Re: Plenty of oxygen on the Moon
Satellites use hypergolics. The most common fuel combination is monomethylhydrazine fuel and textroxide oxidizer. Lunar fuel plant designs are based around hydrolox. ISRU availability of nitrogen and carbon on the Moon is limited to trace amounts. Refueling satellites using Lunar fuel will require importing both nitrogen and carbon.
We want hydrogen, not oxygen, for spacecraft shielding. If we want to go the bulk mass route and use unprocessed rocks, grabbing an asteroid requires far less Dv. The trouble with the bulk mass route is we end up using a lot of fuel to get rock to the destination. That rock isn't useful for much else without processing. If we were building dozens of ships and stations it could make sense to build a rock processing center in space. We're not building dozens of ships and stations. At this stage is HSF it makes the most sense to send water to any stations/ships we build. At least there are multiple uses for the water.
The Moon simply is not a good source of resources. To change this we either need to import carbon and nitrogen(Assuming we don't discover extractable local sources in the quantities needed). Depending on the labor force needed to operate an industrial mass-production facility(Robots are great but, for the foreseeable future, we still need the guy with the spanner.) and the supply chain it is questionable whether we would have enough hydrogen for local uses. If we are going to the Moon using tax dollars it has to be because people actually want to live on the Moon. If casino owners want to set up Lunar Vegas on their own dime that is fine with me.
I am hoping the Sabre engine will fly. I don't see what exactly Skylon has to do with a discussion about the Moon versus Mars. Skylon is a space plane to LEO. When(think positive) it is operational it should lower the cost to Earth's surface to LEO. If anything it will make it more difficult for Lunar exports to compete.
Because I don't think I've covered it, which means it will probably come up, hydrolox(H2/O2) is not suitable for use as a satellite fuel. The current goal for "long-term" hydrogen storage on orbit is seven days(ACES developmental second stage).
Biting the hand that feeds IT
