Moon Miners' Manifesto

#4 April 1987

Bootstrap Rockets!

J. Alex Gimarc in his 1 Dec 1985 dated report ( to SSI ) on Space Shuttle External Tank Applications, section IV-A, discusses orbital disassembly of the ET and melting and powdering of the aluminum ( see the Wyle orbital aluminum melting facility pictured on page 11 of this [hardcopy version] newsletter ) for use as a fuel to burn with cryogenics ( LH2/LO2 ) scavenged from the ETs in a hydrogen / oxygen / aluminum based rocket engine in a 1:3:4 mix with a specific impulse ( Isp ) of over 400 seconds. Despite the high costs of engine development and the orbital melting / powdering facility, the economics of so much ET aluminum available already in orbit are such that this technology would greatly enhance the possible scope of orbital transfer operations.

But why do space enthusiasts continue to espouse and settle for developments which are NOT ON THE ROAD to ultimate goals? If all that is wanted is a token science base on the Moon and perhaps a robotics-operated mining facility / mass-driver launch system, okay; but then this hypocrisy about favoring settlement of the Inner Solar System should stop. Such an engine, discussed by A. H. Cutler ( in Aluminum Fueled Space Engines to Enhance Space Transportation System Effectiveness, Springboard to the 21st Century, NASA / ASEE Summer Study, 1984, by A. H. Cutler ) and alluded to by Gimarc will not serve as the bootstrap rocket needed by a Lunar Colony to support itself without wholesale handouts from Earth.

Getting to the Moon only counts if we do so in a manner which allows us to stay there and thrive no matter what non-supportive political-economic decisions are made on Earth. To this end only an engine which burns Lunar-sourced fuels exclusively will do. With such an engine, the Earth to Moon freight bill would reduce itself ( so far as bottom-line balance of payments are concerned ) to no more than the Earth to LEO ( low Earth orbit ) cost. The Moon could pick up cargo and settlers in LEO and transport them the rest of the way essentially free.

[The above was written more than a decade before Lunar Prospector's confirmation of substantial water-ice reserves at both lunar poles. Since that discovery, many have called for using this resource to produce liquid hydrogen and liquid oxygen rocket fuels. This would constitute a one time unrecyclable squandering of a limited resource that took hundreds of millions of years to be deposited. The "rocket jocks" who couldn't care less about lunar settlement and only want to jet set around the solar system on voyages of discovery, can scratch their itch elsewhere. The writer stands adamantly opposed to the production of rocket fuels from lunar polar ices when they are not necessary. Once we are this far out on the shoulder of Earth's gravity well, hydrogen-free fuel combinations with a lower Isp produced locally on the Moon will do quite well. -- PK.]

The aluminum rocket IS the answer, of course, but without the costly Isp enhancing hydrogen purchased from Earth sources. Burning powdered Lunar aluminum with liquid Lunar oxygen, O2 ( possibly enriched with ozone, O3 ), in a hybrid engine will not have the high Isp performance we have grown used to, but it will be superior to the CO/O2 fuel system now being favorably considered for Mars based operations.

[Other metallic fuels are worth investigating, especially iron, as powdered unoxidized iron is abundant in the surface regolith and needs only a magnet to harvest. - PK]

Whatever problems there are in development of a working Al/O2 engine pale into insignificance in comparison to the rewards. Those with the right stuff or can-do mind-set will not be discouraged by apparent "obstacles."

Meanwhile, the H2/Al/O2 rocket is but an expensive distraction that wins the battle of orbital transfer operations but loses the war of space settlement. It should be resisted.

Contents of this issue of Moon Miners' Manifesto