Solar Empire

Some thoughts of mine on space logistics from a comment:

If you want to use something like nuclear thermal or solar-thermal rockets to push cargo and eventually people around the solar system (to, say, actually set up a base on the moon/mars), then hydrogen is what you will need for propellant.

Reading the research on lunar water deposits a few years ago, I didn’t get the impression that there was a lot there. The article discussing the orbital neutron reflection scan seemed to imply something like an extremely diffuse presence in tons of sand in the permanently shadowed regions of the moon. If so, blowing it away as reaction mass might not be sustainable. You might want to keep it around for use in moon-bases.

Ceres seems to be the closest object with lots of water and a shallow gravity well. (It’s also, and for that reason, far enough out that deriving serious power from solar energy is problematic.)

I think that colonizing Mars / beginning to fling large masses around the solar system with space derived propellant, may require robotically colonizing Ceres as a first step.