If you try to go on a trip in your automobile, you are not going to get very far if there are no gasoline stations to feed your auto. Or restaurants to feed you. Or auto repair shops. This is what is called infrastructure. In the same way, if you want a rocketpunk future, you are going to need some infrastructure in space or your spacecraft are not going to get very far either.

Having said that, creating these pieces of infrastructure will be very expensive. It will be difficult to fund them. And you can be sure that whoever manages to build them will have iron control over who is allowed to use said infrastructure. And how much will be charged as a fee to use it.

It is possible to use spacecraft without any of this infrastructure, but it will be much more difficult. The owners of the infrastructure will probably adjust the fees so it will be cheaper to use their services, but only barely.

And of course an entertaining series of future histories can be postulated using various initial conditions. Does one national government have a monopoly? Two or more governments? Does one privately owned corporation have a monopoly? Two or more corporations? Or a several governments and several corporations?


A starship is not an independent entity—no more than a jet plane is independent just because it can leave the ground.

Imagine for a moment, a fully loaded 747 jet airliner flying from Los Angeles to New York. That's several hundred thousand pounds of airplane and three hundred people. First of all, there's the technology to build that airplane. (Not just one factory in the city of Seattle—but aerospace contractors all over the United States supplying components for every part of the plane, from blades for its jet engines to light bulbs over the seats.) Then there's the technology to maintain it; the schools to train the mechanics, the teachers to teach the stewards; the simulators and mockups on which they'll learn; the equipment with which the plane will be serviced, the specialized trucks and tools and devices; and the men and the training to support all of these levels. There's more than the airplane alone. There are airports. Lots of them.

That means the equipment and technology to lay down a perfectly flat runway two miles long. There are ground controllers—that means radar and scopes and computers. And reservation desks and communications systems to service those desks. Luggage-handling systems, porters, allowances for taxis, parking lots, restaurants, rest rooms—and the people to clean, maintain, and work in them.

Then you have to be ready for emergencies—so there will be rescue planes and fire trucks and medical equipment on hand. And detectives to protect the passengers and Federal Marshals to look for hijackers with metal detectors and psychological profile charts.

An airplane burns fuel—a lot of it. A 747 gulps enough petroleum in a single flight to drive an automobile for a year. That requires refineries to crack that oil (men to build and operate those refineries) and trucks to deliver it, tanks to store it. Passengers need meals, that demands another whole service industry. And entertainment—and specialized insurance—and airsickness bags in the back of each seat.

None of these things just happen by chance; they are designed into the system as it grows. The 747 could not exist until most of the support technology has already developed. What did not exist had to be built. All of it was oriented to fit the needs of the passenger as our culture has determined them. The very existence of the 747 as the kind of plane it is, is a direct result of what our culture considers important to the traveler. Imagine an airplane with fourteen bathrooms!

That airplane is a piece of living America. (In fact, I'm told it's the state bird of Hawaii.) It is an active vital symbol of our national technology, but it is no more independent of that technology than is a bird independent of the air in which it flies. The air holds up the bird. Our technology holds up that airplane.

Now. Apply that to a starship.

Extrapolate the needs of the Enterprise. Her fuel requirements, her crew requirements, her maintenance and training needs, her supply needs, her communication and control structures, her relation to the culture that produced her—and why that culture produced her.

Think about it.

Do you think the Enterprise is really an independent entity?

It isn't. It never could be. Her independence is an illusion, just as the independence of the 747 is an illusion. Sooner or later that ship is going to have to return home to have her exhausted energies recharged. Or, if not home, then to a base with an equivalent technology.

From THE WORLD OF STAR TREK by by David Gerrold (1973)

From the invited address of Salter Wherry to the United Nations General Assembly, following establishment of Salter Station in a stable six-hour orbit around the Earth, and shortly before Wherry withdrew from contact with the general public:

Nature abhors a vacuum. If there is an open ecological niche, some organism will move to fill it. That's what evolution is all about. Twenty years ago there was a clear emerging crisis in mineral resource supply. Everybody knew that we were heading for shortages of at least twelve key metals. And almost everybody knew that we wouldn't find them in any easily accessible place on Earth. We would be mining fifteen miles down, or at the ocean bottom. I decided it was more logical to mine five thousand miles up. Some of the asteroids are ninety percent metals; what we needed to do was bring them into Earth orbit.

I approached the U.S. Government first with my proposal for asteroid capture and mining. I had full estimates of costs and probable return on investment, and I would have settled for a five percent contract fee.

I was told that it was too controversial, that I would run into questions of international ownership of mineral rights. Other countries would want to be included in the project.

Very well. I came here to the United Nations, and made full disclosure of all my ideas to this group. But after four years of constant debate, and many thousands of hours of my time preparing and presenting additional data, not one line of useful response had been drafted to my proposal. You formed study committees, and committees to study those committees, and that was all you did. You talked.

Life is short. I happened to have one advantage denied to most people. From the 1950s through the 1990s, my father invested his money in computer stocks. I was already very wealthy, and I was frustrated enough to risk it all. You are beginning to see some of the results, in the shape of PSS-One—what the Press seems to prefer to call Salter Station. It will serve as the home for two hundred people, with ease.

But this is no more than a beginning. Although Nature may abhor a vacuum, modern technology loves one; that, and the microgravity environment. I intend to use them to the full. I will construct a succession of large, permanently occupied space stations using asteroidal materials. If any nation here today desires to rent space or facilities from me, or buy my products manufactured in space, I will be happy to consider this—at commercial rates. I also invite people from all nations on Earth to join me in those facilities. We are ready to take all the steps necessary for the human race to begin its exploration of our Universe.

It was past midnight by the time that Jan de Vries had read the full statement twice, then skipped again to the comment with which Salter Wherry had concluded his address. They were words that had become permanently linked to his name, and they had earned him the impotent enmity of every nation on earth: "The conquest of space is too important an enterprise to be entrusted to governments."

From BETWEEN THE STROKES OF NIGHT by Charles Sheffield (1985)

Surface to Orbit Boost

For most missions, almost half of the delta-V budget is used up in the first 160 kilometers or so, the lift-off from Terra's surface into Low Earth Orbit. This is the reason behind Heinlein's "halfway to anywhere" comment. In dollar terms, the Russian Proton would cost about $5000 per kilogram boosted into LEO while the Space Shuttle would cost about $18,000 per kilogram. Actually if you factored in all the shuttle's design and maintenance costs, the real price was closer to $60,000 per kilogram. NASA was hoping that the shuttle would cost more like $1,400/kg (in 2011 dollars), though part of the over-run was due to the multi-year interruptions in launches following Shuttle failures.

Infrastructure that help reduce the cost include Lofstrom loops, laser launchers, Marshall Savage's Bifrost Bridge, and the famous Space Elevator.

See the section on Laser Launching below.

Orbital Propellant Depots

As the delta-V for a mission goes up, the amount of propellant required goes up exponentially (or looking at it another way: the amount of payload shrinks exponentially). Large amounts of propellant are expensive, but the higher the mass-ratio the higher the likelihood that the spacecraft will not be resuable. Propellant expense is bad enough, but that's nothing compared to having to build a new spacecraft for each mission. Increasing the mass ratio means things like making the walls of the propellant tanks thin like foil, and shaving down the support members so they are fragile like soda straws. With such flimsy construction it does not take much normal wear-and-tear to turn the spacecraft into junk.

Having a propellant depot at the mid-point of a round-trip mission cuts the required delta-V in half. Instead of the spacecraft having to lug enough propellant to go to Mars then return to Terra, it only carries enough for half the trip but re-fuels (re-propellants, or re-remasses) at the halfway point. And when you are dealing with exponential growth, cutting the delta-V in half cuts the propellant amount much more than half.

Indeed, Rick Robinson noticed that with access to an orbital propellant depot, most cis-Lunar and Mars missions are well within the delta-V capabilities of a sluggish chemical rocket engine. You do not have to use a nuclear thermal rocket. Hop David noticed this as well. Dr. Takuto Ishimatsu's ISRU optimization algorithm calculated that NASA's Mars Reference Mission was more optimal with no NTR but with ISRU ("optimal" defined as "requiring less mass boosted from Terra into LEO").

This is also an argument for orbital propellant depots in Low Earth Orbit. Remember that once the rocket has traveled from Terra's surface into LEO, you are "halfway to anywhere". This means for a one-way trip, LEO is the mid-point of the mission.

But the general consensus is that the best place for an orbital propellant depot in the Terra-Luna system is at Earth-Moon-Lagrange-1.

However Dr. Takuto Ishimatsu has a dissenting opinion. He makes a case for putting the propellant depot at EML2, for complicated reasons I cannot quite follow. Hop David also makes a case for EML2.

Now to make this work, in addition to the depots you will need sources of propellant and tankers and lighter to keep the depots filled up. Water and hydrogen propellant is available in such places as the lunar poles, asteroids, and perhaps the Martian moons Phobos and Deimos. Dr. Takuto Ishimatsu developed an algorithm to optimize placement and supply of ISRU orbital depots.

Examples of tankers include Kuck Mosquitos, Zuppero Water Ships, and Zuppero Lunar Water Trucks.


Part of my series on countering misconceptions in space journalism.

Humans like to reason by analogy. It’s a powerful problem solving technique because so much of our experience generalizes, while first-principles thinking is computationally costly. In space, however, thinking by analogy is almost always wrong, because our terrestrial experience shares so little with the realities of space travel.

One concrete example of this is our intuition around fuel. Humans need to eat to stay alive, and similarly we charge our devices and fuel our cars. All of them can perform their essential duties with a well-contained, discrete battery or fuel tank.

Rockets, on the other hand, are little BUT fuel tank, and it’s important to understand why. Going to orbit involves more than flying beyond the atmosphere, which while difficult is comparatively easy. Going to orbit involves going fast! Roughly 7.8 km/s, or 17,000 mph. These numbers are so huge it’s difficult to imagine how to go that fast.

Rockets work by throwing mass out the back, as fast as possible. A really good rocket engine can eject hypersonic exhaust gas at more than 10 times the speed of sound, which seems fast enough for anything. On the other hand, orbital velocity is more like 25 times the speed of sound. This means that a rocket entering orbit is throwing exhaust products behind it literally as fast as chemistry and physics allows, and yet that gas is still travelling forwards faster than its ejection speed.

The exhaust results from burning fuel, and the fuel that’s ejected has to also be accelerated to these great speeds. This is similar to the effect that fuel mass has on the efficiency of long haul jets, but much much worse. In a jet, the aircraft has to carry passengers, cargo, and the fuel it needs to land for the whole journey. In a rocket, the vehicle also has to carry the oxidizer and the speeds involved are much, much greater.

As a result, the final velocity of the rocket increases only logarithmically with the ratio of fuel mass to everything else, a brain-melting problem often called the “Tyranny of the rocket equation.”

Δv = v_e log(Mi/Mf),

where Δv is the change in velocity, v_e is the exhaust velocity, Mi is the initial mass, and Mf is the final mass. Astronaut Don Pettit has a nice summary of these issues.

In space travel, Δv is everything, and it determines how much fuel is needed to go from place to place, as summarized in this handy chart:

In addition to the absurd 9.3km/s necessary to reach Earth orbit, most other destinations are a reasonable fraction of any achievable exhaust velocity. As a result, mission design is primarily about figuring out how big the fuel tank is and where to put it.

This horrible state of affairs means that it’s basically impossible to get to orbit, let alone deep space, using conventional engineering. In other words, all rocket scientists need to employ at least one crazy idea if they want to get there. The problem with crazy ideas is that it’s hard to tell which ones are almost practical.

As an example, many rocket scientists will reach for hydrogen and oxygen as a high performance fuel, even though hydrogen’s low density and hard cryo temperature mean that the mass fraction of the rocket takes significant penalties. The Space Shuttle is another example of where following wild ideas can lead. SpaceX instead employed lithium/aluminium alloys, materials that are extremely light and almost impossible to weld. There are no easy options – all options involve a great deal of difficulty, and many turn out to be impossible.

At the end of all this, a really good rocket is able to deliver about 4% of its launch mass to orbit. Everything else is structure, engines, and fuel. This is why rockets are really nothing like cars and bicycles and planes.

So it is that, faced with the impossibility of the problem, creative scientists and engineers will face temptation to veer off into wild hypotheticals. Many of the subjects of this blog series deal with the relative impracticality of some of these ideas.

The subject of this blog, after a this fairly sizable preamble, is refueling depots.

The idea behind refueling depots can begin with an analogy to gas stations. Most launch vehicles arrive in LEO with both cargo, such as a satellite, and an empty upper stage. If that stage could be refueled like a car, it would have enough Δv to go almost anywhere in the solar system.

Yes, you read that right. A close examination of the chart above shows that while getting from the surface of the Earth to LEO requires about 9.3km/s of Δv, LEO to the Moon, Mars, or Jupiter requires only about another 3-5km/s of Δv. Since the upper stage of most rockets delivers just over half of the orbital Δv, if refueled they would be able to send missions all over the place.

This fact has been appreciated for a very long time. Indeed, the science fiction author Robert Heinlein said it best when he said “If you can get your ship into orbit, you’re halfway to anywhere.”

Under the status quo, these perfectly good rocket stages are discarded, wasted, and either left to rot in orbit or burned up in Earth’s atmosphere. If a refueling capability existed, existing rockets could also launch larger payloads, or existing deep space payloads could be launched on smaller rockets.

As it happens, I believe that miniaturization and modularity are not sustainable ways to save money on large-scale space projects, a concept embodied in SpaceX’s outsized Starship vehicle. But it turns out that there are bigger weaknesses with the fuel depot concept.

The fundamental problem with refueling from a depot is that, in space, the cost of fuel is not determined by volume or weight, but by location. It’s not possible to economize on fuel by making a hybrid Prius rocket and driving it more slowly, at least not in any conventional sense. Fuel needs to be in the right tank at the right time in the right quantity, and never for very long before it’s used.

The obvious place for a fuel depot is in LEO. Fuel depots further out, such as near or on the moon, have much less benefit. Launch to LEO is the hardest leg, so it makes sense to refuel at each end.

In more detail, when we think of space we think of the night sky overhead, with satellites zooming around. What this disguises, and was ignored in the film Gravity, is that even a set of orbits as restricted as LEO is not one place. In practice, getting from one orbit to another can require more fuel than launching from Earth to that orbit in the first place.

Most orbital vehicles, such as Soyuz, Dragon, or the Shuttle, have 200-500m/s of Δv for orbital maneuvering. Typically, this fuel is used to correct imperfections of the launch, approach and dock with the space station, and then de-orbit.

As players of Kerbal Space Program will know, 500m/s is plenty of Δv to tweak the relative orbital phase, eccentricity, and semi-major axis. It is, however, vastly inadequate to change the inclination or the longitude of the ascending node, which are two other Keplerian orbital elements. Indeed, if we break up all LEO orbits into inaccessible adjacent slots accessible within a 500m/s window, there are about 200 distinct inclinations, and 200 distinct longitudes of ascending node, for about 40,000 discrete orbits.

If orbital refueling was standard practice for every launch, then we’d need to build (and keep supplied) on order 40,000 separate depots. This is obviously impractical, since the cost of building and operating even one is probably more expensive than continuing to manage without them.

In practice, we have to select just a handful of these orbits, just as the ISS needed a discrete orbit. Various considerations can be employed to select these orbits. For example, the ISS, which can be thought of as an orbital depot of people and fatigued aluminium rather than fuel, was placed in an orbit that was accessible for the launch sites and vehicles of the contributing countries.

An ISS-like orbit is a natural choice for a fuel depot, but it would only be useful for a subset of deep space launches. If the depot’s orbital plane doesn’t align with the destination during the relevant launch window, that’s just tough. For the moon, this would mean being able to launch only two or three days per month. For Mars, a dedicated depot would be required for each launch window. There are orbits whose orbital plane precesses in as little as two months, enabling alignment during any launch window, but for only a few days in that time. It is also possible to reduce fuel requirements by changing planes during an extended series of departure burns, but even this strategy requires around 1km/s of Δv.

Additionally, a high inclination orbit like the ISS is designed to be accessible for launches from Baikonur,. This increases the inefficiency of launches from any other launch site, which inflates the operational cost of keeping it fueled.

Some proponents believe that the depot could be topped up by salvaging the dregs of conventional launches. All rockets carry slightly more fuel than they need to to ensure margin for orbital insertion. What little is left over, if it happened to be in the same orbit, could be transferred to a depot for storage and later dispensing. Although such fuel would be “free” as salvage, it’s unclear how enough fuel could be salvaged from a huge variety of launch orbits to meet any kind of demand. If fuel margin on launch is 2%, then the depot would need at least 50 successful salvage operations in close succession to be able to refuel even one additional stage.

Operationally, depot management is complicated by a boom-bust cycle of use. For regular gas stations, usage is relatively steady and predictable, while the cost of unsold fuel lurking in an underground tank for a week or two is relatively negligible. Deep space launches occur infrequently and have differing quantities of use and even propellants. In a future where human flight to LEO or the Moon is ramping up, a depot would have to constantly grow to meet demand, which is a nontrivial requirement. Storing cryogenic fuels for long periods in space is difficult because they heat up and boil off, not least because the Earth is radiating significant heat into the LEO space region.

In practice, an impending deep space launch that required depot refueling would require the depot to be refueled “just in time” by a series of accessory launches, all of which would involve a partly-empty upper stage docking and transferring fuel, only to transfer that fuel back to the probe-carrying upper stage. Given the inefficiencies and losses of doing so, it is much easier to dock the fuel-carrying upper stage(s) with the payload, and perform the requisite injection burn directly. Same outcome, reduced complexity, greatly reduced overhead.

There is a broad exception to the above considerations; a case in which propellant transfer in LEO does make sense. In the SpaceX Starship concept, a fully reusable Starship is refilled by a series of launches while in LEO, before continuing its journey. This is a different model to an orbital fuel depot, though conceivably a Starship could be permanently parked in some orbit as a depot if there was a good enough reason. Orbital refilling is more like the in-flight refueling of a fighter jet than the establishment of a chain of gas stations.

The Starship concept reflects a different line of reasoning. Rather than compensate for a vehicle with a small Δv with a series of gas stations, build a vehicle with a huge Δv and, by refilling in LEO, enable it to fly enormous distances with no further support. Indeed, unlike conventional three stage Lunar lander schemes capable of transporting at most a couple of tonnes of cargo, the Starship is able to refuel in LEO, deliver hundreds of tonnes of cargo to the Moon, and fly all the way back to Earth in a single stage, reusable format. This is more like cargo flights to remote bases and islands that do not refuel after landing.

This graph shows the cargo capacity of Starship to deliver or return cargo from the Moon, depending on where it’s refilled and how low the dry mass ends up being. It can fly similar quantities of cargo to Mars, but must be refueled there by a local propellant factory.

In summary, reasoning by analogy in space almost never works. Be wary of glib assertions that future cis-Lunar industry will employ orbital fuel depots filled by Lunar water and staffed by self-replicating robots. The natural place to fuel rockets is at their launch pad!

From THERE ARE NO GAS STATIONS IN SPACE by Casey Handmer, PhD (2019)

     Introduction: On February 19th 2019 the world entered an era of impending Space-based military asset proliferation with U.S. Space Policy Directive-4 (SPD-4), which codifies legislative efforts in support of the establishment of the U.S. Space Force. There are currently approximately 81 U.S. military assets in Space, based on information that is publicly available. This study provides a preliminary quantitative assessment of potential U.S. military demand for in-Space water-based fuel in support of future U.S. military assets in Earth’s orbit. Our study concludes that if the U.S. military transitioned its future assets to utilization of water-based propulsion, there could be a military market demand for in-Space water-based fuel of 25 metric tons per year (baseline demand). In addition, and more importantly for the evolution of military demand for in-Space water fuel, we determined a parametric relation-ship between the supply of in-Space water on the Moon, Near-Earth Asteroids (NEAs) and the Asteroid Belt and the potentiality of increased U.S. military assets and increased propulsive capability per asset, thus leading to even further increased military demand for in-Space water in the future.

     Note: We make no assertions as to the merit of the establishment of a U.S. Space Force and the militarization of Space. However, increased market demand from civil, commercial and military use cases will all contribute to increased economic viability of Space Resources Utilization (SRU) and investability of associated technological capabilities and SRU value-chain public and private enterprises. The purpose of this preliminary assessment is to provoke holistic thinking on how U.S. military needs for strategic deterrence could drive significant demand for an in-Space water-based fuel supply-chain.

     Results and conclusions: Our estimate of U.S. military baseline demand for in-Space water, assuming today’s number of U.S. military assets in Earth’s orbit, is 25 metric tons, which using ULA’s $3,000/kg price point at LEO, deduces a total market opportunity of approximately $75M USD per year. This market opportunity is not significant and probably does not warrant in itself significant investment in the realization of in-Space water supply-chain for U.S. military needs. However, given the U.S. military’s desire to grow its presence in Earth’s orbit, and the proliferation of low-cost, highly maneuverable, and shorter lifetime military assets in LEO (with higher de-orbiting fuel needs), we foresee the $75M market opportunity growing by at least an order of magnitude in the foreseeable future. In addition, on the supply side, the estimated Lunar, NEA and asteroid belt deposits posit a new paradigm for how the U.S. military could deploy, operate, utilize, refuel, repair and retire or repurpose its assets in Earth’s orbit (and beyond). The U.S.’s notional apportionment of Lunar water deposits alone could, for example, enable the deployment of 33,000(!) equivalent assets (by mass) in Earth’s orbit, with 100X the maneuverability (i.e. station keeping reserves) for 500 years(!). Even though it is not reasonable to assume all of the U.S.’s theoretical Lunar water apportionment would be used for military needs, even a fraction of it would drive significant demand for in-Space water fuel, with a market opportunity in the $Bs/year.

     As noted in the introduction, we make no assertions as to the merit of the establishment of a U.S. Space Force and the militarization of Space. The sole purpose of this preliminary assessment is to provoke holistic thinking on how military needs for strategic deterrence could drive significant demand for an in-Space water-based fuel supply-chain, that enhances the value-chain of SRU for civil and commercial needs, and thus ena-bles increased investability of SRU technologies and enterprises at a global scale.

Water Supply and Demand


MoonNear Earth AsteroidsAsteroid Belt
ProsClosePotential low delta-VEnormous supply
Diverse resources & applicationsSignificant supplyDiverse resources
ConsRelatively high delta-VHighly variableHigh delta-V
Finite supplySignificant unknownsFar away


  • Demand estimates based on current U.S. military assets in orbit
  • Future trends for satellite development are unknown
  • Future assets may be smaller & decentralized, but advancements could dramatically change this

Calculating Demand

Demand Assumptions and Methodology


Deriving water needs:

  • All fuel is replaced with water (Isp~180)
  • Fueling occurs in LEO for deployment
  • Dry mass of satellites does not change
  • CubeSats not considered

Future assets:

  • Follow same orbital distribution
  • Lifetime of 20 years
  • 10X current maneuverability
  • 10% share of all ISRU water


USG Assets Results

Based on ~130 military assets, it was estimated:

  • Current demand is ~45 tons of water per year
  • 333 kg of water per asset per year

A future water propelled U.S. military asset would require:

  • 3,000 kg for deployment
  • 130 kg for disposal
  • 610 kg per year for station keeping

Supply chain demand:

  • ~40% Fuel for LEO
  • ~20% Fuel for MEO
  • ~40% Fuel for GEO

Transportation to destination orbit needs 50% for LH2/LOX and 10% for ion/plasma

Supply Chain Road Map

Calculating Supply 1: The Moon

Supply Chain Road Map

Lunar Assumptions and Methods


  • 1.2 x 1012 kg of water located at the Lunar Poles
  • U.S. Military has 10% share of total
  • About 2/3 of the dry mass of Lunar escape vehicles is payload
  • LH2/LOX fuel for Lunar escape
  • Ion/plasma propulsion used for final fuel delivery


  • 10% multiplier for 10% share of total water
  • ~50% multiplier for water loses due to Lunar escape
  • ~90% multiplier for water loses due to destination orbit insertion

Leaving 5.2 x 1010 kg for military assets

Lunar Results

  • Accessible with conventional technology
  • Relatively high magnitudes of water
  • Important stepping stone to future supply chains
  • Easier to disrupt
  • More Competition
Independent Lunar Supply Chain
Source Water Mass1.2 x 1012 kg
Delivered Water Mass5.2 x 1010 kg
Theoretical Number of Deployable Assets~3.4 Million Assets
Time Until Depletion~510 years

Calculating Supply 2: Near Earth Asteroids

Supply Chain Road Map

Near Term NEA Assumptions and Methods


  • Only 5-30m asteroids are minable
  • C types make up 20% of NEAs
  • Even distribution of asteroid size and type
  • U.S. Military has a 10% share
  • Solar baking method is scalable
  • Ratio of asteroid to spacecraft is 60
  • Min of 50% of water reserved for return
  • 75% of the water is mined out and the remainder of the asteroid is ditched
  • Fuel to despin asteroids is negligible
  • LH2/LOX is used for outbound
  • Derived LH2/LOX fuel for Earth return
  • Ion/plasma propulsion is used for fuel delivery


  • Use assumptions to find delta V max
  • Use delta V in broken plane delta V function to estimate mass in range
  • Adjust based on ratio in size range
  • 20% multiplier for C types
  • Density adjustment multiplier
  • 10% multiplier for percent water
  • 75% multiplier for water taken
  • 50% multiplier for water saved
  • Subtract water inbound for net
  • Adjust using Reiman sums to account for greater recovery at all lower delta Vs
  • 10% share of total water
  • ~90% multiplier for water loses

Leaving 5.3 x 107 kg for military assets

Near Term NEA Model

Near Term NEA Results

  • Comparatively low water mass
  • Extremely efficient for early ISRU cascade all within Lunar delta V
  • Water return ratio here is 5 times the investment
  • Provides value as a redundant supply chain
  • Hard to disrupt
Independent Near Term NEA Supply Chain
Source Water Mass1.6 x 109 kg
Delivered Water Mass5.3 x 107 kg
Theoretical Number of Deployable Assets~3400 Assets
Time Until Depletion~170 years

Long Term NEA Assumptions and Methods


  • All NEAs accessible with minimal in-bound loss
  • C types make up 40% of NEAs
  • Even distribution of asteroid size and type across delta-V ranges
  • All C type asteroids can be mined
  • 100% of the water is mined and the remainder of the asteroid is ditched
  • Fuel to despin asteroids is negligible
  • U.S. Military has 10% share of water
  • Derived LH2/LOX fuel for Earth return
  • Ion/plasma propulsion used for final fuel delivery


  • 20% multiplier for C types
  • Density adjustment multiplier
  • 10% multiplier for percent Water
  • 75% multiplier for water taken
  • ~16% multiplier for loses due to Earth return
  • 10% multiplier for military share
  • ~90% multiplier for water loses due to destination orbit insertion

Leaving 9.8 x 1012 kg for military assets

Long Term NEA Results

  • Tremendous resources available in the NEA population
  • Much of it is currently inaccessible
  • Requires significant R&D but it’s worthwhile
  • Hard to disrupt
Independent Long Term NEA Supply Chain
Source Water Mass6.7 x 1014 kg
Delivered Water Mass9.8 x 1012 kg
Theoretical Number of Deployable Assets1 Million Assets*
Time Until Depletion12,800 years*

*Capped at one million with demand becoming linear thereafter, as # of assets was far too great to be realistic

Calculating Supply 3: The Asteroid Belt

Supply Chain Road Map

Asteroid Belt Assumptions and Methods


  • Asteroid belt mass is 3x1021 kg
  • C type make up 40% of the population
  • C types are 15% water by mass
  • Asteroid intercept requires average delta-V of 8000 km/s
  • Fuel losses due to asteroid escape are negligible
  • Derived LH2/LOX fuel for Earth return
  • About 2/3 of the dry mass of miner is payload
  • U.S. Military has 10% share
  • Ion/plasma propulsion is used for final fuel delivery


  • 40% multiplier for percent C types
  • 15% multiplier for percent water
  • ~13% multiplier loses due to Earth return
  • ~90% multiplier for water loses due to destination orbit insertion
  • 10% multiplier for the 10% share of total water

Leaving 2.1 x 1018 kg for military assets

Asteroid Belt Results

  • Provides inexhaustible resources
  • Much of this water is centralized to Ceres
  • Could support planned Moon like manufacturing
  • Ceres will likely be an important strategic & economic hot spot for humanity
Independent Asteroid Belt Supply Chain
Source Water Mass1.8 x 1020 kg
Delivered Water Mass2.1 x 1018 kg
Theoretical Number of Deployable Assets1 Million Assets*
Time Until Depletion2.8 Billion Years**

*Capped at one million with demand becoming linear thereafter, as # of assets was far too great to be realistic

All Independent Supply Chain Outcomes

Given a 10% share of the total resources and estimated requirements for resource return, based on the average military asset with 10X maneuverability and 2% exponential growth, each supply chain could independently support:

Lunar Supply ChainNear Term NEA Supply ChainLong Term NEA Supply ChainAsteroid Belt Supply Chain
Source Water Mass1.2 x 1012 kg1.6 x 109 kg6.7 x 1014 kg1.8 x 1020 kg
Delivered Water Mass5.2 x 1010 kg5.3 x 107 kg9.8 x 1012 kg2.1 x 1018 kg
Theoretical Number of Deployable Assets3.4 Million3,4001 Million*1 Million*
Time until Depleition510 Years170 Years12,800 Years*Unlimited*

*Capped at one million w/linear demand after for asset replacement, as the exponential # of assets was unrealistic


Controversy and confusion continue to swirl around the issue of a cislunar space base, no matter where it is proposed to be built, what it is named, or what it is supposed to be for. Assuming that one of the primary purposes of such a base should be to supply lunar-derived propellant to vehicles in or departing from cislunar space, there are several immediate problems. First, there is a massive conflict in the potential schedule, since human missions to Mars that could be fueled from the Moon could take place about the time we find out if there is any actually accessible lunar ice available. We know that there are massive ice deposits on Mars, while most of the Moon is more than bone dry and the critical polar water deposit surface characteristics are still hidden from us.

Another problem area is the related but unknown costs of building the lunar mining base, the cislunar base, and the transport system to move the propellant from the lunar surface to the cislunar base, and how much that would add to the cost of lunar propellant. It is very hard to estimate the cost of developing the mining base. Some claim that the cost would be so high as to make the lunar propellant more expensive than propellant brought from the Earth, even though the cost of moving propellant from the Moon is usually quoted at about 15–20 times less that bringing it from the Earth’s surface.

Finally, there is the NASA plan, dormant for a while and now seemingly moving ahead, to create a way to use its obsolete and expendable SLS rocket to support what it still refers to as a lunar “gateway.” This is the project I have referred to in the past as the “Gateway without a Gate.” Very recently, the name and orientation of this project has changed again, to the Lunar Orbital Platform-Gateway, or LOP-G. It may seem as if a station in lunar orbit is more closely associated with actual lunar development, but placing a station in any actual lunar orbit, since it is then in an orbital plane, restricts the number of lunar surface locations that are easily accessible, and some of these so-called “lunar” orbits spend a lot of time far from the Moon.

Since most plans and sources do not mention refueling and logistics facilities as integral and initial parts of this project, such a “gateway” would neither be able to support a lunar base nor support dispensing lunar propellant produced by such a base, and are unlikely to be added later. A NASA request for information (RFI) in late 2017 covered many aspects of gateway science, but not a single transport issue. Most people would agree that an actual gateway provides a pathway to some physical location. So where is the physical path for this gateway? Where does it lead from and what does it lead to? In spite of the acronym, the planners have lopped off the critical gateway (transport-related) features—if they were ever there to begin with.

Some people fear that this project would eat up any and all funds for an actual lunar mining base and thus are now insisting that any lunar base be supported only from low Earth orbit, which is less efficient. If the platform is supported by the SLS, it would eat up even more funds, leaving little for any other human space projects, and could delay the establishment of an actual lunar base by a decade. With time, bureaucrats could decide that it is too dangerous to have propellant depots docked at the “gateway.” When the powers that be finally realize that crews stationed beyond LEO actually do need a significant amount of shielding mass to protect them from cosmic radiation, the whole project could be thrown into redesign disarray and last another decade before even being launched.

Obviously, a vehicle about to depart for Mars will not want to land on the Moon to get its propellant. Even getting into lunar orbit from a cislunar location would waste fuel. Thus, most experts believe that a location like Earth-Moon L1 or L2 is the best place to accumulate a large store of propellant, since it is always in the same position relative to the Moon and Earth, and thus is not subject to orbital plane limitations. Since vehicles ready for either departures to Mars or to cyclers going to Mars would need to be positioned at locations other than L1 (but at about the same distance from Earth), the main propellant depot would probably be at L1, with temporary depots positioned at other locations during Mars transit windows every 26 months.

So why is having a lunar-derived propellant supply in a near-lunar location so favorable? It’s the propellant cost, along with some other good reasons. If you want to go to any location outside the Earth-Moon system, whether it is Mars or an asteroid, a departure location high above Earth is best since that allows a very efficient Oberth maneuver, which uses a departure burn at L1 and another during a close pass of the Earth. This saves more than half of the departure propellant compared to departure from LEO, and for Mars missions, this means the Mars transit propellant weighs less than the mission’s dry mass. (If you are not using any lunar propellant, the advantage of the high departure point is much less.) From L1, lunar propellant can be delivered to LEO for only about 0.85 kilometers per second of velocity change, and even directly from the lunar surface for about 2.74 kilometers per second, making delivery much cheaper there than Earth propellant, which needs about 9.5 kilometers per second for delivery.

Having a base in a location like L1 makes initial support of a new lunar base much easier, since it is possible to reach L1 from anywhere on the Moon’s surface (or the reverse) in about 12 hours without worrying about the orbital planes. It also breaks the trip from LEO to the lunar surface into two smaller steps in terms of velocity change, thus decreasing the dry mass and fuel mass fraction of each vehicle, and allowing each one to carry relatively more cargo or propellant. This also improves the safety factor, since smaller rocket engines can be used, and they do not fire as long.

The big factor, however, is still the vast cost difference in moving the fuel to L1. The difference is primarily caused by the fact that you need a huge amount of propellant to move the Mars transit propellant from Earth, but only a small amount to move it from the Moon. Let us assume that we have vehicles ready for a Mars mission, either three large 85–100 ton dry mass vehicles, similar in size to the SpaceX BFS stage, able to carry a small crew plus a lot of cargo, or a set of ten smaller 30-ton-range dry mass vehicles, some for crew and cargo and some just for cargo. Assume that both fleets have about 4,000 tons of dry mass and need about 2,100 tons of propellant at L1 to depart via an Oberth maneuver. To show the huge numeric difference in cost between Earth-based and lunar based propellant at L1, we do need to do some simple calculations.

Note that in these calculations, I distinguish between the mass of the rocket propellant needed to move the Mars transit propellant to L1, and the mass of the Mars transit propellant (the payload) itself. To avoid confusion, I will refer to the transit propellant as the transit propellant payload, the surface to LEO propellant (a) carrying the transit payload to LEO, and the surface to LEO propellant (b) carrying up the LEO to L1 propellant needed in LEO to move the transit payload from LEO to L1. On the opposite side of the scale, I will refer to fuel for the cislunar tanker which carries the lunar-derived transit propellant payload as the lunar to L1 propellant. The multiple kinds of propellant uses may be confusing, but these distinctions are crucial to understanding the huge cost difference. All named transport propellant loads include the return to base propellant, as all vehicles are reusable.

Let’s assume you have moved your Mars expedition fleet dry mass (less the transit and bootstrapping propellant) to either a position at L1 or into a high orbit that is at a similar distance from Earth as L1 is, ready for its Oberth-style Mars departure maneuver. The transit propellant payload will need to include all of the propellant (a minimum of 400 tons) needed for bootstrapping the initial landings on Mars before the surface propellant plant there can be set up. During transit, this propellant can be kept in vehicles with cryo-coolers or in one or more propellant depots equipped with cryo-coolers. All in-space propellant discussed here is cryogenic liquid oxygen (LOX)-liquid hydrogen with an assumed specific impulse (Isp) of 460 seconds. All loads of the transit and bootstrap propellant to L1 are 150 tons, and thus a single expedition needs 14 such loads.

What is the amount of propellant mass to move the needed approximately 2,100 tons of transit propellant to the fleet at L1 or a similarly high orbit? Propellant created on Earth for use by this fleet would be moved to L1 in two steps, supported by multiple launches from the surface. If the BFR tanker version is used, 150 tons at a time can be delivered by one BFR tanker to a LEO logistics base. Reaching LEO takes about 9.5 kilometers per second of velocity change. There it is transferred to a small reusable tanker with sunshade and cryocoolers, which will take it from LEO to L1. This takes another 3.77 kilometers per second, for a total delta-V of about 13.27 kilometers per second. To provide propellant for the small tanker, almost two more BFR tanker loads of LEO to L1 propellant need to be delivered to the LEO base per 150-ton load of transit propellant payload. All of the BFR tankers would reenter and land back on Earth. The small tanker would offload the cryogenic propellant to shaded and refrigerated depots at the L1 base, and then, minus its payload, would drop back toward Earth, where it would use a single pass aero-capture maneuver to get into LEO again for a tiny amount of fuel.

For transport of Earth-based propellant, I will use current numbers for the SpaceX BFR (tanker version), as the launcher, which uses LOX-methane propellant. At 4,400 tons liftoff mass, we can subtract the dry mass to get the total propellant mass. The payload (wet or dry) is 150 tons, the upper stage is 85 tons, and the first stage is probably at about 125 tons, giving a total dry mass of 360 tons and thus a nominal surface to LEO propellant (a) mass of 4,040 tons, with almost 1,000 tons of propellant in the second stage. The propellant to payload ratio for this description of a BFR would be 4,040/150 or 26.93: 27 tons of propellant is needed for every ton delivered to an LEO base. The payload mass ratio is an impressive 0.0341. The structural mass ratio for the second stage is also an impressively low 6.9 percent (85 tons/1,225 tons). These numbers will probably change some as the extremely efficient BFR designs are refined further by SpaceX.

We will assume that, at LEO, the 150-ton transit propellant payload is then transferred to the smaller tanker of the same cargo capacity but with smaller engines which use only LOX-hydrogen. Note that the launches from the Earth’s surface need to supply the small cislunar tanker with both the LOX-hydrogen LEO to L1 propellant plus the LOX-Hydrogen transit propellant payload itself. The LEO to L1 tanker is already in orbit. Assuming that the smaller tanker is about 25 tons and has its own cryo-coolers and sunshade, its structure and payload would weigh 175 tons. The delta-V from LEO to L1 is 3.77 kilometers per second, and about 1.0 kilometers per second for the return trip where aerocapture and a small orbit trim is all that is needed. This means the small tanker needs to carry only 7 tons of descent propellant with it to L1, with a margin. This then means the mass that reaches L 1 must be 182 tons, so the ascent (LEO to L1) propellant mass, also with a margin, is 250 tons. The total mass departing LEO for L1 is now 432 tons. Note that the structural dry mass for this small tanker at departure from LEO is 5.8 percent.

However, the 257 tons of LEO to L1 propellant needed to move the single load of transit propellant payload propellant to L1 and get the empty tanker back to LEO also needs to be moved up to LEO first, and requires the use of 6,921 tons of LOX-methane surface to LEO propellant (b) on more than one ride to LEO via the BFR. It costs about $200,000 to launch a Falcon 9 with about 500 tons of fuel (LOX and RP1) on board, thus that fuel combination costs about $400 dollars per ton. LOX-methane might cost about the same. So, in order to get each 150-ton batch of Mars departure propellant to L1 from Earth, it takes the following components:

Propellant masses for delivery of 1 & 14 loads of 150 tons of LOX-hydrogen to L1

Payloadpayl massprop massvehiclefromtopropel. cost
Mars Transit prop (payload)1504,0401 BFR tankerEarthLEO$1,616,000
LEO to L1 tanker propellant2576,9212 BFR tankersEarthLEO$2,768,400
Mars transit prop (payload)1502571 cisln tankerLEOL1102,800
Total propellant mass-11,218bothEarthL1$4,487,200
(Multiply by 14 BFR and tanker loads to L1)
Total propellant mass to L12100157,052bothEarthL1$62,800,000

This is a 74.79-to-1 ratio of propellant to payload delivered to L1 (11,218/150). The transport propellant for one load of Earth propellant thus costs $4.49 million at $400 per ton so that just one ton of Earth propellant delivered to L1 would be worth about $30,000, based only on delivery propellant costs. The total propellant mass needed to deliver 2,100 tons, or 14 BFR loads, of transit propellant payload to L1 is 157,052 tons and costs $63 million, making the propellant cost a major part of a single Mars mission cost when conducted with reusable vehicles. If there were 100 civilian passengers on the trip, the fuel would cost each person $628,000.

Now let’s see how much lunar to L1 propellant is needed to get the transit propellant payload propellant from the Moon to L1. In this case, we are using a lunar to L1 tanker with LOX-hydrogen fuel. It takes 2.6 kilometers per second to go from the lunar surface to L1 and the same to return, but fuel use on return is minimal since there is no payload. I assume that this tanker is 30 tons, since it needs landing legs and it leaves the lunar surface with the same 150 tons of cargo, for a dry and payload mass of 180 tons. The empty 30-ton tanker will need just 25 tons of fuel (with a margin) to return to and land at its lunar base without its payload, so the structural mass, payload, and return fuel mass is 205 tons. The vehicle leaving the lunar base with its payload of fuel needs 170 tons of propellant, with a “wet” mass of 375 tons, so for the whole round trip (where the payload is left at L1), the fuel needed is just 195 tons of propellant.

Reusable Lunar surface to L1 & return tanker masses

Trip Component1 load massmass fractionmass for 14 loads
Dry structural mass0 tons0.08420
Transit propellant payload150 tons0.40210
return to base propellant25 tons0.07350
surface to L1 propellant170 tons0.452380
total mass at liftoff3751.00250
total round trip propellant195 tons0.522730

Notice that this means for a well-designed light tanker ferry, for every 1.0 tons of payload propellant it only takes 1.3 tons of fuel propellant to move the payload from the surface base to L1. At lunar takeoff, this tanker would mass 375 tons, but since it is taking off in lunar gravity, it would effectively weigh only about 62 tons. The composite propellant tanks, similar to what will be used for the BFR, would probably mass only 20 tons, leaving 2 tons for the engines, 2 tons for the landing legs, and 6 tons for the rest of the structure, including the cryo-coolers, sunshade and power system. This provides a structural mass fraction of 8.0 percent.

At this point, we do not know the actual cost of the lunar propellants as delivered to the tanker at the lunar base, including the vehicle development costs, but finally we can compare the relative mass of the delivery propellants. Assuming that we have not underestimated the tanker mass, the delivery propellant mass from Earth to LEO to L1 is 57.5 times more (74.8/1.3) than the delivery propellant mass from the Moon to L1 for the same 1 ton of propellant as payload. (Note that this mass difference is about three to four times larger than the typical cost difference of 15–20.) Cost of lunar fuel would include fuel production costs, transport propellant costs, and vehicle operation costs. The wear and tear on lunar-to-L1 vehicles is much less, since no vehicles need to take off from the Earth or re-enter the Earth’s atmosphere. Even the cislunar tanker must undergo an aerocapture to return to LEO from L1, while the lunar-to-L1 tanker would encounter only the stresses of thrust and landings. In addition, propellant at L1 is at least twice as valuable as propellant in LEO, due to the gravitational potential and additional velocity from an Oberth maneuver performed starting at L1.

So if the lunar propellant cost proportionally as much as the delivered Earth propellant before the lunar propellant is delivered to L1, it might cost about $23,012 per ton (57.5 times $400), or ($29,915/1.3) on the lunar surface. If future lunar entrepreneurs can beat that price, and if lunar water ice does exist in minable quantities, the lunar fuel production enterprise seems assured. Sales of large amounts of propellant for Mars expeditions would assure a robust human presence on the Moon. However, to assure that the logistics capability of any cislunar or L1 base will exist, the propellant depot and cargo handling capabilities must be a part of the design of the base from the beginning. Plans for the NASA cislunar base must accept that large propellant depots can be attached to it.

We are getting significant indications of international interest in a lunar base. At the same time, NASA says that there may not be enough room on the LOP-G station to accommodate international science participation. Why does the cislunar base have to be so small if there is support for it? The solution to this problem is a package deal agreement where there is a combined cislunar, lunar, and fully reusable transport development effort taking place simultaneously, with the international partners providing some of the transport and lunar surface infrastructure, with heavy reliance on commercial launches. Development would take place so that the first human landings at a lunar base site would take place within a year of the cislunar base completion. Without such a “package deal,” the NASA cislunar base would probably become the “gateway with no gate” or a “space station junior” copy with very limited utility, as many of us have feared.


Next up: in-space refueling. The first and most obvious customer is NASA; an orbital fuel depot would allow them to launch satellites on smaller LVs or launch larger satellites, allowing a choice between savings on the LV and increased capabilities on the spacecraft. That could mean buying an Atlas 401, Zenit, Soyuz, H-IIA or Falcon 9 instead of an Atlas 551, Ariane 5, H-IIB or Delta 4(5,4). Perhaps less obvious, Russia would see a significant benefit from a LEO depot in the plane of the Baikonur launch site. Vehicles would refuel in order to plane-change to an equatorial orbit for GEO deployment. Further into the future a fuel depot would be essential for the smooth operation of tugs and satellite tenders, serving as a buffer between fuel launches and fuel used in missions.

I think the current leader is Boeing with their in-development ACES vehicle using integrated fluids management. However, they are focused on LOX/LH2 propellant; few customers today have cryogenic upper stages. Hypergolic fuels require a different set of technologies and would most likely require shipping expendable supplies of a pressurant, either nitrogen or helium, but they have a larger potential market right now as hypergolics are typically used for satellite stationkeeping and orbit changes. The third fuel category is inert gases (argon, xenon) for ion engines; these can be stored as compressed gases or cryogenic liquids.

I think a near-term possibility is simply to ship water. It is dense, relatively inert and can be used as a life support consumable or as a propellant after electrolysis. It has a high surface tension and can be wicked out of a bulk tank in microgravity without pressurants or membranes. There are cubesat-scale thrusters available today that separate water over time, accumulating a charge of gaseous O2 and H2 using small amounts of power, then ignite that fuel in a high-efficiency engine. If future satellites were to adopt this technology for RCS and stationkeeping then they could nearly double their Isp while eliminating toxic fuels and cutting down to a single storage tank. Beyond the near-term possibilities, a water depot operator would be able to buy water from any LEO cargo provider as well as any asteroid mining company, relying on the proven launch capabilities today while safely and cheaply allowing for a riskier but cheaper future supply.


     This entry covers cis-lunar space. The topic of lunar mining and fuel supply has a rich field of information available and I cannot claim to know all of it, but hopefully this will show how we can begin to harvest most of our propellant instead of shipping it from Earth.

     First let's establish some basics:

     I assume that we will develop zero boiloff cryogenic storage, reliable cryogenic fluid transfer and reliable cryogenic engine restart. Vehicles will be designed to last 20-30 years, but generally are planned to be replaced every 10 years. Obsolete systems will keep operating until they fail, providing some bonus production capacity.

     The Moon's surface gravity is 1.62m/s², about 16.5% of Earth gravity.
     It takes about 1.87km/s of dV to land or take off from the equator. Only a little more is needed for the poles.
     Another 0.64km/s will take you from low Lunar orbit to EML1 (Earth-Moon Lagrange Point One).
     Low orbits around the Moon are not stable so you should not park anything important there.

     Large amounts of water ice are available at the south pole and most likely at the north pole as well.
     Plenty of metal oxides are available (including iron, aluminum and titanium), but carbon is rare.
     In some locations the mantle interface material (KREEP) is accessible at the surface; this rock is rich in incompatible elements like phosphorus, potassium, rare earths and radioactives.

      Low Earth orbit takes anywhere from 9.4 to 10 km/s of dV to reach.
     Each launch site has a specific, most-efficient inclination. Changing inclinations is very expensive.
     From any low-Earth orbit, EML1 is 3.77km/s away.
     From Kennedy Space Center LEO, geosynchronous orbit is 4.33km/s away. It's only 3.9km/s from an equatorial orbit.
     Earth escape is 3.22km/s away.
     EML1 is the balance point between Earth and the Moon, the place where the gravity of each body cancels out.
     From EML1, a craft with a heatshield can get to any low Earth orbit for 0.77km/s.
     Without a heatshield, 3.77km/s is required.
     A similar maneuver can use the Earth as a slingshot, departing from EML1 with a little nudge into any inclination and then burning at closest approach for best use of the Oberth effect.
     From EML1, geosynchronous orbit is only 1.38km/s away.

     Putting all of that together:
  • The best place for a fuel depot is at Earth-Moon Lagrange Point One (EML1). Fuel can be harvested at the harvester's pace, shipped to the depot at the tanker's pace and accumulated for later use. Fuel is shipped to LEO only as needed and into the correct inclination.

  • The surface to EML1 tanker needs to use chemical engines to overcome the Moon's gravity. It must carry about 4.6km/s of fuel, though the second half of the trip is empty and requires much less fuel. My reference tanker is 5.5 tons, cryogenic with zero boiloff and can deliver 29 tons of propellant from the Lunar surface to EML1, then land at the harvester. Each trip burns just under 34 tons, so the harvester must produce about 2.2kg of propellant for each kg in EML1.

  • The EML1 to LEO tanker can use either chemical or ion engines. The low thrust option requires a very different trajectory and a dV of about 7km/s, plus a lot of onboard power. This can be a competitive option but initially it would be simpler to use the same tanker for each leg. Because the vehicle needs to aerobrake, it requires a reusable heatshield. The same tanker design is used, but it is launched with a dual-use shroud of about 6.3 tons that is kept with the vehicle. This trip delivers 44 tons of propellant at a cost of 19 tons. So, for each kg in LEO the harvester has to produce 3.1 kg. That lines up fairly well with other sources suggesting 75 tons to be harvested for 25 tons in LEO.

     The harvester is an unknown quantity. There are several concepts (including one of mine), but I will use a more generic NASA number of 10kg propellant per kg of harvester per year, with 10% spares. That means if we want to harvest 100 tons of fuel per year we need to send 10 tons of equipment to start and 1 ton of spares for each year. This was for a Mars ISRU system with rover/excavator and integrated power systems. A Lunar system would be much simpler since it would only be melting and filtering water ice then electrolyzing it, so it is possible the equipment will produce far more propellant than this estimate.
     Cheap propellant in LEO is useful for missions to other planets or moons. It is also useful for supplying a LEO station with water and stationkeeping fuel. Satellite servicing tugs could base out of EML1 with a ready supply of fuel and easy access to all inclinations. If commercial satellites were modified to use a water electrolysis thruster system for stationkeeping then they could be launched empty to EML1 for less dV than a direct launch to GEO. A fill of fuel at EML1 and a 1.4km/s nudge would place the satellite in GEO with decades of stationkeeping thrust available. As a bonus, the upper stage of the launch system could be refueled and repurposed. Lastly, water is extremely useful for manned operations as radiation shielding, drinking water and a reserve source of oxygen.

     An example of why the interorbital exchange would be useful is NASA's Mars Design Reference Mission (DRM). Each manned trip requires three flights (one crew and two cargo), each using around 190 tons of fuel. Just the fuel would require 9 Block 1 SLS launches or 6 of the 105-ton launches; being generous we're talking about at least $4.5 billion. This is 570 tons of propellant over 2.1 years, or about 267 tons per year at around $7.9 million per ton. A full campaign of three flights to Mars would cost $13.5 billion in fuel. With lunar ISRU we can save at least $4.7 billion as described below (potentially over $9 billion) and gain a sustainable supply of propellant in EML1/LEO with minimal Earth mass.
     An ISRU plant with this capacity would mass at least 83 tons and consume about 18 tons of spares per Mars opportunity. A modified version of my tanker could land perhaps 17 tons of cargo on the Moon for about 62 tons of fuel; this would require two Falcon Heavy flights (~$300 million) or an SLS block 1 flight with two additional Falcon 9 refueling flights (~$850 million). This initial 15-ton plant (with 1 year of spares and a 500-kg dextrous robot for remote repair operations) would provide the first ISRU fuel as a proof of concept. The cargo lander would be refueled and returned to LEO two months later with plenty of lunar samples. (3 tons of samples, 25 tons of fuel.) At this point the whole architecture can be validated and the final ISRU design can be settled. Until this step happens we have to use some pessimistic numbers (as below), but there is the possibility that the pilot plant will be many times more productive than expected as it will be running a much simpler refining process.
     A standard tanker with dual-use shroud (11.8t empty) would be launched with a Falcon 9. Another standard tanker with 43.5 tons of fuel would be launched on a Falcon Heavy, transfer 27.8 tons of fuel to the shrouded tanker and then head to the Moon and land by the ISRU plant. The shrouded tanker would travel to EML1. At this point fuel can be transferred all the way to LEO; without a proper depot there are some inefficiencies, so only about 40 tons are delivered in each shrouded tanker (requiring two standard tanker flights to fuel up). Fortunately this is enough for the outbound trip of a cargo tug.
     The first shipment of 40 tons would take the rest of the year to produce and would be delivered to the cargo tug in LEO, allowing it to deliver a 22-ton payload to the Lunar surface. (Payload would be a second 15-ton ISRU plant, two years of spares for both plants and 1 ton of other cargo.) This could be a Falcon Heavy carrying two payloads or one of several competing options. After 30 days of surface operation the cargo tug returns to LEO (again, 3 tons of samples and 25 tons of fuel).
     The next 40 tons of fuel take a bit over five months to produce and allow the cargo tug to bring the next 22-ton package. Return fuel for the tug would take three weeks.
     At this point the infrastructure on the moon is producing 1.25 tons of fuel per day. Each cargo trip takes less and less time to refuel (3.4 months, then 2.6 months, then 2 months). A proper depot at EML1 and three more ISRU packages round out the system. The depot is 300-ton capacity, about 20 tons of hardware and delivered to EML1 by a Falcon Heavy. In total the buildup phase takes two years and two months, almost exactly one synodic period. 90 tons of ISRU hardware is on the surface with an annual production of 900 tons and spares requirements of 9 tons. This system can deliver 289 tons of fuel to LEO every year, or 617 tons per Mars synodic period. The target of 570 tons is met with an extra 47 tons of fuel for delivering spares.
     A total of seven Falcon Heavy flights are required, plus one Falcon 9. Let's call this $1.1 billion in launch costs over 26 months. Let's also assume that spares are supplied as 11-ton packages by Falcon 9, two per synodic period. A third assumption is that we will need to replace about 20% of the system every period (at a conservative 10-year lifespan for components), so we budget a Falcon Heavy flight for $150 million. That's an operational cost of about $250 million per period. In the first synodic period the fuel in LEO will cost $2.2 million per ton in launch costs. Each additional period will cost only $405,200 per ton in launch costs.

     The cost of all that hardware is difficult to estimate. Let's look at two very different systems and get a ballpark figure. The BA-330 expandable space station module from Bigelow is estimated to mass about 22 tons and cost about $250 million, or about $12 million per ton. By contrast, the Iridium NEXT constellation of 72 satellites is expected to mass 57.6 tons in total and cost $2.4 billion (not counting launch costs), or about $42 million per ton. The comsats include costs like bandwidth leases and operations, but let's use that figure anyway as a first approximation. The startup phase requires 131 tons of hardware, or about $5.5 billion. Extended operation will replace about 10% of that hardware per year at a cost of about $550 million. This ignores the significant commonalities between systems; all the propulsion units are identical, all tankers identical other than the cargo adapter and all six 15-ton ISRU plants are identical.
     This gives us the second part of fuel costs: capital expense. Each ton of fuel in LEO in the first period costs $9.8 million, with additional periods costing $890,000. These numbers assume we do not spread the capital costs over five periods, but front-load the entire bill into the first launch season. The first Mars caravan would cost $6 billion instead of $4.5 billion in fuel, but the next one would pay only $1.4 billion. A campaign of three flights to Mars would save about $4.7 billion in fuel costs. As a budget line item, the cis-lunar fuel network would cost NASA or a private operator $375 million per year once established.
     What if, instead, a cost-effective hardware program is used that is closer to the BA-330 in terms of cost per kg? Now our 131 tons of hardware only costs about $1.6 billion with annual replacement costs of $160 million (or per-period costs of $342 million). Under this assumption, the startup phase would cost $2.7 billion with operational costs of $592 million per period ($278 million per year). Propellant would cost $5.34 million per ton in the first period and $960,000 per ton thereafter. NASA would save about nine billion dollars on three Mars flights, and would even save about $1.2 billion on the first flight.


The first Earth-Moon Lagrange point, or EML-1, offers a number of key advantages that make it an ideal destination for activities in cislunar space. Over the near-term, however, its utility is constrained by a lack of physical infrastructure. This can change if our approach to space moves away from destinations and towards a strategy of enabling capabilities.

Talk abounds of going beyond Earth orbit, although once beyond low Earth orbit (LEO) what happens next becomes a little fuzzy in most discussions. This need not be the case, as capabilities can be built from the very first test of a trans-LEO vehicle. Some sample test runs:

  1. Out to GEO: Given launch locations of likely US crewed vehicles, the mission could involve a plane change to geostationary (perhaps through a bi-elliptical transfer for extra-credit), close-approach to a “zombiesat”, and perhaps even retrieval of some old hardware for forensic analysis.
  2. Free-return trajectory: A loop around the Moon to give the heat shield a workout on the return. Perhaps some maneuvering out around the Moon. How close can they shave the rear-end of the Moon at perilune?
  3. EML-1 visit: The main purpose would be to establish a halo orbit. Once there, it would make sense to drop off a package of instruments that could serve a number of purposes.

Instrumental to the use of EML-1 is the concept of the halo orbit. It is a technique that allows an object to orbit an empty space, typically a Lagrange point, as with SOHO, WMAP, Genesis, the future JWST, and others. The best, though inapt, way to think about it is as a sort of gyroscopic effect, as with a bicycle wheel, where the hub is on the line connecting the centers of gravity of two objects (like the Earth and Moon), and the satellite is on the wheel. The action of the orbit helps to keep the object in place; some station keeping is required, but at a level orders of magnitude less than the ISS.

The EML-1 neighborhood is good for looking not only outward, but also back in towards Earth. EML-1 is a naturally clutter-free environment, since space junk doesn’t normally have station-keeping capability, as well as a “high ground” that allows observation not only of the Earth but also everything that’s orbiting around the Earth out to GEO. Instruments could be placed there for the specific purpose of keeping an eye on the traffic in cis-GEO space. By the same token, it is also ideal for looking at the Moon, and serves as a natural gateway to the entirety of the Moon’s surface. Bigelow Aerospace has proposed using EML-1 as an aggregation point for modules to be emplaced on the Moon’s surface using Armadillo Aerospace rockets for the descent. As far back as 1986 a Lunar Spaceport was envisioned as a kind of motel/gas station/warehouse/restaurant/garage for space travelers.

The Moon is still a bit in the future, though, as there are still a lot of things to consider on the Earth side of EML-1. One of the key advantages of staging at EML-1 is, as Brad Blair notes, “its ability to fall into various inclinations without a major [delta-V] penalty, thus increasing the number of customers that could be reached by a small set of vehicles and systems elements.”. What this means is that the inclination you end up in in LEO is set by how you depart from EML-1.

If you picture the Earth-Moon system, and the line connecting their centers of gravity, EML-1 is about 85 percent of the way to the Moon. Trace an ellipse from the EML-1 point down around the Earth and back up to EML-1. Put the perigee close enough to Earth and you can even get some aerobraking. This ellipse can be assumed to be in the orbital plane of the Moon. Now, rotate that ellipse around the Earth-Moon axis. This means that every inclination of LEO orbit is accessible, from the 28.5° of Kennedy Space Center, to the 51.6° of ISS, to even polar orbits, although the latter suffer from more delta-V penalty by virtue of the Earth’s oblateness.

If all of the LEO inclinations are available from EML-1, then it is also true that any LEO inclination can get to EML-1. This means that the ISS can serve as a staging point for missions to EML-1 in the nearer term, and later stations in different inclinations can also reach EML-1 as they come online. There is no need to wait to get started. As soon as a crew vehicle comes online it can start staging from ISS to EML-1, first as test-runs, then as missions to emplace as well as service, upgrade, and refuel assets. By the time crewed facilities are emplaced there will already be regular traffic to the location.

One question often raised is “What would a crew do at EML-1?” There are a myriad of answers:

1) In terms of propellant, it is cheaper to go from EML-1 to GEO and back to EML-1 than it is merely to go from LEO to GEO. Over the long term, it makes sense to stage GEO operations from EML-1. What kind of operations? The easiest answer is salvage, given the hundreds of tonnes of scrap circulating in GEO. Crews could fall down to GEO, spend a few days retrieving defunct equipment like failed satellites, and then return to EML-1 to process it. Whatever could be reused in some way is unknown, but the real value is in the forensic analysis of how the satellite weathered in the GEO environment over a known period of time. That kind of information allows for better satellite design.

2) EML-1 is an on-ramp to what are known as the InterPlanetary Superhighways (IPS). These are a network of ridges and ripples in space created by the gravitational effects of the planets and Sun. A satellite pushed onto the IPS will travel very, very slowly along this network to its destination, where it can kick itself into a halo orbit around a Lagrange point and collect data. Locations of interest would include the Sun-Mars L-2 and Sun-Jupiter L-1, to observe the Asteroid Belt; the Sun-Venus equilaterals at L-4 and L-5 to provide communications relay when Mars is on the other side of the Sun from Earth; Sun-Saturn L-2 to look at the Kuiper Belt; Sun-Neptune L-2 to look at the Oort Cloud; Sun-Mars L-1 as a waypoint on the way to Mars and the Asteroid Belt; Sun-Earth L-1 to watch the Sun; Sun-Earth L-2 to watch the stars. The key is that all of these instruments would also be able to return via the IPS to EML-1 for regular maintenance and servicing. As more probes are added to the network, instead of thrown into the void, there will be an increasing stream of probes in need of work.

3) The time lag from EML-1 to the Moon and back is much less than that for Earth-Moon. As a result, it is a better location for safe teleoperation of robots on the lunar surface.

4) As lunar activities ramp up, there will be an increasing need for freight handling of goods destined for the Moon, as well as those from the Moon. Early lunar exports are likely to be low-value-added goods such as oxygen, water, raw regolith, and some metals, but as more capabilities are established the exports will start creeping up the value-added chain: foodstuffs from lunar greenhouses, crafts created by the locals from local materials, increasingly sophisticated entertainment like dance and music, and so forth.

5) EML-1 is an ideal location to aggregate mission components for a trip to an asteroid. Fuel can come from the Moon, while spacecraft come from Earth. Someone’s going to have to put all of that together.

6) A facility at EML-1 can serve as a communications node for lunar operations to overcome the line-of-sight issue. Additionally, with solar sails “pole-sitting” above the north and south lunar poles, communications with the far side can be established.

7) Port services. While probes returning on the IPS will end up in the neighborhood of EML-1, they will need to be picked up. Same thing with freeflyer platforms sent on low-energy trajectories around the Moon for production runs. A space tug would be a good tool to have, and someone has to fly it.

These are just a few ideas, which can easily be expanded. If a crew can fall down to GEO for a servicing run, it can also fall down to HEO, MEO, and LEO for servicing missions. If an asteroid mission can be assembled at EML-1, so too can a Mars mission. If crews are salvaging dead satellites and kick stages from GEO, they may be able to cobble together the parts for other missions, selling the result to whomever wants to buy a space probe.


      Earth Moon Lagrange 2 or EML2 is one of 5 locations where earth's gravity, moon's gravity and so called centrifugal force all cancel out. It lies beyond the far side of the moon at about 7/6 of a lunar distance from earth.

     Infrastructure at any of these 5 locations could be kept in place with a small station keeping expense. Other high earth orbits would be destabilized by the influences of the earth, moon or sun.

     Of these 5 locations, EML2 is the closest to escape. How close?

Specific orbital energy is given by
v2/2 - GM/r

v: velocity with regards to the earth
G: gravitational constant
M: mass earth
r: distance from earth center

     Here's specific orbital energies for a few orbits:

     For EML1 and EML2 I'm looking at resulting earth orbits for payloads nudged away from Luna's Hill Sphere.

     Most the energy is getting from earth's surface to Low Earth Orbit (LEO). Then another huge chunk is getting from LEO to escape.

     EML2 is right next door to escape (aka C3=0). If the goal line is Trans Mars Injection, EML2 is on the 9 yard line.

     EML2's orbital energy is about -180,000 joules per kilogram. How much is that? Well, Kattie is standing next to the small generator which provides electricity for our business during power outages during the summer monsoons. It would take this 20 kilo-watt generator 9 seconds to crank out 180,000 joules.

     An EML2 payload nudged away from Luna would rise to an 1.8 million km apogee. An ordinary earth orbit at 450,000 kilometers from earth's center would move about 0.94 km/s. But since EML2 is moving at the moon's angular velocity, it is traveling 1.19 km/s. Earth's Hill Sphere is about 1.5 million km in radius. So depending on timing, an EML2 nudge could send a payload out of earth's sphere of influence into a heliocentric orbit.

     Another possibility is the sun's influence could send a payload back towards the earth with a lower perigee:

     All of these pellets were nudged from EML2. The sun's influence has wrested most of these from earth's influence. But check out pellet number 3 (orange). The sun's influence has dropped this pellet to a perigee deep in earth's gravity well. For a .1 km/s nudge from EML2 we can get a deep perigee that can give a very healthy Oberth benefit. However, such a route takes about 100 days.

Farquhar Route

     Using an lunar gravity assist along with an Oberth enhanced burn deep in the moon's gravity well, EML2 is 9 days and 3.5 km/s from Low Earth Orbit (LEO):

     This route was found by Robert Farquhar.

Bi-Elliptic Transfers

     If radii of two different orbits differ by a factor of 11.94 or more, a bi-elliptic transfer takes less delta V than Hohmann. EML2 radius / LEO radius is about 67, so LEO to EML2 could definitely be a beneficiary of bi-elliptic.

     From LEO, a 3.1 km/s burn gets us to a hair under a escape. A multitude of elliptical orbits fall under this umbrella!

     As you can see, it takes almost as much to get as high as EML1 as it does to reach a 1.8 million km apogee. I chose 1.8 million as an apogee since a 450,000 x 1,800,000 km ellipse at perigee has the same altitude and speed as EML2. At perigee a payload can slide right into EML2 with little or no parking burn.

     What's needed is an apogee burn to raise perigee to 450,000 km. A 6738x1,800,000 km ellipses moves very slow at apogee, a mere 0.04 km/s. A 450,000 x 1,800,000 km ellipse doesn't move much faster at apogee, about 0.3 km/s So a .26 km/s apogee burn suffices to raise perigee.

     So the total budget is 0.26 + 3.1555 km/s. This 3.42 km/s delta V budget is better than a Hohmann but about the same as Farquhar's 9 day route.

     But recall apogee is beyond earth's Hill Sphere. With good timing, the sun can provide the apogee delta v.

Hop's Route from LEO to EML2

     Here's a route I found with my shotgun orbital sim:

LEO burn is about 3.11 km/s. Payload passes near the moon on the way out, boosting apogee and rotating line of apsides. The sun boosts apogee as well as perigee. Coming back the pellets slide right into EML2 (the circular path alongside the Moon's orbit).

This LEO to EML2 route took 74 days and 3.11 km/s.

EML2 and Reusable Earth Departure Stages.

     Using the Farquhar route, it takes about 0.4 km/s to drop from EML2 to a perigee moving just under escape velocity. At this perigee 0.5 km/s will give Trans Mars Insertion (TMI). After the departure stage separates from the payload it's pushing, it can do a 0.5 km/s braking burn to drop to an ellipse with a near moon apogee. Once at the moon, another 0.4 km/s takes the EDS back to EML2.

     For massive craft moving from between earth's neighborhood and other heliocentric orbits, it makes little sense to climb down to Low Earth Orbit (LEO) and back each trip. It saves time and and delta V to park at EML2 on arrival. If EML2 becomes a stop for interplanetary space craft, a reusable EDS is a good way to depart the earth/moon neighborhood.

     I talk about this in more detail at Reusable Earth Departure Stages.

EML2 and Fast Transits

     Here's a pic of a Non Hohmann Mars transfer:

     Mars and earth orbits are approximated as circular orbits. A Hohmann orbit will have a 1 A.U. perihelion and a 1.52 A.U. aphelion. The transfer orbit above has perihelion 0.7 A.U. and aphelion 1.53 A.U. Semi-major axis of this orbit is (0.7 + 1.53)/2 A.U. or 1.115 A.U. Orbital period is 1.1153/2 years which is about 1.18 years.

     The trip to Mars isn't the entire orbital period though, just the turquoise area swept out from departure to destination. The turquoise area is 31.5% of the ellipse's area. 31.5% of 1.18 years is about 135 days or about 4.4 months.

     Departure and arrival Vinf are indicated by the red arrows. These are the vector differences between the transfer orbit's velocity vector and the planet's velocity vector at flyby. A change in direction accounts for most of the Vinf. I'm assuming Mars and Earth are in circular orbits with a zero flight path angle. Therefore the direction difference between vectors can be described with the flight path angle of the transfer orbit's velocity vector.

     In this case the earth departure Vinf is 11.3 km/s. That's a big Vinf! But if falling from EML2, only a 4.9 km/s perigee burn is needed. This is doable.

     At Mars the Vinf is 5.14 km/s. But a periaerion burn of 2.57 km/s brakes the orbit into an (3697x2345 km ellipse. This orbit could be circularized via periaerion drag passes through the upper atmosphere. Since this ellipse has a period less than a day, orbit could be circularized in a few weeks.

     An upper stage can have a 8 km/s delta V budget. Recall it takes about 0.4 km/s to fall from EML2. Therefore let's try to find a route that takes about 7.6 km/s from perigee burn to periaerion burn.

     Trial and error with my Non Hohmann Transfers spreadsheet gives:

     With chemical rockets departing from EML2, I believe 4 month trips to Mars are doable.

EML2 Proximity to Possible Propellent Sources.

     In terms of delta V, time and distance EML2 is quite close to several possible propellent sources.

     There are thought to be frozen volatiles in the lunar cold traps. Some craters at the lunar poles have floors in permanent shadow. Temperatures can go as low as 30 K. Volatiles that find their way to the cold traps would freeze out and remain. There may be rich deposits of H20, CO2, CH4, NH3 and other compounds of hydrogen, carbon, oxygen and nitrogen. These would be valuable for life support as well as propellent.

     The moon's surface is about 2.5 km/s from EML2.

     Also there are proposals to retrieve asteroids and park them in lunar Deep Retrograde Orbits (DROs). DROs are stable lunar orbits that can remain for centuries without station keeping. Planetary Resources would like to retrieve water rich carbonaceous asteroids. Carbonaceous asteroids can contain up to 20% water by mass in the form of hydrated clays. They can also contain compounds of carbon and oxygen.

     LDROs would be about 0.4 km/s from EML2.


     EML2 would make a great transportation hub. Not only for travel to destinations throughout the solar system but also within our own earth moon neighborhood.

From EML2 by Hollister David (2015)

     This entry covers near-term resources on and near Mars and how they might be transported.
     I assume the propellant network described in part 1 has been built, or at least that lunar propellant is available at Earth-Moon Lagrange Point One (EML1).
     The short version of the below is that using hardware similar (or identical) to the part 1 Lunar infrastructure, cargo to and from Mars becomes relatively cheap.
     A set of three NASA-reference mars missions could have their cargo requirements filled for a total of $11.4 billion (including fuel).
     Nitrogen and argon from Mars could be as cheap as $400 per kg at EML1.

     Again, let's start with the basics.

     Mars has a surface gravity of 3.711m/s² or 37.6% of Earth gravity, and a surface rotation of about 0.24km/s.
     Mars is blessed with a thin atmosphere, mostly carbon dioxide but with useful amounts of nitrogen and argon.
     Martian soils are rich in perchlorates and relatively rich in water.
     The north and south poles have permanent ice caps, mostly water ice under a layer of frozen CO2.
     CO2 slabs violently sublimate in the spring, making the edges of the ice caps fairly dangerous in this season. Otherwise the dust storms are not a serious threat.
     Takeoff and landing requires 4.1km/s; drag can save as much as 2.4km/s of this on landing.
     Mars has two moons, Phobos and Deimos. Both are believed to be captured asteroids, probably C-type.
     From EML1, Mars transfer costs 0.74km/s. Mars capture costs 0.9km/s and the move to low Mars orbit costs 1.4km/s. Trip total is just over 3km/s.
     From low Mars orbit, reaching Phobos costs 1.4km/s and reaching Deimos costs 1.9km/s.
     Launch opportunities to or from Earth (using a Hohmann transfer orbit) occur every 2.135 years, or about 26 months.

     Taking all of this together we want a surface location near the equator and a depot in low orbit. If we find significant amounts of water at either Phobos or Deimos then we want a mining outpost there. It would be nice if we could set up a Phobos-anchored tether for orbit changes.

     Getting cargo to Mars is slow and expensive. The post in part 1 used NASA's Mars Design Reference Mission (DRM) as a baseline to show how in-situ resource utilization (ISRU) could save money on fuel. Let's look at other ways to save.
     For starters, let's use the same cargo tug as described in part 1. This is a 5.5 ton dry vehicle that would deliver 50 tons of payload to EML1 using 77 tons of Lunar fuel and a reusable 15-ton (fueled) drop tank. The tug and payload would refuel with 63 tons of lunar fuel and continue on to Mars with fully propulsive capture to low orbit. These tugs can be used as fuel tankers between Phobos and LMO and can also be used to return cargo to Earth (up to 52 tons to EML1 all propulsive).
     Once cargo is in low Mars orbit, a different vehicle is needed to land it. The cargo tugs are capable, but multiple atmospheric landings in Mars gravity are out of reach. Instead, let's use the Access to Mars SSTO ferry (Strickland, Gopalaswami). This is a 30-ton dry mass, reusable SSTO cargo ferry for moving payloads to and from the Martian surface. The vehicle is 14 meters in diameter, which poses a problem; we would need a larger-diameter booster, a way to assemble the vehicle in orbit or a way to launch such a wide payload on an existing rocket. The design could probably be scaled down, but extrapolating the performance of a smaller version is not trivial. I will assume the problem is solved without specifying how. If reliable fuel is available from Phobos then the lander might be redesigned to refuel both in LMO and on the surface, allowing it to carry more payload each way.
     The cargo lander is intended to fuel up, launch to orbit (with 5 tons of payload or excess fuel), collect a 25-ton payload and land. Repeat as needed. Each 50-ton tug payload would require two lander trips. NASA's reference mission involves 80 tons of cargo to the surface, so two such flights would be required. Note that the ~40-ton DAV would not be required at all; a crew version of the lander can ferry crew to and from the surface. That suggests that a single 50-ton payload could include all of the required surface habitat, science equipment, power, rovers, food, etc. The first mission would require a cargo lander and crew lander as well as an orbital depot, so the first mission would require three 50-ton cargo flights to establish infrastructure along with the surface cargo. Each additional mission would require only one cargo flight.
     Each lander flight requires 95 tons of fuel, and each mission requires two flights (one 25-ton cargo, one 20-ton cargo + crew). This 190 tons requires about 9 tons of ISRU plant and 2 tons of spares. The Phobos ISRU plant should provide 15 tons of fuel for each lander. We might also send a single tug flight back to Earth each period for a cost of 63 tons of propellant from Phobos. That totals about 7.4 tons of ISRU plant and 1.6 tons of spares. A cargo tug can haul fuel from Phobos to the LMO depot, delivering 37.2 tons per trip at a cost of 25.8 tons of fuel.

     So, let's compare this to the baseline NASA plan over the course of three missions to Mars. The first trip requires three cargo flights to establish the orbital depot, Phobos ISRU base, tanker fleet and lander fleet. A habitat, science payload, ISRU facility, food and other supplies are delivered to the surface. Total cost is two landers (60 tons), three tugs (16.5 tons), 420 tons of Lunar fuel, a ~15-ton depot (200-ton capacity) and 16.4 tons of ISRU plant (with 3.6 tons of spares). That leaves 55 tons of payload available for the surface mission, with the understanding that the surface ISRU system will provide sufficient water and buffer gas.
     As a first-mission flight, the fuel alone will cost $2.24 billion. Using a middle of the road estimate of $30 million per ton for hardware (including surface payloads) that's almost exactly $5 billion. Launch costs would be three Falcon Heavy and a Falcon 9, about $500 million. Total mission cost, $7.75 billion. Note that this does not include the crew launch, transit habitat or crew recovery; these will be discussed in a later post.
     Future flights would require a single cargo flight, 55.5 tons of hardware ($1.67b) and 140 tons of lunar fuel ($135m). All other components are reusable and already present. Total pricetag for the cargo end is $1.8 billion for each additional mission. After about the fifth mission some of the infrastructure hardware will need scheduled replacement, so this cycle of one expensive mission and four cheap missions could continue indefinitely or the replacement costs could be spread across multiple missions. Still, $11.4 billion for three missions to Mars is cheap compared to $2.5 billion for MSL/Curiosity (which was money well spent) or the $156 billion for Apollo to put men on the moon.

     Looking past the baseline, the Mars surface base is able to supply nitrogen for breathing gas and argon for electric engine fuel. This can be carried back to EML1 in a reusable cargo tug that paid for itself by delivering its first payload to Mars orbit. The same tug can be reused multiple times. Ultimately the cost of shipping along this route is the cost of spares and replacement of the various ISRU bases, depots and tugs. With Earth launch costs in the $3 million per ton range, any advantage is worth pursuing. Cargo from Mars costs about 126kg of spares to Mars per ton delivered to EML1. Cargo to Mars costs about 76kg of spares to the Moon per ton delivered to LMO. Of course each trip requires the use of a cargo tug costing anywhere from $66-$165 million but in terms of ongoing costs we're looking at 6.78 tons from Earth to support a 50-ton cargo from Mars, a better than 7:1 ratio. Another way to say it is for $20 million in launch costs we can get 50 tons of argon and nitrogen (or Mars core samples or Phobos turnings, etc.) at EML1 for use elsewhere once the system is established, a savings of at least $130 million.


For travel throughout cislunar space, I’ve long been an advocate of having depots on both ends of the journey. The LEO depot provides a refueling stop at the first practical point after leaving the ground, and also a spot for bringing vehicles back from lunar space for refueling for their next trip out. The lunar orbit depot plays a similar role for flights to/from the lunar surface, as well potentially, as being a staging location for departures into interplanetary space. By launching from a lunar facility near the top of earth’s gravity well, it’s both possible to use low-thrust trajectories in and out of cislunar space, as well as to do an earth swingby with a departure burn at apogee for high-thrust departures taking maximum advantage of the Oberth effect.

One important question however has been where to place the lunar orbital facility.

Lunar Orbital Facility Orbit Options
A recent FISO telecon presentation by Ryan Whitley and Roland Martinez of NASA JSC describes and discusses several of these staging orbit options. I’ll be reposting snapshots of a few of their slides to introduce the orbits, but here you can find their full presentation:

They discuss most of the commonly cited options including Low Lunar Orbit, Frozen Orbits, L2 Halo Orbits, Distant Retrograde Orbits, and a more recently discovered option, Near Rectilinear Orbits.

This slide shows some of the smaller lunar orbit options and descriptions (click for larger image):


And this slide shows some of the larger lunar orbit options, with descriptions (click for larger image):


And this slide shows all of the orbits relative to each other to give you a better idea of what they look like (click for larger image):


Comparison of Options

While Whitley and Martinez in their FISO telecon focus on evaluating the various staging orbits from the standpoint of NASA missions using the Orion capsule, they still provide a lot of useful information for evaluating options for the location of a lunar orbital facility/depot. To me, some of the considerations for locating a lunar orbital facility are:

  • How frequently do you have opportunities to travel from a LEO facility to the lunar facility, and how frequently you can travel the other direction?1
  • How much delta-V does it take to go between the facility and LEO and the facility and the lunar surface?
  • How long is the transit between the location and the lunar surface?
  • How useful is the orbit for supporting deep space missions?
  • How hard is it to reach various lunar surface destinations from the lunar orbital facility location?
  • What is the thermal environment like in the orbit?
  • And how much of the lunar surface to destination delta-V can be provided by some sort of propellantless lunar launch scheme2?

Based on these considerations, I’d like to focus the rest of this post on the pros and cons of the two options I consider most interesting–L2 Halo Orbits and Near Rectilinear Orbits.

Pros and Cons of EML-2 Halo Orbits
EML-2 orbits have been my favorite option ever since learning about the low delta-V cost of reaching them via powered lunar swingbys. They have a lot going for them, including:

  • One of the lowest delta-V stopping points in the lunar vicinity, requiring only ~3.43km/s of delta-V from LEO.
  • Easy access to/from a LEO facility on every LEO-lunar or lunar-LEO window.
  • Any-time access to/from anywhere on the lunar surface.
  • Low stationkeeping delta-V3
  • Benign and cold thermal environment4
  • Continuous communications with Earth, and most of the farside of the Moon.
  • Good staging point for both deep-space and lunar missions.
  • Could become a starting location for a lunar space elevator.

But EML-2 does have a few drawbacks:

  • Long LEO-EML2 and EML2-LEO transit times5 for the low delta-V powered-swingby option.
  • Long EML2 to lunar surface (and vice versa) travel times6
  • It wasn’t clear that a propellantless lunar launch option located at either pole could launch easily to EML2. An elliptical orbit from such a launcher would have its line of apsides pass through the launch location, which would be orthogonal to the Moon-EML2 line. You could launch into a polar LLO, and then do multiple burns from there to EML2, but the propellantless launch option would only provide the first leg of the trip (surface to LLO).

The long trip times mean that the vehicles taking people between LEO and EML2 and between EML2 and the Moon will require much more extensive life support and accommodations than would be needed if the trip were shorter. That will drive up the dry mass of those systems, and by extension the propellant and overall cost of moving people to and from EML2.

Pros, Cons, and Questions Regarding Near Rectilinear Orbits
Starting several months ago, some of my astrogator friends started telling me about NASA’s interest in Near Rectilinear Orbits for exploration missions. After all the talk about Distant Retrograde Orbits, this sounded a bit like the “flavor of the week” syndrome, but the FISO presentation helps explain some of the allure of such orbits:

  • Only slightly higher delta-V to/from LEO to NROs compared to LEO to EML27.
  • Because the NRO orbit’s perilune is only 2000km from the Moon’s surface, once per 6-8 day orbit, the orbit lines up so that the travel time between NROs and the lunar surface drops to 0.5 days.
  • Powered swingby trajectories between LEO and NROs take approximately 5 days each direction, instead of 9-11 for EML2.
  • Slight lower delta-V between NROs and the lunar surface compared to EML2.
  • The NRO is close enough to an elliptical polar orbit that it might be possible for a polar base to use propellantless launch techniques to fling payloads nearly into NRO, with possibly only minor adjustments and raising the perilune with a burn near apolune half an orbit later8

The benefits of shorter transit times are pretty important, but there are still a couple of relative drawbacks and open questions:

  • While it’s possible to get from LEO to a given NRO orbit during every lunar injection window, the NRO facility will be at different points in its orbit during each window, which may make a first-orbit rendezvous either infeasible or it might cost additional delta-V. I’d want to get this resolved, because while this isn’t an issue for one-off, ground-launched missions like the NASA folks were thinking of, this would be a real issue for reusable spaceship flights between a LEO and NRO facility.
  • Likewise, departures from the NRO may not be in the optimal part of the orbit for the Earth return maneuver when the timing is right to return to the plane of the LEO facility. This isn’t a problem if you’re doing a direct return, but once again is a big pain in the neck for reuse of space hardware. Once again this is something I’d want to analyze more before settling on an NRO orbit.
  • Additionally, the NRO facility has LOS with one lunar pole about 86% of the time (while heading out and coming back from apolune), but only sees the other facility for a brief period near perilune. If you’re planning on using propellantless launch methods to send stuff from a polar lunar settlement to the NRO facility, it’s going to be in an NRO with apilune on the opposite side of the moon from your lunar settlement, meaning you’ll only be in contact briefly for maybe 1 day out of a week.
  • Because the perilune is only 2000km, the heating environment is going to be warmer than EML2, with slightly higher boiloff, but this is probably only a minor difference–it should still be tons easier to keep cryo boiloff low in an NRO than in LEO.

While NRO orbits have some really interesting characteristics, I’d really want answers to those first two concerns before I’d pick it for the location of a lunar orbital facility. If you can’t get to it on a regular basis from a given LEO depot without having to do complicated trajectories, or paying big penalties in flight duration or delta-V, then that would likely outweigh the benefits. If on the other hand, it’s not a big deal to adjust the trajectory on the way to and from the NRO facility to enable rendezvous with the facility regardless of where it is within its orbit when the LEO to lunar launch window opens, then it could be a really interesting location for a lunar transportation node. I’ll have to see if I can get some of my astrogator friends to weigh in on those questions. Until then I’m probably still more of a fan of EML-2, in spite of the annoyingly long transit times.

[Update 1: After speaking with an astrogator friend who’s been looking at NROs to support lunar missions, he thinks it might be possible to put an NRO facility in an orbit whose period is synchronized with the average time between launch windows from the LEO facility. If that works, that would mean the NRO facility would be in approximately the same part of its orbit during each trip to/from the Earth. There are questions of if you can make an NRO orbit with a long enough period (~9 days) to make that work, and if the NRO facility could be made to line up both for arrivals and departures from/to Earth, but hopefully he’ll have more opportunity to dig into that further later this year.]

  1. Due to the orbital motion of the Moon and nodal regression of a LEO facility, you get optimal lunar departure and/or return options about every 7-9 days IIRC. The choice of lunar orbital facility location may constrain this further.
  2. Lunar Slings, Mass Drivers, Launch Loops, etc. All the stuff I was supposed to write about in my “The Slings and Arrows of Outrageous Lunar Transportation Schemes” series that I still need to finish
  3. <10m/s/yr
  4. About 10x lower LOX/LH2 boiloff rate than LEO. In fact with passive insulation you can completely surpress LOX boiloff and even freeze oxygen at EML-2
  5. 9-11 days
  6. 3-5 days
  7. 3.58km/s vs 3.43km/s
  8. Which you’d also want to be the burn that brings you to rendezvous with the NRO facility

Kuck Mosquito

Kuck Mosquitoes were invented by David Kuck. They are robot mining/tanker vehicles designed to mine water propellant from icy dormant comets or D-type asteroids and deliver it to an orbital propellant depot.

Form follows function. So it is unsurprising that the Kuck Mosquito resembles an Enterobacteria phage T4 virus. Only difference is that the virus is injecting, while the Mosquito is sucking out.


Because LEO is drier than the driest desert, there is money to be made by importing water from nearby worlds. The closest hydrated body to LEO, speaking in delta-v terms, is the moonlet Deimos (closer than the Earth, closer than Luna.) See “The Deimos Water Company” by David Kuck of Oracle, Arizona for details.

Kuck mosquito — As icy dormant comets or D-type asteroids are warmed by the sun, they accumulate an outer anhydrous lag layer. An in-situ mining robonaut called the Kuck mosquito is designed to drill through this layer, inject steam, and pump out the water in the core. Some of the water is electrolyzed for fuel for a small H2-O2 chemical engine. To gain a secure foothold, thermal lances melt into the substrate. The targeted bodies must have a cometary matrix of not less than 30% ice. There is a danger of catastrophic fracture of the subsurface mantle layer due to the tensile forces generated by the pressurization. Dave Kuck, “The Exploitation of Space Oases,” Princeton Conference on Space Manufacturing, Space Studies Institute, 1995

(ed note: in the game, Kuck Mosquitos have 220 kilonewtons of thrust and a specific impulse of 460 seconds. The water bag masses 40 metric tons because that is the standard measurement in the game.)

From High Frontier game by Philip Eklund (2010). Atomic Rocket Seal of Approval.

In 2007 it is difficult to maintain a space station in Low Earth Orbit (LEO). Before we can hope to colonize asteroids we need a better way to get out of LEO.

Kuck mosquitoes (designed by David Kuck of Oracle, Arizona) are small, unmanned craft that consist of not more than a drill, a heating element, and a bag house to store extracted volatiles. (ed note: it will also require a source of electricity. Maybe an RTG or solar cell array)

Sending small Kuck mosquitoes to Near Earth Asteroids to retrieve water and fuel is more doable than manned missions.

A few Kuck mosquitoes returning to earth orbit with full bag houses would make LEO much more hospitable.

These mosquitoes could be tankers for LEO fuel depots. LEO fuel would make manned spaceflight to the moon, Mars and asteroids much less difficult.

From KUCK MOSQUITO by Hop David (2007)

Using steam to propel a spacecraft from asteroid to asteroid is now possible, thanks to a collaboration between a private space company and the University of Central Florida.

UCF planetary research scientist Phil Metzger worked with Honeybee Robotics of Pasadena, California, which developed the World Is Not Enough spacecraft prototype that extracts water from asteroids or other planetary bodies to generate steam and propel itself to its next mining target.

UCF provided the simulated asteroid material and Metzger did the computer modeling and simulation necessary before Honeybee created the prototype and tried out the idea in its facility Dec. 31. The team also partnered with Embry-Riddle Aeronautical University in Daytona Beach, Florida, to develop initial prototypes of steam-based rocket thrusters

“It’s awesome,” Metzger says of the demonstration. “WINE successfully mined the soil, made rocket propellant, and launched itself on a jet of steam extracted from the simulant. We could potentially use this technology to hop on the Moon, Ceres, Europa, Titan, Pluto, the poles of Mercury, asteroids — anywhere there is water and sufficiently low gravity.”

WINE, which is the size of a microwave oven, mines the water from the surface then makes it into steam to fly to a new location and repeat. Therefore, it is a rocket that never runs out of fuel and can theoretically explore “forever.”

(ed note: well, to be more precise, it never runs out of water propellant. It still needs fuel in the form of solar panels or RTGs. The former suffers a power drop-off once you get further from the sun, such as at Mars or the asteroid belt. The latter currently have a useful lifespan of about 30 years)

The process works in a variety of scenarios depending on the gravity of each object, Metzger says. The spacecraft uses deployable solar panels to get enough energy for mining and making steam, or it could use small radiosotopic decay units to extend the potential reach of these planetary hoppers to Pluto and other locations far from the sun.

Metzger spent three years developing technology necessary to turn the idea into reality. He developed new equations and a new method to do computer modeling of steam propulsion to come up with the novel approach and to verify that it would actually work beyond a computer screen.

The development of this type of spacecraft could have a profound impact on future exploration. Currently, interplanetary missions stop exploring once the spacecraft runs out of propellant.

“Each time we lose our tremendous investment in time and money that we spent building and sending the spacecraft to its target,” Metzger says. “WINE was designed to never run out of propellant so exploration will be less expensive. It also allows us to explore in a shorter amount of time, since we don’t have to wait for years as a new spacecraft travels from Earth each time.”

The project is a result of the NASA Small Business Technology Transfer program. The program is designed to encourage universities to partner with small businesses, injecting new scientific progress into marketable commercial products.

“The WINE-like spacecrafts have the potential to change how we explore the universe.” – Kris Zacny, vice president of Honeybee Robotics

“The project has been a collaborative effort between NASA, academia and industry; and it has been a tremendous success,” says Kris Zacny, vice president of Honeybee Robotics. “The WINE-like spacecrafts have the potential to change how we explore the universe.”

The team is now seeking partners to continue developing small spacecraft.

Metzger is an associate in planetary science research at UCF’s Florida Space Institute. Before joining UCF, he worked at NASA’s Kennedy Space Center from 1985 to 2014. He earned both his master’s (2000) and doctorate (2005) in physics from UCF. Metzger’s work covers some of the most exciting and cutting-edge areas of space research and engineering. He has participated in developing a range of technologies advancing our understanding of how to explore the solar system. The technologies include: methods to extract water from lunar soil; 3D printing methods for structures built from asteroid and Martian clay, and lunar soil mechanic testers for use by gloved astronauts.

Honeybee Robotics, a subsidiary of Ensign Bickford Industries, focuses on developing drilling tools and systems for finding life as well as for space mining for resources. Honeybee has previously deployed and operated Rock Abrasion Tool (RAT) on Mars Exploration Rovers (MER), Icy Soil Acquisition Device (ISAD) on Mars Phoenix, and Sample Manipulation System (SMS) for the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL). The MSL also has Honeybee’s Dust Removal Tool. Current flight and R&D projects include systems for Mars, the Moon, Europa, Phobos, Titan, and others.

Kuck Mosquito
PropulsionH2-O2 Chemical
Specific Impulse450 s
Exhaust Velocity4,400 m/s
Wet Mass350,000 kg
Dry Mass100,000 kg
Mass Ratio3.5
ΔV5,600 m/s
Mass Flow49 kg/s
Thrust220,000 newtons
Initial Acceleration0.06 g
Payload100,000 kg
Length12.4 m
Diameter12.4 m

Deimos, the outer moon of Mars, is possibly the most accessible source of water to LEO. Lewis has shown the delta-V to go from LEO to Deimos is less than that needed to land on Earth's Moon. Partial loss of velocity at Mars might be obtained by a shallow dip into the Martian atmosphere. The delta-V to return from Deimos to HEEO (Highly eccentric Earth orbit) is very small. The travel time is roughly two years. The Moon may be used as an aid to accelerate and decelerate a vehicle as it leaves LEO and arrives at HEEO. Shallow penetration of the Earth's atmosphere may be used to loose velocity and aid in capture into HEEO.

Bodydelta-V Surface to LEO (m/sec)time of flight (d)delta-V LEO to Surface (m/sec)time of flight (d)

(ed note: the important part is LEO to Deimos Surface is deltaV=1800 m/s and 270 days transit, Deimos Surface to LEO is deltaV=5600 m/s and 270 days transit.)

A disadvantage of Deimos is the 26 month delay between launch opportunities.

Fanale calculates that ice should exist at a depth of 100 meters at the equator and at a depth of 20 meters at the poles of Deimos. Thus, the drilling equipment proposed in 1995 by Kuck should be able to reach ice at or near the poles, but not near the equator.

To move 100 tonnes of water ice from Deimos to LEO will require 250 tonnes of water ice for propellant (Z). Thus, in order to leave Deimos 350 tonnes must be propelled from the surface. A 1,000 cubic meter collection bag should be large enough to contain the 350 tonnes of ice, cuttings & other precipitates.

(ed note: 100 metric tons payload + 250 metric tons propellant implies mass ratio of about 3.5, since engine and structural mass are a small fraction of this (e.g, by the table below, the drilling equipment is 0.3 metric tons). If it electrolyzes the propellant into O2 and H2 and burns it as chemical fuel with a specific impulse of 450 seconds, this would give a delta-V of around 5,500 m/s or so.)

Table 1. Mass of Drill and equipment for the Deimos version of the drill presented in "Exploitation of Space Oases" presented at Princeton May 1995. The total mass is in grams. The drill pipe is titanium for lightness and chemical resistance to corrosion.
Down The Hole Hammer Drill, Titanium drill pipe & accessories
L (mm)OD (mm)ID (mm)Weight (grams)NumberWeight (grams)Ti
Hammer DTH210162333699No
Under-reamer Guide782049.43148.2Yes
Casing Shoe21241610160No
Collar Pipes1000434013741013740Yes
From THE DEIMOS WATER COMPANY by David Kuck (1997)

The images below are details of the "Spider" water harvester carried by the Robot Asteroid Prospector. It performs much like the business end of the Kuck Mosquito.

Optimizing Depot Placement

Takuto Ishimatsu's Ph.D. thesis is titled Generalized multi-commodity network flows : case studies in space logistics and complex infrastructure systems (abstract here). Basically: manually chosing where to place in-situ resource allocation depots so as to get the maximum benefit is a very very hard problem. Wouldn't it be nice to create a computer program that could automatically find the optimum solution?

This is very relevant to our interests.

For the Apollo missions NASA used a "carry-along" strategy, where all vehicles and resources traveled with the crew at all times. Along with the horrific propellant cost to boost all of this from Terra into LEO. For the International Space Station NASA adopted a "resupply" strategy. This also has horrific boost cost plus it requires a close resupply source (Terra).

The resupply strategy ain't a gonna work for a Mars mission (as Terra gets further and further away), so the conventional view was to use a carry-along strategy. Dr. Ishimatsu examined NASA's Mars Design Reference Architecture 5.0 (plus addendum 1 and 2).

As you know from reading this section the way to avoid the horrific boost costs is in-situ resource utilization: travel light and live off the land. The problem is figuring out what is the best placement of in-situ mining, refining, and orbital depot assets.

Dr. Ishimatsu's software determined that using lunar propellant mines and tankers would cut the cost of the conventional NASA Mars mission by a whopping 68 percent!

It is very similar to the military. The old bromide is that amateurs talk about battle tactics while professionals talk about logistics. Well, deep space exploration is going to require a well-planned logistics strategy as well.

Dr. Ishimatsu examined several prior solutions, but all either were not scaleable as the mission complexity increased, required the user to pre-define the logistics network (i.e., solve the problem manually), or were not capable of doing optimization with no human input.

Dr. Ishimatsu used Dale Arney and Alan Wilhite's technique of modeling space system architectures using graph theory. The nodes are physical locations in space wihle the arcs (connections between the nodes) are possible movements or transports between nodes. Note that arcs are one-way, an arc going from node A to node B is totally different from an arc going from node B to node A. This is because one can, for instance, use aerobraking to traverse an arc going from LEO to Terra's Surface, but one cannot use aerobraking to go from Terra's surface into LEO.

To allow for the optimal solution, it is best to include as many nodes and arcs as possible. The optimizer obviously cannot use arcs and nodes that are not present. If the optimal solution requires use of a missing node or arc, it will not be found.

One peculiarity is that you use an arc that starts and ends on the same node to model a node that is a resource processing facility. This is required in order to allow the optimizing mathematics to work. These are called a "graph-loop", "self-loop" or a "buckle".

Another peculiarity is having several arcs between a given pair of nodes. For instance, if the mission could move items between node A and node B by either chemical rockets or nuclear thermal rockes, each rocket type would have its own arc between node A and node B. This is because the two rocket types have different specific impulse and thus different propellant consumption. Additional arcs will be required for the same rocket type if it has different delta V usage choices. For instance, a nuclear thermal rocket can do either an economical burn with a long time of flight or an expensive burn were more propellant was expended in order to reduce the time of flight. There will also be an additional arc where aerocapture is possible.

Basically the multiple arcs allow the optimization to explore multiple mission choices. One choice per arc.

These multiple arcs between a given pair of nodes are called "parallel arcs."

For logistics calculation, you state the mission as a set of demands at certain nodes in the network. A demand for "plantISRU" at the LSP node corresponds to a lunar mission to transport an in-situ resource allocation industrial plant to the lunar south pole.

Dr. Arney modeled the propellant required in a mission as costs on a given arc. But Dr. Ishimatsu found it more useful to model the propellant required for all subsequent stages of the mission as payload on a given arc. In addition, since in-situ resource allocation (ISRU) allowed propellant and other resources to be generated at other nodes besides Terra, it made sense to model propellant as commodities included in the flow variables rather than as costs like Dr. Arney did. This allows formulating the problem as a multi-commodity network flow, with some commodities coming from Terra and others from ISRU sites.

The optimization problem becomes finding the best routes in the network that satisfies the mission demands while also meeting certain constraints (i.e., figuring out which nodes and arcs to use). The result will tell you "where to deploy what."

The program is trying to optimize TLMLEO, which is Total Launch Mass from Terra to Low Earth Orbit (LEO) required to set up the entire logistics network. The program is trying to find the solution with the lowest TLMLEO.

Note that there are lots of other things that could be optimized for, but this system only optimizes TLMLEO. Other things that might be optimized include:

  • Development, Test, and Evaluation cost of the various components (ISRU and orbital propellant depots will require lots of expensive R&D)
  • Number of rendezvous and refueling events (the more, the higher the chance of a malfunction or accident)
  • Complexity (the more complicated, the more potential points of failure)

For the nitty-gritty mathematical details of the optimization, please refer to Dr. Ishimatsu's thesis. It contains lots of calculus and matric algebra which makes my head hurt. There are matrix multiplications for flow equilibrium, flow transformation, and flow concurrency.

As a case study, Dr. Ishimatsu ran NASA's Mars Design Reference Architecture 5.0 through his software.

In the model, everything that travels from node to node is a "commodity", even the crew. The 20 commodities are listed in the table below. Each commodity has a flow and demand all measured in kilograms.

  • Crew
    • crew (traveling to Mars)
    • crewRe (returning to Terra)
  • Resources
    • hydrogen
    • oxygen
    • water
    • methane
    • carbonDioxide
    • food
    • waste
  • Infrastructure
    • habitat
    • plantISRU
    • sparesISRU
  • Transportation
    • vehicle
    • inertLOXLH2
    • inertLOXLCH4
    • inertNTR
    • tankLOX
    • tankLH2
    • tankLCH4
    • aeroshell

Commodity "crew" represents the crew traveling from Terra to Mars while "crewRe" represents the crew returning to Terra. A self loop on Mars transforms crew into crewRe, enforcing the rule that the mission is a round trip. This is a mathematical trick that allows the optimization math to work.

The Resources catagory includes the rocket propellants, crew provisions, and crew wastes.

The Infrastructure catagory includes habitation facilities, ISRU industrial plants, and ISRU spares.

The Transporation catagory includes vehicles, propulsive elements, and non-propulsive elements. "InertX" means "rocket engine utilizing propellant X" while "TankX" means "tank full of propellant X. The three engines are: chemical liquid oxygen + liquid hydrogen, chemical liquid oxygen + liquid methane, and nuclear thermal rocket. Note that NTR can use any of the three tanks as propellant, the others require tanks of each of their named propellants. For NASA reasons, the NTR is not allowed for lift-off or landing on a planet, and aerocapture is allowed for unmanned cargo missions but not allowed for manned missions.

Solar electric rockets were not included because they require a different way of defining the arc parameters.

For the Mars mission it requires a demand for "habitat" at GC and a demand for "crewRE" at PAC. This translates into a mission to send a crew of six and a surface habitat to Mars Gale Crater, the crew becomes crewRE (crew ready to return to Terra) on Mars after a 540 day stay, which forces a mission to send the crewRE from Mars to Terra Pacific Ocean Splashdown.

Dr. Ishimatsu used the graph below, which does show the self-loops but only shows a single arc even when parallel arcs are present. Otherwise the diagram would be an unreadable mess. The full graph has 16 nodes and 598 arcs. There are self-loops at LSP (Lunar south pole), DEIM (Deimos), PHOB (Phobos), and GC (Mars Gale Crater).

ISRU availability/technology have the folloiwng assumptions:

  • Lunar ISRU can produce O2 from regolith or H2O from water ice at a rate of 10 kilograms per year per unit plant mass while requiring spares of 10% of plant mass per year.
  • Mars ISRU can acquire CO2 from the atmosphere or H2O from water ice with the same production rate and spares requirement as those for lunar ISRU.
  • Mars CO2 can be converted into CH4 and H2O via the Sabatier reaction or can be converted into O2 via solid oxide electrolysis.
  • Electrolysis of H2O and pyrolysis of CH4 are assumed to be available along with lunar/Mars ISRU

All these chemical reactions are modeled as an optional self-loop.

First, a "baseline" problem is defined and sent through the program for a solution. This is a simplified problem whose solution will be used to measure the results of altering various parameters. Among other things the baseline problem has the propulsion system modeling simplified. For the details about the baseline problem, please refer to Dr. Ishimatsu's thesis

Dr. Ishimatsu rubs salt in the wound by cheerfully telling us "Using MATLAB 8.3 (R2014a) with CPLEX 12.6 on an Intel R CoreTM i7-2640M CPU at 2.80 GHz, one run of the optimization model takes approximately 12 seconds for preprocessing and 1.2 seconds for optimization (TLMLEO minimization)." He did a test validation by constraining the model to NASA's Mars Reference Mission, the results were practically identical.

The baseline solution has a TLMLEO of only 271.8 metric tons, a 68% savings from the NASA Mars Reference Mission NTR scenario, and a 78.3% savings from NASA's chemical/aerocapture scenario.

Then the user can alter various propulsion parameters and measure the results against the baseline solution. The other parameters and assumptions remain the same. The surprise here is that NASA's Mars Reference Mission's reliance on nuclear thermal rockets is sub-optimal. LOX/LH2 chemical engines are superior, if you include ISRU (which NASA did not). The massive amounts of oxygen and hydrogen produced by the Lunar ISRU more than makes up for the relatively low specific impulse of the chemical rocket.

The arc from Kennedy Space Center (KSC) to Low Earth Orbit (LEO) has by far highest delta V cost: 9.8 km/s. This is the mathematical way to model Heinlein's "Halfway to Anywhere" observation. The emergent property produced by optimization is the need for in-situ resource utilization.

Now the user can alter various ISRU availability scenarios and measure the results against the baseline solution. The other parameters and assumptions remain the same.

Example: Depot into Story Plot

This section has been moved here.

Solar Power Stations

Solar Power
PlanetSol Dist
☿ Mercury0.3876.6779,121
♀ Venus0.7231.9132,613
⊕ Terra1.0001.0001,366
♂ Mars1.5200.433591
⚶ Vesta2.3620.179245
⚵ Juno2.6700.140192
⚳ Ceres2.7680.131178
⚴ Pallas2.7720.130178
♃ Jupiter5.2000.03751
♄ Saturn9.5800.01115
♅ Uranus19.2000.0034
♆ Neptune30.0500.0012

Space-based solar power (aka "Powersat") is one of those concepts that make one think about idealistic hippy futurists in the 1970's drunk on the idea of MacGuffinite that is also ecological and green. It is solar energy on steroids. By placing the solar collectors in orbit you get all the solar energy since ground based solar collectors can only gather the frequencies that our atmosphere is transparent to, and are hampered by rain clouds and/or the fact that it is nighttime.

You can get almost unlimited amounts of green energy: no nasty coal, oil, natural gas, or uranium is required. Groovy, man!

The fact that none of these exist today tells you that the difficulties are overwhelming.

At Terra's orbital distance from Sol the solar power flux is abotu 1,366 watts per square meter. Due to the inverse square law the power increases the closer you get to Sol (see table). And vice versa as well.

But we do not care about such stations, since other than being a species of MacGuffinite, it has nothing to do with spacecraft, right?

Au contraire! Read on to see how solar power stations can be a boon to spacecraft.

Beamed Power

Let me take a minute to talk about solar moth rockets.

Remember the fundamental rule of rocket design: Every Gram Counts. The motivation behind the solar moth is "just imagine how much mass we could save if we eliminated the rocket engine from the design! Using the "magnifying glass incinerating an ant" principle, the solar moth utilizes a large mirror to focus the heat from the sun on the propellant, energizing it so it rushes out the exhaust bell, resulting in thrust.

It is a pity that solar energy is so diffuse around Terra's orbit. To really get worth-while amounts of heat, the solar moth will need huge mirrors. Which sort of eliminates the mass advantage of removing the engine.

That's where the powersat comes in. Have a powersat send power in a beam of microwaves and give the solar moth a microwave rectenna to receive the electrical energy! You will be using Beam-powered propulsion. The electricity can be used to heat the propellant. Suddenly your pathetically weak solar moth will be a super-powered muscle machine.


NASA’s Dr. Ernst Stuhlinger, a leading authority on electric (ion) propulsion, has often said that such a rocket system would be ideal for a manned journey to Mars.

“Yeah,” a wag once cracked, “if you can just find an extension cord long enough."


The joke is saying that electromagnetic and electrostatic propulsion systems (e.g., ion drives, VASIMR) are power hogs. Solar power arrays will have to be huge due to the low power concentration in sunlight (low as compared to the propulsion power demands). Nuclear reactors can easily supply the power but have ugly mass penalties. But the joke is on the cracking wag, beamed power is pretty much the same as an extension cord long enough.

Microwaves are difficult to focus, and the conversion from electricity to thermal energy has unavoidable inefficiencies. It would be nice to beam thermal energy instead of electrical energy. Can do: replace the microwave with a laser! Now you can use the same lightweight mirror on a solar moth, but with the much more intense radiant energy of a laser. It will be a laser thermal rocket. You can also use it on a solar sail craft and make it into a high-powered laser or photon sail. The advantage is that your delta-V capacity will be incredibly large. The disadvantage is that you are at the mercy of whoever owns the powersat.

If your laser thermal rocket is renting laser time from Beams-R-Us, you better make sure that your bill is paid up. Otherwise they will pull the plug and your rocket will suddenly be powerless, and on a one-way ticket to nowhere. You might be able to limp along using solar power instead of the laser from Beams-R-Us, but I would not bet your life on it.

And make sure you stick closely to the flight plan you filed with Beams-R-Us, or they might have a problem keeping the beam aimed at you.

Beams-R-Us might purchase their own laser thermal or laser sail ships. They will then be like a rail-road company, owning both the trains and the rails they run on.

As a matter of fact, the solar collector on the powersat will be much more effective if it was closer to the sun than Terra's orbit. Say: the orbit of Mercury. Now we're cooking!


The report Fusion Energy for Space Missions in the 21st Century had an informative analysis on a proposed beam-powered spacecraft system, tucked away in Appendix B: An Alternative Strategy for Low Specific Power Reactors Powering Interplanetary Spacecraft, Based on Exploiting Lasers and Lunar Resources.

If you are in a hurry, skip to the end of this segment to see the chart showing laser power and range.

They started by examining a standard mission to Mars, and how chemical propulsion resulted in travel times that would exceed the astronaut's career limits on radiation exposure. Cyclers (with their more massive levels of radiation shielding) were rejected as a solution because they force the round trip periods to be inconveniently long four-year cycles.

A better solution would be a more powerful rocket engine. One that was strong enough to reduce the trip time so that the radiation dosage would be acceptably low (even with the spacecraft's lower level of radiation shielding).

The analysis assumed a radiation dose limit of chronic 5 rem/year (0.05 sievert) and acute 25 rem/incident (0.25 sievert). It assumed that spacecraft radiation shielding would still result in an exposure of 0.1 rem per day (0.001 sievert). This means that the astronauts would receive 25 rems in only 0.7 year (250 days).

So the spacecraft would have to be capable of making a round trip to Mars in only 0.7 year. Of course this means the astronauts will have to retire at the end of the mission.

The report then starts looking at a 0.33 year (4 month) one-way mission. This would only result in a radiation exposure of 12 rem (0.12 sievert). It would require the engine to have a minium specific power (αp) of 10 kWe/kg (ten kilowatts of electrical power per kilogram of engine). How they arrived at that figure is a bit complicated, see the report for details.

For a 1,000 metric ton initial vehicle mass the engine would need about 129 MWe output (engine mass of 12.9 metric tons at 10 kWe/kg)

The little NASA spacecraft in the center of the diagram receives beam power from an inflatable foil mirror focused on a photocell receiver.

The inflatable foil mirror has a diameter of about 1,000 m (one kilometer!) and an areal mass of 10-2 kg/m2. A=πr2 so the mirror has a surface area of about 785,000 m2. Times the areal mass means the foil mirror has a mass of about 7,850 kilograms (7.9 metric tons).

The photocell receiver has a diameter of about 100 m and an areal mass of 1 kg/m2. 7,850 m2 and a mass of 7,850 kilograms. In case you are interested, this represents a diamond film semiconductor 100 μ thin film voltalic array along with support structure. The dark non-laser side has heat radiators to get rid of the 10 kWth/m2 waste heat (see below).

We want the mirror+photocell combo to have a specific power of 10 kWe/kg for our 4 month Mars trip.

Each square meter of photocell is fed by 100 square meters of mirror. 1 square meter of photocell has a mass of 1 kg. 100 square meters of mirror has a mass of 1 kg. So each square meter of photocell represents 1 + 1 = 2 kg worth of mirror+photocell.

So in order for the mirror+photocell to have αp=10 kWe/kg, each square meter of photocell needs to be fed 20 kW of laser light. 20 kW divided by 2 kg equals the desired 10 kW/kg.

But that is only if the photocells were 100% efficient at converting laser light into electricity. The report assumes they are actually only 70% efficient (with an ultraviolet laser beam with a wavelength between 100 and 200 nanometers). Therefore they will need 30 kW/m2 of laser light (20 × 0.70) in order for αp=10 kWe/kg. In case of emergency, the diamond film semiconductor photocell can use solar energy at about 2% efficiency. This would probably be about 0.2 kWe/m2 at Terra orbit, raw solar energy is about 1.366 kW/m2.

The inflatable foil mirror probably has an efficiency of about 90%.

Since the 30 kW of laser power fed to each square meter of photocell comes from 100 square meters of foil mirror, each square meter of foil mirror needs to feed 30,000 W / 100 = 300 W of laser light to the photocell array.

The point of all this is that the specified NASA spacecraft needs the incoming laser beam to have a power density of 300 watts per square meter and have a spot size of at least one kilometer in diameter.

Unlike the diagram above, the report is of the opinion that it makes more sense to base the laser station on Luna instead of Terra. Lack of atmosphere (so you can use laser beams in the vacuum frequencies, like ultraviolet c), and access to Lunar Helium-3 for fusion plants (though that is more or less a Chimera). And it would also work on a Solar Power Station.

Desired characteristics:

  • 100 megawatt-level high average power
  • High conversion efficiency (20% to 40%)
  • High specific power (≥1 kWe/kg)
  • Tunability to any desired wavelength (Free Electron Laser)
  • Laser intensity at emitter 100 kW/m2

You want to use a free-electron laser so the beam frequency can be tuned. This allows laser to be adjusted to wavelength optimal for the photocell receiver of that particular spacecraft.

Laser intensity at emitter 100 kW/m2 in order to balance beam losses using optical coatings with radiative cooling.

The emitter would be large, to limit diffraction losses and to allow adequate cooling (otherwise intensity becomes too many kilowatts per square meter and the emitter melts). Probably an array of thin hexagonal wafer mirrors, each supported by three computer controlled actuators. It would have an areal mass of about 40 kg/m2.

Note that these specs are for a single laser emitter that might be dedicated to a Mars mission for four months. Beams-R-Us will probably have an antenna farm full of these lasers. The more lasers, the more clients they can service simultaneously. More clients can be added by, say, having a given laser alternate boost periods between two clients. Scheduling might become tricky.

As previously mentioned, the astromilitary will be alarmed at the prospect of civilian ownership of huge batteries of ship-killing laser death-ray turrets. There might be a move to put Beams-R-Us under military control.

Given the lunar-base transmitter intensity of 100 kW/m2, and the spacecraft photocell receiver needing 30 kW/m2 of laser light, it is possible to make an equation relating the average laser power PL and the range between transmitter and receiver R. If you are going to change either of those variables the equations will need tinkering with.

Well, if you were running Beams-R-Us, you'd want to know how much energy each laser will require, and the maximum range a customer can be at, wouldn't you?

The other main variable is on the spacecraft, the ratio of the diameter of the inflatable foil mirror Dr to the diameter of the photocell receiver Df. The ratio is Dr/Df.

Dr = diameter of inflatable foil mirror
Df = diameter of photocell receiver
Dr/Df = ratio of mirror diameter to photocell diameter (10.0 in our sample ship)
R = range
λ = laser wavelength
PL = average laser power. Note in first two equations this is in watts, in third it is megawatts (200 MW in our sample ship)
3×104 W/m2 = 30 kW/m2, needed laser energy density at photovoltaic array
0.9 = efficiency of inflatable foil mirror (90%)
x1/2 = square root of x

So for the first equation:

Dr = (Dr/Df) * sqrt((4/π) * ((0.9 * PL)/(3×104)))

Dr = 10.0 * sqrt((4/π) * ((0.9 * 2×108)/(3×104)))

Dr = 870 m ≈ 1000 m diameter of inflatable foil mirror

Second equation:

Df = sqrt((4/π) * ((0.9 * PL)/(3×104)))

Df = sqrt((4/π) * ((0.9 * 2×108)/(3×104)))

Df = 87 m ≈ 100 m diameter of photocell receiver

Third equation is used to draw the chart below. Each diagonal λ line is plotted by choosing a constant value for λ then stepping along the X-axis with various values for R, using R and λ to calculate the Y-value PL

Given the requirement of a 1,000 metric ton initial vehicle mass on a Mars 4 month mission needing an engine with 129 MWe output, an inflatable foil collector with an efficiency of 90% and a photocell receiver efficiency of 70%, the required UV laser beam power is 200 MW. 129 / (0.9 * 0.7) ≈ 200 MW.

As indicated on the chart by dotted lines, the intersection of the Mars trip line and the λ=0.16 μM (UV) line is at the 200 MW average laser power point. Longer wavelengths would require a higher laser power, or several laser stations enroute to decrease the range requirement. A laser station on, say, Phobos would cut the range requirement in half. The ship would use a laser station based on Luna up to the half-way point, then switch to Phobos station.


Power beaming is clearly central to space-based solar power concepts. Here I will provide a quick overview of my understanding of power beaming, the various equations involved, typical example calculations.

If power beaming were efficient and cheap, I believe space-based solar power would be quite viable even for grid power. However it’s not, and that largely has to do with the distances involved AND the fact that you need to convert energy multiple times, with losses along the way. The distances involved aren’t a complete show-stopper, since you can solve that problem just by operating at a large enough scale. However, the conversion inefficiencies (and the need to dump waste heat, etc) is not going to go away simply by operating at greater scale (although it helps).

The first equation we need is the diffraction limit. Roughly speaking, the spot size of a transmitted beam (microwave or laser) is:

Spot size = distance-to-spot * wavelength / (aperture diameter)

This is close enough for an order-of-magnitude estimate. More detailed work to follow.

But if we have a satellite out in Geosynchronous orbit (36,000 km altitude) transmitting power at roughly 10GHz (3cm wavelength, the shortest wavelength that still penetrates readily through the atmosphere) with an antenna 300m in diameter (NRO SIGINT/ELINT satellites are rumored to be that big, but maybe only around 100m in diameter), you’d have a spot size on the order of:

3.6×107m * 3×10-2m / (3×102m) = 3.6×103m or 3.6 km in diameter

…turns out that not all the energy of your beam is contained in this diameter (“Where’s that factor of 1.22,” you cry), but that’s a halfway decent start (and you’d need an infinitely wide aperture to collect all the energy in the beam…). 3.6km is obviously huge. The biggest full-aperture dish ever built is the half-way finished Chinese Arecibo clone at 500m. Still, there are ways to tweak this.

With a laser operating at 1micron, in medium-Earth-orbit (10,000 km) with 1 meter diameter optics needs only a:

1×107m * 1×10-6m / 1m = 10m diameter receiver to receive the vast majority of the beam’s energy. This is much, much better, obviously. You could put a 10m diameter receiver on top of a tethered airship or drone or something that allows you to transmit it to the ground without interference from clouds.

Or heck, use it to power high-altitude aircraft… but that’s a whole ‘nother blog post! (And suffice it to say, there are lots of caveats about laser transmission of energy, too.)

From POWER BEAMING by Chris Stelter (2015)

8.25 Solar power satellites

     While in skeptical mode, let me say a few words about another concept of initial high appeal, the Solar Power Satellite. This was proposed in the 1960s by Peter Glaser, and like the L-5 colonies it had its heyday in the 1970s and early 1980s. Proponents of the idea believed (and believe) that it can help to solve Earth's energy problems.

     A solar power satellite, usually written as SPS, has three main components. First, a large array of photoreceptors, kilometers across, in space. Each receptor captures sunlight and turns it to electricity. The most usual proposed location is in geosynchronous orbit, though some writers prefer the Earth-Moon L-4 location. The second component is a device that converts electricity to a beam of microwave radiation and directs it toward Earth. The third component is a large array on the surface of the Earth, usually known as a rectenna, that receives the microwave radiation and turns it into electricity for distribution nationally or nternationally.

     The SPS has some great virtues. It can be placed where the Sun is almost always visible, unlike a ground-based solar power collector. It taps a power source that will continue to be steadily available for billions of years. It contributes no pollution on Earth, nor does it generate the waste heat of other power production systems. It does not depend on the availability of fossil or nuclear fuels.

     Of course, the SPS cannot be built without a powerful in-space manufacturing capability, something that is lacking today. We are having trouble putting modest structures, such as the International Space Station, into low orbit. It is likely that we will not be able to build an object as large as the proposed SPS for another century or more.

     But when a century has passed, we are likely to have much better energy-raising methods, such as controlled fusion. Admittedly, progress on fusion has been slow—we have been promised it for fifty years—but it, or some other superior method, will surely come along. A fusion plant (or, for that matter, a fission plant) in orbit would have all the advantages of SPS, and none of the disadvantages. Sunlight is a highly diffuse energy source unless you get very close to the Sun. As we pointed out in Chapter 5, the history of energy use shows a move in the direction of more compact power sources—oil is more intense and compact than water or wind, nuclear is more compact and intense than chemical. The other problem is that the Sun, unlike our future fusion reactors, was not designed to fit in with human energy uses and needs. I put the question the other way round: Why build a kilometers-wide array, delicate and cumbersome and vulnerable to micrometeor damage, when you can put the same power generating capacity into something as small as a school bus? Admittedly, we don't have controlled fusion yet—but we also can't build an SPS yet.

     However, the real killer argument is not technological, but economic. Suppose you launch SPS to serve, say, the continent of Africa. You still have the problem, who will pay for the energy? Economists distinguish two kinds of demand: real demand: the need for food of starving people with money to buy it; and other demand: the need for food of starving people without money. Regrettably, much demand for energy is in nations with no resources to pay for it.

     In spite of this economic disconnect, many people have suggested that an SPS would be great for providing energy to Africa, where energy costs are high. Suppose that you put SPS is geostationary orbit and beam down, say, 5 gigawatts. That's the power delivered by a pretty substantial fossil fuel station. Now, you could also generate that much energy by building a dam on the Congo River, where it drops sharply from Kinshasa to the Atlantic. So ask yourself which you would prefer if you were an African. Would you like SPS, providing power from a source over which you had no control at all—you couldn't even get to visit it. Or would you prefer a dam, which in spite of all its defects, sits on African soil and is at least in some sense under your control? SPS has to compete not only from an economic point of view, but from a social and political point of view.

     I think it fails on all those counts. Like the L-5 colony, SPS is part of a false future. It is not surprising to find Gerard O'Neill arguing that the sale of electricity generated by an SPS at L-5 would pay for the colony in the breathtakingly short period of twenty-four years. When we want to do something, all our assumptions are optimistic.

     There are still SPS advocates. A recent NASA study suggested that a 400 megawatt SPS could be built and launched for five billion dollars. Do I believe that number? Not in this world. We all know that paper studies often diverge widely from reality. NASA's original estimated cost to build the International Space Station was eight billion dollars. Over the years, the station has shrunk in size and the costs have risen to more than 30 billion dollars. Projects look a lot easier before you get down to doing them. Recall the euphoria for nuclear power plants in the 1940s, "electricity too cheap to meter." And that was for something we had a lot more experience with than the construction of monster space structures.

     Certainly, we hope and expect that the cost of sending material to space will go down drastically in the next few generations. We also will become increasingly unwilling to pollute the Earth with our power generation. But frequent space launches have their own effects on the environment of the upper atmosphere. If there is ever an SPS, which I doubt, it will more likely make little use of Earth materials and depend on the prior existence of a large space infrastructure.

     I feel sure that will come—eventually. By that time the idea of power generation plants near population centers will be as unacceptable as the Middle Ages habit of allowing the privy to drain into the well. However, I want to emphasize that our solutions to the problems of the future can be expected to work no better than two-hundred-year-old solutions to the problems of today. We can propose for our distant descendants our primitive technology as fixes for their problems. But I don't believe that they will listen.

From BORDERLANDS OF SCIENCE by Charles Sheffield (1999)

Power beaming stations might well be dual purpose, the space age equivalent of the military frontier posts of the American west.

The military purpose would be to protect Earth from infalling asteroids or whatever military threat develops in deep space, but they pay for themselves by beaming power to cooperative targets like friendly shipping or energy receivers mounted on NEOs. Unless there is a red alert, shipping takes priority and even if the beam is interrupted, the ships continue to coast on predictable orbits and can be picked up after the interruption is resolved (repairs made, asteroid vapourized etc.)

Life in Fort Heinlein revolves around maintaining the solar energy arrays and maintaining the tracking systems, and life will be pretty tedious. Daily routine includes system checks and battle drills, and screw-ups get to go out and polish the mirrors under the first sergeant's unforgiving gaze. A secondary economy of service providers (saloons and whorehouses) will grow around the "fort" to service the crew, and other business might set up shop as well, everything from contractor repair depots to futures traders monitoring ship traffic and energy consumption.

Lightweight ships tapping into this system have torch like performance, economy traffic might go by cycler (although the "taxis" might need torch like performance to match the cycler or slow down to orbital velocity after dropping off) and bulk traffic will still go by low cost transfer orbits.


This and similar proposals on power and propulsion generated a great deal of speculation and study in the 1970s. These activities, although generally incomplete and sometimes contradictory, identified several themes:

  • Lower cost power and propulsion is key to the development of near-Earth space.
  • Solar- and nuclear-powered lasers have the characteristics for high payoff in space applications.
  • Expensive transportation applications show high potential for cost reduction through the use of remote laser power.
  • Economical power beaming in space requires multiple customers who cannot use available (solar photovoltaic) power sources.
  • High laser conversion efficiency is a key power-beaming challenge.
  • NASA laser power requirements are very different from those of DOD and DOE, but NASA can benefit from the breadth of basic research generated by the programs of other agencies.

From the studies, then, a general set of requirements are emerging for beaming power by laser to currently envisioned space missions. First, the laser must be capable of long-term continuous operation without significant maintenance or resupply. For this reason, solar- and nuclear-powered lasers are favored. Second, the laser must supply high average power, on the order of 100 kW or greater for applications studied so far. For this reason, continuous wave or rapidly pulsed lasers are required.

Since solar energy is the most available and reliable power source in space, recent research designed to explore the feasibility of laser power transmission between spacecraft in space has focused on solar-pumped lasers. Three general laser mechanisms have been identified:

  • Photodissociation lasing driven directly by sunlight
  • Photoexcitation lasing driven directly by sunlight
  • Photoexcitation lasing driven by thermal radiation

Solar-Pumped Photodissociation Lasers

Several direct solar lasers based on photodissociation have been identified, including six organic iodide lasants that have been successfully solar pumped and emit at the iodine laser wavelength of 1.3 micrometers. (See figure 40 for a possible application of such a laser.) Another lasant, IBr, has been pumped with a flashlamp and lased at 2.7 μm with a pulsed power of hundreds of watts. One organic iodide, C3F7I, and IBr have been investigated intensively to characterize their operation. Several reports on experimental results and modeling have been published. An important characteristic of the photodissociation lasers under consideration is that they spontaneously recombine to form the lasant molecule again. Both C3F7I and IBr do this to a high degree, permitting continuous operation without resupplying lasant, as is generally required for chemical lasers. In addition, C3F7I absorbs almost no visible light and thus remains so cool that it may require no thermal radiator except the pipe that recirculates the lasant. A variety of other lasants offering increased efficiency are under study.

Solar-Pumped Photoexcitation Lasers

Another group of direct solar-pumped lasers rely on the electronic-vibrational excitation produced by sunlight to power the laser action. Two systems are being actively studied. The first is a liquid neodymium (Nd) ion laser, which absorbs throughout the visible spectrum and emits in the near-infrared at 1.06 μm. This lasant has lased with flashlamp pumping and is currently being tried with solar pumping, since calculations indicate feasibility. A second candidate of this sort is a dye laser, which absorbs in the blue-green range and emits in the red, near 0.6 μm. These lasers offer good quantum efficiency and emission that is both of short wavelength and tunable. However, the lasers require extremely high excitation to overcome their high threshold for lasing, and the feasibility of achieving this with concentrated sunlight is still a question for further research.

Indirect Photoexcitation Lasers

Photoexcitation lasers driven by thermal radiation produced by the Sun are termed indirect solar-pumped lasers. The lower pumping energy implies longer wavelength emission than with photodissociation lasers. Two lasers, the first blackbody-cavity-pumped laser and a blackbody-pumped transfer laser, work on this principle. Molecules such as CO2 and N2O have lased with emission wavelengths between 9 μm and 11 μm. These lasers are inherently continuous wave and have generated powers approaching 1 watt in initial laboratory versions, with blackbody temperatures between 1000 K and 1500 K. While such lasers, powered by solar energy, may be used in space, they also offer great potential for converting to laser energy the thermal energy generated by chemical reactions, by nuclear power, by electrical power, or by other high- temperature sources.

From LASER POWER TRANSMISSION by Edmund J. Conway. Collected in Space Resources NASA SP-509 vol 2

The laser power needed to accelerate the 82,000 ton interstellar vehicle at one percent of earth gravity was just over 1300 terawatts. As is shown in Figure 5, this was obtained from an array of 1000 laser generators orbiting around Mercury (which has 6.7 times the solar flux compared to Terra's orbit). Each laser generator used a thirty kilometer diameter lightweight reflector that collected 6.5 terawatts of sunlight and reflected into its solar-pumped laser the 1.5 terawatts of sunlight that was at the right wavelength for the laser to use.

When fed the right pumping light, the lasers were very efficient and produced 1.3 terawatts of laser light at an infrared wavelength of 1.5 microns. The output aperture of the lasers was 100 meters in diameter, so the flux that the laser mirrors had to handle was only about 12 suns. The lasers and their collectors were in sun-synchronous orbit around Mercury to keep them from being moved about by the light pressure from the intercepted sunlight and the transmitted laser beam.

The 1000 beams from the laser generators were transmitted out to the L-2 point of Mercury where they were collected, phase shifted until they were all in phase, then combined into a single coherent beam about 3.5 kilometers across. This beam was deflected from a final mirror that was tilted at 4.5 degrees above the ecliptic to match Barnard's elevation, and rotated so as to always face the direction to Barnard.

The crew to construct and maintain the laser generators were housed in the Mercury Laser Propulsion Construction, Command, and Control Center. The station was not in orbit about Mercury, but hung below the "sunhook," a large ring sail that straddled the shadow cone of Mercury about halfway up the cone.

The final transmitter lens for the laser propulsion system was a thin film of plastic net, with alternating circular zones that either were empty or covered with a thin film of plastic that caused a half-wavelength phase delay in the 1.5-micron laser light. (During the deceleration phase, when the laser frequency was tripled to produce 0.5-micron green laser light, the phase delay was three half-wavelengths.) This huge Fresnel zone plate acted as a final lens for the beam coming from Mercury. Since the focal length of the Fresnel zone plate was very long, the changes in shape or position of the billowing plastic net lens had almost no effect on the transmitted beam. The zone plate was rotated slowly to keep it stretched and an array of controllable mirrors around the periphery used the small amount of laser light that missed the lens to counteract the gravity pull of the distant Sun and keep the huge sail fixed in space along the Sun-Barnard axis.

From ROCHEWORLD by Dr. Robert E. Forward

(ed note: this is a laser thermal rocket energized by powerful lasers on an L5 colony)

     The next item on the agenda was the laser-powered high-acceleration tug, otherwise referred to as the ultra-fast optical system, UFOS having more dash and elan than LPHAT. Corporate Susan made the presentation it had worked up with Skaskash and Lady Dark.

     "The basic idea isn't bad,” said Cantrell. “How would you keep the lens oriented normal to the laser when you start to move the engine to a different orientation?"
     "We have a pair of pipes at the equator of the sphere, pumping water in opposite directions,” said Corporate Susan. “Also, inside the sphere, under the photovoltaic surface, are two pairs of circular loops, set flush with the surface and at right angles to each other. Each pair pumps water in a counterrotary direction. The pumps are all controlled, so the UFOS is gyroscopically stabilized in three planes."

     "I see,” Dornbrock said. “How do you move the engine around on the surface of the geodesic sphere?"
     "The sphere rests on this little egg cup here,” said Corporate Susan. “The egg cup is a plastic perforated surface. When we want to move, we pressurize the surface, and the geodesic sphere floats on an air cushion. Then the mechanical hands around the perimeter of the egg cup orient the engine while the sphere stays put, or the engine stays put and the hands reorient the sphere, depending on how you work the gyroscopic pumps."
     "Wouldn't you lose a lot of air pressurizing the perforated surface?” Corporate Forziati asked.
     "No, actually,” Corporate Susan replied. “We have built a little valve into each perforation which only operates when the surface is depressed by the weight of the element of the sphere in contact with it.” A diagram flashed on her telecon screen for a moment.
     "Thank you,” Forziati said. “And when you are not under thrust, weight is no problem and you don't pressurize. Very good."

     "On the other end of the egg cup,” Bogdanovitch said, “where you have the engines and the tanks for the reaction mass, you have a long cable supporting the warship. Couldn't you have the ship on an egg cup, too?"
     "No,” Corporate Susan replied. “The engines are thrusting against the geodesic sphere, which rests on top of the egg cup. The warship must keep its center of mass in line with the axis of thrust. Put it on the sphere with its own egg cup, and it would have to stay lined up with the engines—on the other side—which means the sphere would have to be built stronger, and heavier."
     "And it would get in the way of the big laser beam,” Cantrell added.

     "Then how does the warship stay out of the jet of ions?” asked Bogdanovitch.
     "It rotates at the end of its cable,” said Corporate Susan, “and makes a little circle around the jet of uranium ions which provide the main thrust. The jet of boron and hydrogen is flared off, simply to provide electrical neutrality, but it also provides a tiny bit of thrust, which can be used to offset the wobble the ship would otherwise cause by swinging around the main jet."

     "I don't understand,” Marian said.
     Corporate Susan dissolved into a diagram. “Consider the vector diagram of the force exerted by the cable supporting the ship,” said the computer. “Most of it runs through the axis of thrust, but there is a small component going at right angles to that thrust. The boron and hydrogen, flared off with the excess electrons from the decaply ionized uranium, can be adjusted to exactly balance that small component. The flare—a very soft jet—would be in the same plane as the ship, and pointing in the same direction, to push where the ship is pulling."
     "The jet—the flare, I mean, turns with the cable?” asked Marian.
     "Of course,” said Corporate Susan.

     "Orange and green,” said Marian. “Very pretty. What color is the uranium jet?"
     "Hard X-ray,” Skaskash said. “It would probably be dangerous for two or three hundred kilometers."
     "That might be an idea whose time has come,” Cantrell said at last. “Any more questions? No? Shall we build it? ... It seems to be unanimous."

     "I have a model at the shop you can use. I'll have the changes you wanted put on, and you can use that, if you want."
     "How big is it?"
     "Not big—” Ilgen stretched his arms. “Maybe a meter and a half. Did you decide what ship you wanted with it?"
     "The Alamo. We need to impress people, and the Alamo is the biggest thing we've got."
     "Right, Charlie. I'll throw in a model of the Alamo to the same scale. The UFOS plus the Alamo figures to go seven to eight times as fast as any cruiser."
     Cantrell whistled softly.
     "I'll tell the Navy,” he said. “That ought to make them very happy."

From THE PIRATES OF ROSINANTE by Alexis Gilliland (1982)

Last on my list is beamed power, which arguably does not belong in an 'early days' roundup. The usual example is a solar power satellite network beaming power down to the surface. Other uses include long-range power (probably laser) to a vehicle or satellite for propulsion and short-range power (probably RF) between a carrier satellite and payload cubesats or other small craft.

The SPS concept has been thoroughly explored over the decades. All necessary technologies exist and have been demonstrated. Environmental impact studies have been performed. The main barrier now is launch costs, which can be overcome by low-cost reusable LVs and / or the use of material harvested in space. As long as human civilization continues to use electricity there will be a market for SPS power on the surface. As the impact of human-induced climate change grows, the demand for power that does not threaten our species will continue to grow.

This kind of baseload power is further into the future but there are near-term applications. In particular, electric space tugs would benefit from a constellation of modest-sized SPS craft. Instead of carrying large solar panel arrays, a tug could carry just the rectenna and power conditioning equipment necessary to receive beamed power. This hardware would be lighter and much more resistant to radiation, allowing for a longer service life for LEO-GEO tugs. The reduced mass would make the tug more fuel-efficient, while a proper network of satellites would allow full-time operation of the tug's ion engine without requiring large battery packs. This same network of satellites could provide peak power to other assets with intermittent high power demand, particularly to a low-orbit space station that periodically does energy-intensive materials processing or uses electric engines for reboost / CAM. A further set of customers might include satellites intended only for short missions; formation flights of cubesats for example would benefit from requiring a smaller mass (and lower price) of rectenna than they would have required in solar panels.

A 'retrofit' option would be an SPS network that beams power using IR or visible lasers rather than RF. The specific frequency would be one that solar cells can efficiently convert. The SPS would simply lase the solar panels of the client craft, providing power when the sun is not available or increasing power while the craft is lit. This is significantly less efficient than RF but it would work on existing satellites and at longer ranges.


The spacecoach is a design pattern for a reusable solar electric spacecraft, previously featured on Centauri Dreams here and developed in A Design for a Reusable Water-Based Spacecraft Known as the Spacecoach (Springer Verlag), which I wrote with Alex Tolley. It primarily uses water as its propellant. This design has numerous benefits, chief among them the ability to turn consumables, ordinarily deadweight, into working mass.

The recent announcement of the Breakthrough Starshot project, which aims to use beamed power to drive ultra lightweight lightsail probes on interstellar trajectories, is of note. This same infrastructure could be used to augment the capabilities and range of spacecoaches (or any solar electric spacecraft), while providing a near-term use for beamed power infrastructure as it is developed and scaled up.

The spacecoach design pattern combines a medium sized solar array (sized to generate between 500 kilowatts and 2 megawatts of peak power at 1AU) with electric propulsion units that use water as propellant (and possibly also waste streams such as carbon dioxide, ammonia, etc). We found that, even when constrained to these power levels, they could fly approximately Hohmann trajectories to and from destinations in the inner solar system. Because consumables are converted into propellant, this reduces mass budgets by an order of magnitude, and effectively eliminates the need for an external interplanetary stage, all while greatly simplifying the logistics of supporting a sizeable crew for long duration missions (more consumables = more propellant).


The primary constraint for space coaches, especially if you want to travel to the outer solar system, is available power. This is an issue for two reasons. First, solar flux drops off by 1/r2, so at Jupiter, a solar array will generate roughly 1/25th the power as it does at Earth distance. Second, trips to more distant locations will typically require a greater delta V (and thus higher exhaust velocity to achieve this with a given amount of propellant). The amount of energy required to generate a unit of impulse scales linearly with exhaust velocity, so the net result is the ship’s power requirements are increased, all while the powerplant’s power density (watts per kilogram of solar array) is decreased.

Testing Beamed Power

Beamed power infrastructure would enable space coaches and solar electric spacecraft in general to operate at higher power levels for a given array size, which would enable them to operate at higher thrust levels, and to utilize higher exhaust velocities to maximize delta V and propellant efficiency. This means they would be able to accelerate faster, achieve higher delta-v, while using less propellant. In effect beamed power to SEP spacecraft will give their operators the equivalent of a nuclear electric power plant (without the nukes).

A spacecoach built for solar only operation would be able to serve as a testbed for beamed power. For example, a space coach departing Earth orbit could be illuminated with a beam that increases its power output by a small amount, say 10% (large enough to make a measurable difference in performance, yet small enough that major modifications are not required to the ship as it just experiences slightly brighter illumination while in beam). At higher light levels, this technique could also be used to simulate lighting and heat loading conditions expected at the inner planets while remaining in near Earth space. Note also that lasers can be tuned to the absorption wavelength(s) of the photovoltaic material, greatly improving conversion efficiency (and reducing heat gain per unit of power delivered). An even cheaper way to build out and test power beaming infrastructure will be with satellites and probes that utilize solar electric propulsion.

The pathway to a system based primarily on beamed power then becomes one based on incremental improvements, both for the ground based facilities and for the ships. This would result in near term applications for the beamed power facilities while the much more technically challenging aspects of the starshot project are sorted out. Meanwhile, satellite and space coach operators could test ships with ever higher levels of beamed power until they hit a limit (heat rejection is probably the main limit to how much power can be concentrated per unit of sail area, as this is similar to concentrated photovoltaics).

The chart below illustrates the power/performance curve by showing the amount of impulse that can theoretically be generated per megawatt hour using electric propulsion, as a function of exhaust velocity. Real world performance will be somewhat lower due to efficiency losses, but this shows the relationship between thrust, ve and power. We see that impulse per MWh varies from 72,000 kg-m/s (ion drive, ve ~ 100,000 m/s) to 1,400,000 kg-m/s (RF arcjet, ve ~ 5000 m/s). A Hall Effect thruster, a flight proven technology, would yield about 300,000 kg-m/s per MWh. Compare this to pure photonic propulsion, which would yield only 12 to 24 kg-m/s per MWh. Clearly photonic propulsion will be necessary to achieve a delta v of 0.2c, but for more pedestrian applications such as satellite orbit raising, launching interplanetary probes or cargo ships from LEO to BEO (beyond earth orbit), electric propulsion will work well at power levels many orders of magnitude lower than what’s required for a starshot.


Driver for an Interplanetary Infrastructure?

Closer to home there could be lots of opportunities to sell beamed power to space operators. It’s costly to launch large payloads beyond low earth orbit (which isn’t cheap in the first place). Meanwhile, payload fairings limit the size of self-deploying solar arrays, which limits the use of electric propulsion for satellites and probes. If one could launch spacecraft with small solar arrays to LEO, and then use beamed power to amplify their power budget they could use electric propulsion to boost themselves to their desired orbits or interplanetary trajectories within a reasonable time frame. The beamed power infrastructure can also be built up incrementally. Early systems would beam 100 kilowatts to 10 megawatts of power to targets measuring meters to tens of meters in diameter. This should be readily achievable, and can be scaled up from there in terms of power output, beam precision, etc. The result: lower costs per kilogram to deliver a payload to its destination or desired orbit compared to all chemical propulsion.

This could make electric propulsion for transit from LEO to GEO and beyond an attractive option. Meanwhile, the power beaming operator would accrue lots of operational experience with beam shaping, tracking objects in orbit, etc, all things that will need to be mastered for the starshot project, while providing an economic foundation for the power beaming facilities during the buildup to their intended purpose.

In fact, one can imagine the starshot project becoming a profitable LEO to BEO (beyond earth orbit) launch operator in its own right. The terrestrial power beaming infrastructure is one component. A standardized “power sail” that can be fitted to many different payloads, from geostationary satellites to interplanetary probes, is another. The power sail would consist of a self-deploying solar array that is sized to work well with beamed power, heat rejection gear, and electric propulsion units. It would use beamed power during its boost phase to rapidly accrue velocity for its planned trajectory, and then as it leaves near Earth space, would transition to use ambient light as its power source from there. Meanwhile these power sails would provide an evolutionary path from conventional spacecraft to solar electric propulsion to the nanocraft envisioned for purely photonic propulsion.

As a starting point, it would be interesting to conduct ground based vacuum chamber tests to see how a variety of PV materials respond to being illuminated with concentrated laser light tuned to their peak absorption wavelengths. What do the conversion efficiencies look like? How much waste heat is generated? How do the materials perform at high temperatures in simulated in-beam conditions? Building on that one can imagine experiments involving cubesats to validate the data from those experiments in real world conditions, and if that all works out, one could scale up from there to build out beamed power infrastructure for use by many types of solar electric vehicles.

Ambitious R&D projects have a way of generating unintended side benefits. It’s possible that the starshot initiative, in addition to being our first step toward the stars, will also make great contributions to travel and exploration within the solar system.

From SPACECOACHES AND BEAMED POWER by Brian McConnell (2016)

Powersat Weapons

About this point all but the hopelessly dull are thinking "wait just a darned minute, what are the military applications?" Pretty good, actually. Have you ever heard of a Laser Combat Mirror? The laser-propulsion mirror eliminates most of the mass of the engine, the laser combat mirror eliminates most of the mass of a laser cannon. This will free up payload mass in the space warship so it can carry more of other kinds of weapons.

As the range increases the powersat beam rapidly becomes too diffuse to do damage due to diffraction. But a warship sporting a laser combat mirror can focus the seemingly harmless diffuse beam into an eye-searing ship-destroying pin-point. Again much in the same way that sunlight is too diffuse to harm ants, unless a naughty boy uses a magnifying glass to focus it into an ant-destroying death ray.

Powersat's weapon potential is so effective that they will probably be nationalized, removed from civilian hands, and turned over to the military.

And even without a fleet of warships with laser combat mirrors, a powersat all alone is a pretty fair orbital laser weapon. Without laser combat mirrors the range is limited, but within that range, whoo boy can they vaporize the heck out of enemy spacecraft, space assets, and even torch ground targets. Their huge solar panels make them fragile, but they can do plenty of damage before they are neutralized.

Not quite green ecological hippy anymore, is it?


G. Harry Stine's (writing as Lee Correy) wrote a rocketpunk novel called Manna. In the novel, the military branches of the space-faring nations would like to put five gigawatt High Energy Laser (HEL) satellites in orbit. Using fancy techniques they are powerful enough to get their weapon laser beam through Terra's atmosphere and incinerate targets on the ground.

The trouble is the militaries want the HEL beamer satellites to be stealthy. The root of the trouble is that a five gigawatt HEL beamer containing a +five gigawatt power source is about as stealthy as a New York 4th of July fireworks display.

If only the power source could be at some distance from the HEL beamer, sending the energy by electromagnetic waves. You know, the same way a powersat sends microwave energy to ground power stations... hmmmmmmm.

That would work, the HEL beamers could be stealthy little dastards with no nuclear power plant, but rapidly unfurling a powersat reception antenna when it came time to zap something.

Now comes a bigger problem. Nobody can build any powerstats.

Why? Well, no corporation is going to embark upon a multi-billion dollar project like a powersat without insurance. And no insurance company is going to underwrite a multi-billion dollar installation which becomes a military target the instant it redirects its power beam from a power station in order to energize a HEL beamer. Especially a military target so huge, easy to hit, and incredibly fragile as a powersat.


How to solve the problem? Well, since it is an insurance problem, there should be an insurance solution.

Through a series of international agreements, the Resident Inspection Organization (RIO) was formed. This international group regularly inspected all powersats, and insured that they stayed pointed at ground power stations. In exchange, the insurance companies would underwrite the powerstats. If any powersat started to energize something that might be a stealthed HEL beamer, RIO would sound the alarm to all the astromilitaries, presumable giving the military units enough time to blow the living snot out of the powersat.

Naturally the astromilitary of Nation Alfa would be angry at RIO squealing when astromilitary Alfa tried to energize one of their HEL beamers. But astromilitary Alfa would be vary grateful if RIO squealed about astromilitary Bravo, Charlie, Delta or Echo doing the same thing.

     "I'm worried about RIO's reaction," Captain Kevin Graham remarked from the space port. "Our captains are concerned that PowerSat, InPowSat, and InSolSat powersats could have their power beams diverted to the American beam weapon stations on orbit . . . and we know where every one of them is stationed even though the Aerospace Force tried to hide them in inclined Clarke orbits."
     That was Top Secret information! How had the League of Free Traders found these battle stations, shrouded as they were with hard stealth technology?
     Ursila Peri reported from L-5, "I don't know if the powersat crews would carry out an order to redirect power beams to military battle stations. Whether the Aerospace Force has plans for a military takeover of the powersats is another matter, but such an attempt would put them in confrontation with the RIO teams on the powersats."...
     ...Vaivan went on, "Sandy, energy war isn't difficult to understand. Most low-tech countries will continue to do business with us in spite of any embargo or boycott. We provide value received and take very little off the top. The Tripartite may try to invoke sanctions against our customers by pulling their powersat plugs, but we'll be there with another plug. And we have a space port, space lift capability, primary metals and plastics industries, and the lunar mine and smelter at Criswell Center. You haven't see that yet, but it's just a lunar mine and smelter. Commonwealth Glaser's capable of supplying powersat electricity to anyone the Tripartite cuts off because they're now building powersats with lunar materials at a much faster rate than the Tripartite companies."
     "They'll react," I warned.
     "They'll go after your powersats."
     "In the face of international law and the Resident Inspection Organization? The insurance trusts won't stand for it," Wahak maintained. "Those trusts are controlled by the Tripartite, but not even a consortium of all the Tripartite banks could possibly cover the insurance losses. And there won't be any because the insurance trusts will place a rather strong damper on any military powersat takeovers. Then RIO will drive in the bung."
     "RIO teams are un-armed," I reminded him.
     "We'll see what happens when everybody shows their cards. RIO will have to become the first Space Patrol whether they want to or not because circumstances will force it ... and so will we."...
     ..."How much capacity has been dropped off the powersat net?" Ali tried to get back on track.
     "Fourteen gigawatts," Shaiko reported. "The cut-offs in­volved split beams, so no powersat is totally off-line, but One-Zero-Five-East and Six-Zero-East have near-zero loads."
     I didn't like that. "Which powersats will have near-zero if they pull the plug on Annom, Nireg, and Sorat?" I asked.
     Shaiko consulted a nearby display before replying, "Two-Zero-East and One-Zero-Five-East."
     "That drops One-Zero-Five-East down to zilch, doesn't it?" I observed.
     "Any load left on One-Zero-Five-East if Annom and Sorat go off?"
     "What are you worried about, Sandy?" It was Vaivan who caught my concern.
     "A ten gigawatt powersat can pump a big laser, Vaivan," I explained. "A high-energy laser—they're called hell beamers from their acronym, H-E-L—is limited in beam power density and range only by its energy source. If it's a self-contained unit, the space facility is large and vulnerable. But if a hell-beamer's energized remotely, it's small and hard to identify. Powersat One-Zero-Five-East could put its ten gigawatts into a hydrogen-fluoride hell-beam station to punch a beam right down to surface from GEO!"
     This was obviously news to them. Rayo Vamori broke the silence, "Is there a battle station over us?"
     "The Aerospace Force has them over all parts of the world in sixty-degree inclined geosynchronous orbits. Kevin Graham's captains have spotted them."
     Ali said slowly, "I'd better pay Peter Rutledge a visit."
     I went with Ali to the Resident Inspection Organization's headquarters, GEO Base Zero. Ali needed a pilot, and he wanted me to meet those upon whom the delicate stability of space power depended.
     I'd never known any RIO people. They kept to themselves as an anational paramilitary organization with a tradition of non-involvement. They had to be aloof. Thanks to RIO, there hadn't been a conflict in space since the Sino-Soviet Incident.
     Ali wanted to make certain that RIO knew what was happening with the powersats. He was also covering his anatomy by insuring that Powersat One-Zero-Five-East or any other powersat didn't get its power beam redirected to a hell-beamer.
     The approach to RIO Headquarters was a two-man job. The first challenge from RIO came at a thousand kilometers. We answered with the proper transponder code. Then we had to close at no more than ten meters per second, matching orbits and station-keeping ten klicks behind at zero closure rate. There we were thoroughly scanned. Once we proved we were sweet, pure, and unrefined as well as incapable of swatting a bee in revenge for being stung, they put a RIO pilot aboard. She strapped into the jump seat between Ali and me and flew the ship. It was rather disturbing to sit next to someone wearing about twenty kilos of Comp-X around her waist. From her accent as she reported on her comm set to RIO Approach, she was Japanese. I knew she wouldn't hesitate to self-destruct and take the ship and the two of us with her if we tried to ram GEO Base Zero...
     ..."He had to be. How much do you know about RIO and how it's run, Sandy?"
     "Only what I've read, which was reasonably extensive be­cause the Academy wanted future officers to understand RIO not as an adversary, but as a potential obstacle."
     The Resident Inspection Organization had been the factor which permitted the powersat network. Without non-national or international inspection, who was to know whether or not a powersat also contained a hell-beamer? Who could have ascer­tained whether or not an attack satellite was hidden in the structures of the photovoltaic panels? And who'd be sure that the power beam wouldn't be diverted—as Ali and I now feared— from the ground rectenna to an otherwise passive and silent hell-beamer satellite? Could someone really pirate the pilot beam that kept the power beam phased on the rectenna and then concentrate several power beams on an Earth or space target, even though the power density of a single powersat beam is only one-fifteenth that of a microwave oven?
     These questions left unanswered posed a military threat which in turn made a powersat a military target because nobody could take chances if an armed conflict appeared imminent.
     A powersat is a terribly vulnerable thing—square kilometers of solar panels and bus bars carrying megawatts of power. No businessman, entrepreneur, financier, banker, or investor would have risked a worn penny on a powersat that was a certain target in the opening moments of any future war. Neither Lloyd's nor Macao's would or could have underwritten the insurance re­quired for the long-term financing.
     Obviously, a non-political international inspection organization was required. But how could it be organized, financed, and operated to insure that it remained non-national? That had been an enormous problem.
     But technology always creates the new social organizations necessary to finance, manage, and control it.
     People hacked away at the problem until RIO was organized at the Hartford Convention. RIO was formed with the funding from the groups who'd lose the most if a powersat were attacked as a military target, whether it was an actual threat or not. The damage or destruction of a multi-billion dollar powersat would be an expensive loss to the insurance underwriters.
     The world needed space power and the insurance consortiums were the critical bottleneck. Whether or not there were economic pressures applied is a moot point today because the fraction of a percent that was tagged onto the kilowatt-hour consumer electric bill amounted to billions of dollars in insurance premiums which in turn more than paid for the 2,000 RIO inspectors and specialists with their independent communications and transportation systems.
     Rutledge had been accurate in using the sentry as the analogy for RIO.
     A lot of people didn't understand that an unarmed RIO was considered to be very effective. If a resident team or one of the ubiquitous spot inspection teams under the command of Rutledge found something unusual, there were two options open to the team leader: (a) report it covertly to RIO Headquarters for evaluation there; or (b) in a real emergency communicate the military activity to everybody. In the latter case, it was then important for RIO to get out of the line of fire.
     Because of its unique anational character and novel operational methods, RIO often acted in strange and unfathomable ways. Unarmed as they were, they posed no military threat to |anyone. But the threat of their capability to saturate the comm/info network with the danger cry of the watch dog was a sure and certain restraint on military space activities. I suspected—and knew in some cases—that RIO had intelligence operations which penetrated deeply into nearly every military organization in the world. It wouldn't have surprised me, either, if their intelligence activities also embraced the world of commerce.
     A lot of military planners had spent a lot of time and effort drafting plans and programs for circumventing RIO. The Aerospace Force—whose job was ostensibly to keep and guard the peace, too—had a continual highly-classified think-tank activity going on "should it be necessary to activate such plans and programs." But the job of any military service is to ensure the security of its nation...

From MANNA by G. Harry Stine (1983)

Tether Propulsion


A momentum exchange tether is a kind of space tether that can be used as a launch system, or to change spacecraft orbits. Momentum exchange tethers create a controlled force on the end-masses of the system due to centrifugal acceleration. While the tether system rotates, the objects on either end of the tether will experience continuous acceleration; the magnitude of the acceleration depends on the length of the tether and the rotation rate. Momentum exchange occurs when an end body is released during the rotation. The transfer of momentum to the released object will cause the rotating tether to lose energy, and thus lose velocity and altitude. However, using electrodynamic tether thrusting, or ion propulsion the system can then re-boost itself with little or no expenditure of consumable reaction mass.

A non-rotating tether is a rotating tether that rotates exactly once per orbit so that it always has a vertical orientation relative to the parent body. A spacecraft arriving at the lower end of this tether, or departing from the upper end, will take momentum from the tether, while a spacecraft departing from the lower end of the tether, or arriving at the upper end, will add momentum to the tether.

From the Wikipedia entry for MOMENTUM EXCHANGE TETHER

A good low-mass way to prevent cables from failing catastrophically is to use Hoytethers (cables that are elongated Hoytubes). Strengthening a cable by increasing its diameter quickly becomes too expensive in terms of mass. A Hoytether on the other hand is a low mass network of redundant cables that fails gracefully.

Momentum exchange Hoytethers were featured in the novel Saturn Rukh by Robert L. Forward.


A momentum exchange tether is a long thin cable used to couple two objects in space together so that one transfers momentum and energy to the other. A tether is deployed by pushing one object up or down from the other. Once the two objects are separated by enough distance, the difference in the gravitational force at the two locations will cause the objects to be "pulled" apart. This is called the "gravity gradient force". The tether can then be let out at a controlled rate, pulled by the tension caused by the gravity gradient force. Once the tether is deployed, if there are no other forces on the tether it will have an equilibrium orientation that is aligned vertically. There are a number of different concepts for momentum exchange using tethers. Some general categories are:

A bolo is a long rotating cable anywhere in space that is used as a "momentum-energy bank". It could be used to "catch" a payload coming from any given direction (in its plane of rotation) at any given speed (less than its maximum tip speed), and then some time later, "launch" the payload off in some other direction at some other speed. A gravity gradient stabilized bolo orbiting some planet has the property that if the tether is cut, then one-half an orbit later, the separation distance between the two masses is seven times larger than the initial separation. This can be used to deorbit the lower mass, or throw the upper mass to a rendezvous or to escape.

(ed note: momentum-energy bank is just like a financial bank, only using momentum instead of money. You can put momentum in by catching a spacecraft and take momentum out by launching a spacecraft, but the important point is you cannot take out more momentum than the blasted bank currently contains. This means you need a strategy to balance deposits and withdrawals of momentum.

The most common strategy is to have two bolos, for example one at Terra orbit and one at Mars orbit. Each bolo lobs payload modules at the other, and catches modules aimed at them. This keeps the momenum balanced.)

Tip Velocity and Material Strength

The maximum tip speed of all these systems is a function of the "launcher to payload mass ratio" of the tether system and the "characteristic velocity" of the material used. The characteristic velocity of the material in a tether is given by the square root of the ratio of the design tensile strength T of the tether to the density D of the tether material. u = (T_d/D)^1/2. In practice, the design tensile strength is usually chosen to be 50% of the measured strength for metals and 25% of the measured short-term individual fiber strength for other materials. Thus, using imperfect materials with reasonable safety margins, the characteristic velocity of most metals and fibers is around 1 km/s, with optimistic predictions for graphite and improved polymers reaching 3 km/s. With the development of a design for a high strength-to-weight tapered Hoytether, the design tensile strength can be safely chosen to be 60% of the measured strength of the individual fibers, allowing commercially available fibers to have characteristic velocities up to 4 km/s.


     "Just the general idea. It starts with the Spider again. Now it's spinning a different kind of web. Rockets are wrong. That's sitting there in your desk as we talk, but I didn't follow it far enough. I should have known you wouldn't stop with the beanstalk, that just gets us up and down from Earth. You wanted a way of moving materials around the whole System without using drives. And the Spider could give you that."...
     ..."Spin another cable," he went on. "Make it like the beanstalk, with superconducting cables and drive train attached to the load cable. This time, put the powersat at the center of the cable, with an equal length on each side of it. Fabricate it in space, but don't ever plan to fly it in and tether it. Leave it out near the orbit of Mars, or in the Belt, or in near Earth—key places in the System. Then start it rotating about its center, like a couple of spokes on a wheel. I assume that you began with just a couple of them, one in the Belt and one near Earth?"
     Regulo nodded calmly. He had finished fiddling with the control panel and now seemed oddly relaxed. "We started with two. That's just the beginning. The more you have, the better the efficiency of the whole operation. I've been thinking we'd build about five thousand of them through the Earth-Belt region."
     "You could handle that many?"
     "With Sycorax? Easily. We can track that number, and more—there are millions of orbits in the data banks already. This is just a few extra ones." Regulo's tone was that of a patient teacher. "I've told you before, Rob," he went on. "Think big. The System's a big place. You have to scale your thinking to match it."...
     ..."Just as you did. You have a rotating cable out in a free orbit—thousands of kilometers of it." He leaned forward, at the same time as Regulo moved his chair farther away from the desk.
     "Now suppose you want to move a space pod from the Belt to the Moon," Rob went on. "You make it rendezvous with the center of the cable, where the powersat sits. The center of mass of the cable would be moving in a free-fall orbit, travelling about the same speed as the pod, so you use hardly any reaction mass to make the rendezvous. You don't need much acceleration from the pod's drives, either, just a fraction of a gee will be enough. Once you have the pod at the middle of the cable, you let it move out along the drive train. As the pod moves from the center it feels a centripetal acceleration. You need to use the drive train on the cable to restrain it. When it reaches the end of the cable, you release it to move in free fall. You've given it a big velocity boost. But the trouble from the point of view of a human on the pod is the acceleration. Out at the end of the cable, it's huge. I looked at a couple of examples. A cable four thousand kilometers long, with end velocity of twenty-four kilometers a second, would give thirty gees at each end. That's what killed the Goblins."...
     ...He put the space pod to a cable rendezvous with a cargo Slingshot—one with high accelerations, never intended for people."
     "Do you have Slingshots for passengers?" Rob moved forward right up to the desk.
     "We built the first two, just a month ago. I could find out which cable your Goblins used easily enough, by checking the angular momentum of all of them. Each time we use a Slingshot we naturally increase or decrease its angular momentum." Regulo stood up, his back to the wall. "We lose angular momentum when we throw a cargo in toward the Sun, and pick it up when we catch something thrown in from Mars or the Belt. Provided we move the same mass of materials in and out, the whole system balances—just like the beanstalk back on Earth.

From THE WEB BETWEEN THE WORLDS by Charles Sheffield (1979)
     My post Orbital Momentum as a Commodity describes how a tether with a healthy anchor mass can catch and throw payloads. I tried to think of ways a tether might restore orbital momentum lost during a catch or throw. Two way traffic is one way to pay back borrowed momentum.

     Well, Mars' moon Phobos masses 1.066×1016 kg. With this huge momentum bank, catching and throwing payloads would have less effect than a gnat hitching a ride on a Mack truck. A Phobos anchored tether could catch and throw for millennia with little effect on Phobos' orbit.

     The tether illustrated above doesn't suffer the enormous stress of a full blown earth elevator or even a Mars elevator. It could be made from Kevlar with a taper ratio of about 11.

Access to Mars

     The tether foot pictured above moves about 0.6 km/s with regard to Mars surface. This is about 1/10 of the ~6 km/s the typical lander from earth needs to shed. Mars Entry Descent and Landing (EDL) would be vastly less difficult.

     Some have suggested Phobos 1.88 g/cm3 density indicates volatile ices. If so, the moon could also be used as a source of propellent. A Phobos propellent source would make EDL even less of a problem. However Phobos' low density might also be due to voids within a rubble pile.

     On page 2 of the Acceleration of the Human Exploration of The Solar System with Space Elevators Asteroid Initiatives founder Marshall Eubanks takes a look at how the foot of Phobos-Anchored Martian Space Elevator (PAMSE) might interact with Mars' atmosphere:
     The orbital eccentricity of Phobos amounts to 283 km, which is by coincidence comparable to the effective depth of the Martian atmosphere for satellite drag (typically ~ 170 km, but subject to variations due to atmospheric events such as dust storms). The average relative velocity between the lower tip and the surface of Mars is only 534 m/sec, roughly Mach 2 in the cold Martian atmosphere, and slow enough that it should not cause significant heating of the tip. This raises the interesting possibility that the PASME tip could dip down deep into the atmosphere to leave or recover payloads or perform reconnaissance, acting as a supersonic airplane for the period near periapse when it is near the surface.
     Eubanks' 534 m/sec is a little slower than the 0.6 km/s of my tether tip. This might be because I had placed my tether tip 300 km/s above Mars' surface thinking atmospheric friction would destroy a lower tether foot. Eubanks' analysis has changed my view.

     In the Facebook Asteroid Mining Group, Eubanks noted:
     The orbit of Phobos is equatorial, and there is a big mountain in the way, Pavonis Mons, the middle of the Tharsis volcanoes, straddling the equator and by far the highest obstacle in the path of the elevator tip. Maybe a railroad on top of the volcano could match speeds with the elevator tip, once every 3 days or so (when the orbit and volcano aligned). If so, you would have up to 3 minutes to shift cargo on and off. 
     as well as
     …the cool thing is that the tip can be something like a tethered airplane (with wings and flaps, etc.) and you should be able to use that to control oscillations. I was hoping to get money to begin actually "testing" this (i. e. in simulation), but, alas, not so far. 
     Remember, too, with the PAMSE the counterweight has ~ infinite mass, and so any oscillations have to end there. (of course, anchoring a PAMSE in Phobos is left as an exercise for the reader.)
     If Phobos is indeed a loose rubble pile, anchoring the elevator would be difficult. So while Eubanks eased my anxieties on oscillations and atmospheric friction, he calls my attention to a problem I hadn't thought of.

Access to Earth

     6155 km above Phobos the tether is moving faster than escape velocity with a Vinf of 2.65 km/s. This is sufficient to toss a payload down to a 1 A.U. perihelion. This could provide most of the delta V for Trans Earth Insertion.

     A ship coming from Earth would have a Vinf of 2.65 km/s and so rendezvous with this part of the tether might be accomplished with little propellent.

Access to the Main Belt

     7980 km above Phobos the elevator is moving with a Vinf of 3.27 km/s, enough to hurl payloads to a 2.77 A.U. aphelion. This part of the tether might send/receive payloads to/from the Main Belt. There are a lot of asteroids with healthy inclination, though. So there would be substantial plane change expense at times.

Possible Mars exports to the main belt

     One thing about the Main Belt, the pace is much more leisurely. Ceres moves about 1º every 5 days. In contrast earth moves about 1° a day and a satellite in low earth orbit moves about 4° a minute.

     So a month-long, low-thrust ion burn over there looks a lot more like an impulsive burn than it does in our neck of the woods. I believe high ISP ion engines are well suited for travel about the Main Belt.

     The inert gas argon can be used as reaction mass for ion thrusters. Mars' atmosphere is about 2% argon. It is also about 2% nitrogen and 96% carbon dioxide with traces of oxygen and water. Mars also has respectable slabs of water ice at the poles.

     Mars would be a good source of propellent for the entire belt as well as CHON for the volatile poor asteroids in the inner main belt.

     Ion engines don't have the thrust to weight ratio to soft land on the larger asteroids. But asteroids often have high angular velocity (in other words, they spin fast). High angular velocity combined with shallow gravity wells make asteroids amenable to elevators.

     For example the balance point for a Ceres elevator would only be 706 km above Ceres surface, that is the altitude of a Ceres-synchronous orbit. To provide enough tension to remain erect, the elevator would need to extend to an altitude of 2000 km. At 2000 km, the tether tip is moving about 0.46 km/s, a good fraction of the 2.82 km/s needed fro Trans Mars insertion. If this Ceres elevator is Kevlar, taper ratio would be about 1.02.

     If extended to an altitude of 14,500 km, the Ceres elevator top would be moving fast enough for Trans Mars insertion. This would require a taper ratio of around 5 for a Kevlar tether.

Incremental Development

     The tether pictured at the top of this post is ~14,000 km long with a taper ratio of 11 for Kevlar. While much smaller than a full blown Mars elevator, this elevator would still be a massive undertaking. But the whole thing doesn't need to be built overnight. Early stages of the elevator would still be useful.

     Pictured above a Deimos tether drops a payload to a Phobos tether.

     At apoapsis of the large ellipse, payload velocity matches the Deimos tether foot. At periapsis, the velocity matches the speed of the Phobos tether top. Thus payloads can be exchanged between these Martian moons using practically zero reaction mass.

     After descending the Phobos tether, the payload can be dropped to a Mars atmosphere grazing orbit.

     These tethers are a lot shorter than 14,000 km tether we were talking about and taper ratio is close to 1.

No Moons to Dodge

     A full blown Mars elevator capable of throwing payloads to the Main Belt or even earthward would have to dodge Deimos as well as Phobos.

     A Phobos elevator for flinging payloads to Ceres ends well below Deimos' orbit. And of course a Phobos anchored tether doesn't need to dodge Phobos.


     Tsiolkovsky's rocket equation and big delta V budgets are touted as show stoppers for routine travel to Mars' surface or the Main Belt.

     With judicious use of tethers and orbital momentum, rhinoceros sized delta V budgets are shrunk to hamster sized delta V budgets. No bucky tubes needed, ordinary materials like Kevlar can do the job.

Inert Cargo Vessels

If you were shipping asteroid ore (actually "ore" is not quite the right word but there isn't a good one) from Ceres to Terra (or manufactured goods going the other way), well, the cargo is going to take a bit more than 15 months for the trip. Which is a long time for the cargo spacecraft to be idle, doing nothing but surrounding the cargo. It is hard to amortize the cost of the spacecraft and spacecraft maintenance when it is only doing billable work at the start and end of the trip while the engines are burning.

A few innovative thinkers had the bright idea that since the expensive engines (specifically the propulsion bus) are only needed at the start and end of the journey, why not jettison them so they can be reused?

In the first scheme the propulsion bus becomes a space tug. This latches onto a cargo container, pushes (or pulls) the container into the desired trajectory, detaches to let the cargo go on its merry way, then the tug flies back to the cargo staging area for a propellant re-fill and to grab the next scheduled cargo cannister.

The cargo cannister flies in its trajectory, with no engine but no need for an engine either.

15 months later the launched cannister approaches Terra where it is intercepted by a Terran space tug. It then decelerates into the cargo storage orbit, parks the cargo, refills, and heads out to catch the next incoming cargo cannister.

Since the tugs are constantly working they can amortize their little hearts out.

If the delta-V requirement for the trajectory is not too excessive, the pair of space tugs can be replaced by a pair of momentum exchange tethers ping-ponging momentum energy back and forth between each other as they launch and catch cargo cannisters. With this scheme it is important that each tether in the pair launches the same amount of mass that they catch. Otherwise one or the other tether will start running out of energy and will have to be spun up again with solar power or something.

Again these are are constantly working and constantly amortizing.

Back in 1976 visionary Gerard K. O'Neill had a similar concept for use in the construction of his O'Neill cylinder L5 space colonies. Their isn't enough money in the entire world to boost the required million metric tons or so of construction into orbit. Therefore O'Neill designed a lunar mining base which would dig up the required materials, catapult them into cis-Lunar space with a huge Mass drivers, and when a given load approached the L2 point it would be intercepted by a huge net-like construct picturesquely named a "catcher."

Some mass driver designs have the masses of ore encased in ferromagnetic cannisters to give the mass driver's magnetic field something to grab. Others need no cannisters, instead they use ferromagnetic buckets which are halted and returned to be reused at the end of the mass driver. The ore goes flying into space toward the catcher. This saves on cargo cannisters cost.

The cargo modules will probably be sized to be compatible with standard cargo cannister form factors.


      The observation bubble on the side of the Cay Habitat had a televiewer, Leo discovered to his delight, and furthermore it was unoccupied at the moment. His own quarters lacked a viewport. He slipped within. His schedule allowed this one free day to recover from trip fatigue and jump lag before his course was to begin.

     The curve of Rodeo’s horizon bisected the view from the bubble, and beyond it the vast sweep of stars. Just now one of Rodeo’s little mice moons crept across the panorama. A glint above the horizon caught Leo’s eye.

     He adjusted the televiewer for a close-up. A GalacTech shuttle was bringing up one of the giant cargo pods, refined petrochemicals or bulk plastics bound for petroleum-depleted Earth perhaps. A collection of similar pods floated in orbit. Leo counted. One, two, three … six, and the one arriving made seven. Two or three little manned pushers were already starting to bundle the pods, to be locked together and attached to one of the big orbit-breaking thruster units.

     Once grouped and attached to their thruster, the pods would be aimed toward the distant wormhole exit point that gave access to Rodeo local space. Velocity and direction imparted, the thruster would detach and return to Rodeo orbit for the next load. The unmanned pod bundle would continue on its slow, cheap way to its target, one of a long train stretching from Rodeo to the anomaly in space that was the jump point.

     Once there, the cargo pods would be captured and decelerated by a similar thruster, and positioned for the jump. Then the superjumpers would take over, cargo carriers as specially designed as the thrusters for their task. The monster cargo jumpers were hardly more than a pair of Necklin field generator rods in their protective housings so positioned as to be fitted around a constellation of pod bundles, a bracketing pair of normal space thruster arms, and a small control chamber for the jump pilot and his neurological headset. Without their balancing pod bundles attached the superjumpers reminded Leo of some exceptionally weird and attenuated long-legged insects.

     Each jump pilot, neurologically wired to his ship to navigate the wavering realities of wormhole space, made two hops a day, inbound to Rodeo with empty pod bundles and back out again with cargo, followed by a day off; two months on duty followed by a month’s unpaid but compulsory gravity leave, usually financially augmented with shuttle duties. Jumps were more wearing on pilots than null-gee was. The pilots of the fast passenger ships like the one Leo had ridden in on yesterday called the superjumper pilots puddle-jumpers and merry-go-round riders. The cargo pilots just called the passenger pilots snobs.

     Leo grinned, and considered that train of wealth gliding through space. No doubt about it, the Cay Habitat, fascinating as it was, was just the tail of the dog to the whole of GalacTech’s Rodeo operation. That single thruster-load of pods being bundled now could maintain a whole town full of stockholding widows and orphans in style for a year, and it was just one of an apparently endless string. Base production was like an inverted pyramid, those at the bottom apex supporting a broadening mountain of ten-percenters, a fact which usually gave Leo more secret pride than irritation.

From FALLING FREE by Lois McMaster Bujold (1988)

One of the incredible mentions in the Elon Mars concept was a thousand spacecraft in orbit ready for the Mars launch window to open. I’m not sure how many launch windows down the road this would be, I assume several decades. Whether it is next decade or next century though, an expensive asset like a spacecraft that is only capable of being used once every other launch window is a massive investment that is mostly idle.

I suggest an alternate concept for having a thousand vehicles heading toward Mars during one launch window. Each vehicle is an inert barge with a homing beacon and barely enough structure to house the cargo during thrust and coast. No engines, electricity, shielding, or other frills. These barges carry only items that store well. Machinery, provisions, propellant, clothing, etc.

The orbital gathering place for these barges is a high Earth orbit above the radiation belts but below Lunar orbit. The storage orbit keeps however many barges are heading out during each launch window in parking lot adjacent to a refueling facility that is stocked up between launch windows. The third item is skeletal booster tugs with no frills like ability to reenter or handle gravity.

There is a certain limited amount of time in a Mars launch window when the Hohman transfer orbit uses minimum propellant. There are periods of time on both sides of the ideal window that still get you to Mars, just at the expense of additional propellant. Total available time in the window can be a few months depending on available propulsion.

At the first opportunity, a tug with a dry mass of perhaps ten tons, a propellant load of two hundred tons, and a hundred ton barge, does a short burn to drop its’ perigee to just outside noticeable atmospheric drag. At perigee it is at nearly escape velocity when it does a strong (~4km/sec) Oberth effect burn to place the whole assembly on a Mars trajectory. Immediately after reaching the required velocity, the tug separates and a short retro burn to place the light tug back into an eccentric orbit with an apogee equal to the barge parking lot. The orbital equivalent to the SpaceX Falcon 9 boostback.

Back at the parking lot, the tug does a short burn to match velocities and goes for docking. Refuel, clamp onto another barge, and go again on intervals of one to four days. Depending on assumptions, each tug could send as many as a hundred barges per window to be caught on the other end.

So I can see the possibility of a hundred thousand tons of vessels heading to Mars during one launch window. The main hardware investments being launch vehicles, depots, and tugs that are kept employed at other tasks in the meantime between windows. People launch separately in vehicles suitable.

The main strength I would see in a scenario such as this is that the expensive hardware would be constantly available for use for other tasks. This is important for those of us that don’t see that much value in Mars as the next step out. The same equipment would be useful for asteroid missions or sending a Pluto lander. A heavyweight to Europa or a close solar corona investigation. Or more immediately useful support for Lunar and NEO missions.

From MARS BARGES by John Hare (2017)

FAR, FAR OUT on Pluto, where the sun is only a very bright star and a frozen, airless globe circles in emptiness; far out on Pluto, there was motion. The perpetual faint starlight was abruptly broken. Yellow lights shone suddenly in a circle, and men in spacesuits waddled to a space tug—absurdly marked Betsy-Anne in huge white letters. They climbed up its side and went in the air lock. Presently a faint, jetting glow appeared below its drivetubes. It flared suddenly and the tug lifted, to hover expertly a brief distance above what seemed an unmarred field of frozen atmosphere. But that field heaved and broke. The nose of a Pipeline carrier appeared in the center of a cruciform opening. It thrust through. It stood half its length above the surface of the dead and lifeless planet. The tug drifted above it. Its grapnel dropped down, jetted minute flames, and engaged in the monster tow ring at the carrier’s bow.

The tug’s drivetubes flared luridly. The carrier heaved abruptly up out of its hidingplace and plunged for the heavens behind the tug. It had a huge classmark andsnumber painted on its side, which was barely visible as it whisked out of sight. It went on up at four gravities acceleration, while the spacetug lined out on the most precise of courses and drove fiercely for emptiness.

A long, long time later, when Pluto was barely a pallid disk ‘behind, the tug cast off. The carrier went on, sunward. Its ringed nose pointed unwaveringly to the sun; toward which it would drift for years. It was one of along, long line of carriers drifting through space, a day apart in time but millions of miles apart in distance. They would go on until a tug from Earth came out and grappled them and towed them in to their actual home planet.

But the Betsy-Anne, of Pluto, did not pause for contemplation of the two-billion-mile-long line of ore carriers taking the metal of Pluto back to Earth. It darted off from the line its late tow now followed. Its radiolocator beam flickered invisibly in emptiness. Presently its course changed. It turned about. It braked violently, going up to six gravities deceleration for as long as half a minute at a time. Presently it came to rest and there floated toward it an object from Earth, a carrier with great white numerals on its sides. It had been hauled ofl Earth and flung into an orbit which would fetch it out to Pluto. The Betsy-Anne’s grapnel floated toward it and jetted tiny sparks until the tow ring was engaged. Then the tug and its new tow from Earth started back to Pluto.

There were two long lines of white-numbered carriers floating sedately through space. One line drifted tranquilly in to Earth. One drifted no less tranquilly out past the orbits of six planets to reach the closed-in, underground colony of the mines on Pluto. Together they made up the Pipeline.

Carriers drifted on through space. They were motor-less save for the tiny drives for the gyros in their noses. They were a hundred feet long, and twenty feet thick, and some of them contained foodstuffs in air-sealed containers—because everything will freeze, in space, but even ice will evaporate in a vacuum. Some carried drums of rocket fuel for the tugs and heaters and the generators for the mines on Pluto. Some contained tools and books and visiphone records and caviar and explosives and glue and cosmetics for the women on Pluto. But ail of them drifted slowly, leisurely, unhurriedly, upon their two-billion-mile journey.

They were the Pipeline. You put a carrier into the line at Earth, headed out to Pluto. The same day you took a carrier out of space at the end of the line, at Pluto. You put one into the Earth-bound line, on Pluto. You took one out of space the same day, on Earth. There was continuous tratfic between. the two planets, with daily arrivals and departures from each. But passenger-trafiic between Earth and Pluto went by space liners, at a fare of fifty thousand credits for the trip. Because even the liners took six months for the journey, and the Pipeline carriers—well, there were over twelve hundred of them in each line going each way, a day apart in time and millions of miles apart in space. They were very lonely, those long cylinders with their white-painted numbers on their sides. The stars were the only eyes to look upon them while they traveled, and it took three years to drift from one end of the pipeline to the other.

But nevertheless there were daily arrivals and departures on the Pipeline, and there was continuous traffic between the two planets.

The Pipeline was actually a two-billion-mile arrangement of specks in infinity. Each of the specks was a carrier. Each of the carriers was motorless and inert. Each was unlighted. Each was lifeless. But—some of them had contained life when they started.

The last carrier out from Earth, to be sure, contained nothing but its proper cargo of novelties, rocket fuel, canned goods, and plastic base. But in the one beyond that, there was what had been a hopeful stowaway. A man, with his possessions neatly piled about him. He’d been placed up in the nose of the carrier, and he’d waited, mousy-still, until the spacetug connected with the tow ring and heaved the carrier out to the beginning of the Pipeline. As a stowaway, he hadn’t wanted to be discovered. The carrier ahead of that—many millions of miles farther out—contained two girls, who had heard that stenographers were highly paid on Pluto, and that there were so few women that a girl might take her pick of husbands. The one just before that had a man and woman in it. There were four men in the carrier beyond them.

The hundred-foot cylinders drifting out and out and out toward Pluto contained many stowaways. The newest of them still looked quite human. They looked tranquil. After all, when a carrier is hauled aloft at four gravities acceleration the air flows out of the bilge-valves very quickly, but the cold comes in more quickly still. None of the stowaways had actually suffocated. They’d frozen so suddenly they probably did not realize what was happening. At sixty thousand feet the temperature is around seventy degrees below zero. At a hundred and twenty thousand feet it’s so cold that figures simply haven’t any meaning. And at four gravities acceleration you reach a hundred and twenty thousand feet before you’ve really grasped the fact that you paid all your money to be flung unprotected into space. So you never quite realize that you’re going on out into a vacuum which will gradually draw every atom of moisture from every tissue of your body.

But, though there were many stowaways, not one had yet reached Pluto. They would do so in time, of course. But the practice of smuggling stowaways to Pluto had only been in operation for a year and a half. The first of the deluded ones had not quite passed the halfway mark. So the stowaway business should be safe and profitable for at least a year and a half more. Then it would be true that a passenger entered the Pipeline from Earth and a passenger reached Pluto on the same day. But it would not be the same passenger, and there would be other differences. Even then, though, the racket would simply stop being profitable, because there was no extradition either to or from Pluto.

So the carriers drifting out through emptiness with their stowaways were rather ironic, in a way. There were tragedies within them, and nothing could be done about them. It was ironic that the carriers gave no sign of the freight they bore. They moved quite sedately, quite placidly, with a vast leisure among the stars.

From PIPELINE TO PLUTO by Murray Leinster (1945)

3 March 2094, 0250 hours Flight Deck of the Catapult Hercules

His finger tips sweated in the close-fitting control caps. Only eighteen k-k's from Vesta and still no Company. What had they done—written the station off? The entire ship reached into his heightened awareness. The awesome engines designed to hurl inert cargo on multi-million-kilometer tracks through space. The heavy mining laser converted into a terrifying main weapon now slung in the cargo grapples. The thousands of bits of information from the ship‘: computers and sensing radars. Where the hell were they‘? “Come on, you Company fish, swim out into the pan."

Violently the ship executed a maximum burn maneuver with her nine and twelve o'clock engines. Some of the datastream elements were now glowing red. “Damage report: two mike hit on plates 1023/24 negative critical. Integrity 80-80."

“Beautiful, Dee, You saved our jewels with that cut."

Ulans tapped his foot reflexively. On the blue cross hair showing on the main screen, a yellow dot bloomed. Six thousand kilometers distant, several people died.

Catapults: Catapults are the means by which materials are transported within the Solar System. Catapults latch on to a container of ore extract and accelerate to a high speed before releasing the load in the direction of the destination. Another catapult at the destination intercepts the container and latches on to decelerate it. The ore is delivered tn orbital factories or delivered by shuttle to the surface (None of the interplanetary space ships is designed to land on the surface of a Planet.)


Unlike Miners and the so-called Transports (which were more like Ares Patrol ships), the Catapults were not normally equipped with lasers. Consequently, at the start of the game, they have no combal capacity. However, it would not be difficult to mount a laser in a Catapult, as the computer would be quite capable of aiming it, and plenty of spares were around. Hence, Catapults may easily gain combat capacity.

[9.91] At the start of the game, until serviced (see Case 9.92), all Catapults are treated as if they had major damage,

[932] During any Logistics and Maintenance Phase, Catapults may be fitted with lasers (“serviced”) at any Friendly Asteroid or Planet (see Case 15.35).


Conventional Cargo Vessels


I originally posted this on the /r/spacex a few days ago and I would like to post here an updated version with feedbacks accounted for.

I did this map of SpaceX Starship delivery costs between the Earth, Moon, and Mars, to try to understand how the space economy could develop in the near future now that we are going to get a large reusable launch vehicle.

Since Starship's raptor engines runs on methane, it can't fully refuel on the Moon (only liquid oxygen, no methane, because there is no carbon on the Moon), so I also included a competitor Starship-like than runs on liquid hydrogen and oxygen and has its main base on an industrialized Moon capable of producing large quantities of propellant (Lunar Port concept), to understand how that would threaten the business of Starship deliveries.

A number of common popular concepts for developing the private space economy are discussed in the black boxes at the bottom:

  • GEO/LEO servicing
  • Moon reusable landers
  • LOX from Moon ISRU
  • Lunar Port (extracting water to produce propellant)
  • Fuel depot at Earth-Moon Lagrangian point L1
  • Moon to Mars deliveries
  • Asteroid mining
  • Mars propellant
  • Mars food

I took the Delta-Vs from this reddit post with some added margins of up to 20%.

I needed this data for a study I'm doing on the economic viability of a Lunar Port space mission for ESA in partnership with 3 European universities, but hopefully that can be of interest for some other people here too, as it was on /r/spacex !

Original thread

PDF version file

Google sheets:

sheet 1

sheet 2

Landing Grid

This is very fringe science. I'm no expert, but the Richmond concept is probably more impractical than it is actually forbidden by the laws of science.

Nikola Tesla

Back in the early 1900's noted genius and mad scientist Nikola Tesla figured he could tap a conductive layer in Terra's upper atmosphere and used it to wirelessly broadcast electricity. The electricity would be held in standing waves around the entire globe, and could be tapped by machines in remote locations for electrical power. It would also make the entire upper atmosphere glow, making cities and shipping lanes happy while infuriating astronomers. Oh, and it would also work as a wireless telegraph.

While many of Tesla's devices were brilliant, this one was a total crack-pot idea. Telsa was suspicious of these new-fangled ideas about air-borne electromagnetic waves. Not to mention there was no way to send an electricity bill to the people using it.

Telsa managed to talk a bunch of investors into funding a pilot project, the Wardenclyffe Tower. The project was a disaster for various reasons and Telsa had a nervous breakdown.

Murray Leinster

About fifty years later science fiction writer Murray Leinster wrote a series of short stories featuring a huge device called a "landing grid." I have been unable to discover the source of Leinster's inspiration, but I suspect Telsa's Wardenclyffe Tower. As far as I have been able to determine the first of these stories was Sand Doom (1955), first of the Colonial Survey series.

Anyway a landing grid is a circular arrangement of steel girders and copper cables about half a mile high and one mile in diameter. It is set firmly into the planet's bedrock.

For a planetary colony, it supplies electrical power by tapping the electrical potential difference between the ground and the planet's ionosphere. The planet acts like a huge capacitor. One plate is the ground, the other plate is the ionosphere, and the insulating dielectric is the atmosphere in between.

Since the ionosphere is basically energized by the planet's sun it will supply electricity for as long as the sun shines. As to how much energy is available, the best I can say is "lots and lots." A certain Dr. Elizabeth Rauscher estimated that the ionosphere and magnetosphere had a potential energy of about 3 terawatts. No idea of how rapidly the energy would be replenished by the sun.

The second vital function a landing grid supplies a planetary colony is landing services. It can use technobabble tractor beams to grab a spacecraft at a range of tens of thousands of miles and gently lower it to land in the center of landing grid. Or gently lift a spacecraft from the grid up into space, releasing it several thousand miles altitude. The spacecraft does not have to spend horrific amounts of delta V to get halfway to anywhere. The inexhaustible supply of ionospheric electricity will do it for you.

The framework of girders requires about one foot of diameter for every ten miles of tractor beam range. They are typically one mile in diameter, giving the tractor beam a range of about 53,000 miles (about 6.7 Terran diameters).

When a new planetary colony is founded, the first construction crew lands in rocket-propelled vehicles (since there is no existing landing grid). Their priority is to quickly build a grid to get the colony started.

In theory, interplanetary and interstellar war was not possible in Leinster's novels. Naturally a planet would not be foolish enough to use their grid to land a hostile invasion force. And the grid was perfectly capable of attacking an enemy orbiting fleet with tractor-beam launched missiles, or even rocks for that matter. Without grid support, an invasion force trying to land troops would need lots of rockets with ugly mass ratios. The invading fleet can launch missiles and bombs, but they have limited supplies (limited to what they brought with them). The planet ain't going to run out of rocks.

And if the invaders destroy the landing grid, they will lose easy access to the surface. Worse, any invading forces actually on the planet will be stranded until a new grid can be constructed. So the invaders do not want to nuke the grid, but the grid can decimate their fleet with hypervelocity rocks.

The theory was exploded in Leinster's 1957 story The Grandfathers' War. Basically they built a space-going landing grid.

Conventional grids grab objects in space with a tractor beam and pulls it to the ground. This monster grabs the ground with a tractor beam and pushes the grid into space. Conveniently the FTL drive can operate the instant a ship (or space-going landing grid) is several planetary diameters away from the planet, so the grid does not even need any rockets. Directly into FTL drive it goes. The warlike grid travels under FTL drive then emerges into real space in orbit around the target planet. There it uses its tractor beam to land itself, instantly creating an invader-controlled grid on the surface of the hapless planet. The grid then lowers the hordes of invading troop carrier starships gently to the surface and the attack begins. The only question I have is can the space-going grid tap the target planet's ionosphere while in orbit?

Lucky for the peace of the galaxy, in Leinster's universe nobody ever copied the grid-ship idea, and it was forgotten. The idea was not used in subsequent novels.

Walt and Leigh Richmond

In 1962 Walter Richmond was doing research into atmospheric electricity and invented what he called the Solar Tap. It was a way to access the potential energy difference between the ionosphere and the ground, but it was rather hair-raising.

You build an insulator, a pyramid shaped pile of rock about 150 meters tall. Be sure you locate the insulator well away from the magnetic poles of the planet. From the peak is shot a powerful laser beam pulse to create a conducting ionized trail all the way to the ionosphere. A titanic bolt of lightning travels down the trail to hit the insulator. There equipment does its best to harvest as much of the lightning as it can, without destroying the equipment or too much of the surrounding landscape.

As an encore, distribute the energy world-wide by using some sort of technobabble Tesla style energy broadcasting technology.

Why is it so important to site this far away from the magnetic poles? Well, the lightning bolt will create a magnetic field cross-wise to the planet's natural magnetic field. The result is to pinch the bolt and stop it after a few microseconds. Then you shoot another laser blast to created the next lightning bolt. All nice and controlled.

If the insulator is at a magnetic pole, the lightning bolt's magnetic field will be parallel to the planet's field. The bold will not be pinched. It will be permanent until the ionosphere is depleted after a week or so (an "avalanche"). In other words about 3 terawatts of power will start evaporating the continent around the magnetic pole, split the tectonic plates and start the continents moving around, create nuclear winter, destroy all civilization and cause a global extinction event.

That would be bad.

In 1967 Walt and Leigh Richmond wrote The Lost Millennium aka Shiva. The idea behind the novel was that solar taps were not only possible, they had been invented about eight thousand years ago. The reason we were unaware of this is because the idiots back then had sited the main tap at the magnetic pole in the name of maximum power harvesting, and they resolved to be very very careful not to let an avalanche start. With predictable results. Pretty much erased their entire civilization, it did.

The reason the insulator for a solar tap is about the same size and shape as the Great Pyramid of Cheops is because the latter is an insulator for a solar tap. Apparently some survivors from Atlantis built Giza a couple of thousand years after the avalanche (the pyramid that caused the avalanche was pretty much obliterated). Well away from the magnetic pole you will note. The laser firing makes a noise that sounds like "SHEEEEE!" and the returning lightning bolt makes a sound like "OPS!". So the solar tap in operation sounds like SHEEE-Ops!, SHEEE-Ops!, SHEEE-Ops!. Which is where the Cheops pyramid got its name. Cute.

The novel includes all sorts of historical anomalies harvested from tales of Atlantis, ancient astronauts, and Chariots of the Gods? The reason archaeologists are not constantly stumbling over eight thousand year old automobiles and skyscraper girders is because the broadcast power system made large metal objects a dangerous idea.

Anyway the other item relevant to our interests is that the solar tap could also be used to boost and land spacecraft. The Richmonds are vague in the details but they maintain that a network of smaller pyramids can create a pattern of laser beams to craft a titanic Jacob's Ladder. The high-voltage traveling arc boosts or land spacecraft by electromagnetic induction. Somehow (the details are left as an exercise for the reader). In the novel, during boost mode the solar tap sounds like ANGOR-WATT! ANGOR-WATT! which is also cute.

In their later novel Gallagher's Glacier the Richmonds take up planetary liberation by solar tap. In the novel, all the poor planetary colonies are controlled by an evil corporation. The colonies are not allowed to have solar taps, because the corporation do not want the colonies to be anywhere near being self-sufficient.

Gallagher takes a tip from Leinster and mounts the solar tap on a spaceship. It is impossible for a colony to covertly build a solar tap over a couple of decades without the evil corporation goons noticing. But once Gallagher's space ship shows up, the colony instantly has a solar tap, and can use its energy to defeat the goons and kickstart building their own permanent solar tap.


     The landing system was from what Gallagher called their solar tap. They were tapping the electrical potential that exists between a planet and its orbiting proton and electron belts—the belts of ionized particles caught in the planet's magnetic field.
     The landing system was part of a power system that produced, from this one site, enough electricity to power the entire continent on a broadcast basis.
     Broadcast power. It had been known on Earth since the days of Nicola Tesla—the system for putting power on the airwaves the way radio and TV are broadcast. Electric power that you could tune into, the way you tune in a radio.
     With broadcast power, you didn't have to have wires strung around the continent to plug in motors and appliances and furnaces and the like. You didn't have to carry your own fuel in! your ground car. You tuned in your motor to the power frequency, the way you tune in a radio to the frequency of the station you want to hear.
     Earth hadn't had broadcast power, though she'd known how to broadcast it, because the production of power was geared to installations that didn't have sufficient potential that you could waste it on the airwaves. But the power potential in the solar tap was so great you could throw it away on an inverse-square: basis and still be able to tune in at the coast lines, two thousand miles distant, and run anything you wanted to run, from a manufacturing complex to a skimmer.
     The power that exists between the ground potential on any planet and the orbiting proton and electron belts trapped in the magnetic field of any planet, is fed by the solar wind of the sun around which the planet orbits, and it is a practically limitless potential. Electrons from the solar wind make their way in through the magnetic poles of the planet, distribute themselves at its crust, and seep through the insulating atmosphere towards the strong positive potential of the inner proton belt.
     If you make a "short circuit" through the atmosphere by creating an ionized pathway with a laser beam that reaches to the ionosphere, the top of the insulating atmospheric layers, the electrons will jump across the short circuit, changing the groundside potential. When the groundside potential lowers, it makes it possible for more electrons to pour in from the solar wind to equalize the potential. The planet is effectively recharged, and you can short-circuit again.
     It's done in milliseconds, and it's done on a pulse-basis. You turn the laser-beam short circuit off and on in an alternating-current effect, and it's most efficient at a low sonic frequency, although it has radio-frequency overtones.
     There was a group of huge pyramidal structures that were the bases for the solar tap and landing system. A huge, central pyramid was the -tap itself; built of granite with a marble overlay, and of sufficient size to insulate the tremendous bursts of power flow from the ground. The laser installation was on a small platform at the peak of the pyramid, and the control systems were centered well inside where the X rays and other radiation from the flow would not harm the technicians.
     From this, central pyramid, the pulsed power was broadcast across the continent, and even from inside the canteen and at this distance you could hear the deep-throated roar of that power, pulsing through at a frequency within the audible range. Chee-ops, chee-ops, chee-ops, it seemed to say as it shorted in, was cut off, and pulsed in again.
     It was the landing system that used the smaller, satellite pyramids around the big one and that used other factors of the huge central pyramid as well.
     The landing system was a gigantic web of laser beams, angled upward and focused to create a huge electrical discharge spiral that used magnetic induction and repulsion to bring the meteors in. They could bring in any metallic ship as well on that huge spiral, even though the interstellar ships were comparatively fragile; for the gentle cradle of the magnetic induction-propulsion system could raise or lower the gigaton masses as evenly as a freight elevator might bring down a crate of delicate electronic equipment.
     The landing system. From the huge central pyramid, and from each of the smaller ones, two great alternating laser beams angled upward, aimed through tunnels internal to the pyramids and geometrically accurate to a hair. Those beams discharged their alternating spirals into a crisscrossed web of induction-repulsion that caught a ship and either stepped it up from rung to rung of the magnetic induction-propulsion ladder, or cradled it gently downward.

     "But where's the meteor we came down in, and what's your plan for it?" I asked. "That's a big plenty of steel."
     "Over there." He pointed to where I could see a glow in the sky at the center of the port complex. "We can use steel. We just use it with know-how."
     I stared at the glow in the sky. "Surely it couldn't have been that hot?"
     "That glow? That's not the meteor. That's the melting tap in operation. But the meteor did come in at a red heat, at least in its surface layers. You see, we land them direct into the furnace, "and as soon as everybody's clear, they change the frequency of the induction current and start melting them down. Saves quite a bit of time, and time's our most precious commodity. The energy we're not worried about—that we've got in plenty. But it takes time to reheat, and if the ejection mechanism doesn't work, it's a couple or three hours' setback to lose the heat that was built up during descent so that we can get the people out. And then we have to reheat the darned thing so we can melt it down."
     "Isn't that a rather expensive way to get steel?" I asked.
     He grinned. "You're just not used to the idea of really planetary power," he said. "Those meteors—asteroids, really—can be brought in, melted down, and ready to use for tool steel at a cost per ton of, say, a hundredth of a solar credit."

     The ridiculousness of shooting a planet with the ineffective sting of a fine-focused laser began to creep up on me. The focus on this device was so fine that it would probably make no more than a centimeter-diameter hole in whatever target it hit, and though that's plenty big to play utter havoc with a space vehicle, it would be less than the sting of a mosquito so far as a planet was concerned.
     "Set power pulse to three seconds."
     Gallagher's voice was slightly edged, but Cricket's came back in a singsong that showed no overtones of emotion.
     "Power pulse on three seconds by off point five seconds."
     "Initiate pulse."
     Cricket didn't have to respond to that one because the power machinery did it for her. There was a slow, rhythmic, mmm-pop, mum-pop from the power supply that went on and on and combined with the cheeee to form a now-familiar repetitive pattern; the song of power that I had heard on Betsy Ann: cheee-ops, cheee-ops.
     "I'll be damned," I yelled. "This thing's an upside-down solar tap!"
     There was a choke behind Gallagher's laugh, and his voice had a sweep and flow that spoke of tensions releasing.
     "We're way above the radiation belts," he said, "but the oscillating lens of our zoom focus makes an ionized path from Durango's ionosphere to its ground, and that's all you need for a tap. We didn't have time to build a pyramid down there, so we turned the tap upside-down."

From GALLAGHER'S GLACIER by Walt and Leigh Richmond (1970)


3-D Printing

3-D printing is also known as "additive manufacturing". This is because the object is created by adding blobs of new material, instead of the conventional method of starting with a block of material and carving away the unwanted bits (for example, as done by a CNC router).

This was a mind-blowing concept when Keith Laumer used it in his 1981 novel Star Colony, but with the advent of hobbyist 3-D printers it is now considered trendy but not impossibly futuristic.

Corporations will be angered by 3D printers: if you thought the RIAA went ballistic about digital music piracy and the MPAA was freaking out about movie file sharing, you ain't seen nuthin' yet. Manufacturers are going to start foaming at the mouth about digital object piracy. I predict even more draconian Digital rights management laws.

There is already in the real world people who are stirring up trouble by making blueprints that will 3D print plastic "ghost" firearms with no serial numbers. They are trying to strike a blow for Libertarianism, but they might just wind up making 3D printers illegal. Angry corporations are one thing, angry governments are even worse.

And if you take a super-duper 3-D printer and hook it up to a super-duper 3-D scanner, you have a Star Trek Replicator. Which will create unintended consequences.

But I digress.

NASA is interested in 3-D printing because Every Gram Counts. It would be a valuable savings in mass if a spacecraft did not have to carry spare parts for every conceivable thing that might break, but could instead only carry a 3-D printer and the raw material. You do not have to waste payload on spare parts you might never need. And the computer blueprints have zero mass.

Most currently available 3-D printers only print with one material (generally some kind of plastic). Innovators are frantically working on printers that can handle multiple materials. This is vital for printing, say, an electric motor or an electronic circuit. Currently available printers deposit blobs of material, in the future they will deposit on an atom-by-atom basis.

In September 2014, SpaceX delivered the first zero-gravity 3-D printer to the International Space Station (ISS). On December 19, 2014, NASA emailed CAD drawings for a socket wrench to astronauts aboard the ISS, who then printed the tool using its 3-D printer.

As a proof-of-concept, Markus Kayser created the Solar Sinter. He noted that in the deserts of Terra, there is a lack of useful artifacts but unlimited amounts of sunlight and sand. The Solar Sinter is a computer controlled magnifying glass that 3-D prints by melting layers of sand. There are many planets and moons where such a tool would be incredibly useful.

Architecture Et Cetera (A-ETC) is working on Project SinterHab. This will use microwaves to fuse Lunar dust in order to 3-D print habitat modules for a Lunar base.

Foster + Partners is working with the ESA to make a 3-D printed lunar base. Lunar soil is mixed with magnesium oxide to produce the material. Layers are bound by being sprayed with a binding salt in a controlled pattern. The binding salt turns the material into a stone-like solid.

A 3-D printer can also be used as the "assembler" component of a Santa Claus Machine.


      Archinaut, a NASA Technology Demonstration Mission (TDM) project developing cutting-edge technology to build and assemble complex hardware and supersized structures on demand in space, achieved an unprecedented milestone this summer.
     "To our knowledge, this is the first time additive manufacturing has been successfully tested on such a large scale in the vacuum and temperature conditions of space," said Eric Joyce, Archinaut project manager for Made In Space Inc. of Mountain View, California, which spearheads the project for NASA.
     The Archinaut test series, using Made In Space's innovative Extended Structure Additive Manufacturing Machine, was conducted in a vacuum chamber in the Engineering Evaluation Laboratory at NASA's Ames Research Center in Moffett Field, California.
     The team conducted hundreds of hours of tests to complete the series. Working around the clock for much of June, they printed large beam segments — similar to those used to construct a variety of space structures — and subjected printing equipment and printed hardware alike to the pressures, temperatures and other rigors of deep space.
     "This was a big step for us," Joyce said. "It advances the technology — and gives us real confidence the hardware will do the job in space that it does here on the ground, enabling us to print sturdy, reliable structures of unlimited size. It was a history-making test."
     Archinaut is one of three "tipping point" projects NASA is funding in pursuit of groundbreaking new solutions under the umbrella of TDM's In-space Robotic Manufacturing and Assembly (IRMA) project, sponsored by NASA's Space Technology Mission Directorate. These projects help NASA determine whether the technology has been sufficiently matured to pursue flight demonstrations or for infusion into future exploration missions.
     "We couldn't be more pleased about Archinaut's successful demonstration," said Trudy Kortes, TDM program executive at NASA Headquarters in Washington. "In-space robotic manufacturing and assembly technologies are destined to be key building blocks for a thriving space infrastructure, and will enable robust future exploration missions across the solar system. Milestones such as this one are crucial steps toward that future."

Building in space to curtail cargo launches

     Better known as 3-D printing, additive manufacturing could offer solutions for quickly and cheaply mounting new space infrastructure missions to Earth orbit and beyond. Combined with robotic manufacturing and assembly, the technology could help NASA and its commercial partners remotely construct new habitats and hardware in space — without the costs or risks associated with flying heavy materials or structures via rocket from Earth to space.
     Just as crucially, building to order in space frees future missions from the limitations of conventional spaceflight. "Until now, everything we have sent to space has been constrained by the volume available on various launch vehicles," Joyce said. "That fundamentally limits the size and geometry of anything we send up."
     Additive manufacturing would nullify that obstacle. "Instead of launching a rocket with a complete vehicle crammed on board, what if we just launch feedstock — raw material — and do all manufacturing and assembly in space?" he added. "All the constraints go away, and rockets become more efficient at delivering cargo to space."
     The logical next step — following another test series in early 2018 to further hone the capabilities of the ESAMM prototype and refine Archinaut's robotic manipulator — is full-scale, in-space flight demonstration. The team is already pondering its ideal project for that potential future mission: a massive communications satellite dish, or perhaps a supersized truss designed to robotically deploy solar panels? Time will tell, Joyce said.
     Ultimately, Archinaut could evolve into a build-to-order space platform. Vehicles or satellites could dock to enable construction, assembly and integration of whatever space-optimized hardware or systems they require, Joyce suggested — permanently rewriting the way humans travel to space.
     "This technology is absolutely transformative," Joyce said. "Archinaut has the potential to dramatically advance discovery in space, reducing the time and money spent launching hardware and equipment and putting the focus on the human explorers who will use that made-in-space equipment to explore the cosmos."
     The Archinaut team includes lead subcontractor Northrop Grumman Corp. of Falls Church, Virginia; Oceaneering Space Systems of Houston, Texas; and Ames Research Center. TDM projects such as Archinaut mature groundbreaking technologies for infusion into government and commercial programs, dramatically extending human capabilities and opportunities in space. NASA's Marshall Space Flight Center in Huntsville, Alabama, leads the TDM program for the agency.

For more information about Archinaut, visit:

To learn more about NASA's Space Technology Mission Directorate, visit:

At the heart of Archinaut technology is Made In Space's Extended Structure Additive Manufacturing Machine (ESAMM). ESAMM is a manufacturing method which incorporates Archinaut’s additive manufacturing system with a robotic manipulator to create objects in free-space and install both additively manufactured and pre-fabricated components.

Created by MIS and validated in microgravity research flights through the NASA Flight Opportunities Program, ESAMM produces arbitrarily large and complex structures. By using its robotic manipulators to position the part being created, ESAMM can constantly reorient the part with a high degree of freedom, allowing the part to be created as large as desired in any dimension. This allows ESAMM to create structures as small as an oxidizer tank fueling cap, as large as a Mars cruise vehicle back bone, or any size in between.

Archinaut is capable of additively joining previously manufactured or pre-fabricated elements together, enabling assembly of spacecraft. Different mission profiles require different materials and prefabricated components, thus the variety of feedstocks available for use by Archinaut is broad and includes multiple spaceflight-proven materials such as space-grade polymers and composites.


"I am a physicist. I specialize in the field of molecular structures. As you know, practically all of the raw materials used in industry today are synthesized from artificially transmuted elements—using techniques originally perfected on Mars." The Assassin nodded, keeping his eyes fixed on the professor. Brozlan went on: "The synthetic compounds used today are amorphous in nature—they do not possess any highly organized internal structure. Essentially the processes just turn out vast quantities of some particular kind of molecule, without assembling the molecules together into any higher level of organization." He took a long breath and then said: "An area of research that I was involved in some time ago had to do with taking the idea one step further."

"To produce a full range of materials needed on Mars, it was not sufficient to just synthesize or import unstructured molecules in bulk," Brozlan resumed. "We needed to be able to duplicate, say, the crystal lattice structures of many metal-base compounds, or the polymer chains of organic substances—things that are abundant on Earth but totally lacking back there."

"I'd have thought that that's where you'd use traditional processing methods," the Assassin muttered. He didn't mind talking as long as it was he who was asking the questions. It could only be to his ultimate advantage to know more about what was going on.

"On Earth, yes," Brozlan replied. "Primary raw materials are cheaper than they've ever been, because they're now synthetic. From those primary materials, things like steel, rolled alloys, fabricated goods, and so on must still be produced in much the same way as they've always been. Hence the costs are much the same as they've always been, and by the time they get to Mars that means expensive."

"If you ship it all up from Earth," the Assassin agreed. "But why bother? Why not just set your own processing plants up right there?"

"We could have done that." Brozlan nodded. His face creased into a frown. "But somehow we were not satisfied with that idea. We had a virgin planet with no set ways or traditions to uphold. It seemed unsatisfactory simply to follow slavishly the methods that had evolved on Earth. We could have spent fortunes copying all of Earth's industrial complexes on Mars only to find them obsolete before they went into production. You see, we were convinced that there had to be a better way."

The Assassin thought for a moment and looked puzzled. "How?" he asked at last. Brozlan's eyes glinted. He replied:

"Consider any form of component that is used in the construction of a larger assembly . . . the parts of a machine, for example. How is the component made? Answer—we take a lump of whatever material we need and cut away from it all the excess to leave the shape that we require. That forms the basis of just about every machining process that is used traditionally. Cut away what you don't want to leave behind what you do want."

"Okay." The Assassin shrugged. "What other way is there?"

"Deposition!" Brozlan peered at him intently as if expecting some violent reaction. The Assassin looked back at him blankly. Brozlan explained: "Instead of cutting material away to leave the part, we deposited material to build the part up!"

"You mean like electrolytic forming? That's not new."

"The idea isn't," Brozlan agreed. "But the way we were doing it was. You see, electrolytic forming works only with certain metals. We were working with every kind of molecule."

"You mean you could build up something out of anything—any substance at all?" The Assassin looked astounded.

"Exactly! And it didn't have to be all from the same kind of molecule, either. We could mix them together any way we chose.' For instance, we could produce a solid block that was phophor-bronze at one end and polythene at the other, with a smooth transition from one to the other in between. It opened up a whole new dimension in engineering design possibilities. The whole process was computer-controlled. A designer could develop a program to create any part he wanted out of any material he chose or any combination of materials—molecule by molecule if he really wanted to go down to that level of detail and if he had the patience and the processor power to handle it."

"Molecule by molecule .. ." The Assassin's face registered undisguised disbelief. "That's incredible . . ."

"Nevertheless, it worked," Brozlan told him. "There have been experimental plants on Mars operating for years now, turning out goods that are higher in quality and far cheaper to produce than anything' that could ever come out of the factories of Earth—even things normally processed from organically derived substances, such as paper, oils, fats, sugars . . . you name it."

"Oil . . . food . . . paper ... all synthesized from transmuted elements?" The Assassin gaped as his mind struggled to take it all in. "Why have we never heard of such things?"

"Politics." Brozlan sighed. "By that time there was a different brand of thinking among the higher echelons of the Federation government. Ambitious and unscrupulous men were taking over. They did not see these discoveries as potential benefits.for all mankind, but only as a means toward furthering their own designs by securing full economic autonomy. They began to see themselves as undisputed rulers over a thriving and self-sufficient world. Those purposes would be served better if Earth were allowed to lag behind, with its industries unable to compete against the newer Martian ones. The Federation authorities assumed tight control over our work and placed a strict security blanket over everything. That was why few people knew about what we were doing. That was also where the movement for Martian independence had its origins. Only a handful of individuals stand to gain, and not in the ways that are popularly believed."

"Interesting, isn't it, Hadley?" the colonel came in, spinning suddenly on his heel to face the bed. "But if you think that's hard to swallow, wait until you hear the next bit." He nodded at Brozlan, who continued:

"That was just one aspect of the research work going on at that tune. Another aspect was Dr. Franz Scheeman's work on structural scanning with neutrino beams. You see, Scheeman developed a method for scanning a material object, inside and out, and for extracting from the transmitted beams a complete encoding of the arrangement of atoms and molecules within the object. It was analogous to the way in which an old TV camera encoded the information contained in a visual scene." Brozlan took a deep breath. "The real breakthrough came when we combined Scheeman's technique with the molecular-deposition process that we have just been talking about!"

Silence reigned for a long tune while the Assassin digested the professor's words. Then his eyes widened slowly and transfixed Brozlan with a dumbfounded, unblinking stare.

"You're joking . . ." the Assassin breathed at last.

"A solid-object camera!" the colonel confirmed for him. "Yes, Hadley, you've got it. They could scan an object and derive a complete structural code for it. From that code they could generate a computer program to control the deposition process. Result—a perfect analog, a molecule-by-molecule copy of the original. And, of course, if they could make one they could just as easily make as many as they liked. Think of it, Hadley . . ."

The Assassin thought about it. Raw materials in abundance at negligible cost and the ability to transform them into any object for which an original already existed—it would be the Golden Age come true. Something in his expression must have betrayed what was going through his mind.

The colonel nodded and continued. "But think of some of the deeper implications, too. What would happen if somebody suddenly introduced that kind of technology into a complex and established economy like Earth's? Suppose that once you'd built the prototype of, say, a domestic infonet terminal"—he pointed to the bedside console—"you could churn out a million of them, all for peanuts. What would happen to the conventional electronics industry then? What about the components industry that supplies it? What would happen to the industries that supply all the parts—the plugs, sockets, metalwork, moldings, and all that kind of thing? And then what about the service industries that depend on all those in turn ... office equipment, furnishings, data processing, real estate, and so on through the list? How could they survive if half their customers and half their business went to the wall?" The colonel spread his arms wide in the air. "All finished, Hadley. Total collapse. How could you cope with ninety-five percent of a planet's population being suddenly redundant? How could a global economy, with its roots buried in centuries of steady evolution, survive an upheaval like that?"

"You see," Brozlan added, "That is exactly what the Federation government wanted to do. They wanted to rush full-speed into setting up a huge Martian industrial conglomerate based on the new technology, flooding Earth's markets with goods at giveaway prices."

"Earth would have been ruined," Barling interjected. "Or at best would have faced the prospect of existing as a very second-rate entity, dependent on a new rising star."

From ASSASSIN by James P. Hogan (1978 )

(ed note: the intruders have entered the solar system and are systematically committing genocide on the species known as Man. For asteroid colonies, an alien laser broadcast subtly reprogrammes the 3D printer to create a deadly infective substance that destroys technology. This would not kill on the habitable planet Terra, but sabotaging the technology of an asteroid colony will destroy all life support)

SOMETHING LIKE A LIGHTHOUSE BEACON WAS SWEEPING the solar system. On Ceres, the first cluster of gamma-ray telescopes picked it up and passed the signal to the station's computer net with a red tag for instant analysis. Within a microsecond, one of the most highly advanced brains ever built by the hand of man had undergone a subtle change in programming and, against all previous instructions, sent an ominously less subtle program change on a hairline beam of laser light to one of the gamma-ray telescope robots.

And still within that part of a second, the robot began to respond. Its multiple brains had been designed to predict the consequences of any action— from lifting a rock to constructing a new furnace— and then to decide the appropriate action at lightning speed by committee voting. Even without a human presence, the machine was capable of manufacturing a gamma-ray telescope, or anything else it was instructed to supply.

Antlike in appearance, it was more like a colony of machines than an entity of its own—just as its creator had intended. It had been built from and by a hive of smaller, simpler machines, which still circulated inside it like motile cells through a dense matrix of connective pathways. There were workers of many shapes and sizes, and what could even be called "drones" and "egg-laying queens." Each was so intensely social, and so intimately connected to the robot's circuits, that if it were isolated from the rest of the hive, it could no more function on its own than an ant cast out of its hill or a human marooned on an island, and it quickly "died." Like an anthill, or the Ceran colony itself, every robot hive met all the essential criteria of an organism.

One half second after the laser flashed into its eyes, the hive sensed a loss of some essential material it had been programmed to produce—a loss that, left unaccounted for, would have violated its first directive and allowed the human colony inside Ceres to come to harm.

The material in question had never existed before on Ceres, or anywhere else in the solar system; but the hive did not know that it was being deceived, that it was not acting on orders given it by human beings. Egoless, incapable of friendships or emotional ties, free of conscious sympathies and antipathies, without overt motives or concealed ones, the hive's brains and workers responded so fast that it was already fashioning the right tools and had already located the right chemicals before Ed Bishop could even begin to notice that a problem was developing.

By the time the maglev had shuttled him from Isak's home to the north pole, a pressurized tent had already sealed off his stricken, half-eaten robot from the rest of Ceres, a phone line had already connected the tent to the colony, and a system of laboratory modules was already being trucked to the site.

The tent itself enclosed a fully equipped "clean room." Bishop had entered through an airtight; glove box that fit him like a space suit, and in the ; center of the room one of the robots was melting in the warming air. It occurred to him then—too late—that no one should have been allowed to pressurize the chamber or heat the air. A second robot had stood on the far side of the room, ready to assist him. Now both machines lay in melting heaps, and Bishop found himself alone and afraid, abandoned by his crew, as he retreated to a module whose hull was twisting out of shape and leaking air. He tightened his suit helmet, hoping to buy himself a few more minutes of life, and began his final report to Isak.

There was very little he could say that was new to the president. One of the machines had been tricked into producing a substance that, for lack of a better name, Bishop had come to call a "molecular virus" or "template"—with which it had promptly infected itself.

Isak had replayed the images over and over on his pad: Bishop's robot on the floor of the tent, being eaten as if by a mighty cancer, breaking open like a poorly constructed beehive, thousands of microrobots spilling out of the rent across its abdomen, writhing and melting; Bishop's robot assistant placing samples under the scopes; and then, after an hour or two, the scopes themselves seizing up and flaking apart. .. and then the robot assistant.

The scopes had lasted long enough to show, with brutally realistic computer animation, what was happening. Most chemical reactions released their excess energy as heat: random, chaotic molecular motion. Every schoolgirl knew that every chemical compound had a specific melting point, at which the motion became so distorted that the crystalline structure broke down and individual molecules drifted off in different directions. The template molecule, when it came into contact with a ceramic composite, a carbon-metallic alloy, or with almost any substance likely to be manufactured by civilized beings, rearranged its crystal structure in such a way that the old melting points were drastically altered. Superconductors failed to function. Mechanical parts either became brittle or liquefied at room temperature. On the face of each crystal in the "tissues" of the stricken robot molecules were rearranging identically and transmitting a pattern of molecular recoil to every neighboring crystal— which vibrated and softened in turn.

"To get the ball rolling, the robot need only have innocently manufactured a few milligrams of this stuff," Bishop said. He was breathing hard inside his helmet, speaking quickly now, and Isak detected a touch of panic in his voice. "When all this got started, that's all there was—less than a gram. Then we had the whole robot and the scopes and then another robot crumbling to pieces—tons of the stuff lying around. How do you contain something like that? Sooner or later it was bound to get out. Sooner or later it should even get to the Intruders."

"But that seems an unlikely hope," Sargenti added. "They would have built-in protection, some sort of half-life. Otherwise they'd have to worry about meteorite impacts flicking bits of contaminated dust off Ceres and one of their ships coming in contact with it."

"If this had happened on Earth," Bishop said, "they could have counted on the winds to spread template dust to every continent. All the towers and skylines would have vanished. Obviously that wasn't enough. They wouldn't have been happy just knocking Earth back to the Stone Age and leaving the Acropolis, Renaissance cathedrals, Mayan temples, and the forests still standing. But here on Ceres, where we depend on high-tech for everything—even the air we breathe—the template is the perfect Final Solution." He stopped and took a deep breath. "One other thing. I'm afraid it's gotten through the material in my suit and into me. From the feel of it, I'd say even the iron and calcium in our bodies is vulnerable."

There was a popping sound behind Bishop, and the room fogged as the air pressure dropped.

From THE KILLING STAR by Charles Pellegrino and George Zebrowski

Santa Claus Machine

The Santa Claus Machine is sort of a technological version of Aladdin's Lamp or a Cornucopia. Basically it is a Star Trek Replicator that uses in-situ resources as feedstocks. More crudely it is a mass spectrometer feeding a 3D printer.

If you are trying to set up a base or colony on a desolate moon or planet, a Santa Claus Machine could be the difference between success and failure. The less equipment and prefab base you have to bring and the more stuff you can manufacture with local resources, the better.

As with any such thing, it has two parts: a disassembler and an assembler. This is because there are two basic operations possible in the universe, analysis and synthesis. That is, breaking one large object into smaller parts, or assembly smaller parts into one larger object. The ancients called this "solve et coagula" (e.g., written on the arms of the Sabbatic Goat in the famous illustration by Eliphas Levi).


The disassembler breaks down the input material into atoms, then sorts the atoms by element and isotope. This provides the raw materials needed by the assembler.

In most Santa Machine designs, the disassembler is a fusion torch attached to a mass spectrometer (in this context the fusion torch has nothing to do with the similarly named "torchship").

You shovel rocks, dirt, and other regolith into the hopper of the fusion torch. The input matter is flash heated to a temperature of about 15,000 K by the awesome power of thermonuclear fusion, disassembling all the compounds into individual atoms and ionized atoms at that. You now have all the atoms separated in a plume of ultra-high temperature plasma.

There are many proposed ways of sorting the atoms into bins for each individual element and isotope. The most commonly mention method is using a mass spectrometer.

Atoms have inertia, like anything else that is matter. And like all other matter the more mass an atom has, the more inertia is has. So if the atoms are moving in one direction in a atomic beam, if you give each atom a shove to the right with a given strength push the atoms with less inertia will be nudged off course more than the atoms with more inertia. Without the push all the atoms in the beam will strike the target point. The shove with smear the target point to the right. If you nudge enough, the target will smear into a row of points, one for each element. Nudge it more and the points will separate further into points for each isotope of each element.

All you have to do is put a collection bin at each target point and they will fill up with pure isotopes. But do be careful about the bins for fissionable isotopes. Allowing a critical mass to accumulate will have unfortunate consequences.

Mass spectrometers generally use a magnetic or electrostatic field to give atomic beam a shove.

Keep in mind that what you get out depends upon what you load into the input hopper. If the asteroidal regolith you are shoveling in contains no uranium, none is going to show up in the collection bins. You might have to import isotopes that are absent in your location.

Just imagine how useful the fusion torch+mass spectrometer combo would be for recycling the mountains of trash filling up our real life land-fills. The entire blasted world is impatiently waiting for somebody to tame fusion power.

Also note that this technology makes it easy to refine uranium ore into weapons grade uranium, which will make the astromilitary and the authorities extremely nervous. Current enrichment techniques such as gas centrifuges require the resources of an entire nation the size of Iran. A fusion torch could do in your garage.


(ed note: in this space opera Aarn needs some super-duper chemical elements to create his new super-science weapons. He figures the giant star Torka has all sort of chemical elements beyond atomic number 100 which have not been discovered yet but presumably exists. He uses handwaving tractor beams to grab a blob of star-stuff and uses handwaving force fields to create a crude mass spectrometer.)

      Three and a half hours later Aarn stopped the Sunbeam. The gravito-magnetic sheath had been relaxed, but (the giant star) Torka was still a great disc, and their strange cargo glowed angrily orange, at a temperature of thousands of degrees. Aarn got to work immediately, setting up new fields he had carefully plotted.
     "Well—here goes, and Carlisle, cast an eye over this one. It's got your scheme beaten, I suspect. I have about five hundred million tons of matter there—and every ounce of it ionized. Now watch—"
     Suddenly a vast gout of flame spurted out of the compressed, tightly bound mass of incandescent matter. For hours Aarn had been holding it in check only by his tremendous forces. Now it shot out through a gap he had made, thrusting out under the incalculable power of released pressure, pressure generated in Torka where trillions of tons of matter had weighed down on it, pressed by the terrific gravitational force of the sun. (Aarn is holding the high-pressure ionized star-stuff inside a handwaving force field. By opening a small hole in the field, the hot gas spurts out)
     The stream bent abruptly, fanning out strangely, and part seemed to wrap about itself, forming a new center, smaller and colder. Most of it curved, some circling half way round, but it escaped, fanned, and spread in space, beginning a long, long fall back to Torka. "It works," Aarn exulted. "It works, Carlisle! I'm getting it—an atomic spectro-separator on a gigantic scale, and I'm collecting no atoms lighter than atomic number one hundred!" (like a mass spectrometer Aarn bends the stream with a magnetic field, to sort the atoms by mass. Atoms with an atomic mass of 99 are allowed to escape, the higher mass atoms are captured in a second force field.)
     Carlisle started, and stared at the swiftly growing dark center. "One hundred! There isn't any known, let alone heavier." (Fermium was discovered after this novel was written, discovered in the debris of the first hydrogen bomb explosion in 1952)
     "Not on a planet—but inside a nuclear reactor that big and that violent, a lot of improbable but possible events have a chance to occur. These super-atoms are synthesized. And I pulled that out from about one thousand miles down—just as deep as I could reach before the forces simply tore my beam to fragments. But now that stuff is cooling by expansion—"
     The expansion as the ions escaped was cooling it rapidly, and Aarn drove a heating transpon beam into it. Resting almost motionless, his own ship was using little power, and the excess he turned into the seething mass swiftly drove the temperature up, and increased the ionization.
     It took over four hours to finish the operation, but at last a great cold ball of matter rested in the beams, while a vast cascade of flaming atoms was falling, falling, falling the fifty millions of miles back to Torka. (the cold ball has all the fascinating new undiscovered elements, the cascade of falling atoms are all the old boring known elements)
     "I wish I could work on that stuff right now," exclaimed Aarn as, with full coils, he drew the mass of the gleaming metallic sphere inside the walls of his forces, and set himself for the homeward trip. Torka grew hazy, space changed, and even the stars moved slowly, while three flashing, curved lines represented the three planets as the Sunbeam shot toward swiftly expanding (planet) Cornal.
     In an hour the Sunbeam was back in her berth. In half an hour more, workmen under Aarn's directions had cut off a fifty pound mass of the cooled stuff, and put it in a great lead case. The rest, Aarn took out to a deserted island, far from any city. The rays from this mass of super-heavy elements were potent, and deadly. In that mass, carefully separated as it had been, perhaps a tenth of one percent of lighter, known elements had been included. Radium was there, more than the Tornans had ever had before.
     "I'm going to get to work," said Aarn decisively, as they landed again. "I want to see what I've got. Carlisle, you can have about five pounds of that stuff if you want it—you might determine all the chemical elements present, and all the properties thereof. You'll probably find some of them are still missing—gaseous substances that escaped—but you'll get them as other, heavier ones break down to form them. And—here's something to watch out for: there will be numerous elements of the same chemical structure but having different atomic weights. Pick 'em out carefully, will you? I'll have some of these physicists here rig up a very high-power spectro-separator for you that ought to catch an atomic weight difference of one in any element less than 350."

From THE INTERSTELLAR SEARCH by John W. Campbell, Jr. (1949)


The assembler takes atoms from the disassember's output, and puts them together according to the user selected blueprint.

This will basically be advanced versions of the 3D printers and rapid prototyping machines available now. Instead of just handling one material (typically plastic) they will be capable of printing in multiple materials. They will accept as feedstock the elements and isotopes from the disassembler, and either chemically create the required compounds or just print the compounds by alternating the atoms.

Early crude versions will print blobs of paste composed of compounds created from the atom feedstocks, much as a commercial 3D printer makes objects out of molten plastic. Later advanced versions will assemble the object atom by atom.

The limits will be

  1. the chemical elements required from the disassembler for object currently being printed (does the local regolith have all that is necessary?)
  2. the availability of blueprint files for the desired object (are the blueprints illegal?)
  3. the speed of printing the object (if it takes ten years to print, forget it)
  4. the supply of fusion fuel to power the fusion torch (though with fusion you are talking gigawatts per centigrams/seconds of fuel)

Faster printers will be more expensive, because that's the way it always is.

Some blueprints will be illegal (e.g., DIY nuclear warhead) and of course will be readily available anyway from data smugglers and on the dark web. There might be illegal blueprints which on the surface look innocent, but combining part 23 of the dust precipitator plan with part 17 of the air conditioner plan creates a working submachine gun.


The human consequences of the singularity reverberated endlessly, too. The exiles hadn’t simply been dumped on any available world; in almost all cases, they’d been planted in terrain that was not too hostile, showing crude signs of recent terraforming.

And the Eschaton had given them gifts: cornucopias, robot factories able to produce any designated goods to order, given enough time, energy, and raw materials. Stocked with a library of standard designs, a cornucopia was a general-purpose tool for planetary colonization.

Used wisely, they enabled many of the scattered worlds to achieve a highly automated postindustrial economy within years. Used unwisely, they enabled others to destroy themselves. A civilization that used its cornucopia to produce nuclear missiles instead of nuclear reactors—and more cornucopias—wasn’t likely to outlast the first famine, let alone the collapse of civilization that was bound to follow when one faction or another saw the cornucopia as a source of military power and targeted it. But the end result was that, a couple of hundred years after the event, most worlds that had not retreated to barbarism had achieved their own spacegoing capabilities.

Newpeace had been settled by (or, it was more accurate to say, the Eschaton had dumped on the planet) four different groups in dispersed areas—confused Brazilian urbanites from Rio; ferocious, insular, and ill-educated hill villagers from Borneo; yet more confused middle-class urban stay-at-homes from Hamburg, Germany; and the contents of a sleepy little seaside town in California.

Each colony had been plonked down in a different corner of the planet’s one major continent—a long, narrow, skinny thing the shape of Cuba but nearly six thousand kilometers long—along with a bunch of self-replicating robot colony factories, manuals and design libraries sufficient to build and maintain a roughly late-twentieth-century tech level McCivilization, and at ten-meter-tall diamond slab with the Three Commandments of the Eschaton engraved on it in ruby letters that caught the light of the rising sun.

From IRON SUNRISE by Charles Stross (2004)

Needless to say the invention of a Santa Claus Machine will have a drastic effect on the economy of your civilization.

And other things too. I've already mentioned how the powers-that-be will be concerned with giving rock-rats the ability to manufacture weapons of mass destruction and refine kilogram lots of weapons grade fissionables. And I'm sure the futuristic equivalent of the MPAA and RIAA will be furious with Joe Asteroid wallpapering their habitat dome with atom-level perfect copies of the Mona Lisa. Not to mention how angry the banks will be with a device that can crank out undetectable counterfeits of coins, bills, cheques, and other legal documents.

Of course things get astronomically worse if a Santa Claus Machine can produce copies of itself. Now you've got a freaking Von Neumann self-replicating machine on your hands.

I have a feeling that Santa Claus Machines will always be under military guard, much like the beam propulsion lasers controlled by the Laser Guard. The Santa Guard will place the machine at the site of a future base/colony, and watch what is manufactured like a hawk. If a colony builder submits a blueprint for something questionable, they are liable to be apprehended by the Santa Guard and questioned.

In the far future Santa Claus Machines might be equipped with a law-abiding artificial intelligence. If the user asks it to make a nuclear warhead, the machine will refuse and call the cops.


Matter Replicator: The cornucopia machine or autofac, which can build matter into pretty much any object that you want and have – or can write – a recipe for.

Sadly, they are required to obey the laws of thermodynamics and conservation of mass-energy. They also tend to incorporate – especially in larger models designed to build larger objects – arrays of specialized nanofactories and macro-scale tools, and require plenty of energy and specialized appropriate feedstocks for whatever it is you want them to build (so mining, refining, recycling, bactries, and the rest of the industrial supply chain haven’t gone away quite yet). You can make them increasingly general-purpose in these areas at the cost of greater inefficiency – field autofacs are a lot less elegant and more energy-hungry and expensive to run than standard household models.

Living things generally have to be grown in a medical vat instead; simply because most of them tend to die when only half-printed. Yes, this is exactly as gross as it sounds. (Also, some dead organic matter – well, let me put it this way. While you can print up a steak in an autofac, steak is still made in carniculture vats, because first, self-replicating steak is cheaper, and second, it gets boring eating the exact same steak hundreds or thousands of times. Similar although aesthetic considerations are why vatwood is generally preferred to directly replicated wood – although vatwood planks are seen as input to larger autofacs.)

Nonetheless, they’re more than good enough for post-material scarcity purposes.


Since we’ve just passed the Matter Replicator trope, and since it may be relevant to an upcoming FAQ question, I thought I’d throw out some definitions relating to such things that may make things clear. Well, clearer.

A nanofac is the basis of nanofacturing technology. Think of it as essentially a 3D printer which can handle arbitrary molecular components with single-atom resolution. (It doesn’t have to: a lot of the time it can simply place pre-assembled multi-atom components picked out of its feed, but the point is that it can.) While it can use free-floating assembler nanites as part of its operation, the vast majority of the work is done in a supercooled vacuum chamber by an array of distant descendants of the atomic force microscope. The materials supply it needs is fed to it as a suspension of molecular components called nanoslurry available in a variety of forms, supplied as a utility from a central nanosource that makes the stuff from raw materials and recycles the return feed of all the stuff that the nanofacs don’t use.

Most important to note is that a nanofac is not a discrete thing you can buy itself – it’s just the term for the central construction array as a module.

What you can buy, on the other hand, is a cornucopia, which is a general-purpose construction device that comes in sizes ranging from desktop-printer-sized (the ubiquitous nanoforge) to dishwasher/fridge size. These are common household, etc., appliances, packaged as vending machines by companies like Valuematic Vending, and are basically a user interface/power supply/etc. wrapped around an appropriate nanofac. They can make pretty much anything you can describe in a recipe, or conceptual seed, to give it its formal name, although if it’s something too big to fit into its vacuum chamber what you’ll get is a heap of parts over several runs which you have to assemble manually following the v-tags after you get them out. (They may or may not bond permanently once you do this.)

A specialized cornucopia, on the other hand, is a fabber. These exist because in nanofacturing, there’s essentially a scale with versatility at one end and efficiency at the other. A cornucopia is a magical device that can make everything, but isn’t the fastest or most efficient way to make anything in particular.

So there are fabbers, which trade off that ability for greater speed and efficiency and customized user-friendliness in doing one particular thing. So while you want a cornucopia available to you, certainly, what you want in your wardrobe is a clothing fabber, in your kitchen is a food fabber, in your sickbay is a pharmafabber, in your wet bar is a cocktail fabber, etc., etc.

And finally, it’s worth noting that assembling things atom by atom, or molecule by molecule, is not actually a terribly efficient way to do things in the first place. It works fine for small objects, sure, where the convenience outweighs the inefficiency, and especially for those made out of lots of tiny components with fine detail to assemble. But large things, especially large things with large areas of relatively homogeneous structure, you really don’t want to make that way.

Which is where autofacs come in. An autofac is a automated assembly system that contains an array of nanofacs for making individual detailed components, but which also contains lathes and drills and presses and kilns and extruders and all manner of other macroscale manufacturing-process equipment, along with plenty of motile robots whose job is to do the assembly of all the different outputs of these processes into the end product. (So they take in nanoslurry for the ‘facs, but also metal ingots, ceramic powder, plastic granules, etc., etc., as their raw materials.)

These vary in size from the relatively modest autofacs you’ll find in most neighborhoods, belonging to companies like Ubiquifac, whose job is to construct large goods people have ordered on-line at a point relatively local to them for immediate delivery, up through larger factories – such as the ones that take nanoslurry and sheet metal in at one end and have finished vehicles drive out the other – all the way to truly giant many-square-miles really-can-build-anything complexes like the Hive.


Yes, folks, it’s that time again for the first time when I answer y’all’s background questions!

We have one question this month. James Sterrett asks:

What precursor elements do autofacs require for fabrication? The same elements in the same proportions as the finished product (plus waste etc), or can they synthesize required elements?

Well, now, that’s an interesting question with quite a complicated answer, inasmuch as autofacs are rather complicated things in themselves..

Let me first suggest that this might be a good time to re-read Things That Make Things, since it covers a lot of the terminology I’m about to be throwing about.

So let’s start at the small end, with one of the most common working parts of an autofac, and which is also the core component of a cornucopia, including the ubiquitous desktop nanoforge, the portable nanolathe, and the specialized fabbers.

These, themselves, can’t synthesize elements, or indeed produce any other part of their feedstock – which is to say, you can’t just throw trash into them and have them rearrange it into what you want (you need specialized disassemblers for that, that are hardened to the job. Throw trash into a cornucopia, you have a good chance of wrecking the delicate internal components). They’re just glorified 3D printers. They’re absolutely dependent on a supply of feedstock, which is called nanoslurry.

(One exception to this is that you can also get what is called a nanobrick, which is basically dehydrated nanoslurry and formed together with a mass of simple assemblers. You use it together with a programming nanolathe for field construction, after mixing it with a suitable solvent, usually water, to form a nanopaste. But that’s not what we’re talking about here.)

Nanoslurry itself is a complex suspension of materials useful in nanoconstruction, designed to make it as easy and efficient as possible for nanofacs to pick out the bits they need. It comes in a variety of different kinds and grades, most of which are intended for one specialized industrial application or another. Standard-grade, which is what is shipped out as a public utility down municipal nanopipe systems, comes in two forms, informally referred to as “gray” and “green”.

The nanopipe you have plugged into your domestic cornucopia, for that matter, is actually a four-pipe system. The first supplies gray nanoslurry – which is water, long-chain alcohols, sulphur and nitrogen compounds, a suspension of iron and copper oxides, heavy metals, silicates, acetats, nanograins of industrial plastics, ceramics, and alloys, and prefabricated molecular components, or to put it another way, everything you might need to perform “common mechanosynthetic applications”. The second supplies green nanoslurry, which is specialized towards organic synthesis applications – what this means, of course, varies from world to world. And the third is the special-order pipe, which gets aliquots of specialized feedstock shot down it upon request, because while you may occasionally need, say, 2.1 g of technetium, it’s something specialized enough that there’s no point in including it in the regular feedstock.

(The fourth is the return pipe, that pumps what’s left after the nanofac has picked out what it needs back to the nanosource for recycling.)

And what the nanofacs need is, well, exactly what elements are in the finished product. (Plus a certain degree of in-process waste that ends up squirted down the outgoing pipe back to the nanosource.)

So, so far, we’ve just pushed the problem back to the nanosource; after all, nanoslurry doesn’t exist in nature, so it has to be manufactured. Which is what nanosources do: out of a variety of sources. Air mining, for worlds with atmospheres that have useful components. The bactries of chemical companies, refining volatile asteroid-liquor into useful chemicals with bacterial aid. Giant metal ingots shipped from smelters, which are reduced to slurry components. Reclaimed and purified chemicals from recycling plants and biocleaning cascades. In short, from the ends of all the conventional supply chains. Larger autofacs, like the Hive, will usually have their own nanosource(s) to produce all the specialized feedstocks that they want, especially since autofacs use a bunch of those raw materials elsewhere in their non-nanotech manufacturing processes.

So now we’ve just pushed the question back another level, haven’t we, to “can the people the nanosources use as suppliers synthesize elements?”

To which the answer is, finally: yes, but they usually don’t.

Nucleosynthesis is possible. There’s an entire engineering discipline, alchemics, that specializes in this sort of thing. But it’s neither cheap nor convenient, inasmuch as it still involves banging nucleons together and trying to get the wee buggers to stick, a process that tends to involve particle accelerators and nucleonic furnaces and isotopic separators and mucking about at absurdly high energy densities and low efficiencies. That said, it is now regular non-experimental engineering, and a large enough autofac might well include the equipment.

…but economically, it is almost always cheaper to dig the stuff up and have it shipped to you for nanosource processing than try to manufacture it on site from other elements. Nature’s production process may be slow and uncomfortably explosive for anyone within a couple of hundred light-years, but, damn, does it have economies of scale.

This effect is only amplified, of course, by the fact that alchemics equipment is also what you use to produce gluonic string, muon metals, and various other kinds of exotic matter that genuinely don’t occur in nature anywhere. Now that’s what you call comparative advantage!

Self-replicating Machine

A self-replicating machine or Von Neumann device is an independent robot that can create a duplicate of itself from materials scavenged locally. The little monsters can multiply exponentially (i.e., like cancer) so it is best you have some kind of control or kill switch on them.

They are used when you have a really big job, so you want the robot work force to scale itself up to a size suitable to the task. For example: covering the entire equator of the planet Mercury with solar power cells in only a few years. Or sending robot space probes to every planet in the entire galaxy.

Of course it can be weaponized as either an anti-ship or planetary attack weapon.


A self-replicating machine is a type of autonomous robot that is capable of reproducing itself autonomously using raw materials found in the environment, thus exhibiting self-replication in a way analogous to that found in nature. The concept of self-replicating machines has been advanced and examined by Homer Jacobsen, Edward F. Moore, Freeman Dyson, John von Neumann and in more recent times by K. Eric Drexler in his book on nanotechnology, Engines of Creation and by Robert Freitas and Ralph Merkle in their review Kinematic Self-Replicating Machines which provided the first comprehensive analysis of the entire replicator design space. The future development of such technology is an integral part of several plans involving the mining of moons and asteroid belts for ore and other materials, the creation of lunar factories, and even the construction of solar power satellites in space. The possibly misnamed von Neumann probe is one theoretical example of such a machine. Von Neumann also worked on what he called the universal constructor, a self-replicating machine that would operate in a cellular automata environment.

A self-replicating machine is an artificial self-replicating system that relies on conventional large-scale technology and automation. Certain idiosyncratic terms are occasionally found in the literature. For example, the term "clanking replicator" was once used by Drexler to distinguish macroscale replicating systems from the microscopic nanorobots or "assemblers" that nanotechnology may make possible, but the term is informal and is rarely used by others in popular or technical discussions. Replicators have also been called "von Neumann machines" after John von Neumann, who first rigorously studied the idea. However, the term "von Neumann machine" is less specific and also refers to a completely unrelated computer architecture that von Neumann proposed and so its use is discouraged where accuracy is important. Von Neumann himself used the term universal constructor to describe such self-replicating machines.

From the Wikipedia entry for SELF-REPLICATING MACHINE

(ed note: "rollers" are Lunar cargo hauling vehicles, with built-in pressurized habitat modules)

     “That reminds me of something I’ve been meaning to ask," Ben said, a little embarrassed and eager to change the subject. “Why are rollers so cheap? You’ve kept telling me that machines are expensive on the Moon. We bought a used one, but even the new rollers I priced were cheap. I'm not arguing with the price—but there’s a contradiction there.”
     Garrison thought for a moment. “Okay, lemme see if I can explain it. Suppose you wanted to sell eggs on the Moon. What would you import, eggs or chickens?”
     “Chickens, of course,” Ben said. “Or probably fertilized eggs, let ’em hatch here.”
     “Minor detail. A fertilized egg is just a chicken in compact packaging. But the point is the same. Since eggs are something everyone can use, it’s worth shipping in a whole egg factory—that is, the chicken—rather than importing the finished product, the egg. You sell a million eggs cheap and make your money on volume. Now, suppose you wanted to important caviar. What do you ship in—the fish eggs or the sturgeon?”
     “The caviar, obviously.”
     “Right. Not only is the fish harder to take care of than a chicken, but a lot fewer people are going to want the product. So if you’re going to make a living selling caviar on the Moon, you’re not going to have much volume. You send the price through the roof to compensate.”

     Garrison took a sip of his beer and went on. “What’s expensive on the Moon are the caviar machines, things you only need a few of if you need them at all. Specialized high-tech stuff. Like the automated ID booth you were expecting. Or maintenance robots. Or luxury items, like those automatic hairdressers that were such a big fad when we were in New York. They’d cost too much, so the Conners get along without them and tell themselves they're better olf without them. If we ever get back to Central, ask Mrs. Lombroska her opinion of automated hotel systems. That’s the caviar stulf.
     “What we've been riding in is a chicken’s egg. There are thousands of rollers around, because some UNLAC lab on Earth designed a whole roller factory. They built it, shipped it here, switched it on, and stepped back. It s been cranking out rollers ever since. They’ve tweaked up the design a few times, and they put out a few different models for dilferent jobs. Cargo versions, oversize jobs like that big guy out front. Besides dialing in what model to make, they just leave the factory alone. Which makes rollers cheap. Basic supply and demand.

     “The kicker is that the factory is totally automated, right down to raw materials. I got a tour of it once. They have robot bulldozers that feed dirt into the hopper of a soil-cracker, and dedicated long-distance robot haulers that supply ore for lunar-rare elements like nitrogen from nearby mines. They fabricate the parts right from raw materials. Robot labor assembles it. They call it a half-von Neumann machine.”
     “Meaning what?"
     “A von Neumann is any machine capable of replicating itself. Then the relicas replicate themselves, and soon you’re up to your keister in von Neumanns. There have been some gimmicky lab gadgets that could copy themselves but no one has ever built a worthwhile true von Neumann. A half-von Neumann can endlessly duplicate a machine simpler than itself. ”
     “They can’t do that with an entire roller, Ben protested. “It’s too complex.”
     “You open up that control panel when we re back aboard and see how many parts there are in it. They ve got the things boiled down to absolute simplicity."

     Ben frowned for a second. “Wait a minute. Solar powered factory, right?”
     “So they've got free power. And they’re getting the raw materials essentially for free, digging the dirt out of the ground and refining it; Robots mine the raw materials and build the rollers, so you don’t have any labor costs. Power, material and labor free. Aside from the cost of building the factory, it doesn’t cost them anything to make the rollers! So what do they base the cost on?”
     “ ‘The value of a thing is that which it will bring,’ ” Garrison quoted. “They sell for whatever the market will bear. At the moment, the market is flooded, so rollers are cheap. Another good run of immigration, and thesupply will dry up. Or else they can just turn off the factory for a while until it’s needed again, and drive the price up a bit. But you've spotted a real problem there. How do you run an economy when things of value cost nothing to produce? The roller plant is an example, not an exception. Lots of common items on the Moon are produced that way.”
     “So how do they run the lunar economy?”
     Garrison shrugged. “UNLAC? I think they just ignore it and hope it will go away. I mean, Christ, you’ve got a whole planet here that doesn’t even have its own currency. Instead we use everyone else’s money—and half of that is in confetti-denominations. From an economic standpoint, the whole Moon is sheer chaos, but it works somehow. I think the policy people are afraid that if they try to fix it, people will notice it can’t possibly work, even though it's been working for years. Confidence would collapse, and the whole place would go to hell in a hand basket.”

(ed note: Garrison is asking about why deep-drilling gear is being hauled to the Lunar farside)

     “Why do they need deep-drill gear for way the hell out there?’ Garrison asked.
     “Laser array. ”
     “The comm laser array they’re building out there.”
     “Right, we’d heard about that," Garrison replied. “But what do comm lasers have to do with deep-drill mining?”
     “They're shipping a whole laser factory out there, and they need a bunch of materials that aren’t available on the surface. It’s the old factory that built the Nearside array."
     “A whole factory just to build a few comm lasers?” Ben objected.
     Garrison shrugged. “You have to put the factory somewhere. Cheaper to ship it than haul the final products halfway around the Moon, even if you only need a few lasers.

     “They need more than a few,” Mohammed said. “With the space traflic density they’re projecting, they'll need to track maybe two, three dozen comm-targets at once—most of the interplanetary shipping, plus the Settlements on Mars, the Belt, and the inner and outer planets. Plus you need back-ups for all of those, and you have to have lasers at several frequencies for various dull reasons. Right off the bat, they’ll need about a hundred frequency-tunable comm laser units. More with eventual expansion, and for replacement of broken units. Makes sense to build them on the spot. Besides which, the laser units aren't small. Each comm laser unit will be self-contained. Each one with its own solar cells and storage coils and pointing mechanism and so on.

     “If they had built ’em at Central Colony, and shipped ’em from there, maybe I’d have been able to fix two of them on my roller at a time. Shipping two per trip, and one trip a month, it would take over four years to get ’em all out there. That would cost UNLAC plenty, more so if they hired several oversize rollers to get it done faster. There aren’t that many outsizers around, and they cost plenty to hire. It’s cheaper, faster, and easier to ship a robot factory out there. In fact, most of the factory is already out at Farside Station. The deep-drill mining gear is the last component to go in.”

From FARSIDE CANNON by Roger MacBride Allen (1988)

(ed note: A self-replicating lunar factory (SRLF) would dramatically accelerate the rate of space industrialization. The problem is establishing the first one. A "seed" hardware has to be developed, then delivered to the lunar surface.

A 1982 study figured you'd have to deliver about 100 metric tons of seed hardware, basically the mass of an entire SRLF. This is far too much mass to deliver, short of an Orion Drive spacecraft. This can be reduces a bit by using 3D printing, but not enough.

A more drastic measure to reduce the seed mass is to avoid full "closure." A SRLF with full closure can totally replicate itself using local materials. A SRLF lacking full closure would require some of the components for the new machine to be shipped from Terra. The main missing item is the local manufacture of computer chips and electronics. A chip fabrication unit requires many tons of seed mass. The advantage of shipping computer chips from Terra is drastically lowered seed mass and faster SRLF replication time (since it doesn't have to make a new chip fab). The disadvanage is lack of full closure does not scale. As more SRLFs are produced, Terra will have to boost more and more computer chip mass.

The paper proposes a new approach: "bootstrapping."

The seed mass for the initial SRLF is low (about 12 metric tons) because the seed will only be able to create equipment that is much more primitive and crude than the seed, say 1700s-era technology. The 1700s tech will construct new equipment that was 1800s-era tech. The 1800s tech will construct 1900s-era tech and so on. It will bootstrap itself until it reaches the point of being an actual full closure SRLF. It will then start cranking out daughter factories and space industrialization goes into high gear. According to their mathematical model, the fully developed 7th generation SRLF will have a total mass of about 100 metric tons, which is in close agreement with the 1982 study. But this is from only 12 metric tons shipped from Terra, instead of 100 MT. Abet with several years of tech advancement.)

Once successfully bootstrapped, a robotic network can access, process, transport, and utilize the solar system’s resources for mankind’s benefit. Appropriately designed robots will not have the problems traveling the vast distances of the solar system that humans have, and they can set up the infrastructure that will enable us to follow. Within the first several decades a vital industry could be established on the Moon and in the asteroid belt using technologies that are for the most part only modestly advanced beyond today’s state-of-the-art. After that, human outposts, laboratories, and observatories can spring up everywhere between the Kuiper belt and Mercury. It can grow exponentially and provide mankind the ability to do things that today are only dreams...

...There are several additional strategies to reduce the launch mass of a seed replicator. The first is to identify and use only the simplest system capable of replication. The second is to avoid full “closure”. Closure is the ability to replicate all aspects of the system in space so that nothing further is required from Earth to build replicas. Nearly full closure is vastly easier to achieve than full closure (Freitas and Gilbreath 1980), because the manufacture of electronics and computer chips requires heavy, high-tech equipment that would be expensive to launch from Earth and would command much of the industry’s resources during replication. However, incomplete closure results in very high launch masses later as the industry grows exponentially, as we show below. A third strategy, which to our knowledge has not been discussed in the literature, is to begin with a simpler, sub-replicating system and evolve it toward the self-replication capability. In this strategy, the evolving system might never become a “self-replicator” even after it reaches full closure, because each generation can continue creating something significantly more advanced than itself. This is the strategy adopted here.

The first hardware sent to the Moon will be high-tech equipment built on Earth. However, the high launch costs demand that it be mass-limited so it will have insufficient manufacturing capability to replicate itself. It will construct a set of crude hardware made out of poor materials, so the second generation is actually more primitive and inefficient than the first. The goal from that point is to initiate a spiral of technological advancement until the Moon achieves its own mature capabilities like Earth’s. This evolving approach will provide several benefits. First, industry on the Moon can develop differently than on Earth. The environment, the manufacturing materials, the operators (robots versus humans), and the products and target markets are all different. Allowing it some reasonable time to develop will allow it to evolve an appropriate set of technologies and methods that naturally fit these differences. Second, the evolving approach supports the development of automation so that industry can then spread far beyond the Moon. The technological spiral will develop the robotic “workers” in parallel with the factories. It will also improve automated manufacturing techniques such as 3D printing. The third and probably most important benefit is the economic one. As we show here, a space economy can grow very rapidly, and it will quickly require massive amounts of electronics and robotics unless there is full closure. The tiny computer chips alone become too expensive to launch within a few decades as the industry grows exponentially, and therefore we will quickly need lithography machines on the Moon to make the computer chips. The evolving approach sends only a small and primitive set of machines as “colonists”, and the nascent lunar industry develops over time – but still rapidly – toward the full sophistication that Earth cannot afford to launch...

...So the objective is for the first robotic “colonists” on the Moon to fabricate a set of, say, 1700’s-era machines and then to advance them steadily through the equivalent of the 1800’s, 1900’s, and finally back into the 2000’s. We argue that this can be accomplished in just a few decades. There are reasons why this technological spiral will be both easier and faster than when we accomplished it on Earth. First, the majority of the technology does not need to be re-invented. The knowledge will be provided by technologists on Earth. Second, the Earth will provide material support in the early stages. We will send teleoperated robots and complex electronic assemblies prior to achieving closure. On the other hand, there will be new challenges. For example, we must gain experience in the lunar environment to learn how to adapt terrestrial technologies to it...

...For the concept of lunar industry presented here we do not think the term “self-replicator” is appropriate and so we will avoid the term. A self-replicator is by definition self-contained with all of its parts co-located in a complete set. That entire set fabricates a new complete set that is situated in a new location before the next replication cycle begins. This is unlike industry or biology on Earth: neither businesses nor industries are self-replicators. Although biological species are self-replicators, they require a vast number of other species in a highly networked ecology to survive, and the ecology does not operate on a synchronized replication cycle. We think the networked complexity of these examples is the more successful topology for space industry because it is the one that naturally occurs and hence is probably the more efficient and adapted for survival, as well as the more easily bootstrapped through an evolutionary process. We therefore avoid any requirement that the various hardware assets remain together in a closed set, and we allow instead for transportation to develop naturally between multiple, specialized production sites. Thus, lithography machines to make computer chips can be located in just one laboratory on the Moon, and their products can be transported to other sites for incorporation into robots and machines. The original facility to house that equipment can be built larger than necessary to allow for expansion and to gain economies of scale...

The set of assets within each generation is described below. To be conservative, we usually assume that each asset is retired at the end of its generation so that only the more modern assets of the new generation are involved in producing the generation after that (except as noted below for solar cells and robonauts). This is overly conservative, but it allows that hardware failures could disable some new assets that are unable to be repaired while assets from the prior generation continue to operate to take their place.

In Generation (“Gen”) 2.5, the use of the decimal place (rather than incrementing to 3.0) indicates that the assets of Gen 2.0 and Gen 2.5 are added cumulatively rather than retiring the Gen 2.0 hardware. We do this because it is necessary to vastly diversify materials manufacturing as quickly as possible, and this is accomplished by creating Gen 2.5 hardware that is no more sophisticated than Gen 2.0 although capable of making different materials.

The technologies needed for mining, chemical processing, and metallurgy are for the most part already existent in Earth’s industry. The feasibility of adapting them to the lunar environment has been and is currently being demonstrated by the wide variety of successful space utilization projects described elsewhere in this issue of the journal.

Excavators. The excavators will travel between the digging site and the resource processing site, delivering sufficient lunar regolith each hour to maintain production rates of the other assets. The details of the excavators are unimportant. In our modeling we assumed for specificity that they are small and operate in a swarm. They may also be fitted with paving attachments (Hintze and Quintana 2012).

Chemical plants for volatiles. Dry regolith or an ice/regolith mixture will be deposited into hoppers and then fed into chemical plants. Electrical power for the processes is augmented with thermal power from solar concentrators. One type of chemical plant will be concerned with producing gases and liquids. These fluids will include oxygen, hydrogen, water, hydrocarbons such as methane, and (in more advanced generations) solvents for industrial processes. So far, NASA has developed and field tested only basic oxygen production systems, including hydrogen reduction and carbothermal systems. More complex chemical processes have been developed for terrestrial applications, and by adapting the lessons-learned from the lunar projects it should not be difficult to adapt the other processes to the lunar case, too. For specificity, we have described the chemical plants using particular masses, power levels, and production rates after examining several sources of data. These include analyses of lunar chemical plants (Mendell 1985, Taylor and Carrier 1993) and the actual construction and performance of lunar chemical plants that our team and collaborators have recently field tested on Mauna Kea in 2008 and 2010 (Boucher et al. 2011; Captain et al. 2010; Gustafson et al. 2010a; Gustafson et al. 2010b; Muscatello et al. 2009). The specifics are not too important as we will vary these numbers over wide ranges to demonstrate general feasibility of the bootstrapping process. Gen. 3.0 and subsequent will have larger throughputs than the earlier generations, and they will gain from economies of scale by building much larger chemical plants rather than reproducing a large number of smaller plants (Lieberman 1987; Gallagher et al. 2005). However, to be conservative we ignore the economies of scale and instead describe the chemical plants as though they were units identical to the originals. These represent “units” of chemical processing capability in larger plants rather than standalone assets.

Chemical plants for solids. Chemical plants are also needed to produce plastics and rubbers from the lunar polar ice. This is possible because we now know that the ice contains large quantities of carbon molecules (CO, CO2,…) as well as nitrogen-bearing and hydrogen-bearing molecules (Colaprete et al. 2010; Gladstone et al. 2010). These materials may be needed for gaskets, seals, and insulators, for example. Later diversity will introduce sheet materials, fabrics, and layered and complex materials. Again, economies of scale are ignored in the model to be conservative.

Metal and Ceramics Refinery. It will be crucial to manufacture metals and metal-oxide ceramics and to improve the properties of the various alloys with subsequent generations. Processes to do this from lunar soil have been described (Rao et al. 1979; Jarrett et al. 1980; Sargent and Derby 1982; Lewis et al. 1988; Stefanescu et al. 1988; Landis 2007; Lu and Reddy 2008), and some development work is on-going by our colleagues and collaborators. Notionally, the early generations in our model will produce crude “mongrel alloys” by electrowinning or other methods. Hardware constructed from those alloys will need to be massive to add strength to make up for their poor mechanical properties. (This will be partially offset by the reduced forces in low lunar gravity.) Subsequent generations of metal refineries will add processes and material streams to improve the mechanics of the materials. Oxygen and other gases produced by metal refining will be sent to the chemistry plants. Electrical power is augmented with thermal power collected by solar concentrators.

Manufacturing. Additive manufacturing will have two forms: 3D printers that make parts that are small enough to fit inside the printer, and larger units that move about robotically and add material onto large structures external to themselves. The printers may eventually have multiple material streams including metals and plastics to make complex assemblies in a single pass. However, the earlier generations will require import from Earth of the most complex assemblies, such as electronics packages and the assembly robots. Furthermore, “appropriate technology” will mandate the design of simpler assets that can function without too many complex or miniaturized components, simplifying their manufacture and reducing imports. To achieve the final generations, the additive manufacturing technologies require advancement beyond the current state of the art. However, gains are being made rapidly and it is very likely the advancements will support the bootstrapping strategy presented here.

Solar Cell Manufacturer. Power will be provided mainly by solar cells. Ignatiev et al. (2001) and Freundlich et al. (2005) have shown how these may be manufactured on the Moon even in the earlier, more primitive generations of lunar industry. For specificity, we have described the mass, power, and throughput of the solar cell manufacturers as per those earlier studies. We show that these devices in the first and subsequent generations produce far more available power than needed by the following generation. This excess power capacity grows exponentially. We assume that solar cells are added cumulatively from one generation to the next. Failure of solar cells by radiation damage and micrometeoroids has not been modeled explicitly, but can be deducted from the exponentially growing excess.

Power Station. In the first generation, a power station is included in the mass of hardware shipped to the Moon. This station includes power conditioning, docking stations, and cabling to manage and distribute the solar power. It might also include a small nuclear reactor to support human presence and as a backup system to support re-bootstrapping in case of system failure.

Robonauts. Robotic astronauts, or “robonauts”, will perform the assembly and maintenance tasks. The name is borrowed from a particular robot developed by General Motors and the NASA Johnson Space Center, with the assumption that robonauts in future lunar industry will be the direct descendants of the current ones. The number of robonauts must grow rapidly as the industry itself grows. At first the robonauts are imported from Earth. To keep the strategy slightly more economical, they are not retired with each subsequent generation. Beginning with the third generation their structural components are made on the Moon, while Earth continues to send their cameras, computers, motors, and sensors. Eventually they are made completely on the Moon.

At first the robonauts will be teleoperated from Earth. The approximately 2.5 second round-trip communication time delay can be managed even for fine motor tasks, such as screwing parts together by hand, by having a teleoperator on Earth interact with a virtual world that models the robonaut and its environment rather than interact with the reality itself. The robonauts on the Moon will mimic the behaviors they observe in the virtual reality as closely as possible using existing levels of robotic autonomy. Resynchronization will occur in the virtual world using a rubric designed to prevent operator confusion. Similar schemes are being developed for telesurgery with large communication latency (Haidegger and Benyó 2003). This will make teleoperation manageable for lunar operations, but it will require a growing and expensive workforce of teleoperators on Earth plus sufficient communications bandwidth, and it will not be extensible to the asteroid main belt or beyond. Therefore, with each generation, progress will be made toward full autonomy.

Table 1 describes the autonomy in terms developed by Hans Moravec (Moravec 1999; Moravec 2003). Moravec’s “insect” level is when robots perform simple pre-programmed responses to sensor inputs. Many machines operate at the insect level today. The “lizard” level is when robots identify objects functionally to guide their motor tasks. Lizard-level robotics is already appearing in laboratories on Earth and is making steady progress toward greater capability. “Mouse” level is when the robots learn and improve the performance of their tasks through simple positive and negative feedback. This is important because human industry is only adapted to terrestrial conditions, but learning robots can adapt it to the multitude of environments they will experience in the solar system. “Monkey” level is when the robots maintain a mental model of the world including other agents. This provides them with insight into the intent of other agents as well as foresight. “Human” level is when the robots have the mental ability to reason abstractly, generalizing from specific learning situations to a broader class of applications, and thus to make decisions in the face of the unexpected. These higher levels of robotics will be necessary in the distant future when, for example, a robotic construction crew is building a science lab on Pluto, many hours of time delay away from human help. Extrapolating the computing speed of small, inexpensive microprocessors that are commercially available, we expect by the year 2023 they will reach the speed Moravec predicted as necessary to support human-level robotics. Even if Moore’s Law ended today, that computer power is easily achieved by paralleling inexpensive microprocessors and by other advances planned by computer chip manufacturers (Gargini 2005). On-going advances in robotic software and artificial intelligence present a very optimistic picture that these levels of robotics will be achieved as Moravec predicted, with lizard-level occurring by 2020, mouse-level by 2030, monkey-level by 2040, and human-level by 2050. Only mouse-level is needed by the end of bootstrapping on the Moon, but depending on how fast the strategy is carried out the robotics sent to the asteroid belt may be at the monkey-level or higher.

Electronics Manufacturing. In the baseline model, when Gen. 2.5 is fabricated its assets include some electronics manufacturing machines. Those machines themselves are built with electronics imported from Earth, and they are capable of making only the crudest and simplest of electronics components such as resistors and capacitors, which will not be miniaturized or efficient. Gen. 3.0 and subsequent possess a greater diversity of electronics manufacturing machines with increasing sophistication. By Gen. 5.0 we aim to have basic lithography machines on the Moon, built using computer chips sent from Earth, so that by Gen. 5.0 all computer chips can be made in space. The early computer chips will lack the transistor density of chips made on Earth, but they will be adequate for “appropriate technology” in space. Later generations (not modeled here) continue spiraling the sophistication of space industry so that eventually the lithography machines and computer chips match the best of Earth’s.

(ed note: the reseachers then created a mathematical model to determine how rapidy the lunar industry would grow. Maximum production rate "Max." is when the plants run full bore trying to make the next generation. Reduced production rate "Red." is when the plants pause manufacturing to allow other tasks, such as technological advancement, manufacturing experiments, or to allow slow robotnauts to catch up assembling parts. "Red." reduces the manufacturing rate by one-half. As it turns out, the reduced rate is the minimum necessary to meet survival and growth goals. Once the SRLF reaches the final generation, it can switch over to Max rate thereafter.)



In theory, a self-replicating spacecraft could be sent to a neighbouring planetary system, where it would seek out raw materials (extracted from asteroids, moons, gas giants, etc.) to create replicas of itself. These replicas would then be sent out to other planetary systems. The original "parent" probe could then pursue its primary purpose within the star system. This mission varies widely depending on the variant of self-replicating starship proposed.

Given this pattern, and its similarity to the reproduction patterns of bacteria, it has been pointed out that von Neumann machines might be considered a form of life. In his short story, "Lungfish", David Brin touches on this idea, pointing out that self-replicating machines launched by different species might actually compete with one another (in a Darwinistic fashion) for raw material, or even have conflicting missions. Given enough variety of "species" they might even form a type of ecology, or – should they also have a form of artificial intelligence – a society. They may even mutate with untold thousands of "generations".

The first quantitative engineering analysis of such a spacecraft was published in 1980 by Robert Freitas, in which the non-replicating Project Daedalus design was modified to include all subsystems necessary for self-replication. The design's strategy was to use the probe to deliver a "seed" factory with a mass of about 443 tons to a distant site, have the seed factory replicate many copies of itself there to increase its total manufacturing capacity, over a 500-year period, and then use the resulting automated industrial complex to construct more probes with a single seed factory on board each.

It has been theorized that a self-replicating starship utilizing relatively conventional theoretical methods of interstellar travel (i.e., no exotic faster-than-light propulsion, and speeds limited to an "average cruising speed" of 0.1c.) could spread throughout a galaxy the size of the Milky Way in as little as half a million years.

Implications for Fermi's paradox

In 1981, Frank Tipler put forth an argument that extraterrestrial intelligences do not exist, based on the absence of von Neumann probes. Given even a moderate rate of replication and the history of the galaxy, such probes should already be common throughout space and thus, we should have already encountered them. Because we have not, this shows that extraterrestrial intelligences do not exist. This is thus a resolution to the Fermi paradox – that is, the question of why we have not already encountered extraterrestrial intelligence if it is common throughout the universe.

A response came from Carl Sagan and William Newman. Now known as Sagan's Response, it pointed out that in fact Tipler had underestimated the rate of replication, and that von Neumann probes should have already started to consume most of the mass in the galaxy. Any intelligent race would therefore, Sagan and Newman reasoned, not design von Neumann probes in the first place, and would try to destroy any von Neumann probes found as soon as they were detected. As Robert Freitas has pointed out, the assumed capacity of von Neumann probes described by both sides of the debate are unlikely in reality, and more modestly reproducing systems are unlikely to be observable in their effects on our Solar System or the Galaxy as a whole.

Another objection to the prevalence of von Neumann probes is that civilizations of the type that could potentially create such devices may have inherently short lifetimes, and self-destruct before so advanced a stage is reached, through such events as biological or nuclear warfare, nanoterrorism, resource exhaustion, ecological catastrophe, or pandemics.

Simple workarounds exist to avoid the over-replication scenario. Radio transmitters, or other means of wireless communication, could be used by probes programmed not to replicate beyond a certain density (such as five probes per cubic parsec) or arbitrary limit (such as ten million within one century), analogous to the Hayflick limit in cell reproduction. One problem with this defence against uncontrolled replication is that it would only require a single probe to malfunction and begin unrestricted reproduction for the entire approach to fail – essentially a technological cancer – unless each probe also has the ability to detect such malfunction in its neighbours and implements a seek and destroy protocol (which in turn could lead to probe-on-probe space wars if faulty probes first managed to multiply to high numbers before they were found by sound ones, which could then well have programming to replicate to matching numbers so as to manage the infestation). Another workaround is based on the need for spacecraft heating during long interstellar travel. The use of plutonium as a thermal source would limit the ability to self-replicate. The spacecraft would have no programming to make more plutonium even if it found the required raw materials. Another is to program the spacecraft with a clear understanding of the dangers of uncontrolled replication.

Applications for self-replicating spacecraft

The details of the mission of self-replicating starships can vary widely from proposal to proposal, and the only common trait is the self-replicating nature.

Von Neumann probes

A von Neumann probe is a spacecraft capable of replicating itself. The concept is named after Hungarian American mathematician and physicist John von Neumann, who rigorously studied the concept of self-replicating machines that he called "Universal Assemblers" and which are often referred to as "von Neumann machines". While von Neumann never applied his work to the idea of spacecraft, theoreticians since then have done so.

If a self-replicating probe finds evidence of primitive life (or a primitive, low level culture) it might be programmed to lie dormant, silently observe, attempt to make contact (this variant is known as a Bracewell probe), or even interfere with or guide the evolution of life in some way.

Physicist Paul Davies of Arizona State University has even raised the possibility of a probe resting on our own Moon, having arrived at some point in Earth's ancient prehistory and remained to monitor Earth (see Bracewell probe), which is very reminiscent of Arthur C. Clarke's The Sentinel.

A variant idea on the interstellar von Neumann probe idea is that of the "Astrochicken", proposed by Freeman Dyson. While it has the common traits of self-replication, exploration, and communication with its "home base", Dyson conceived the Astrochicken to explore and operate within our own planetary system, and not explore interstellar space.

Oxford-based philosopher Nick Bostrom discusses the idea that future powerful superintelligences will create efficient cost-effective space travel and interstellar Von Neumann probes.


A variant of the self-replicating starship is the Berserker. Unlike the benign probe concept, Berserkers are programmed to seek out and exterminate lifeforms and life-bearing exoplanets whenever they are encountered.

The name is derived from the Berserker series of novels by Fred Saberhagen which describe a war between humanity and such machines. Saberhagen points out (through one of his characters) that the Berserker warships in his novels are not von Neumann machines themselves, but the larger complex of Berserker machines – including automated shipyards – do constitute a von Neumann machine. This again brings up the concept of an ecology of von Neumann machines, or even a von Neumann hive entity.

It is speculated in fiction that Berserkers could be created and launched by a xenophobic civilization (see Anvil of Stars, by Greg Bear or could theoretically "mutate" from a more benign probe. For instance, a von Neumann ship designed for terraforming processes – mining a planet's surface and adjusting its atmosphere to more human-friendly conditions – might malfunction and attack inhabited planets, killing their inhabitants in the process of changing the planetary environment, and then self-replicate and dispatch more ships to attack other planets.

Replicating seeder ships

Yet another variant on the idea of the self-replicating starship is that of the seeder ship. Such starships might store the genetic patterns of lifeforms from their home world, perhaps even of the species which created it. Upon finding a habitable exoplanet, or even one that might be terraformed, it would try to replicate such lifeforms – either from stored embryos or from stored information using molecular nanotechnology to build zygotes with varying genetic information from local raw materials.

Such ships might be terraforming vessels, preparing colony worlds for later colonization by other vessels, or – should they be programmed to recreate, raise, and educate individuals of the species that created it – self-replicating colonizers themselves. Seeder ships would be a suitable alternative to Generation ships as a way to colonize worlds too distant to travel to in one lifetime.

From the Wikipedia entry for SELF-REPLICATING SPACECRAFT

“Figured out what?” Sondra asked. “A theory about what?”

“About what the Charonians are,” she said.

“They’re von Neumanns. That’s it. That’s got to be it.”

“That’s what?”

“The answer, the explanation. The key to it all.

Not all by itself, but it’s a start.” Marcia stood up, still holding the pages of the message, and stared off into space, carefully thinking it all out. “It makes sense,” she said. “They’ve got to be von Neumanns.”

“Will you please quit saying ‘von Neumanns’ and explain what they are?” Sondra demanded.

“It’s very simple,” Marcia said. “How did we miss it? A von Neumann machine is any device that can exactly duplicate itself out of locally available raw materials. A toaster that could not only toast bread but build more toasters out of things found in the kitchen would be a von Neumann toaster. It’s a very old concept, named for the scientist who dreamed it up.

“But von Neumann’s real idea was to build a von Neumann starship,” Marcia said. “A robot explorer that could fly from one star system to another, explore the system—and then duplicate itself a few dozen times, maybe mining asteroids for materials. It would send out new von Neumanns, duplicates of itself, from there. Then each new exploration robot would travel on to a nearby star, duplicate itself, and start the cycle again. Each machine would report back to the home planet on what it found. Even given a fairly slow transit speed between stars, you could explore a huge volume of space in just a few hundred years. Traveling, exploring, reproducing, over and over again.”

Von Neumann Machine. Any machine that can precisely duplicate itself. A Swiss army knife that included a Swiss-army-knife-making attachment would be a von Neumann machine.

From THE RING OF CHARON by Roger MacBride Allen (1990)

He was saying to Frad: "The arrangements with the machinery are cumbersome, but not difficult in principle. We can lend you our Brood assembly until she replicates herself; then you reset the daughter machine, feed her scrap, and out come City Fathers (computers) to the number that you'll need—probably about a third as many as we carry, and it'll take maybe ten years. You can use the time feeding them data, because in the beginning they'll be idiots except for the computation function.

From A LIFE FOR THE STARS by James Blish (1962)

Space Plastic

Plastics are organic polymers, which means they are composed of huge chains of carbon and hydrogen molecules. The raw materials can be found in carbonaceous asteroids and in the hydrocarbon lakes of the Saturnian moon Titan.

Inside the closed ecology of a spacecraft's or base's CELSS some of the carbon and hydrogen can be diverted to brewing up some plastics. The source can be from carbon dioxide in the air or from agricultural waste.


I've mentioned several times that plastic can be produced from agricultural waste and/or CO2.

 The plastic of interest is polyethylene, or rather ultra high molecular weight polyethylene (UHMWPE, UHDPE, polyethene or trade names Spectra or Dyneema). It is formed of very long single chains of carbon, so the unit formula is CH2. This material is a thermoplastic, melting around 130 °C (or less if it contains solvents and/or crystalline defects). In normal use it should be kept between -150 °C and about 80 °C, so in-space applications will typically require a protective coating such as thin-film aluminum.

 So, we will assume we have available a quantity of ethanol (C2OH6) from other processes. Fermentation of sugar and/or cellulose is one possible source, as is syngas fermentation. It does not have to be perfectly pure; ethanol-water eutectic produced by distillation is acceptable. See the link for chemical structure and other data. This is passed through a fluidized bed reactor with alumina or zeolite dehydration catalyst that removes one molecule of water from each molecule of ethanol, yielding ethylene (C2H4) at high purity. The catalyst has to be regenerated periodically to recover the water and remove carbon and trace contaminants. The ethylene can be stored in high-pressure tanks.

 An alternative is to use the reverse water gas shift reaction to convert H2 and CO2 to CO; with additional H2 added this is syngas. The H2 would come from electrolysis of water. If methane is available it can be used with some O2 to produce syngas directly. Apply the methanol process, then apply something like the Mobil methanol to gasoline process to yield ethylene. Proper choice of zeolite will yield pure gaseous ethylene.

 The ethylene can be polymerized using titanium tetrachloride as a catalyst. This process has been used commercially for 60 years and currently yields high-quality resin with masses of 5.5 to 6 x10^6 grams per mol and contaminants of titanium (<40 ppm), aluminum (<20 ppm) and chlorine (<30 ppm), a total of 110 grams of catalyst lost per ton of plastic {UHMWPE biomaterials handbook, Steven M. Kurtz; chapter 2, tables 2.1 and 2.2}. Of these, chlorine is the hardest to replace unless there are convenient chloride salt deposits available; even so, 10kg of chlorine would be sufficient for 333 tons of plastic. The catalyst also requires magnesium chloride and a structural scaffold (usually microporous silica beads, sometimes zeolite or activated carbon), both of which can be completely recovered. The catalyst must be activated with triethylaluminum (TEA); this material is very dangerous and also useful as a rocket igniter. It can be produced using metallic aluminum, hydrogen gas and ethylene gas; if no TEA is available to jump-start the reaction then a small amount must be made using another process involving lithium hydride or ethyl chloride.
 A related catalyst, metallocene titanium, zirconium or hafnium chloride is used in solution with methylaluminoxane (MAO). Recent work has developed related catalyst systems using MAO; it is also very dangerous and is related to TEA. Synthesizing metallocene looks straightforward, but the input materials are fairly complex.
 These reactions can be terminated by hydrogen, so care must be taken to avoid any excess hydrogen gas in the ethylene or catalyst bed (particularly avoid water gas shift). The reactions normally occur in a solvent which does not react with the catalysts; this allows the catalyst active sites to remain exposed as the polymer molecules are carried away. Details about separation of metallocene from solvent appear to be kept secret, but supported catalyst in solvent should be straightforward as a continuous process.

 Solvents are a tricky question. The ideal solvent will be an organic oil which can be extracted from biomass, can dissolve PE, boils above 150 °C, does not thermally polymerize below that temperature and is nontoxic. Orange oil (mixed terpenes) fit that description, but the yield of terpene per m² of growing area is so low that it is disqualified for use in space. Proven solvents are xylene and toluene. This is an input that requires additional research; plant oils, silicone oils and possibly alcohols should be examined. Prototype production of PE could use Earth-sourced solvents while demonstrating the process is feasible, as could projects with a specific mass of plastic as a goal (early tethers for example).

 The product of this polymerization process is purified to contain only long-chain polymer and solvent. If necessary this can be done by centrifuge but the proportion of shorter chains and branches should be very low with these catalysts. Solvent is removed until the concentration of polymer is around 20% by mass. This results in a gel which is loaded into a ram extruder or similar heat and pressure device with spinneret holes. As the gel is passed through these holes the molecules are drawn into alignment; the resulting gel fibers are cooled and passed through water or ethanol to gradually remove the rest of the solvent as the fiber is drawn further. This gel spinning causes a very high degree of alignment and crystallization and can even reduce lattice defects; this is the secret of the incredibly high strength of Spectra fibers. The fiber is eventually wound onto a bobbin and then heat treated to drive off any remaining solvent and to further improve strength. Individual fibers are woven into yarn which is then used as needed. Again, fibers that will be exposed to space or to monatomic oxygen (low-Earth orbit) should be coated with a protective layer such as vapor deposited aluminum or a UV and oxygen resistant polymer film.

 For bulk use the freshly made polymer will have all solvent removed, yielding a powder that can be pressed into pellets for later use or pressed directly into shape. The powder can be melted under inert gas or redissolved in solvent and cast or extruded into the necessary shapes; pellets can sometimes be difficult to redissolve without shredding or patience.

 The bulk plastic is suitable for cutting boards, artificial joints, low-friction or low-wear contact surfaces, storage containers for water or moderate acids / bases, lightweight mechanical parts like rollers, cams, gears, etc., etc. Extruded rods can be used in 3d prototyping machines for additive manufacturing.

 The fiber is suitable for composite overwrap pressure vessels, tensile reinforcing members (including in regolith blocks), habitat hulls, meteoroid hull patches, cut-resistant cloth, ballistic armor, sutures and space tether strands.

Actually doing any of this would require the services of a good process chemist / chemical engineer at the least (plus possibly other engineers) to set up the various reactions, required equipment and input streams. Many of these processes if operated in batch mode will have unreacted or partially reacted inputs, and all of the processes will have some byproducts; these materials will need to be destroyed, most probably in a wet gasifier (supercritical water + O2 reactor) to recover the C, H and O. Any trapped catalyst material will find itself in the ash/salts, so any metals in the waste stream will end up as oxides or chlorides. Because the inputs are generated slowly, the overall process does not need to be particularly time-efficient as long as it is reliable, low-maintenance and low-mass-loss. For edge cases where a large supply of water and methane or CO2 are available a different solution might be used that takes less time but more manual effort.

Space Concrete


Lunarcrete, also known as "mooncrete", an idea first proposed by Larry A. Beyer of the University of Pittsburgh in 1985, is a hypothetical aggregate building material, similar to concrete, formed from lunar regolith, that would reduce the construction costs of building on the Moon.


Only comparatively small amounts of moon rock have been transported to Earth, so in 1988 researchers at the University of North Dakota proposed simulating the construction of such a material by using lignite coal ash. Other researchers have used the subsequently developed lunar regolith simulant materials, such as JSC-1 (developed in 1994 and as used by Toutanji et al.). Some small-scale testing, with actual regolith, has been performed in laboratories, however.

The basic ingredients for lunarcrete would be the same as those for terrestrial concrete: aggregate, water, and cement. In the case of lunarcrete, the aggregate would be lunar regolith. The cement would be manufactured by beneficiating lunar rock that had a high calcium content. Water would either be supplied from off the moon, or by combining oxygen with hydrogen produced from lunar soil.

Lin et al. used 40g of the lunar regolith samples obtained by Apollo 16 to produce lunarcrete in 1986. The lunarcrete was cured by using steam on a dry aggregate/cement mixture. Lin proposed that the water for such steam could be produced by mixing hydrogen with lunar ilmenite at 800 °C, to produce titanium oxide, iron, and water. It was capable of withstanding compressive pressures of 75 MPa, and lost only 20% of that strength after repeated exposure to vacuum.

In 2008, Houssam Toutanji, of the University of Alabama in Huntsville, and Richard Grugel, of the Marshall Space Flight Center, used a lunar soil simulant to determine whether lunarcrete could be made without water, using sulfur (obtainable from lunar dust) as the binding agent. The process to create this sulfur concrete required heating the sulfur to 130–140 °C. After exposure to 50 cycles of temperature changes, from -27 °C to room temperature, the simulant lunarcrete was found to be capable of withstanding compressive pressures of 17MPa, which Toutanji and Grugel believed could be raised to 20MPa if the material were reinforced with silica (also obtainable from lunar dust).

Casting and production

There would need to be significant infrastructure in place before industrial scale production of lunarcrete could be possible.

The casting of lunarcrete would require a pressurized environment, because attempting to cast in a vacuum would simply result in the water sublimating, and the lunarcrete failing to harden. Two solutions to this problem have been proposed: premixing the aggregate and the cement and then using a steam injection process to add the water, or the use of a pressurized concrete fabrication plant that produces pre-cast concrete blocks.

Lunarcrete shares the same lack of tensile strength as terrestrial concrete. One suggested lunar equivalent tensioning material for creating pre-stressed concrete is lunar glass, also formed from regolith, much as fibreglass is already sometimes used as a terrestrial concrete reinforcement material. Another tensioning material, suggested by David Bennett, is Kevlar, imported from Earth (which would be cheaper, in terms of mass, to import from Earth than conventional steel).

Sulfur based "Waterless Concrete"

This proposal is based on the observation that water is likely to be a precious commodity on the Moon. Also sulfur gains strength in a very short time and doesn't need any period of cooling, unlike hydraulic cement. This would reduce the time that human astronauts would need to be exposed to the surface lunar environment.

Sulfur is present on the moon in the form of the mineral troilite, (FeS) and could be reduced to obtain sulfur. It also doesn't require the ultra high temperatures needed for extraction of cementitious components (e.g. anorthosites).

"Sulfur "concrete" is an established construction material. Strictly speaking it isn't a concrete as there is little by way of chemical reaction. Instead the sulfur acts as a thermoplastic material binding with a non reactive substrate. Cement and water are not required. The concrete doesn't have to be cured, instead it is simply heated to above the melting point of sulfur, 140 °C, and after cooling it reaches high strength immediately.

The best mixture for tensile and compressive strength is 65% JSC-1 lunar regolith simulant and 35% sulfur, with an average compressive strength of 33.8 MPa and tensile strength of 3.7 MPa. Addition of 2% metal fiber increase the compressive strength to 43.0 MPa Addition of silica also increases the strength of the concrete.

This sulfur concrete could be of especial value for dust minimization, for instance to create a launching pad for rockets leaving the Moonp>

Issues for "Sulfur Concrete"

It provides less protection from cosmic radiation, so walls would need to be thicker than concrete walls (the water in concrete is an especially good absorber of cosmic radiation).

Sulfur melts at 115.2 °C, and lunar temperatures in high latitudes can reach 123 Celsius at midday. In addition, the temperature changes could change the volume of the sulfur concrete due to polymorphic transitions in the sulfur. (see Allotropes of sulfur).

So unprotected sulfur concrete on the Moon, if directly exposed to the surface temperatures, would need to be limited to higher latitudes or shaded locations with maximum temperatures less than 96 °C and monthly variations not exceeding 114 °C.

The material would degrade through repeated temperature cycles, but the effects are likely to be less extreme on the Moon due to the slowness of the monthly temperature cycle. The outer few millimeters may be damaged through sputtering from impact of high energy particles from the solar wind and solar flares. This may however be easy to repair, by reheating or recoating the surface layers in order to sinter away cracks and heal the damage.


David Bennett, of the British Cement Association, argues that lunarcrete has the following advantages as a construction material for lunar bases:

  • Lunarcrete production would require less energy than lunar production of steel, aluminium, or brick.
  • It is unaffected by temperature variations of +120 °C to −150 °C.
  • It will absorb gamma rays.
  • Material integrity is not affected by prolonged exposure to vacuum. Although free water will evaporate from the material, the water that is chemically bound as a result of the curing process will not.

He observes, however, that lunarcrete is not an airtight material, and to make it airtight would require the application of an epoxy coating to the interior of any lunarcrete structure.

Bennett suggests that hypothetical lunar buildings made of lunarcrete would most likely use a low-grade concrete block for interior compartments and rooms, and a high-grade dense silica particle cement-based concrete for exterior skins.

From the Wikipedia entry for LUNARCRETE


What sort of space clothing will space colonists wear? Something lightweight, to save on mass. No spandex, please.

Clothing is difficult to manufacture in microgravity, from growing the plant fibers to spinning, weaving, dying, and tailoring. All of those processes are much more difficult when things are floating around. This will limit the supply of available clothing, and make them expensive.

On the ISS, the crew wears garments made of cotton. These have a tendency to shed lint which can clog up ISS machinery and air filters. They are experimenting with Merino wool shirts and polyester shorts, which are lighter and do not shed lint.

The clothing might be treated with anti-microbial agents to make them odour resistant, since a microgravity clothes washer is so problematic that the ISS does not have one. On the ISS, clothing is worn and re-worn without washing until they get too stinky. Then they are put on the next cargo supply ship to burn up in re-entry. Actually, in microgravity, clothing does not actually touch the wearer's body as much as it does under Terra's gravity. For a crew of six, the ISS requires about 400 kilograms of clothing per year.

In classic Star Trek, the laundry renders the clothing back down to its chemical components, filters out the dirt, then refabricates the clothing. Nowadays we would think in terms of a 3D printer. Later versions of Star Trek would use unobtainium "replicators", but they have unintended consequences.

There are two basic ways to enable textiles to kill microbes. The first is to coat the fabric in a liquid solution that contains metals like silver ions; metal oxides like copper oxide; or compounds of ammonium. The other way is to impregnate the threads themselves with these kind of antimicrobial agents. Some testers said that the clothing would not stink, but it did tend to get noticeably heavier the more times it was worn. Presumably from the accumulation of perspiration and cast-off skin cells.

The ISS solution of "rely upon resupply from Terra" for the clothing problem won't work for a Mars Mission. Terra will be too far away, so you'll have to carry all the required clothing. In and effort to reduce the clothing payload NASA commissioned the UMPQUA Research Company in 2011 to produce the Advanced Microgravity Compatible Integrated Laundry System. The prototype worked on a vomit comet test flight, but UMPQUA is trying reduce the unit's water and power supply requirements.


The Advanced Microgravity Compatible, Integrated Laundry (AMCIL) is a microgravity compatible liquid / liquid vapor, two-phase laundry system with water jet agitation and vacuum assisted drying.

Umpqua Research Company previously developed a complete microgravity compatible Single Phase Laundry System (SPLS). Single-phase operation during the wash cycle facilitated microgravity compatible fluidics and eliminated problems associated with foams. Pulsed water jets were utilized to agitate the clothing. Drying was achieved with microwave assisted vacuum drying followed by a tumble cycle that greatly enhanced softness in the previously vacuum pressed clothing. Tumbling was achieved by an array of three air jets, two to generate a cyclonic effect and a third to induce tumbling by blowing perpendicular to the plane of rotation. This concept was successfully demonstrated during a KC-135 microgravity simulation flight.

The proposed AMCIL concept will build on the SPLS technology and incorporate key design improvements to reduced water requirements and lower power consumption. Specific advancements include a redesigned wash cycle that consumes less water and reduces power demand.

The Phase I effort will demonstrate the feasibility of the microgravity compatible liquid / liquid vapor, two-phase washing concept in a laboratory scale system. A complete, automated prototype unit that incorporates the system parameters established during the Phase I tests will be designed, fabricated, and tested during the Phase II program.

Skirts or kilts are discouraged because [a] it is difficult to impossible to keep them in a modest position in free fall, and [b] if the decks are open gratings instead of solid floors, people on the next deck down will be treated to an up-skirt view. No panchira allowed.

NASA ISS astronauts wear clothes with lots of pockets and strips of velcro, as a handy place to carry gear.

In Larry Niven's Protector, the Belters of the asteroid belt spend most of their lives inside their space suit. They have a tendency to paint their suits in extravagant colors. One of the characters had Salvador Dali's Madonna of Port Lligat on the front of their suit. In an interesting psychological quirk, Belters also tend to be nudists when in a pressurized environment. This could also be a response to the difficulty of making clothing, or a reaction to the how expensive clothing is.


I'd waived clearance while still under ascent thrust on our original trajectory to a 200-kilometer parking orbit. Our delta-vee margin was excellent even though the Tomahok was running with a full cargo bay of—would you believe it?—cotton underwear.

Clothing wears out, and we hadn't established any clothing industry in space yet. Spinning, weaving, dyeing, and tailoring are ancient technologies, but they were among the last to be adapted to the weightlessness of space. As for cotton, one of the Commonwealth's primary products, nobody has yet developed an artificial fiber quite as comfortable.

We had a lot of leeway in changing our flight path because the Tomahok had "bulked-out" before she "grossed-out"—the hold was filled long before maximum weight was attained.

From MANNA by Lee Correy (G. Harry Stine) 1983

APPAREL. The clothing worn in most of the KNOWN GALAXY, at least that worn by EARTH HUMANS, is for the most part extremely dull, or in very bad taste. Usually both. At least, this is the case in HOLLYWOOD SCIFI, and so far as I can tell from book covers, in most written SF as well. The general norm, especially for advanced societies, is essentially long underwear; the most common alternative is a jumpsuit, equally unflattering and harder to get into or (especially) out of.  These may be tarted up - as in the era c. 2000 CE - with racing stripes, corporate-logo-style swooshes, and so forth. But no matter what you do to them, basically they are all butt-ugly. To be sure, a babelicious actress will still look good, especially since her outfit is invariably skin-tight and low-cut. But she'd look good in anything, and even better in a more flattering costume.

Things are slightly better when WARFARE is involved (which may be why it is so common). Uniforms tend to follow 20th century CE practice, more or less, and so are at least crisp if still basically long underwear. Original Trek did go boldly where no one has gone since, putting the female crew members in those miniskirts. Alas, the feminists did away with that. Their logic might be impeccable, as Spock would say, but 'tis still a pity.

The one social system in the Known Galaxy that allows people to actually look good is NEOFEUDALISM. In Neofeudalist cultures (at least in the ruling class), the men get to wear that most dramatic of male costume accessories, a sword, while the women are all a major eyeful in long, tight, low-cut dresses. There is simply no way to look better without looking tacky. This of course is achieved in the final, decadent stages of the FIRST EMPIRE, when the women - at least those of the Imperial Court - run around looking like the Victoria's Secret catalog. But when you see that much flesh on display, you know that the FALL OF EMPIRE is at hand.

On the whole, ALIENS WITH FOREHEAD RIDGES get to dress better than Earth Humans. The same odd rule applies as with Earth Humans, though; on the whole, the more civilized they are the worse they dress. In general, Space SF Apparel is in a bad way. Give us some help here, people! With at least billions, maybe trillions of intelligent, civilized beings throughout the Known Galaxy, someone ought to be able to come up with a few decent outfits.


Space Clothes: Averted; even in space, people just wear regular clothes. (Sure, they have lots of pockets, but that’s not specific to spacer culture.) The only difference is that the pure-skirt option is eliminated for both sexes (because microgravity), and the cloaks have to come with MEMS and occasional microfan thrusters to let them manage themselves as people move.

And spandex is not used for regular, day-to-day clothing anywhere. Even not in space.


 One of the basic necessities not yet mentioned is clothing.

 Most clothing is made, not surprisingly, of cloth. That in turn is made of woven threads, which are made either of plastic, animal hair or plant fiber.

 I'm going to eliminate animal fibers simply on an efficiency basis. The varieties of animals that are raised for fur (sheep, rabbits, goats, yaks) can also produce meat and milk, but are much less efficient than purpose-bred varieties. Sheep are probably the best all-round performers (~5.4kg wool per animal per year eating about 2kg/day of feed), but we can still do much better than that. Of course any incidental fur, skin, etc. will be used for filling, lining, leather and such, but we cannot assume there will be enough of that material to clothe everyone.

Read on for the rest. This turned out to require a lot more growing space than I would have thought, 10.26m² per person.

 Plastic has many benefits. Some routes to plastic production don't involve living organisms as a bottleneck. Others use byproducts of food production. Depending on the choice of plastic the resulting fabric can be quite strong, durable and chemical-resistant. Dyes can be incorporated directly into the fibers for simpler, more durable coloring. Plastics can also have drawbacks like static buildup or melting, and tend to be degraded by UV exposure.
 On Earth, the main clothing fibers are nylonpolyurethane (as Spandex), acrylicrayon and polyester. Nylon and polyurethane are fully synthetic, typically at the end of a long chain of processes that start with benzene. Acrylic is also fully synthetic, most commonly encountered as cheap knitting yarn. Rayon is a cellulose polymer that typically starts life as wood or bamboo fiber; it is considered semisynthetic even though it is just as heavily processed as nylon. Polyester refers to a family of plastics, some of which are found in nature. Notable polyesters include PET (PET as Dacron, BoPET as Mylar), Vectran and PLA.
 Notice that none of those are my favorite plastic, polyethylene. I suspect PE fabric for clothing would be uncomfortable, with no stretch and a slightly oily feel. Excellent as an outer layer in a protective garment but terrible for underwear.

 Plant fibers also have many benefits. Softness and durability are at the forefront. Natural fibers tend to withstand flexing better than synthetic fibers. These tend to char rather than melt. They also have a softer feel. On the other hand, natural fibers are more difficult to dye and can be more labor-intensive to produce.
 On Earth the main clothing fibers are cotton, flax (linen) and hemp. All three are grown for their fibers and seeds; the seeds can be eaten, milled into flour or pressed for oil. All three are suitable for hydroponic cultivation, mechanical harvesting and mechanical processing.

 Regardless of type, the various fibers are spun into yarns. Often the yarn is composed of several different fibers in order to combine desirable properties. For example, it is very common to include a few percent Spandex with cotton or nylon to produce a yarn with some elastic response.

 From yarn, some types of clothing are knitted directly. Machine-knit sweaters and socks are common. Other types require that the yarn is woven into fabric, which is then cut and sewn. One key variable is the weight of the fabric, typically specified in ounces per yard or grams per square meter. I'll be using GSM / grams per square meter. For example, a thin t-shirt might use 100 gsm material while a resort hotel might offer super-thick 800 gsm bath towels. I've used values below that are in the middle of the range for each fabric type.

 Fabric amounts are handled oddly in the US. People specify some number of yards of length, but often fail to mention that it's not square yards. Fabric is typically sold in widths of 45" or 60" (sometimes 32"). If a pattern calls for 2 yards of 45" fabric, that's actually 2.5 square yards. I've listed values below in square meters. I used a variety of sources; there was one excellent sewing blog with tables for the first three items, then I found a pattern for coveralls. For the bath and bedroom items I used actual dimensions, added an allowance for hems and converted to metric.

Typical fabric requirements:
pants, 1.5-4.2m² (2.5m² avg.) x 250gsm = 625g
shirt, 0.7-3.4m² (2m² avg.) x 150gsm = 300g
dress, 1.3-7.7m² (3m² avg) x 200gsm = 600g
coveralls, 4.3-6m² (5.3m² avg.) x 350gsm = 1855g
sheet (queen): 6m² x 150gsm = 900g
sheet (full): 5m² x 150gsm = 750g
blanket (single-layer fleece): 7m² (90x110"/ 230x280cm) x 350gsm = 2450g
quilt (2-layer without filling): 14m² (90x110"/ 230x280cm) x 200gsm = 2800g
pillowcase: 1.4m² x 150gsm = 210g
napkin: 0.4m² x 200gsm = 80g
towel (face / washcloth): 0.1m² x 350gsm = 35g
towel (hand): 0.4m² x 350gsm = 140g
towel (bath): 0.9m² x 500gsm  = 450g (also worth a read)

 Let's assume each person has a full set of bedding and bath linens, a blanket, a napkin and one week of clothing. The linens come to 20.2m² of various weights, 4.865kg. Clothing depends a lot on the person's size, preference and occupation; I will add the first four values and divide by three to get an 'average' mass for a day's clothing. This is likely to be high as I doubt that a third of the crew will need heavy denim coveralls for daily work. Still, that comes to 29.9m² or 7.887kg for seven outfits. That's 12.75kg in total; add a bit of leeway for knits and undergarments (~1.5kg), thread, sizing, etc. and call it 15kg per person. Specifics may differ; I'm assuming a full-size bed and all single people. A couple could use the same sheet and bathroom set. A more regimented facility might use Navy-style hot bunks and hot air drying after bathing to cut most of the linens. I suppose wealthy tourists might want more amenities.

 These things wear out. Socks and undergarments typically last perhaps half a year. Outerwear lasts 1-3 years depending on circumstances, so let's use one year. Bedding and bath items can last many years, but let's call it three. Heavy-duty work outfits like denim coveralls might last a decade or might wear out in three months; call it one year. On an annual basis using these numbers each person needs about 12.5kg of replacement fabric. These estimates are a bit conservative; many people replace their clothing far less often than this and only when they are actually worn through. I assume that the 'replaced' garments may not necessarily be discarded and people may simply build up a wardrobe over time. Sufficient space could be available to store 2-3 weeks worth of clothing, while worn or damaged pieces would be used as rags or as fiber sources for filter paper.

 Let's look at yields. I simply don't have enough information available to predict the material requirements for plastics, so this will focus only on natural fibers.

 Cotton can be grown at 1000-1500 lb per acre in open fields. In a hydroponic environment with no pests and tight nutrient control it should be possible to significantly exceed that mark, but let's use 1500lb/ac for this estimate. 4047m² per acre gives us about 0.37lb per m² or about 168g/m². Estimates range from 150-180 days for a growth cycle, so let's use 165 days. That works out to almost exactly 1 gram per square meter per day. Each person needs 34.25 grams per day, which would require 34.25m² per person. If we use a record yield of 6.31 bales per acre, that would be 3,536kg/ha or 354 grams per m² or 2.15g/m² per day > ~16m² per person. Seed production is about 1.62 x cotton production, or 3.48g/m² per day.
  Flax can be grown to yield over 1800kg/ha or 186g/m². Growth cycle is 90-125 days (in Canada), so we will use 108 days. That gives 1.72g/m² per day or 19.89m² per person.
 Hemp has yielded 6 tonnes of fiber per hectare or 600g/m² (again, Canada). Growth cycle is 70-90 days for fiber only (80) or 110-150 days (130) for dual crop. Using the dual crop number we get 4.62g/m² per day or 7.4m² per person. Seed production is about 0.7g/m² per day.

 Based on those numbers it sounds like a mix of 2:1 hemp and cotton would be ideal. That would be 4.93m² per person of hemp and 5.33m² per person of cotton to produce a total of 12.5kg of fiber. The process would co-produce about 1.25kg of hempseed and 6.77kg of cottonseed plus another few kg of plant waste.

It's worth mentioning that the record land yields tend to be twice the high averages, if not more, for most crops; even so, hydroponic methods can often surpass the record yields simply by preventing stress. Crops that have not been optimized for performance (like flax and hemp) have the potential to double or triple their yields given a dedicated breeding project. Have a look at dwarf rice and wheat yields vs. the varieties that existed before the 60's for an example of this in action. In other words, within a decade any number I post here will be obsolete as long as someone is actively developing the potential of these species. I think a combination of longer 'useful life' assumptions for clothing and improved hydroponic yields could cut the required area down below 3m² per person. That research and breeding could be applied to commercial crops on the ground, providing improved incomes for farmers around the world.

Bamboo has bast fibers, similar to flax and hemp. Most things referred to as 'bamboo fiber' are actually rayon made with bamboo as a feedstock, but true bamboo fiber is possible. The raw material is high in lignin, so processing is often a combination of mechanical chopping and chemical or enzyme boosted bacterial retting. Lots more details here:

The tenacity of those fibers is less than half that of cotton. The resulting cloth won't be as durable or tough, but still falling between wool and rayon. That is to say, still useful and with a reportedly pleasant feel.

The yield of bamboo basts can be as high as 53 tonnes per hectare (5.365kg/m² or 14.7g/m² per day). As long as the net fiber yield is at least 15% of the gross bast mass then it is competitive with cotton. If it is over 31% then it is competitive with hemp.

yield source:

If we look back a ways (1909), at least one author noted yields as high as 44 tons per acre (an eye-popping 98.6 tonnes per hectare) and fiber yields as high as 44%.

source: Congressional Serial Set: pulp and paper investigation hearings. 1 January 1909. (available free)

Let's go with the modern optimistic yield (while noting that high-intensity hydroponics can almost certainly double that value) and a fiber yield of, say, 38%. That would give a fiber yield of 5.6g/m² per day or about 6.1m² per person. The plants require a three-year lead time and a third of the stand is harvested each year. Waste from this process would be suitable for paper or fuel alcohol.

I think the main drawback would be that bamboo grows very tall. A dwarf species could be found that grows to 4m after three years, but it's not certain the yield numbers would still apply. Even so, that's about 25m³ per person. Cotton by contrast grows to perhaps 130cm. Allowing 20cm for lighting and nutrient systems, that same 4m space could house two stacked crops. If a mild dwarf variety of cotton was developed that matured to 110cm or less, three stacked crops could occupy the same space and would become competitive again on a floor-space and volume basis.

Another drawback is that bamboo requires several years to develop for this purpose. Peak fiber yields occur at three years. Peak structural strength is typically seen around 5 years. For paper pulp or wattle it can be taken at 1-2 years.

Those drawbacks are certainly opposed by several advantages unique to bamboo. It's a structural material, can be used similar to wood (buttons, flooring, furniture) and resists bacterial and fungal attack. Bamboo resists high-pH environments and can be embedded in concrete; it could serve as the tension member in a reinforced regolith-block construction if metal is scarce.

John Powell: Beta cloth is also a good candidate for durable outer wear. It's non-flammable, completely recyclable and made from silica fibers, a major component of lunar regolith. The Apollo/Skylab spacesuits used it.

Chris Wolfe: Excellent idea. I'd probably not want to wear that against the skin and there's a potential inhalation hazard from shed fiber fragments, but as an outer layer with heat and chemical resistance it would be very useful for engineering coveralls. Equipment to make silica fibers would also be useful for making rockwool insulation and rooting media.


Hyperpower Stations

There are just some industrial applications that demand power approaching Kardashev Type I levels. Hyperpower stations will supply you with massive amounts of power (along with a massive electricity bill).

At the orbital radius of the planet Mercury the solar flux is about 9,121 watts per square meter, a whopping 6.7 times the 1,366 W/m2 available at Terra's orbital radius. So a ten kilometer square solar photovoltaic array that was 100% efficient would crank out about one terawatt of power.

Titanic solar power stations covering huge areas on the surface of Mercury or Luna are called "Asimov Arrays", name bestowed by James Powell and Charles Pellegrino after Isaac Asimov pointed out several serious errors in their design. Such as "You do know that Mercury is not tidally braked with respect to the Sun, do you not?"

Do keep in mind that it is not mandatory for the solar cells to be mounted on Mercury, they can be orbital. You could even place them closer to the sun if you really need the power. The only problem is that light pressure will tend to push them away, Mercury's gravity can anchor them.
Vulcanoids are a hypothetical population of asteroids that orbit the Sun in a dynamically stable zone inside the orbit of the planet Mercury. No astronomer has ever discovered any, but admittedly they would be rather hard to observe. They wouild not have the total surface area of a Mercury Asimov array, but [a] they would be closer to Sol and [b] if enemy nations(s) held claim(s) to the entire surface of Mercury, vulcanoids would be a worth-while alternate site.
An Asimov Array of solar power stations around the lunar equator could supply the all the energy needs of inhabited Terra. The power would be beamed to Terra using microwaves.
There is 2.0 × 1013 watts (20 terawatts) potential between Jupiter and Io. This can be harvested with electrodynamic tethers.
Alternatively, you mount lasers on copper rods and launch them from Io at Jupiter. As the rods cut the magnetic lines of force they generate electricity. This is converted into laser light and beamed back to Io. Rod is destroyed when it hits Jupiter, but so what, they are cheap.
Saturn, Uranus, and Neptune have atmospheres rich in Helium-3, useful for 3He+D fueled fusion reactors (although there is some evidence that Saturn only has 1/5th the 3He of the others). This can be harvested by atmospheric scooping. Jupiter has 3He as well, but the heavy gravity makes it uneconomical to harvest. You need a freaking solid core NTR to boost the harvest into Jovian orbit.
Naturally huge arrays of fusion power plants are going to require a huge supply of fusion fuel nearby.

“Getting the power may not cost us that much after aIl,” said Tuna ("Richard Tuna" is actually Charles Pelligrino). “Not when you consider where computer science and robotics are headed during the next fifty to seventy years. A few days ago, at Brookhaven, we came to realize that it may cost us only the expense of developing about thirty small, self-replicating factories—which build factories, which build factories—which, when they reach a certain population density, switch over from building factories to building solar panels. We simply send them like a viral infection tolthe planet Mercury, and carpet one hemisphere with panels. You’d get more than fifty thousand times the U.S. energy budget there.”

“Mercury rotates!” Colby called out.


“Sorry, Richie,” Colby said, “but you can’t build your panels on one hemisphere only, because Mercury rotates. Where have you been? People have known that for ten years. I’m sure it rotates. Have I introduced you to the natural resource? Ask him.”

“He’s right,” said Dr. Isaac Asimov. “Mercury rotates with aperiod of about three months, and the energy received per square foot, when Mercury is most distant from the Sun, is seven times what Earth receives. It goes up to ten times during closest approach. The interesting thing is that the one-eighty-degree and zero-degree longitudes do become gravitationally locked, alternately, during apihelion, and are exposed to the Sun almost three times longer than the longitudes ninety degrees away from them.”

“Oh, no,” Tuna groaned, flushing with embarrassment. “I don’t believe it. We have to redesign the whole thing.”

“Please,” Asimov said, raising his hands above his head, as if to show that he bore no weapons. “Don’t blame me. I didn’t make Mercury rotate. Better to find out now than when you get there and look up in the sky and—‘Hey! Why is the Sun moving?’ ”

Tuna groaned. “I don’t believe I missed that. We can redesign it, though. We’ll just have to cover a bit more surface area, and perhaps send three times as many machines to get the project started … make sure at least one cluster of them is in sunshine at any given moment…”

“And you’ll certainly want to test and perfect the machines on the Moon first,” added Asimov. “You know, it’s just one more argument for building a permanent Moon base. By the time you perfect solar panel builders for Mercury, you’ll already be beaming large quantities of clean energy down to Earth from the Moon…” He paused and smiled. “Incidentally, I wrote a science fiction story, way back in 1940, about an interrupted array of panels around the Moon’s equator (I have yet to figure out which story this is. The closest I can find is Reason). So if you ever do build the thing, Richard, you can call it the Asimov Array.”

“We can?”

“I insist on it.”

(ed note: The following is from the technical appendix to the novel.

Keep in mind that this was written in 1993 so adjust US dollars and national power consumption for inflation)

The technology for producing antimatter using particle accelerators is presently under development at American and European laboratories. At CERN’s seven-kilometer-circumference synchrotron near Geneva, Switzerland, antiprotons are routinely produced by firing a high-energy beam of protons into a block of tungsten. A trillion (1012) antiprotons can be created in this way. A trillion antiprotons may sound like a lot, but they contain the potential annihilation energy of only three hundred joules (roughly equivalent to the “bang” from a cap gun), and the CERN facility gets slapped with a $40,000 electric bill every time the accelerator is turned on (more like $68,000 US in year 2017).

Clearly, simpler and more efficient accelerators are needed. Machines with the proper requirements are presently under development in the United States (and soon to be under intensive development in Japan) for use in fusion reactor research.

“As an example,” explains physicist George Mueller, “in one design being studied, the particle accelerator will produce short bursts of protons with a power beam of 1014 watts, about one hundred times the present power output of the entire world! (in 2013 the world's average energy consuption was about 12.3×1012 watts, 1014 is still one hundred times as much) Of course, since the machine will be operated in 10-8-second bursts, the average power is very much lower.”

The natural location for antimatter factories, in view of their large power requirements, is in space, where continuous and, from an industrial perspective, limitless solar power is available. “Using the solar flux at the Earth’s distance from the Sun,” adds Mueller, “a light collector about three hundred kilometers on a side could provide the power for a 1014-watt factory (9×1010 m2. Solar flux at Terra orbit is 1,366 W/m2. At 100% efficiency that is 1.2×1014 watts).

If the efficiency of antiproton production from each high-energy proton in the initial beam could be made as high as 0.1 percent (efficiency of 0.001.) [presently Hiroshi Takahashi is predicting higher efficiencies] (Dr. Robert Forward thinks realistically it will be more like 0.0001)

…then this machine would produce 1020 antiprotons per second (each antiproton requires 1.5×10-10 Joules, 1.2×1014 watts at efficiency of 0.001 can produce 7.98×1020 antiprotons per second),…

…or about one kilogram of antimatter per month.” (antiprotons have a mass of 1.7×10-27 kilograms. At a rate of 1020 antiprotons/sec 1 kilogram would take 69 days or 2.3 months)

From our earliest brainstorming sessions emerged proposals for a solar panel array, in orbit around Earth, covering an area in excess of ten thousand square kilometers. Even if it should one day become economically feasible to mine, refine, and transport materials from the Moon to Earth orbit, such an array would literally become a gigantic solar sail, requiring a considerable expenditure in thrust (presumably from rockets that would have to be refueled from somewhere) just to keep it from blowing away on the solar wind.

Our attention tumed elsewhere, to a power source more firmly anchored, yet overlooked, perhaps because it is so large that no one noticed it before. If we are correct, the planet Mercury is destined to become the most valuable piece of real estate in the solar system.

Presently, we are eyeing self-replicating, solar-panel-building machines. If humanity plays its cards right, prototypes could be tested on the Moon near 2020, and the rewards that the descendants of these first machines can bring—cheap, clean, and unlimited power for all mankind—are yet another argument for a permanent Moon base. Using the materials available at the lunar surface, they will build solar panel farms, and new solar-panel-building machines. In time, the farms will girdle the Moon’s equator to form the Asimov Array (named, exactly as described in Chapter 4, after an early contributor to the concept). The Asimov Array will provide power for Earth.

However, we dare not use that power for producing and storing large quantities of antimatter on the Moon, or anywhere near Earth, because even a single kilogram of the stuff—a mere handful—carries the explosive potential of forty hydrogen bombs, along with the moral responsibilities that go hand in hand with the possession of such power. (1 kilogram of antimatter + 1 kilogram of matter will make about 1.8×1017 joules, about 43 megatons. B83 nuclear bomb has highest yield of any in US nuclear arsenal, it has a maximum yield of 1.2 megatons. So 43 MT is about thirty-six hydrogen bombs)

Once perfected, the descendants of the original Asimov Array robots can be sent like a viral infection to the planet Mercury. Assembling replicas of themselves from the substance of their host, their first half decade of habitation will be a latent, incubation phase, during which most of the solar panels manufactured by the machines will be used to power an ever-accelerating chain reaction of machines building more self-replicating machines. As their population approaches a predetermined critical density, more and more of them cease reproduction and join to form solar panel factories, with the result that almost three decades after the arrival of the original twenty or thirty machines, uncountable square kilometers of generator, with an area the size of Rhode lsland being added daily.

When Mercury is farthest from the Sun, each panel will receive 6.7 times as much solar energy as it would receive on the surface of the Moon. This figure rises to fully ten times the lunar surface value as the planet’s eccentric orbit dips twenty-four million kilometers nearer the Sun. In time, self-replicating machines will carpet the Mercuran landscape from pole to pole with solar panels, giving mankind more than 50,000 times the present U.S. electrical energy budget, a power capable of launching at least two interstellar missions per year.(1990 U.S. annual electrical output 2.7×1016 Joules. ×50,000 = 1.3×1021 Joules. Divided by 2 per year = 6.7×1020 Joules = 7.5 kilogram antimatter per interstellar mission.)

Using self-replicators, the world’s future energy problems and even the excess energy required for relativistic flight can be solved for a very small initial investment: the cost of developing as few as a dozen ancestral machines on the Moon. Of course, we should not trouble ourselves to begin immediate development. They would be too expensive to build today, and too inefficient if built from the equipment now at hand—just as a trans-Atlantic airline service and videocassette recorders, though technologically feasible, would have been prohibitively expensive to build in 1925. We must wait, not only for technology to catch up with the idea, but for the idea to become economically viable.

From FLYING TO VALHALLA by Charles Pellegrino (1993)

The main dome of Ganymede City covered three square kilometers of the moon's surface. Here on the top level, the observation screens covered the interior of the dome; they could be turned on individually, or en masse to show a panorama of sky and surrounding terrain. A direct view would have left the observation level with too little shielding against the leakage of solar radiation trapped by Jupiter's magnetic field; even though Ganymede City sat in the moon's radiation shadow, the aboveground portion was protected, as an added precaution, by meters of water in the outer shell, piped in from the nearby ice field. Natives called Ganymede City "the big igloo,” because of the liquid that was kept frozen in its insulating space. In addition to the physical shielding against stray radiation and occasional meteors, the Laser-Fed Fusion Reactor powered the super conducting units which cast a magnetic shield over the domes.

Ganymede plowed through a sea of death; but despite this, ships had visited all the Galilean satellites by 2015. Built at the Martian space docks on Phobos and Deimos, the water- and magnetically-shielded tin cans, as the ships came to be called, had penetrated into Jupiter's radiation belts, setting up research bases on Callisto and Ganymede, as well as temporary facilities on a few of the close-in rocks whipping around the edges of the gas giant’s atmosphere.

To make power for building the first underground living quarters, the tin cans had deployed a giant sun mirror. The collector was no more than a few molecules thick, but its huge size and focusing capacity made up for the fact that the sun's intensity was only about four percent of what it was in the vicinity of earth (51 W/m2 instead of 1,366 W/m2).

While Ganymede City's first levels were being built, a mass driver track had been constructed beyond what was now the tug port. Using the three-kilometers-per-second escape velocity from the Jovian moon, the track began to toss copper ingots toward Jupiter, whose escape velocity was twenty times greater; this large energy difference was expressed in the form of eddy currents of electricity forming in the copper as it rushed through Jupiter's powerful magnetic field; these were lased back to Ganymede by a small disposable unit, continuing right up to the moment when the ingot hit the atmosphere for a final, dramatic surge of electricity. Current flow was evened out by storage facilities at the receiving station on Ganymede.

As a result of this and other systems, Ganymede became one of the energy-self-sufficient places for science, attracting research and development from earth. The solar mirror was still working; the lofter still threw ingots into Jove's face; and a second fusion LFR had recently been completed.

Ironically, Sam thought, success on Ganymede had slowed the building of facilities on Saturn's moons, as well as delaying development of the larger asteroids such as Ceres. A whole system of worlds waited to come alive out here, offering conditions for industry and research, room for a civilization to grow.

From MACROLIFE by George Zebrowski (1979)

Hyperpower Uses

Here are a few industrial applications that require hyperpower stations.

Interstellar Mission Laser Sail
     Such as in Rocheworld, which needed an outrageous 1,300 terawatts.
     Solar system wide network of laser power transmission and laser thermal rocket energizers.
Project Daedalus
     This slower-than-light unmanned starship would get up to 0.12 c and cruise for 46 years before flashing through the Barnard's Star system frantically snapping pictures. It would require 30,000 metric tons of Helium-3, harvested from Jupiter's atmosphere over a 20 year period. It also needs 20,000 metric tons of deuterium, but you can get that out of seawater.
Antimatter Creation
     Antimatter factories producing commercial quantities of antimatter, are hideously inefficient power hogs. But antimatter has a thousand and one uses, it will be a valuable commodity. In Michael McCollum's Thunderstrike antimatter is used as super-duper rocket fuel and to move valuable asteroids to more convenient locations. Pelligrino and Powell's Valkyrie and Frisbee's starship use antimatter as starship fuel.
     Antimatter distribution is administered by the Antimatter Guard because is it so much easier to misuse than mere plutonium..
Valkyrie Antimatter Starship
     These ultralight starships can deltaV up to 0.92c and back down to zero. But my slide rule says they'll need about 4,200 metric tons of antimatter.
Frisbee Antimatter Starship
     This brute can delta V up to 0.125c and back down to zero, with an acceleration of 0.01 g. And the freaking thing is 700 kilometers long (not meters, kilometers). It will require 159,450 metric tons of antimatter liquid hydrogen, because it ain't no ultralight starship. 500 kilometers of the ship is just heat radiators.

Fission Fuel Plant

Atomic Rockets need Atomic Fuel. Raw uranium or thorium ore is worthless as fuel for your nuclear thermal rocket or nuclear power reactor (the same goes for nuclear weapons). The stuff the asteroid miners haul in will have to be enriched before it can be used as fuel.

Common power reactors require enrichment from 1% to 20%, fast-neutron power reactors and nuclear thermal rockets need 20% to 85%, above that is the weapons-grade fissionables needed for nuclear weapons, SNRE-class propulsion, Orion pulse units, and nuclear salt water rockets burning 90% UTB.

Enrichment requires a sizable high-tech factory, they will have to be strategically placed around the inhabited solar system. Along with security forces provided by the astromilitary of a select group of nations, to ensure that none of the weapons-grade plutonium gets stolen (the Nuke Guard).

It is a lamentable fact that fission engine fuel elements clog up with nuclear poisons and stop working while there is still lots of fuel in them. After about 15% of the fuel is burnt (85% unburnt) the rod stops fissioning. Since is it a criminal waste of scarce fuel to throw the rod away when 85% is still yet to be used, you have to take it to a nuclear reprocessing plant. The plant will filter out all those nuclear poisons and use the unburnt fuel to make new fuel rods. A distressing by-product is lots of weapons-grade plutonium, which the Nuke Guard will also have to deal with.

Obviously reprocessing will only be needed for solid core and closed-cycle gas core NTRs. Other nuclear rockets blow the nuclear fuel out their tail pipes, burnt and unburnt.

There will have to be reprocessing plants strategically placed around the inhabited solar system, perhaps inside enrichment plants. Perhaps with a network of fuel transport ships shuttling fuel rods (fresh and spent) between plants and spaceports for convenience. Said ships will undoubtedly be a part of the Nuke Guard.

Aldrin Cyclers

A trip to Mars is very expensive in terms of propellant. Rockets are very sensitive to mass. Remember that Every Gram Counts.

The Mars mission requires hydroponics for food and air for the astronauts, nine months worth. The habitat module. And worst of all, the massive anti-radiation storm cellar. All of this takes mass. Then you have to add the mass for the lander and the other equipment you'll need on Mars. Just think about the propellant bill.

Then if you have a second expedition, you have to pay for it all again. And for each subsequent expedition.

About this time, astronautics experts had the thought "what if we could re-use some of the required equipment?" More specifically, re-use the delta-V.

Take the habitat module, the hydroponics, and the storm cellar and make it into a space station. Spend enough propellant to delta-V it up into an orbit that passes by Mars and eventually returns to Earth. It will regularly pass by Earth and Mars for the rest of eternity, with a little mid-course correction now and then. So you now have a habitat module delta-Ved for a Mars mission that can be re-used. It is a Cycler.

For your next Mars mission, you have a transfer vehicle that will carry the crew and mission specific payload. It rendezvous with the cycler, more or less paying the same delta-V cost as the start of a Mars mission. Except it only pays the propellant cost for the crew and the mission payload, it does not have to pay for the habitat module. You will be re-using the delta-V for the hab module by using the cycler. When the cycler passes by Mars, the transfer vehicle leaves the cycler and burns enough propellant (or aerobrakes in the Martian atmosphere) to delta-V into Mars orbit. The cycler goes on its merry way, still full of delta-V, still available for re-use by a future expedition.

Keep in mind that you still need the propellant for the people and mission payload. But saving the propellant needed for the habitat module is a huge help.

Understand that since a cycler is a clever way to reuse the delta V of the habitat module, the hydroponics, and the storm cellar, the implication is that a cycler is worthless for sending inert payloads to Mars. It will take the exact same amount of delta-V to send the inert payload to Mars regardless of whether you use the cycler or not, so what's the point? This is because inert payloads do not need habitat modules, hydroponics, nor storm cellars.

Hop David has computed the orbits for Earth-Asteroid cyclers, discovering the existence of virtual "railroad towns".

UCLA Cycler

UCLA Cycler
Storm Cellar15,000
x2 Crew
Refrig Cycle31
Reactor and
1,390 kg/m3)
x60 Ion
x16 Crew,

This is from Ion engine propelled Earth-Mars cycler with nuclear thermal propelled transfer vehicle. It is a preliminary study by California University School of Engineering and Applied Science.

The report makes a few assumptions:

  • There is a space station in LEO to be a base for construction of the cycler, and a rendezvous spot for the "taxi" (spacecraft that ferries astronauts to and from the cycler)
  • There is some kind of transportation system between Terra and the space station (a Space Shuttle or Soyuz spacecraft)
  • Previous missions has already established habitats on the Martian surface, as well as landing/launch pads for the taxi
  • Previous missions has already established an in-situ resource utilization plant to produce liquid hydrogen propellant for the NTR taxi. The cycler cannot a transport all the propellant the taxi needs, it has to refuel on Mars.
  • Previous missions have already established a fuel ship capable of transporting liquid hydrogen from the Martian ISRU plant to the taxi in low Mars orbit

The heart of a cycler system is the Cycle; that is, the orbit it follows.

The study looked at various orbits, trying to optimize for:

  • More frequent encounters between Mars and Terra
  • Smaller detal V angles and Terra and Mars approaches
  • Shorter stay time on the cycler
  • Easy predictability of the position of the cycler

Having just one cycler and rotating its orbit to meet the two planets seems attractive, but there are major drawbacks. The fuel required to rotate the orbit are expensive, about 85% the mass of the cycler. This requires constant refueling. Also since the cycler is not in a predictable orbit the motion will have to be constantly monitored and mid-course corrections applied. With no corrections the orbit error will propagate to future trips.

To deal with the predictability problem a proposed solution was to rotate the orbit every 2.143 years (the delay between times the relative positions of Mars and Terra repeat) by 51.429 degrees (360° / 7, giving 7 discrete orbits). This would cover the entire range with only seven passes. The orbits would be rotated by a burn performed at the closest approach to Terra in order to get a gravity assist. The drawback is that the fuel requirements would be about the same, and there would be periods of more than ten years before the cycler returned to Mars and allowed the Mars explorers to return to Terra.

So this option was rejected.

The Up/Down Escalator orbit was ruled out because: the Taxi would need excessive amounts of delta V to catch a ride and the orbit would have to go way further past Mars in order to encounter Mars on the inward swing (which drastically increases the cycler orbital period).

This option was rejected as well.

The report concluded that the optimum cycle was using three cyclers with VISIT-like orbits. One at zero degrees, one at +130° and one at -130° (230°). This allows squeezing the most mission into each 20 year period while optimizing the other factors.

In Table 2, row Cycler DELTA V (row 19) shows the taxi delta V needed to leave the cycler and enter close Mars orbit. This varies from 5.27 to 6.32 kilometers per second. Row Hyperbolic delta v (27) shows the taxi delta V needed to leave the cyclear and enter close Terra orbit. This varies from 9.49 to 10.46 km/s. They figure that to perform these maneuver the taxi will need a thrust of 5.639e+5 Newtons, which is good because the planned taxi engine will have a thrust of 6.98e+5N.

Taxi Requirements
ORBIT 1 Mars Approach
ΔV6.3152 km/s
Propellant16,108 kg
Burn Time378 s (6.3 min)
ORBIT 1 Terra Approach
ΔV9.4889 km/s
Propellant20,564.34 kg
Burn Time432.7 s (8.05 min)
ORBIT 2 & 3 Mars Approach
ΔV5.2707 km/s
Propellant14,220 kg
Burn Time333.78 s (5.56 min)
ORBIT 2 & 3 Terra Approach
ΔV10.4554 km/s
Propellant21,613 kg
Burn Time507.3 s (8.46 min)

Table 3 shows three Terra-Mars mission opportunities over an 18 year period. Trip 1 starts at year Zero, uses the zero degree cycler, and has a mission duration of 5.41 years. Trip 2 starts at year 4.75 and has a mission duration of 6.73 years. Trip 3 starts at year 14.89 and has a mission duration of 2.856 years.

The Reactor produces 10 MWe (electrical) power. The Power Conversion is a Stirling cycle with an efficiency of 0.254 so the reactor has to produce 40 MWth (heat). To reject waste heat 1,000 m2 of Heat Radiators operating at 1,000K are used.

The Storage / Experiment / Greenhouse module is above the hub. It contains space for microgravity experiments, food storage, and the life support reclamation systems. The hygiene/gray water reclamation system uses various filters, as well as Waldman's dark green lettuce in the greenhouse.

The cycler provides artificial gravity by spinning as a dependent centrifuge, where the spin axis is parallel to the thrust axis. The habitat modules are set at a radius of 50 meters from the spin axis, the spin rate is 2.32 rpm (at the nausea limit for the untrained), the resulting gravity is 0.3 g. The report assumes this will be enough gravity to prevent muscle atrophy, since it will be very hard to explore Mars if the astronauts are too weak to walk. For what it is worth the surface gravity of Mars is 0.376 g.

The bulk of the cycler's mass is on the spin axis (with the exception of the habitat modules) to make the smallest moment of inertia. This reduces the amount of reaction control jet fuel needed to spin up or spin down the cycler. The jets are located at the ends of each habitat module. The cycler must be despun for docking and releasing the taxi.

Each of the two Habitat Modules has two levels: command level above and residential level below.

The command level has the control/communication room, the kitchen, the communal room (including exercise equipment), and the infirmary. On such a multi-year mission a dedicated sickbay is needed. And two of the sixteen crew are doctors.

The residential level has the crew quarters, toilets and showers. Each crew member has their very own 2 x 3 meter private room, with bed and desk.

The Storm Cellar is located below the hub. It can hold all sixteen astronauts and is designed to ensure that a solar proton storm does not inflict a dose higher than 0.5 Sieverts. The astronauts are seated in semi-reclined chairs so they can sleep or do work, since the ceiling is too low to stand up (2.5 meters floor to ceiling).

Aluminum shielding instead of water was chosen due to ease of construction and maintenance. The shielding is 20 grams per square centimeter of aluminum (thickness of 7.4 centimeters). The largest proton storm ever recorded was the August 1972 solar event and the most harmful spectrum was the February 1956 solar event. If the cycler suffers a solar event with the duration and intensity of the 1972 event coupled with the deadly spectrum of the 1956 event the storm cellar will ensure the astronauts only suffer a dose of 0.43 SV.

The storm cellar has an expensive mass of 15,000 kilograms, but radiation shielding always has a painful amount of penalty mass.

The Communication Array is de-spun. It is mounted on a coupling with rings and brushes (perhaps this could be replaced by a Canfield Joint).

The Ion Thrusters use argon propellant. Each engine has a mass of 165 kg, a diameter of 0.85 m, a specific impulse of 10,000 sec, a propellant mass flow of 1.579E-3 kg, and produce 4.4 Newtons of thrust. The reactor produces 10 MW of electricity but for safety and to leave power for the rest of the ship only 9.5 MW are used by the engines. For the 130,000 kg cycler, 35 ion engines were deemed adequate. Since ion engines tend to fail, 60 engines are carried.

Ion Requirements
ΔV10.5 km/s
Propellant13,195 kg
Burn Time8,356,554.78 s (96 days 17 hours 15.9 minutes)
ORBIT 2 and 3
ΔV11.46 km/s
Propellant14,333 kg
Burn Time9,077,264.09 s (105 days 1 hour 27.7 minutes)

Stage 1
EngineSolid core
Isp836 s
Ve8,200 m/s
Thrust349,000 N
Mass Flow42.6 kg/s
Accel11.65 m/s2
Dry Mass11.65 m/s2
TOTAL21,614 kg
Stage 1
TOTAL8,386 kg
Wet Mass30,000
Taxi Requirements
ORBIT 1 Mars Approach
ΔV6.3152 km/s
Propellant16,108 kg
Burn Time378 s (6.3 min)
ORBIT 1 Terra Approach
ΔV9.4889 km/s
Propellant20,564.34 kg
Burn Time432.7 s (8.05 min)
ORBIT 2 & 3 Mars Approach
ΔV5.2707 km/s
Propellant14,220 kg
Burn Time333.78 s (5.56 min)
ORBIT 2 & 3 Terra Approach
ΔV10.4554 km/s
Propellant21,613 kg
Burn Time507.3 s (8.46 min)

The taxi has two stages: a nuclear powered first stage with a solid core NTR and a chemical powered second stage (based on a McDonnell Douglas DC-X).

Contrary to what you'd expect, the nuclear stage never lands on Mars. Its purpose is to ferry the chemical stage from the cycler (as is whizzes past Mars) to low Mars orbit. The chemical stage separates and lands on Mars while the nuclear stage stays in Mars parking orbit. It seems that the designers were hesitant to bath a part of the Martian surface with deadly radiation from the nuclear engine. It was also a challenge to protect the astronauts from getting a bad dose of radiation as they crawled down the ladder along the taxi's side to step on the Martian surface.

While the astronauts explore the Martian surface, a robot propellant transport containing a full load of ISRU liquid hydrogen blast off and refuels the nuclearr stage in parking orbit. The chemical stage on the surface also has its liquid hydrogen tanks topped off.

When the return cycler approaches, the astronauts blast off from Mars in the chemical stage, rendezvous with the nuclear stage, and use the nuclear engine to rendezvous with the cycler.

The report is very vague on the chemical stage, other than stating it has a maximum mass of 8,386 kg. Doing some back of the envelope calculations I figure it will need about 3,550 m/s of delta V to land or blast off from Mars. Using LH2/LOX chemical engines with 4,905 m/s of exhaust velocity, the chemical stage will need a mass ratio of 2.06 in order to produce enough delta V. If the wet mass is 8,386 kg, then the propellant mass is 4,315 kg and the dry mass is 4,071 kg.

I find the figures for the Taxi Requirements puzzling. It says the Orbit 2 Terra Approach burn requires 21,613 kg of propellant. However, if the total wet mass is 30,000 kg, minus the 8,386 kg for the second stage gives us a wet mass for the first stage of … 21,613 kg. Subtact the required propellant from that and you discover the dry mass of the first stage is zero. Which is impossible. I am re-reading the report to try and figure this out. It could be that they are assuming that at the Terra Approach Burn the chemical stage will have empty fuel tanks.

Business Opportunities

RocketCat sez

I'm not sure if it is the third or fourth oldest profession, but salesman/con-artist/uses-car-dealer/grifter is one of the oldest.

It warms the liquid-hydrogen cooled cockles of my so-called heart to see you innocent naive simpletons who believe that humans will somehow become all noble and altruistic in the glorious space frontier. But that's not the way to bet. As long as there are space folk with money out there, others will be endlessly trying to figure out how to transfer those credit coins from the folk's pockets into theirs.

Since credit transferal by blatantly illegal means is covered elsewhere, here we will talk about the more legal means. The start is to discover a "hole in the market", that is, some desirable product or service that space citizens are willing to buy with their hard-earned credits.

If you can find one that is actually new, so much the better. Just be sure to cash in quick because scummy low-life copy-cats will rapidly try to make cheap knock-offs of your product. Or you might be returning the favor to some other company's lucrative monopoly (in which case you are obviously not a scummy low-life copy-cat, nay you are a virtuous monopoly-buster).

I compiled the list below simply by looking for clever solutions to major problems faced by space dwellers, then asking the question "how can I make a buck off of this?"

And never forget the attractiveness of a one-stop solution.

Example: A rock-rat asteroid miner delta-Vees into Billstown to shop. Packages of disposable space suit diapers might be over in the clothing section. Anti-fogging space helmet moist towelette packets are way over there in utility goods. Suit maintenance tools are in the hardware department. Emergency puncture repair patches are in the repair section.

Both you and I know that the rock-rat ain't a gonna waste their time bouncing around the entire freaking store looking for all this crap. They will probably only put one or two of the items in their shopping drone, which means Bill is not extracting the maximum amount of moola from the rock-rat's wallet.

But what if the rock-rat walked into Billstown, and saw a stack of "Space-suit kits" by the entrance? A nice shrink-wrapped canister containing a pack of diapers, a couple of boxes of anti-fogging towelettes, a modest suit maintenance tool set, and a stack of puncture repair patches. All in one box at a low-low price. No walking all over the entire store required.

Bill has lowered the purchasing friction to a point where nine times out of ten the rock rat will buy the kit, thus buying all of those space suit products instead of just one or two. Bill is no longer leaving money on the table.

You may have encountered something like this at your local hardware store, say a kit of various cleaning products (a selection of soaps, detergents, sponges and brushes, all wrapped up in a cleaning bucket). The urge to purchase one is almost irresistible. A simple one-stop-shopping item, a "kit" with all you need in a single package; just grab it, walk to the checkout line and you are done. I actually saw somebody look at one of those kits and say "I want to buy this, but I don't know why!"

That's the magic of a one-stop solution. "It's a Kit!"

In his novel Going Postal, Writer Terry Pratchett put it this way: “(The Postmaster) made a mental note: envelopes with a stamp already on, and a sheet of folded paper inside them: Instant Letter Kit, Just Add Ink! That was an important rule of any game: always make it easy for people to give you money.”

An example of a kit is "Beams-R-Us" below. If they just sold laser time that's will get them a bit of money. But if they also rented beam-rider spacecraft (just like a U-Haul truck) and had beam-riding cargo transports riding their own beams like a railroad train riding on its owner's railroad track, well, "It's a Kit!". Beams-R-Us has become one-stop shopping for all your interplanetary shipping needs. They might even branch out and offer spacecraft purchase financing, and cargo transport insurance. Why go to five different companies when you can get it all done at Beams-R-Us?

As I've mentioned so many times you must be sick of it, 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. Once people are traveling in space, there will arise numerous business opportunities to sell things to traveling people.

Please note that none of these are MacGuffinite, they are not economic motivation for the colonization and industrialization of space. But once there are people in space, they become potential customers.

Science fiction authors should note that the presence of these various spacegoing corporations can lead to a very colorful background for their novels. Indeed, the history of how a given corporation got started could be an interesting series of stories. Things are raw and cut-throat on the space frontier, especially when the people starting the company are novices learning the ropes the hard way. Hilarity ensues.

Satellite Servicing

This is more a near-future business. Which means it could be a MacGuffinite precursor.

In the present time the biggest space industry is satellites. These are mostly of the communication variety (telecommunication, radio, television, phone, internet access), but navigation, weather, and crop monitoring are also viable industries. Not to mention all the military spy satellites.

These suckers are hideously expensive to design, build, and launch into orbit. Obviously the longer their effective lifespan, the more the owner can amortised the cost.

What limits the satellite's lifespan? Is it meteorite strikes? No. Is it deterioraization due to space radiation? No. Is it electronic malfunctions? No. Well, what is it? The blasted fuel tanks for the attitude control jets being used up! And the little darlings generally run dry years before anything else on the satellite zaps out.

Gee, it is a shame there exists no company running satellite orbit-side servicing like an outer space Triple-A, filling empty attitude-jet fuel-tanks and repairing malfunctions. They could charge huge fees without being more expensive than launching an entire new replacement satellite.

Sounds like a business opportunity to me.

This was the inspiration for the 1988 MOVERS Orbital Transfer Vehicle study. More recently (2017) the Space Infrastructure Services LLC (SIS) company proposed a similar service, using teloperated drones. Now please understand that their drones can only refuel SIS designed satellites, but they probably consider that to be an advantage.

Laser Launch Services

Remember that once you get to orbit you are halfway to anywhere. So a company offering an affordable way to get your payload and crew into orbit will find their services in high demand. Freeman Dyson is of the opinion that a large country such as the United States should invest in such a service and offer it at a nominal fee, in order to promote interplanetary Prairie Schooners. See below.

For a grittier more ruthless-corporation view of the laser-launching business, do check out Jerry Pournelle's Laurie Jo Hansen stories, available in the collection Exile And Glory.

IKEA Space Habitat Modules
People living in space need a habitat module to live in (or they will rapidly stop living). So there is a build-in market. Flimsy cheap modules will do for orbital or asteroid locations. But sturdier modules will be needed if it has to be able to stand under its own weight on a planetary surface, or accelerated by a rocket engine if used as an impromptu spacecraft. The inexpensive modules might be mostly made of water. They will probably be sized to fit standard cargo containers. See the short story. In the real world Bigelow Aerospace is actively developing this, using NASA TransHab technology.
Wagon Train in Space

Jerry Pournelle foresees that with the availability of a laser launch service coupled with affordable habitat modules could lead to wagon train in space.

Mom and Pop pioneers/rock-rats/space-entrepreneurs just need the price of a hab module and laser boost fees for the overhead of space access. This gets them into LEO.

Then all Mom and Pop need (besides supplies for their business model) is transport. The Wagon Train Company would have orbital tugs for hire with regular service to haul hab modules to various interplanetary destinations. The tugs could probably haul long strings of hab modules at a time, especially if the tugs had a waterskiing thruster arrangement. Wagon train indeed!

The tug would probably also haul a company emergency module. If one of the hab modules springs a leak or otherwise has an emergency, the company module could rescue them. In exchange for a stiff fee, of course. In the wild west, wagon trains were mostly for mutual assistance, so the inhabitants of the various hab modules would probably want to try and help each other. Only if nobody offers any help would the unlucky Mom and Pop have to mortgage their souls to the company emergency module.

For a bit more money, travelers could upgrade from a rocketless habitat module to something with minimal rockets. Brian McConnell and Alex Tolley have a great concept called the Spacecoach that would be just perfect. But it would still make sense to travel in a wagon train led by a Wagon Train Company transport (even if you do not need their hauling services). Just in case you suddenly need the services of the company emergency module.

The Motel Aldrin

Entrepreneurs could sell habitat module services between Terra and Mars by making a space-going motel into an Aldrin Cycler. Space explorers on a budget would only need enough delta V to get themselves and their payload up to Mars transfer velocity, they could then rent a room and life-support services at Motel 6 km/s. This concept is quite similar to the Wagon Train in Space.

Convoy Services

Spacecraft going to a given destination, e.g., Mars, will tend to clump into convoys in order to take advantage of Hohmann transfer windows. Clever operators will have special ships in the group: not to travel to Mars but to do business with the other ships in the group (with an eye to making lots of money).

Things like being an interplanetary 7-Eleven all night convenience store, selling those vital little necessities (that you forgot to pack) at inflated prices.

A fancy restaurant spaceship for when you are truly fed up with eating those nasty freeze-dried rations.

A space-going showboat for outer space riverboat gambling.

An (expensive) health clinic, when you are not sure if that is merely a tummy-ache or actually full-blown appendicitis.

A flying bar with a wide variety of vacuum-distilled liquors (anybody for a Pan Galactic Gargle Blaster?).

Not to mention a orbital brothel.

Fans of TOS Battlestar Galactica will be reminded of the Rising Star, luxury liner and casino in space.

And the owners of an wagon train in space might want to add a couple of these company-owned modules, to sell stuff to the wagon train riders.


Orbital laser services might be just as lucrative as laser launching services. Owners of cheap laser thermal rockets could rent laser time from Beams-R-Us. Not to mention spacecoach owners. You could probably even rent the cheap laser thermal rockets for use with the laser time.

For that matter, Beams-R-Us would probably have their own cargo laser rockets for transport services, making them the interplanetary equivalent of the railroad (The Laser Horse). Even if there is no initial need for such services, a government might create it for political reasons. Even if it is eventually taken over by the military.

A laser railroad could easily become Wagon Train in Space.

See above for technical details on laser thrust services.

Orbital Propellant Depots

The multi-billion dollar Terran petroleum industry is a model for offering the services of orbital propellant depots. Since propellant is the sine qua non of rockets, owning a network of such depots and the supplying them by in situ resource utilization will be a license to print money.

There is also money to be made on the side by being the interplantary equivalent of a 7-Eleven convenience store attached to a gasoline station. With the same inflated prices.

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.

Momentum-energy Banks

These are giant spinning bola-like tether propulsion installations. A pod with engines not much stronger than attitude jets can attach itself to one and be precisely catapulted at a destination with many gravities of acceleration. At the destination the pod is caught by a similar installation. All for a fee, of course.

For an interplanetary Prairie Schooners owned by a Ma-and-Pa company, momentum-energy banks dovetail nicely with laser launch services. It doesn't matter that your tin-can habitat module has the same delta V as a can of underarm deodorant spray. The laser will boost it into orbit and the bola will sling it to the destination. The limits are [a] you can only travel between momentum-energy banks installations and [b] do you have enough money to pay for the bola services? [c] is the acceleration low enough so it won't instantly kill Ma and Pa?

Inert Cargo Vessels
Inert cargo vessel shipping services will probably be a cheaper solution to sending your ore to market than renting a cargo spacecraft.
A "gold" strike in an asteroid belt or the establishment of a military base in a remote location may create a "boomtown", as entrepreneurs appear to sell the asteroid miners or enlisted people whiskey, prostitutes, and gambling. But remember that boomtowns can become ghost towns quite rapidly, if mineral strike dries up or the military base is closed.
Camp Followers
Military units operating in a remote location will often attract "camp followers." These are civilian hangers-on who officially or unofficially see to needs of the troops. Official camp followers could be civilian contractors supplying official items like fuel, signal flares, and fragmentation grenades. Unofficial camp followers supply services like cooking, laundering, liquor, nursing, sexual services, and sutlery. For a price. Unofficial camp followers are notorious for after-battle scavenging and looting.
Sears, Robot & Co.
In the 1900's the Sears, Roebuck & Co. made good money doing mail-order catalog sales to rural inhabitants. The same model might be applied to asteroid dwellers. See below
Asteroid Mining Services
Asteroid miners have lots of needs that entrepreneurs can fulfil. From renting mobile refineries to purchasing ore. Although in reality the economies of scale seem to preclude individual mom-and-pop asteroid metal miners, volatile mining might be their only option.
New and Used Spacecraft Yards
Don't forget Dealer Dan, The Spaceship Man with his wide selection of new and slightly used rockets. "Now this little beauty was owned by a little old lady who only took it out on alternate synodic periods..."

(“Terminal” by Lavie Tidhar is an emotionally wrenching science fiction story about people, who, either having nothing to lose or having a deep desire to go into space, travel to Mars via cheap, one-person, one-way vehicles dubbed jalopies. During the trip, those in the swarm communicate with each other, their words relayed to those left behind.)

      From above the ecliptic the swarm can be seen as a cloud of minute bullet-shaped insects, their hulls, packed with photovoltaic cells, capturing the sunlight; tiny, tiny flames burning in the vastness of the dark.
     They crawl with unbearable slowness across this small section of near space, beetles climbing a sheer obsidian rock face. Only the sun remains constant. The sun, always, dominates their sky.
     Inside each jalopy are instrument panels and their like; a sleeping compartment where you must float your way into the secured sleeping bag; a toilet to strap yourself to; a kitchen to prepare your meal supply; and windows to look out of. With every passing day the distance from Earth increases and the time-lag grows a tiny bit longer and the streaming of communication becomes more echoey, the most acute reminder of that finite parting as the blue-green egg that is Earth revolves and grows smaller in your window, and you stand there, sometimes for hours at a time, fingers splayed against the plastic, staring at what has gone and will never come again, for your destination is terminal.

     There is such freedom in the letting go.
     There is the music. Mei listens to the music, endlessly. Alone she floats in her cheap jalopy, and the music soars all about her, an archive of all the music of Earth stored in five hundred terabytes or so, so that Mei can listen to anything ever written and performed, should she so choose, and so she does, in a glorious random selection as the jalopy moves in the endless swarm from Earth to Terminal. Chopin’s Études bring a sharp memory of rain and the smell of wet grass, of damp books and days spent in bed, staring out of windows, the feel of soft sheets and warm pyjamas, a steaming mug of tea. Mei listens to Vanuatu string band songs in pidgin English, evocative of palm trees and sand beaches and graceful men swaying in the wind; she listens to Congolese kwasa kwasa and dances, floating, shaking and rolling in weightlessness, the music like an infectious laugh and hot tropical rain. The Beatles sing “Here Comes the Sun,” Mozart’s Requiem trails off unfinished, David Bowie’s “Space Oddity” haunts the cramped confines of the jalopy: the human race speaks to Mei through notes like precise mathematical notations, and, alone, she floats in space, remembering in the way music always makes you remember.

     She is not unhappy.
     At first, there was something seemingly inhuman about using the toilets. It is like a hungry machine, breathing and spitting, and Mei must ride it, strapping herself into leg restraints, attaching the urine funnel, which gurgles and hisses as Mei evacuates waste. Now the toilet is like an old friend, its conversation a constant murmur, and she climbs in and out without conscious notice.
     At first, Mei slept and woke up to a regiment of day and night, but a month out of Earth orbit, the old order began to slowly crumble, and now she sleeps and wakes when she wants, making day and night appear as if by magic, by a wave of her hand. Still, she maintains a routine, of washing and the brushing of teeth, of wearing clothing, a pretence at humanity which is sometimes hard to maintain being alone. A person is defined by other people.
     Three months out of Earth and it’s hard to picture where you’d left, where you’re going. And always that word, like a whisper out of nowhere, Terminal, Terminal…
     Mei floats and turns slowly in space, listening to the Beach Boys.

     But really, it is the sick, the slowly dying, those who have nothing to lose, those untied by earthly bonds, those whose spirits are as light as air: the loners and the crazy and worst of all the artists, so many artists, each convinced in his or her own way of the uniqueness of the opportunity, exchanging life for immortality, floating, transmuting space into art in the way of the dead, for they are legally dead, now, each in his or her own jalopy, this cheap mass-manufactured container made for this one singular trip, from this planet to the next, from the living world to the dead one.
     “Sign here, initial here, and here, and here—” and what does it feel like for those everyday astronauts, those would-be Martians, departing their homes for one last time, a last glance back, some leaving gladly, some tearfully, some with indifference: these Terminals, these walking dead, having signed over their assets, completed their wills, attended, in some instances, their very own wakes: leaving with nothing, boarding taxis or flights in daytime or night, to the launch site for rudimentary training with instruments they will never use, from Earth to orbit in a space plane, a reusable launch vehicle, and thence to Gateway, in low Earth orbit, that ramshackle construction floating like a spider web in the skies of Earth, made up of modules, some new, some decades old, joined together in an ungainly fashion, a makeshift thing.
     …Here we are all astronauts. The permanent staff is multinational, harassed; monkey-like, we climb heel and toe heel and toe, handholds along the walls no up no down but three-dimensional space as a many-splendoured thing. Here the astronauts are trained hastily in maintaining their craft and themselves, and the jalopies extend out of Gateway, beyond orbit, thousands of cheap little tin cans aimed like skipping stones at the big red rock yonder.
     Here, too, you can still change your mind. Here comes a man now, a big man, an American man, with very white face and hands, a man used to being in control, a man used to being deferred to—an artist, in fact; a writer. He had made his money imagining the way the future was, but the future had passed him by and he found himself spending his time on message boards and the like, bemoaning youth and their folly. Now he has a new lease on life, or thought he had, with this plan of going into space, to Terminal Beach: six months floating in a tin can high above no world, to write his masterpiece, the thing he is to be remembered by, his novel, damn it, in which he’s to lay down his entire philosophical framework of a libertarian bent: only he has, at the last moment, perhaps on smelling the interior of his assigned jalopy, changed his mind. Now he comes inexpertly floating like a beach ball down the shaft, bouncing here and there from the walls and bellowing for the agent, those sleazy jalopymen, for the final signature on the contract is digital, and sent once the jalopy is slingshot to Mars. It takes three orderlies to hold him, and a nurse injects him with something to calm him down. Later, he would go back down the gravity well, poorer yet wiser, but he will never write that novel: space eludes him.
     Meanwhile, the nurse helps carry the now-unconscious American down to the hospital suite, a house-sized unit overlooking the curve of the Earth. Her name is Eliza and she watches day chase night across the globe and looks for her home, for the islands of the Philippines to come into view, their lights scattered like shards of shining glass, but it is the wrong time to see them. She monitors the IV distractedly, feeling tiredness wash over her like the first exploratory wave of a grey and endless sea. For Eliza, space means always being in sight of this great living world, this Earth, its oceans and its green landmasses and its bright night lights, a world that dominates her view, always, that glares like an eye through pale white clouds. To be this close to it and yet to see it separate, not of it but apart, is an amazing thing; while beyond, where the Terminals go, or farther yet, where the stars coalesce as thick as clouds, who knows what lies? And she fingers the gold cross on the chain around her neck, as she always does when she thinks of things alien beyond knowing, and she shudders, just a little bit; but everywhere else, so far, the universe is silent, and we alone shout.

     “Hello? Is it me you’re looking for?”
     “Who is this?”
     “This is jalopy A-5011 sending out a call to the faithful to prayer –”
     “This is Bremen in B-9012, is there anyone there? Hello? I am very weak. Is there a doctor, can you help me, I do not think I’ll make it to the rock, hello, hello—”
     “This is jalopy B-2031 to jalopy C-3398, bishop to king 7, I said bishop to king 7, take that Shen you twisted old fruit!”
     “Hello? Has anyone heard from Shiri Applebaum in C-5591, has anyone heard from Shiri Applebaum in C-5591, she has not been in touch in two days and I am getting worried, this is Robin in C-5523, we were at Gateway together before the launch, hello, hello—”

     Mei turns down the volume of the music and listens to the endless chatter of the swarm rise alongside it, day or night, neither of which matter or exist here, unbound by planetary rotation and that old artificial divide of darkness and the light. Many like Mei have abandoned the twenty-four hour cycle to sleep and rise ceaselessly and almost incessantly with some desperate need to experience all of this, this one-time-only journey, this slow beetle’s crawl across trans-solar space. Mei swoops and turns with the music and the chatter, and she idly wonders of the fate to have befallen Shiri Applebaum in C-5591: is she merely keeping quiet or is she dead or in a coma, never to wake up again, only her corpse and her cheap little jalopy hitting the surface of Mars in ninety more days? Across the swarm’s radio network, the muezzin in A-5011 sends out the call to prayer, the singsong words so beautiful that Mei stops, suspended in mid air, and breathes deeply, her chest rising and falling steadily, space all around her. She has degenerative bone disease, there isn’t a question of starting a new life at Terminal, only this achingly beautiful song that rises all about her, and the stars, and silent space.
     Two days later Bremen’s calls abruptly cease. B-9012 still hurtles on with the rest towards Mars. Haziq tries to picture Bremen: what was he like? What did he love? He thinks he remembers him, vaguely, a once-fat man now wasted with folded awkward skin, large glasses, a Scandinavian man maybe, Haziq thought, but all he knows or will ever know of Bremen is the man’s voice on the radio, bouncing from jalopy to jalopy and on to Earth where jalopy-chasers scan the bands and listen in a sort of awed or voyeuristic pleasure.

     “This is Haziq, C-6173…” He coughs and clears his throat. He drinks his miso soup awkwardly, suckling from its pouch. He sits formally, strapped by Velcro, the tray of food before him, and out of his window he stares not back to Earth or forward to Mars but directly onto the swarm, trying to picture each man and woman inside, trying to imagine what brought them here. Does one need a reason? Haziq wonders. Or is it merely that gradual feeling of discomfort in one’s own life, one’s own skin, a slowly dawning realisation that you have passed like a grey ghost through your own life, leaving no impression, that soon you might fade away entirely, to dust and ash and nothingness, a mild regret in your children’s minds that they never really knew you at all.
     “This is Haziq, C-6173, is there anyone hearing me, my name is Haziq and I am going to Terminal”—and a sudden excitement takes him. “My name is Haziq and I am going to Terminal!” he shouts, and all around him the endless chatter rises, of humans in space, so needy for talk like sustenance, “We’re all going to Terminal!” and Haziq, shy again, says, “Please, is there anyone there, won’t someone talk to me. What is it like, on Terminal?”
     But that is a question that brings down the silence; it is there in the echoes of words ords rds and in the pauses, in punctuation missing or overstated, in the endless chess moves, worried queries, unwanted confessionals, declarations of love, in this desperate sudden need that binds them together, the swarm, and makes all that has been before become obsolete, lose definition and meaning. For the past is a world one cannot return to, and the future is a world none has seen.

     Mei floats half-asleep half-awake, but the voice awakens her. Why this voice, she never knows, cannot articulate. “Hello. Hello. Hello…” And she swims through the air to the kitchenette and heats up tea and drinks it from the suction cup. There are no fizzy drinks on board the jalopies, the lack of gravity would not separate liquid and gas in the human stomach, and the astronaut would wet-burp vomit. Mei drinks slowly, carefully; all her movements are careful. “Hello?” she says, “Hello, this is Mei in A-3357, this is Mei in A-3357, can you hear me, Haziq, can you hear me?”
     A pause, a micro-silence, the air filled with the hundreds of other conversations through which a voice, his voice, says, “This is Haziq! Hello, A-3357, hello!”
     “Hello,” Mei says, surprised and strangely happy, and she realises it is the first time she has spoken in three months. “Let me tell you, Haziq,” she says, and her voice is like music between worlds, “let me tell you about Terminal.”

     It was raining in the city. She had come out of the hospital and looked up at the sky and saw nothing there, no stars no sun, just clouds and smoke and fog. It rained, the rain collected in rainbow puddles in the street, the chemicals inside it painted the world and made it brighter. There was a jalopy vendor on the corner of the street, above his head a promotional video in 3D, and she was drawn to it. The vendor played loud K-pop and the film looped in on itself, but Mei didn’t mind the vendor’s shouts, the smell of acid rain or frying pork sticks and garlic or the music’s beat which rolled on like thunder. Mei stood and rested against the stand and watched the video play. The vendor gave her glasses, embossed with the jalopy sub-agent’s logo. She watched the swarm like a majestic silver web spread out across space, hurtling (or so it seemed) from Earth to Mars. The red planet was so beautiful and round, its dry seas and massive mountain peaks, its volcanoes and canals. She watched the polar ice caps. Watched Olympus Mons breaking out of the atmosphere. Imagined a mountain so high, it reached up into space. Imagined women like her climbing it, smaller than ants but with that same ferocious dedication. Somewhere on that world was Terminal.

     “Picture yourself standing on the red sands for the very first time,” she tells Haziq, her voice the same singsong of the muezzin at prayer, “that very first step, the mark of your boot in the fine sand. It won’t stay there forever, you know. This is not the moon, the winds will come and sweep it away, reminding you of the temporality of all living things.” And she pictures Armstrong on the moon, that first impossible step, the mark of the boots in the lunar dust. “But you are on a different world now,” she says, to Haziq or to herself, or to the others listening, and the jalopy-chasers back on Earth. “With different moons hanging like fruit in the sky. And you take that first step in your suit, the gravity hits you suddenly, you are barely able to drag yourself out of the jalopy, everything is labour and pain. Who knew gravity could hurt so much,” she says, as though in wonder. She closes her eyes and floats slowly upwards, picturing it. She can see it so clearly, Terminal Beach where the jalopies wash ashore, endlessly, like seashells, as far as the eye can see the sand is covered in the units out of which a temporary city rises, a tent city, all those bright objects on the sand. “And as you emerge into the sunlight they stand there, welcoming you, can you see them? In suits and helmets, they extend open arms, those Martians, Come, they say, over the radio comms, come, and you follow, painfully and awkwardly, leaving tracks in the sand, into the temporary domes and the linked-together jalopies and the underground caves which they are digging, always, extending this makeshift city downwards, and you pass through the airlock and take off your helmet and breathe the air, and you are no longer alone, you are amongst people, real people, not just voices carried on the solar winds.”
     She falls silent then. Breathes the limited air of the cabin. “They would be planting seeds,” she says, softly, “underground, and in greenhouses, all the plants of Earth, a paradise of watermelons and orchids, of frangipani and durian, jasmine and rambutan…” She breathes deeply, evenly. The pain is just a part of her, now. She no longer takes the pills they gave her. She wants to be herself; pain and all.

     In jalopies scattered across this narrow silver band, astronauts like canned sardines marinate in their own stale sweat and listen to her voice. Her words, converted into a signal inaudible by human ears, travel across local space for whole minutes until they hit the Earth’s atmosphere at last, already old and outdated, a record of a past event; here they bounce off the Earth to the ionosphere and back again, jaggedy waves like a terminal patient’s heart monitor circumnavigating this rotating globe until they are deciphered by machines and converted once more into sound:
     Mei’s voice speaking into rooms, across hospital beds, in dark bars filled with the fug of electronic cigarettes’ smoke-like vapoured steam, in lonely bedrooms where her voice keeps company to cats, in cabs driving through rain and from tinny speakers on white sand beaches where coconut crabs emerge into sunset, their blue metallic shells glinting like jalopies. Mei’s voice soothes unease and fills the jalopy-chasers’ minds with bright images, a panoramic view of a red world seen from space, suspended against the blackness of space; the profusion of bright galaxies and stars behind it is like a movie screen.

     “Take a step, and then another and another. The sunlight caresses your skin, but its rays have travelled longer to reach you, and when you raise your head the sun shines down from a clay-red sun, and you know you will never again see the sky blue. Think of that light. It has travelled longer and faster than you ever will, its speed in vacuum a constant 299,792,458 meters per second. Think of that number, that strange little fundamental constant, seemingly arbitrary: around that number faith can be woven and broken like silk, for is it a randomly created universe we live in or an ordained one? Why the speed of light, why the gravitational constant, why Planck’s? And as you stand there, healthy or ill, on the sands of Terminal Beach and raise your face to the sun, are you happy or sad?”

     Mei’s voice makes them wonder, some simply and with devotion, some uneasily. But wonder they do, and some will go outside one day and encounter the ubiquitous stand of a jalopyman and be seduced by its simple promise, abandon everything to gain a nebulous idea, that boot mark in the fine-grained red sand, so easily wiped away by the winds.
     And Mei tells Haziq about Olympus Mons and its shadow falling on the land and its peak in space, she tells him of the falling snow, made of frozen carbon dioxide, of men and women becoming children again, building snowmen in the airless atmosphere, and she tells him of the Valles Marineris, where they go suited up, hand in gloved hand, through the canyons whose walls rise above them, east of Tharsis.

     Perhaps it is then that Haziq falls in love, a little bit, through walls and vacuum, the way a boy does, not with a real person but with an ideal, an image. Not the way he had fallen in love with his wife, not even the way he loves his children, who talk to him across the planetary gap, their words and moving images beamed to him from Earth, but they seldom do, any more, it is as if they had resigned themselves to his departure, as if by crossing the atmosphere into space he had already died and they were done with mourning.
     It is her voice he fastens onto; almost greedily; with need. And as for Mei, it is as if she had absorbed the silence of three months and more than a hundred million kilometres, consumed it somehow, was sustained by it, her own silence with only the music for company, and now she must speak, speak only for the sake of it, like eating or breathing or making love, the first two of which she will soon do no more and the last of which is already gone, a thing of the past. And so she tells the swarm about Terminal.

     But what is Terminal? Eliza wonders, floating in the corridors of Gateway, watching the RLVs rise into low Earth orbit, the continents shifting past, the clouds swirling, endlessly, this whole strange giant spaceship planet as it travels at 1200 kilometres an hour around the sun, while at the same time Earth, Mars, Venus, Sun and all travel at nearly 800,000 kilometres per hour around the centre of the galaxy, while at the same time this speed machine, Earth and sun and the galaxy itself move at 1000 kilometres per second towards the Great Attractor, that most mysterious of gravitational enigmas, this anomaly of mass that pulls to it the Milky Way as if it were a pebble: all this and we think we’re still, and it makes Eliza dizzy just to think about it.

     But she thinks of such things more and more. Space changes you, somehow. It tears you out of certainties, it makes you see your world at a distance, no longer of it but apart. It makes her sad, the old certainties washed away, and more and more she finds herself thinking of Mars; of Terminal.
     To never see your home again; your family, your mother, your uncles, brothers, sisters, aunts, cousins and second cousins and third cousins twice removed, and all the rest of them: never to walk under open skies and never to sail on a sea, never to hear the sound of frogs mating by a river or hear the whooshing sound of fruit bats in the trees. All those things and all the others you will never do, and people carry bucket lists around with them before they become Terminal, but at long last everything they ever knew and owned is gone and then there is only the jalopy confines, only that and the stars in the window and the voice of the swarm. And Eliza thinks that maybe she wouldn’t mind leaving it all behind, just for a chance at…what? Something so untenable, as will-o’-the-wisp as ideology or faith and yet as hard and precisely defined as prime numbers or fundamental constants. Perhaps it is the way Irish immigrants felt on going to America, with nothing but a vague hope that the future would be different from the past. Eliza had been to nursing school, had loved, had seen the world rotate below her; had been to space, had worked on amputations, births, tumour removals, fevers turned fatal, transfusions and malarias, has held a patient’s hand as she died or dried a boy’s tears or made a cup of tea for the bereaved, monitored IVs, changed sheets and bedpans, took blood and gave injections, and now she floats in freefall high above the world, watching the Terminals come and go, come and go, endlessly, and the string of silver jalopies extends in a great horde from Earth’s orbit to the Martian surface, and she imagines jalopies fall down like silver drops of rain, gently they glide down through the thin Martian atmosphere to land on the alien sands.

     She pictures Terminal and listens to Mei’s voice, one amongst so many but somehow it is the voice others return to, it is as though Mei speaks for all of them, telling them of the city being built out of cheap used bruised jalopies, the way Gateway had been put together, a lot of mismatched units joined up, and she tells them, you could fall in love again, with yourself, with another, with a world.
     She waits; she likes his voice. She floats in the cabin, her mind like a calm sea. She listens to the sounds of the jalopy, the instruments and the toilet and the creaks and rustle of all the invisible things. She is taking the pills again, she must, for the pain is too great now, and the morphine, so innocent a substance to come like blood out of the vibrant red poppies, is helping. She knows she is addicted. She knows it won’t last. It makes her laugh. Everything delights her. The music is all around her now, Lao singing accompanied by a khene changing into South African kwaito becoming reggae from PNG.

     One month to planetfall. And Mei falls silent. Haziq tries to raise her on the radio but there is no reply. “Hello, hello, this is Haziq, C-6173, this is Haziq, C-6173, has anyone heard from Mei in A-3357, has anyone heard from Mei?”
     “This is Henrik in D-7479, I am in a great deal of pain, could somebody help me? Please, could somebody help me?”
     “This is Cobb in E-1255, I have figured it all out, there is no Mars, they lied to us, we’ll die in these tin cans, how much air, how much air is left?”
     “This is jalopy B-2031 to jalopy C-3398, queen to pawn 4, I said queen to pawn 4, and check and mate, take that, Shen, you twisted old bat!”
     “This is David in B-1201, jalopy B-1200, can you hear me, jalopy B-1200, can you hear me, I love you, Joy. Will you marry me? Will you—”
     “Yes! Yes!”
     “We might not make it. But I feel like I know you, like I’ve always known you, in my mind you are as beautiful as your words.”
     “I will see you, I will know you, there on the red sands, there on Terminal Beach, oh, David—”
     “My darling—”
     “This is jalopy C-6669, will you two get a room?” and laughter on the radio waves, and shouts of cheers, congrats, mazel tov and the like. But Mei cannot be raised, her jalopy’s silent.

     Not jalopies but empty containers with nothing but air floating along with the swarm, destined for Terminal, supplements for the plants, and water and other supplies, and some say these settlers, if that’s what they be, are dying faster than we can replace them, but so what. They had paid for their trip. Mars is a madhouse, its inmates wander their rubbish heap town, and Mei, floating with a happy distracted mind, no longer hears even the music. And she thinks of all the things she didn’t say. Of stepping out onto Terminal Beach, of coming through the airlock, yes, but then, almost immediately, coming out again, suited uncomfortably, how hard it was, to strip the jalopies of everything inside and, worse, to go on corpse duty.
     She does not want to tell all this to Haziq, does not want to picture him landing, and going with the others, this gruesome initiation ceremony for the newly arrived: to check on the jalopies no longer responding, the ones that didn’t open, the ones from which no one has emerged. And she hopes, without reason, that it is Haziq who finds her, no longer floating but pressed down by gravity, her fragile bones fractured and crushed; that he would know her, somehow. That he would raise her in his arms, gently, and carry her out, and lay her down on the Martian sand.
     Then they would strip the jalopy and push it and join it to the others, this spider bite of a city sprawling out of those first crude jalopies to crash-land, and Haziq might sleep, fitfully, in the dormitory with all the others, and then, perhaps, Mei could be buried. Or left to the Martian winds.

     She imagines the wind howling through the canyons of the Valles Marineris. Imagines the snow falling, kissing her face. Imagines the howling winds stripping her of skin and polishing her bones, imagines herself scattered at last, every tiny bit of her blown apart and spread across the planet.
     And she imagines jalopies like meteorites coming down. Imagines the music the planet makes, if only you could hear it. And she closes her eyes and she smiles.
     “I hope it’s you…”
     “Sign here, initial here, and here, and here.”
     The jalopyman is young and friendly, and she knows his face if not his name. He says, perhaps in surprise or in genuine interest, for they never, usually, ask, “Are you sure you want to do it?”
     And Eliza signs, and she nods, quickly, like a bird. And she pushes the pen back at him, as if to stop from changing her mind.
     “I hope it’s you…”
     “Mei? Is that you? Is that you?”
     But there is no one there, nothing but a scratchy echo on the radio; like the sound of desert winds.

From TERMINAL by Lavie Tidhar (2016)

According to the AIAA Space Logistics Technical Committee, space logistics is

... the theory and practice of driving space system design for operability, and of managing the flow of material, services, and information needed throughout a space system lifecycle.

However, this definition in its larger sense includes terrestrial logistics in support of space travel, including any additional "design and development, acquisition, storage, movement, distribution, maintenance, evacuation, and disposition of space materiel", movement of people in space (both routine and for medical and other emergencies), and contracting and supplying any required support services for maintaining space travel.


Wernher von Braun spoke of the necessity (and the underdevelopment) of space logistics as early as 1960:

"We have a logistics problem coming up in space ... that will challenge the thinking of the most visionary logistics engineers. As you know, we are currently investigating three regions of space: near-Earth, the lunar region, and the planets. While it is safe to say that all of us have undoubtedly been aware of many or most of the logistics requirements and problems in the discussion, at least in a general way, I think it is also safe to state that many of us have not realized the enormous scope of the tasks performed in the logistics area. I hope the discussions bring about a better understanding of the fact that logistics support is a major portion of most large development projects. Logistics support, in fact, is a major cause of the success or failure of many undertakings."


James D. Baker and Frank Eichstadt of SPACEHAB wrote, in 2005:

The United States space exploration goals expressed in January 2004 call for the retirement of the Space Shuttle program following completion of International Space Station (ISS) construction. Since the Shuttle is instrumental in transporting large quantities of cargo to and from the ISS, this functional capability must be preserved to ensure ongoing station operations in a post-Shuttle era. Fulfilling ongoing cargo transport requirements to the ISS is a prime opportunity for NASA to reduce costs and preserve and repurpose the unique and limited Shuttle resource by acquiring cargo transportation services commercially. Further, implementing such a service prior to retirement of the Shuttle reduces risk to the vehicle and her crews by eliminating their use for routine cargo transport missions while accelerating the readiness for alternative ISS-support transportation.
In January 2004, President Bush directed NASA to begin an initiative that focuses on exploration of the Moon, Mars, and beyond. This initiative calls for the completion of International Space Station (ISS) assembly by the end of the decade coincident with retirement of the Space Shuttle. Retirement of the Shuttle while ISS operations are still being conducted results in reduced capability to supply ISS logistics requirements. An examination of existing and planned logistics carriers shows that there are deficiencies in both capacity and capability to support ISS needs. SPACEHAB's history of space station logistics delivery and existing ground infrastructure coupled with NASA's mandate and documented intent to acquire commercial space systems and services when possible has led SPACEHAB to develop a versatile and affordable cargo transport service for ISS .

Current activities

According to Manufacturing Business Technology,

NASA has awarded $3.8 million to two MIT engineering professors to pursue an interdisciplinary study for adapting supply chain logistics to support interplanetary material transport and transfer. Professors David Simchi-Levi and Olivier de Weck of the MIT Engineering Systems Division will spearhead the project in partnership with the Jet Propulsion Laboratory, Payload Systems, and United Space Alliance.
Sustainable space exploration is impossible without appropriate supply chain management and unlike Apollo, future exploration will have to rely on a complex supply network on the ground and in space. The primary goal of this project is to develop a comprehensive supply chain management framework and planning tool for space logistics. The eventual integrated space logistics framework will encompass terrestrial movement of material and information, transfer to launch sites, integration of payload onto launch vehicles and launch to Low Earth Orbit, in-space and planetary transfer, and planetary surface logistics. The MIT-led interplanetary supply chain management model will take a four-phase development approach:
1. Review of supply chain management lessons learned from Earth-based commercial and military projects, including naval submarine and arctic logistics
2. Space logistics network analyses based on modeling Earth-Moon-Mars orbits and expected landing-exploration sites
3. Demand/supply modeling that embraces uncertainty in demand, cargo mix, costs, and supply chain disruptions
4. Development of an interplanetary supply chain architecture.

Examples of supply classes

(ed note: All of these are business opportunities)

Among the supply classes identified by the MIT Space Logistics Center:

  • Propellants and Fuels
  • Crew Provisions and Operations
  • Maintenance and Upkeep
  • Stowage and Restraint
  • Waste and Disposal
  • Habitation and Infrastructure
  • Transportation and Carriers
  • Miscellaneous

In the category of space transportation for ISS Support, one might list:

State of the ISS logistics capability in 2005

A snapshot of the logistics of a single space facility, the International Space Station, was provided in 2005 via a comprehensive study done by James Baker and Frank Eichstadt. This article section makes extensive reference to that study.

ISS cargo requirements

As of 2004, the United States Space Shuttle, the Russian Progress, and to a very limited extent, the Russian Soyuz vehicles were the only space transport systems capable of transporting ISS cargo.

However, in 2004, it was already anticipated that the European Automated Transfer Vehicle (ATV) and Japanese H-IIA Transfer Vehicle (HTV) would be introduced into service before the end of ISS Assembly. As of 2004, the US Shuttle transported the majority of the pressurized and unpressurized cargo and provides virtually all of the recoverable down mass capability (the capability of non-destructive reentry of cargo).

Cargo vehicle capabilities

Baker and Eichstadt also wrote, in 2005:

An understanding of the future ISS cargo requirements is necessary to size a commercial cargo vehicle designed to replace the Shuttle's capabilities and capacities and augment currently planned alternative vehicles. Accurate estimates of ISS cargo transfer requirements are difficult to establish due to ongoing changes in logistics requirements, crew tending levels, vehicle availabilities, and the evolving role the ISS will play in NASA's space exploration and research goals.
An increased unpressurized cargo delivery requirement is shown during the years 2007–2010. This increased rate is a result of a current plan to preposition unpressurized spares on the ISS prior to Shuttle retirement. Provision of a commercial cargo carrier capable of transporting unpressurized spares to supplement the Shuttle eliminates the prepositioning requirement and aligns the estimated averages during 2007–2010 to approximately 24,000 kg for pressurized cargo and 6800 kg for unpressurized cargo. Considering the delivery capability of the remaining systems after the Shuttle is retired yields.
Retirement of the Shuttle and reliance on the Progress, ATV, and HTV for ISS logistics will result in no significant recoverable down-mass capability. Further, no evidence suggests that any of these cargo transport systems can increase production and launch rates to cover the cargo delivery deficiency.

Commercial opportunity

Baker and Eichstadt also wrote, in 2005:

In addition to ISS support deficiencies, alternative opportunities for a commercial cargo transport system exist. The retirement of the Shuttle will also result in an inability to conduct Low Earth Orbit (LEO) research independent of the ISS. A commercial payload service could serve as a free-flying research platform to fulfill this need. As logistics support requirements for NASA's space exploration initiative emerge, existing commercial system can be employed.
Finally, nascent interest in the development of non-government commercial space stations must take resupply issues into consideration. Such considerations will undoubtedly be subjected to a make/buy analysis. Existing systems which have amortized their development costs across multiple government and non-government programs should favor a “buy” decision by commercial space station operators. As these markets arise, commercial companies will be in a position to provide logistics services at a fraction of the cost of government-developed systems. The resulting economies of scale will benefit both markets. This conclusion was reached by a Price-Waterhouse study chartered by NASA in 1991. The study concluded that the value of SPACEHAB's flight-asset-based commercial module service with an estimated net-present-value of $160 million would have cost the US government over $1 billion to develop and operate using standard cost plus contracting. SPACEHAB's commercial operations and developments (such as the Integrated Cargo Carrier) since 1991 represent further cost savings over government-owned and operated systems.
Commercial companies are more likely to efficiently invest private capital in service enhancements, assured continued availability, and enhanced service capability. This tendency, commonplace in non-aerospace applications, has been demonstrated by SPACEHAB in the commercial space systems market via continued module enhancements and introduction of new logistics carriers.
Shortfalls in ISS cargo transport capacity, emerging opportunities, and experience gained from SPACEHAB's existing ground and flight operations have encouraged development of Commercial Payload Service (CPS). As a commercially developed system, SPACEHAB recognizes that to optimize its capability and affordability requires that certain approaches in system development and operations be taken.
The first approach levies moderate requirements on the system. Introducing fundamental capabilities on the front end and scarring for enhanced capabilities later reduces cost to launch and shortens development time.
The second one is the utilization of existing technology and capabilities, where appropriate. A typical feature of NASA programs is the continual reach for newly developed technologies. While attractive from a technical advancement perspective, this quest is expensive and often fails to create operational capabilities. A commercially developed cargo module will maximize the use of existing technologies (off the shelf where possible) and seek technical advances only where system requirements or market conditions drive the need for such advances. Additionally, costs associated with the development of spacecraft are not limited to those associated with the vehicle systems. Significant costs associated with the infrastructure must also be considered. SPACEHAB's existing logistics and vehicle processing facilities co-located with the Eastern launch range and at the Sea Launch facilities enable avoidance of significant system development costs.
Finally, SPACEHAB has realized cost and schedule reductions by employing commercial processes instead of Government processes. As a result, SPACEHAB's mission integration template for a Shuttle-based carrier is 14 months, compared to 22 months for a similar Shuttle-based Multi-Purpose Logistics Module (MPLM).

Rack transfer capability

Baker and Eichstadt also wrote, in 2005:

The ISS utilizes the International Standard Payload Rack (ISPR) as the primary payload and experiment accommodations structure in all US operated modules. Transferring ISPRs onto and off the ISS requires passage through the hatch only found at the Common Berthing Mechanism (CBM) berthing locations. The diameter of the CBM combined with ISPR proportions typically drives cargo vehicle diameters to sizes only accommodated by 5 m payload fairings launched on Evolved Expendable Launch Vehicles (EELV).

Recoverable reentry–pressurized payloads

Baker and Eichstadt also wrote, in 2005:

The Russian Progress vehicle has long served as a cargo vehicle which, upon departing a space station, destructively reenters the atmosphere destroying all “cargo” on board. This approach works very effectively for removing unwanted mass from a space station. However, NASA has indicated that the return of payloads from the ISS is highly desirable [5]. Therefore, a commercial system must examine the implications of including a pressurized payload return capability either in the initial design or as an enhanced feature of the service to be introduced in the future. Providing such capability requires the incorporation of thermal protection subsystem, deorbit targeting subsystems, landing recovery subsystems, ground recovery infrastructure, and FAA licensure. The recovery of unpressurized payloads presents unique challenges associated with the exposed nature of unpressurized carriers. To implement a recoverable reentry system for unpressurized payloads requires the development of an encapsulation system. Encapsulation activities must either occur autonomously prior to reentry or as a part of the operations associated with loading the unpressurized cargo carrier with return cargo. In either case, additional cost associated with spacecraft systems or increased operational requirements will be higher than simply loading and departing a pressurized carrier for a destructive reentry.

Mixed manifest capability

Baker and Eichstadt also wrote, in 2005:

Typically, the avoidance of point solutions provides flexibility for a given system to provide variable capabilities. Designing a cargo carrier that mixes pressurized and unpressurized systems can lead to increased cost if all associated cargo accommodations must be flown on every flight. To avoid unnecessary costs associated with designing and flying structure that accommodates fixed relative capacities of all types of payloads, a modular approach is taken for CPS. Anticipated cargo transport requirements for ISS after the Shuttle is retired indicate that dedicated pressurized and unpressurized missions can support the ISS up-mass requirements. Utilizing common base features (i.e. service module, docking system, etc.) and modularizing the pressurized and unpressurized carrier elements of the spacecraft assures flexibility while avoiding point solutions.

Propellant transfer

Baker and Eichstadt also wrote, in 2005:

The Russian Segment of the ISS (RSOS) has the capability via the probe and cone docking mechanisms to support propellant transfer. Incorporation of propellant transfer capability introduces international issues requiring the coordination of multiple corporate and governmental organizations. Since ISS propellant requirements are adequately provided for by the Russian Progress and ESA ATV, costs associated with incorporating these features can be avoided. However, the CPS’ modular nature coupled with the inherent capability of selected subsystems enables economical alternatives to propellant transfer should ISS needs require.
Indirect costs considered in developing the CPS architecture include licensing requirements associated with International Traffic in Arms Regulations (ITAR) and the Federal Aviation Administration (FAA) commercial launch and entry licensing requirements. ITAR licensing drives careful selection of the vehicle subsystem suppliers. Any utilization or manufacturing of spacecraft subsystems by non-US entities can only be implemented once the appropriate Department of State and/or Commerce approvals are in place. FAA licensing requirements necessitate careful selection of the launch and landing sites. Vehicles developed by a US organized corporation, even if launched in another country, require review of the vehicle system, operations, and safety program by the FAA to ensure that risks to people and property are within acceptable limits


While significant focus of space logistics is on upmass, or payload mass carried up to orbit from Earth, space station operations also have significant downmass requirements. Returning cargo from low-Earth orbit to Earth is known as transporting downmass, the total logistics payload mass that is returned from space to the surface of the Earth for subsequent use or analysis. Downmass logistics are important aspects of research and manufacturing work that occurs in orbital space facilities.

For the International Space Station, there have been periods of time when downmass capability was severely restricted. For example, for approximately ten months from the time of the retirement of the Space Shuttle following the STS-135 mission in July 2011—and the resultant loss of the Space Shuttle's ability to return payload mass—an increasing concern became returning downmass cargo from low-Earth orbit to Earth for subsequent use or analysis. During this period of time, of the four space vehicles capable of reaching and delivering cargo to the International Space Station, only the Russian Soyuz vehicle could return even a very small cargo payload to Earth. The Soyuz cargo downmass capability was limited as the entire space capsule was filled to capacity with the three ISS crew members who return on each Soyuz return. None of the remaining cargo resupply vehicles — the Russian Space Agency Progress, the European Space Agency (ESA) ATV, the Japan Aerospace Exploration Agency (JAXA) HTV — can return any downmass cargo for terrestrial use or examination.

After 2012, with the successful berthing of the commercially contracted SpaceX Dragon during the Dragon C2+ mission in May 2012, and the initiation of operational cargo flights in October 2012, downmass capability from the ISS is now 3,000 kilograms (6,600 lb) per Dragon flight, a service that is uniquely provided by the Dragon cargo capsule.

Nine additional Dragon cargo resupply flights are scheduled to depart the ISS with downmass in the next several years.

From the Wikipedia entry for SPACE LOGISTICS

      The phrase sticks in my mind. I surely read it in an SF novel, or more than one, and perhaps in a variation like daily moonship. Since it is an evocative phrase, at any rate to me, let us evoke something from it.

     The weekly moonship. Just the name tells us a good deal about Luna's place in human affairs: we go there every week, at least most weeks. It might be more; perhaps connecting flights depart from Cape Canaveral on Mondays, Baikonur on Tuesdays, and so on. But let us modestly stick to a single weekly moonship.

     Not only do we know that we go to the Moon weekly, we can venture a broad guess as to how many people make the trip. Our moonship surely carries more than a couple of passengers, fewer than a thousand; a broad range might be 10-200. We will say fifty: our moonship has the seating of a 1950s airliner or transcontinental train coach.
     Since the Luna round trip takes a week, weekly service probably means two passenger ships taking turns, with a third — perhaps an older model, less economical to fly — in reserve. For landing on the lunar surface, a shorter mission, one lander will do, with one in reserve. One or two ships suffice for other distant orbits, so altogether we have a generous half dozen passenger ships working the Moon and other locales in the outer reaches of Earth's orbital space.
     And we will suppose that these ships mostly fill their seats, unlike the rather similar spaceliner in 2001 that carried Heywood Floyd to the Moon in solitary VIP splendor. So about 2500 passengers travel to Luna each year, at least to lunar orbit; most continue on down to the surface. At this stage nearly all are making the round trip; if most are serving six-month rotations we have about a thousand regular residents of Luna Base and its outliers.
     Passengers making shorter stays nudge up the lunar population — as does anyone staying on past six months. Add a few hundred people in lunar orbit, or other distant orbits, for a total of roughly 2000 people in the outer orbital zone.
     Beyond that zone we might suppose that about fifty people are on or orbiting Mars, with a similar number aboard exploratory missions elsewhere — perhaps a half dozen active deep space ships that carry human crews, plus some robotic freighters that can take slower orbits.
     If the deep space missions use electric propulsion they depart from high orbits or at least refuel and take crew aboard there; if they use chemfuel or (properly shielded!) atomic rockets they blast straight out of low orbit for maximum Oberth effect. In that case the human presence in outer orbital space may still be confined largely to the Moon itself, and lunar orbit.
     But we are not mainly concerned here with deep space. Anyway,  you cannot yet buy a ticket aboard the biennial Mars ship the way you can with the weekly moonship.

     Looking inward, towards Earth, we can expect to find more people.

     Geosynch is economically important but surprisingly difficult to reach — nearly twice as hard as jumping over the Moon, as Apollo 8 did. Geosynchronous orbits are awkwardly placed: High enough that it takes a big burn to get there, close enough, thus with high orbital speed, that it takes sizable burns to match orbit, then head back down. So geosynch traffic is purely utilitarian, and the human presence perhaps less than in lunar orbit. A single passenger ship can serve this route, with one in reserve.
     Low Earth orbit is a different matter. It is the closest place in space, the easiest and cheapest to reach, and for many purposes and most passengers that is enough. Tourists can float and gawk as well here as anywhere. Virtual tourism is also served; Xollywood can and will use low Earth orbit as stand-in for the universe.
     So ... taking a not too deep breath, let us say that there are 10,000 people in low Earth orbit at a given time, ten times the lunar population. For those who are staying weeks or months in space, this corresponds to a tenfold increase in traffic volume, about 25,000 people going up every year for fairly long stays.
     But low Earth orbit allows quicker trips than the week-long journey to the Moon. So let us say that about ten percent of the people in low orbit are visiting for short stays of less than a week, adding about 50,000 annual trips, for a total of 75,000.
     And let us round things out by adding 25,000 tourists who simply go up and down, never exiting the shuttle, but going back with memories.

     Thus, 100,000 (!) passengers to space every year, a few hundred daily. If our passenger shuttles also carry fifty people, there are five or six daily flights to orbit worldwide. Allow, 'conservatively,' a one week turnaround, and there are about forty shuttles in the service rotation. Perhaps fifty in the active fleet, allowing for maintenance cycles, some in reserve, and so on.
     In human terms this is some serious traveling. We can suppose that the baseline human lift cost to low orbit is perhaps $50,000 (in present day USD), but that is an average. Business travelers will pay another $20K for a reserved ticket and 'complementary' cocktail; most pay cheerfully because they aren't paying; their company picks up the tab.
     Tourists fly standby and bring their own libations. They also benefit from the economics of unsold seats on the bus. The seats go into orbit whether or not any passengers are floating above them. The direct cost of lifting each passenger is really only a ton or two of propellant, at Earth industrial price, plus an airline meal.
     Which means that some seats will be sold pretty cheap, and even us peasants can pass on that new car, and instead spend a day looking the universe in the eye.

     The payload we care most about is us, but we must say a little about cargo traffic as well, especially since much of it also involves us intimately: food and shelter.
     At this level of development, growing food in space is still in trial stage; daily sustenance comes up from Earth. My baseline 'cheap' orbit lift cost is $100,000/ton, $45 per old fashioned pound. That is roughly ten times the grocery store price of everyday goods, but not much more than the price of luxury items.
     People in space will eat well, because the lobster doesn't cost much more than the rice you serve it with. In general, everyday economics has the boom-town combination of sky high all-around prices with peculiar twists.

     You also need a place to stay. The most massive and crucial structural works in space are not ships but dormitory habitat modules: where you live, if you are living in space or on the Moon.
     My baseline guesstimate for these is about 20 cubic meters and 10 tons per person. If you stripped all the laboratory equipment and such out of the International Space Station, beefed up life support, and fitted its pressure modules out like a Pullman train, it would have roomettes for some 45 people, which sounds about right.
     (For really long term occupancy, including children and pregnant women, you need another 5-10 tons of radiation shielding. On the Moon you can just pile up regolith, AKA lunar dirt, over the hab structures. But at this stage we only need a few fully shielded habs.)
     Booking a hab roomette as a hotel room might come to about $10,000 per night minimum — more inflated than the price of food, because the thing is so heavy. There may be bad hotels in space, but at this level of development there are not yet any cheap ones.
     For 10,000 people in low orbit, thus about 100,000 tons of habitat, plus we might suppose another 100,000 tons of other facilities such as those Xollywood sound(less) stages. Annual orbit lift needed to support, maintain, upgrade, and expand it all might come to 30 percent of the total, 60,000 tons.

     Suppose we have two main classes of cargo lifters. Most carry up about 25 tons, and are cargo counterparts of the passenger shuttles. About a fifth are heavy lifters, 100 tons to orbit, carrying about half the total load. Average payload is 40 tons, so 1500 flights per year, about five daily including one heavy lifter.
     The fleet of cargo shuttles comes to about forty vehicles, so altogether our orbital shuttle fleet approaches a hundred (two-stage) vehicles.
     The thousand people on the Moon, and the other thousand or so elsewhere in orbital space, also need room and board — coming to some 40,000 tons of imported structures, and about 12,000 tons per year in up-bound cargo traffic from Earth, half of it going to the Moon.
     To carry this cargo up we will need a few more shuttles, and to take it on outward we need a small fleet of cargo ships. Let each carry 60 tons of cargo — comparable, for these longer trips, to the 50 seats aboard the passenger ships — and we have a couple of cargo moonships per week as well as the passenger ship. Altogether the cargo fleet working beyond low Earth orbit will number about a dozen ships — add the passenger fleet for a total of around 20.

     So we come full circle to the weekly (passenger) moonship. A ticket will not come cheap, because lunar propellant is probably not yet competitive for use on low Earth orbit.
     Propellant sent up from Earth to an orbital depot is a relatively simple bulk payload suited to maximum streamlining of operations, and the price might get pushed down to $50,000 per ton. A ton of lunar propellant delivered to low Earth orbit needs at least another ton or so to get it there, even with solar electric kites for the second leg of the trip, so the price point to match for lunar production is around $25,000 per ton at the source.
     Moreover, rocket propellant uses a larger proportion of hydrogen than ice contains, thus perhaps two tons of ice per ton of propellant extracted. Altogether, to make lunar propellant competitive in low Earth orbit you may need to bring production cost down to $250 per ton of lunar regolith that must be crunched to obtain the ice — a pretty demanding order for mining on the Moon.
     Lunar propellant is much more competitive in lunar space, versus propellant lifted all that way from Earth, but low Earth orbit will favor Earth-sourced propellant for a long time, even permanently if launch costs come down enough.
     Our weekly moonship needs about four tons of propellant per passenger, costing $200,000 on orbit (and not counting, for Earth passengers, their ticket to orbit). All in all, upwards of a quarter million on average to fly to the Moon. Robert Heinlein, writing in 1949, pegged the full Earth-to-Moon lift at $30 per pound — equivalent, at current prices, to $299.75 (almost exactly 10x inflation), or $660,649 per ton. So we are beating Heinlein's price hands down.
     That said, even filling that last empty seat will set you back a minimum of $30,000 in propellant to lift you and your baggage. But hey, a best-case total of maybe $50K or so to fly to the Moon? Not shabby.

     Stepping back, the vision I have sketched here looks very much on the same scale as what Kubrick and Clarke gave us in 2001: A Space Odyssey. One estimate for the mass of Space Station V in the film comes to 68,000 tons, about a third of my estimate for total low-orbit presence.
     The operating technology I've presumed — chemfuel rockets for all routine operations — is speculation-free, aside from the bit of magitech faerie dust needed to make space operations routine. We probably could have done it by 2001, had space development continued at the white hot pace of 1968.
     The whole shebang — shuttles, orbital stations and habs, moonships and Luna base, all of it — has a combined mass somewhat less than 300,000 tons. By my million-dollars-per-ton guesstimate, which applies to commercial airliners — and expendable rocket stages — today, it would cost us not quite a third of a trillion dollars to build it all, and $100 billion or so to operate it each year.
     In an earlier development stage, when spacecraft are still largely handbuilt prototypes, the same money will only buy about a tenth as much — still a respectable start: a thousand people in space, a hundred on the Moon, the cost falling and development expanding as experience is gained and economies of scale kick in.

     But enough of the big picture, except for the biggest picture of all, the one outside the viewport. Ladies and gentlemen, moonship Henry Mancini is now ready for boarding at Airlock Ten-Alpha. Please glance at the ticket scanner as you pass by, and have a wonderful trip! Damy i gospoda, kosmicheskiy korabl' na Lunu Genri Manchini gotov ... (Ladies and gentlemen, the spacecraft to the moon Genri Manchini is ready)

From THE WEEKLY MOONSHIP by Rick Robinson (2015)

Satellites are extremely expensive to build and operate – a fact that makes their short life even more troublesome for their owners and operators. One of the largest contributors to a satellite’s eventual demise is running out of fuel and not having the fuel necessary for station-keeping, maneuvering and other requisite operations.

However, there could be a solution on the horizon that could extend satellite life through strategic refueling.

In June of this year, SSL MDA Holdings – a global communications and information company – announced the formation of Space Infrastructure Services LLC (SIS), a new company that will offer commercial satellite servicing capabilities, including refueling. In addition to announcing the formation of the company and the introduction of these services, they also announced the company’s first customer – SES.

Carlo Tommasini, the Vice President of Fleet Engineering at SES recently gave an interview about why SES decided to move in the direction of in-orbit refueling, and why this could have a major impact on the future of the satellite industry. Here is what Carlo had to say:

Q: Refueling a satellite on-orbit with minimal disruption on the operations of the spacecraft sounds like a scene from a science fiction movie. How does it work?

Mr. Tommasini: MDA’s refueling approach is conceptually similar to a travelling space gas station that is capable of refueling satellites through robotic arms. MDA relocates the space gas station (robotic servicer) to the orbital location of the SES satellite where it docks to the aft end of the SES satellite for approximately nine days.

While the SES satellite continues providing customer services, automatic and tele-operated robotic servicing tools are used to survey the SES satellite, manipulate thermal blankets, valves and pump fuel. After the fuel transfer is completed, the worksite is closed and the robotic servicer undocks from the SES satellite and moves away. Thereafter, the SES satellite operates standalone and can continue to serve our customers beyond its usual 15 year-lifespan.

Q: What are the concrete benefits that this technology will deliver to SES?

Mr. Tommasini: Many satellites are healthy and in good operating condition in-orbit, and are able to operate beyond their 15 years design life. For these satellites, the limiting lifetime factor is the remaining fuel on board to maintain attitude control and orbital position station-keeping.

For satellites low on propellant, satellite in-orbit refueling provides life extension – maintaining revenue streams for the company and providing time to determine the optimal fleet management strategy.

Q: SES is the first commercial satellite operator to sign up for these in-orbit refueling services. With no previous users or case studies, how can the company be confident in this new technology?

Mr. Tommasini: MDA is a leader in space robotics and automated systems capable of enabling on-orbit servicing missions. SSL is a leading supplier of commercial GEO satellites and is also designing the satellite servicing spacecraft vehicle for the US Defense Advanced Research Projects Agency (DARPA) Robotic Servicing of Geosynchronous Satellites (RSGS) program.

We have spent months working closely with MDA and SSL to jointly develop the refueling services concept to meet SES’s needs. As SSL embarks on building the servicer, SES will be closely involved in reviewing the design and performance. This service – when ready – will bring powerful options to our fleet management capabilities. Together with the MDA and SSL, we are proud to be pioneering this technology.

Q: When can we expect to see the first SES satellite benefitting from MDA’s satellite in-orbit refueling service? Which satellite will be the first to get services?

Mr. Tommasini: SSL’s satellite servicing spacecraft is planned for launch in 2021, so we are hoping that would be the year where we would see our first SES satellite benefitting from this on-orbit refueling service.

It’s a little too soon to [identify the first satellite to be serviced] at this stage. There are a couple of factors that we need to consider — the strategic importance of the orbital location, long-term fleet plans, projected market dynamics at that point in time, and – most importantly – customer requirements. It is of utmost importance for us to make sure that our customers have business continuity at all times.


(ed note: Cassell, captain of a consolidator spacecraft, is giving a prospective new employee a test of their piloting skills.)

Suzi’s voice came from a console speaker on the bridge of the consolidator Turner Maddox, owned by Fast Forwarding Unincorporated, drifting 250 million miles from Earth in an outer region of the Asteroid Belt.

“Spider aligned at twelve hundred meters. Delta vee is fifteen meters per second, reducing.” Her voice maintained a note of professional detachment, but everyone had stopped what they were doing to follow the sequence unfolding on the image and status screens.

“No messing with this kid, man,” Fuigerado, the duty radar tech, muttered next to Cassell. “He’s going in fast.”

Cassell grunted, too preoccupied with gauging the lineup and closing rate to form an intelligible reply. The view from the spider’s nose camera showed the crate stern on, rotating slowly between the three foreshortened, forward-pointing docking appendages that gave the bulb—ended, remote-operated freight-retrieval module its name. (the spider is a "catcher" for cargo crates flung at it by remote mass drivers) Through the bridge observation port on Cassell’s other side, all that was discernible directly of the maneuver being executed over ten miles away were two smudges of light moving against the starfield, and the flashing blue and red of the spider’s visual beacon.

As navigational dynamics chief, Cassell had the decision on switching control to the regular pilot standing by if the run-in looked to go outside the envelope. Too slow meant an extended chase downrange to attach to the crate, followed by a long, circuitous recovery back. Faster was better, but impact from an overzealous failure to connect could kick a crate off on a rogue trajectory that would require even more time and energy to recover from. Time was money everywhere, while outside gravity wells, the cost of everything was measured not by the distance moved, but by the energy needed to move it there. A lot of hopeful recruits did just fine on the simulator only to flunk through nerves when it came to the real thing.

“Ten meters per second,” Suzi’s voice sang out.

The kid was bringing the crate’s speed down smoothly. The homing marker was dead center in the graticule, lock-on confirming to green even as Cassell watched. He decided to give it longer.

The Lunar surface was being transformed inside domed-over craters; greenhousing by humidifying its atmosphere was thawing out the freeze-dried planet Mars; artificial space structures traced orbits from inside that of Venus to as far out as the asteroids. It all added up to an enormous demand for materials, which meant boom-time prices.

With Terran federal authorities controlling all Lunar extraction and regulating the authorized industries operating from the Belt, big profits were to be had from bootlegging (transporting illegal goods) primary asteroid materials direct into the Inner System. A lot of independent operators (illegal or pirate miners) got themselves organized to go after a share. Many of these were small-scale affairs—a breakaway cult, minicorp, even a family group—who had pooled their assets to set up a minimum habitat and mining-extraction facility, typically equipped with a low-performance mass launcher. Powered by solar units operating at extreme range (barely 10% of the solar power available at Terra), such a launcher would be capable of sending payloads to nearby orbits in the Belt, but not of imparting the velocities needed to reach the Earth-Luna vicinity.

This was where ventures like Fast Forwarding Uninc. came into the picture. Equipped with high-capacity fusion-driven launchers, they consolidated incoming consignments from several small independents into a single payload and sent it inward on a fast-transit trajectory to a rendezvous agreed upon with the customer.

Consolidators moved around a lot and carried defenses. The federal agencies put a lot of effort into protecting their monopolies. As is generally the case when fabulous profits stand to be made, the game could get very nasty and rough. Risk is always proportional to the possible gain.

“Delta vee, two point five, reducing. Twenty-six seconds to contact.”

Smooth, smooth—everything under control. It had been all along. Cassell could sense the sureness of touch on the controls as he watched the screen. He even got the feeling that the new arrival might have rushed the early approach on purpose, just to make them all a little nervous. His face softened with the hint of a grin.

As a final flourish, the vessels rotated into alignment and closed in a single, neatly integrated motion. The three latching indicators came on virtually simultaneously.

“Docking completed.”

“Right on!” Fuigerado complimented.

Without wasting a moment, the spider fired its retros to begin slowing the crate down to matching velocity, and steered it into an arc that brought it around sternwise behind the launcher, hanging half a mile off the Maddox’s starboard bow. It slid the crate into the next empty slot in the frame holding the load to be consolidated, hung on while the locks engaged, and then detached. (When enough crates are consolidated in the frame to constitute a full load, the mass driver launches it to Earth-Luna)

(ed note: So Fast Forwarding Uninc. moves their high-powered mass driver and spider "catcher" to new covert point X. Their bootleg miner clients use low-powered mass drivers to launch crates of illegal ore to point X. Fast Forwarding uses the spider to catch the incoming crates and uses their high-powered mass driver to launch the crates to buyers at Earth-Luna. Then sends a bill to the bootleg miner clients.

Fast Forwarding relocates their mass driver often to avoid being raided by the Feds. And the mass driver has defensive arms in case they didn't relocate soon enough.)

From MADAM BUTTERFLY by James Hogan (1997)

(ed note: This is for the Traveller role playing game. In the game, starships usually refuel at a spaceport but can refuel by skimming gas giants in the wilderness. Some star-captains avoid spaceports in favor of gas giants because it saves money. Unfortunately there are no space stations around such gas giants for your journey weary crew's benefit. The government of the solar system may notice a business opportunity.)

Okay ships use wilderness refueling to save credits. However, their crews do have money to spend. While their captain won't want to head for the mainworld, which has no market for his cargo, the crew still wants some leave. Even a few hours. Smart captains will give a little. Forward thinking world governments will see a way to make some bucks off passing ships.

Presenting Last Chance Outposts. Also known as side ports, gas 'n goes and a variety of less wholesome names.

Many worlds with a C starport or worse establish a space station near the inner gas giant. Sometimes it's an orbiting base. Other worlds use one or more large insystem craft, the better to meet captains eager to make their schedule. The mobile outposts carry a variety of merchandise, spares, filters, vacc suits, ship's locker items and personal weapons.

A number of outposts have very basic repair services have basic repair stations and a large EVA crew to perform them for ships that have been damaged during refueling. Without exception such repairs always take at least a few hours allowing the ship's crew to partake of the other outpost services.

An outpost will have a restaurant of some type. They vary in quality though most at least serve fresh food. After all the crew can get microwaved packaged crap onboard for nothing. Other shops will sell local goods such as luxury items or handcrafts all at steep mark up.

There is usually a compartment or several reserved for various illicit activities. These red lit corridors have almost anything you could imagine for sale or rent though what's illicit varies wildly from world to world. You might wind up in a coffee bar or out of uniform. Note this section is not openly advertised and requires some Streetwise or Steward skill to learn about and enter (as well as credits).

Finally each outpost has a cargo hold filled with a variety of items for speculation. A lot of haggling happens here. A great many items are organic in nature. Dumping food cargos due to spoilage, mold or fungal infection is common. So common that no one really looks into it. Some dumped cargoes find their way to an outpost where they can be bartered for other organics leaving no paper trail for the revenue services to follow and tax.

Other cargos can find their way to the cargo hole depending on how believable a story the captain can come up with. You might get away with saying you dumped some pcs with viruses downloaded from the factory that weren't worth debugging for example or saying you got swindled on some goods and threw them out the airlock ("What the hell are 'Bollex' wrist chronometers?!")

Some outposts are owned outright by the mainworld governments. The mobile outposts are often franchise owners moving from system to system or in many cases squatters on the gas giants of worlds that haven't the means of chasing them off or assuring they get a cut of the profits.

Another lucrative role for these entrepreneurs is as camp followers, tagging along behind a large mercenary group or an invasion force catering to the military's whims. War can be a cash cow no matter who wins.

From Gas (Giant) and Go! by Rob Garitta (2015)

While there maybe those who have a preference for development of cislunar space and/or the Moon according to some plan decreed by government diktat, my years in economics and finance and banking have shown me that the growth (and death) of industries and companies is a very messy affair once you get down into the trenches. The markets that the United States provided in the past embraced the chaos and let free men trade as they would, because it was out of the chaos that the best ideas emerged through competition with other ideas in open markets where people can make informed decisions. Bad ideas and bad practices can only occur in markets where the Sun does not shine adequately, and the participants in the market are deceived by shadows. Unfortunately, far too often, it is government itself that is casting those shadows.

As an advocate for free market cislunar and Lunar development, and President of The Moon Society, I am often asked “So what kind of business is there to do in space and on the Moon?” As if any one person would have all the answers, but research in the Lunar Library has shown that the question has certainly not gone unpondered. Too often, though, there is a fixation on one particular aspect, a particular product or service, which is thought to be the driver, the killer app that will unlock vast new wealth and make everything else happen by default. That, combined with the framework that NASA has provided for U.S. space activities over the decades, has unfortunately put blinders on what could be considered, and quite frankly has hampered our ability to move forward.

Embrace the chaos of free markets. The first thing to understand is that we are not going to go straight to the Moon and then begin backfilling cislunar space with commercial activity, although some folks advocate for such. What’s going to happen is that activity is going to expand outward, and once activity has reached the neighborhood of the Earth-Moon L-1 point, the Moon (and so much more) becomes a no-brainer. EML1 is the killer app of cislunar space, to the extent one might exist.

Earth to orbit

So how is this going to happen? Suborbital gets to market first. The obvious contenders are Virgin Galactic, Blue Origin (though does anyone really know what they’re doing?), and XCOR for crewed, and Masten Space Systems and Armadillo Aerospace for uncrewed flights, although it has been suggested that Armadillo’s products could support “spacediving” activities.. After the initial round of prepaid pioneers are flown off, look for microgravity science payloads to become an increasing segment of the straight up-and-down market, and look for suborbital to expand into the point-to-point market for persons and goods. (When it absolutely, definitely has to be there today.) Expect strong seed capital from NASA in the early stages of the microgravity science utilization, just as happened back in the 1990s with NASA’s Space Commercialization Centers, but really universities, foundations, and even companies should be stepping up with funding and payloads. And not just funding they’ve received from NASA, but with their own monies so that they really own the results.

We’re already seeing excitement in this area, as exemplified by the Next Generation Suborbital Researchers Conference at the end of February. Some payloads are even getting to orbit through the CubeSat program, and NanoRacks LLC is offering commercial access to ISS, even showing their upcoming launch manifest on their homepage. A lot of folks deride microgravity science as a pointless endeavor, pointing to the general lack of results that have ended up in the consumer sector. The issue, though, is not a lack of potential in the sector, but rather the constraints in which it has operated to date. Sounding rockets are limited in what they offer, and being automated one hopes the black box works the first time. The Shuttle was never able to provide a reliable and consistent, or even frequent, launch schedule, and the demand for space always overwhelmed the limited supply. Challenger was a serious blow to the kneecaps as well.

When the author inquired about paying for a Hitchhiker payload, the reply (in 2002) was that there were over 60 GASCans waiting to go, paying your own freight did not move the payload ahead in the queue before freeriders (and if NASA felt a subsequent payload was more scientifically meritorious it could be bumped ahead of paying customers), and not every Shuttle flew GASCans. Not a promising platform for building a vacuum sphere business (glass spheres ‘filled’ with the vacuum of space), and what other options were there? Astrotech [NASDAQ-CM: ASTC] subsidiary Astrogenetix has had better luck recently working on vaccines against some of the more virulent staph bugs based on results from flown hardware.

Another entrepreneurial idea the author had back in the day was to go around and quietly buy up the various flown boxes. These would be refurbished and then leased to scientists who wanted to do research without having to engineer their own. The presumption was the fact that these were flown instruments, previously cleared for flight on the Shuttle, and this would help facilitate the processing for any subsequent flight, as NASA was already familiar with the instrument. Well, we all know what happens when you presume. The ultimate priority, though, is to get scientists to orbital lab benches.

First, we need to get the crew to orbit problem solved. We’ve got good rockets, and we’re working on the crew vehicles. An optimistic timeline is within three years, but the equation involves a large NASA variable that could easily push that out to five or six or even more years. Until private industry gets to the point where it is going to space in spite of NASA, not because of it, the timeframe will tend to push outwards. The basic solution to accelerate private sector development is to enable more direct investment by individual, but not necessarily qualified, investors, so that more investment capital can be directed into the industry. There is legislation in the works to better enable equity investment, for example through crowd-sourcing, enabled by our much more capable computing abilities (itself enabled by Apollo).

It does rather seem a shame to have to ask the government for permission to invest in a collective manner in a company and industry in which I believe and actually know something about (notice how few of the companies named have stock tickers noted). I shouldn’t have to jump through a million hoops to invest in companies I see addressing particular needs for which I envision markets. Some examples of such companies include Orbital Outfitters, which develops spacesuits; Altius Space Machines, whose “Sticky Boom” technology for non-consensual docking maneuvers could also have applications for debris salvage operations; and Celestis, which takes cremains to orbit and has a 30-year legacy.

Space development is going to start out with lots of small companies exploiting particular niches. Other examples of niche exploitation include Wyle Labs, which focuses on human performance services for commercial human spaceflight customers, and NASTAR, which describes itself as “the premier air and space training, research, and education facility in the world”. Ball Aerospace [NYSE: BLL] serves a variety of niches, such as remote sensing, astronomy, optics, laser communications, data exploitation, low-observable antennas and precision cameras. Draper Labs has a specialty in advanced guidance, navigation, and control systems; high-performance space science instruments; and reliable and high-performance processing systems. Honeybee Robotics focuses on developing technology and products for next-generation advanced robotic and spacecraft systems that must operate in increasingly dynamic, unstructured and often hostile environments. Stone Aerospace’s Shackleton Energy Company envisions robotic access of the Lunar poles in the not too distant future. Paragon SDC identifies itself as “the premier provider of environmental controls for extreme and hazardous environments”, and has partnered with Google Lunar XPrize competitor Odyssey Moon to grow a plant on the Moon. Analytical Graphics provides software for orbital analysis. MacDonald, Dettwiler and Associates provides robotic arm services for on-orbit facilities. Harris Corp. designs specialized antennas. Andrews Space offers a range of technical competencies from space system design and rapid prototyping to business analysis. There are many niches to be exploited in the still fledgling commercial space industry.

We must not shy away from fear of failure. While Beal Aerospace may have gone out of business, it did allow SpaceX to pick up nice engine test facilities outside of Waco, Texas. People will get bamboozled and they will lose money, but it happens in every industry in every country on the planet. It’s bad that it happens, as it represents malinvestment, but we can’t seem to make it go away.

Getting crewed vehicles online is critical to any further development. If it can’t be done, what follows is meaningless. Current optimistic projections run somewhere in the 2015 timeframe for test flights; maybe a bit before, maybe a bit later. Expect at least one critical flaw or disaster that will lead to new protocols of some sort or another. The best things that NASA can do in this regard is purchase rides for their astronauts, just as they do from Roscosmos, and promulgate universal, international interfaces (in metric) like docking ports and communications standards, as well as work with industry to ensure the highest quality space product in the market.

Current efforts in the US to provide crewed vehicle to orbit capability include Blue Origin’s vehicle efforts, Boeing’s [NYSE:BA] CST-100 capsule, Sierra Nevada Corporation’s Dream Chaser lifting body, and SpaceX’s Dragon capsule. Development of all four have been supported by NASA’s Commercial Crew Program through funded Space Act Agreements. SpaceX’s Dragon started development through NASA’s Commercial Orbital Transportation Services (COTS) program, alongside Orbital Sciences Corporation’s [NYSE: ORB] Cygnus vehicle. In addition, NASA has its own Orion Multi-Purpose Crew Vehicle (MPCV) capsule program.

Offering good insight into what kinds of things private industry launch to orbit might enable are the Concept Exploration & Refinement (CE&R) studies that NASA conducted back in 2004 after the Vision for Space Exploration was released. These tapped into work done by NASA’s Decadal Planning Team around the turn of the millennium, which continues in the form of the Future In-Space Operations (FISO) Working Group.

Low Earth orbit (LEO)

Once in orbit, there are more possibilities enabled. While we’re limited at the moment to the ISS up in a 51.6° inclination orbit, there are other inclinations that may be of interest. Once Bigelow Aerospace is able to provide usable space on orbit with their BA330s, and transportation can be adequately provided (one of the reasons that crew vehicles should be compatible with Falcon, Delta, and Atlas rockets), there are a number of uses that can be imagined. It’s not clear whether Bigelow is going to adopt the current ISPR standards for equipment (which would re-open the black box leasing idea from earlier), or perhaps implement a new standard that would tie users to the BA330s.

Where would these inclinations be? Where are the launch sites? Equatorial would be one, easily accessible from Kourou, but the scenery from orbit is pretty boring overall. Kennedy’s inclination is an obvious choice for NASA activities. An inclination of about 40° overflies most US launch sites, from Spaceport America to MARS. And it’s entirely possible that more facilities will be added in the ISS inclination. Whatever facilities are put on orbit, they will likely be in the inclinations most readily accessible from terrestrial launch sites.

What to do? What not to do? My favorite option is microgravity sciences. “Space Industrialization Opportunities” by Jernigan and Pentecost is a great academic introduction to the topic. A more contemporary introduction is “A World Without Gravity” from ESA. Ceramic metals. Glass metals. Foamed metals. Bizarre alloys impossible in the gravity well. Optics. There is so much research to be done, much of it with real market potential. The faster that suborbital flights can provide capability to microgravity researchers, the better it can serve as a springboard to when we do get facilities in orbit. Once on orbit, things like free-flyer platforms should be considered to co-orbit with the facilities. The research to be done there will lay the groundwork for later production processes undertaken farther out in cislunar space. NASA is supporting these researchers, but more support must come from academia and industry.

Being much traveled, I understand the joy of visiting new places in person and exploring my world corporeally. It’s all about the senses, and having flown a Zero-G flight (back in 2004; even got a “barf quote” in the local paper), I am sensitive to the impact of the different gravity environments and their effects on the senses. I highly recommend it, especially Lunar gravity. It’s an absolute joy. Once facilities are on orbit, they will become a destination for travelers seeking new experiences, new vistas, and new destinations, plus their tickets help pay the rent. This is a proven fact by the number of non-governmental-employees who have already visited the ISS, and even Mir before that, through the work of companies like Space Adventures. Even the Shuttle had members of Congress as fellow travelers, and private citizens working for companies.

While some will purchase their ticket to orbit, others will have to work their way up there. There’s no shame in being the steward of a space hotel, even if it may be rather unpleasant at times. Don’t forget the movie industry, which may decide it wants to incorporate more microgravity effects in its storytelling. There will also be those who want to conduct their research away from prying eyes and corporate and governmental malefactors. Speaking of governments, if an open crew transport market becomes available, as well as usable space on orbit, expect a number of governments to consider pursuing their own national agendas from an orbital platform as a means of showing off to their neighbors their technological prowess. It may also arise that satellites and probes end up being launched to the vicinity of orbital facilities for a post-launch checkout before being sent on their way. In this way, many expensive failures can be avoided. What if, for example, Phobos-Grunt had been launched to the vicinity of an orbital facility, and for a few million dollars could have had an engineering team pay it a visit to figure out what’s going on?

So there are many possibilities awaiting us just in LEO. Having an open market means that no one can predict what will happen and what whacky ideas will turn out to be cornucopias of wealth. Looking out past LEO, there are a number of possibilities, with GEO being the obvious choice. But GEO is expensive in terms of fuel, even if we are smart enough to put gas stations in the local neighborhood in LEO. For many, including engineers who have taken Economics for Engineers 101, this quickly leads logic to heavy-lift launch vehicles as the solution for providing adequate volumes of propellant. A subtler read of the situation suggests that you can’t lead the market to where it’s going, and what is needed now is more frequent use of existing, mass-produced launch vehicles to help drive economies of scale into a virtuous cycle of growth. Having facilities on orbit will be beneficial in that regard, but cannot provide the sole solution. Over the near term, it makes sense to deliver propellant to orbit in more frequent but smaller amounts, as that helps to make the cost of rockets cheaper for everyone. It will get to the point where “heavy” lift (let’s say over 100 metric tons at a time for the sake of argument) will make sense because of the volume of traffic that is going to orbit, but that time is not now. The Russians already figured this one out years ago.

Additionally, by the time there is enough volume going to orbit to consider heavy lift that will also be the time where reusable launch vehicles (RLVs) become a compelling solution. Materials research on orbit is likely to have helped advance that field in some regard (such as, perhaps, lightweight foamed metal cores for aerospike engines). It will be a decision point, and the likelier path is RLV transport, as the economics will make as much if not more sense than HLV. Having RLV transport will also much more greatly enable further growth in LEO, and further support efforts to go trans-LEO. This could happen as early as 2020, but more likely 2030 or beyond.

A more strategic consideration is towards things like space as an export market. In principle, a product shipped from a US launch site to, for example, an Isle of Man flagged facility like those proposed by Excalibur Almaz, would be an export. Would it be possible to get EXIM Bank financing? Coupled with Zero-G Zero-Tax type initiatives that helped get Internet-based commerce kickstarted, these could significantly facilitate interest in and growth of cislunar commerce. Whatever solutions arise, it won’t be an easy process, as noted by Near Earth LLC in a presentation at the NewSpace 2011 conference last July.

Geosynchronous/Geostationary Orbit (GEO)

GEO is sometimes referred to as the Clarke Orbit, after Sir Arthur C. Clarke, who noted its utility by applying some simple mathematics. While Sir Clarke envisioned large stations crewed by workers busily replacing blown vacuum tubes, what we’ve ended up with is a hodgepodge of telecommunications and broadcast satellites of increasing size and sophistication. The use of GEO is tightly controlled by the International Telecommunication Union, but over time a large number of inoperative objects have accumulated. These do not go stumbling about like their name, “zombiesats”, might imply. Rather, through a peculiarity of gravity (the gravitational lumpiness of Earth) and orbital energies, and centrifugal force, the objects tend to cluster in areas where there is a bit less gravitational pull from Earth, the two most obvious being the gouge dug out by India as it sped north into the Himalayas, and an area in the Pacific off the coast of the Americas. The latter, about 105° W, is an area of particular crowding and concern.

There have been ongoing efforts to address the problem robotically, such as EPFL’s proposed CleanSpaceOne, MDA’s [TSX: MDA] Space Infrastructure Servicing vehicle, and SkyCorp’s satellite life extension spacecraft. Still, companies may prefer some on-site supervision when revenue-generating satellites are at risk.

Broadcasters are pushing for larger satellites and more power, so that your direct-to-home television signals won’t fade out in a heavy rainstorm. Other interests are looking into solar power satellites, which would find an ideal home in GEO, which would allow a fixed broadcast point and constant source for the beamed energy. Most of our energy supply is second- or third-hand solar power, so why not go directly to the source?

So the basic agenda for GEO is:

  1. Garbage cleanup
  2. Bigger broadcast and telecom platforms
  3. Space-based solar power satellites
From THE CISLUNAR ECONOSPHERE (PART 1) by Ken Murphy (2012)

Laser Launching

Laser Launching is a remarkable inexpensive way to get payload into LEO (aka "Halfway to Anywhere"). Unfortunately it requires lots of money for creating the initial facillity.

Genius Freeman Dyson believes it would be a good investment for a country such as the United States to build a laser-launch site and charge a modest fee to anybody who wanted to boost a payload into orbit. Such as mom & pop asteroid mining businesses. This is similar to the political motivation behind the US transcontinental railroad mentioned here.

An affordable space-going version of a Prairie Schooner could be purchased by private individuals, boosted into orbit for a modest fee by laser launch, then another modest fee to an ion-drive tug to join the wagon train to Luna, Mars, or the Asteroid belt. LEO is halfway to anywhere, remember? This would also allow grizzled old asteroid miners to go prospecting in the belt.

For a possible space-going Prairie Schooner, take a look at the Spacecoach concept.


That's the concept, and I think I was the first to use it in a science fiction story. Imagine my surprise, then, when at an AAAS meeting I heard Freeman Dyson of Princeton's Institute for Advanced Studies give a lecture on laser-launched systems as "highways to space."

Dyson is, of course, one of the geniuses of this culture. His Dyson spheres have been used by countless science fiction writers (Larry Niven cheerfully admits that he stole the Ringworld from Dyson). One should never be surprised by Freeman Dyson—perhaps I should rephrase that. One is always surprised by Freeman Dyson. It's just that you shouldn't be surprised to find you've been surprised, so to speak.

Dyson wants the U.S. to build a laser-launching system. It is, he says, far better than the shuttle, because it will give access to space—not merely for government and big corporations, but for a lot of people.

Dyson envisions a time when you can buy, for about the cost of a present-day house and car, a space capsule. The people collectively own the laser-launch system, and you pay a small fee to use it. Your capsule goes into orbit. Once you're in orbit you're halfway to anyplace in the solar system. Specifically, you're halfway to the L-5 points, if you want to go help build O'Neill colonies. You're halfway to the asteroid Belt if you'd like to try your hand at prospecting. You're halfway to Mars orbit if that's your desire.

America, Dyson points out, wasn't settled by big government projects. The Great Plains and California were settled by thousands of free people moving across the plains in their own wagons. There is absolutely no reason why space cannot be settled the same way. All that's required is access.

Dangerous? Of course. Many families will be killed. A lot of pioneers didn't survive the Oregon Trail, either. The Mormons' stirring song "Come Come Ye Saints" is explicit about it: the greatest rewards go to those who dare and whose way is hard.

That kind of Highway to Space would generate more true freedom than nearly anything else we could do; and if the historians who think one of the best features of America was our open frontiers, and that we've lost most of our freedom through loss of frontier—if they're right, we can in a stroke bring back a lot of what's right with the country.

Why don't we get at it?

Dyson envisions a time when individual families can buy a space capsule and, once Out There, do as they like: settle on the Moon, stay in orbit, go find an asteroid; whatever. It will be a while before we can build cheap, self-contained space capsules operable by the likes of you and me; but it may not be anywhere as long as you think.

The problem is the engines, of course; there's nothing else in the space home economy that couldn't, at teast in theory, be built for about the cost of a family home, car, and recreational vehicle. But then most land-based prefabricated homes don't have their own motive power either; they have to hire a truck for towing.

It could make quite a picture: a train of space capsules departing Earth orbit for Ceres and points outward, towed by a ship something like the one I described in "Tinker." Not quite Ward Bond in Wagon Train, but it still could make a good TV series. The capsules don't have to be totally self-sufficient, of course. It's easy enough to imagine way stations along the route, the space equivalent of filling stations in various orbits.

Dyson is fond of saying that the U.S. wasn't settled by a big government settlement program, but by individuals and families who often had little more than courage and determination when they started. Perhaps that dream of the ultimate in freedom is too visionary; but if so, it isn't because the technology won't exist.

However we build our Moonbase, it's a very short step from there to asteroid mines. Obviously the Moon is in Earth orbit: with the shallow Lunar gravity well it's no trick at all to get away from the Moon, and Earth's orbit is halfway to anywhere in the solar system. We don't know what minerals will be available on the Moon. Probably it will take a while before it gets too expensive to dig them up, but as soon as it does, the Lunatics themselves will want to go mine the asteroids.

There's probably more water ice in the Belt than there is on Luna, so for starters there will be water prospectors moving about among the asteroids. The same technology that sends water to Luna will send metals to Earth orbit.

Meanwhile, NERVA or the ion drive I described earlier will do the job. In fact, it's as simple to get refined metals from the Asteroid Belt to near-Earth orbit as it is to bring them down from the Lunar surface. It takes longer, but who cares? If I can promise GM steel at less than they're now paying, they'll be glad to sign a "futures" contract, payment on delivery.

It's going to be colorful out in the Belt, with huge mirrors boiling out chunks from mile-round rocks, big refinery ships moving from rock to rock; mining towns, boomtowns, and probably traveling entertainment vessels. Perhaps a few scenes from the wild west, or the Star Wars bar scene? "Claim jumpers! Grab your rifle—"

Thus from the first Moonbase we'll move rapidly, first to establish other Moon colonies (the Moon's a big place) and out to the Asteroid Belt. After that we'll have fundamental decisions to make. We can either build O'Neill colonies or stay with planets and Moons. I suspect we'll do both. While one group starts constructing flying city-states at the Earth-Moon Trojan points, another will decide to make do with Mars.

From A STEP FARTHER OUT by Jerry Pournelle (1979)

Orbital Tug


The reason an orbital tug is attractive is that rockets can launch much heavier payloads to a low orbit than they can to a high orbit. If the rocket does not have to launch hardware for moving the payload to a higher orbit then mass is saved, allowing the customer to use a cheaper launch vehicle or to launch a heavier payload for the same price.

An orbital transport provider would use a spacecraft, commonly called a tug or taxi, to deliver a payload to a different orbit. Ideally this vehicle would be reusable. This has been an area of active research since the 60's if not earlier, but I would argue that the ESPA ring and particularly the LCROSS mission represent a major step forward. The next step in this vein is probably the SSPS / Sherpa proposal from Spaceflight Inc for smaller payloads. Larger payloads could be handled by a Boeing ACES, Lockheed Martin Jupiter, ISRO PAM-G, RKK Energia Parom or Ad Astra concept vehicle. Of those, only Boeing and ISRO are known to be testing hardware. As far as I know, Boeing is the only contender investing heavily in microgravity cryogenic fluid management; this is a serious roadblock to in-flight refueling, which is a fundamental requirement for reusable tugs.

Ion-powered vehicles are popular concepts since they are so fuel-efficient. One drawback is that an ion-powered spiral from LEO to GEO exposes the payload to the Van Allen radiation belts. A possible solution is for the tug to provide radiation shielding for its payload during transit.

The Jupiter proposal is an example of a reusable tug with no depot. Tug fuel is included on the same launch vehicle as the payload. This is an efficient approach that minimizes risk in the near term. On the other hand, using a depot would allow the tug operator to purchase fuel at the lowest available launch cost and free up all available capacity on the customer's launch vehicle for their payload.

Satellite maintenance is in some ways an extension of an orbital tug. Either fuel or replacement parts are taken from LEO to the satellite's orbit. The craft is fueled, repaired or maintained in position while still operating. The largest market for this service is probably geosynchronous communication satellites, where receiving extra RCS fuel could extend their service lifetime by a decade or more. NASA has done in-space research on this subject under the Robotic Refueling Mission on ISS. Vivisat and MDA have both done work on commercial refueling services, with MDA's entry including a manipulator arm that could be used for ORU-style maintenance as well as refueling.

Adding the ability to swap out solar panels and transponders, a satellite bus could double its profitable lifespan. To take advantage of this the satellite needs to be designed for on-orbit maintenance from the beginning, similar to the way the ISS uses orbital replacement units.

An extension of this would be for a tug to retrieve a satellite and deliver it to a manned repair facility. Satellites with power or communication failures could be rescued or recovered this way, examined by human technicians, then possibly repaired and returned to their service orbit depending on the damage. Right now satellite operators are required to provide their own end-of-mission contingency; in most cases that means reserving a significant chunk of RCS fuel to either deorbit or move to GEO parking orbit. Having a service tug available might allow operators to eliminate that reserve, extending the useful life of satellites (potentially by several years) at the cost of a single tug mission.

In the longer term, most satellites at end of life are still structurally sound. If we start designing satellites with fully-replaceable parts then there is no reason why a GEO sat couldn't be retrieved, refueled, given new power hardware and upgraded navigation and outfitted with a new set of transponders before being placed back in GEO, all automated or remote-controlled. The basic structural bus might last many decades. Even for satellites currently in graveyard orbit, if a suitable crewed facility was available then the owners of those craft would gain considerable value from that mass by refitting or selling the bus to be refitted by someone else.


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Interplanetary Peddlers

RocketCat sez

Savvy science fiction authors like Ken MacLeod know that "History is the trade secret of science fiction." Even tired hackneyed old tropes will have new life if you put them in SPAAAAACE! Just look at Mal and Zoë riding their horses out of the starship in the classic show Firefly. Sword on a Starship or what? But in this case starship horses make sense, because if you have the same historical constraints your solutions are gonna be the same.

So the idea of rocket-propelled space peddler seems like a really stupid idea, but is it really?

And it does not have to be comedic, a re-hash of Harcourt Fenton Mudd or Cyrano Jones. Or have you forgotten about the musical Oklahoma, where Ali Hakim the peddler sells Will the deadly "little wonder?"


Oh, I'm sure you've seen this trope with media associated with the North American frontier. The peddler / Yankee trader / tinker traveling from pioneer homestead to homestead, selling the little necessities and luxuries.

But as I've mentioned many times before, futurologists and science fiction writers can save themselves tons of work by remembering that everything old is new again. The North American frontier is dead and gone, but roughly the same situation could arise in the future. I'm thinking about mom-and-pop asteroid mining operation and pioneers colonizing interstellar planets.

All three groups advance into wilderness areas with no infrastructure nor shopping malls. All of them need tools and items for survival, and certain luxuries that make life bearable. Any entrepreneur worthy of the title can see this is a business opportunity.

Now, there are differences. Peddlers in North America could travel by foot, carrying their wares on their backs. They could also obtain their wares at a modest cost. This made the trade attractive to beginner businesspeople with strong legs but little starting capital. However, a interplanetary peddler selling things to asteroid miners are going to need a space suit and a space taxi at a minimum (though the latter could indeed be jury rigged out of stuff from the spaceship junkyard). If the peddler is traveling from star colony to star colony they have to have some kind of starship. This raises the bar for entry into the business, but the bar has already been raised for the pioneer star colonists. If they can afford the interstellar transport fee, so can the peddler.

The pioneer people were also eager for any hot-and-juicy gossip the peddler could bring from the last villiage they were at. Interstellar colonists might already know all the news by virtue of their jury-rigged internet.

And of course some peddlers were con artists. That ain't gonna change in the future, not without drastic changes in human personality.

Frontier peddlers in history would often find their stock boxes growing heavier as they sold stuff. This is because many of the pioneers had no money, so they had to pay with crops, food, honey, or other barter. The peddler would lug all this barter back to more civilized regions and sell it. Asteroid peddlers would probably have to be paid in asteroid ore.

Readers who are rich with years will remember the wearisome number of jokes on the topic of the traveling salesman and the farmer's daughter. The "traveling salesman" was a peddler.


Closely related is the profession of Tinker. North American pioneers had very little money, so they could not afford to replace a broken household utensil. The tinker would use low-tech methods with inexpensive or free local materials to make the repair. To fix a hole in a pan, the tinker would make a "tinker's dam" out of clay, mud, or dough. The tinker would then pour some molten solder into the dam, which would solidify and mend the hole. The tinker's dam would be removed and thrown away, since it is literally "not worth a tinker's dam."

So in the future, Asteroid Dan: the Tinker Man would travel to Ma and Pa Kessler asteroid mine to glue together their broken antiquated laser drill. And have to be OK with being paid in fresh asteroid ore instead of cash.


Now, if times get tough (or if you are trying to take advantage of alien technology), a tinker could graduate into becoming a Cobbler.

Ma and Pa Kessler have a problem repairing their broken laser drill due to a lack of money, NOT a lack of technology. The tech is available, assuming you have coin.

If the technology become unavailable, that's when the tinkers will have to become cobblers. A tinker tries to repair broken parts. A cobbler tries to replace a broken part with some locally available equivalent.

For instance: a tinker welds together a cracked gear. A cobbler deals with a sudden absence of automobile gasoline by altering the car to run on methane (compress methane boiled off by stable-dung, and plumb a gas-supply into the induction manifold using scrap tubing and insulated tape).

Why would the technology become unavailable? Many reasons. A sudden zombie apocalypse. The galactic empire descends into the Long Night. Or if you are a combat archeologist trying to fix some million-year old alien paleotechnology, where the alien repair parts also became unavailable a million years ago.



There are many items that Terradyne either will not import for its employees in the colonies, or doesn’t have the time to bother with. This has left a void which is filled by Yankee traders, named for the peddlers who traveled door-to-door in the 18th and 19th centuries in North America.

These traders move from settlement to settlement, usually in ramshackle space ships, selling their wares and picking up items to sell in the next colony. In smaller camps they are heartily welcomed as a fresh source of news and gossip from the outside. Their stock in trade varies widely, from beef jerky and dried fruit to “spicy” VRs and print publications.

There are occasional rumors that some of the Yankee traders are actually RMA spies. If so, colonists in general tend to feel that the visits are worth being spied on.

(ed note: The RMA is the undercover intelligence agency of the successor to the United Nations. Who are always looking for ways to rein in the out-of-control Terradyne megacorporation)

From GURPS Space: Terradyne by Russell Brown and Mark Waltz (1991)

      I went back to the problem of setting our sixteen thousand tons of ship onto the rock.
     It wasn't much of a rock. Jefferson is an irregular-shaped asteroid about twice as far out as Earth. It measures maybe seventy kilometers by fifty kilometers, and from far enough away it looks like an old mud brick somebody used for a shotgun target. It has a screwy rotation pattern that's hard to match with, and since I couldn't use the main engines, setting down was a tricky job.
     There are two inertial platforms in Slingshot, and they were giving me different readings. We were closing faster than I liked.
     The attitude jets popped. "Hear this," I said. "I think we're coming in too fast. Brace yourselves." The jets popped again, short bursts that stirred up dust storms on the rocky surface below. "But I don't think—" the ship jolted into place with a loud clang. We hit hard enough to shake things, but none of the red lights came on "—we'll break anything. Welcome to Jefferson. We're down."
     Janet came over and cut off the intercom switch, and we hugged each other for a second. "Made it again," she said, and I grinned.
     There was a winking orange light, showing an outside call on our hailing frequency. Janet handed me the mike with a wicked grin. "Lock up your wives and hide your daughters, the tinker's come to town," I told it.
     "Slingshot, this is Freedom Station. Welcome back, Cap'n Rollo."
     "Jed?" I asked.
     "Who the hell'd you think it was?"
     "Anybody. Thought maybe you'd fried yourself in the solar furnace. How are things?" Jed's an old friend. Like a lot of asteroid Port Captains, he's a publican. The owner of the bar nearest the landing area generally gets the job, since there's not enough traffic to make Port Captains a fulltime deal. Jed used to be a miner in Pallas, and we'd worked together before I got out of the mining business.
     Slingshot is built up out of a number of compartments. We add to the ship as we have to—and when we can afford it. I left Jan to finish shutting down.

     The entryway is a big compartment. It's filled with nearly everything you can think of: dresses, art objects, gadgets and gizmos, spare parts for air bottles, sewing machines, and anything else Janet or I think we can sell in the way-stops we make with Slingshot. Janet calls it the "boutique," and she's been pretty clever about what she buys. It makes a profit, but like everything we do, just barely.

     "People waitin' for you in the Doghouse, Captain Rollo," Jed said. "Big meeting."
     "I'll just get my hat."

     There aren't any dogs at the Doghouse. Jed had one when he first came to Jefferson, which is why the name, but dogs don't do very well in low gravs. Like everything else in the Belt, the furniture in Jed's bar is iron and glass except for what's aluminum and titanium. The place is a big cave hollowed out of the rock. There's no outside view, and the only things to look at are the TV and the customers.
     There was a big crowd, as there always is in the Port Captain's place when a ship comes in. More business is done in bars than offices out here, which was why Janet and the kids hadn't come dirtside with me. The crowd can get rough sometimes.
     The Doghouse has a big bar running all the way across on the side opposite the entryway from the main corridor. The bar's got a suction surface to hold down anything set on it, but no stools. The rest of the big room has tables and chairs, and the tables have little clips to hold drinks and papers in place. There are also little booths around the outside perimeter for privacy. It's a typical layout. You can hold auctions in the big central area and make private deals in the booths.
     Drinks are served with covers and straws because when you put anything down fast it sloshes out the top. You can spend years learning to drink beer in low gee if you don't want to sip it through a straw or squirt it out of a bulb.
     The place was packed. Most of the customers were miners and shopkeepers, but a couple of tables were taken by company reps. I pointed out Johnny Peregrine to Dalquist. "He'll know how to find Barbara."
     Dalquist smiled that tight little accountant's smile of his and went over to Peregrine's table.
     There were a lot of others. The most important was Habib al Shamlan, the Iris Company factor. He was sitting with two hard cases, probably company cops.
     The Jefferson Corporation people didn't have a table. They were at the bar, and the space between them and the other Company reps was clear, a little island of neutral area in the crowded room.
     I'd drawn Jefferson's head honcho. Rhoda Hendrix was Chairman of the Board of the Jefferson Corporation, which made her the closest thing they had to a government. There was a big ugly guy with her. Joe Hornbinder had been around since Blackjack Dan's time. He still dug away at the rocks, hoping to get rich. Most people called him Horny for more than one reason.
     It looked like this might be a good day. Everyone stared at us when we came in, but they didn't pay much attention to Dalquist. He was obviously a feather merchant, somebody they might have some fun with later on, and I'd have to watch out for him then, but right now we had important business.
     Dalquist talked to Johnny Peregrine for a minute and they seemed to agree on something because Johnny nodded and sent one of his troops out. Dalquist went over into a corner and ordered a drink.

     There's a protocol to doing business out here. I had a table all to myself, off to one side of the clear area in the middle, and Jed's boy brought me a big mug of beer with a hinged cap. When I'd had a good slug I took messages out of my pouch and scaled them out to people. Somebody bought me another drink, and there was a general gossip about what was happening around the Belt.
     Al Shamlan was impatient. After a half hour, which is really rushing things for an Arab, he called across, his voice very casual, "And what have you brought us, Captain Kephart?"
     I took copies of my manifest out of my pouch and passed them around. Everyone began reading, but Johnny Peregrine gave a big grin at the first item.
     "Beef!" Peregrine looked happy. He had five hundred workers to feed.
     "Nine tons," I agreed.
     "Ten francs," Johnny said. "I'll take the whole lot."
     "Fifteen," al Shamlan said.
     I took a big glug of beer and relaxed. Jan and I'd taken a chance and won. Suppose somebody had flung a shipment of beef into transfer orbit a couple of years ago? A hundred tons could be arriving any minute, and mine wouldn't be worth anything.
     Janet and I can keep track of scheduled ships, and we know pretty well where most of the tramps like us are going, but there's no way to be sure about goods in the pipeline. You can go broke in this racket.
     There was more bidding, with some of the storekeepers getting in the act. I stood to make a good profit, but only the big corporations were bidding on the whole lot. The Jefferson Corporation people hadn't said a word. I'd heard things weren't going too well for them, but this made it certain. If miners have any money, they'll buy beef. Beef tastes like cow. The stuff you can make from algae is nutritious, but at best it's not appetizing, and Jefferson doesn't even have the plant to make textured vegetable proteins—not that TVP is any substitute for the real thing.
     Eventually the price got up to where only Iris and Westinghouse were interested in the whole lot, and I broke the cargo up, seven tons to the big boys and the rest in small lots. I didn't forget to save out a couple hundred kilos for Jed, and I donated half a ton for the Jefferson city hall people to throw a feed with. The rest went for about thirty francs a kilo.
     That would just about pay for the deuterium I burned up coming to Jefferson. There was some other stuff, lightweight items they don't make outside the big rocks like Pallas, and that was all pure profit. I felt pretty good when the auction ended. It was only the preliminaries, of course, and the main event was what would let me make a couple of payments to Barclay's on Slinger's mortgage, but it's a good feeling to know you can't lose money no matter what happens.
     There was another round of drinks. Rockrats came over to my table to ask about friends I might have run into. Some of the storekeepers were making new deals, trading around things they'd bought from me.

From TINKER by Jerry Pournelle (1975)

      For almost three days the Rolling Stone coasted slowly through Rock City. To the naked eye looking out a port or even to a person standing outside on the hull Rock City looked like any other stretch of space—empty, with a backdrop of stars. A sharp-eyed person who knew the constellations well would have noticed far too many planets distorting the classic configurations, planets which did not limit their wanderings to the Zodiac. Still sharper attention would have spotted motion on the part of these "planets," causing them to open out and draw aft from the direction the Stone was heading.
     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.
     In close company with City Hall was a stubby cylinder; it was either smaller than the spherical ship or farther away. Near it was an irregular mass impossible to make out; the sunlight on it was bright enough but the unfilled black shadows gave no clear clues. All around them were other ships or shapes close enough to be distinguished from the stars; Pollux estimated that there must be two dozen within as many miles. While he watched a scooter left a ship a mile or more away and headed toward City Hall.
     Whitsitt had gone inside but he had recycled the lock and left it open for them. They went on in, to be met there by the Honorable Jonathan Fries, Mayor of Rock City (aka "One-Price", proprietor of the City Hall store). He was a small, bald, pot-bellied man with a sharp, merry look in his eye and a stylus tucked back of his ear. He shook hands with Roger Stone enthusiastically. "Welcome, welcome! We're honored to have you with us, Mister Mayor. I ought to have a key to the city, or some such, for you. Dancing girls and brass bands."
     Roger shook his head. "I'm an ex-mayor and a private traveler. Never mind the brass bands."

     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—then remembered with regret that they had precious little left to sell; the flat cats, before they were placed in freeze, had eaten so much that the family had been delving into their trade goods, from caviar to Chicago sausage. He whispered to Castor, "I had no idea the competition would be so stiff."
     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. It had dawned on them that here in Rock City was a potential, unexploited market for flat cats (fuzzy Martian pets that were the inspiration for Tribbles). 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 (their father) 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 (like tribbles if you feed them too much the blasted things are born pregnant). 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 neighborly 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 rebroadcast 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, neighbors! Here we are again with two hours of fun and music—and a few tips on bargains. But first, our theme—the war-r-rm 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!"
     Sometimes they would do interviews:
Castor: "A few words with one of our leading citizens, Rocks-in-his-head Rudolf. Mr. Rudolf, all Rock City is waiting to hear from you. Tell me, do you like it out here?"
Pollux: "Naw!"
Castor: "But you're making lots of money, Mr. Rudolf?"
Pollux: "Naw!"
Castor: "At least you bring in enough high grade to eat well?"
Pollux: "Naw!"
Castor: "No? Tell me, why did you come out here in the first place?"
Pollux: "Bub, was you ever married?"
     Sound effect of blow with blunt instrument, groan, and the unmistakable cycling of an air lock—Castor: "Sorry, folks. My assistant has just spaced Mr. Rudolf. To the purchaser of the flat cat we had been saving for Mr. Rudolf we will give away—absolutely free!—a beautiful pin-up picture printed in gorgeous living colors on fireproof paper. I hate to tell you what these pictures ordinarily sell for on Ceres; it hurts me to say how little we are letting them go for now, until our limited stock is exhausted. To the very first customer who comes in that door wanting to purchase a flat cat we will—Lock that door! Lock that door! All right, all right—all three of you will receive pin-up pictures; we don't want anyone fighting here. But you'll have to wait until we finish this broadcast. Sorry, neighbors—a slight interruption but we settled it without bloodshed. But I find myself in a dilemma. I made you a promise and I did not know what would happen, but the truth is, too many customers were already here, pounding on the door of Flat Cat Alley. But to make good our promise I am enlarging it: not to the first customer, not to the second, nor to the third—but to the next twenty persons purchasing flat cats will go, absolutely free, one of these gorgeous pictures. Bring no money—we accept high grade or core material at the standard rates ."

(ed note: high grade is high-grade asteroid ore. Core material, well, this novel was written back in those days of yore when some astronomers still thought that the asteroid belt was from a planet that exploded. So "core material" is fragments of the exploded planet's core, which asteroid miners search for as a valuable MacGuffinite.)

     Sometimes they varied it by having (their sister) Meade sing. She was not of concert standards, but she had a warm, intimate contralto. After hearing her, a man possessing not even a flat cat felt lonely indeed. She pulled even better than the slick professional recordings; the twins found it necessary to cut her in for a percentage.

     But in the main they depended on the flat cats themselves. The boomers from Mars, almost to a man, bought flat cats as soon as they heard that they were available, and each became an unpaid traveling salesman for the enterprise.
     Hardrock men from Luna, or directly from Earth, who had never seen a flat cat, now had opportunities to see them, pet them, listen to their hypnotic purr—and were lost. The little things not only stirred to aching suppressed loneliness, but, having stimulated it, gave it an outlet.
     Castor would hold Fuzzy Britches to the mike and coo, "Here is a little darling—Molly Malone. Sing for the boys, honey pet." While he stroked Fuzzy Britches Pollux would step up the power. "No, we can't let Molly go—she's a member of the family. But here is Bright Eyes. We'd like to keep Bright Eyes, too, but we mustn't be selfish. Say hello to the folks, Bright Eyes." Again he would stroke Fuzzy Britches. "Mr. P., now hand me Velvet."

     The stock of flat cats in deep freeze steadily melted. Their stock of high grade grew.

     They had reached the last few at the back of the hold and were thinking about going out of business when a tired-looking, grey-haired man showed up after their broadcast. There were several other customers; he hung back and let the twins sell flat cats to the others. He had with him a girl child, little older than Lowell (age 4). Castor had not seen him before but he guessed that he might be Mr. Erska; bachelors far outnumbered families in the node and families with children were very rare. The Erskas picked up a precarious living down orbit and north; they were seldom seen at City Hall. Mr. Erska spoke Basic with some difficulty; Mrs. Erska spoke it not at all. The family used some one of the little lingos—Icelandic, it might have been.
     When the other customers had left the Stone Castor put on his professional grin and introduced himself. Yes, it was Mr. Erska. "And what can I do for you today, sir? A flat cat?"
     "I'm afraid not."
     "How about a projector? With a dozen tapes thrown in? Just the thing for a family evening."
     Mr. Erska seemed nervous. "Uh, very nice, I'm sure. No." He tugged at the little girl's hand. "We better go now, babykin."
     "Don't rush off. My baby brother is around somewhere—or was. He'd like to meet your kid. Maybe he's wandered over into the store. I'll look for him."
     "We better go."
     "What's the rush? He can't be far."
     Mr. Erska swallowed in embarrassment. "My little girl. She heard your program and she wanted to see a flat cat. Now she's seen one, so we go."
     "Oh." Castor brought himself face to face with the child. "Would you like to hold one, honey?" She did not answer, but nodded solemnly. "Mr. P., bring up the Duchess."

     "Right, Mr. C." Pollux went aft and fetched the Duchess—the first flat cat that came to hand, of course. He came back, warming it against his belly to revive it quickly.
     Castor took it and massaged it until it flattened out and opened its eyes. "Here, honeybunch. Don't be afraid."
     Still silent, the child took it, cuddled it. The small furry bundle sighed and began to purr. Castor turned to her father. "Don't you want to get it for her?"
     The man turned red. "No, no!"
     "Why not? They're no trouble. She'll love it. So will you."
     "No!" He reached out and tried to take the flat cat from his daughter, speaking to her in another language.
     She clung to it, replying in what was clearly the negative.

     Castor looked at them thoughtfully. "You would like to buy it for her, wouldn't you?"
     The man looked away. "I can't buy it."
     "But you want to." Castor glanced at Pollux. "Do you know what you are, Mr. Erska. You are the five hundredth customer of Flat Cat Alley."
     "Didn't you hear our grand offer? You must have missed some of our programs. The five hundredth flat cat is absolutely free."
     The little girl looked puzzled but clung to the flat cat. Her father looked doubtful. "You're fooling?"
     Castor laughed. "Ask Mr. P."
     Pollux nodded solemnly. "The bare truth, Mr. Erska. It's a celebration of a successful season. One flat cat, absolutely free with the compliments of the management. And with it goes either one pin-up, or two candy bars—your choice."

     Mr. Erska seemed only half convinced, but they left with the child clinging to "Duchess" and the candy bars. When the door was closed behind them Castor said fretfully, "You didn't need to chuck in the candy bars. They were the last; I didn't mean us to sell them."
     "Well, we didn't sell them; we gave 'em away."
     Castor grinned and shrugged. "Okay, I hope they don't make her sick. What was her name?"
     "I didn't get it."
     "No matter. Or Mrs. Fries will know." He turned around, saw (their grandmother) Hazel behind them in the hatch. "What are you grinning about?"
     "Nothing, nothing. I just enjoy seeing a couple of cold-cash businessmen at work."
     "Money isn't everything!"
     "Besides," added Pollux, "it's good advertising."
     "Advertising? With your stock practically gone?" She snickered. "There wasn't any 'grand offer'—and I'll give you six to one it wasn't your five hundredth sale."
     Castor looked embarrassed. "Aw, she wanted it! What would you have done?"
     Hazel moved up to them, put an arm around the neck of each. "My boys! I'm beginning to think you may grow up yet. In thirty, forty, fifty more years you may be ready to join the human race."
     "Aw, lay off it!"

From THE ROLLING STONES by Robert Heinlein (1952)

When you think of a peddler or a traveling salesman in the frontier days, what do you picture in your mind?

Again I have to blame Hollywood for the image that comes into my head. A wagon with pots and pans rattling as he comes around the corner into the yard. Hanging from the wagon is an assortment of shiny new tin hollowware; more tin-ware hangs from the wagon walls, which also contains dusters, brooms, and other household items. The wagon has racks, drawers, and cabinets filled with all sort of trinkets and small household items.

And this was probably the way it was, but not until later. The first peddlers didn’t have the luxery of a road to travel on, so they traveled from farm to farm with their trunks strapped on their backs or, as roads improved, on the back of a pack-horse or in a cart or wagon.

Trunk peddlers sold smaller items like combs, pins, cheap jewelry, knives and woodenware, knitted goods, and books.

Most were willing to barter their wares in exchange for farm products from their cash-strapped and isolated rural customers (many early Indian fur traders were in this sense little more than peddlers), then carry those goods for resale at a cash profit in country stores and town markets.

In early 1884 several traveling salesmen walked across the Ozarks Mountains bringing goods, referred to as “notions,” to sell on their trip. They bought the goods with money they earned selling fish they caught in the White River in Arkansas.

Notions are things like needles and thread, knives and buttons. Such small, useful items were scarce on the frontier. They were also easy for a peddler to carry.

The men made good money selling notions. In just a half a day in Willow Springs, the men sold $4.65 worth of goods, which was a lot of money in those days. They had problems selling their wares in some towns, however. Local merchants sometimes didn’t like strange travelers taking business away from their stores. In Thayer, the sheriff even took the full pack of goods one of the peddlers was carrying because he didn’t have a merchant’s license.

From PEDDLERS IN THE WILD WEST by jchulsey (2015)

The sea and the deep broad bays and rivers sweeping far into the continent ottered the early American colonists their easiest and cheapest highroad for commerce and communications. There were literally tens of thousands of miles of shore line which could be reached handily by boat, yet because of some perverse streak in man’s nature it wasn’t long before a number of restless people packed their scanty possessions and struck out for the heavily wooded, hilly interior.

As these deflectors from the tidewater areas moved inward, cleared their land and established outposts of colonial civilization, they presented a challenging opportunity to other men whose minds were occupied with trade and commerce. Each farm, each gristmill, each nucleus of some future village had its constant need for a supply of worldly goods and its surplus of produce to offer to the seaboard. It was a market that couldn’t be ignored—and it wasn’t for very long. Thus it came about that a band of stout-legged men hoisted trunkloads of merchandise on their backs and trudged off into the pathless forests to trade with the people who had moved inland.

These were the peddlers. For the next two centuries they were to follow doggedly in the shadows of farwandering Americans as they raited down the Ohio and the Mississippi, trekked along the Wilderness Road and the Santa Fe Trail, and ultimately moved in on the Spaniards on the far side of the Rockies in California.

Considering the number of easier and more sedate ways there were to earn a living, one wonders why men chose to become peddlers. In almost every respect it was a dog’s life, knocking around the raw back country of America. When the peddlers went out on the road, they were quite literally on the road—afoot, sloshing through mud ankle-deep in winter, or scuffing up a cloud of dust in summer. They were snapped at by vicious dogs, shot at by Indians, nipped by frost, and pounced upon by hijackers. Many were stung by rattle-snakes, and all of them were feasted upon by fleas, gnats, mosquitoes, bedbugs, leeches, and other flying and crawling species of tormentors.

But despite all of these occupational hazards, there were many overriding reasons why so many men chose such a precarious profession. Adventure was one of them, and from all accounts they encountered enough of that. A chance to get about and travel was another; early Americans had a consuming curiosity about the make-up of their country, and for a man with a restless foot, peddling gave it plenty ol exercise.

But the main reason for “going peddling” was opportunity. Peddling required no experience and very little capital. A peddler could quickly enough learn his trade as he made his rounds, and for as little as twenty or thirty dollars in cash he could buy enough stock to set himself up in business. The market for the peddlers’ goods was rapidly expanding; many peddlers accumulated enough money alter several years to retire from traveling and settle down at home as merchants and traders.

Thousands of others spotted remote villages which they figured would some day become bustling centers of trade and transportation. To these places with a future the peddlers returned and sank their roots. Some opened stores and became prosperous merchants. Others became jobbers and wholesalers. In hundreds of American cities and towns—Albany, Buffalo, Cincinnati, Fargo, Albuquerque, Sacramento—firms begun long ago by peddlers are still in business.

The first of the Yankee peddlers carried a general line of housewares and notions. Pots and pans, axes, handmade nails, thread, buttons, scissors, and combs were fastest-selling items. Biggest profits were earned on such frivolities as bits of lace and ribbon and fancy cloth, mirrors, toilet waters, spices, tea, coffee, and nostrums.

There were limits, naturally, as to how much of a load of these things a man could carry or how much he could manage to stow upon his horse. Such weight and space limitations led some of the peddlers to become specialists in certain lines. Instead of loading up with a hodgepodge of general merchandise, the specialists handled spices only, or tinware, or herbs and medicines. In later years there were clock peddlers, furniture peddlers, sewing machine peddlers. There were even peddlers of wagons and carriages—men who hitched together a string of three or four vehicles and drove around until they found buyers for the new rigs.

There was no end to the peddlers’ ingenuity in finding customers. They tracked down the remotest farmhouse and loneliest cabin, and turned up at every fair or carnival. In the Deep South they paddled up and down the rivers and bayous in canoes and drew their customers from plantation mansions and shanties by blowing on a bugle or a conch shell. But mostly the peddlers walked, pacing oil the long lonely miles with their heavy loads on their backs and the dream of riches and the future easing their way.

The peddler’s trunk was a long, rather narrow box usually made of tin. A strong peddler starting out on a selling expedition carried two such trunks, one on each shoulder. The stowing of merchandise in these trunks was a major undertaking requiring great skill. Dishes and pans of varying size were nested. Into pots went buttons, pins, nails, and ribbons. Gingham and bright calicoes were wrapped around long-handled forks.

So packed, each trunk weighed up to fifty or sixty pounds. And. paradoxically, the more a peddler sold the heavier became his trunks, for, often as not, the buyers had only grain, honey, furs, and homemade woodenware to exehange for the peddler’s wares. These products, which often weighed more than those the peddler had sold, had to be carried back to his home base and sold to the merchants and wholesalers. How successfully the peddlers traded all these country wares determined their ultimate profits.

There were compensations, however. Wherever the peddler called he was a welcome visitor. Housewives stopped their work, men came in from the fields, children gathered around, and the trunks were opened. There was no great hurry. Everybody wanted to see all the fascinating goods and hear even scrap of the latest news. And the peddler was in no hurry either, for he welcomed a chance to rest his road-weary legs, besides, if it was morning when the peddler arrived, he could usually drag out negotiations long enough to be asked to stay for the noonday meal, and if he arrived in the afternoon, there was a good chance of an imitation to stay over for supper and the night.

As roads improved some peddlers rode on horsehack, carrying their wares strapped to their horses. Others used wagons which were capable of carrying fair-sized loads. These improvements in transportation increased the importance of the peddler in our early commerce; he was able to go farther, carry more stock and take a greater volume of goods in trade or barter.

But the peddlers still had their troubles, as is attested to by the following letter written by a peddler of bonnets (paper hats called Navarinos) to his supplier in western Massachusetts:

Tioga June 22nd 1830 NYK

Mr. Thomas Hurlbut Sir.

From Bainbridge I armed here today at 12 o’clock by driving 12 miles yesterday in the rain. In consequence of the heavy rains that have fallen in this country the past ten days the roads are tremendous bad they are so rutted that I have been obliged to fasten a roap to the top of my box and hold on. I have just met with a Dry Goods pedler who trades through all pans of Pennsylvania, he says the roads are much worse than they are here however I am not discouraged yet. My horses stand it well except they are galled a little by driveing yesterday and today in the rain & for Bonets I have founed no chance for any sales of consequence yet.

The Small Pox is spreading over this country, don’t send out another Pedler with so high a box. In haste yours

Rodney Hill

I am in good health.

By early March the farm families in New England were on the lookout for the man with the packs on his back. Long before his arrival they had carefully listed the wares they must have—a dozen buttons, a paper of pins (very expensive in those days), a new jackknife, two pewter mugs, six needles—and as an appendage to that list, of essentials there was a much longer list of the things they would like to have.

The meeting between the farm family and the peddler was a lively swapping session, with the peddler in much the stronger position to get the better of every transaction. First of all, the peddler was working in what was pretty much of a seller’s market. His offering included items which the family could not do without. Then, too, he was selling to people who understandably were eager to add the slightest luxuries to their meager possessions. People possessing so little as did the early colonists found it difficult to resist a jew’sharp for the children, a stick of candy, a bit of gay ribbon or of lace, or a pretty piece of chinaware to set on the bare mantel over the kitchen fireplace. Sales resistance was low—even among the most frugal people—and the country people were uninformed about goods and prices.

If a peddler held out for a 600 per cent markup for pepper, he would blandly explain that the price was high due to an obscure war at sea which had shut off imports from the Spice Islands. So, too. would he justify his exorbitant prices for other articles by fixing the blame somehow on the English king or the avarice of the merchants in Boston, New York, or Philadelphia. His customers were in no position to dispute the pedler’s laments about the skyrocketing prices in the market places, and they paid through the nose for the goods they bought.

But when it came their turn to offer goods to the peddler in payment, the farm families invariably found that the market for such things as they had for sale was poor indeed. Honey was a drug on the market, according to the peddler; the merchants in town were not much interested that year in coonskins and beaver pelts or beautifully hand-carved chairs. If the peddler was to be believed, he could resell such items at verv depressed prices, hardly more than it would cost him to transport the stuff back to town.

Very often a peddler who marked up an item by 1,000 per cent knew that this was unrealistic. He started high so that he could magnanimously come down to, say, about 500 per cent profit—a process of repricing which was an exhilarating experience both for the peddler and his customer. One of the most enduring myths in our colonial folklore is that the peddlers were guilty of foisting wooden nutmegs and sanded sugar upon unsuspecting housewives. There has never been any evidence uncovered to back up these tales of deliberate dishonesty, but there is evidence aplenty that the peddlers were masters of the art of deception and overpricing.

Unquestionably, a minority of the peddlers were first-class bums and crooks. Their drunken brawls, bloody fights and shady deals were well publicized, and drew sharp blasts from newspaper editors. Many inns and taverns posted notices bluntly announcing that peddlers were unwelcome.

The spellbinders who peddled a nauseous brew of raw alcohol, roots, herbs, and branch water as a cure-all for every ailment from ague to housemaid’s knee did their profession a disservice. And there are, in fact, no really new stories about the traveling man and the farmer’s daughter, for the same ribald stories told today were in currency soon after the first peddlers passed along the country lanes in staid old New England. In the South the peddlers were referred to as “those damn Yankees from Connecticut,” and throughout the land they were scorned by pious folks as ungodly ne’er-do-wells only a cut or two better than g*psies.

But for all the unsavory publicity generated by the few bad eggs among them, the peddlers served a useful purpose. Importers and small manufacturers depended upon them as an outlet for a large portion of their goods. Several million people relied on these wandering merchants to bring them the goods they needed, and to carry away the things they had produced. This army of walkers was a primitive and inefficient way of carrying on trade, but when the peddler’s trunks were opened up, and he began his persuasive sales pitch, one historian remarked that “wants dawned on the minds of the household that they had never known before.”

The peddler’s salesmanship and physical endurance kept alive the first stirrings of our industrial economy. He has gone now, but for two hundred years he was an important man among men engaged in important affairs.

From PACK-ROAD TO YESTERDAY by Penrose Scull (1956)

Another vanished knight of the road is the old-fashioned peddler whose home and shop was his wagon. He both bought and sold as he went, often selling his stock, wagon and all. Starting anew, with a few wares on his back, he invariable returned with a new horse and wagon and a tidy profit besides.

"Peddler" and "drummer" are typically American words. The ancient Scotch "peder" or foot-salesman became the "pedlar" of the New World. Although in England "peddlers" traveled only by foot and "hawkers" went only by wagon, anone who sold wares from door to door in America became commonly known of peddlers.

The drummer, or man who went about "drumming up trade," actually stemmed from the earliest time when drums were used to attract public attention, just as when church was called a drum, and public announcements were made after a drum call. The first American peddlers often carried a drum known as a "chapman's" drum."

The Yankee peddler was known to the townspeople of his time as a "chapman," a word which comes from the Anglo-Saxon "ceap" for trade, plus "man" hence a "cheap-man." The chapman who later won fame as a Yankee peddler often carried a drum and an America flag and boasted loudly that he sold only American goods. Actually, it was illegal for him to do otherwise, but he was a good salesman.

The Yankee peddler was the original American who could "sell anyone anything." One of his claims to fame is the origination of the name "Nutmeg State" for Connecticut, this derived from the belief that the Connecticut peddler sold wooden nutmeg as real ones. Few people, however, know that nutmegs were famous in Connecticut on their own merits. The nutmeg was the most popular flavoring of the old days; it was even favored as a gift.

Nutmegs were gilded and ribboned and given as presents, not only because of their worth, but because they were supposed to have great medicinal value. Some of the silver trinkets of colonial days which many people believed were snuff boxes were actually nutmeg-holders. The inside of the cover was often pierced to form a grater and served also as an opening to let the aroma escape. The bon vivants and fashionable dames of the period carried nutmegs with them as a sign of luxury. Because nutmegs were valuable and because they were easy to carry, it was always a convenient money-maker for the traveling peddler, who was often call a "nutmeg man."

From AMERICAN YESTERDAY by Eric Sloane (1956)

Farmers did business in small rural towns. Before the Sears catalog, farmers typically bought supplies (often at high prices and on credit) from local general stores with narrow selections of goods. Prices were negotiated, and depended on the storekeeper's estimate of a customer's creditworthiness. Sears took advantage of this by publishing catalogs offering customers a wider selection of products at clearly stated prices. The business grew quickly. The first Sears catalog was published in 1888.

...By 1894, the Sears catalog had grown to 322 pages, featuring sewing machines, bicycles, sporting goods, automobiles and a host of other new items. By 1896, dolls, stoves and groceries had been added to the catalog.

... Rosenwald brought to the mail order firm a rational management philosophy and diversified product lines: dry goods, consumer durables, drugs, hardware, furniture, and nearly anything else a farm household could desire.

...In 1906, Sears opened its catalog plant and the Sears Merchandise Building Tower in Chicago. Also, by that time, the Sears catalog had become known in the industry as "the Consumers' Bible". In 1933, Sears issued the first of its famous Christmas catalogs known as the "Sears Wishbook", a catalog featuring toys and gifts, separate from the annual Christmas Catalog. The catalog also entered the language, particularly of rural dwellers, as a euphemism for toilet paper. From 1908 to 1940, the catalog even included ready-to-assemble kit houses.

Novelists and story writers often portrayed the importance of the catalog in the emotional lives of rural folk. For children and their parents, the catalog was a "wish book" that was eagerly flipped through. It was not a question of purchasing but of dreaming; they made up stories about the lives of the models on the pages. The catalog was a means of entertainment, though much of its magic wore off with the passing of childhood.

(ed note: now, in your mind, replace "rural" with "asteroid belt")

From the Wikipedia entry for Sears

Looking today at another article talking about the difficulties of infrastructure for space colonization with comparisons to the colonization of the West, I think there is one element in the latter that has been overlooked so far.

The Sears catalog. Kit homes included, and lengthy lead times on delivery also included.

Yes, I am picturing the future equivalent of Sears, Roebuck, & Co. having a big warehouse near Luna with giant mass driver attached, ready to lob e-catalog products at customers all over the System on demand.

For science! profit!

Also, IKEA inflatable habitats. Hopefully those two screws and the brackety-widgety-thing you had left over didn't do anything too important...

(ed note: and if your primary habitat O2 tank springs a leak, Sears Robot & Co will be happy to send a high-priority high-delta V shipment to save your life. After you use interplanetary internet public key encryption protocols to cybernetically sign in your own blood a mortgage on your soul.)


Tinker or tinkerer is an archaic term for an itinerant tinsmith who mends household utensils.


The word is attested from the 13th century as "tyckner" or "tinkler" a term used in medieval Scotland and England for a metal worker. Some travelling groups and Romani people adopted this lifestyle and the name was particularly associated with indigenous Scottish Highland Travellers and Irish Travellers. However, this usage is disputed and considered offensive by some (as is the term "gypsy"). Tinkering is therefore the process of adapting, meddling or adjusting something in the course of making repairs or improvements, a process also known as bricolage.

The term "tinker", in British English, may refer to a mischievous child. Some modern-day nomads with a Scottish, Irish or English influence call themselves "techno-tinkers" or "technog*psies" and are found to possess a revival of sorts of the romantic view of the tinker's lifestyle. The family name "Tinker" is of Anglo-Saxon origin and does not have a Scottish, Irish, or Romany connection.

Tinker's dam

A tinker's dam is a temporary patch to repair a hole in a metal vessel such as a pot or a pan. It was used by tinkers and was usually made of mud or clay, or sometimes other materials at hand, such as wet paper. The material was built up around the outside of the hole, so as to plug it. Molten solder was then poured on the inside of the hole. The solder cooled and solidified against the dam and bonded with the metal wall. The dam was then brushed away. The remaining solder was then rasped and smoothed down by the tinker.

In the Practical Dictionary of Mechanics of 1877, Edward Knight gives this definition: "Tinker's-dam: a wall of dough raised around a place which a plumber desires to flood with a coat of solder. The material can be but once used; being consequently thrown away as worthless".

Tinker's curse

The common use of "tinker's dam" may have influenced the English phrase tinker's curse, which expresses contempt. The phrases tinker's damn and tinker's curse may also be applied to something considered insignificant. A common expression may be the examples: "I don't give a tinker's curse what the Vicar thinks", sometimes shortened to, "I don't give a tinker's about the Vicar." In this context, the speaker is expressing contempt for the clergyman and his opinion. A tinker's curse or cuss was considered of little significance because tinkers (who worked with their hands near hot metal) were reputed to swear (curse) habitually.

From the Wikipedia entry for TINKER

(ed note: Note that the term "Gypsy" is considered offensive by some)

Technogypsie (also Techno-G*psie or Techno G*psy) is a term for a modern-day nomadic person who balances the arts and sciences in their lifestyle. According to Technog*psie artist Leaf McGowan, one of the Chief Executive Officers (CEOs) of, the term was created by anthropologist Thomas Baurley in the early 1980s during his ethnographic studies of modern-day nomadic peoples, especially those traveling with a "technology" job and "artistic" skill. Many of his case studies were attendees of the International Rainbow Gatherings, Burning Man festivals or sub-cultural events.

This was a term also used by Leaf McGowan to describe his lifestyle beginning in 1986 to which he claimed he coined the term then, even though the use by Baurley seems to date earlier and other uses of the term are widespread by many other authors. The original author is not certain, as it is an easy term to concoct by adding together the descriptor of "techno" from "technology" to noun or slang "G*psy" or "G*psie". According to the web site, a "Technog*psie" or "Techno G*psy" is a "wanderer and/or traveler who is inclined towards a nomadic, unconventional way of life yet embraces equally the technological as well as artisan fields and lifestyles merged together with skillsets of a Jack (or Jane) of all trades." A "Techno Tinker, Techno G*psy, or Techno Nomad".

Many individuals around the world use this title or definition to describe their wanderlust traveling lifestyle, arts, sciences, and trades. Of the many individuals who use these titles, they often have a balance between an artistic lifestyle with one that is technology driven – such as a web designer or programmer who telecommutes and travels also doing art, music, crafts, or pursuing passions that the romantic g*psies of old were known to do such as making baskets, reading tarot cards or palms, playing music, or crafting didgeridoos. Other "Techno-G*psies" are sound engineers traveling to various music events like Burning Man and creating a nightclub out of tents and art in the middle of nowhere, living bohemian in a gifting economy. Another Technog*psie might travel the world researching folklore, writing books and articles, using hospitality networks such as CouchSurfing and Airbnb, while concurrently managing websites. Many of these modern-day nomads take inspiration from the g*psies, tinkers, travelers, vagrants, and nomads of the past.

Another self-claimed "Technog*psy" who is a chemist and material scientist who defines the lifestyle as "people who basically keep the science and technology going", "often employed by large industries although sometimes working as faculty or as a small one-man business, these highly skilled scientists and engineers move about the country from technical problem to problem as the work and money moves." A network of self-identified Technog*psies, operating a website called, are a band of traveling engineers in Europe who are creating a community of support for contractors living this lifestyle. Others claiming the title of "Techno g*psy" is as a "digital nomad" or musical artisan or a network catalyzer. Techno-G*psies are a unique class, caste, and sub-cultural movement of a type of individual who blends together artistic aspirations with a knack for technologies, and are very nomadic persons possessing often very intense wanderlust addictions. The “Techno-G*psie” is more of a recent phenomenon of individuals with wanderlust, who may have simply become inspired by the lure of adventure by these fore-parents of g*psies, pirates, and tinkers; or are actually possessing the continued bloodlines of such from ancestral roots that travel with their art, writings, dance, crafts, or creativity, yet has also discovered a resonance with the equilibrium of technology, science, research, and innovation as a balanced aspiration, goal, and/or skill that drives and propels their life or meaning.

According to the authors of "Technog*psies", "There is a charm to these wanderlust ways – the freedom of the road, the woods, or the sea … beautiful scenery, new faces, friends, experiences, adventures, and things to see … the ultimate feeling of being free, yet always on the brink of survival. To live the life of a techno-g*psy, one needs to be in touch with their senses, especially that of direction; able to throw caution to the wind, yet learn when to and when not to trust others; to be able to multitask and able to possess several skill-sets that can provide sustenance and survival as well as motion. In the air of being “techno” to be in arms grasp and understanding of the world(s) we live within, and the mechanisms that make them tick. Being able to comprehend the sciences and/or the hidden knowledge, but also being in touch with the beauty and vision of what is called the “arts”. It's a balance of living between the “arts” and “sciences”. "

From the Wikipedia entry for TECHNOGYPSIE

Motorcycles were a type of two-wheeled Earth vehicle.

Motorcycles were built on Earth in the 20th and 21st centuries. They were considered a symbol of self-reliance and masculinity for many of their owners. As gasoline-powered devices became out of favor due to their harmful effects on the atmosphere, production decreased and the last gasoline powered motorcycle was built in 2035. By 2258, they were a rare collector's item.

Michael Garibaldi collected all the spare parts to build a Kawasaki Ninja motorcycle but could only find instructions in Japanese, a language of which he had no knowledge. Lennier offered to help him construct the motorcycle, as he was an expert in many languages and interested in the history of the vehicle. Through his excitement and Garibaldi being distracted, Lennier reconstructed the entire motorcycle and even fitted the machine with a non-polluting Minbari power source. Garibaldi wanted to be involved in the process and, at first, was angry, but then accepted it. The two of them went for a ride through the Zócalo.


From The Babylon Project entry MOTORCYCLE

(ed note: the description is about the movie Masters of the Universe)

Nearby, He-Man is walking with Julie to go find the Cosmic Key which she confirmed having had possession of. They run into Man-At-Arms and Teela.

As they stand there and talk, an old, pink car comes swerving haphazardly around the corner with Gwildor behind the wheel. As it would happen, he took a broken down combustion engine and made it run on “neutrinos” now, “no hydro-carbons needed.” They all pile in and he activates the thing, which goes speeding off at break-neck speed.

Snake-Oil and Scams

Now writers, if your science fiction universe contains casual FTL travel and sleepy backwater colonies, this will approximate the early days of the United States frontier. While there are venues for legitimate trade, a planet full of hicks and rubes is a tempting target for that species of trader called the Con Artist. Everything old is new again, or Plus Ça Change Plus C'Est La Même Chose.

While most of the scams are optimised for urban dwelling victims, many work well in a frontier setting.

Wild west TV shows and movies often feature the classic Medicine Show scam where mountebanks and quacks distract the crowd with entertainers while peddling their worthless miracle elixir cure-alls and snake oils. Change the labels to "alien serums" or "nanotech breakthroughs" and you are good to go.

The old "salting a mine" trick should work perfectly well on gullible asteroid miners.

Colonists facing crop failure in the face of adverse weather are ripe for the ancient Rain making scam.


(ed note: English translation: What goes around comes around)

Sure, we'd heard of that skyhoot Noah Arkwright wanted to do. Space pilots flit the jaw, even this far out the spokes. We wanted no more snatch at his notion than any other men whose brains weren't precessing. Figured the Yonder could wait another couple hundred years; got more terry incog already than we can eat, hey? But when he bunged down his canster here, he never jingled a word about it. He had a business proposition to make, he said, and would those of us who had a dinar or two to orbit be interested?

Sounded right sane, he did; though with that voice I compute he could've gotten jewelry prices for what he'd call dioxide of ekacarbon (sand). See you, nigh any planet small enough for a man to dig on has got to have its Victory Heads—Golcondas, Mesabis, Rands, if you want to go back to Old Earth—anyhow, its really rich mineral deposits. The snub always was, a planet's one gorgo of a big place. Even with sonics and spectros, you'll sniff around a new one till entropy overhauls you before you have a white dwarf chance of making the real find. But he said he had a new hypewangle that'd spot from satellite altitude. He needed capital to proceed, and they were too stuffnoggin on Earth to close him a circuit, so why not us?

Oh, we didn't arc over. Not that we saw anything kinked in his not telling us how the dreelsprail worked; out here, secrets are property. But we made him demonstrate, over on Despair. Next planet spaceward, hardly visited at all before, being as useless a little glob as ever was spunged off God's thumbnail. Dis if his meters didn't swing a cory over what developed into the biggest rhenium strike since Ignatz.

Well, you know how it is with minerals. The rich deposits have an edge over extraction methods, like from sea water, but not so much of an edge that you can count your profits from one in exponentials. Still, if we had a way to find any number of 'em, quick and cheap, in nearby systems— We stood in line to capitalize his company. And me, I was so tough and smart I rammed my way to the head of the line!

I do think, though, his way of talking did it. He could pull Jupiter from Sol with, oh, just one of his rambles through xenology or analytics or Shakespeare or history or hypertheory or anything. Happen I've still got a tape, like I notice you making now. You cogno (understand) yours stays private, for your personal journal, right? I wouldn't admit the truth about this to another human. Not to anybeing, if I wasn't an angstrom drunk. But listen, here's Noah Arkwright.

"—isn't merely that society in the large goes through its repetitions. In fact, I rather doubt the cliché that we are living in some kind of neo-Elizabethan age. There are certain analogies, no more. Now a life has cycles. Within a given context, the kinds of event that can happen to you are of a finite number. The permutations change, the elements remain the same.

"Consider today's most romantic figure, the merchant adventurer. Everyone, especially himself, thinks he leads a gorgeously variegated existence. And yet, how different can one episode be from the next? He deals with a curious planetary environment, natives whose inwardness he must try to understand, crafty rivals, women tempting or belligerent, a few classes of dangers, the eternal problems of making his enterprise pay off—what more, ever? What I would like to do is less spectacular on the surface. But it would mean a breaking of the circle: an altogether new order of experience. Were you not so obsessed with your vision of yourself as a bold pioneer, you would see what I mean."

Yah. Now I do.

We didn't see we'd been blued till we put the articles of partnership through a semantic computer. He must have used symbolic logic to write them, under all the rainbow language. The one isolated fusing thing he was legally committed to do was conduct explorations on our behalf. He could go anywhere, do anything, for any reason he liked. So of course he used our money to outfit his damned expedition! He'd found that rhenium beforehand. He didn't want to wait five years for the returns to quantum in; might not've been enough anyway. So he dozzled up that potburning machine of his and— On Earth they call that swindle the G*psy Blessing (confidence game in which the swindler promises his victims good fortune in exhange for money).

Oh, in time we got some sort of profit out of Despair, though not half what we should've dragged on so big an investment. And he tried to repay us in selfcharge if not in cash. But—the output of the whole works is—here I am, with a whole star cluster named after me, and there's not a fellow human being in the universe that I can tell why!

From PLUS ÇA CHANGE PLUS C'EST LA MÊME CHOSE by Poul Anderson (1975)

Interplanetary Internet

This section is for a telecommunications network around a planet or within a given solar system.

For an interstellar faster-than-light telecommuications network see here.

The Interplanetary Internet (based on IPN, also called InterPlaNet) is a conceived computer network in space, consisting of a set of network nodes which can communicate with each other. Communication would be greatly delayed by the great interplanetary distances, so the IPN needs a new set of protocols and technology that are tolerant to large delays and errors. While the Internet as it is known today tends to be a busy network of networks with high traffic, negligible delay and errors, and a wired backbone, the Interplanetary Internet is a store-and-forward network of internets that is often disconnected, has a wireless backbone fraught with error-prone links and delays ranging from tens of minutes to even hours, even when there is a connection.


NASA is about to make it a little easier to check your Instagram in zero gravity. Two teams, Science Mission Directorate and Human Exploration and Operations, are working together to finally make interplanetary internet a thing. Previous efforts to bring WiFi throughout the solar system haven’t always been successful, but this time, it could become reality.

It will work using something called Delay/Disruption Tolerant Networking, which is pretty similar to the internet you’re familiar with. But conventional internet doesn’t do well in space, plagued with long delays, noisy channels, and high error rates.

With DTN, even if your connection gets disrupted, it will guarantee data packet delivery once the next communication path opens. Normally, if you lose connection, the data gets dumped. But by removing the need to retransmit during a lag, it saves time and frees up the limited memory used by spacecraft.

Cosmic WiFI

Getting WiFi in space is complex, especially given typical extreme distances and fragile connection links. Even if your internet is traveling at lightspeed, it can take considerable time to send a message from Earth to Mars, for example. NASA previously proposed bringing the internet to the Red Planet in 2009, but due to budget constraints, the Mars Telecommunications Orbiter was scrapped. It would have used high-speed radio signals and laser light beams to send the equivalent of three compact disks of data each day.

DTN will now be deployed with the launch of PACE, or the Plankton, Aerosol, Cloud, ocean Ecosystem Mission, an Earth-monitoring satellite operation that will advance our understanding of climate change. The satellite, slated for launch in 2022, will surveil everything from massive storms to algal blooms to carbon cycles, teaching us more about the health of the planet’s oceans.

But testing DTN goes back to 1998, when the U.S. Defense Advanced Research Projects Agency (DARPA) began its Next Generation Internet initiative, which financed a small team at NASA’s Jet Propulsion Laboratory in Pasadena, California. Their goal was to build a “specialized deep space backbone network of long-haul wireless links” under the guidance of internet pioneer Vinton Cerf. It built upon the Space Communications Protocol Specifications developed by the late Adrian Hooke.

Since then, DTN has been used on Deep Impact, a space probe that in 2005 launched an impactor at a comet called Hartley 2, which caused an explosion equivalent to 4.8 tons of TNT. More recently, NASA tested DTN to remotely drive a Lego car in Germany from the International Space Station and to send a photo at the National Science Foundation’s McMurdo Station in Antarctica, where internet connection is spotty.

“DTN represents a shift in how data will get delivered in the future,” NASA engineer David Israel said in a statement.

DTN is just a part of NASA’s Decade of Light initiative, a growing endeavor to build an internet in the Solar System, including NASA’s Near Earth Network, Space Network and Deep Space Network. As Space Race 2.0 heats up, we’re going to need faster, more reliable ways to connect online — and technologies like DTN will be the path forward to exploring the stars.


/* Increase the timeout each time we retransmit. Note that
* we do not increase the rtt estimate. rto is initialized
* from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
* that doubling rto each time is the least we can get away with.
* In KA9Q, Karn uses this for the first few times, and then
* goes to quadratic. netBSD doubles, but only goes up to *64,
* and clamps at 1 to 64 sec afterwards. Note that 120 sec is
* defined in the protocol as the maximum possible RTT. I guess
* we'll have to use something other than TCP to talk to the
* University of Mars.

* PAWS allows us longer timeouts and large windows, so once
* implemented ftp to mars will work nicely. We will have to fix
* the 120 second clamps though!



Actually, given the great time lags in communications (and probable bandwidth issues), I would not expect interplanetary Tweets, phone calls or even emails.

Point to point communications would most likely resemble texting (including the incomprehensible abbreviations), but you would have anywhere from 1.4 seconds delay to the moon to many hours to Uranus.

This means another possible driver for high performance spacecraft would be mail delivery. (Consider a small car delivering 100 DVDs for Netflixx probably is carrying more information than you can access through your home internet connection in a day.) Contracts, magazines, movies, personal messages and anything else which needs more detail than a text message will all be loaded aboard mail servers on fast packets, and blasted to their destinations via the fastest means possible.

This of course leads to interesting scenarios where protecting and intercepting mail becomes important for intelligence agencies, business and criminals. Mail delivery will involve high levels of security and screening of the mail delivery personnel. I doubt anyone will hijack a mail packet in flight, but having a covert operative on board to hack the mail server and download the interesting information is a very real possibility.

Jim Baerg:

This sounds very implausible to me.

The light speed delays mean that all interplanetary communication will resemble emails with attachments more than phone calls.

The immense power required for torchship performance would make interplanetary communication lasers much more economical for sending even terabytes of data, much less an email greeting with a 1 MB photo.


Email in space — Should be no problem with this, even if the distances slow it down to telegraph speeds.

Text messaging in space — Will be restrained to within a few light-seconds, probably no more than 10 or so. Any longer than that and you might as well send a longer message.

Instant messaging — Will probably be restrained to 2-3 light-seconds. Like a phone call, any more delay defeats the whole purpose.

Physical packets — Documents that you don't want easily copied, high-density data storage for non-essential information (Movies, music, etc), items that can't be replicated at the destination (Due to lack of facilities), items that shouldn't be replicated at the destination (Gifts), and people (Diplomats, managers, mediators, etc).


To expand on Citizen Joe's point, would you like to receive "Male enhancement" emails with the olympusmon.mars address? How about "Dear Sir, I am the last surviving member of the Europan Resistance front and need your help to transfer $10 billion solars from the Bank of Callisto...."

On a more serious note, the high bandwidth links would probably be reserved for ship traffic, government and military communications and corporate communications (for companies with the financial clout to get in line for email). Certainly the Uranus Space Navy would not want the high bandwidth links clogged during their showdown with the Imperial Jovian Navy, nor would they want to risk malware or botnet attacks coming through those links; which suggests interplanetary comms would be tightly controlled and subscribers carefully vetted.


Since power and surface area aren't problems on the ground (and to a lesser extent, in orbit), communications would likely be predominantly TO ships while ship to shore (home base) comms would be limited to a confirmation of receipt. On Earth, we can afford to put up huge arrays to catch the smallest radio signal. Not so much in space. Likewise we can pump a lot of energy into the antenna to send back a longer message with a lot of bandwidth and strength even at stupendous ranges.

Now there are some tricks, like omnidirectional beacons and antenna that act as targets for the directional antennae. But you can only listen to data in the direction of the directional antenna. That might be limited to a single stream. Comm relays would likely have at least 4: Signal in, Signal out, Previous relay, Next Relay. By using multiple relays (at least 4 would get you around the sun) you wouldn't have black outs (except at ship orbit). And then there is the problem with the fragile gimbals needed for all the antennae.

In the end, yes, you can communicate via radio. No, it isn't broadband. No, it won't service a population comparable to the internet. It will likely be biased communication. It will still be expensive. There will be extreme needs that keep every carrier busy. So, although you COULD send a digital copy of Pluto Nash to Pluto, you would never get enough priority to use the carriers and thus it would be simpler to put it on a torch or fling it out the airlock.

Jean Remy:

What about relays at Lagrangian points?

Everyone knows where those are, and if someone needs to connect they can just link into the network. I don't even think lasers would even be needed. The relays would have high gain antennas to receive the data on broadband signals, and when a ship or colony needs to link in they can query the closest available platform with a much lower-gain antenna.

If we can be in contact with various probes (like Voyager probes) at interplanetary distances, on 1970s technology, then I hardly think you would need a giant technological leap to create a system-wide comm network.

Granted you won't have the bandwidth of fiberoptic cables, so no browsing for Earth-porn from Callisto, but I don't see communication as much of an impediment. The only real reason to use lasers (that I see) would be for private (read: military) communications that you don't want intercepted, but with a target area of 90 km in radius, it's not really very private anymore.


Surfing the interplanetary web would be a unique experience. Given the reply times measured in minutes or hours, getting a response for a search query would be more akin to making a request at the Library of Congress and then waiting for the attending librarian to go and bring you a copy of whatever they think you asked for (which may or may not be what you were actually looking for).

Since we survived the dark ages of dial-up modems, I think we could probably put up with the connection speed of the interplanetary net.


I think that interplanetary communications networks would be more like a cluster of 'webs'; one on Earth, one on Mars, one on Luna, ect. The different webs would send updates to each other on a regular schedule via dense-data/high-priority channels, and all other inquries/messages being sent via lower-priority channels. Most of your routine web activities would be with your local internet, but occationally you'd connect with another world's internet via the systen-wide web.

Jean Remy:

Interestingly enough, this is the way the "extranet" is postulated to work in the Mass Effect games. Essentially all colonies pack with them a web server full of the most needed and demanded data. If the information you are looking for is not on the server the system opens a communication link (FTL in the game) and hits the closest large colony server, and so on, until it finds the info, and it uploads it into the colony's server for easy retrieval later. In the game data storage is no longer an issue, but I assume if storage space is needed and a specific file hasn't been looked at for a while, it would be deleted.

However, since most early colonies will be science bases, I would assume large amounts of data will be passed back and forth as scientists on Callisto and on Earth look over the data, form theories and send them back and forth. It seems like a very fluid form of data exchange is needed even with local "nets". I also doubt early colonies will be very large, or widespread, and it is far more likely the Callisto colony terminals will be linked on a LAN to a single server rather than a network of servers in the first place.

Citizen Joe:

Viral propagation is another option. It doesn't guarantee speed or privacy. The idea would be that a message would be sent to any ship that is heading in the right direction that is within range. This could be a very long route. However, since there would likely be relatively few interplanetary vessels (compared to airplanes), Solar Space Traffic Controllers would have the full list of vessels and thus able to chart a route based on predicted paths. While the InterPlanetary Space ships would carry parcels, they would probably also serve as communication hubs for the viral network.


That sounds pretty close to how the modern internet functions, with data tracing geographically indirect paths as it goes from place to place. I like the efficiency of such a scheme: it would use the infrastructure that's already there to create an ad-hoc network backbone. On the other hand, you'd be trading out data security unless you've got some very good encryption (or just plain don't care who else reads your messages).

Jean Remy, I was thinking along those same lines. A lot of business/corporate/government entities would end up hosting proxies of their sites and databases on the far-flung colony servers, with periodic updates being beamed back and forth (ultra-secure data being handled differently).

With multiple proxies being hosted for a single database, with data exchange rates measured in minutes, how long do you think the system will last until Murphy's Law takes a server down through version conflicts?

Jean Remy:

Viral dissemination works on Earth because of thousands and thousands of privately owned servers.

However, even in the best-case scenario of a very developed interplanetary infrastructure, I don't see a lot of traffic in space. Say two cyclers between every major colonial epicenters (say 2 for Mars, 2 for the Jovian colonies, 2 for Saturn etc...) and a few "moon hopper" shuttles, but those would be so close to their giant primaries getting a Line of Sight on them would be an issue.

However the Comm relay platforms suggested are basically Voyager probes without the scientific instrumentation and a known stable orbit. Rather that throwing your message out omnidirectionally and hope that eventually it will reach your destination (because viral dissemination is kind of like shooting blind) you simply bounce the signal of a set number of known (and if want, secure) predetermined platforms. If your goal is to reach as many people as possible (the entire point of viral dissemination in the first place) then target the Cyclers. Chances are good the passengers en route back and forth have personal computers linked in to the ship's server, which keeps updated by linking in to the platforms.


The general outlines of communications in the plausible mid-future look a bit like the Victorian era. Fast and reliable close to home, a little slower if you want to contact the next 'city' over, slower again but still reliable if you want to contact another 'country', and best of luck to you if you want to contact someone in the backbeyond. In this case city, country, and backbeyond are defined by both linear distance and orbit.

You could even end up with a Pony Express situation. Someone sets up a Planet Express torchship delivery system to carry high information-density packages or mail that requires high-security delivery... And then nine months later someone else sets up a tightbeam relay network that can handle multiple high-bandwidth high-security messages... And suddenly you've got a lot of cheap ponies on the market.

Except in this case the ponies have 45 gW/30 milligee legs.

From On Torchships comments (2010)

This is a topic post referring to Purdue University's project Destiny.
Here is my introductory post for the series.
The subject is section 4, Interplanetary Communications Network.

 Headline results: I believe that the cost of this system can be reduced by nearly 50% without altering the underlying performance assumptions.


 This study's communications design is a major factor in overall cost. Every effort should be made to reduce this cost; the headline price is $228 billion, which works out to $4,560 per colonist per year for connectivity.

 The basic design using radio links for surface to orbit and optical links for orbit to orbit is sound. The performance numbers seem well-researched, as do the fault rates. The need for a relay is well-established. The amount of data considered is also reasonable: a single HD video stream for each 100 colonists plus two minutes of SD video (or its equivalent in other data) per person per day. My disagreement is that the use of small disposable satellites is an oldspace norm which unnecessarily drives cost.

 What's the alternative? A large multiuser platform with human maintenance missions. ITS has more than enough dV to deliver a maintenance crew and 300 Mg of cargo from Earth to ESL-5 or from Mars to areosynchrous orbit. By delivering discrete components like transponders, processors, batteries, apertures, etc., the mass of the thrust tube and propellant masses for orbital insertion and decommissioning are eliminated. Beyond that, a shared facility offers options for cost recovery. Science missions such as large telescopes may draw funding for shared services like electrical power and maintenance. Organizations like the L5 society may choose to dock habitats to the platforms for similar reasons.

Relay Node

 Consider for example the ESL-5 relay. Baseline costs for the node are $47.5 billion. The baseline plan requires 53 separate Falcon Heavy launches, 12 of which are contingency satellites. Each vehicle has dedicated avionics, GNC, optical apertures, structural bus, thrust tube, propulsion, etc., etc., all of which are discarded once any one system fails.

 For redundancy and to minimize interference, two platforms should be deployed. The physical structures are not significantly affected by exposure to deep space, so their effective service lifetime is greater than the length of the study. By allowing one ITS launch per cycle and alternating the visited platform, each platform is visited roughly every five years. Components can be tested, repaired or replaced if necessary and certified for another 5-year period. System expansion is done by adding more components than are removed.

 The baseline Falcon Heavy launch and operation costs for this location are $6.2 billion in current dollars. 47 fully-refueled ITS launches (at $46 million each, using a higher lifetime flight rate for near-Earth operation and the same $25 million operations cost) would run $2.16 billion. Total savings: $4.04 billion.

 The solar panels are a major portion of that cost, $240 million for ~360 kWe on one satellite, or $12.72 billion for the relay satellite system. The project considers SAFE-series reactors in other contexts, for example a SAFE-800 design producing 240 kWe for about $1.4 million. At steady state, six satellite equivalents will be operational at each platform; 9 SAFE-800 reactors plus one spare would therefore cost $28 million initial plus $4.3 million per refuel for the L5 relay system. Reactors are assumed to have a 60-year operational life, so two complete sets of hardware (40 total reactors) must be built and deployed during the project along with eight refueling cycles. Total cost $90.4 million, assuming launch costs are covered in the per-cycle maintenance visit cost. Total savings: $12.63 billion. Even if the development process for these reactors took several billion dollars it would be a net gain.

 The thrusters, propellant tanks, lines, valves, avionics, guidance and other systems are shared across the entire platform. Because no insertion or deorbit burns are necessary, the amount of stationkeeping propellant required is a small fraction of the baseline amount. I'll assume that mass and cost of these systems is instead spent on a structural truss for mounting components, on a stationkeeping system with ion thrusters or PITs to eliminate toxic fuels, and on a platform pointing system with very long lever arms and robust reaction wheels. No net change.

 The electronic communication components would be unchanged, and remain the primary expense at $268.8 million each ($11.02 billion total without flight spares). However, because a failure of other critical systems does not lead to loss of use of the comm systems, we are able to eliminate the 12 extra satellites and comm sets. Human servicing missions will be able to repair, repurpose or replace as needed, while one extra set on each platform will provide short-term protection against an outage. Total savings, $3.22 billion.

 This node in the communication network can be implemented as a shared facility for a savings of $19.89 billion, a total cost of $27.65 billion. The average colonist population over 100 years is half a million, so this node costs $553 per colonist per year.

 Similar logic can be applied to the Earth-orbit and Mars-orbit nodes.

Earth Node

 The Earth-orbit node would consist of three geosynchronous shared platforms. Due to the high population of GEO satellites, these could be useful places for permanent satellite servicing facilities. A rotating workforce of technicians could keep the platforms operational while also servicing other customers' hardware to offset costs. Over the life of the node, 66 satellite equivalents are required; 15 satellites are required at steady state, or 5 per platform. For simplicity these platforms should be identical to the ESL-5 platforms, though they will use one fewer reactor due to reduced power requirements. To maintain a five-year service interval, ITS flights are required every 20 months which equals 60 total flights. An alternative is to place a permanent manned maintenance facility at EML-1 and use an orbital tug to service platforms as needed; this would provide the added benefit of a one-week response time to problems.

 The baseline cost of this node is $61.1 billion with 14 flight spares. Electrical savings are ($19.2b baseline - $75.6m capital - $46.44m refueling) = $19.08 billion. Launch savings are ($9.36 billion baseline - $390 million ITS/$6.5m) = $8.97 billion. Spares savings are 14 x $189.86 million = $2.66 billion. This node's total savings are $30.71 billion, total cost is $30.39 billion.

Mars Node

 The Mars-orbit node would consist of three areosynchronous shared platforms. Due to the study's power limitations, bandwidth through each satellite is quite a bit lower than through the relay satellites and so more craft are specified. Over the life of the node, 135 satellite equivalents are required; 33 satellites are required at steady state, or 11 per platform. These would ideally be two standard platforms linked together, with 19 reactor modules. The hardware would be delivered via cargo ITS, one per cycle. This vehicle would aerocapture and then rendezvous with a central maintenance facility on Phobos (or possibly Deimos) for offloading, followed by a descent to the surface with remaining cargo and a standard return. Service missions would be dispatched from the Martian surface using one of several Mars-dedicated ITS vehicles, dock with facilities on Phobos, transit to the appropriate platform, perform maintenance and installation tasks, then return first to Phobos and then the surface. The Phobos base may eventually be permanently manned and used as a port for handling electric-propulsion cargo vehicles via docking tether.

 The baseline cost of this node is $119 billion with 21 flight spares. I believe there is a potential savings from increasing the transmission power of the Mars node to match the data rates of the other nodes, but let's stick with the baseline for now. Electrical savings are ($37.44b baseline - $159.6m capital - $98.04m refueling) = $37.18 billion. Launch savings are ($18.25 billion baseline - $1,457 million ITS/$31m) = $16.79 billion. Spares savings are 21 x $189.86 million = $3.99 billion. This node's total savings are $57.96 billion, total cost is $61.04 billion.


 These changes bring the total I-Comm network costs to $119.08 billion, or $2,382 per colonist per (Earth) year / $198.47 per (Earth) month. That's a combined savings of $108.92 billion, or 47.8%. I believe there may be another $30-$60 billion of potential savings in the actual comms components due to standardization and large production runs, and at the Mars end by adding more power through fewer apertures.

 The use of shared facilities encourages the further development of space. Permanent crewed maintenance bases near the three nodes would revolutionize the way satellites are built, launched and operated, and would open the road to asteroid mining and the colonization of free space.

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