once that technology becomes available and reliable, Mining useful things in outer space is at least 10 years away, plus at least another 10 to make it "reliab

once that technology becomes available and reliable, Mining useful things in outer space is at least 10 years away, plus at least another 10 to make it "reliable." And what would it accomplish? If you brought an asteroid full of volatiles into LEO, and then converted it into LOX and LH2 before the asteroid burnt off and then developed a cryogenic storage system and then used a constant supply of the fuel for station keeping, you could have a fueling station in LEO. So I guess you could launch a smaller rocket from Earth, spend fuel to rendezvous with the fuel station, fuel up, and then go to Mars. How much will that save you? A Falcon 9 launch is about $50 million. A SpaceX developed heavy-launch will probably cost $100 million or $200 million, but maybe you could get by with a Falcon 9 for about $50 million. So, you've saved $50 million to $150 million, assuming this all works perfectly, on a mission that will costs several billion, and massively increased the complexity by requiring a stop and refueling in orbit. (And I pretended that bringing the asteroid into LEO and keeping it there and mining it there and preserving the fuel there all had a cost of $0.00.) This isn't a "stepping stone." This is at best a side show, at worst a permanent delay to a manned Mars mission, because these kind of "well, once that technology becomes available and reliable, it would help, right?" issues are limitless. There is no end of the things that you could do instead because they might eventually some day if everything works right make a Mars mission a tiny margin easier. This is exactly the problem the SEI had when designing a trip to Mars. Bush said he wanted one, and so NASA put every possible thing they could on the critical path to make sure everyone's pet technology would get funded. It got a price tag of $450 billion and Congress reacted by zeroing out every single expenditure for it. Here are REAL stepping stones: 1. Build a heavy-launch vehicle. 2. Put a lab onto Mars capable of manufacturing fuel from the Martian atmosphere. 3. Develop a landing system to put a 10+ ton payload onto the surface of Mars. 4. Launch a few spacecraft with artificial gravity and after several unmanned launches put some people in them for a few days / weeks / months (doing some other mission if you want).