Use of Hydrogen as a Rocket Fuel

One of the biggest problems with in-situ fuel production on the moon is the lack of hydrogen. LH2/LOX gives one of the highest Isps of chemical rockets, but it must be imported from Earth, which basically defeats its purpose.

However, there may in fact be signigficant quantities of hydrogen on the moon:

1. Clementine preliminary results offer teasing indications of ice (possibly in economically minable quantities) at south lunar pole.
2. If we mine Helium-3, we will produce plenty of H2 as a by-product. It is present, thanks to eons of solar wind buffetting, in 1 part per 10,000 (1 ton per 10,000 tons).

Apart from the above, there is the optional strategy of using a "hydrogen extender." There have been promising studies of methods of using hydrogen from Earth in combination with lunar dust to produce Silane, SiH4, a near-analog of methane, and this would give us several times more propulsion for the same amount of hydrogen imported or extracted.

There are strong reasons to extend what hydrogen we import or extract from the regolith: we will also need it for our mini-biospheres and as an industrial reagent. Burning it is really a crime in that respect.

There are alternatives to hydrogen: powdered metals. Chemically, the attraction for oxygen of iron, aluminum, magnesium, and calcium -- all abundant enough on the moon -- is sufficient to warrant development of the engines to burn such combinations. Attractively, the exhaust is not a gas that would degrade the scientifically and industrially priceless lunar vacuum, but powder, analogous to the moondust from which it was derived, that will fall back to the surface in an environmentally benign way.