Fuel choices for orbital bus? | Orbital bus | Forum

We haven't given this much thought yet.  The most important design criteria to keep in mind is that the orbital bus that's attached to the lander will spend 4 or 5 months in space during its low energy transit.

This point is especially important when it comes to consideration of cryogenic storage.  If we can't keep, say, LOX oxidiser at a sufficiently low temperature, it will slowly boil off.  Over the course of 5 months (as opposed to a few days on the CM), we could lose a lot of LOX, which is obviously quite wasteful.

This isn't a problem with non-cryogenic fuels, of course, which most hypergolic fuels seem to be.  However, hypergolic fuels seem to be the nastiest, with regrads to things like corrosiveness or toxicity.  I'm a little unsure what our approach should be.

I'll try to see if I can find some liquid propellants which are non-cryogenic but otherwise not too nasty, but I'm not going to hold my breath.

Have hybrid rockets ever been used in space, instead of just on the way?