
Originally Posted by
cjameshuff
Travel time is absolutely an issue. You're talking about shipping propellants to Earth to enable flights to Mars. You'd be moving Starship propellant loads with a round trip longer than Starships going to Mars and back (possibly much longer, it will take OSIRIS-REx 7 years to make its trip to Bennu and back), with openings less frequent than Starships have to Mars. Exactly how many of these tankers do you want to keep in operation to enable each Starship to make its trip? A Starship tanker operating from Earth with multiple launch/landing sites could conceivably deliver multiple payloads per day, matching the throughput of a whole fleet of NEO tankers. And of course it would launch when needed, to the orbit the propellant is needed in, as opposed to burning a good chunk of it to match orbital plane.
So you're foreseeing no changes in propulsion methods between now and when we set up lifetime human settlements on Mars? I wouldn't count on OSIRIS-REx or Starship still being relevant designs by then.
As for how many tankers, I'd say given the goals of human colonization a fleet should be established with as many vessels as possible. Mars isn't the only destination.
And volatiles, no, it doesn't "remain to be seen". NEOs get too close to the sun to still have significant ices. Your volatiles will be limited to water (no nitrogen, argon, etc), and that will be in the form of hydrates that require high temperatures to extract...
very high temperatures if you want to get all of it, similar to those used in pottery kilns. If you're mining propellant to be shipped across the solar system for use elsewhere, you're going to want to go after bigger fish.
Hot dry stone... like Mercury or the Moon. Surely no water there!
You are probably right. But the only way to find out for sure is to go and look.
It has the same problem as suggestions that we use the moon or the lunar "Gateway" as an intermediate. Craft going to or from Mars will be passing through the neighborhood at several km/s.
OK.
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