for the torsiometer is the quickest and simplest means of determining the specific gravity of metal out in space, and no torsion instrument will work upon inertialess matter.

     He read the scale even as he turned on the Berg. Seven point nine. Iron.

     Worthless. Big operators could use it—the asteroid belts had long since supplanted the mines of the worlds as sources of iron—but it wouldn't do him a bit of good. Therefore, tossing it aside, he speared another. Another, and another. Hour after hour, day after day; the back-breaking, lonely labor of the meteor miner. But very few of the bona-fide miners had the Gray Lensman's physique or his stamina, and not one of them all had even a noteworthy fraction of his brain.

     And brain counts, even in meteor-mining. Hence Kinnison found pay-metal; quite a few really good, although not phenomenally dense, pieces.

     Then one day there happened a thing which, if it was not in actual fact premeditated, was as mathematically improbable, almost, as the formation of a planetary solar system; an occurrence that was to exemplify in startling and hideous fashion the doctrine of tooth and fang which is the only law of the asteroid belts. Two tractor beams seized, at almost the same instant, the same meteor! Two ships, flashing up to zone contact in the twinkling of an eye, the inoffensive meteor squarely between them! And in the air lock of the other tug there were two men, not one; two men already going for their guns with the practiced ease of space-hardened veterans to whom the killing of a man was the veriest bagatelle!

     They must have been hi-jackers, killing and robbing as a business, Kinnison concluded, afterward. Bona-fide miners almost never work two to a boat, and the fact that they actually beat him to the draw, and yet were so slow in shooting, argued that they had not been taken by surprise, as had he. Indeed, the meteor itself, the bone of contention, might very well have been a bait. He could not follow his natural inclination to let go, to let them have it.

     The tale would have spread far and wide, branding him as a coward and a weakling. He would have had to kill, or have been killed by, any number of lesser bullies who would have attacked him on sight. Kinnison's hands flashed to the worn grips of his DeLamaters, sliding them from the leather and bringing them to bear at the hip with one smoothly flowing motion that was a marvel of grace and speed. But, fast as he was, he was almost too late. Four bolts of lightning blasted, almost as one. The two desperadoes dropped, cold; the Lensman felt a stab of agony sear through his shoulder and the breath whistled out of his mouth and nose as his space-suit collapsed. Gasping terribly for air that was no longer there, holding onto his senses doggedly and grimly, he made shift to close the outer door of the lock and to turn a valve.

     He did not lose consciousness—quite—and as soon as he recovered the use of his muscles he stripped off his suit and examined himself narrowly in a mirror. Eyes, plenty bloodshot. Nose, bleeding copiously. Ears, bleeding, but not too badly; drums not ruptured, fortunately —he had been able to keep the pressure fairly well equalized. Felt like some internal bleeding, but he could see nothing really serious. He hadn't breathed space long enough to do any permanent damage, he guessed.

     Then, baring his shoulder, he treated the wound with Zinsmaster burn-dressing. This was no trifle, but at that, it wasn't so bad. No bone gone—it'd heal in two or three weeks. Lastly, he looked over his suit If he'd only had his G-P armor on—but that, of course, was out of the question. He had a spare suit, but he'd rather... Fine, he could replace the burned section easily enough. QX.

     He donned his other suit, re-entered the air lock, neutralized the screens, and crossed over; where he did exactly what any other meteor miner would have done. He divested the bloated corpses of their space-suits and shoved them off into space. He then ransacked the ship, transferring from it to his own, as well as four heavy meteors, every other item of value which he could move and which his vessel could hold. Then, inerting her, he gave her a couple of notches of drive and cut her loose, for so a real miner would have done. It was not compunction or scruple that would have prevented any miner from taking the ship, as well as the supplies. Ships were registered, and otherwise were too hot to be handled except by organized criminal rings.

     As a matter of routine he tested the meteor which had been the innocent cause of all this strife—or had it been a bait?—and found it worthless iron. Also as routine he kept on working.

From GRAY LENSMAN by E.E. "Doc" Smith (1936)
      Dark anger lowered in the captain’s face. “We had just staked out our claim when that damned pirate came up. We didn’t have a chance. Practically my whole crew was out on the asteroid, unarmed; and they had a torpedo gun trained on us. There wasn’t a thing we could do but curse and watch. They erased our monuments, raised their own; took over whatever thermatite (the incredibly valuable mineral the asteroid is full of) we had already mined, emptied our fuel tanks, smashed our radio, and set us adrift.”
     The law of filing on newly discovered asteroids was definite. Two steps were required. First, setting up the proper monuments on the asteroid. Second, filing the requisite affidavits in the Claims Office of jurisdiction. In this case, Planets. One step alone was not sufficient. Prior monuments meant nothing; the date of filing controlled. Well, if Kerry Dale wanted to take the chance, who was he to stop him! In his mind’s eye. Ball could hear old Kenton’s approving chuckle. The old man was pretty sore over that last trick Dale had pulled on him.
     “Looks all right. We’re landing, though.”
     “To reset your monuments. Filing’s no good without them, you know.”
     Let him have his fun, thought Ball sourly. Nuisance value, my eye! That skunk, Foote, won’t pay him a nickel.
     The ceremony didn’t take long. Four metal stakes were driven deep into the stone, exactly in the niches where Ball’s old ones had been ripped out. Then a photograving of claim to title was etched deep within the area bounded by the stakes. Meanwhile, Jem gleefully broke off the evidences left by the highjackers.

(ed note: So, the semi-good guy (Kenton) sent his asteroid miners to the belt where they found an incredibly valuable asteroid. Alas, the bad guy (Foote) had sent some asteroid pirates to claim-jump the asteroid miners: destroying the legitimate monuments, ruining the miner's spaceship, and then heading at high speed to the Planets Claim office at Vesta to file their stolen claim. The bad guy won't be indicted since the asteroid pirates he hired give him plausible deniability. The bad guy will tell the judge that he bought the asteroid from the asteroid pirates in good faith, he had no idea they were pirates (even though they were secretly hired by him in the first place to do piracy).

Our hero (Kerry Dale), who often butts heads with the semi-good guy, arrives and rescues the asteroid miners before their air runs out. He pulls a fast one. He gets the asteroid miners to sign their asteroid claim over to him in exchange for dragging their ship to port instead of seizing their ship as salvage. The asteroid miners figure sure, why not? The asteroid claim is worthless since the asteroid pirates will be filling their claim at Vesta any day now.

Then our hero surprises everybody by dragging the ship to port at Ganymede, instead of Vesta. What's going on?

Only this: it turns out that when you examine the asteroid's orbital elements, you'll see it is legally NOT part of the asteroid belt. It is a Trojan asteroid, which means it is legally part of the Jovian system. Remember that step 2 was filing the requisite affidavits in the Claims Office of jurisdiction? Well, for this asteroid the jurisdiction claim office is NOT the Planet office at Vesta. It is the office at Ganymede. In other words the asteroid pirates claim filing is null and void, while our hero's claim is valid!

This also allows our hero to stick-it to the semi-good guy as well, since the claim was signed over to the hero. Trust me, the semi-good guy deserved it.)

From JURISDICTION by Nat Schachner (1941)

Asteroid Moving

Moving an asteroid from out in the boondocks into a more convenient orbit around Luna or Terra can be a big savings for an asteroid miner. The drawback includes the hefty delta V energy price, and the fact that if you make a mistake the resulting accidental asteroid strike could devastate Terra.

Asteroids being moved will be very closely monitored by the Spaceguard. If the asteroid strays off the flight path (specified in the asteroid moving permit), the Spaceguard will instantly "neutralize" the asteroid controllers (i.e., make the rock rats surrender at gunpoint or launch a military strike if the rock rats resist) and re-direct the asteroid into the proper path. The existing equipment will be used if the rock rat surrender (or if the equipment survives the military strike). Otherwise the Spaceguard will use their own equipment, carted along for just such emergencies.

When it comes to moving asteroids that could wipe out all signs of civilization on Terra, the Spaceguard has absolutely no sense of humor whatsoever.

Of course, just obtaining the initial permit from the Spaceguard will be a major undertanking in and of itself.

There was an entertaining bit in Poul Anderson's Ramble with a Gamblin' Man (1970). After the Asteroid Revolutionary War, the asteroids in the Leading Jupiter Trojans asteroids still belonged to Terra, but pretty much the entire belt is now part of the independent Asteroid Republic.

Terra, desperate to keep feeding bread and circuses to their global welfare state, has to make up for the lost revenue now that the asteroids are independent (yes, Poul Anderson firmly believes in the Decay of the Fatherland). So they put the squeeze on Odysseus, largest of the Leading Trojans. And while they are at it, the puritanical elements in the Terran government want to shut down anything on Odysseus that even vaguely looks like "vice" or even "fun."

The Odysseans are facing ruin. Until the protagonist has a brilliant idea.

The people in the story use a handwaving antigravity technology called gee-gees. This is used for spacecraft and for terraforming asteroids. However, in theory it could be used to move an asteroid. Assuming you have access to huge amounts of water for hydrogen to feed fusion reactors to power the geegees.

Under the Convention of Vesta, possession of an asteroid depends upon the nationality of whoever first lands and files a claim with Space Control Central. But the interesting part is that asteroids are identified by their orbits. I'm sure you see where this is leading.

Under some flimsy pretext of moving the Odyssean ice reserves into a more advantageous location, they openly set up the reactors and geegess required to turn the asteroid into a spaceship. After about a years worth of thrusting, Odysseus leaves the Trojan cluster. Odysseus is no longer identified by its old orbit. It is considered to legally be a new asteroid.

Before Terra realizes what is happening, an Asteroid Republic ship lands on Odysseus, claims it, files the claim with Space Control Central, and a bunch of Asteroid Republic warship take up orbit just in case Terra gets any ideas. Odysseus is saved!

Since antigravity is more or less fantasy, asteroid miners will need more mundane methods to move their asteroids. A popular choice is using mass drivers, since they can use the rocky body of the asteroid itself as reaction mass.

In Michael McCollum's novel Thunder Strike! they alter the orbits of asteroids with charges of antimatter, in torus-shaped Penning traps. This is much more dramatic, but much more extravagant. Antimatter is many things, but "cheap" ain't one of them.


      It was the big asteroids that got the publicity but the little ones that had the value. The "Big Three" of the Inner Belt, Ceres, Pallas and Vesta, were already suitable for permanent colonies. A little farther out was a good handful of others, above three hundred kilometers in diameter and all likely candidates for long-term development: Hygeia, Euphrosyne, Cybele, Davida, Interamnia. The crew of the Alberich had tracked and ignored all these, along with anything else that was more than a kilometer or two across. Finding metal-rich planetoids was one thing; moving and mining them was a different and more difficult proposition.
     Darius Regulo, as junior member of the team, had been given the long and tedious job of first analysis and evaluation. He took all the observations: spectroscopic, active and passive microwave, thermal infra-red, and laser. That permitted the estimate of probable composition. Add in the data on size and orbital elements, and he had all he needed for the first recommendation. Nita Lubin and Alexis Galley would take his work, throw in Galley's encyclopedic knowledge of metal prices F.O.B. Earth orbit, and make the final decisions.
     Now Galley, grey-haired and bushy eye-browed, was sitting at the console. He looked like an old-fashioned bookkeeper, squinting his deep-set eyes at the output displays and muttering numbers beneath his breath. Every few seconds he would gaze up at the ceiling, as though reading invisible figures printed there.
     "It's the right size," he said at last. "Not bad elements either. I wish we could get a better idea of iridium content—that and the percentage of volatiles, they'll be the swing factors. What's the assay look like for lead and zinc, Darius? I don't see those anywhere."
     "They're negligible. I decided we might as well call them zero, for estimating purposes."
     "Did you now?" Alexis Galley sniffed. "I'll thank you to leave that decision to me, until you get a few more years on your shoulders. Now, let's have another look at those mass figures."
     Darius Regulo stood behind Galley, watching over his shoulder as the older man worked. If a twenty-four-year-old could pick up the results of twenty years of space mining experience just by watching and listening, he would do it. Already he had learned that the actual value of the metals was no more than a small part of the final decision. It was outweighed by the availability of the volatiles used to make the orbital shift, by the asteroid position in the System, and by final mining costs.
     Galley was nodding slowly. "I'm inclined to give it a try," he conceded. "You've done a fair job here, Darius." He swivelled in his chair. "What do you think, Nita? Shall we give this one a go?"
     The third member of the crew stood by the far wall of the ship, looking through the port at the irregular pitted mass of rock that was looming gradually closer to the Alberich. She was rubbing at the back of her head, thinking hard. "I don't know, Alexis. There's an ample margin on the volatiles, we can get it there easily enough. But can we do it quickly enough? The Probit group is offering a ten percent bonus for the next hundred million tons of nickel-iron in Earth orbit."
     Galley nodded. "They're fighting deadlines."
     "As usual," said Lubin. "And so are we. I'm afraid that Pincus and his team will beat us to it. I've been listening to their radio broadcasts and they'll be starting to move their choice in another day or two. Even if we decide this minute, we won't have the drives on this rock for close to a week, and we won't pick up any time on them in the transfer orbit. If anything, they're better placed for transfer than we are."
     "Then we're in trouble." Alexis Galley peered vacantly at the screen. "Getting there second would halve our profit. Maybe we should look some more, try and find one with a better composition."
     "We shouldn't do that." Regulo had been listening intently to the exchange. Alexis Galley was always too conservative, and Regulo needed that bonus far more than either Galley or Nita Lubin. "We've taken weeks to find one as good as this. How about trying a hyperbolic?"
     There was a silence from the other two.
     "There should be plenty of reaction mass for it," Regulo went on. "You said yourself that there were ample volatiles, Nita—and we'd pick up at least four weeks on total transit time."
     Galley looked up at Regulo's thin face and pale, bright eyes. "I think you know my views on hyperbolic transfers," he said. "Do I have to say them again? You'll boil off some of the volatiles and lose reaction mass on solar swing-by. If you're unlucky you'll find that you have to ask for help when you're past perihelion, just to get yourself slowed down into Earth orbit. You can spend twice your profits on tugs to help you in. Still"— he shrugged—"I don't like to close my mind to things, just because I'm getting older. How close in would we have to go?"
     "Three million kilometers, at perihelion."
     "From the center of the Sun, or from the surface?"
     "From the center."
     "Hell. We'd only be two and a quarter million from the solar surface. That's close, too close."
     "But we won't be there for long," Nita Lubin broke in. She came forward and stood by the screen. "I think we should do it. We've talked about it before, and we always find a reason not to. Let's try it. We don't have to stay with the rock, you know. We can separate ourselves on board the Alberich once we get in as far as Mercury, fly on an orbit with a bigger perihelion distance, and re-connect with the rock later."
     "But then we'll be too late to meet it," protested Galley. "If we fly past further out, we'll take longer."
     "Not if we take the Alberich on a powered fly-by. Alexis, you're just making up reasons to avoid trying." Nita Lubin seemed to have made up her mind. She turned to their junior crew member. "How long will it take you to work out a decent power trajectory for the Alberich? We'll need to have a few choices."
     Regulo did not speak. He reached into his pocket, produced an output sheet and held it out to her.
     "What's this?" Nita Lubin glanced quickly over the sheet, grinned, and placed it in front of Galley. "Orbits for the Alberich. He's really hungry, isn't he? Well, there's nothing wrong with that—it's what we're all here for. What do you think, Alexis? We'd have a twelve-million-kilometer perihelion for the ship. That's not too bad, though I suppose I'd better check it for myself. You two might as well get to work putting the drives out on the rock. We should have plenty of time for that if we can really pick up four weeks on the transfer, the way this analysis shows."
     Alexis Galley stood up slowly from the console and looked for a long moment at the other two. "I still don't like it, but I'll go along with it. You put up most of the money, Nita, and it's only right that we try and protect your investment. Remember one thing, though. Neither of you has ever done any work close in to the Sun. I have. We're going to find that timing is tighter there—you don't have as much margin for error as we have out here. If you don't mind, Nita, I'll check those calculations when you've done with them."
     He left the cabin and went forward towards the drive supplies and installation facility. Nita Lubin looked after him thoughtfully. "You know, he's only going along with this for me, Darius. I'm wondering if we ought to go through with it. Alexis has more experience than the two of us put together."
     Regulo stared at her, his head cocked to one side. "What do you mean, Nita? I thought it was all settled. Look, I don't know about you but I certainly don't want to lose to the Pincus group. That's what will happen if we settle for the usual elliptic orbit transfer. We'll lose, there's no question of it."
     His face had gone pale, and his eyes blazed. Nita Lubin looked at him shrewdly. "You are hungry, Darius—more than I ever realized. Well, I still say that's no bad thing. I'm in this for profit myself, and so is Alexis. You go up front and help him, and let me check your calculations."
     "They'll be right," said Regulo. He turned quickly and left the cabin, before Nita Lubin could speak further.

     The first stages of the orbit transfer were following the classical pattern that Alexis Galley had pioneered more than twenty years earlier. First the shape of the asteroid was mapped and recorded from multiple angle images. Next came the detailed mass distribution calculated from analysis of seismic data. That determined the place where powerful explosive pellets would be sited in bore holes drilled deep into the rock. Even with these they would gain only an approximate distribution of the internal densities, but that was still their best source of information on the amounts of ammonia, solid carbon dioxide, water and methane ice inside the asteroid—the source of the reaction mass that would power the transfer of the fragment to Earth orbit.
     Galley and Regulo were at the computer, working together on the computation of the drive placings. As volatiles were consumed and expelled in flight, the center of mass and moments of inertia of the remaining rock would change. The drive thrust had to remain exactly through the changing center of mass, or the whole planetoid would begin to rotate under the applied torque.
     "See now why I'm against your damned hyperbolic fly-by?" grumbled Galley. "When you send anything that close to the Sun, the boil-off rate goes crazy. You lose a good fraction of your volatiles in just a few hours if you go in near enough. That's going to ruin the center-of-mass calculation. We never run into that sort of problem with an elliptic transfer, but now we have to think about it."
     "We can allow for it," said Regulo. His voice was confident. "It's just a matter of a little more calculation. I'll work out the solar flux as a function of our time in orbit, and that will give us all the boil-off information that we need."
     "Oh, I'm not saying we can't do it." Alexis Galley shook his head. "Only that it's a pain, and we'll lose another day while we're at it."
     "Look, I'm not asking you to do it. I'll be quite happy to handle all the computation."
     The older man looked at Regulo calmly. "Now then, Darius, just cool off. I'm not saying you don't take your share of the work, and more. I'm just saying that I still don't care for this whole thing. I've only flown one hyperbolic in my whole life, and that was in an emergency medical ship with unlimited thrust. We weren't trying to steer a billion tons of rock along with us, either. This is a tricky business, one you don't jump into without a decent amount of thought. If you're going to work on the calculations, I'll go out on the rock and take another look at the position of the drive placings."
     "I'd like to help on that, too. I've never seen it done before, and I want to learn how. Don't worry about the boil-off calculations," Regulo added quickly, seeing Galley's doubtful look. "I'll work those up as soon as we come back into the ship."
     "All right." Galley paused for a second, then nodded his head approvingly. "I'll say this for you, Darius, I've never had a junior man as keen to learn every single thing about this business. Come on, let's get our suits on. Time's a-running."
     The Alberich was moored on a short cable, a few meters from the asteroid. The difference in the natural orbits of the two bodies was infinitesimal, barely enough to hold the tether taut. The two men drifted slowly across to the rock and Galley began his careful examination of its surface.
     "Here's a good example," he said after a few moments, his voice loud over the suit phone. "When you first look at this location you think it's perfect. There's solid rock to secure a drive to, and you can see the volatiles right on the surface. But take a look at the mass distribution." Galley flashed part of the computed interior structure of the planetoid onto the suit video. "See that? The volatiles peter out just a few meters below the surface. Now, compare it with that position over to sunward. There's a real vein of volatiles there, and the mooring is just as good." Galley peered closely at the cratered surface, lit by the harsh, slanting rays of the distant Sun. "This looks like a fine one. There's enough reaction mass in that vein to do us some real good."
     Regulo was studying the video display. "I thought you told me that this mass distribution was just an approximation."
     "It is." Galley gave a brief bark of a laugh. "Sometimes you get a surprise, no matter how much thinking you do ahead of time. But the approximation is still the best information we have, so there's no sense in ignoring it unless we actually see something on the surface to tell us more. That's one reason we came out here." Galley switched in the ship's circuit. "Nita? Give us that composition read-out, would you?"
     He bent forward while the signal was being read through to the suits, and tapped the rock close to their feet. "Here's an example of what I was saying. I know there's a good amount of ferromagnetics under us, just from the strength of the magnetic clamps in the suit. You couldn't see that from the data we have on the ship, right? I don't know what else we've got here, either. I'd hate to throw away a lump of platinum, just to make a hole setting for a drive."
     The two men moved slowly across the surface of the rock, examining each possible site carefully while Galley offered a running commentary on his selection logic. It took a long time, and almost four hours passed before Alexis Galley picked the last of the seven places that he wanted. He patiently answered Regulo's continuous stream of questions.
     "We don't usually need to be this careful," he said. "But this one's an awkward shape—too long and thin."
     "You're afraid it might start to tumble?"
     "It has that tendency. The closer the shape of the rock to spherical, the less we have to worry about rotational instabilities. This one is almost twice as long as it is wide. We'll be all right, though. With those drive placings, we'll have no problem unless you find really big values for the boil-off mass. I'll be interested to see what the temperatures run out here during perihelion fly-by. Up near the thousand mark, for my guess."
     The two men had begun to drift slowly back towards the Alberich. Regulo noted the easy control of small body movements and the tiny, almost unconscious use of the suit jets as Alexis Galley controlled his position and attitude. He did his best to mimic the older man's actions.
     "Fly-by will go really fast," he said. "I don't think we'll spend more than two weeks inside the orbit of Mercury, in-bound and out-bound. The rock will get hot, but there's no harm in that—and it won't be for long."
     He turned his head and stared through the faceplate of the suit at the distant Sun. Still two hundred and fifty million miles away, it seemed small and strange, a dazzling, golden ornament in the black sky. Galley had stopped and was following his look.
     "Come on, Darius," he grunted. "You'll be getting your belly-full of that in another month or two. Let's get those calculations done and see to the drives. After that, you'll have all the time in the world for Sun-watching. But I have to say, the sooner we get through with this whole thing and are in Earth orbit, the better I'll be pleased."
     The drives set in the surface of the asteroid had finished their first spell of work long ago. Now they sat idle. They would not be needed again until the time came to decelerate into Earth orbit. The Alberich, still tethered to the rock, was falling with it, steadily and ever faster, toward the Sun. They were past Venus, past Mercury, plunging to perihelion. Darius Regulo, magnetic clamps holding him firmly to the surface of the planetoid, paused in his work to take a quick look at the solar primary. It had swollen steadily since they left the Asteroid Belt. Now it was ten times its former size and dominated the sky.
     "Come on, move it." Nita's voice came suddenly over the suit phone. She must have been watching on the external viewing screen. "Don't hang about out there. We'll be separating the Alberich from the asteroid in less than two hours."
     "On our way," Regulo said. "I just finished checking the last drive. They've all come through first impulse well. Unless Alexis disagrees with some of my data, I don't see a reason to change any of the settings before we use them again." He looked closely at the rock surface beneath his feet. "I'd say we're getting about our predicted amount of boil-off from the surface here."
     "And it's getting hotter than hell." That was Galley's voice, grumbling over the suit circuit. He was standing on the rock, close to the tether point that connected the Alberich to the asteroid. "I'm showing contact temperatures of over five hundred Kelvins, going up every minute. Come on, Darius, put the lid on it and let's get out of here."
     "I'll be right with you." Regulo bent to clamp the protective cover over the last of the drive units. It was a little tricky getting the fit to the asteroid's rough surface. He crouched lower, frowning at the awkward bolts.
     He was carefully turning the last coupling when the tremor came. His attention was all on the clamp and he saw nothing—but the rock surface was suddenly shaking beneath his feet. Even as he felt the vibration, he knew that it was impossible. Earthquakes simply don't happen on tiny rock fragments only a couple of kilometers across.
     He straightened, and at the same moment there was a long, metallic screech over his suit phone. The Sun, which a moment ago had been shining in fiercely through his faceplate, was abruptly darkened by an obscuring cloud. He looked for the Alberich but it too had vanished within a glowing white nimbus.
     "Alexis! What's going on?"
     He waited. There was no reply over his phone. After a few seconds he saw the shape of the ship, appearing mysteriously through the fog. The fog. There could be no fog here, far from any possible form of atmosphere. Regulo set his course for the ship, using his jets as Alexis Galley had taught him. As he moved, his eyes scanned the surface of the rock looking for Galley himself. The other man had to be somewhere on the asteroid. There was no sign of him, but before Regulo was halfway to the ship tether point he was beginning to see a slight change to the familiar shape of the surface. Where he had last seen Galley there now stood a deep pit, gouged into the rock itself. A fuming gas, brightly lit by the glaring beams of the swollen Sun, was pouring out of its interior.
     The Alberich was still attached to the rock by its tether. Regulo propelled himself up to it and looked in dismay at the condition of the ship. The forward hull plates had been shattered, with a great boulder of dark rock embedded in the wall of the main cabin. He looked in through a broken port and saw Nita Lubin's body, unsuited, floating free against an inner bulkhead.
     Even while his mind was struggling to accept the reality of an impossible series of events, some deep faculty was coolly assessing all that he saw and seeking explanations. He looked for an instant at the face of the Sun. The photo-sensitive faceplate of the suit darkened immediately, so that he could see nothing in the whole universe but that broad and burning face. The Alberich and its cargo were still falling towards it at better than thirty miles a second.
     What were the last words he had heard from Alexis Galley? . . . over five hundred Kelvins, going up every minute. Somehow, that had to be the key. A hundred and thirty degrees above the boiling point of water, almost four hundred degrees above the boiling point of methane. The surface of the asteroid had been cooking hotter and hotter in that unrelenting Sun, vaporizing the volatiles beneath. The pressure of the trapped gases forming there had increased and increased . . . until at last some critical value had been reached. Part of the rock had fractured under the intolerable stress. Fragments had been propelled out by the expanding gases, into the body of Alexis Galley, into the hanging target of the Alberich. All that had saved Regulo had been luck, his position on the asteroid and distance from the explosion.
     But saved for what? Regulo looked about him with a sickening realization of his own plight. The ship was a total wreck, he had known that as soon as he saw it. There was no way that it could be powered up to take him away to a safe orbit. The automatic alarm system should have triggered as soon as the ship's internal condition became unable to support human life. Regulo tuned quickly to the distress frequencies and heard the electronic scream as the ship blared and roared its high-frequency Mayday across the System. The signal would already be activating the monitors far out beyond Mercury, but that would be of no use to him. When the ship had swung past the Sun and out to the cooler regions of the Inner System, others would come and recover the hulk and its valuable cargo. But that would be too late for Regulo. At the moment, the Alberich was as unreachable by outside assistance as if it were sitting on the blinding photosphere of the Sun itself.
     After those first few moments of animal panic, Darius Regulo steadied. In spite of the furnace looming ahead of him, he felt cool and analytical. What were his options?
     The Alberich was available—but he had calculated long since that the ship's refrigeration system could not support a tolerable temperature through a perihelion transit of two and a quarter million kilometers. If he stayed with the ship he would quietly broil to death. He stared again at the Sun. Already it seemed bigger than ever before. In imagination, those fierce rays were lancing through his puny suit, pushing his refrigeration system inexorably towards its final overload. He could feel sweat trickling down his neck and chest, the body's own primitive protest at the worsening conditions surrounding it.
     He could open the suit and end it now. That would be a quicker and more merciful death, but he was not ready for it.
     Regulo entered the Alberich through its useless air lock. First he went to the communicator and sent out to the listening emergency stations a brief and precise description of his situation. He added a summary of what he intended to do, then went to the supply lockers and took out an armful of air tanks, jet packs, and emergency rations. The latter, he felt, had to be thought of as an expression of optimism. From the medical locker he took all the stimulants that he could find.
     He performed a brief calculation on his suit computer, confirming his first estimate. Somehow he would have to survive for eight days. If he could do that, perihelion would be well past and the Alberich again cool enough to tolerate.
     Dragging the bundle of supplies along behind him, Regulo left the ship and propelled himself slowly back to the asteroid. The explosion that destroyed the Alberich and killed Alexis and Nita had expelled enough material from the rock to give it some angular momentum. It was turning slowly about its shortest axis. Regulo attached the supplies firmly to his suit, took a last look at the ruined ship, then went behind the rock and entered the deep, black shadow. He knew what he had to do. At three million kilometers, the Sun would stretch across more than twenty-five degrees of the sky. He had to stay close enough to the surface to remain within the shield of the cool umbra. That was his only protection against the roaring furnace on the other side of the asteroid.
     He felt cooler as soon as he passed into the shadow. That, he knew, was all psychological. It would take several minutes before his suit temperature dropped enough to make a perceptible difference.
     As he expected, there were first of all several hours of experiment. If he ventured too far from the surface, he lost the protection of the cone of shadow. Too close, and he was forced to move outward when the long axis of the asymmetrical rock swung around towards him in its steady rotation. He found the pattern of movements that would minimize his use of the jet packs and settled in for a long, lonely siege.
     There was ample time to look back and study the mistakes that they had made. With such a close swing-by of the Sun, they should have kept the rock turning. That would have given an even heating on all sides and also a chance for heat to radiate away again into space. And they should have put the Alberich at least a few kilometers away from the asteroid, to reduce its vulnerability to accidents. Regulo reached a grim conclusion. Alexis Galley had been right: with all his experience, he had not known how to handle the hyperbolic swing-by. Regulo would learn that—if he survived.

     After the first twelve hours his actions became automatic. Move always to keep in the shadow. Eat and drink a little—he had to force himself to do that, because his appetite was gone completely. Check the fuel in the jet assembly. And take a stimulant every six hours.
     He could not afford to sleep. Not with the menace of the Sun so ready to engulf him if he failed to hide from it. But sleep was the tempter. After sixty hours his whole body ached for it with a physical lust that surpassed any desire he had ever felt. The stimulants forced the mind to remain awake, but they did so without the body's consent. Fatigue crushed him, sucked the marrow from his bones, drained his blood.
     After eighty-five hours he began to hallucinate. Alexis and Nita were hanging there next to him, unsuited. Their empty eyes were full of reproach as they floated out into the golden sunlight and waved and beckoned for him to follow them, to leave the dead shadows.
     Soon after the hundredth hour, he fell briefly asleep. The flood of molten gold wakened him, splashing in through his faceplate. He had drifted outside the guardian shadow of the asteroid, and although his visor had darkened to its maximum it was useless against the stabbing, shattering light. He squeezed his eyes shut. The orb was still visible, burning a bloody, awful red through his eyelids.
     He must be close to perihelion. The Sun had become a giant torch surrounded by huge hydrogen flares. The asteroid had dipped well inside the solar corona itself, hurtling in to its point of closest approach. Light filled the world. Regulo writhed in its grip, turning desperately about to seek the shelter of the rock. The asteroid, the stars, the ship, all were invisible now, forced to insignificance by the tyrannous power of the great solar crucible.
     Instinctively, Regulo began to jet back and forth, firing his thrusts at random in a desperate cast for the shadow. At last he found it by pure luck, a dark crescent bitten from the flaring disc. He moved towards it. Back once more in the blessed darkness, he hung seared and gasping in his overloaded suit.
     "No." His voice was hoarse and choking. "Not this time, you bastard. You don't get me this time." He glared through bloodshot eyes at the surface of the asteroid, as though seeing right through it to the burning orb beyond. "You won't get me. Ever. You think you're the boss of everything, but I'll prove you're not. I'll beat you. I'll outlast you."
     Even as he spoke, an icy trickle of rage dribbled into his brain, washing away the fatigue and the terror. He knew that his face was beginning to sear and blister from the harsh sleet of radiation that he had experienced, but he was able to ignore it. All that mattered was the battle ahead. He stared about him.
     On each side of the asteroid a stream of ionized gases was roaring past, boiled out from the sunward surface and driven by light pressure. The halo that they formed scattered the Sun's rays to make a ghostly sheath of green, blue and white, flickering all around him. A hundred meters below, the dark surface of the rock was beginning to bubble and smoke as it slowly turned, roasting in the solar glare like a joint on a spit. He stared at it, cold-eyed. He would have to keep well clear of that, now and for the next seventy hours. No matter. It was just one more reason why he could not afford to fall asleep again. He would not sleep again.

(ed note: end of flashback, return to present)

     "They never found any trace of Alexis Galley, and of course the other crew member was dead. The verdict on the whole thing was an unfortunate accident, with no one to blame. When they brought the asteroid in to Earth orbit, Regulo owned all of it—survivors on the mining teams always willed the finds to each other if some of them were killed. And Regulo had stayed with the rock, otherwise the value would have been shared with the crew who salvaged the Alberich."
     Corrie was silent for a few moments as she watched the display with its final landing instructions for the field at Way Down.
     "That was enough to give him the financing for his first transportation company," she went on. "He pioneered the techniques for the hyperbolic orbit and cut all the transit times by a factor of two. But he never flew another hyperbolic himself. He has never been closer to the Sun than the orbit of Earth. And he will not tolerate any form of intense light. It upsets him, makes him almost unstable. It's the only thing that ever has that effect on him."

From THE WEB BETWEEN THE WORLDS by Charles Sheffield (1979)

      At twenty I gave up my UN citizenship to become a Belter. I wanted stars, and the Belt government holds title to most of the solar system. There are fabulous riches in the rocks, riches belonging to a scattered civilization of a few hundred thousand Belters; and I wanted my share of that, too.

     It wasn’t easy. I wouldn’t be eligible for a singleship license for ten years. Meanwhile I would be working for others, and learning to avoid mistakes before they killed me. Half the flatlanders who join the Belt die in space before they can earn their licenses.

     I mined tin on Mercury and exotic chemicals from Jupiter’s atmosphere. I hauled ice from Saturn’s rings and quicksilver from Europa. One year our pilot made a mistake pulling up to a new rock, and we damn near had to walk home. Cubes Forsythe was with us then. He managed to fix the com laser, and aim it at Icarus to bring us help. Another time the mechanic who did the maintenance job on our ship forgot to replace an absorber, and we all got roaring drunk on the alcohol that built up in our breathing-air. The three of us caught the mechanic six months later. I hear he lived.

     Most of the time I was part of a three-man crew. The members changed constantly. When Owen Jennison joined us he replaced a man who had finally earned his singleship license, and couldn’t wait to start hunting rocks on his own. He was too eager. I learned later that he’d made one round trip and half of another.

     Owen was my age, but more experienced, a Belter born and bred. His blue eyes and blond cockatoo’s crest were startling against the dark of his Belter tan, the tan that ended so abruptly where his neck ring cut off the space-intense sunlight his helmet let through. He was permanently chubby, but in tree fall it was as if he’d been born with wings. I took to copying his way of moving, much to Cubes’ amusement.

     I didn’t make my own mistake until I was twenty-six.

     We were using bombs to put a rock in a new orbit. A contract job. The technique is older than fusion drives, as old as early Belt colonization, and it’s still cheaper and faster than using a ship’s drive to tow the rock. You use industrial fusion bombs, small and clean, and you set them so that each explosion deepens the crater to channel the force of later blasts.

     We’d set four blasts already, four white fireballs that swelled and faded as they rose. When the fifth blast went off we were hovering nearby on the other side of the rock.

     The fifth blast shattered the rock.

     Cubes had set the bomb. My own mistake was a shared one, because any of the three of us should have had the sense to take off right then. Instead, we watched, cursing, as valuable oxygen-bearing rock became near-valueless shards. We watched the shards spread slowly into a cloud … and while we watched, one fast-moving shard reached us. Moving too slowly to vaporize when it hit, it nonetheless sheared through a triple crystal-iron hull, slashed through my upper arm, and pinned Cubes Forsythe to a wall by his heart.

     A cool blue mood settled on me, and I remembered …

     … Owen Jennison lounging on a corner of my hospital bed, telling me of the trip back. I couldn’t remember anything after that rock had sheared through my arm.

     I should have bled to death in seconds. Owen hadn’t given me the chance. The wound was ragged; Owen had sliced it clean to the shoulder with one swipe of a com laser. Then he’d tied a length of fiberglass curtain over the flat surface and knotted it tight under my remaining armpit. He told me about putting me under two atmospheres of pure oxygen as a substitute for replacing the blood I’d lost. He told me how he’d reset the fusion drive for four gees to get me back in time. By rights we should have gone up in a cloud of starfire and glory.

     “So there goes my reputation. The whole Belt knows how I rewired our drive. A lot of ’em figure if I’m stupid enough to risk my own life like that, I’d risk theirs too.”

     “So you’re not safe to travel with.”

     “Just so. They’re starting to call me Four Gee Jennison.”

From DEATH BY ECSTASY by Larry Niven (1969)

      The mountain was spinning.
     Not dizzily, not even rapidly, but very perceptibly, the great mass of jagged rock was turning on its axis.
     Captain St. Simon scowled at it. "By damn, Jules," he said, "if you can see 'em spinning, it's too damn fast!" He expected no answer, and got none.
     He tapped the drive pedal gently with his right foot, his gaze shifting alternately from the instrument board to the looming hulk of stone before him. As the little spacecraft moved in closer, he tapped the reverse pedal with his left foot. He was now ten meters from the surface of the asteroid. It was moving, all right. "Well, Jules," he said in his most commanding voice, "we'll see just how fast she's moving. Prepare to fire Torpedo Number One!"
     "Yassuh, boss! Yassuh, Cap'n Sain' Simon, suh! All ready on the firin' line!"
     He touched a button with his right thumb. The ship quivered almost imperceptibly as a jet of liquid leaped from the gun mounted in the nose of the ship. At the same time, he hit the reverse pedal and backed the ship away from the asteroid's surface. No point getting any more gunk on the hull than necessary.
     The jet of liquid struck the surface of the rotating mountain and splashed, leaving a big splotch of silvery glitter. Even in the vacuum of space, the silicone-based solvents of the paint vehicle took time to boil off.
     "How's that for pinpoint accuracy, Jules?"
     "Veddy good, M'lud. Top hole, if I may say so, m'lud."
     "You may." He jockeyed the little spacecraft around until he was reasonably stationary with respect to the great hunk of whirling rock and had the silver-white blotch centered on the crosshairs of the peeper in front of him. Then he punched the button that started the timer and waited for the silver spot to come round again.
     The asteroid was roughly spherical—which was unusual, but not remarkable. The radar gave him the distance from the surface of the asteroid, and he measured the diameter and punched it through the calculator. "Observe," he said in a dry, didactic voice. "The diameter is on the order of five times ten to the fourteenth micromicrons." He kept punching at the calculator. "If we assume a mean density of two point six six times ten to the minus thirty-sixth metric tons per cubic micromicron, we attain a mean mass of some one point seven four times ten to the eleventh kilograms." More punching, while he kept his eye on the meteorite, waiting for the spot to show up again. "And that, my dear Jules, gives us a surface gravity of approximately two times ten to the minus sixth standard gees."
     "Jawohl, Herr Oberstleutnant."
     "Und zo, mine dear Chules, ve haff at least der grave zuspicion dot der zurface gravity iss less dan der zentrifugal force at der eqvator! Nein? Ja! Zo."
     "Jawohl, Herr Konzertmeister."
     Then there was a long, silent wait, while the asteroid went its leisurely way around its own axis.
     "There it comes," said Captain St. Simon. He kept his eyes on the crosshair of the peeper, one hand over the timer button. When the silver splotch drifted by the crosshair, he punched the stop button and looked at the indicator.
     "Sixteen minutes, forty seconds. How handy." He punched at the calculator again. "Ah! You see, Jules! Just as we suspected! Negative gees at the surface, on the equator, comes to ten to the minus third standard gees—almost exactly one centimeter per second squared. So?"
     "Ah, so, honorabu copton! Is somesing rike five hundred times as great as gravitationar attraction, is not so?"
     "Sukiyaki, my dear chap, sometimes your brilliance amazes me."
     Well, at least it meant that there would be no loose rubble on the surface. It would have been tossed off long ago by the centrifugal force, flying off on a tangent to become more of the tiny rubble of the belt. Perhaps "flying" wasn't exactly the right word, though, when applied to a velocity of less than one centimeter per second. Drifting off, then.
     "What do you think, Jules?" said St. Simon.
     "Waal, Ah reckon we can do it, cap'n. Ef'n we go to the one o' them thar poles ... well, let's see—" He leaned over and punched more figures into the calculator. "Ain't that purty! 'Cordin' ter this, thar's a spot at each pole, 'bout a meter in diameter, whar the gee-pull is greater than the centry-foogle force!"
     Captain St. Simon looked at the figures on the calculator. The forces, in any case, were negligibly small. On Earth, where the surface gravity was ninety-eight per cent of a Standard Gee, St. Simon weighed close to two hundred pounds. Discounting the spin, he would weigh about four ten-thousandths of a pound on the asteroid he was inspecting. The spin at the equator would try to push him off with a force of about two tenths of a pound.
     But a man who didn't take those forces into account could get himself killed in the Belt.
     "Very well, Jules," he said, "we'll inspect the poles."
     "Do you think they vill velcome us in Kraukau, Herr Erzbischof?"

     The area around the North Pole—defined as that pole from which the body appears to be spinning counterclockwise—looked more suitable for operations than the South Pole. Theoretically, St. Simon could have stopped the spin, but that would have required an energy expenditure of some twenty-three thousand kilowatt-hours in the first place, and it would have required an anchor to be set somewhere on the equator. Since his purpose in landing on the asteroid was to set just such an anchor, stopping the spin would be a waste of time and energy.
     Captain St. Simon positioned his little spacecraft a couple of meters above the North Pole. It would take better than six minutes to fall that far, so he had plenty of time. "Perhaps a boarding party, Mr. Christian! On the double!"
     "Aye, sir! On the double it is, sir!"
     St. Simon pushed himself over to the locker, took out his vacuum suit, and climbed into it. After checking it thoroughly, he said: "Prepare to evacuate main control room, Mr. Christian!"
     "Aye, aye, Sir! All prepared and ready. I hope."
     Captain St. Simon looked around to make sure he hadn't left a bottle of coffee sitting somewhere. He'd done that once, and the stuff had boiled out all over everywhere when he pulled the air out of the little room. Nope, no coffee. No obstacles to turning on the pump. He thumbed the button, and the pumps started to whine. The whine built up to a crescendo, then began to die away until finally it could only be felt through the walls or floor. The air was gone.
     Then he checked the manometer to make sure that most of the air had actually been pumped back into the reserve tanks. Satisfied, he touched the button that would open the door. There was a faint jar as the remaining wisps of air shot out into the vacuum of space.
     St. Simon sat back down at the controls and carefully repositioned the ship. It was now less than a meter from the surface. He pushed himself over to the open door and looked out.
     He clipped one end of his safety cable to the steel eye-bolt at the edge of the door. "Fasten on carefully, Jules," he said. "We don't want to lose anything."
     "Like what, mon capitain?" (my captain)
     "Like this spaceship, mon petit tête de mouton." (my little sheep's head)
     "Ah, but no, my old and raw; we could not afford to lose the so-dear Nancy Bell, could we?"
     The other end of the long cable was connected to the belt of the suit. Then St. Simon launched himself out the open door toward the surface of the planetoid. The ship began to drift—very slowly, but not so slowly as it had been falling—off in the other direction.
     He had picked the spot he was aiming for. There was a jagged hunk of rock sticking out that looked as though it would make a good handhold. Right nearby, there was a fairly smooth spot that would do to brake his "fall". He struck it with his palm and took up the slight shock with his elbow while his other hand grasped the outcropping.
     He had not pushed himself very hard. There is not much weathering on the surface of an asteroid. Micro-meteorites soften the contours of the rock a little over the millions of millennia, but not much, since the debris in the Belt all has roughly the same velocity. Collisions do occur, but they aren't the violent smashes that make the brilliant meteor displays of Earth. (And there is still a standing argument among the men of the Belt as to whether that sort of action can be called "weathering".) Most of the collisions tend to cause fracturing of the surface, which results in jagged edges. A man in a vacuum suit does not push himself against a surface like that with any great velocity.
     St. Simon knew to a nicety that he could propel himself against a bed of nails and broken glass at just the right velocity to be able to stop himself without so much as scratching his glove. And he could see that there was no ragged stuff on the spot he had selected. The slanting rays of the sun would have made them stand out in relief.
     Now he was clinging to the surface of the mountain of rock like a bug on the side of a cliff. On a nickel-iron asteroid, he could have walked around on the surface, using the magnetic soles of his vacuum suit. But silicate rock is notably lacking in response to that attractive force. No soul, maybe.
     But directly and indirectly, that lack of response to magnetic forces was the reason for St. Simon's crawling around on the surface of that asteroid. Directly, because there was no other way he could move about on a nonmetallic asteroid. Indirectly, because there was no way the big space tugs could get a grip on such an asteroid, either.
     The nickel-iron brutes were a dead cinch to haul off to the smelters. All a space tug had to do was latch on to one of them with a magnetic grapple and start hauling. There was no such simple answer for the silicate rocks.
     The nickel-iron asteroids were necessary. They supplied the building material and the major export of the Belt cities. They averaged around eighty to ninety per cent iron, anywhere from five to twenty per cent nickel, and perhaps half a per cent cobalt, with smatterings of phosphorous, sulfur, carbon, copper, and chromium. Necessary—but not sufficient.
     The silicate rocks ran only about twenty-five per cent iron—in the form of nonmagnetic compounds. They averaged eighteen per cent silicon, fourteen per cent magnesium, between one and one point five per cent each of aluminum, nickel, and calcium, and good-sized dollops of sodium, chromium, phosphorous, manganese, cobalt, potassium, and titanium.
     But more important than these, as far as the immediate needs of the Belt cities were concerned, was a big, whopping thirty-six per cent oxygen. In the Belt cities, they had soon learned that, physically speaking, the stuff of life was not bread. And no matter how carefully oxygen is conserved, no process is one hundred per cent efficient. There will be leakage into space, and that which is lost must be replaced.
     There is plenty of oxygen locked up in those silicates; the problem is towing them to the processing plants where the stuff can be extracted.
     Captain St. Simon's job was simple. All he had to do was sink an anchor into the asteroid so that the space tugs could get a grip on it. Once he had done that, the rest of the job was up to the tug crew.
     He crawled across the face of the floating mountain. At the spot where the North Pole was, he braced himself and then took a quick look around at the Nancy Bell. She wasn't moving very fast, he had plenty of time. He took a steel piton out of his tool pack, transferred it to his left hand, and took out a hammer. Then, working carefully, he hammered the piton into a narrow cleft in the rock. Three more of the steel spikes were hammered into the surface, forming a rough quadrilateral around the Pole.
     "That looks good enough to me, Jules," he said when he had finished. "Now that we have our little anchors, we can put the monster in."
     Then he grabbed his safety line, and pulled himself back to the Nancy Bell.
     The small craft had floated away from the asteroid a little, but not much. He repositioned it after he got the rocket drill out of the storage compartment.
     "Make way for the stovepipe!" he said as he pushed the drill ahead of him, out the door. This time, he pulled himself back to his drilling site by means of a cable which he had attached to one of the pitons.
     The setting up of the drill didn't take much time, but it was done with a great deal of care. He set the four-foot tube in the center of the quadrilateral formed by the pitons and braced it in position by attaching lines to the eyes on a detachable collar that encircled the drill. Once the drill started working, it wouldn't need bracing, but until it did, it had to be held down.
     All the time he worked, he kept his eyes on his lines and on his ship. The planetoid was turning under him, which made the ship appear to be circling slowly around his worksite. He had to make sure that his lines didn't get tangled or twisted while he was working.
     As he set up the bracing on the six-inch diameter drill, he sang a song that Kipling might have been startled to recognize.
     When the drill was firmly based on the surface of the planetoid, St. Simon hauled his way back to his ship along his safety line. Inside, he sat down in the control chair and backed well away from the slowly spinning hunk of rock. Now there was only one thin pair of wires stretching between his ship and the drill on the asteroid.
     When he was a good fifty meters away, he took one last look to make sure everything was as it should be.
     "Stand by for a broadside!"
     "Standing by, sir!"
     "You may fire when ready, Gridley!"
     "Aye, sir! Rockets away!" His forefinger descended on a button which sent a pulse of current through the pair of wires that trailed out the open door to the drill fifty meters away.
     A flare of light appeared on the top of the drill. Almost immediately, it developed into a tongue of rocket flame. Then a glow appeared at the base of the drill and flame began to billow out from beneath the tube. The drill began to sink into the surface, and the planetoid began to move ever so slowly.
     The drill was essentially a pair of opposed rockets. The upper one, which tried to push the drill into the surface of the planetoid, developed nearly forty per cent more thrust than the lower one. Thus, the lower one, which was trying to push the drill off the rock, was outmatched. It had to back up, if possible. And it was certainly possible; the exhaust flame of the lower rocket easily burrowed a hole that the rocket could back into, while the silicate rock boiled and vaporized in order to get out of the way.
     Soon there was no sign of the drill body itself. There was only a small volcano, spewing up gas and liquid from a hole in the rock. On the surface of a good-sized planet, the drill would have built up a little volcanic cone around the lip of the hole, but building a cone like that requires enough gravity to pull the hot matter back to the edge of the hole.
     The fireworks didn't last long. The drill wasn't built to go in too deep. A drill of that type could be built which would burrow its way right through a small planetoid, but that was hardly necessary for planting an anchor. Ten meters was quite enough.
     Now came the hard work.
     On the outside of the Nancy Bell, locked into place, was a specially-treated nickel-steel eye-bolt—thirty feet long and eight inches in diameter. There had been ten of them, just as there had been ten drills in the storage locker. Now the last drill had been used, and there was but one eye-bolt left. The Nancy Bell would have to go back for more supplies after this job.
     The anchor bolts had a mass of four metric tons each. Maneuvering them around, even when they were practically weightless, was no easy job.
     St. Simon again matched the velocity of the Nancy Bell with that of the planetoid, which had been accelerated by the drill's action. He positioned the ship above the hole which had been drilled into the huge rock. Not directly above it—rocket drills had been known to show spurts of life after they were supposed to be dead. St. Simon had timed the drill, and it had apparently behaved as it should, but there was no need to take chances.
     "Fire brigade, stand by!"
     "Fire brigade standing by, sir!"
     A nozzle came out of the nose of the Nancy Bell and peeped over the rim of the freshly-drilled hole.
     "Ready! Aim! Squirt!"
     A jet of kerosene-like fluosilicone oil shot down the shaft. When it had finished its work, there was little possibility that anything could happen at the bottom. Any unburned rocket fuel would have a hard time catching fire with that stuff soaking into it.
     "Ready to lower the boom, Mr. Christian!" bellowed St. Simon.
     "Aye, sir! Ready, sir!"
     "Lower away!"
     His fingers played rapidly over the control board.
     Outside the ship, the lower end of the great eye-bolt was released from its clamp, and a small piston gave it a little shove. In a long, slow, graceful arc, it swung away from the hull, swiveling around the pivot clamp that held the eye. The braking effect of the pivot clamp was precisely set to stop the eye-bolt when it was at right angles to the hull. Moving carefully, St. Simon maneuvered the ship until the far end of the bolt was directly over the shaft. Then he nudged the Nancy Bell sideways, pushing the bolt down into the planetoid. It grated a couple of times, but between the power of the ship and the mass of the planetoid, there was enough pressure to push it past the obstacles. The rocket drill and the eye-bolt had been designed to work together; the hole made by the first was only a trifle larger than the second. The anchor settled firmly into place.
     St. Simon released the clamps that held the eye-bolt to the hull of the ship, and backed away again. As he did, a power cord unreeled, for the eye-bolt was still connected to the vessel electrically.
     Several meters away, St. Simon pushed another button. There was no sound, but his practiced eye saw the eye of the anchor quiver. A small explosive charge, set in the buried end of the anchor, had detonated, expanding the far end of the bolt, wedging it firmly in the hole. At the same time, a piston had been forced up a small shaft in the center of the bolt, forcing a catalyst to mix with a fast-setting resin, and extruding the mixture out through half a dozen holes in the side of the bolt. When the stuff set, the anchor was locked securely to the sides of the shaft and thus to the planetoid itself.
     St. Simon waited for a few minutes to make sure the resin had set completely. Then he clambered outside again and attached a heavy towing cable to the eye of the anchor, which projected above the surface of the asteroid. Back inside the ship again, he slowly applied power. The cable straightened and pulled at the anchor as the Nancy Bell tried to get away from the asteroid.
     "Jules, old bunion," he said as he watched the needle of the tension gauge, "we have set her well."
     "Yes, m'lud. So it would appear, m'lud."
     St. Simon cut the power. "Very good, Jules. Now we shall see if the beeper is functioning as it should." He flipped a switch that turned on the finder pickup, then turned the selector to his own frequency band.
     Beep! said the radio importantly. Beep!
     The explosion had also triggered on a small but powerful transmitter built into the anchor. The tugs would be able to find the planetoid by following the beeps.
     "Ah, Jules! Success!"
     "Yes, m'lud. Success. For the tenth time in a row, this trip. And how many trips does this make?"
     "Ah, but who's counting? Think of the money!"
     "And the monotony, m'lud. To say nothing of molasses, muchness, and other things that begin with an M."
     "Quite so, Jules; quite so. Well, let's detach the towing cable and be on our way."
     "Whither, m'lud, Vesta?"
     "I rather thought Pallas this time, old thimble."
     "Still, m'lud, Vesta—"
     "Pallas, Jules."
     "Hum, hi, ho," said Captain St. Simon thoughtfully. "Pallas?"
     The argument continued while the tow cable was detached from the freshly-placed anchor, and while the air was being let back into the control chamber, and while St. Simon divested himself of his suit. Actually, although he would like to go to Vesta, it was out of the question. Energywise and timewise, Pallas was much closer.
     He settled back in the bucket seat and shot toward Pallas.

From ANCHORITE by Randall Garrett (1962)

Lunar Mining

On the one hand, the delta V cost to reach the asteroids or the Martian moons is quite a bit less than to reach the Lunar surface. On the other hand, transit times to the asteroids is measured in years, while transit to Luna is measured in days. It is a trade off.

The lunar poles contain valuable deposits of ice.

The entire surface of Luna is covered by a layer of regolith (the result of billions of years of meteorite strikes). It is several meters thick in the lunar mare regions, and ten or more meters thick in the older highland areas. The upper few centimeters are like dust, but by a depth of 30 cm it has become very compacted. The average grain size is about 60 μm but there is a mixing of larger rock fragments.

The point is that lunar mining can be done by just scooping up regolith.

A special type of lunar regolith is KREEP, so-named because it contains potassium K, rare earth elements REE and phosphorus P. It also contains uranium and thorium.

Another special type of regolith is pyroclastic deposits aka volcanic ash. Unlike other regoliths they contain significant volatiles, and when you are trying to extract oxygen from regolith it is easier to crush pyroclastic glass than it is to crush crystal silicates.

Titanium is useful for constructing rocket-powered vehicles due to its absurdly low mass for its strength. It can be found in Lunar Ilmenite ore, but currently there are no other known high-concentration sources (other than on Terra). Asteroids contain only microscopic fractions of titanium. On Luna a "High titanium basalt" is one with more than 6% titanium by weight, it can go up to 8%.

The lunar highland regoliths have high concentrations of aluminum, typically 10 to 18% by weight. Asteroids are lucky to have 1%. Aluminium is a splendid rocket framework material, and it can even be used as rocket fuel with oxygen.

All lunar rocks are about 20% silicon by weight, which is usefull for constructing solar power cells.

And yes, the regolith has absorbed the solar wind over the aeons. Fanatics think the absorbed helium-3 is a prime MacGuffinite, but the sad fact of the matter is that the concentration is so miniscule it really isn't worth it. It would be more profitable to try and extract gold from seawater. Seawater can have up to 44 parts-per-billion (ppb) of gold, lunar regolith has an average abundance of 4 ppb helium-3.


A place which (a) has things you need (b) stored in an economically removable form is a valuable resource. But what does the Moon have?

     Why mine the Moon—or any planet-sized body—at all? They’re beset with such inconveniences as deep gravity wells and atmospheres, and you can‘t do more than scratch the surface; most of the volume of the planet is inaccessible. Oh, sure, we’ll build mass drivers on the Moon and scoop up bags of lunar dirt—nothing fancy, we’re just looking for common elements. And early in the space industrialization effort we’ll have to bring up lots of material from Earth—volatiles (water, chlorine, carbon) and rare metals (copper, moly, vanadium) to supplement the stuff the lunar dirt’s deficient in. But ev’body knows the asteroids are where it’s at, ultimately. They’re easy to get to; no gravity well and lots of surface area—you can even move them bodily (at least the little ones). They’re also rich in some elements the Moon’s crust lacks, particularly the volatile elements: the carbon, hydrogen, and nitrogen for life support and industrial processes.

     So goes the emerging conventional wisdom. And, admittedly, there’s a lot of truth in it: gravity wells are awkward, and most of the planet is effectively beyond your reach. And atmospheres, if present, are a real drag—you can’t even use mass drivers to throw stuff off the surface, but have to get involved with propelled transport vehicles, with attendant hemorrhages in economy. (An apt terrestrial analogy, due to T. A. Heppenheimer, is the difference in cost between moving bulk goods by pipeline versus by airplane.) However, there’s a major point to consider before completely writing off planets as economic sources of raw materials.

     Planets are differentiated bodies (no, Virginia, nothing to do with calculus). “Differentiated,” in this context, means chemically and physically differentiated—fractionated, if you will. Consider planetesimals formed from the solar-nebula condensates: blobs of nickel-iron alloy; droplets (“chondrules”) of refractory (opposite of “volatile”) silicates; low-temperature carbonaceous material. Stir together a heterogeneous, planet-sized mixture of this material (in different proportions, granted; heavier on the metal for Mercury, heavier on the rocky material for Mars; very light on the volatiles for the Moon—but all still mixtures). What happens? Well, first the mixture becomes hot from the energy of gravitational infall and the decay of natural radioactive elements. The planetary body melts, at least in part, and then physically and chemically separates on a planetary scale: the heavy stuff (iron) sinks to the center while the light material (silicates—“slag” and volatile elements) rises to the surface.

     Planetary scale chemical differentiation has another consequence: it gives a chance for those parts-per-million (or billion) rare elements to aggregate into more substantial, albeit localized, concentrations. Rare elements can be broadly divided into two types, “dispersed” and “incompatible.” Dispersed elements are sufficiently similar in chemistry to a common element that they form no minerals of their own—they are “dispersed,” and replace that common element in its minerals. Examples are rubidium (which replaces potassium in potassium minerals), gallium (which follows aluminum), and bromine (which follows chlorine). Dispersed elements don’t ever become very concentrated in nature; generally, they are recovered as by-products when refining other elements.

     Incompatible elements, in contrast, are iconoclasts; they don’t fit well into any of the common minerals, but form their own—with important economic consequences. Consider, for example, a cooling mass of magma (molten rock). As it solidifies, the incompatible elements become more and more concentrated in the residual melt; finally, after most of the magma is solid, they become sufficiently concentrated to form their own minerals. The minerals end up as distinct veins in a much larger body of rock.

     Now the punchline: most of the familiar metals—gold, copper, tungsten, beryllium, tin, lead, zinc—are incompatible elements. In fact, these metals are familiar, some known since antiquity, because they become concentrated by geologic processes.

     Planetary differentiation works the other way, too. On the Earth, for example, a number of elements are much rarer in the crust than their cosmic abundances, because their chemistry is such that they have tended to “partition” (geochemist’s jargon; it means “separate into preferentially,” which is why “partition” is easier) into the Earth’s nickel-iron core. These elements are “siderophile” (“iron-loving,” if you’ve forgotten your Greek); siderophile elements that are greatly depleted in the crust include such valuable commodities as nickel, cobalt, and platinum. To recover these elements, we want a non-differentiated body, like a metallic asteroid—but therein lies another article.

     So the large-scale chemical fractionation that accompanies the formation of a planet concentrates incompatible elements in the planet’s crust (at least, those incompatible elements that didn’t end up in the core instead). But that just sets the stage: planets are huge bodies, and natural radioactive elements in that enormous volume produce at lot of heat over geologic time. As this heat builds up and slowly works its way out, it keeps the planet active for a long, long time. Several things happen. First, rocks at depth “partially” melt; that is, the low-melting fraction becomes liquid, and the bodies of magma so formed work their way upward by buoyancy, like bubbles in a beer. The magmas may either crystallize at depth (and fractionate again while they crystallize), or they may reach the surface to be extruded as lava (and again undergo fractionation). Also a small proportion of the planet’s heat gets transformed into mechanical work, or “tectonics” in geologic jargon: uplift, mountain-building, faulting. On the Earth, plate tectonics continually recycles crust. “Plates” are formed as new sea floor oozes out at mid-ocean ridges; they are consumed at “subduction zones,” where old sea floor, with an accumulated burden of sediments riding piggyback, plunges back into the mantle at oceanic trenches. The down-going slab of cold rock is in turn heated and partially melted (the lavas and ash of Mt. St. Helens, like all the Cascade volcanoes, are derived from the partial melting of the subducting Juan de Fuca plate thirty or forty kilometers below the surface). ln all this activity the continents are passively rafted back and forth, split up, fused together, eroded, and the sediments subducted, only to be melted and pop back to the surface with igneous activity. A planet like the Earth is a huge chemical fractionating plant.

     As you might have gathered from all this, Earth is well set with ore-forming processes. Not only does plate tectonics constantly stir the outermost 100 km or so of our planet, but the Earth’s atmosphere and ocean also supply a bewildering variety of fractionation processes. Purely physical separation occurs: placer deposits formed by running water. Chemical separation occurs: compounds precipitated from aqueous solution in the ocean, in sedimentary rock, in lakes, ponds, and marshes. In fact, the interaction between the multitude of geologic processes increases their effectiveness. For example, erosion, a physical process, is a conveyor that continually pours broken, uplifted rock back into the tectonic recycler, and the material becomes further chemically and physically fractionated as it’s carried along. The ultimate deposits on the sea floor are then carried down in a subduction zone to be melted and extruded anew. Or sedimentary rock can be chemically (or biologically—much separation is expedited by the activities of living things) pre-enriched in some element; upon being “cooked” by burial, or by an intruded magma, the element can be mobilized and concentrated into distinct veins.

     That leads into another aspect of Earth’s ore formation: even igneous ore-forming processes (well, many of them) rely on Ealth’s water. Earthly magmas are generally saturated with H2O; a silicate melt at hundreds of degrees centigrade can contain a few weight percent water. As the magma cools and solidifies, the incompatible elements accumulate in a water-rich residual melt. Eventually a separate “fluid phase” forms, essentially a dense, superheated steam charged with a host of other elements. This fluid phase can be injected into the “country rock” around the intrusion to cool, segregate, and finally crystallize. The whole sequence describes the genesis of a “hydrothermal deposit,” in geologist’s lingo, and such deposits are extremely important mechanisms for forming terrestrial ores. Those veins of quartz seamed with gold that you read about in Western novels are the result of hydrothermal processes.

     By the way, what is “ore,” technically, now that l’ve started using the word? As defined in the American Geological Institute’s Glossary of Geology (1978 edition), an “ore” is (a) “The naturally occurring material from which a mineral or minerals of economic value can be extracted at a reasonable profit. Also, the mineral(s) thus extracted. The term is generally but not always used to refer to metalliferous material…”. Thus “ore” is an economic term—only! If it is an economically useful concentration of (generally) metallic element(s), it is “ore.” By definition. The word carries no connotation of the particular geologic process that happened to cause the concentration. We can properly use the word “ore” to describe what we mine on the Earth, on the Moon, or anywhere else.

     In contrast to the Earth, the Moon doesn’t stack up well at all in terms of ore-forming processes. The Moon is nearly—though possibly not completely—dead volcanically; it is airless and waterless; and it is tectonically inert. The crust of the Moon is thick and rigid, not thin and mobile like the Earth’s; plate tectonics does not stir the crust continually over geologic time. Finally, more than being just airless and waterless, lunar rocks are drastically depleted in volatile elements—elements, including carbon, hydrogen, chlorine, and nitrogen, that have low boiling points and that on the Earth are concentrated in the ocean and atmosphere. Even metallic elements with low melting or boiling points, such as lead, are much rarer on the Moon.

     This lack of volatiles is a double whammy. Not only are many of the volatile elements vital for life support and space industry, they are vital to many ore-forming processes! On the Moon there are no placer deposits, winnowed by running water; no metal-rich precipitates from aqueous solutions in sedimentary rocks; no chemical concentrations by living things. And there are no water-saturated magmas at depth to form hydrothermal ore deposits by injecting metal-laden juices into the country rock.

     Still, things are not completely bleak. First of all, that first-order separation from the planetwide differentiation itself has already yielded benefits. In the lunar highlands, or “terrae,” the light-colored, heavily cratered ancient terrane (That’s the spelling used by geologists in the sense of a "general geologic region.") that comprises most of the Moon’s surface, calcium and aluminum have been concentrated into the mineral anorthite, CaAl2Si2O8. Large parts of the highlands are dominantly anorthosite, a rock composed mainly of plagioclase (anorthite is pure calcium plagioclase; “plagioclase,” in case we caught you by surprise, is sodium-calcium feldspar, (Na, Ca)(Si, Al) AlSi2O8. Most lunar plagioclase is nearly pure anorthite). Both Ca and Al are not particularly abundant in asteroidal material—the lunar highlands are a much richer source. And Al in particular is a very useful industrial metal.

     The lunar lowlands, or “maria,” (MAH-ree-uh, not like the name “Maria.” The word is Latin, the plural of mare (MAH-reh), “sea”—from Galileo's belief that the dark, smooth lowland areas were seas.) are also enriched usefully. The maria are plains composed of thick sequences of flows of basalt, a dark lava that is also common on Earth (similar basalts comprise the Hawaiian Islands, the Columbia Plateau in Washington state, the cinder cone Sunset Crater in Arizona, most of the sea floors, and so forth). Many of the mare basalts contain a few percent titanium, a useful metal that isn’t especially abundant otherwise.

     The mare basalts are the result of the Moon’s continuing evolution as a planet after its formation; they are “early secondary differentiates,” magmas formed by the partial melting of rock deep within the Moon’s crust long after the Moon had formed. The mare flows are not spring chickens even by geologic standards; they range in age from about 4 billion years to as young (!) as perhaps 2.5 billion. Still, the Moon formed at about 4.6 billion years ago; 600 million years elapsed before mare basalts began erupting. That's a substantial delay; for comparison, 600 million years ago trilobites had just begun swimming in Earth oceans. (The age dates on the mare basalts are obtained two ways. Some come from determinations, on returned samples from Apollo or Luna spacecraft, of the amount of “daughter” nuclei resulting from the decay of long-lived, naturally occurring radioactive elements. Other age estimates are made from the relative abundances of impact craters on the surfaces of the basalt flows.)

     In passing, I’ll note that the Moon’s surface has yet another advantage for mining: it has been pervasively broken up by eons of meteorite impact. The lunar regolith (not “soil”—all soils are regoliths but not vice versa) that has resulted from this comminution is already halfway to being an industrial feedstock. It still needs sieving for size sorting, but most of the milling has been done. And milling is expensive.

     All right already. The Moon is a good source of aluminum and titanium because it is a differentiated body. The surface rocks have even been broken up, so that they’re easy to push with a ’dozer and scoop onto a conveyor belt. But I’ve reviewed how the Earth is a far better fractionating plant than the Moon; can there really be any ores of rare elements?

     Before speculating on the sorts of ores that may occur on the Moon, let’s review the “wish list” for industry in space. The useful elements that are readily available on the Moon are (first and foremost).oxygen, followed by silicon, and then the structural metals iron, magnesium, aluminum, and titanium. In addition, manganese and chromium can probably be recovered as by-products without too much trouble. But what else do we need? Well, first off, there are the volatiles: water, carbon, and nitrogen for life support; carbon and chlorine for carbochlorination, to smelt silicates into free metal and oxygen; water for industrial processes; sulfur for sulfuric acid. Then there are the other industrial metals, which read like a Who’s Who of the periodic table: Copper. Zinc. Zirconium. Vanadium. Molybdenum (generally affectionately shortened to "moly"). Tungsten. Lead. Beryllium. Chromium. Tin. Niobium (I refuse to say “columbium”!). Even gold and silver. Many of these metals (Cr, Mo, V, Nb) are critical in various steel alloys; some (e.g., Zn) are useful for alloying aluminum; a few are useful in themselves (copper for electrical conductors; tungsten for electrical filaments), and yet others are primarily useful in their compounds (Ag in photography).

     To me, holding this shopping list, it looks as if there are three strategies for approaching the search for lunar ores. First and most straightforwardly, we can simply look for exceptionally concentrated deposits of the common elements—nearly pure anorthite, for example, or concentrations of ilmenite (the iron-titanium oxide that is the ore mineral for titanium). This sort of exploration will ultimately be valuable, but it will not be important early in the lunar exploitation effort. The location of a mass driver for sending material off the Moon is dictated by celestial mechanics; certain locations are favored because they lead to achromatic trajectories, trajectories whose endpoints are not sensitive to small errors in launch directions or velocities. Achromatic trajectories are extremely important to the economics of the lunar mass drivers, because both the mass driver and the mass catcher (in space) can be simpler and therefore cheaper. Thus any lunar ore will have to be sufficiently valuable, because of either concentration or composition, to warrant transporting the ore to the mass driver. Even exceptional concentrations of the common elements won’t qualify at first.

     (Transportation of ore to the mass driver won’t be terribly difficult; small mass drivers, “mass throwers,” will work nicely for tossing the material around on the Moon. You don’t need ore cars, because in an airless environment you can count on ballistic trajectories. However, the additional expense of a separate mining base with a mass thrower must be justified by the value of the material mined.)

     Second, we could look for anomalous concentrations of elements that are rare on the Moon but are not particularly rare cosmically. The volatiles fall in this category. For example, there may be deposits of water ice in permanently shadowed “cold traps” near the lunar poles. (The result of a possible lunar ore-forming process that has no counterpart on Earth! Amazing!) Such deposits can be legitimately considered “ores,” according to the definition I quoted earlier; they may be worth seeking because the Moon is nearby and convenient. It may turn out, however, that the asteroids are just as convenient as a source of volatiles. Perhaps lunar volatiles will be most economical for the lunar settlements.

     Probably the most useful prospecting to carry out on the Moon is to search for industrially important elements that are just rare. In this way we are exploiting the Moon’s great advantage; that it is a planet-sized body that has undergone large-scale chemical differentiation. Concentrated deposits of such elements would be extremely valuable even early in the lunar exploration effort; and in the slightly longer run, by establishing sources of raw materials that are completely independent of the Earth, such deposits may be critical.

     With no water on the Moon, many sorts of sedimentary ore-forming processes are out. As I’ve mentioned, too, hydrothermal processes like Earth’s are hampered or precluded by the dearth of H2O. However, although the Moon is depleted in volatiles, some are still present.

     Sulfur, for example, is depleted but extant, and sulfide minerals are accessories (trace constituents) in many lunar rocks. Sulfur is a relatively “electronegative” element, which means it tends to preferentially combine with metals; thus, some sulfur has remained on the Moon in the form of sulfides. In addition, by happy chance most of our wishlist deficient metals are “chalcophile” (more jargon—"sulfur loving"); that is, given their drufhers they will combine in sulfides rather than silicates. Furthermore, molten sulfide and molten silicate together in a magma separate into “immiscible liquids,” like oil and water, and the droplets of sulfide in the silicate melt scavenge most of the chalcophile elements. A number of important ore deposits on the Earth have been formed in this way.

     Chlorine is another important element that, although relatively volatile, is electronegative and should have been retained to some degree on the Moon in metallic salts. Indeed, chlorine may become concentrated with sulfur in a late fluid phase in a cooling magma. Such a late vapor phase, the “juices” exuded by a cooling magma, would be analogous in both geochemical and economic significance to Earth’s hydrothermal fluids; although “hydro”-thermal, in this case, is something of a misnomer. Chlorine should also form water-soluble salts—this should make leaching the ore a simple procedure!

     Sulfide or chloro-sulfide enrichment is not the only possible lunar ore-forming process I can envision, however. Some important incompatible elements are “lithophile” (“rock-loving,” this time—they like silicates best). One such metal is beryllium. It is extremely refractory, so it should not be particularly depleted on the Moon; however, beryllium is also an extremely rare element cosmically, because its nucleus is destroyed easily in stellar nuclear reactions. Zirconium is another incompatible, refractory, lithophile element which is relatively rare, and which makes dandy alloys. Beryllium tends to occur mainly in the silicate mineral beryl (whose gem forms are emerald and aquamarine), whereas zirconium mostly occurs in zircon, another silicate. A highly differentiated silicate rock—a granite, say —that contained a few percent of beryl and/or zircon would be a nice ore. Yet another possible lunar ore-forming process is the formation of “cumulate” deposits, an igneous process that doesn’t depend on a late fluid phase separating from the cooling magma. Cumulates are formed in a large body of cooling magma; as the magma cools and crystallizes, heavy minerals can crystallize out and then sink through the melt to rest on the floor of the magma chamber. In some cases, a single mineral will become stable all at once in the cooling magma, forming a distinct “sedimentary" layer when it settles out. Most of the Earth’s chromium deposits are cumulates; perhaps similar deposits occur on the Moon.

     Well, by just “waving my arms,” using elementary geochemistry and our limited information on the Moon, I can hypothesize some reasonable lunar ore-forming mechanisms. Some of the processes may not work out, for one reason or another; but there are probably some processes I haven’t thought of that do.

     How do we go about prospecting for ores? Another advantage of the Earth’s active tectonics is that ores formed by processes occurring deep in the crust have a reasonable chance of being made accessible by later uplift and erosion. Although such uplift does not occur on the Moon (at least in the last four billion years or so, but we may have a'pleasant surprise when we investigate the ancient highlands in detail), excavation by impacts—especially very large impacts —furnishes a fair substitute. Craters truncate and expose geologic features, and the impact lofts out material from deep in the crust.

     In fact, the excavation by impact provides a means for prospecting. When a meteoroid strikes at speeds of tens of kilometers per second, a small fraction of the material splashed out—the ejecta—is thrown for tens, hundreds, or thousands of kilometers, or even reaches escape velocity and leaves the Moon completely. That small, very high velocity fraction from any cratering event lends every lunar regolith an “exotic” component: a few percent of the dirt comes from over a hundred kilometers away; a tiny proportion comes from halfway around the Moon. Analysis of these exotic components yields information on the composition of distant parts of the Moon; Nature has provided us with a remote sampling mechanism.

     Such analysis has already provided information on unsampled areas of the Moon. It was surmised very early in the Apollo program, for example, that the lunar highlands are much richer in plagioclase than the maria; this was subsequently confirmed by the Apollo landings at highland sites. A rock type nicknamed KREEP also was inferred from the exotic components in the regolith, and also has subsequently been found. (That’s an amazing acronym, by the way, possible only in a linguistic hodgepodge like English; it stands for potassium (whose chemical symbol is K, from kalium), Rare Earth Elements, and Phosphorus. KREEP material is somewhat enriched in those elements.) Finally, just recently a fragment of granite has been found in one of the breccias (rocks comprised of broken bits of other rock) returned by the Apollo missions. Somewhere, thar’s granite on the Moon. And granite is a lithophile rock that results from extreme chemical differentiation. On the Earth granites are fairly commonly associated with ores (remember beryllium and zirconium?).

     Not only can we determine what other rocks exist on the Moon from analysis of the exotic component in lunar regolith, we can even locate the general area where the rocks occur. Sampling the regolith at a number of different sites will allow us to triangulate back to the source of the exotic component (this will be easier when we have the maps I describe below, which will be made by remote sensing from low orbit). This “backtracking” is no different from what terrestrial prospectors and field geologists do already. When beginning field work, you always inspect the “float,” the broken rock that has been brought downslope and downstream by erosion, to determine the rock types that occur upstream. Saves a lot of walking! And a prospector, when he finds “color" in a stream, will continue panning upstream until the color vanishes. He has then located where the gold entered the stream, and he now starts exploring the slopes on either side for the source.

     Probably, ore deposits such as I describe in this article will generally be too small to be detected directly by remote sensing. You’ve simply got to get on the surface and take samples. However, detailed mapping by remote sensing will give us a much better understanding of the Moon’s geology* *Not “selenology.” “Geology” (also “geophysics,” “geochemistry,” etc., have, quite sensibly, been generalized to all planets, not just the Earth.) than we have now, and will allow us to locate geologic provinces where ore deposits might be favored. Mineral exploration is also done this way on the Earth; you define a favorable area (according to some geologic model—and different areas can become favorable as different models come into vogue!) and then start looking.

     After my spiel several paragraphs ago on the value of the “exotic component" in the regolith, you may wonder how remote sensing could be of any use on the Moon. Hasn’t the regolith been hopelessly homogenized by meteorite impact? Not quite; the bulk of the ejecta from an impact doesn’t move very far at all. Over 90% of the dirt sitting on top the lunar surface is the broken-up, pulverized, and agglutinated equivalent of the bedrock underneath. This fact makes remote sensing of the lunar surface feasible.

     In fact, orbital remote sensing of the Moon will be easier than the Earth in at least one respect: the absence of an atmosphere allows you to get much closer to the surface. For example, “potential fields” techniques are commonly used in geophysical exploration on Earth. In these techniques, you detect minute variations in the Earth’s gravitational or magnetic field and use these variations to infer geologic structure. Different rock types cause such variations by their differences in density or magnetic properties. Because of the high resolution required, potential-field surveys on Earth must be airborne or ground-based, and are therefore expensive. On the Moon we can sense potential fields directly from orbit.

     Lacking this more detailed geologic mapping, and the more detailed understanding that will come with it, what areas merit prospecting at this point? Several come to my mind. First, a number of features on the Moon have been interpreted as volcanoes. This interpretation is based solely on their detailed morphology, not on sampling; if the interpretation is correct, they represent a different style of volcanism than the mare basalts. Therefore the lavas making up the volcanoes probably differ in composition from mare basalt, and they may be more differentiated. At least they’ll be differently differentiated. Such a volcano laid open by a large impact would be a very interesting place to look for veins of minerals.

     In a somewhat similar vein (!), “lunar transient events,” possibly due to volcanism, have been reported from time to time, and they are still unexplained. The most notorious events have been associated with the central peak in the crater Alphonsus, where spectrograms taken in the ’50s suggested gaseous emissions. Perhaps the Moon’s volcanism is not quite dead even now. Perhaps, even, volatile emissions accompany this volcanism. For economic as well as scientific interest, Alphonsus should be investigated as soon as we return to the Moon.

     Finally, the lunar highlands are an ancient (>four billion years), heavily cratered terrane that is certainly far more complex in detail than we currently understand. Sure, by and large the highlands rocks are anorthosite (or norite, or troctolite—two other plagioclase-rich rock types), but there’s at least some granite out there, and there might also be large igneous bodies with compositions that lead to cumulate deposits. Additionally, the highlands have been thoroughly shattered by major impacts (and I mean major—craters hundreds of kilometers across), and these rocks were emplaced when the Moon was still highly active volcanically. Many mineralized districts on the Earth contain thoroughly shattered rock (shattered by faulting, in the terrestrial case) which has hosted mineralization because it is riddled with conduits for ore-forming solutions intruded later. What sorts of rare rock types have been emplaced here and there in the highlands? What veins of ore may seam the bedrock?

     We really ought to go and see.


     Beatty, J. Kelly, Brian O’Leary, and Andrew Chaikin, eds., The New Solar System, Cambridge University Press and Sky Publishing Corp., 1981.

     Greeley, Ronald, and Peter Schultz, eds.,A Primer in Lunar Geology, Ames Research Center, NASA, 1974.

     Murray, Bruce, Michael C. Malin, and Ronald Greeley, Earthlike Planets, W. H. Freeman and C0., San Francisco, 1981.

     Papike, J .J ., S.B_ Simon, and J .C. Laul, The lunar regolith: Chemistry, mineralogy, and petrology, Reviews of Geophysics and Space Physics, 20, 761-826, 1982.

From MINING THE MOON, ANALOG Magazine November 1983 by Stephen L. Gillett, Ph.D.

     Returning to the theme of bootstrapping for a bit, let's examine what kind of material processing could be done with a modest payload. I'll cover two scenarios, lunar surface and captured asteroid; the first post will discuss the moon.

     As with all unproven technology, mass estimates for mining equipment are wild guesses. I'll be using the wild guesses of people smarter and/or better informed than myself. Most of the concepts presented are well-known; I've simply combined them a different way and extrapolated the results.

     For those not interested in reading the wall of text to follow, here are my results:

3x haulers based on NASA chariot / lunar electric rover (1.2 ton each)
3x prospecting package: gamma spectrometer, neutron spectrometer, UV/VIS/IR spectrometer, magnetometer, robotic scoop (included in hauler mass)
2x excavator equipment package: bucket and cable rig, sized to fit hauler chassis (up to 3 tons each)
60kW power center (1 ton)
6x 90m² solar reflecting ovens with electrodes (0.5 tons each)
ore separation / benefication (0.5t)
cryogenic oxygen plant (4t)
tank press (0.5t)
radiators (2t)
electrical cables, 6ga/10.5mm, 4-conductor, 108v 3phase, 6kW, 8km (4t)
4000x cryogenic tank valves (0.2kg each)

total: 25.9t
(1 SLS or 2-3 Falcon heavy)

     - 2,400 tons of material processed per year, 10 tons per lit day
     - 840 1m³ filled oxygen tanks per year (958t LOX + 95.8t aluminum)
     - 128 1m³ filled water-ice tanks per year (120t H2O + 1.2t aluminum)
     - 527t metals (iron, additional aluminum, titanium, calcium) per year
     - 480t silicon
     - Unknown quantities N2, trace metals, other volatiles
     - ~217t refractory slag (radiation shielding); can be pressed, sintered and metal-wrapped

     The supply of valves is enough for four years; they are brought along because they are too complex and risky to assemble in place. A pressed and sintered (or SLS + heat treated) pressure vessel is simple enough to be produced on-site even if welding is required. Sufficient oxygen will be available for burst testing the results before use.
     If significant amounts of nitrogen are found, that would also be liquefied and tanked. Hydrogen would be reacted with oxygen and stored as water.
     Cables can be eliminated at the cost of more batteries and shorter range.
     Minimal additional equipment (1-2t) can enable production of thin-film solar panels with quarts front-glass and aluminum, titanium or iron backplates.

     Back to the long form...

     A moon expedition would produce huge amounts of oxygen. The main use for this would be to transport it to low-Earth orbit and pair it with hydrogen launched from Earth (or collected elsewhere) for fuel or for water. 1 ton of water contains 888.9kg oxygen and 111.1kg hydrogen; 1t of hydrogen from earth could be paired with 9t of oxygen from the Moon to yield 10 tons of fuel or water; this 10:1 ratio provides significant savings. For manned exploration of the moon, having oxygen available at each step of the trip saves much more than 9:1 since it does not have to be lifted from Earth and then sent to the Moon. For a cargo trip to Mars, the Earth departure stage calls for anywhere from 90 to 115 tons of fuel; using Lunar oxygen frees up 81-103 tons of payload to LEO or eliminates an entire SLS launch of fuel. A Mars campaign that requires four cargo trips and two manned trips could save six fuel launches or about $4.5 billion over six years. A single SLS launch could deliver a payload to the Moon capable of producing the ~600 tons of oxygen in one year as well as the vehicles necessary to deliver it to LEO; even if that mission costs $750 million for the rocket and another $1 billion for the payload it would save $2.75 billion while validating ISRU technology prior to its use on Mars.

     For a variety of reasons, the most useful place for a single mining operation on the moon is at either pole.

     Problem: The moon rotates at the same speed that it orbits Earth (it is tide-locked; the same face of the moon always faces Earth). Since the moon's orbit is about a month long, each day has two weeks of daylight and two weeks of night at the equator. That means enough power to run for two weeks of darkness has to be stored during the lit hours; most industrial processes would have to be halted.

     Solution: High peaks or crater rims near the poles can be sunlit for 80% of the time or more. (due to the axial tilt and geography there are no permanently-lit areas at ground level.)      A base at one of these locations could operate at full power for around 22 out of every 27 days.

     Problem: The moon's soil or regolith is bone dry to at least 30cm deep, and it seems unlikely that there is any bulk ice under most of the surface. Metals (titanium, aluminum, calcium, iron, magnesium), silicon and oxygen are abundant but hydrogen, carbon and nitrogen are exceedingly rare.

     Solution: There are craters whose bottoms are never lit by the sun, conveniently located next to the high-sunlight peaks. These areas get so cold that they can freeze water and volatile gases (including nitrogen); this is why they are called cold traps. There is strong evidence of water ice, hundreds of millions of tons of it, at the north polar craters and no reason to suspect it is not also abundant at the south polar craters (Shackleton crater).

The mission should target either the Shackleton crater rim near the south pole or the rim of Peary crater near the north pole.

     Remaining problems: many.

     Rich sites to be mined need to be identified with some kind of sensing instrument (or more likely a set of 2-3). Nearly all of the major minerals on the moon can be processed for oxygen, but some of their metals are more useful than others.
     Estimates for volatile concentrations are as high as 5% for the target areas. Let's assume the bulk excavation of material yields 1% volatiles and further assume that it is nearly all water (either free as ice or bound as hydrates). There is some free hydrogen from the solar wind and potentially traces of hydrocarbons and nitrogen-bearing organics, but without enough data to even guess at a concentration. It is possible that there is bulk water ice available; if so, it can simply be melted, filtered and frozen again in tanks with minimal energy requirements.
     Just like on Earth, craters on the Moon were caused by asteroid or comet impacts. Many of these impactors are rich in metals (iron-nickel-cobalt and platinum group metals), while others are rich in carbon. It is possible that these sites will serve as rich orebodies for these resources. There are also a few areas where mantle material is exposed; this boundary layer is rich in incompatible elements like rare earths.

     Products of this early mission would be water, hydrogen, oxygen, base metals, possibly ceramics and possibly semiconductors. Later work would advance to construction of integrated circuits, LEDs and multijunction solar cells in addition to worked metal (bar, sheet, tube stock).

     A mobile excavator would be required, probably a simple dragline. I've seen proposals that assumed the regolith would be powdery and easy to scrape up, but the Apollo reports indicate that under a surface dust layer the soil was surprisingly tough. Some think that the grains have settled due to vibration from impacts over the past few billion years. Regardless, the tough soil and the possibility of crystalline ice means the excavator needs to be able to break up soils. In the low gravity of the moon, this requires either a very large amount of mass to produce the necessary force or a novel solution of some kind; either way will require a lot of power. I'm fond of the idea of a rotary flail since the impact force can be closely controlled, but that introduces a mechanical part that will wear over time. I am also fond of the idea of using a sheet or bag to cover the active area, something to capture flying dust and debris to avoid messing with the atmosphere and surrounding areas. Presumably this would use electrostatics to capture dust.      Due to the high power requirements I assume this excavator will be connected to the power center with a cable up to a few km long; this is one of the heaviest single items on the list but it is less risky than batteries or beamed power.

     See NASA DRM5 numbers; they propose an excavator system that is under 1t all-inclusive and redundant, including onboard power via electrolysis.

     Once the raw material is excavated it has to be processed. Options include baking out the water at the excavator or hauling it back to a refinery. I prefer hauling it back to reduce thermal pollution (that is, to avoid cooking off the useful volatiles in the mining area). So, this introduces the need for a hauling rover of some kind. The output of the excavator will drop directly into the bed of the hauler, with an electrostatic dust sheet over the top.

     The hauler will deliver regolith to the processing center. Samples will be analyzed for content in order to determine the most efficient processing plan. Volatiles like water will be baked out using solar concentrators at 600-1000 °C and then cryogenically separated. The remaining ore is now stable and can be stockpiled for later processing if needed. Iron-rich nodules and fragments will be removed with a magnetic rake. The remaining grains can be sorted with a rotary device into bins based on grain strength (aluminum-rich, titanium-rich, glasses) anywhere from 50% to 90% enriched.

     Many proposals assume the use of a reactant gas (usually hydrogen) which will be recycled; this gas is used to extract oxygen at lower temperatures than would be required otherwise. This seems unreasonably optimistic; hydrogen gas is difficult to contain on Earth, but we're talking about a hard vacuum environment with the most hostile abrasives we've ever encountered in the natural world. It will have to handle hundreds to thousands of open/close cycles with a perfect seal in the face of 1500+ °C temperature swings. Add the lack of maintenance or human operators for adjustments plus the need for vacuum pumps with both high volume and very low pressure and that all adds up to heavy, complex and unreliable.
     I choose to assume a brute force method of direct molten electrolysis. Instead of using hydrogen and reducing iron oxides at 1600 °C, the processor will melt the ore grains at 2200-2500 ­°C and electrolyze the melt with tungsten electrodes. This will produce oxygen gas at one end of the cell and reduced metal at the other end. For the lighter metals (aluminum, calcium, sodium) the cell temperature is high enough to vaporize them; the metal vapor can be collected on cold plates and scraped off as fine grains or it can be used directly for vapor deposition. Heavier metals (iron, titanium) will accumulate as melt and can be tapped and formed into bars. High-temp refractory ceramics like magnesia are out of reach of this method but might be available to a solid-phase electrolysis process. The oxygen is passed back through the incoming ore stream for heat exchange; any unreacted contaminants will definitely be oxidized in the process.
     Concentrated ores can be heat-treated further as a form of distillation to remove materials in order of their melting points; a carefully-designed feed mechanism can pass the ore through one oven, allow the lower-temp material to melt, then deliver the higher-temp material to another oven. The temperature of the refining furnace can also be adjusted to evaporate out metals in sequence with reasonably high purity. One additional control is the voltage of the electrolysis cell; if necessary the oven can be operated as a batch process using appropriate voltages to reduce each metal in sequence.
     The processor requires a very high temperature furnace. This will be made of magnesia (magnesium oxide, melting point 2852°C) and heated with a mix of joule heating and concentrated sunlight, which will require a large reflecting area of aluminized mylar. The magnesia is very heavy; it may be possible to construct a suitable trough on-site from regolith baked, pressed and sintered into a useful form. At this stage in the process the ore grains have been heated to recover most of the volatile content; the melt can be performed in open vacuum for direct solar heating with only the electrode sections enclosed to capture products. This avoids the need for an absurdly high-temperature transparent material. The furnace will be continuous process; accumulated solids are scooped out and dumped (and possibly used as a heat source for the first baking step). These can be compressed in the tank press to form radiation shielding blocks if desired. Oxygen is continuously produced and passed back up the ore stream, then cooled and passed to the cryogenic plant. Reduced metal either vaporizes and is condensed on a cold plate or deposition target or is drawn off as a liquid from the bottom of the melt and cast into the desired form.

     As a specific example: aluminum-rich grains will be melted (2072°C) in a magnesia crucible by concentrated sunlight and then electrolyzed (with tungsten, tungsten carbide or molybdenum electrodes) into oxygen and aluminum metal. The temperature can be further increased to 2470°C to produce aluminum vapor; thin-film conductive/reflective coatings or vapor deposition can be performed directly in the furnace. Aluminum metal parts can be controllably oxidized using the hot oxygen stream to form alumina surface coatings for abrasion resistance. This requires about 3.2MJ/kg from 0°C to 2100°C; 80-90% of this can be from sunlight, about 40m² of reflectors and 6kW for 1 kg per minute capacity. 52.9% of the yield is aluminum and 47.1% is oxygen by mass, barring any other metal oxides in the melt.

     As it turns out, tungsten is not suitable for this process over the long term because it is oxidized. An inert surface layer of iridium is required on the anode (oxygen-generating), while molybdenum is sufficient for the cathode (metal-generating). The anode layer needs to be thick enough to resist abrasion from any unmelted grains. A cylinder furnace of magnesia with molybdenum cathode strips along the bottom and an iridium-coated tungsten anode bar along the long axis will be used; the entire furnace is sealed and heated by concentrated sunlight from the outside. Preheated ore grains are loaded at the top of the 'near' end with an augur. A baffle keeps gases contained but the melt's surface is exposed to vacuum at this end; if this volume is enclosed then a cold plate could capture volatiles that were missed by other process steps. Oxygen is tapped at the top of the far end, while molten metal is tapped near the bottom of the far end. The endcaps of the furnace can be removed so any accumulated slag or debris can be removed and electrodes can be replaced.
     In order to boil the aluminum metal, the entire furnace's operating temperature is driven higher. Care must be taken to keep the oxygen gas and aluminum gas separate; if this mode of operation is desired then the internal structure should be shaped like a U, with cathode and anode in separate arms.
     There are ongoing efforts within NASA and within the steel industry for developing robust molten oxide electrolysis cells; a prototype molten regolith cell might contain 0.02m³ of volume and consume 3-5 kW of electricity as a 100% joule-heated furnace (with no mention of cycle time). My proposal needs to process 10m³ per day but can obtain very large amounts of heat externally; as a result my design can place the electrodes closer together, reducing the resistance of the melt and thus the electrical losses to heat.

     This method can be used for extracting iron, calcium, sodium and titanium from their oxides as well. While useless on earth, pure calcium is an excellent conductor in dry, oxygen-free environments and could substitute for aluminum in PV conductor lines. Sodium and calcium are potential scavengers for corrosive volatiles like chlorine and fluorine, but their vigorous reaction with water calls for careful process management.

     Silica grains can be used to make clear glass. Thin quartz glass sheets are a starting point for making PV cells (the surface protective layer); conductive lines of aluminum are vapor-deposited onto the glass, then doped silicon, then a thicker layer of aluminum. These are not the most efficient devices (~9%), but they are very simple and straightforward to manufacture. The silicon can be extracted from silica just like the aluminum is refined, but at a lower temperature (1713°C).

     With a goal of 1 ton of 1% icy regolith processed per day we should be producing 10kg water, 400kg oxygen, 200kg silicon, 120kg iron, 60kg aluminum and about 260kg of other metals and unprocessable byproducts. Specific ratios of silicon, iron, aluminum and titanium depend on what minerals are present at the excavation site, but it is very difficult to predict in advance what the ratios will be at a specific site. This processing will require roughly 30m² of solar reflector area and 4.5kW of electrical power. If we assume the initial power system alpha is 200 watts per kg (since it needs to withstand lunar gravity), that's only 22.5kg of solar panels.
     Pushing things a bit farther, 10 tons of ore per day would require 45kW of power (225kg) and 400m² of reflector area (about 8kg plus supports). A minimum work cycle of 20 days per sol means about 2 tons of water, 80 tons of oxygen and 52 tons of metals per sol (27 days). If the excavator manages to produce ore with 5% ice then the yield is 10 tons of water per sol; if bulk ice is discovered then a different process will be needed. It would be possible to process larger quantities of ore for volatiles and only process a portion of the desired metals; extracting water takes a tiny fraction of the energy needed to melt and electrolyze metal oxides.

     See the NASA DRM5 numbers for ISRU equipment; to produce 56kg H2O per day from 3% water-content soil required 413kg of equipment and 2.02 kW of power. That's roughly 1.8 tons ore per day; multiply by six to hit the 10-ton target and that's 2.5t of equipment and 12kW of power for the entire process end to end. Most of the power is used for process heat, so substantial savings can still be obtained with solar reflectors. This would produce a supply of dry granular material for later processing or for direct use as bulk shielding.

     The excavator needs to remove a bit under 7kg per minute. Bulk density is around 2g/cc (2ton/m³). A 100-liter bucket would have to be filled about every 28 minutes. If the hauler holds 1 ton (cube 80cm per side) then a full round trip (load, deliver, unload, return) must take 2 hours and 24 minutes or less. Assuming load and unload take 12 minutes that leaves 1 hour for the drive one-way; better yet, let's assign 1.5 hours for the loaded trip and 30 minutes for the empty trip. At 5 m/s maximum empty speed (1.67m/s loaded speed) that gives a range of 9km between refinery and excavator.
     If the hauler holds three tons (100x100x150cm) then a full trip is at most 7 hours 12 minutes. Using the same 12 minutes to load or unload and 3/4 of the trip time loaded, that's 5 hours 6 minutes for the loaded trip and 1 hour 42 minutes for the return trip. Using the same speeds (5m/s empty, 1.67m/s full) that gives a range of 30.6km.
     An alternative is to use both haulers in rotation; one is stationed at the excavator getting filled while the other travels to the refinery and back. There would be enough time for prospecting during the return trip.

     NASA already has an electric rover design in this size range; 1 ton of vehicle mass for 3 tons of payload. That design's maximum speed is quoted several different ways, but at least one reference uses 15mph (6.7m/s) as high-gear speed, presumably for just the chassis, and several others use 10km/h (2.78m/s) as the top speed while loaded with a mobile habitat module. I would add prospecting sensors, a small scoop and a blade and auger.

     For reasons of efficiency, the excavator should use a hauler chassis with an excavation package mounted on top. A spare chassis can be shipped in case either the hauler or the excavator fails. Resupply missions can carry modular parts. Two excavation packages will be shipped with the initial mission, both using a drag line arrangement that minimizes repositioning time. (A set of two pylons with pulleys, so the bucket can be moved anywhere within a triangle defined by the two pylons and the hauler base. A 50m triangle with 450m of cable can cover 1082m² of territory; for excavation to 2m that's 2164m³ or about 4300 tons, more than a year of production.) All three haulers will be equipped with a blade and augur. In fact, the initial phase would involve all three vehicles using just their blades to clear a landing site for cargo spacecraft, followed by a short roving mission to identify high-ice sites and then leveling a basic road to the best site. This will provide some ground truth on solar wind ions and other volatiles in the upper regolith plus validate several approaches to lunar base site clearing for manned missions.

     Harvested metal (primarily aluminum) is pressed into cryogenic tanks using multipurpose valves brought from Earth (solenoid with integrated pressure relief). These tanks are pressure-tested and then filled with liquefied oxygen. Filled tanks are stored in a permanently-shadowed crater for zero boiloff. Tanks are shipped to L1 for about 2.5km/s dV in a dedicated lander, then to LEO for a further 0.8km/s in an orbital tug with heat shield or 3.8km/s propulsive-only. Ideally a launch sling would be used to deliver the tanks to L1/L2 and avoid the need to burn propellant.

     Once this architecture is validated it could be reapplied at other sites and for other purposes. The haulers could be shipped to a future human lunar base to clear landing sites, roads and construction sites, plus accumulate material for radiation shielding and later bury the habitats. The processing equipment could manufacture solar panels, heat radiators, oxygen, structural materials, etc. in advance of crew arrival so the mass to be shipped from Earth can be minimized.
     Similar equipment could be shipped to Mars for the same purpose; the initial cargo mission could deliver equipment for site preparation and atmosphere processing. Mars has a much more complete chemical environment, so a much more useful selection of products can be produced.

     Again, NASA DRM5 has useful numbers for PV power systems. A single PV/RFC (regenerative fuel cell) module was 4.5 tons and provided 5kW of fuel cell power and 290m² of collector area at 29% efficiency. Under lunar conditions (no atmosphere, 1366W/m², ground return ignored) that array produces 396 kW gross, roughly 336kW of conditioned power. The whole system could be reduced to one fifth, massing 0.9t, providing 1kW of fuel cell power and 67.2kW of PV power. This would be abundant power for daytime operations but probably insufficient night-time power. However, the fuel cell's peak output would be more than sufficient, so extending operation to several days would require only larger tanks for water, O2 and H2. This is reasonably in line with my original estimate of 1t for 60kW.

     Further, the DRM5 offers a nuclear alternative. A 30kWe nuclear reactor masses 7.8t and would enable continuous operation. I think this would be an enabling technology that would completely change the architecture of a lunar mining operation. Night on Luna is the enemy for solar-powered architectures, leading to deep thermal cycling and heavy battery or fuel cell requirements. It also greatly expands the potential locations for a base. There would still be a need for rover excavators; nuclear power means a lot of radiated heat that we want to keep away from the cold-trap volatiles we are most interested in harvesting. One benefit is that the reactor's waste heat can be used as a first stage heat source for ore processing. Using JIMO (project Promethius) data, the proposed brayton cycle reactor has an end to end efficiency of 18.35% from thermal to conditioned electrical power at the PMAD output. The Mars design has slightly improved efficiencies, but JIMO performance would be sufficient. Let's assume the difference means a 30kWe reactor would mass 8t even and spec 163.5kWt. This reactor's coolant is 920-950K at the recuperator, a very convenient source of process heat at 650-670 °C and around 133kWt available.
     Lunar soil's specific heat is 0.88 kJ/kg*K at 350K; data is sparse for higher temperatures but can be expected to increase somewhat up to 950K; let's call it double or about 1.7kJ/kg*K. That would mean the available heat could cook soil from 90K to 950K at a rate of 5.46kg per minute. 10 tons processed per day would be 6.94kg per minute, so we are in the right ballpark. A counterflow heat exchanger running between the incoming ore and outgoing ore would only need to recover about 22% of the heat to close the thermal requirements.
     If relatively pure water ice is available, it can be taken from 90K to 275K (2 °C) for ~334kJ/kg + 334kJ/kg to melt it. The reactor could process 23.9kg of water ice per minute; this application would use heat at the radiator return (~390K) rather than the recuperator for more efficient operation. This approach could handle up to 34.4 tons of water ice a day.
     Both of these modes of operation would leave the entire 30kW of electrical power available for other purposes
From EARLY LUNAR MINING by Chris Wolfe (1933)
Lunar Materials Production
Additional Processes
(cumulative with "builds upon")
Additional Materials Produced
(cumulative with "builds upon")
1N/ASieve and/or grind regolithRegolith
21Molten Regolith Electrolysis“Mongrel Alloy”
31,2Vacuum Distillation or equivalentElemental Aluminum, Iron, Magnesium, Calcium, Silicon, Titanium.
(Also, if regolith obtained from KREEP terrane, then Potassium, Rare Earth Elements, and Phosphorus)
41-3Metals RefineryGood alloys
5N/AIce Mining & DistillationH2O, CO, CO2, NH3, many compounds and trace metals
65Fischer Tropsch processCH4, plastics, rubbers
71-6Metals Refinery including carbon from 5 & 6Steel
81-3Slaking and cement productionLime and cement
91-8Advanced processesAnything you want

Based on an earlier proposal, the method is a three-drum slusher, also known as a cable-operated drag scraper (Ingersoll-Rand Company 1939, Church 1981). Its terrestrial application is quite limited, as it is relatively inefficient and inflexible.

The method usually finds use in underwater mining from the shore and in moving small amounts of ore underground. It uses the same material-moving principles as more efficient, high-volume draglines.

The slusher is proposed here because the LOX-to-LEO project is a very small operation by terrestrial standards and requires a method that minimizes risk. The three- drum slusher has already proven itself in this context. It has the advantages of simplicity, ruggedness, and a very low mass to be delivered to the Moon. When lunar mining scales up, the lunarized slusher will be replaced by more efficient, high-volume methods, as has already happened here on Earth.

The Machine and Duty Cycle

Before discussing the advantages of the machine in a small-scale startup lunar mining scenario, I will describe the slusher and its duty cycle. It consists of the following modules (see figs. 18 and 19):

  1. A mobile power unit and loading station—including three drums around which the cables are wound, a mechanism to place anchors, a mechanism to change tools, an optional operator cab, a dozer blade, and a conveyor to load material into the electrostatic separator
  2. Three lengths of cable to operate the scraper or other mining tools
  3. Two anchored pulleys
  4. Interchangeable working tools, including scrapers, rakes, plows, and rippers

The duty cycle starts with machine setup. The mobile power/loader unit places two pulleys at appropriate locations at the mine site. They could be anchored by large augers in the firm regolith below the loose soil or by other methods. The preferred anchoring method depends on specific site characteristics. After the pulleys are anchored, the power unit similarly anchors itself. The two pulleys and the power unit form a V-shaped mining area. Because machine setup is done only infrequently, is a complex job, and requires firm anchoring, it could be left as a manual operation. For one reason, the anchoring augers might hit buried rocks before they are successfully emplaced. Further study may show that automated or teleoperated setup is also feasible and more desirable.

However, I will mention one major alternative—a stationary power/loader unit (fig. 20), which is the terrestrial configuration. In this case, the slusher itself would be far simpler, but such a system would require an auxiliary vehicle to transport the slusher from site to site and set it up. A stationary slusher would be less able to remove unexpected obstacles from the pit, as I will discuss. Either way, the excavation duty cycle is basically the same.

After setup, the excavation duty cycle begins with the scraper (or other tool) at the loading station. The scraper can be moved to any point within the V by a combination of tensions on the two outhaul cables. After reaching the desired position, usually as far into the pit as possible, the scraper is pulled back to the power/loader unit by the inhaul cable. During inhaul, a combination of inhaul force and scraper weight causes the scraper to fill with loose regolith and carry it back to the power/loader unit. Here the material is pulled up the ramp, discharged from the scraper onto the conveyor, and loaded directly into the mill module.

The mill is the electrostatic separator described by Agosto in the section on beneficiation. The separator should be in direct contact with the slusher. This eliminates rehandling of the mined material, resulting in a significant energy saving, since 90 percent of the mined material will be rejected by the separator. The waste from the separator is dumped away from the production area by ballistic transport or another method. Waste transport need only be far enough to keep the separator and slusher from being buried in their own waste.

The box-like scraper will have closed sides to keep the very fine regolith from spilling out, as has been the terrestrial experience.

Because the machine defines its own mining area and machine motions are repetitive, the scraping operation is a reasonable candidate for automation. Feedback control for automatic loading of the scraper will be supplied through sensing the inhaul cable tension. Loading always requires complex motion control, but the problem is more easily resolved with a limited-motion machine such as the slusher than with fully mobile equipment, such as front-end loaders, which have unlimited freedom of motion.

After mining starts, the mobile power unit generally does not move. If an obstacle is uncovered in the pit, the mobile version of the power/loader unit can detach from its anchor and move into the pit. (The anchor is not removed from the soil unless the machine is moving to another site.) To facilitate pit work, the loading ramp is tilted up and a dozer blade extends to its working position. The blade can push boulders out of the pit or mine a small selected area. Because the power/loader unit is lightweight and consequently has poor traction characteristics, it must pull against the outhaul cables when it works a load in the pit. The complexity and uniqueness of this job argue against automating it, but automation is not impossible and teleoperation is a possibility. Both setup and power unit pit work can be done by teleoperation, except for handling severe unforeseen problems that require human intervention.

During normal operation, electric power is supplied to the power/loader unit by a stationary cable. When the power/loader unit works the pit, it gets its power through a cable reel located at the anchor. One advantage of stationary mining equipment such as the slusher (even the mobile version moves very little during excavation) is simplicity of power supply. Most mobile terrestrial equipment has diesel power, which is rugged, capable, efficient, and, most importantly, onboard. These loaders are very flexible and rugged earth-movers. The lunar alternatives are less satisfactory. Lunar loaders with onboard power would probably use electric motors driven by fuel cell or battery technology. Both are expensive options. Versions with external power must be fed electricity through a trailing cable. Terrestrial experience has shown that trailing cables are high maintenance items, but adaptation to the Moon is possible. Another possibility is a new-technology internal combustion engine, but developing the engine and finding lunar fuel sources are difficult problems.

The Lunar Environment and Machine Design Principles

The major reason for proposing the three-drum slusher is to illustrate problems to be expected in a lunar mining project.

Simplicity in Design and Operation

Compared to other mining machinery, the three-drum slusher is quite simple in design and operation. This simplicity yields several interrelated advantages.

  1. Fewer moving parts, resulting in fewer failures per operating hour
  2. Simpler repair, reducing downtime after a failure
  3. Smaller inventory of repair parts, hence less weight to transport to the Moon
  4. Simpler parts, with faster adaptability to lunar manufacture
  5. Less redesign for lunar conditions, with consequently lower R&D costs
  6. Fewer degrees of freedom than mobile equipment, and therefore relative ease of automation
  7. Fewer project startup problems

Traction Independence

Mobile mining equipment depends on traction to generate sufficient loading forces on the blade or scraper. Most terrestrial mobile equipment loads near its traction limit. On the Moon, reduced gravity creates a less favorable inertia:traction ratio. Increases in traction are achieved by increases in mass, but increases in mass add inertia, which decreases control of a moving machine. To achieve the same traction as on the Earth, a mobile machine on the Moon would have to have six times as much mass. This greater mass would cause correspondingly higher inertial resistance to turning and slowing.

Slusher loading forces are supplied through the cable, thus almost eliminating traction problems. The scraper bucket will have to be more massive than on Earth, simply to cause the bucket to fill. To lower launch weight, the extra mass needed by the scraper bucket can be supplied by lunar rocks.

Since the slusher is a relatively low-production method, upscale lunar mining projects will eventually use mobile mining methods. It is necessary to address inertia- traction problems as early as possible. Further study may find that long-term considerations argue for using mobile equipment from the very beginning. As with the scraper bucket, the extra traction mass can be supplied by lunar materials. Perhaps traction could be improved by new tread or track designs.

Mining Flexibility and Selectivity

The lunar slusher differs from the terrestrial slusher by one major design addition: the power unit is mobile rather than stationary. This allows the machine to set itself up and eliminates the need for an auxiliary vehicle. Most important, by adding a dozer blade, the machine can doze undesirable rocks from the pit. Such large rocks would impede mining operations if the power unit were stationary.

The mobile power unit makes the machine more selective. By allowing the power/loader unit to reposition, the slusher has some ability to separate different soils during the mining process or to go into the pit and mine a small area of interest.

Mining Tools for Selecting Particle Size and Breaking Regolith

The ability to change from a scraper to a rake allows the machine to select different size fractions. For example, if fines are required, the area can be raked on the outhaul, so that oversized rocks are moved to the far side of the pit. Then the rake can be exchanged for a scraper to mine the remaining fines. If larger sizes are desired, they can be raked in on the inhaul.

Other tools, such as rippers or plows, are used to break difficult ground. Lower levels of lunar regolith appear to have a high degree of compaction (Carrier 1972) and must be broken before mining can take place. Although it is the usual terrestrial practice, chemical explosive blasting appears to be prohibited by the high cost to transport the explosives to the Moon. The ripper or plow greatly increases machine working depth. It has already been established that the slusher, unlike mobile loading equipment, is independent of traction. This traction independence allows the slusher to break difficult ground while still maintaining a light weight. More lunar geotechnical engineering data is needed, however, and the design of the ripper is unknown. The ripper probably needs an attached weight to force it into the regolith. A plow may be better than a ripper, as its shape helps pull it into the soil, making it less gravity dependent.

Two Environmental Factors

In addition to one-sixth gravity, there are two other significant lunar environmental factors worth noting: temperature extremes and electrostatic dust. Temperature extremes are easily answered by shutting down during the lunar night. Heating selected equipment components is feasible, if more expensive. Electrostatic dust is more of a problem. Machinery bearings must be protected, a problem exacerbated by the lunar vacuum, where lubricants may evaporate. One significant feature of the slusher is that it uses very few bearings, even in the mobile version. Lunar bearing designs and lubrication methods must be developed regardless of the mining method used.

Machine Specifications and Fleet Mix

The specifications and fleet mix I present are for the mobile lunar slusher. The reader should note that alternative methods, such as the stationary slusher, were included to illustrate lunar mining design problems and are not specified here. The data given below are for the proposed baseline mobile lunar three-drum system.

The needed raw material for a 100-metric-ton LOX-to-LEO project is 40 000 metric tons. The machine specified below is oversized by a factor of 2.5 or a yearly rate of 100 000 metric tons. This oversizing is to ensure the production is easily accomplished, while demonstrating that a significantly oversized machine is relatively lightweight. Even with this large oversizing, the hourly production is about 25 metric tons per hour. This rate is close to the lowest rate shown on the production table of one manufacturer.

Yearly production100 000 metric tons
Span and reach50 meters
Mined depth2 meters
Scraper capability2 cubic meters
Mobile slusher weight4.5 metric tons
Auxiliary vehicle weight1.5 metric tons
Ballistic transporter1 metric ton
Spare parts and tools2 metric tons
Operation and maintenance2 people
Foundry (optional)5 metric tons
Total weight (without foundry)9 metric tons
mobile slusher1
auxiliary vehicle with
small multipurpose crane
ballistic transporter1

Lunar Mining Operations

Production Profile

The baseline self-propelled slusher excavates a triangular area 50 meters in base and height. At a mining depth of 2 meters, approximately 9000 metric tons are excavated per setup. Approximately one setup per lunar day yields a yearly raw material production of 100 000 metric tons. Mining would cease during the night, as the extremely low temperatures would make operation difficult. But milling could continue, as the mill is more easily protected from the environment.

Modular Components

Every opportunity should be takento divide the slusher (and other equipment) into modular components. The modules should be as interchangeable and transportable as possible. Two general types of modules envisioned are large functional modules, such as mining units, material crushers, and electrostatic separators, and small equipment modules, such as electric motors and power distribution panels.

Modularity increases flexibility and reduces downtime without adding equipment weight.

  1. A component needing repair can be replaced on site with a working unit. The defective unit can then be repaired onsite or in the shirt-sleeve environment of a pressurized shop.
  2. Quick component replacement allows production to continue when one component breaks. When many components break, a producing unit can frequently be assembled from the remaining units.
  3. Catastrophic failure of a module, such as an electric motor, will not hamper production, as the whole unit can be replaced.
  4. Increasing production simply means adding more components rather than redesigning or rebuilding the existing facilities. Upgrading one part of the operation with new designs or technology is facilitated by replacing the old components with the new.

Accomplishing modularity is relatively easy in small-production mining facilities-: (By terrestrial standards, the lunar slusher operation is very small.)

Auxiliary Vehicle

A small, self-propelled auxiliary vehicle will probably be necessary, even with a mobile slusher or other mobile mining method. It will find use hauling broken components to the repair shop and replacement modules to their operating positions. as well as hauling people and materials back and forth. It should have a crane to aid in constructing habitats and repairing equipment. Adding a small conveyor to the vehicle would allow it to heap up Joose regolith for habitat shielding. This general-purpose vehicle will be smaller than the vehicle required to move a stationary slusher from site to site.

Shop Facilities

A pressurized repair shop would facilitate complex repairs by providing a shirt-sleeve environment. There is no good reason to rewind an electric motor in a vacuum. Since lunar dust is ubiquitous and insidious, some system for removing dust from the shop and its equipment must be provided. Equipment from the outside must be cleaned of dust before it enters the shop.

However, a shop would add significant launch weight unless it could be fabricated on the Moon. launch weight considerations dictate a careful mix of tools, equipment, and spare parts for the shop. The shop and repair activities are there to keep the mine operating while helping to keep transportation costs for tools and spare parts to a minimum.

In addition to tools and spare parts, the shop could eventually have a small adjacent foundry to cast pulleys, bearings, and other easily fabricated parts. The foundry will probably not be in the shop but outside in the vacuum. This plan assumes lunar metal production.

Fiberglass ropes of lunar origin to replace Earth-made cables are also candidates for early lunar manufacture, as glass is a byproduct of LOX production. Glass manufacturing methods were not considered here.

Mine Waste Disposal

Depending on required products and milling processes, some fraction of the mined material will be waste which must be removed from the production area. This fraction can be quite significant (e.g., terrestrial copper operations yield only 10 kg of product per metric ton of ore; thus, 1990 kg of that tonne is waste). The LOX-to- LEO project will generate two types of waste. Fines waste is the soil fraction rejected by electrostatic separation. Slag waste results from the smelting process. Production of liquid oxygen from regolith that is 10 percent ilmenite will generate mostly fines waste, on the order of 90 percent of the material mined or 36 000 metric tons per year. Providing a vehicle for waste disposal would add significant launch weight, and the waste disposal options must be studied.

Robert Waldron and David Carrier have both proposed a ballistic transport mechanism that could be usable in lunar mining. It is well suited to removing fines waste. Using a simple mechanism such as an Archimedean screw or conveyor flights, it is possible to ballistically transport fines waste several hundred meters away from the production area. Their preliminary calculations indicate that the mechanism could be built at a reasonable weight. A ballistic transporter, along with a storage and feed bin, could be added as part of the mill module or as a separate module. The ballistic transporter could also be used to heap up material for habitat shielding.

Ballistic transport of the glassy slag waste from the smelting of ilmenite will be more of a problem. For regolith that is 10 percent by weight ilmenite, the slag waste produced will be on the order of 80 percent of the ilmenite or 3200 metric tons per year. Slag waste will contain much larger and more angular particles, which are less suited to ballistic transport. If the iron is extracted, the slag waste drops to 40 percent or 1600 metric tons per year. These figures are based on 100-percent separation efficiencies.

From A Baseline Lunar Mine by Richard E. Gertsch. Collected in Space Resources NASA SP-509 vol 3

     Continuing the series, this is a look at what to do next after water mining becomes routine and a network of fuel transfers is available. This post assumes that Lunar water mining is operational, but that material from Mars is not guaranteed.

     While harvesting ice is fairly straightforward and something I expect we can automate, surveying mineral resources for efficient mining is altogether different. It would still be possible to do without humans on-site but I believe sending experts would be more effective. A program of manned exploration alongside current state of the art automation would expand our knowledge of the Moon and our experience with autonomous mining. Still, the general program I will describe could be done with or without people on site.
 Actually making use of these materials will require human hands. We do not have the automation technology available to perform complex assembly, particularly in a challenging environment. Individual steps will be automated as much as feasible, but in the near term most manufacturing processes will require a crew.

     Operations would be based at the polar water processing center. An abundant supply of fuel and power is available here along with frequent visits by fuel tugs. Hardware from Earth would be delivered to LEO, boosted to EML1 by a cargo tug and then relayed to the pole by another cargo tug. Some types of processing hardware would be left here, to become part of the resource processing infrastructure. Other types would be used on location to preprocess and reduce the mass that needs to be returned to base. Details depend on what specific hardware and process is being used.
     Travel would be by cargo tug, using suborbital hop flights. Surface transport (rover or moon buggy) might reach 1-2° (30-60km) from the pole, but the terrain is rugged. It would be possible to cut a rudimentary road to allow for safer ground travel if a valuable deposit was found. Until then, exploration would be done by hopping to a target site, mapping / probing the area, taking samples, then hopping back to base. Travel to points within 23° (698km) of base would require only 2km/s round-trip. An 83° (2518km) range would require 3km/s, while access to the opposite pole (5461km) would require 3.4km/s. The reference tug can deliver 29 tons to EML1 or could carry 20 tons to any site on the surface and 60 tons back for 63 tons of fuel. For sites within 700km of the pole that same 20-ton exploration package could bring back 80 tons of ore for 46 tons of fuel.

     The easiest initial harvest would be to run magnetic rakes through the regolith and collect iron nodules. The result would be bags of nearly pure nickel-iron grains. This should be done in the immediate area of the pole first to build up a stock of metals with minimal processing requirements. This can be done fairly easily by automated rovers and should be pursued while other exploration activities occur. Even if no other mining is performed, the material collected with this approach would yield iron and nickel as structural materials suitable for 3d printing (via SLS or thermal deposition of carbonyl), plus platinum group metals to use as electrode plating and catalysts.

     Most Lunar mining schemes are intended to produce oxygen, since most were designed before the widespread existence of water ice on Luna was known. (See for example this NSS article.)With such an abundance of water it makes little sense to go to a lot of effort specifically for O2. Instead, the two main targets will be aerospace metals (aluminum and titanium) and incompatibles (phosphorus, potassium, rare earths, etc.).

     Titanium-rich soils contain the mineral ilmenite, an iron titanium oxide. Much research has been done on this as a resource for producing oxygen and the general distribution and concentration of ilmenite at the surface is known. Concentrations can be as high as 10% titanium by mass, while the mineral itself is 31.6% titanium by mass. Impact sorting can produce an enriched feedstock of 90% ilmenite grains, which is 28.4% titanium by mass. This input would be reduced with hydrogen to form iron metal, titanium dioxide and water. The titanium dioxide is electrochemically extracted in a cell with molten calcium chloride and a carbon anode under the FFC Cambridge process, or is carbothermically reduced and then chloride-processed in the MER process.
         Aluminum-rich soils are formed of anorthosite, a calcium-rich plagioclase composed mostly of CaAl3Si2O8 with a small fraction (less than 5%) of NaAlSi3O8. This material is around 25% aluminum by mass. There are a few options for processing; countercurrent hydrochloric acid with fluoride ion (producing aluminum chloride), calcination (with or without carbon), arc melting and reaction with hydrogen. Partially refined aluminum (reduced alloys of aluminum, iron and silicon) can be further refined by the subhalide method, where aluminum chloride (AlCl3) at 1000-1200 °C reacts with aluminum metal to form aluminum subchloride (3 AlCl); aluminum metal is deposited in a condenser and the AlCl3 is recycled. The traditional ALCOA process can also be used, but this equipment is not easy to scale down and is very energy-intensive.

     Incompatibles are concentrated in KREEP (meaning potassium, rare earth elements and phosphorus). This material is about 0.4% phosphorus and 0.8% potassium by mass (present as oxides, each about 1% by mass). It also contains relatively high concentrations of rare earths, including 15-20 ppm thorium and about the same mass of lithium. This material is mostly located in Oceanus Procellarum and can be seen clearly in maps of the Moon's thorium concentrations. There are four specific craters with very high readings that are worth investigating; all are in the Earth-facing northern hemisphere.
     The main goal is to harvest potassium and phosphorus for hydroponics. Less-useful minerals would be removed and the resulting leftovers would be available for later intensive processing (most likely zone refining). Potassium oxide can react violently with water, so care must be taken; bioavailable forms are as chloride or nitrate. Phosphate can be purified by converting to phosphoric acid with additional processing, resulting in either ammonium phosphate or calcium phosphate.

     With a ready supply of structural metals, parts needed for spares can start to be sourced entirely from lunar materials. New hardware built on the Moon won't be under such extreme pressure to minimize mass, meaning the locally-produced equipment can be built heavy to improve MTBF and reduce spares. Simpler but less efficient PV panels can be constructed using all local materials, expanding the base's power supply. Light metals shipped to EML1 can be used to build extremely light structures that would fall apart under chemical acceleration; this capability would be a significant advance for electric propulsion and possibly for light sails. Oversized propellant tanks and other structures could be built to dimensions that could not be launched from Earth.

     This step represents the first major advance in self-sufficiency. No longer dependent entirely on parts and fertilizer from Earth, the facilities offworld can expand with minimal additional launched mass. There is a strong demand for carbon, nitrogen and chlorine, all of which are available in bulk on Mars. Still, the facilities begin to provide services to customers back on Earth, mostly as satellite maintenance but increasingly for satellite construction.


Part of my series on countering misconceptions in space journalism.

Water, the staff of life. What a shame, then, that the Earth’s Moon always seemed to be so dry! So dry, in fact, that in most places if there was concrete available it would be a better source of water than average moon dirt.

Not everywhere, though. For decades now, permanently shadowed craters near the pole have been thought to trap volatiles, including water, in their intense cold. More recently a series of missions have confirmed the presence of some water. Scarcely a month goes by without some breathless headline exclaiming NASA’s (re)discovery of moon water, complete with some Kerbal speculative art.

According to some enthusiasts, moon water changes everything. Yes, the moon is still a barren remote frozen boiling irradiated cratered hellscape, but since there’s some water near the poles, we can build bases with fountains and swimming pools, and make money by selling the water!

I’m actually good with all of this, except the last part. The problem is that there’s not that much water and it’s not that valuable.

First, the quantity. No-one actually knows how much water is there, but if we assume that the bottom of the relevant craters could be lined with 100m of frozen comet rubble, with a water concentration of 10%, then there could be a billion tons, or one gigaton, at each pole.

When I think of water I think of a nice lake full of fish. Instead, we have some cryogenically cold frozen mud that’s full of shards of metals, including heavy metals, and other crud. Still, it’s a lot better than the rest of the moon, which has water abundance of around 200ppm, and is drier than fresh dessicant.

One gigaton of water sounds like a lot, but it’s only a cubic kilometer. For comparison, there are many reservoirs on Earth that hold more water. Converted into hydrogen and oxygen it could fuel all of Earth’s combustion-powered vehicles for a couple of months. And then it’s gone. This fossil water took billions of years to accumulate, and it’s a non-renewable resource.

The second problem is that it’s not that valuable. Lunar water mining advocates envision a mine that produces rocket fuel and transports it to other places where it’s needed more, such as LEO. Here a tug could be fueled to transport geostationary satellites to their final orbits.

It’s worth noting here that water isn’t rocket fuel, it’s rocket exhaust. Turning water back into rocket fuel requires putting all the energy that fabulously energetic fuel generated back into the water, plus some extra for inefficiency’s sake. At 10 kWh/kg of hydrogen and oxygen, generating enough fuel to transport 100 T/month back to Earth would require an average of 30 MWh per day, or about 1.2 MW continuous power. For comparison, the ISS solar arrays generate about 100 kW when in full sun.

Unfortunately for this business model, the assumption that GEO launch cost would remain above $35k/kg has proven false. Indeed, continuous launch innovation on Earth has driven launch cost down by an order of magnitude, crushing the lunar water export model. For a more thorough analysis, see my blog on the topic. Fundamentally, the value added per kg of water or hydrolox fuel is much too low to be a good business, even on Earth!

Despite the hype, the fundamental economics are well understood by the mining industry. We don’t have to worry about a resource rush suddenly occurring, complete with moustache twirling monocle-clad capitalists and grieving moon environmentalists.

That aside, major conceptual work on lunar mining continues to this day. A source of water (and other light elements) is important for a lunar base, and lunar water fuel is great for flying hoppers around on the moon. Reducing mass requirements and shipping costs for a lunar base is awesome, but it won’t pay for the base itself. For that, we need something that has a very high demand and value density on Earth that can only be obtained on the Moon.

So when you see articles about lunar water, remember that it’s a very limited resource in a very particular place, and there’s no market demand for it.

From LUNAR WATER IS NOT THAT EXCITING by Casey Handmer (2019)

Martian Mining


      Jeffrey Allen is the principal investigator on a project “Low Mass, Low Power, Non-Mechanical Excavation of Gypsum and Other Evaporites and Water Production on Mars.”
      This two-and-a-half-year project, funded for a total of $500,000, will investigate whether robots sent to Mars can use powerful jets of water to excavate gypsum, blast the rocks to disintegrate them, and heat the gypsum particles to release the water bound within mineral’s crystal structure. This could be a way to expeditiously make more water and oxygen for human consumption and to make rocket fuel on Mars.
     This work aims to create a way for NASA (or a space exploration contractor) to send humans to Mars with enough water, oxygen and rocket fuel for the trip out, knowing that there will be enough water, oxygen and rocket fuel waiting on Mars for the astronauts to use on their trip home to Earth.

Breaking It Down

     If mining machinery breaks down on Earth, fixing the problem is expensive, but it’s also just a phone call away. There are no mechanics on Mars; therefore, coming up with a way to mine that causes the least wear on machines was the starting point for a project occurring millions of miles away.
     “How could you mine hard rock knowing these machines have to operate for many years without maintenance?” asks van Susante, senior lecturer in mechanical engineering-engineering mechanics and faculty advisor to the Mining Innovation Enterprise (MINE) team. “The problem is the metal that exerts the force to break the rock. Metal wears down or breaks off, requiring maintenance. We’re trying to eliminate that part of it. We came up with idea to use a water jet, or some other gas or liquid, that we can spray at high pressure at the rock. It’s a new idea in space that hasn’t been proposed before.”
     Working with Tim Eisele, assistant professor of chemical engineering and endowed faculty fellow, and students from the MINE team, van Susante is creating a sealed chamber in the Ore Separation Laboratory and Benedict Laboratory equipped with water jets to disintegrate gypsum samples. The second step is to transport the resulting slurry for separation to remove suspended particles and supply the water back to the pressure washer.
     Their plan is to feed water back into the system until there is a surplus, at which point the water will be stored. The water can then be separated and combined with carbon from the Martian atmosphere to create methane for rocket fuel andliquid oxygen is a byproduct.


(ed note: I'm probably wrong, but it seems to me the mudskipper trick might have applications to the fluid gypsum chisel)

      A fish that uses water as a sort of tongue to feed on land could shed light on how animals with backbones first invaded land, researchers say.
     One of the most pivotal moments in evolution occurred when a few pioneering fish left the waterabout 350 million to 400 million years ago. These fish evolved into the first tetrapods (four-legged land animals), which ultimately gave rise to amphibians, reptiles, birds and mammals.
     To figure out how ancient animals made this shift to land, scientists typically investigate how the limbs of the first tetrapods evolved over time. However, biomechanistKrijn Michel at the University of Antwerp in Belgium and his colleagues suggest that investigating how early tetrapods learned to eat on land is equally important to understanding this key point in evolution.
     In the water, fish generate suction with their mouths to help draw in food with the help of a neck bone known as the hyoid. On land, sucking in air to swallow food proved impractical, so tetrapods instead evolved tongues supported by the hyoid that help guide food down their throats. However, much remains unknown about how tetrapod hyoids and tongues evolved.
     To learn more about the evolution of tetrapod feeding, the scientists investigated modern amphibious fish known as mudskippers that dine on land. Mysteriously, these fish emerge onto land with their mouths filled with water.
     Now, Michel and his colleagues have found that mudskippers use their mouthfuls of water "like a tongue to capture and swallow food on land, a finding that may give us a glimpse into how the very first land vertebrates evolved from fish 400 million to 350 million years ago," Michel told Live Science.
     The researchers experimented with five mudskippers from Nigeria, using high-speed video cameras and X-ray scanners to record the fish feeding on shrimp.
     Results showed that the mudskippers fed by first exuding water from their mouths and then quickly sucking it back up once it submerged the food. Essentially, the water acted like a tongue.
     When using this "hydrodynamic tongue," the mudskippers moved their hyoids upward, "more or less the opposite of what fish do to feed underwater," Michel said. However, the mudskipper hyoids behaved much like how those of primitive tetrapods such as newts do during feeding.
     The researchers suggest that early tetrapods may have used hydrodynamic tongues when first moving onto land, and evolved fleshy tongues later to gain further independence from the water.
     Michel and his colleaguesdetailed their findings online March 18 in the journal Proceedings of the Royal Society B.

by Charles Q. Choi (2015)

 Excavation on Earth sometimes uses explosives to break up rock or densely-compacted soil. This can be less expensive than using a drill bit or other grinding or impact tools if the explosive is cheaper than the cost of wear on the drill.

 On Mars, drilling and grinding tools shipped from Earth are enormously expensive. They could be made from local materials, but not easily and not as an automated process without significant advances. Explosives are in the same boat; anything shipped from Earth is super expensive. Nitrogen is about 1% of the Martian atmosphere, but in a form that requires substantial chemical processing. (Nearly all industrial explosives use chemicals with nitrogen bonds as the source of their explosive power).

 One resource that is plentiful is carbon dioxide, CO2. This can be collected directly from the atmosphere and frozen into dry ice pellets. The expansion ratio of CO2 is 845 (1 cc of dry ice forms 845 cc of CO2 gas at standard conditions). A small drill or punch can be used to bore a hole into the work face; CO2 pellets are pushed into the hole and a metal rod with a heater on the end plugs the hole. Heat is applied, sublimating the dry ice into gas and building up a lot of pressure quickly. Used properly, this will cause the surrounding soil to lose cohesion and fragment into clods.

 I don't think this would work well on solid rock but it could be very effective on hardpan or other tightly-packed soils where a grinder or impact tool would endure a lot of wear. This could be useful in particular for excavating a habitat shelter; if the equipment can excavate to bedrock using CO2 fracturing and simple bucket or augur tools then the required mass, power and spares can be minimized. Another place where it could be useful is if the surface soil layers hold less water than expected for ISRU operations. Surface soils are loose and easily scooped up with a blade or bucket, so the harvesting equipment will be minimal. Adding a CO2 system like this as a contingency would allow the harvesters to dig deeper and break up ice-bearing soils without requiring any heavy equipment. The force of CO2 expansion should be strong enough to break up solid ice as well, so if a solid layer of ice is encountered it would be valuable rather than difficult.

 An expanded use for this might be as a drilling rig using gaseous CO2 as the working fluid, similar to the way shallow wells on Earth can be drilled using water and simple tools. If any soils too dense to be carried away by the gas are encountered they can be fractured by gas expansion; the equipment could be designed to do this without needing to back out the drilling pipe (one-way valve at the end strong enough to survive the gas expansion. If actual solid rock is encountered then a small amount of water can be pumped into the well and frozen at depth, using the expansion of ice to fracture the material. This would be a much slower process but considerably more powerful. This type of drilling is different from taking core samples; it would be intended to reach water ice to be melted and pumped out just like a well on Earth.

 Presumably the same mechanism could be used in outer planet probes using methane ice (melts at 90.7 K, boils at 111.7 K) or nitrogen ice (melts at 63.2 K, boils at 77.4 K) depending on local average temperatures. These two don't sublimate but would have to be heated through a liquid phase; still, the temperature rise required is only 21 K for methane and 14 K for nitrogen. Probes to moons beyond Jupiter and to Kuiper belt objects might use this as a lightweight method of digging shallow craters and collecting subsurface samples for analysis, using heat from an RTG directly as the power source.

 Another way to accomplish the same thing might be simply to use a laser to deliver a pulse of heat to the end of the hole, causing any volatiles to vaporize and expand vigorously. This would require a material sturdy enough to contain the gases while being transparent to the laser, and would require soil with enough trapped volatiles to produce a useful force. It would also need a fair amount of power for the laser.

From MARS: CO2 MICROBURST EXCAVATION by Chris Wolfe (2015)

Harvesting Gas Giants

Outer Planet Atmo Composition (by volume%)
PlanetHydrogenHeliumHelium 3MethaneOther
♃ Jupiter89.9%10.2%0.00102%
♄ Saturn96.3%3.3%0.00033%0.4%
♅ Uranus82.5%15.2%0.00152%2.3%1.0%
♆ Neptune80.0%19.0%0.0019%1.0%

First off be aware that there are issues with talking about extraterrestrial sources Helium-3 as an motivation for a huge population of people living in space.

The whole thing started in 1973 with the studies on Project Daedalus. This was an unmanned starship meant to probe Barnard's Star. Since it was planned to reach a peak velocity of 0.12 c you can see it needed gargantuan amounts of fuel. Even then it had to use staging. And it didn't slow down either, it just shot through the Barnard system at 12% lightspeed while frantically snapping pictures. But I digress.

The point is it required something even more powerful than Project Orion nuclear fission pulse units, it had to use deuterium-helium 3 nuclear fusion. Using lots of helium 3. As in "more helium 3 than exists on Planet Terra".

The study figured it could mine helium 3 from the atmosphere of Jupiter, using harvesters supported by hot-air balloons called aerostats (the only thing lighter than a mostly hydrogen atmosphere is hot hydrogen). They calculated it wouldn't take more than 20 years or so to gather the amount Daedalus required. At a rate of 1,500 metric tons of Helium 3 per year! Other studies that focused on just supplying Terra's energy needs suggested that you could get away with only 450 to 500 metric tons per year.

Helium 3 is available in Lunar regolith, but only at levels of 5 to 100 parts per billion by regolith mass (5×10-9 to 1×10-7). Helium 3 in the atmosphere of Jupiter and Uranus is more like 1×10-4 Helium 3 to (common garden-variety) Helium 4 ratio, or 1,000 to 100,000 times greater than Lunar regolith. As you can see from the table, Saturn has much less helium than Jupiter and Uranus.

On the other hand, Luna is quite a bit closer to Terra than Jupiter is. Transporting Helium 3 from the gas giants is going to take years for the trip one-way. In addition, massive brute-force crudely-designed manned tractors slowly chugging away scraping up Lunar regolith are easier to design, manufacture, and maintain. Compared to, for instance, featherweight over-engineered hypersonic robot scoop ships braving gargantuan wind-shear and high gravity eight hundred million kilometers from Terra.

Gas giants also have methane, which contains nitrogen, which is in short supply off Terra but absolutely vital for agriculture. Other attractive resources include:

Hydrogen, helium, methane
Trace gaseous elements (present at parts per million levels 10-6)
Helium 3, hydrogen deuteride, ethane
Ices deep within atmmosphere
Hydrogen, hydrogen deuteride, methane, ammonia, water

Outer Planet Transits
Orbital ΔV
to Terra
Hohmann ΔV
♃ Jupiter43 km/s24 km/s
♄ Saturn26 km/s18 km/s
♅ Uranus15 km/s15 km/s
♆ Neptune17 km/s15 km/s

Carting this stuff back to Terra is going to be expensive in terms of delta V. Those gas giants are really far away.

What's worse is the delta V for whatever vehicle is jumping in and out of the atmosphere to scoop up the good stuff. At Jupiter, a solid core nuclear thermal rocket would need a freaking mass ratio of 20 just to escape! It won't be able to lift much of a cargo with that ugly figure. Saturn is more reasonable, a solid core NTR scoopship can manage with a mass ratio of 4.

The tankers will probably need nuclear powered ion drive propulsion as a minimum. Why?

Exhaust velocity is delta V divided by natural log of mass ratio. Assume that the maximum economical mass ratio is 4.0 (i.e., 75% propellant). This means the tanker rocket will need a propulsion system with an exhaust velocity of at least 17,000 meters per second. Looking at the drive table, a chemical rocket is far too weak, same goes for a solid core nuclear thermal rocket. In the near term you are probably going to use a VASIMR or ion drive.

Both need electricity and plenty of it. And past the orbit of Mars, a solar cell array is not practical. Sunlight at Jupiter is about 0.04 as strong as it is at Terra. And at Neptune it drops to 0.001. You are going to need nuclear energy or better for your ion drive.

Of course if you have 3He fusion power light enough to use on a spacecraft, you will be all set. Just tap a bit of your cargo.

Hydrogen propellant is no problem. The harvesting operation is scooping hundreds of thousands of tons of the stuff and throwing it away while sifting out the precious atoms of 3He. Or if that is too expensive to lug up the gravity well, the gas giants all have plenty of moons or rings just chock full of frozen water ice.

Now, if you are going to be shipping 500 metric tons of 3He to Terra per year, you probably are talking about several hundred flights. Which is a lot.

Most Traveller fans are familiar with the concept of harvesting gas giants because it is enshrined in the game under the name "wilderness refueling." This is a starship obtaining hydrogen fuel by scooping it from the atmosphere of a convenient gas giant. Starships usually obtain fuel by purchasing it from a starport. Wilderness refueling makes sense if the starport fuel is too expensive, or if you are indeed in an uninhabited wilderness solar system and there are no starports.

Keep in mind that if the gas giant is inhabited by native aliens, having your hypersonic starship making a screaming scoop run through their real estate could really cheese them off.

How did the wilderness refueling concept get into the Traveller game? Because the creators of Traveller liked the classic Niven & Pournelle novel The Mote In God's Eye, and Niven & Pournelle liked a plastic model called the Explorer Ship Leif Ericson:


Long ago we (Larry Niven and Jerry Pournelle) acquired a commercial model called “The Explorer Ship Leif Ericson,” a plastic spaceship of intriguing design. It is shaped something like a flattened pint whiskey bottle with a long neck. The “Leif Ericson,” alas, was killed by general lack of interest in spacecraft by model buyers; a ghost of it is still marketed in hideous glow-in-the-dark color as some kind of flying saucer.

It’s often easier to take a detailed construct and work within its limits than it is to have too much flexibility. For fun we tried to make the Leif Ericson work as a model for an Empire naval vessel. The exercise proved instructive.

First, the model is of a big ship, and is of the wrong shape ever to be carried aboard another vessel. Second, it had fins, only useful for atmosphere flight: what purpose would be served in having atmosphere capabilities on a large ship?

This dictated the class of ship: it must be a cruiser or battlecruiser. Battleships and dreadnaughts wouldn’t ever land, and would be cylindrical or spherical to reduce surface area. Our ship was too large to be a destroyer (an expendable ship almost never employed on missions except as part of a flotilla). Cruisers and battlecruisers can be sent on independent missions.

MacArthur, a General Class Battlecruiser, began to emerge. She can enter atmosphere, but rarely does so, except when long independent assignments force her to seek fuel on her own. She can do this in either of two ways: go to a supply source, or fly into the hydrogen-rich atmosphere of a gas giant and scoop. There were scoops on the model, as it happens.

She has a large pair of doors in her hull, and a spacious compartment inside: obviously a hangar deck for carrying auxiliary craft. Hangar deck is also the only large compartment in her, and therefore would be the normal place of assembly for the crew when she isn’t under battle conditions.

The tower on the model looked useless, and was almost ignored, until it occurred to us that on long missions not under acceleration it would be useful to have a high-gravity area. The ship is a bit thin to have much gravity in the “neck” without spinning her far more rapidly than you’d like; but with the tower, the forward area gets normal gravity without excessive spin rates.

And on, and so forth. In the novel, Lenin was designed from scratch; and of course we did have to make some modifications in Leif Ericson before she could become INSS MacArthur (from novel The Mote in God's Eye); but it’s surprising just how much detail you can work up through having to live with the limits of a model.

ed note: so please follow my line of reasoning here.

The Galactic Cruiser Leif Ericson was originally a plastic model that came out in 1968.

Larry Niven and Jerry Pournelle got a Leif Ericson plastic model. They examined it and tried to design a spacecraft based on it, the INSS MacArthur. The MacArthur was streamlined and had scoops. This meant it was a Cruiser class, capable of independent operations. If need be, it could harvest hydrogen fuel by scooping the atmosphere of a nearby gas giant. In other words: In-situ Resource Utilization.

In 1974 Niven and Pournelle wrote the science fiction classic The Mote in God's Eye. It featured the INSS MacArthur.

Marc Miller read The Mote in God's Eye. He thought the fuel scooping ability of the MacArthur was a good idea. So when he wrote the Traveller RPG in 1977, he put that into the game under the term "wilderness refueling."

So what I am telling all you fans of the Traveller RPG is the reason there is wilderness refueling in Traveller is because of the plastic model Leif Ericson!

From BUILDING THE MOTE IN GOD'S EYE by Larry Niven and Jerry Pournelle (1976)

      The Pax Astra Royal Navy frigate Intrepid falls toward Saturn, inexorably drawn into the planet’s gravity well as the vessel continues its long deceleration burn.

     Sixty meters in length, Intrepid is relatively small for a ship with a maximum range of nine a.u.’s. Designed for military missions rather than exploration or trade, few accommodations have been made for passengers and none for freight, other than the two missile pods slung on either side of its forward hull and the manta-like shuttle moored beneath its wasp-waisted midsection. Imagine a half-liter bottle—the payload module—with its spout glued to that of a three-quarter liter bottle—the engine module—and you essentially have the warship’s architecture.

     Mounted beneath the forward module is a large round aerobrake shield (used for wilderness refueling). Its ceramic tiles, each a different color, have been carefully arranged so that they form the warship’s figurehead: an angel with a sword, her wings spread wide as if flying through space.

     Intrepid’s nuclear-pulse main engine has fired continually ever since the ship left the Moon two hundred and seventy-five standard days ago, its lasers fissioning the deuterium pellets constantly fed into the reactor chamber, causing the uninterrupted string of tiny nuclear explosions which gradually accelerated the ship, at the end of its boost phase, to nearly one-tenth light speed. As Intrepid passed through Jupiter’s orbit one hundred and sixty-eight days ago (i.e., at the journey midpoint), its crew flipped the ship around until its bell-shaped engine nozzle was pointed in the direction of flight. Ever since then, the ship has been applying the brakes as a long prelude to entering Saturnine space (a Brachistochrone trajectory).

(ed note: the Intrepid arrives at Saturn)

     “Very well.” (Captain) Kinnard loosens his seat straps as he rotates it to face the bow windows. “Isidore, initiate rollover maneuver. Jon, finalize trajectories for Saturn atmospheric refueling and Titan rendezvous. Cayenne, ship status?”

     Kinnard punches up the course that Jon has laid in. Studying it, he absently smiles, satisfied that the navigator has done his job. Intrepid arrived at Saturn with its fuel tanks nearly depleted; this was a necessary sacrifice for the constant thrust that approached one-gee when the ship began its midcourse deceleration. However, the frigate was specifically designed for refueling by an aerobraking maneuver through the planet’s upper atmosphere, during which gaseous helium-three would be scooped from the thin stratospheric layer high above its swirling cloudtops. This raw fuel source was less efficient than deuterium pellets extracted and refined from the Moon’s regolith, but it was enough to get Intrepid back home. Indeed, his crew had safely performed much the same maneuver during the Callisto mission two years ago.

     Jon has laid in a trajectory that would graze the top of Saturn’s atmosphere below its rings. Before Intrepid made its refueling run, it would drop off its shuttle, Excalibur, near Titan. By the time he and his crew were viewing the rings of Saturn from below, the landing party would be on Titan’s icy surface, trying to discover why all contact had been lost with Huygens Base and the Hershel Explorer.

(ed note: The captain briefs the crew. Apparently Huygens Base and the Hershel Explorer were attacked by some hostile group and utterly wiped out. For all they know the "hostile group" could be invading aliens. Upon learning this, Lt. Col. DeSoto, leader of Bravo Squad and tasked with the landing party, has a problem with the mission plan )

     (DeSoto says) “As it stands now, you intend to drop my people on Titan before proceeding to Saturn. I understand the reasons for doing it this way. You need to refuel as soon as possible.”

     (Captain Kinnard says) “But you have a problem with it.”

     “From Titan flyby to return rendezvous with Excalibur, there is a twenty-six-hour stretch. That’s the time, at bare minimum, that’s required for Intrepid to make its run and meet up with the shuttle. During that period my team will be on Titan, with no backup from orbit.”

     Kinnard frowns. “Excalibur is outfitted for a two-week stay, if necessary.”

     “In terms of basic life-support, sure. But the shuttle is not equipped with its own weaponry. Given the presumption…” DeSoto hesitates, then corrects herself. “Given the likelihood that there are no survivors at Huygens Base, I consider it imprudent for Intrepid to be so distant from Titan.”

     Kinnard absently caresses his chin with his forefinger. She has a point. Once Intrepid goes deeper into Saturn’s magnetosphere, radio contact with the landing party would become progressively difficult, finally impossible as the ship goes around the planet’s far side. If Bravo Squad ran into problems, it could be several hours before Intrepid found out, and even longer before it could respond. More to the point, though, Intrepid also carries two orbit-to-surface missiles. If there is trouble on the surface, Bravo Squad can call in a space-strike as a last resort.

     And without a doubt, there’s something hostile on the Galileo Planitia. Leaving eight men and women down there—however well-armed and trained they may be—could be a fatal risk.

     Isidore is already recalculating Intrepid’s course on his wristcomp. (Captain Kinnard says) “Jefe, can we adjust the trajectory to put us in orbit around Titan?”

     Kinnard considers it for a moment. “Okay,” he says, “go topside and tell Jon to lay it in. We’ll do the run after we get Excalibur back aboard. Tell Marie to alert FLTCOM of the change.”

From KRONOS by Allen Steele (1996)

In Traveller, all ships use hydrogen for fuel. Starships include a faster-than-light drive, which is increases both the mass and the price tag of the ship. System defense boats (SDB) are military ships that have no FTL drive, which makes them lower mass and cheaper than a comparable starship.

In military operations logistics is always a problem. When invading an enemy solar system lugging along fuel in the supply train is a logistical nightmare. So invading starship fleets are fond of refueling at gas giants located in the target system.

Which is why it is standard operating procedure for defending fleets to station system defense boats lurking in the gas giant atmospheres. This allows the system defense boats to ambush the invaders.

The other think to remember is that kilogram for kilogram a system defense boat is more heavily armed. Given a starship and a system defense boat of the same mass, the SDB has no FTL drive or fuel devoted to the FTL drive. So the mass a starship allocates to the FTL stuff is mass that the SDB can allocate to more weapons and defenses. Alternatively you can have a SDB with armament equal to a given class of starship, such a SDB will be much cheaper than the equivalent starship so you can afford more of them.

Of course SDB can never leave the solar system they reside at (unless transported by a huge carrier starship), but generally this is not a problem for a defensive military ship. The major exception is if the solar system has to be abandoned, then the SDB will have to be abandoned as well (and probably scuttled).


The purpose of my first post on this topic was simply to run some numbers and see how long starship refueling takes and how large starship squadrons might go about it. I found that the minimum specifications for squadron (10% total tankage on partially streamlined tankers or tenders capable of gas giant fuel scooping) refueling were a little silly. But now that we had a time frame we could extrapolate for squadrons with more and better tenders. I also mentioned that refueling took several days per Trillion Credit Squadron and brought up the problem of SDBs lurking in a gas giant (almost as beloved a trope as starfighters).

Then Klaus Teufel brought this up:

I think System Defense Boats (SDBs) couldn't effectively ambush refuelers unless the SDBs were really lucky, or there are a lot of refuelers. Jovians are big, and even Traveller atmospheric speeds have limits. SDBs probably live in low polar orbit, rather than atmosphere; dipping in when fuel is low.

Let's crunch some numbers.

Jupiter has an area of 52 billion square kilometers. A fast streamlined starship, let's say it makes Mach 5. If refueling takes 6 hours as I suggested the SDB can intercept starships passing within 36,000 km. That gives an area of 400 million square kilometers or 0.7% of the planet's area. That means you need at least 130 SDBs to cover a gas giant. That's for an intercept by one SBD which is a tall order for the SDB if the opposing task force has any kind of admiral in command. The tenders will either have defenses or escorts (hey, fighters might be a good idea after all!)

If the SDBs are any good at all we're talking 200 mega-credits (Mcr) each, that means you need 26 billion credits for minimum coverage. If you use ten times the number to have a SDB flotilla covering the gas giant completely that 260 billion credits. Ten ships probably won't be enough. Remember the name of the game is High Guard. The rest of the invading starship squadron will be hovering nearby ready to call the wrath of GHU down on your SDB flotilla. Now 260 billion credits is also a lot to spend on a last ditch scorched earth strategy. Maybe if you spent that money on your main fleet the bad guys wouldn't win in the first place? Most planets haven't got many trillions to spend on defense. Likewise most sector navies don't want to spend that much on every planet.

So how do you defend your gas giant?

In a word: nukes.

Read Special Supplement 4: Missiles. Mines are perfectly allowable in that system and fairly cheap. In space even an unguided piece of explosive will hit anything within 2,500 miles. So they must still have some kind of short range guidance and propulsion. Buy a bunch of them. Stick them under balloons. They have an intercept area of 20 million square kilometers and you need 2,600 to cover a gas giant. At the cost of even 100,000 cr. you could buy a few thousand for the cost of a single SDB. Seed the gas giant with them. Use your SDBs to maintain and control them as needed. When the bad guys show up watch hilarity ensue.

Even if an invading starship is moving mach 1 to refuel it cover 24,000 kilometers in the six hours I established for refueling. That means it cut across the engagement areas of at least ten nukes. Even that relatively expensive option is probably only 10 Mcr or less. Again the defender can afford 10 times or more the number of turrets as SDBs.There will probably be more. Instead of a single mine laying under a balloon imagine a remote controlled triple turret with three launchers and a missile magazine.

May I point that nukes are bad in space but they are absolutely terrifying in an atmosphere. In space nuclear weapons mainly damage through x-rays melting your hull. Atmospheres add blast effects to that. This is happening to a tanker starshp or tender starship the owner probably try to save money on. The tanker is probably moving at several Mach. It will not respond well to huge blasts being set off around it.

I always assumed the invading High Guard concerned themselves with incoming attacks while their comrades were refueling. It seems they need to worry about what is below as well as above. Refueling might be a matter of clearing a region of the gas giant and confining your refueling operations there. But by then you've restricted your area of operations and then the defending SDBs have a great chance to find you and raise merry hell.

I said it before but Traveller is about making difficult decisions. Personally I'd chicken out and refuel at the nearest Europa type moon. Quick thaw an area with nukes or lasers and fill them up (starships can easily crack water into fuel and oxygen).

Except you could mine Europa too.

Predictably, when you look more closely at gas giant fuel scooping, the concept has problems. The old Daedalus aerostats made more sense, but you really could not use them for wilderness refueling. Not unless you were prepared to wait for a few years.

Most of the technical reports seem to assume that the scooping will be done at an altitude where the pressure is about one bar, or about the same as atmospheric pressure at Terra sea level.


Mark Fogg

Upon reentry, the airframe has to asborb all the energy that was used in lofting that ship into orbit. So, my scoop ships are diving from high above a Jupiter, heating up in the atmosphere, and ramming all the free fuel into storage tanks. Heat of entry the airframe absorbs, just like a shuttle reentry. Heat of compression? Man, has anybody thought of that? I could see some kind of heat exchangers mounted in delta wings or some such, but you gotta dump a vast amount of heat real quickly or your onboard storage tanks become bombs. None of the online wilderness refueling site discussions seem to cover that.

I work in the oil and gas industry, so I know how it's done in a static installation, but aboard a large aerospace craft making a kamikaze run into a turbulent atmosphere is a whole 'nother set of problems.

Winchell Chung (me)

The question is above my pay grade. Just winging it I'd say a possibility is using extreme open-cycle cooling.

Some of the scooped gas will have to be sacrificed, turned into a heat sink that is then instantly blown out the tail pipe to get rid of the compression heat.

Rob Davidoff

The issue is open-cycle means you may be dumping more coolant than you're taking in. Fancy cooling is a lot of the "secret sauce" in Skylon's SABRE engines—using the liquid hydrogen coming out of the fuel tanks as a sump for the heat of compression created in the "intake/compressor" portion of the engine, which is fine since that same LH2 is bound for an engine where it'll be heated into a gas by combustion anyway.

The issue is that here, you don't have that energy sump., and heat exchangers could easily be saturated by the aerodynamic heating around the ship. I wonder if you might be better off with a system that stays out of the main atmosphere and dangles a winged collector on a rope/pipe down into the air proper. The self supporting length for carbon fiber is 250 km—plenty to be into pretty near-vacuum conditions for the main ship while the collector reeling out below it is into the depths. You can pump the gasses up the "reel" and compress and store at the top, where you get a better radiator performance, and because you're not trying to store as much as you can on one "dive" but instead are operating statically, you don't need the same throughput of gas, reducing the heat pulse to a smaller, more measurable heat rejection rate.

Alistair Young

Hm. From the not-yet-even-back-enveloped-this files, seems to me like you're going to have plenty of stuff to throw away anyway in this operation (at least in my universe, they're mostly gas mining for 2H and 3He, which I expect to involve dumping lots of 1H and 4He).

So, hypothetically, could we use one of the assorted heat pump techniques to transfer heat from the fraction we're keeping into the tailings before dumping them over the side? Even though running that would generate more heat, it might still be overall negative.

Rob Davidoff

Alistair Young, on a similar level of rigor, you don't have a very long window to do all this, so in order to even do that you'd need to be pulling the 2H from the 1H and the 3He from the 4He, then dump the appropriate heat into the appropriate pipe (one to the tanks with its compressors, and then you run the tailings outside that and overboard). Spiking the atmosphere at Mach 20 or something, you don't have a lot of time to do all that.

I think you'd really have to just cast a wide net, grab what you can, and sort it out back in orbit. The basic "dump the heat into the tailings' concept, taken to extremes, becomes the "convection heat exchanges all along the wings" routine.

Constantine Thomas

I don't think scooping actually works as it is commonly imagined — you can't just open up some shutters and suck in stuff while you're zooming through the atmosphere at high velocity — unless you want to use it for a ramjet or scramjet. If you tried that I think the stresses (among other things) would tear the ship apart.

I think the only way that fuel scooping could work without destroying the ship is if you can literally hover in place and suck stuff in.

So it looks like the general point is this: if you need to scoop, do it where the atmosphere is VERY rarefied. Zooming through the cloud decks with your scoops open is just suicide.

Isaac Kuo

There are a number of issues going on here. First off, you ultimately get rid of the heat with radiative cooling. This might be done in a steady state, as in PROFAC, or it could be done along with periodic dipping into the upper atmosphere (elliptical orbit). In the latter case, you can use a "block of ice" to absorb some heat, while melting, during the brief atmospheric passes.

Either way, compression heating is going to mean mining Jupiter is going to look pretty bad compared to mining Uranus. The kinetic energy per kg is proportional to the square of the escape velocity—that means dealing with 9 times the energy in compression heating! It also means pumping 9 times the energy to maintain orbit, and 9 times the energy to get the hydrogen out of the gravity well.

And in any case, mining any gas giant's atmosphere looks pretty bad compared to ice mining small bodies. I'm actually a big fan of atmospheric scooping for mining, but the deep gravity wells involved make it look pretty bad for the ones available here in our solar system.

But assuming you want to do hydrogen atmospheric scooping of gas giants, PROFAC tells you basically what's required. You need some sort of high Isp propulsion to counteract drag. You need a conical scoop to accept thin atmosphere. You need a compressor at the base of the scoop so the gas actually gets "sucked" in rather than just bouncing away. You need to dump the heat of the hot collected gas. While PROFAC ultimately created cryogenic oxygen, that may not be practical for hydrogen. It may be easier to store the hydrogen by chemically binding it to on board carbon.

The most important and counterintuitive thing to know is that the ram pressure of the cone does NOTHING to help you collect the gas. Without the compressor, the pressure will equalize with the (nearly zero) ambient pressure.

Alistair Young

I'm much more inclined to the balloon trick for industrial-scale gas mining, myself, with later advancement to the partial orbital elevator used as a giant straw.

(ed note: the "balloon trick" is to place a gas harvesting unit in the atmosphere suspended by a nuclear-powered hot-air balloon. It gradually accumulates the desired gas, and is periodically visited by tanker rockets. Best for gas giants Saturn-sized and under, otherwise the delta-V for the tanker is uneconomical.

Poul Anderson had a merry set of science fiction stories featuring harvesting Jupiter's atmosphere, collected in Tales of the Flying Mountains. Unfortunately they used scoop ships equipped with handwaving antigravity drives, and they harvested complex chemicals (handwavingly as yet undiscovered by science) that for some handwaving reason could not be synthesized. The mothership had a titanic inflatable external tank which the flock of scoop ships would gradually fill.


"Yes, we are pretty isolated," he said. "The Jupiter ships just unload their balloons, pick up the empties, and head right back for another cargo."

"I don't understand how you can found an industry here, when your raw materials only arrive at conjunction," Ellen said.

"Things will be different once we're in full operation," Blades assured her. "Then we'll be doing enough business to pay for a steady input, transshipped from whatever depot is nearest Jupiter at any given time."

"You've actually built this simply to process ... gas?" Gilbertson interposed. Blades didn't know whether he was being sarcastic or asking a genuine question. It was astonishing how ignorant Earthsiders, even space-traveling Earthsiders, often were about such matters.

"Jovian gas is rich stuff," he explained. "Chiefly hydrogen and helium, of course; but the scoopships separate out most of that during a pickup. The rest is ammonia, water, methane, a dozen important organics, including some of the damn—doggonedest metallic complexes you ever heard of. We need them as the basis of a chemosynthetic industry, which we need for survival, which we need if we're to get the minerals that were the reason for colonizing the Belt in the first place." He waved his hand at the sky. "When we really get going, we'll attract settlement. This asteroid has companions, waiting for people to come and mine them. Home-ships and orbital stations will be built. In ten years there'll be quite a little city clustered around the Sword."

As they glided through the refining and synthesizing section, which filled the broad half of the asteroid, the noise of pumps and regulators rose until it throbbed in their bones. Ellen gestured at one of the pipes that crossed the corridor overhead. "Do you really handle that big a volume at a time?" she asked above the racket.

"No," he said. "Didn't I explain before? The pipe's thick because it's so heavily armored."

"I'm glad you don't use that dreadful word 'cladded.' But why the armor? High pressure?"

"Partly. Also, there's an inertrans lining. Jupiter gas is hellishly reactive at room temperature. The metallic complexes especially; but think what a witch's brew the stuff is in every respect. Once it's been refined, of course, we have less trouble. That particular pipe is carrying it raw."

They left the noise behind and passed on to the approach control dome at the receptor end. The two men on duty glanced up and immediately went back to their instruments. Radio voices were staccato in the air. Blades led Ellen to an observation port.

She drew a sharp breath. Outside, the broken ground fell away to space and stars. The ovoid that was the ship hung against them, lit by the hidden sun, a giant even at her distance but dwarfed by the balloon she towed. As that bubble tried ponderously to rotate, rainbow gleams ran across it, hiding and then revealing the constellations. Here, on the asteroid's axis, there was no weight, and one moved with underwater smoothness, as if disembodied- "Oh, a fairytale," Ellen sighed.

Four sparks flashed out of the boat blisters along the ship's hull. "Scoopships," Blades told her. "They haul the cargo in, being so much more maneuverable. Actually, though, the mother vessel is going to park her load in orbit, while those boys bring in another one—see, there it comes into sight. We still haven't got the capacity to keep up with our deliveries."

"How many are there? Scoopships, that is."

"Twenty, but you don't need more than four for this job. They've got terrific power. Have to, if they're to dive from orbit down into the Jovian atmosphere, ram themselves full of gas, and come back. There they go."

The Pallas Castle was wrestling the great sphere she had hauled from Jupiter into a stable path computed by Central Control. Meanwhile, the scoopships, small only by comparison with her, locked onto the other balloon as it drifted close. Energy poured into their drive fields. Spiraling downward, transparent globe and four laboring spacecraft vanished behind the horizon. The Pallas completed her own task, disengaged her towbars, and dropped from view, headed for the dock.

The second balloon rose again, like a huge glass moon on the opposite side of the Sword. Still it grew in Ellen's eyes, kilometer by kilometer of approach. So much mass wasn't easily handled, but the braking curve looked disdainfully smooth. Presently she could make out the scoopships in detail, elongated teardrops with the intake gates yawning in the blunt forward end, cockpit canopies raised very slightly above.

Instructions rattled from the men in the dome. The balloon veered clumsily toward the one free receptor. A derricklike structure released one end of a cable, which streamed skyward. Things that Ellen couldn't quite follow in this tricky light were done by the four tugs, mechanisms of their own extended to make their tow fast to the cable.

They did not cast loose at once, but continued to drag a little, easing the impact of centrifugal force. Nonetheless, a slight shudder went through the dome as slack was taken up. Then the job was over. The scoopships let go and flitted off to join their mother vessel. The balloon was winched inward. Spacesuited men moved close, preparing to couple valves together.

"And eventually," Blades said into the abrupt quietness, "that cargo will become food, fabric, vitryl, plastiboard, reagents, fuels, a hundred different things. That's what we're here for."

From INDUSTRIAL REVOLUTION by Poul Anderson (1963) Collected in Tales of the Flying Mountains

"You are the captain of the mother ship." Pearson said. "However, we're in orbit now. Only the scoopships are under weigh. And I direct their operations. Under the laws of the (Asteroid) Republic, they're my responsibility. You'll find working for the Jupiter Company is a lot different from an inner-planet merchant run."

"They aren't ordered," Pearson reminded him. "Any pilot may refuse any flit. Of course, if he does it repeatedly, he'll be fired—We can't afford to ship deadheads."

"I know, I know. And yet, well, you asterites are obsessed with economics." The captain lifted a hand to forestall the manager's retort. "I am quite aware of how closely you must figure costs. But there's a ... a callousness in your attitude. You often seem to think a machine is worth more than a human life."

"It is, if several other human lives depend on it."

"And it isn't necessary. You could automate the operation."

"Doubling the capital investment in every scoopship," Pearson said. "Also increasing the rate of loss by an estimated twenty-five percent. Too many unforeseeable things can go wrong down there. An autopilot can act only within the limits of its programming. A man can do more. Sometimes, when he runs into trouble, he can bring his ship back."

"Clear track," said the dispatcher's radio voice. Static buzzed around the words. No tricks of modulation could entirely screen out the interference of Jovian electrical storms. "Good gathering, Tom."

"Roger," said Hashimoto, mechanical response to a ritual farewell, "thanks, and out." His eyes focused on instrument needles, his fingers jumped over switches. The computer clicked and muttered. Otherwise the cockpit was silent, making the beat of blood loud in his ears. He grew conscious of the spacesuit enclosing him, a thick rubbery grip. Its helmet was left off, like its gloves, until such time as an emergency arose. So his nostrils drank smells of machine oil and the ozone tinge that recycled air always has in close quarters. For the minute or two that he traveled in free fall he felt weightlessness: scoopships didn't waste mass on internal field generators. But there was no dreamlike ease to the sensation, such as he had known in other days. The seat harness held him too tightly.

The computer gave him his vectors and he applied power. The nuclear reactor aft was noiseless, but the Emetts of the gyrogravitic generators whirred loudly enough to be heard through the radiation bulkhead which sealed off the engine compartment. Field drive clutched at that fabric of relationships that men call space. Acceleration shoved Hashimoto back into his seat. Maij Girl leaped Jupiterward.

He had a while, then, to sit and think. This interval of approach under autopilot was the worst time. Later the battle with the atmosphere would occupy all of him, and still later there would be the camaraderie of shipboard. But now he could only watch Jupiter grow until it filled the sky. Until it became the sky.

The trouble is, he realized, I'm so near the end of my hitch. I didn 't count the days and the separate missions at first, when I began this job. But now that there's only a few more months to go....

Three years!

He hadn't needed to stay in the Belt that long, as far as his wife was concerned. She wanted desperately to have children, yes, and her frail body would miscarry again and again unless she spent each pregnancy under next-to-zero weight, and obstetrical facilities for that kind of condition existed nowhere but in the Asteroid Republic. (No country on Earth would spend money to establish a geegeeequipped maternity hospital, or an orbital one; anything that increased population, however minutely, was too unpopular these days.) Hashimoto had been more than glad to land a contract with JupeCo that enabled them to move out here. But two healthy children were plenty. Now they wanted to return home.

However, JupeCo insisted on a minimum of three years' service, and the bonus he would lose by quitting before the term was over amounted to half his total pay. He couldn't afford it. No contract that harsh would have been allowable in North America. But once they concluded their war of independence, the asterites had gone their own way. The asterites were as raw and stark as their own flying mountains.

The scoopship thrummed around him. Through the low, thick inertrans canopy he looked forward along the flaring nose. By twisting his neck he could have looked aft to the tapered stern. The metal shimmered blue in the light that poured from Jupiter. He could not see that open mouth which was the bow, gaping upon emptiness, but he could well visualize it. He had watched the service crew often enough, to make sure that their periodic inspections of every accessible part were thorough.

And by the Lord Harry, it was something to steal from Jupiter himself and come back to brag about it!

Eventually the planet filled his entire vision. But then it was no more a planet, hanging in heaven; it had become the world. It was not ahead but below. Cloudfields stretched limitless underneath him, layered, seething, golden-hued but streaked with the reds and browns, greens and blues of free radicals. To port he saw a continent-sized blot of darkness that was a storm, and shifted course. Deceleration tugged angrily at him, and the planet's own pull, nearly three times Earth's. His muscles fought back. The first thin keening of cloven air penetrated to him. The ship quivered.

He switched off the autopilot and plunged downward on manual. The noise grew until it was thunder, booming and banging, rattling his teeth in the jaws and his brain in the skull. Winds did not buffet this craft traveling at many times supersonic speed, but gigantic air pockets did, back and forth, up and down, till metal groaned. Darkness overwhelmed him as he passed through a cloud bank. He emerged below it, looked up and saw the masses towering kilometer upon kilometer overhead, mountainous, lightning leaping across blue-black cavern mouths and down the faces of roiling slaty cliffs, against a distant sky that was hell-red. Briefly an ammonia storm pelted him, the hull drummed with the blows of gigantic poisonous hailstones. Then he was past, still screaming downward.

Presently he was too deep for sunlight to touch his eyes. He flew through a darkness that howled. He ceased to be Tom Hashimoto, husband, father, North American citizen, registered Conservative, tennis player, beer drinker, cigarette smoker, detective-story fan, any human identity. He and the ship were one, robbing a world that hit back.

The instruments, lanterns in utter murk, told him he was at sufficient depth. He leveled off and snapped the intake gate switch. The atmosphere ceased to whistle through the open tube of the hull—for now the tube was closed at the rear. A shock of impact strained him against his harness. The ship bucked and snarled. He reduced the drive to let the atmosphere brake him.

That air was mostly hydrogen and helium, but rich in methane, ammonia, carbon dioxide, water vapor; less full of ethylene, benzene, formaldehyde, and a dozen other organics, but nonetheless offering them in abundance. This far down, none of them were frozen out. The greenhouse effect operated. Jupiter's surface was warm enough to have oceans like Earth's. No man had seen them. The weight of atmosphere would have crumpled any hull like tinfoil. Even at this altitude, Mary Girl sped through an air pressure several times that of sea-level Earth.

Rammed into her open bow by sheer speed, the gases poured through a narrower throat. The wind of their passage operated an ionizer and a magnetic separator. Most of the hydrogen and helium were channeled off into a release duct and thrown away aft. Some of the other gases were too, of course, but there was more where they came from. An enriched mixture flowed—hurtled—through rugged check valves into the after tanks.

The process did not take long. This was actually not the time of maximum hazard—though ships had been known to break up when the stress proved too much for some flaw in their metal. The dive downward from orbit had killed most of those who had perished, and the climb back was not always completed. Gales, lightning, hailstorms, supersonics, chemical corrosives, and less well understood traps could be sprung. If the pilot was simply knocked unconscious, or lost control for a couple of minutes, Jupiter ate him.

A needle crossed the Full mark. The intake gate opened again and the tank valves shut. Hashimoto swung the ship's nose toward the hidden sky and poured power into the field drive.

He was once more out in sunlight, a storm-yellow dusk that showed him nothing but a cloud wrack tattered by wind, when his engine began to fail.

Pumps throbbed, forcing the scoopship's cargo of Jovian gas into the balloon. The sphere did not expand much; a single load was a small fraction of its total capacity. D'Andilly continued working to balance forces and hold the entire system steady in orbit.

At the end, he directed the hose to uncouple and retract. Then he slipped smoothly toward his assigned blister on the mother ship. This far spaceward there was seldom need to operate hydro-magnetic screens against solar particle radiation, so approach and contact were simple. While he got out of his harness and suit, the final adjustments of angular momentum were made. The balloon waited quietly for the next arrival.

Who would not be d'Andilly. He had twenty hours off till he dove again.

Whistling he climbed through joined air locks into the Vesta Castle. Two maintenance men waited in the companionway to clean his gear. Afterward the ship would be inspected. That was no concern of d'Andilly's. He gave the tech monkeys a greeting less condescending than compassionate—imagine so dreary a job!—and sauntered to pilot's country; a short, stocky man, brown hair carefully waved and mustache carefully trimmed, blue eyes snapping in, a hook-nosed square face.

Ulrich von Raaben, tall, blond, and angular, was emerging from the showers as d'Andilly entered. "Whoof!" he exclaimed. "You smell like an uncleaned brewer's vat." He saw the condition of the undersuit that the Frenchman began to strip off, and paused. "Bad down there?"

"I hit an unobserved storm," d'Andilly said, as casually as he could manage.

Von Raaben stiffened. "We shall have a word with the weather staff about that."

"Oh, I will report the matter, of course. But they cannot be blamed. It must have risen from the depths faster than normal. Our meteorologists can only observe so far down."

"A cyclonic disturbance does not rise for no reason. Surrounding conditions ought to give a clue, at least to the probability of such a thing happening. If they tell us a given region looks calm, and it proves not to be, by heaven, they will have some explanations to make!"

He ducked under the shower and wallowed in an extravagance of hot water. That was one of numerous special privileges enjoyed by the scoopship pilots. Others included private cabins, an exclusive recreation room, seats at the officers' mess with wine if desired, high pay, and a dashing uniform that one was free to modify according to taste. In exchange they made a certain number of dives per Earth-year, into Jupiter.

One must be young and heedless to strike such a bargain. Sensible men, even among the asterites, preferred a better chance of reaching old age. No wonder that scoopship pilots off duty tended to act like ill-disciplined sophomores. Including me, no doubt.

Pearson's eyes dropped. He stared for a space at his artificial hand, inert on the table. Finally he said, "But I do know. I was a space pilot once myself. Not scoopships, no, but prospecting, which is pretty dangerous, too, in a rock cluster. Some good friends of mine died in the same collision that shelved me. I managed to get into an intact compartment, alone. But I'd soon have died too, if the survivors hadn't risked their necks to search the debris for casualties.

"But ... that was sound doctrine. The ship was a total loss. Nothing more was being hazarded except men, who'd die in any event if they couldn't pool their efforts to jury-rig sufficient shelter until help came. This case is different. You have to multiply values to be gained or lost by the probability of success or failure. Exposing three ships and three men to a very high chance of destruction, for the sake of one ship and one man whom there's only the smallest likelihood of saving ... no, that's much too bad economics.

"Economics?" d'Andilly exploded.

"That's what I said," Pearson answered. Steel underlay his tone. "The dollar cost of building and outfitting a ship, of training and equipping a man. It's the only basis we've got.

"Wisner, you're an asterite born, and von Raaben has been one for a number of years. But I guess I'll have to spell the facts out for you. Pilot d'Andilly. You're kept like a fighting cock, because that's the only way to attract men to your job. So you aren't aware, I suppose, how thin a margin we asterites live on. Can you imagine what it means to carve a living from airless rocks? Sure, they're rich in metal; atomic power is cheap and solar power is free; but what is there otherwise? Why raid Jupiter at such enormous effort, if we didn't have to have those gases to form the basis of chemical synthesis, of our whole chemical industry, which equals our survival?

"Okay. It's barely possible that three ships working together could grapple onto Hashimoto's and haul him into clear space. I don't believe they could, but I'll grant a slight possibility. So if you did pull off that stunt, every boy on every asteroid would cheer himself hoarse for you, and every girl would fall into your arms, and every man would curse you for a pack of dangerous idiots. Because any operation which consistently gambled at those odds would soon go broke—and we've got to have the operation or the whole Republic dies.

"Now do you understand?"

From WHAT'LL YOU GIVE? by Poul Anderson (1963) Collected in Tales of the Flying Mountains

ed note: The Traveller RPG uses wilderness refueling from gas giants extensively. Rob Garitta point out the many reasons why this seemingly simple operation is actually fraught with peril.

A "system defense boat" (SDB) is a combat spacecraft with no FTL drive. Which means the mass a combat starship uses for the FTL drive is in the SDB devoted to more weapons and defenses. Kilogram for kilogram a SDB outguns a combat starship of the same mass.

Traveller FTL has the "jump limit": you must move away from the planet a distance of 100 planetary diameters before using FTL or Something Awful happens to the starship.

Wilderness Refueling, Local gas giant

A. Achieve orbit

This may not be as simple as it sounds. You must be prepared to deal with:

  • Debris from rings
  • (Electromagnetic) radiation
  • Particle radiation

The orbit will be near the cloud tops. A trip out to the jump limit is 5 to 10 million klicks and will take several hours for a ship that makes 3 gees. This is of concern to Navy operations and anyone else afraid of an attack deep in a (gravity) well (it will be several hours before) they can fall back (outside the jump limit and) call on the Jump Fairy to get them out of a tight spot. You could have part of your squadron at the jump limit and let only the ships needing refueling enter a close orbit and retreat to the jump limit when done.

Of course any (enemy) System Defense Boats (SDBs) waiting in the gas giant are waiting for you to split your forces.

(Defender) SDBs have it relatively easy. They aren't in a hurry to be somewhere else. They can loiter in relatively calm regions of the gas giant's atmosphere. They can pump in hydrogen as they need it for their power plants. Traders and interested others are trying to get fueled and get out fast and are bound to make mistakes.

B. Refuel

Great you made it this far! Be prepared to deal with:

  • Downdrafts
  • Life forms: gas giants do not usually produce intelligent life. Traveller canon does mention one race. Be careful you don't suck someone important into your fuel tanks. Beware the referee who reads H.P. Lovecraft.
  • Contaminated fuel: the good thing about contaminants in fuel is that you can usually smell them. That ammonia leak might cause concern but it also indicates your fuel tank has a leak.
  • Lightning strikes: lightning strikes are the natural enemies of starships.
  • Diamond storms: theory holds that Jupiter and other gas giants have carbon cores that under incredible pressure become diamond. Convection might throw diamond bits into the upper atmosphere. The bad news — this can damage or wreck your ship. The good news — the diamonds are probably poor quality so you don't need to worry about destabilizing the gem market.
  • Communications going out: they will at some point.
  • Sensor blindspot: probably near where the comms go offline.
  • SDBs: yet again.
  • Pirates: sauce for the goose, my friends.

I have no idea what kind of target numbers you need to roll to avoid damage or maintain control. I'd set them at 10+ and make the damage of concern but not immediately fatal.

Keep in mind many people skimp on armament for their fuel tenders. In this case a 600 ton SDB might immobilize a 100,000 ton dreadnought by taking out its fuel tenders to deny it fuel.

C. Set course to major world or outsystem

Yes. Please.

Note that this sort of piloting can be stressful and tiring to pilots. A 24/7 fueling operation might see pilots being rotated between the tenders and the fleet or they might be willing to let their tenders make mistakes while docking our handling cryogenic and inflammable materials.

Some gas giants will have orbiting weather satellites to help ships chart safe courses to refuel. Usually these are not found at C starports who want to sell you their rotten contaminated fuel. If the system has an A or B starport, a Navy or Scout base they have satellites orbiting the nearer gas giant.

Weather satellites could also keep a record of ships refueling or be part of a defense system (mines).

Element Bottlenecks

If you are thinking about a long term civilization on a planet or asteroid, an important chemical is phosphorus. Isaac Asimov called it "life's bottleneck."

Asimov noted that some chemical elements are more common in the bodies of Terran living creatures than in the rocks and dirt composing Terra. Compared to the rocks, those elements are concentrated in living things. The higher the concentration factor, the more vital that element is to organisms and the more rare the element is in rocks. By far the element with the highest concentration factor is phosphorus.

What this boils down to is that a planet's supply of living things (the total biomass) is limited to its supply of phosphorus. It is the first thing that will run out. If there is not enough native phosphorus it will have to be imported. True there are other vital elements, but the phosphorus limit is the one you will hit first.

This is a critical factor in the growth of extraterrestrial colonies, whether planetary or space habitats. It is also a factor in spacecraft closed ecological life support systems.

Please understand the implications for extraterrestrial colonies. If there is no importation of phosphorus, no baby can be born until somebody dies. The population size of the colony cannot grow without an influx of phosphorus. Even with zero population growth, they might need draconian measures, such as euthanasia for citizens reaching a certain age. Not to mention the Baby Police always on the lookout for illegal births.

Another implication is that upon a person's death, the phosphorus and nitrogen in their body cannot be wasted. There will probably be mandatory cremation, with the valuable phosphorus and nitrogen carefully extracted from the ashes. Or the bodies must be composted. Or if the dear departed's next of kin have a farm, the cremated ashes are allowed to be sprinkled over the family crops. One way or another the phosphorus and nitrogen must be recycled.

This is reminiscent of that quote from Frank Herbert's Dune: "A man's flesh is his own; the water belongs to the tribe." On the arid desert planet Arrakis, the bodies of the dear departed have all the water extracted before burial.

If things got really tight, I suppose that phosphorus could be synthesized by nuclear transmutation, but that would be insanely expensive.

Nitrogen for fertilizer is another critical element with no rich off-Terra source.

There is a bit of phosphorus in C-type asteroids. Nitrogen is in ammonia, which can be found in the atmosphere of gas giant planets (which are quite a long ways away) and as free nitrogen in the atmosphere of Titan.

A gentleman who goes by the handle Coffeecat suggested that nitrogen might become the basis of the solar system economy. Actually his exact words were "Ohmygod, we'll be on the feces standard."

The element bottleneck could be a large club that the government of Terra waves at the extraterrestrial colonies, if they start making noises about rebelling from Terra's oppressive control. If the Martian colonials start complaining about "no taxation without representation", Terra will respond with "You are receiving a nice steady supply of phosphorus. It would be a shame if anything happened to it." Naturally the Martian Revolutionary War might be kicked off by the unexpected discovery of of a large non-Terran source of phosphorus.

Naturally Mars Colony would be covertly trying to mine C-type asteroids in an effort to find an alternate source of phosphorus. Which a panicky Terran government would be doing everything in their power to suppress. Things get quite dramatic and explosive when you realize that the Martian moon Deimos is probably a large C-type asteroid.

The phosphorus situation is not very rosy on Terra either. It was noted in 2011 that the world-wide demand for phosphorus (mostly for agriculture) was rising about twice as fast as the growth of the human population. Some researchers say that Terra will reach Peak Phosphorus around 2030, and global reserves may be depleted in 50 to 100 years (starting from 2009). The main ways that phosphorus become uneconomic to recycle is by agricultural runoff and from manure (human and animal) flushed into the ocean. Subsistence agricultural practices would carefully conserve phosphorus by collecting manure and spreading it on the crops. But this is not a profitable option for factory farming so they just flush away the manure.

In the future there might be mandatory agricultural practices to minimize runoff, and sewage treatment plants designed to harvest phosphorus.


[L]ife can multiply until all the phosphorus is gone, and then there is an inexorable halt which nothing can prevent,” he wrote. “We may be able to substitute nuclear power for coal, and plastics for wood, and yeast for meat, and friendliness for isolation—but for phosphorus there is neither substitute nor replacement.

From LIFE'S BOTTLENECK by Isaac Asimov (1959)

Sevoris Doe:

     So, we recently came about reviewing Phosphor Supplies in Space over on the ToughSF Discord, and the math looks interesting.
     It has been proposed that space colonies may run out of phosphorus for farming and thus population support. That… doesn't really work out on detailed observation, though the economics also don't look utterly rosy either.
     Basically, Phosphor is present at about 1 gram/kg of terrestrial crust. For planets and planetoid rubble that can be used as an average assumption. Mind, that is not a lot — phosphorus minerals have much higher concentrations of the stuff — but ultimately it is very workable. Here's why.
     An adult person needs about 700mg of Phosphor per day. At 1g/kg of phosphor concentration, supplying enough phosphor for 250,000 people requires you to grind down and chemically process all of 176.1 tones of rock. That's for a day so let's escalate that number. For three months worth of buffer in a closed-loop life support system we'll need to processs 15,849 tones of rock.
     But that is still not a lot. And I would argue that you will process many more times in rock, metaloid silicates etc. trying to get why you are in space, which is to say: thousands of tones of rare metals, millions of tones of metallic and silicate construction materials and equal amounts of volatiles, and it is attractive to lump these together. Washing out phosphorus also washes out other elements you want to get rid off, so it's basically a processing byproduct.
     In my conclusion, a space colony will not run out of phosphorus any time soon. They'll need closed-loop life support — but that is basic operation procedure for a space colony. Depending on how autonomous and self-replicating your mining operation is, you might get to the point where you're throwing away the sulphuric acid… though this doesn't pay after a point; acids used for ore processing is expensive once you go about using it in large amounts, you'll want to reclaim it.
     Mass-wise, every other bit of population-support infrastructure will be more expensive. You'll be processing more rock for silicate fiber structure materials and radiation shielding for the new habitats; and asteroid rock for metals to make the life support and hydroponics for new people, than in phosphorus. At least if you have a healthy asteroid diet.

G dVille

     Overall, phosphorus is potentially a limiting element for life in the universe. Probably between that and nitrogen. Certainly not water, the staple of many a scifi plot (last century, anyway). For the near term at least, local constraints will govern the expansion of Earth life. Mars has 5 times the available phosphates of Earth, but has a deficit of nitrogen. Meanwhile, Luna seems to be short of carbon.
     My pet project of the last few years is developing a room temperature 3D printable low-temp-cured cement based on phosphate chemistry, as a basis for creating habs on Mars. So even beyond biology, phosphorus may be in demand.
     Also for the world development of a story, I've been looking into chemotrophic ecology. Phosphates play a pretty critical role there in the cellular biochemistry.
     Chemotrophic ecology is probably going to be a cornerstone of ecology construction for any human hab- there has to be a way to replicate the Great Oxegenation Event. Photosynthesis may not be feasible. Inorganic electrolysis probably requires an inorganic power source. Maybe this is the most feasible way to initiate non-photosynthetic oxygenation, but I'm still looking into a bioregenerative method for my story that is not reliant on human maintenance of machinery.


A gentleman named Mr. MJW Nicholas wrote me with a brilliant suggestion. He points out that Terra itself is heading for a phosphorus shortage, "Peak Phosphorus". In that case, instead of Terra having a strangle hold on the space colonies, it might be the other way around. By the same token it would become MacGuffinite.

I was interested to read in the 'Rocketpunk and MacGuffinite' topic the subject of peak oil, and how humanity could make use of Titan. I did a little bit of digging and it struck me how, even if we do come up with viable and sustainable alternatives for both transport and energy production, there are no such alternatives for the vast quantity of other petroleum products our modern society is utterly dependent on.

It was suggested on a number of websites that alternatives for pharmaceuticals would be the holistic or home remedy type eg. willow bark instead of aspirin, and I came to the conclusion that even if you could find natural alternatives, you'd need huge amounts of land to grow them in the quantities required, land which would also need to be used to support cotton and hemp growth to meet the demand for natural fibres for clothing, given that many modern clothes contain oil-based synthetic fibres. Other types of natural fibres come from animals, but then they need grazing land, which means even more land is used. Regardless of the land usage, there is always one thing land will need to be used for — food crops. There is only a finite amount of arable land available, and many breeds of plant can only be grown in certain locations, based on a wide range of environmental variables, which further limits crop yields without either long-term efforts into selectively breeding, or direct manipulation of genes for desired traits. The first one can take potentially hundreds of generations to achieve, depending on the desired result, and the latter requires laboratories, who use equipment that would be difficult and costly to produce, repair or replace in a post-peak oil world, even if one takes into account the usage of oil-sands.

Even if we tapped into difficult to access reserves on a larger scale than we already do, such as deep-sea wells and oil-sands, and even if the ban on exploiting Antarctica's potentially vast mineral wealth was lifted, this is still not a viable long-term solution. Obviously, getting to Titan and extracting, and refining the mineral wealth there in sufficient quantities, and shipping it back, would be immensely costly. I know full well that you know the amount of work and effort behind setting up propellant depots and in-orbit refineries and all the other stuff needed to set that kind of infrastructure in motion, let alone maintain it. This kind of future is one, however, that allows for colonization. But it got me thinking — what are other things that humans, and modern civilisation with it's global scale infrastructure would need, and we have a finite amount of?

Then I harked back to another part of your website, where you mention phosphorus.

Much like peak oil, it is predicted, optimistically, that we'll hit Peak Phosphorus within the next 80-100 years, pessimistic estimates suggest by 2030. Having done some more digging, I noticed that whilst some claim that recycling phosphorus from sewage, and having better crop management and limiting run-off, etc. could outright halt peak phosphorus, a larger number of articles suggested that even with these measures, we're only delaying it. Even if we stop it altogether, we're now limited on how much of anything we can grow, which limits crop yields, which, as you can see, would have a negative impact on the proposed 'plant-based' alternatives for petroleum-based products.

Which leads me onto this — recent in-situ analyses of Martian soil suggest that water soluble phosphorus exists in higher concentrations than anywhere on Earth, with rich deposits near the surface, as well as deeper underground. Also, recent spectroscopic analyses of several near-Earth objects have suggested higher concentrations of phosphorus in C-type asteroids than previously believed.

Both of these things are much easier to get to than Titan, comparatively speaking. Also, given the greater urgency to find alternative phosphorus sources, you could probably convince more people to financially back martian or NEO colonization or exploitation efforts. This would also make it easier to suggest to people 'hey guys, oil's getting a bit pricey, how about Titan?' because you've already got the infrastructure in place between here and Mars.

From MJW Nicholas (2016)

Phosphorus plays a central role for life on Earth. It is an intimate part of life's architecture, contained in the salts that stiffen vertebrate bones and in phospholipids that form the walls of all living cells. It is linked to life's fundamental fuel, adenosine triphosphate (ATP), the energy storehouse that powers just about every physiological action. Even the lengthy genetic sequences of DNA and RNA — the blueprints for life itself — lie cradled within the twisting embrace of a pair of helical backbones built from phosphorus.

Yet for all its biological importance, the element is in remarkably short supply on Earth. According to recent studies, hydrogen atoms outnumber phosphorus atoms by 49 million to 1 in Earth's oceans, 2.8 million to 1 in the universe at large, and 203 to 1 in bacteria. Phosphorus fares a little better with oxygen atoms, which outnumber it by 25 million to 1 in the oceans, 1,400 to 1 in the cosmos, and 72 to 1 in bacteria. For every atom of phosphorus counted in such a census, carbon and nitrogen atoms appear, respectively, 974 and 633 times more often in the oceans, 680 and 230 times more frequently in the universe, and in numbers 116 and 15 times greater in bacteria.

Even these statistics belie the true importance of phosphorus, which scientists credit as the limiting factor for terrestrial life. This idea follows Justus von Liebig's law of the minimum, an early agricultural concept stating that a species responds only to the nutrient in shortest supply and that this is what limits the growth of a given population. Science popularizer Isaac Asimov, in his 1974 book Asimov on Chemistry, put it most succinctly: "Life can multiply until all the phosphorus has gone and then there is an inexorable halt which nothing can prevent."

So where did Earth's phosphorus come from?

"Because phosphorus is much rarer in the environment than in life, understanding the behavior of phosphorus on the early Earth gives clues to life's orgin," said Matthew Pasek, a doctoral candidate at the University of Arizona's Lunar and Planetary Laboratory. Working with Dante Lauretta, assistant professor of planetary sciences at the university, Pasek argues that iron meteorites could have brought more phosphorus to Earth than occurs naturally. He presented his ideas at the 228th American Chemical Society national meeting in Philadelphia on Tuesday.

The most common terrestrial form of phosphorus is a mineral called apatite. When mixed with water, apatite releases only very small amounts of phosphate, the oxidized form in which phosphorus naturally is found. Scientists have tried heating apatite to high temperatures, combining it with various strange, super-energetic compounds.

"These experiments tended to use chemicals that were probably uncommon on the early Earth, so it's unclear how applicable they are to geochemical systems," Pasek told Astronomy. "It's more intuitive to use simpler and more common compounds, such as those found in meteorites."

Lauretta conducted experiments showing that metal surfaces corroded in the early solar system in a way that concentrated phosphorus on them. "This natural mechanism of phosphorus concentration in the presence of … iron-based metal … made me think that … corrosion of meteoritic minerals could lead to the formation of important phosphorus-bearing biomolecules," he explained.

Inspired by these experiments, Pasek and Lauretta began looking at meteorites as a possible source of the element. Meteorites contain several different phosphorus-bearing minerals, but the most important, said Pasek, is iron-nickel phosphide, also known as schreibersite. This metallic compound is extremely rare on Earth, but iron meteorites are peppered with schreibersite grains or even pinkish-colored veins of the mineral. Iron meteorites became the focus of the study because schreibersite is between 10 and 100 times more common in iron meteorites than other types.

Last April, Pasek, Lauretta, and undergraduate student Virginia Smith, mixed schriebersite with de-ionized water at room temperature. They then analyzed the liquid mixture using nuclear magnetic resonance. "We saw a whole slew of different phosphorus compounds being formed," Pasek said. "One of the most interesting ones we found was P2O7, one of the more biochemically useful forms of phosphate, similar to what's found in ATP." The analysis revealed numerous phosphate salts in different states of oxidation, Pasek told Astronomy.

Previous experiments have formed P2O7, or pyrophosphate, but at high temperature or under other extreme conditions. "This allows us to somewhat constrain where the origins of life may have occurred," Pasek said. "If you are going to have phosphate-based life, it likely would have had to occur near a freshwater region where a meteorite had recently fallen. We can go so far, maybe, as to say it was an iron meteorite."

Meteorites were critical for the evolution of life, argues Pasek, because of minerals like pyrophosphate, which is used in ATP, in photosynthesis, in forming new phosphate bonds with carbon-bearing compounds, and in a variety of other biochemical processes.

"I think one of the most exciting aspects of this discovery is the fact that iron meteorites form by the process of planetesimal differentiation," Lauretta noted. The building blocks of planets, called planestesimals, form both a metallic core and a silicate mantle. Iron meteorites come from the metallic core, and other types of meteorites, called achondrites, represent the rocky mantle. Today's asteroids are what remains of our solar system's population of planetesimals.

Life's limiting element links the origin of life to a specific time and place in the solar system's history. "No one ever realized that such a critical stage in planetary evolution could be coupled to the origin of life," Lauretta said. This connection also suggests the environment needed for life elsewhere. The first ingredient is an asteroid belt, where planetesimals can grow to about 300 miles (500 kilometers) across, large enough to form metal cores and stony mantles.

The second requirement, say Pasek and Lauretta, is a mechanism to break up these bodies and deliver them to the inner solar system. Today, Jupiter's gravity perturbs asteroids from stable orbits, herding them toward the inner solar system — and Earth — and also causing them to collide with one another, creating meteorites.

If this scenario is correct, Lauretta argues, then the reactive forms of phosphorus needed by biological molecules — and so essential to terrestrial life — were denied to planets and moons of the outer solar system, limiting the prospects for life there. Likewise, he said, life is less probable in solar systems without a Jupiter-size world able to perturb mineral-rich asteroids toward rocky planets closer to their suns.


(ed note: this is taking place in a Lunar city)

All human communities, wherever they may be in space, follow the same pattern. People were getting born, being cremated (with careful conservation of phosphorus and nitrates), rushing in and out of marriage, moving out of town, suing their neighbors, having parties, holding protest meetings, getting involved in astonishing accidents, writing Letters to the Editor, changing jobs—Yes, it was just like Earth. That was a somewhat depressing thought. Why had Man ever bothered to leave his own world if all his travels and experiences had made so little difference to his fundamental nature? He might just as well have stayed at home, instead of exporting himself and his foibles, at great expense, to another world.

From EARTHLIGHT by Sir Arthur C. Clarke (1955)

(ed note: Some space colonies might get a little strict about tourists who eat more phosphorus than they excrete. )

After a while the style settles down a bit and it begins to tell you things you really need to know, like the fact that the fabulously beautiful planet Bethselamin is now so worried about the cumulative erosion by ten billion visiting tourists a year that any net imbalance between the amount you eat and the amount you excrete whilst on the planet is surgically removed from your bodyweight when you leave: so every time you go to the lavatory it is vitally important to get a receipt.

(ed note: and such space colonies might take a dim view of people born in the colony who want to emigrate, taking their store of phosphorus with them.)

From THE HITCH HIKER'S GUIDE TO THE GALAXY by Douglas Adams (1979)

     Space travel may be more common in the 22nd Century, but while it is cheaper and more efficient, that doesn't make it easy to move. While Mars has its temptations for certain types of Terran malcontents, to settle there takes quite the commitment—and quite a bit of chnops.
     Originally, it was literally CHNOPS—carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur, the six most common elements in life. Mars had much of those, already, but on a lifeless planet you need as much CHNOPS, preferably as aqueous solutions, as you can get.
     The original standard set by the Planetary Trust was based on a candidate's mass at age 21, or if not known, the average mass based on body type. You were expected, in essence, to bring five times your mass in CHNOPS. There were asteroid mining firms who would be happy to assist you for a fee. If not, they could hire you to mine the stuff for five years, and pay your CHNOPS to Mars for you.
     Unless, of course, you had those sorts of unfortunate personal issues that might leave you unable to meet your quota or pay off the expenses you incurred while under their employ. They can extend the contract another five, or twenty, years if need be.
     (The average Martian, incidentally, is horrified by the exploitive nature of the system, but also struggles to figure out what to do about it. The most common proposal, to allow provisional resident status and have them help mine Mars, isn't guaranteed to be an improvement.)
     Eventually chnops became a matter of accounting, and thus a semi-official Martian currency. The Planetary Trust became a treasury, for both cash and biomass—the latter including a thorough census of every Martian, immigrant or native, and an accounting for their remains after death.
     Your covenant to the Trust isn't just for the CHNOPS you brought outside your body, after all—you're committing for your remains to be used to grow some sort of plant. Dr. Jeferson Schefer, for example, was buried under a sapling of Elysium hazel, a tradition his family has followed since. You can buy hazelnuts from them, of course.
     In the mid-22nd Century, the Trust began to shift the requirements away from pure CHNOPS, in favor of other minerals—more platinum-family elements, for instance. That is generally attributed to tensions over rights to Deimos.
     Since the beginning of Martian exploration and colonization, Deimos was critical as a fuel depot and mining base. Its spaceport's legend, "DEIMOS FOR ALL," reminded everyone that it was a port co-managed by Earth and Mars. Even leading up to the War, Deimos was a place where humans of all worlds could mingle, do business, and consider options.
     This was usually the last stop before Mars-side, the point of no return for many an augment looking for a new beginning. If they can't handle the Martians on Deimos, they better hope for a quick refund in chnops—even if they paid in real CHNOPS—and that the Moon could put them to use.
     Also, Deimos is where you were screened to see if you were in fact augmented. If not, you were usually given the choice of accepting the augmentation as a matter of public health, or accepting a refund from the Trust.
     Hostels are a growth industry on Deimos--there are about 200 people at any time, either waiting for their augmentation therapy date, or waiting for a refund. Technically, there are more Terrans on Deimos than Martians, which is why co-management is required. The Terrans provide the public security and handles the transfer of citizenship and identification from Earth to Mars. Mars focuses on processing the new residents, arranging for basic income and identifying prospective communities based on personality and skills.
     And if you can manage the journey, the expense, the probable toil, and the inevitable bureaucracy, you can at last plant your feet on red soil and begin to make your new home.


     Over the weekend I got asked a question: How does Mars contribute to the interplanetary economy, given its economic foundation in CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur) seems to preclude exports in the normal sense?
     First, bear in mind that it's not just that, per the Martian Charter, CHNOPS is to be conserved and cannot be exported from Mars.
     As mentioned previously, the tyranny of the rocket equation still holds a firm grip in the 22nd Century. With Mars' shallower gravity well, it's slightly easier to launch ships into space — and its currently thin atmosphere makes it much easier as well. But the logarithmic relationship between dry mass and wet mass still means that you need exponentially larger ships to launch larger payloads.
     Plus, even in the 22nd Century, your choice of propellants are still, technically, CHNOPS. Whether you use cryogenic hydrogen/oxygen fuel, dinitrogen tetroxide with hydrazine, or methane with cryogenic oxygen, you're using elements that Mars would generally prefer be reserved for biomass.
     So how does Mars get to space?
     Through loopholes, of course.
     Mars won't let you use their CHNOPS to create rocket fuel. But, Deimos is outside of the Martian Charter's jurisdiction. So typically ships will be built and fueled on Deimos, sent down to the Martian surface to be loaded, and then launched back to Deimos.
     The side benefit, from the long term view, is that all that Deimos fuel spent on Mars, winds up becoming part of Mars' total CHNOPS count, even if it isn't currently bound up in biomass. It's not like all that spent propellant is going anywhere quickly.*
* Long term, until the magnetosphere question is resolved, pretty much all gases in Mars' atmosphere will wind up being blasted off the planet by the solar wind. Short term, it's adding, albeit slowly, to the oxygen and water vapor in the atmosphere. Mars considers it a win.
     But that's all dancing around the question.
     The real answer is, Mars tends to provide intangibles — services like their asteroid detection network, or their expertise in coding and training fourth-generation deepers. There is a limited export in things Mars has in abundance, mostly iron. But even then, most of it winds up at Deimos, for spaceship construction. Mars isn't all that fond of plastics, either — that's a luxury of a world that originally thought fossil fuels would last forever. Where plastic must be used, it's kept in forms that can be recycled, even if by means of supercritical water oxidization.
     Until the sol comes when torchships are practical and Mars no longer needs to account for every mole of CHNOPS in the biosphere, Mars won't be creating consumer goods for non-Martian consumption. Mars considers the ecological disaster that Earth has become, a stern warning about what happens when you presume economic growth can be infinite. They aren't eager to repeat the mistake.


(ed note: And if a space colony is really hard up for phosphorus, they might institute an age limit. No child can be born until somebody dies. The longer you live, the longer before the colony can afford a new birth. The elderly will have to prove that they are worth the phosphorus they are tying up. Or face euthanasia when your reach the mandated maximum age.)

     'Look! Look there!' Grew's voice was a whispered rasp. 'You see the horizon? You see it shine?'
     'That is Earth — all Earth. Except here and there, where a few patches like this one exist.'
     'I don't understand.'
     'Earth's crust is radioactive. The soil glows, always glowed, will glow forever. Nothing can grow. No one can live — You really didn't know that? Why do you suppose we have the Sixty?'
     The paralytic subsided. He circled his chair about the table again. 'It's your move.' (ed note: they are playing chess)

     Schwartz said finally, 'What — what is the Sixty?'
     There was a sharp unfriendliness to Grew's voice. 'Why do you ask that? What are you after?'
     'Please,' humbly. He had little spirit left in him. 'I am a man with no harm in me. I don't know who I am or what happened to me. Maybe I'm an amnesia case.'
     'Very likely,' was the contemptuous reply. 'Are you escaping from the Sixty? Answer truthfully.'
     'But I tell you I don't know what the Sixty is!'
     Grew said slowly, 'The Sixty is your sixtieth year. Earth supports twenty million people, no more. To live, you must produce. If you cannot produce, you cannot live. Past Sixty — you cannot produce.'
     'And so …' Schwartz's mouth remained open.
     'You're put away. It doesn't hurt.'
     'You're killed?'
     'It's not murder,' stiffly. 'It must be that way. Other worlds won't take us, and we must make room for the children some way. The older generation must make room for the younger.'
     'Suppose you don't tell them you're sixty?'
     'Why shouldn't you? Life after sixty is no joke … And there's a Census every ten years to catch anyone who is foolish enough to try to live. Besides, they have your age on record.'
     'Not mine.' The words slipped out. Schwartz couldn't stop them. 'Besides, I'm only fifty — next birthday.'
     'It doesn't matter. They can check by your bone structure. Don't you know that? There's no way of masking it. They'll get me next time … Say, it's your move.'
     Schwartz disregarded the urging. 'You mean they'll —'
     'Sure, I'm only fifty-five, but look at my legs. I can't work, can I? There are three of us registered in our family, and our quota is adjusted on a basis of three workers. When I had the stroke I should have been reported, and then the quota would have been reduced. But I would have gotten a premature Sixty, and Arbin and Loa wouldn't do it. They're fools, because it has meant hard work for them — till you came along. And they'll get me next year, anyway … Your move.'
     'Is next year the Census?'
     That's right … Your move.'
     'Wait!' urgently. 'Is everyone put away after sixty? No exceptions at all?'
     'Not for you and me. The High Minister lives a full life, and members of the Society of Ancients; certain scientists or those performing some great service. Not many qualify. Maybe a dozen a year … It's your move!'

From PEBBLE IN THE SKY by Isaac Asimov (1950)

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