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That's true, but there is no fuel source out in space. Outside of Earth orbit, eg Lagrange points, you need fuel deliveries.

On Mars they can make methane with the Sabatier process.

So you have:

- LEO/MEO - vulnerable to asteroid impact ejecta

- GEO/moon/L-points - avoid ejecta, but need regular refueling. If Earth is toast, there goes resupply

- Mars - close enough to the sun for solar, able to conceivably bootstrap in a few centuries

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Actually there is fuel in space - water and sunlight.

You can split water into hydrogen and oxygen using electricity from sunlight.

In long term, most likely both Hydrolox and Methalox will be in use.

I think the parent comment meant to say there is no propellant in space.

There are comets in space, so there is water and water can be made into propellant.

Ceres also seems to have a lot of water: https://astronomy.com/news/2020/08/ceres-an-ocean-world-in-t...

Solar sails can get you to anywhere in the Solar system. Not very fast, but essentially free. So a swarm of drone ships with solar sails can transport an almost infinite amount of propellant to your refueling bases from mining sites.

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