Lunar Manned Maneuvering Unit Fuel Notes

For getting around the moonbase, the question of combustible propellants vs. compressed gas depends on what we want to do. On the first flight, a compressed gas rocket pack would be visually interesting and a good technology demonstrator, saving us development costs and weight while sacrificing range and duration.

Compressed gas would be safer, too; but we still must treat it with extreme respect. A little sphere pressurized to 5000 psi like the Shuttle EMU's secondary oxygen pack has the energy of a few sticks of dynamite if it explodes; it's even more dangerous than a scuba tank.

We're really reluctant about hydrazine. It's very toxic, and even though we'd keep the backpack outside the hydrazine plume and try to minimize leakage from the tank, the hydrazine forms crystals which adhere to the beta cloth on the outside of the space suit. We'd have a problem with decontaminating the suit every time the crew comes in.

The technique for decontamination is straightforward: use ultraviolet light to see stuff (it flouresces in ultraviolet) and then brush it off. But the time lost to decontamination could be significant, and the risk of missing a spot that would be imported into the habitat is very high. It would take days for the crystals to sublimate off the suit in a vacuum.