Space Transportation - mmmt_transportation.pdf - Moon Society

MMM #69 - October 1993
COSMOTIVE, INC. By Peter Kokh
Fuels Division
Most brainstormed Lunar Development Scenarios call for earliest possible Oxygen production. We need
oxygen to make water, for atmosphere and biosphere, and as oxidizer for rocket fuel. The intent here is a) first to
reduce the cost of return crew and cargo trips to orbit and back to Earth, and then b) to ship lunar oxygen to low Earth
orbit cryogenic refueling depots to lower the cost of further Moonbound supply and resupply shipments from Earth,
and finally c) to reduce the cost of expeditions to Mars and the asteroids.
While in water vapor, the combustion product of LOX and LH2, there is an 8:1 mix by weight, the actual mix
going in is a hydrogen enriched 6:1. So lunar oxygen cuts the cost of of 6/7th of the fuel mass. How can we do better?
An early and still often mentioned proposal is to use the hydrogen imported to the Moon to best advantage by
first combining it with local silicon to make liquid Silane SiH4 (a nominal analog of methane) and use that instead of
hydrogen as fuel. While Silane is less potent than LH2, its use promises to reduce the freight bill of sustaining the
outpost or settlement by a significant enough percentage to be worth pursuing once the demand justifies the cost of
required capital equipment. In the Silane family are other potential liquid fuels, some of which should work even
better, such as Si2H8.
Are there other potential totally indigenous lunar fuel combinations? In theory, yes! Oxygen has a high
enough affinity for Iron, Aluminum, Calcium, and Magnesium (all rather abundant in lunar soils) to make good fuel
combinations — on paper. Most discussed are Iron, which exists in handy abundance as powdered fines, and
Aluminum, which, alloyed with 25% Calcium, makes a very friable easily powdered alloy.
However, we have yet to engineer a [chemical] rocket engine that can use such fuels. It’s not a matter of
engineering difficulty so much as the fact of life that in none of NASA's scenarios is there more than token lunar
development. Thus there is not enough perceived need to justify the expense of R&D on such fuel combinations and
the motors to burn them.
Those of us interested in seeing tumble the “NASA Wall” that prevents opening the space frontier to the
general public (as opposed to token elite proxies for voyeuristic gratification) need to find and/or encourage
entrepreneurial development of such transportation modes. Even if cheap access to space (CATS) is realized in the
Delta Clipper program, the cost of shipment of goods into and out of the lunar gravity well will remain higher than it
needs to be without the development of refueling options using “all lunar” fuels.
Once all the fuel needed to refuel a rocket bound for the Moon in low Earth orbit is produced locally on the
Moon, the settlement’s net bill for shipping and freight costs for needed imports the rest of the way from LEO to the
Moon becomes moot. Not only will it be cheaper to import, but the fuel overhead cost of exporting will fall, increasing
whatever competitive advantages that might already exist.
Hold & Hull Division
As we’ve hinted, space pioneers ought not to rest content with diversification of production for export and
with maximizing market opportunities. They can improve their competitive position by paying themselves for the
freight bill of both imports and exports. Using lunar-sourced fuels at every opportunity is just one part of this effort.
Locally supplying as much as possible of the containers and vehicles used in import and export shipments will boost
savings even further on items already competitive, and may make the competitive difference for other items marginally
short of being so.
The idea of a Lunar Frontier Aerospace Industry will elicit gaffs of laughter from many. But recall the MUS/cle
paradigm for lunar industrialization that we’ve previously recommended. [MMM # 18 SEP ‘88 pp. 3-4 “Lunar Industrial
MUS/cle”, and MMM # 65 MAY ‘93 pp. 7-8 “The Fast Road to Lunar Industrial MUS/cle and the Substitution Game”]. It
is an “appropriate” lunar aerospace industry we are advocating.
Lunar industry should not concern itself with those complex, lightweight, and electronic (“cle”) components
which require a sophisticated industrial base to manufacture and which can be made on, and shipped from Earth
relatively cheaply. Instead, frontier industrialists should concentrate on the more massive, unitary, and simple (“MUS”)
components. These are items that would otherwise cost a lot to import because of their aggregate weight, but which
can easily enough be made in the settlement’s startup industrial shops.
What is needed is a glass composites industry to start off production of tanks, body panels, spars and truss
frame members, etc. Second generation industries using local iron, magnesium, titanium, and aluminum can expand
the selection of aerospace products it is possible to fabricate locally.
We are talking about:
√ fuel tanks both for depots and on ship,
√ unpressurized cargo holds
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