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.

Asteroids: The Better Resource

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)
Supersonic Dust Roaster

(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
SABATIER REACTION

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
ISRU Sabatier

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
SABATIER REACTION ECONOMY

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.

From AN ALTERNATE APPROACH TOWARDS ACHIEVING THE NEW VISION FOR SPACE EXPLORATION by Stephen Metschan (2006) {use link to "AIAA 2006 Paper"}

(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.

From On Colonization by Rick Robinson (2009)
Early Days - economics of private space services

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
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.

Lunar Ice

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 delivery to the Moon by asteroidal and cometary impacts

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)
2010: Odyssey Two

     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)
Water

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)

Asteroid Mining

There have been hundreds of science fiction stories about asteroid miners (rock rats, rockskippers, 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 they never stop trying).

Crashing the platinum market is not as much of a concern, since it is actually useful as a catalyst and for crucibles.


AsteroidDiameterMass
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 the 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.

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.

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).

From EXPLORATION STUDIES TECHNICAL REPORT FY 1988 STATUS, VOLUME II
EARLY ASTEROID MINING

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.

results:
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.

 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)
ASTEROID MINING

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.

Conclusions

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
TOP 10 REASONS WHY SOMETHING ARM-LIKE IS WORTH DOING

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 "grubstalkes". 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.


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

From NEWTON'S WAKE by Ken MacLeod (2005)
GRAY LENSMAN

(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)
THE SHATTERED STARS

     "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 Af/as-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)

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)
IN-SITU SOLAR ZONE REFINING

(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)
LASER ZONE REFINING

(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)
DESTROYING THE GOLD STANDARD

"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)

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.’

‘Eh?’

‘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 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. 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)

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.

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.

Asteroid Miners May Get Help from Metal-Munching Microbes

     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 Space.com.

     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

Urban biomining meets printable electronics

     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.

From Urban biomining meets printable electronics by Lynn Rothschild (2016)
Scientists create nano-reactor for the production of hydrogen biofuel

     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.

Truffle House

(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

Reef

(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)

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.

Early Lunar Mining

     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)

yield:
     - 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).

     Result:
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)
Flow Chart
Lunar Materials Production
LabelBuild
Upon
Additional Processes
(cumulative with "builds upon")
Additional Materials Produced
(cumulative with "builds upon")
1N/ASieve and/or grind regolithRegolith
21Molten Regolith Electrolysis“Mongrel Alloy”
Ceramic
Oxygen
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
From Industrial Production Processes for Materials on the Moon, Asteroids and Mars by Phil Metzger (2015)
A Baseline Lunar Mine

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.

Specifications
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
Fleet
mobile slusher1
auxiliary vehicle with
small multipurpose crane
1
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
Interorbital Exchange - part 4, mining metals

     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.

Martian Mining

Mars: CO2 microburst excavation

 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
trace
elements
♃ 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:

Gases
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
PlanetScoopship
Orbital ΔV
Tanker
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. 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.

JERRY POURNELLE AND MOTE IN GOD'S EYE

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)

In Traveller, invading starship fleets will often use gas giants in the target solar system to top off their fuel tanks. 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.


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.

Industrial Revolution

"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
What'll You Give?

"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
Twilight of the GM: Wilderness Refueling

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.

Life's Bottleneck

[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 ()
Peak Phosphorus

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)
Earthlight

(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)
The Hitch Hiker's Guide to the Galaxy

(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)
The Ogg-Nat War: How To Become A Martian

     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.

The Ogg-Nat War: CHNOPS Details

     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.

The Sixty

(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?'
     'Yes.'
     '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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