Space colonization one step at a time (Step 1)

From: sraj

> The most important issue I feel is the availability of water,
> if we are to build many space habs we should be close to a
> ready supply of water?

I've seen Mars advocates make this argument, for obvious reasons. But I tend to think of this in terms of what percentage a particular element is of the total mass needed. Now where water is concerned, we only need concern ourselves with the hydrogen, since if we're smelting ores from any source, we'll be producing more oxygen than we need. The hydrogen is only 14% of the total mass of water needed.

If you look at the mass budget of the Stanford Torus (the most thoroughly-studied design), you find that the hydrogen (and even the carbon) is a relatively small fraction of the total mass you need. The largest fraction of what we need is steel, glass, and shielding.

Now that said, do I think that in the very long term, more space habitats will be built in the Asteroid Belt than near the Earth? Yes. And will greater availability of water in the Belt than in cislunar space be an advantage for them? Also yes. But I certainly expect the process to start out close to Earth for economic reasons.

Regards,

Mike Combs