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It's only when you realise that getting off Mars is far more like getting off Earth than getting off the Moon, that the full rationale behind SpaceX's obsession

It's only when you realise that getting off Mars is far more like getting off Earth than getting off the Moon, that the full rationale behind SpaceX's obsession with a re-usable launch vehicle rocket that can land itself, becomes apparent.

mikepurvis 11y ago
Is the assumption there that a Falcon 9 lands vertically and a Dragon (or equivalent) is the ascent vehicle? Still doesn't really address the business of manufacturing the fuel or getting it into the rocket. Nor, indeed, the matter of lifting a Dragon 60m into the air to integrate it back onto its launcher. So much Earth infrastructure we depend on for this stuff.
- jackgavigan 11y ago
  > ..lifting a Dragon 60m into the air to integrate it back onto its launcher. Why would you need to do that? Why not land the Falcon (Edit: Actually, it might be a Raptor) with the Dragon already on top of it?
  - phire 11y ago
    Raptor is the engine. Though it's unlikely anything baring the Falcon name will ever leave low earth orbit, it's just too specialised for the job of leaving earth's surface. It's not even designed to stay in LEO, they go out of the way to make sure it falls back into earth's atmosphere within a orbit or two (often less than a single orbit). You want to design a new craft from the ground up with the job ascending from mars. Ideally to save weight you want the stage's rockets to be used as many times as possible: Mars ascent, Mars Landing, Potentially orbital manoeuvres to get from LEO to mars and maybe the final part of earth ascent. But making a rocket fire that many times requires the ability to refuel, perhaps even twice (both LEO and on mars). You also have to be confidant about re-igniting the engine that many times over 5+ years.
    - greglindahl 11y ago
      I know what you meant to say by "unlikely anything baring the Falcon name will ever leave low earth orbit", but note that the Falcon 9 upper stage drops off the satellite in Geostationary Transfer Orbit (GTO) for every geosynch launch. Presumably DSCOVR's launch to L1 also involved some kind of not-low transfer orbit. And the 2nd Falcon heavy launch is planned to send the upper stage to much higher than LEO, where it will drop off a variety of small satellites, including Lightsail-B. https://en.wikipedia.org/wiki/Geostationary_transfer_orbit https://en.wikipedia.org/wiki/Geostationary_transfer_orbit
Armisael16 11y ago
Eh - I'd say that it's pretty even. It takes about twice as much delta-v to get into low martian orbit as low lunar orbit, which is still less than half what it takes to get into low earth orbit. Earth has a lot of gravity and a lot of atmosphere, which is nice for living there but a real pain in the ass when you're trying to leave.
rolandog 11y ago
I've always wondered why don't they allow the testing of those rockets in stable ground? We've done crazier tests, like nuclear testing: https://www.youtube.com/watch?v=LLCF7vPanrY https://www.youtube.com/watch?v=LLCF7vPanrY
- MrZongle2 11y ago
  I thought the reason involved the FAA requiring SpaceX's to prove that the first stage could be guided accurately to the general pad area instead of plowing into a populated region. Landing on a barge out at sea reduces the risk of the latter.
  - 001sky 11y ago
    Yep, a flyover of populated areas is avoided with an offshore lz/barge.

mikepurvis 11y ago

Is the assumption there that a Falcon 9 lands vertically and a Dragon (or equivalent) is the ascent vehicle? Still doesn't really address the business of manufacturing the fuel or getting it into the rocket. Nor, indeed, the matter of lifting a Dragon 60m into the air to integrate it back onto its launcher. So much Earth infrastructure we depend on for this stuff.

jackgavigan 11y ago
> ..lifting a Dragon 60m into the air to integrate it back onto its launcher. Why would you need to do that? Why not land the Falcon (Edit: Actually, it might be a Raptor) with the Dragon already on top of it?
- phire 11y ago
  Raptor is the engine. Though it's unlikely anything baring the Falcon name will ever leave low earth orbit, it's just too specialised for the job of leaving earth's surface. It's not even designed to stay in LEO, they go out of the way to make sure it falls back into earth's atmosphere within a orbit or two (often less than a single orbit). You want to design a new craft from the ground up with the job ascending from mars. Ideally to save weight you want the stage's rockets to be used as many times as possible: Mars ascent, Mars Landing, Potentially orbital manoeuvres to get from LEO to mars and maybe the final part of earth ascent. But making a rocket fire that many times requires the ability to refuel, perhaps even twice (both LEO and on mars). You also have to be confidant about re-igniting the engine that many times over 5+ years.
  - greglindahl 11y ago
    I know what you meant to say by "unlikely anything baring the Falcon name will ever leave low earth orbit", but note that the Falcon 9 upper stage drops off the satellite in Geostationary Transfer Orbit (GTO) for every geosynch launch. Presumably DSCOVR's launch to L1 also involved some kind of not-low transfer orbit. And the 2nd Falcon heavy launch is planned to send the upper stage to much higher than LEO, where it will drop off a variety of small satellites, including Lightsail-B. https://en.wikipedia.org/wiki/Geostationary_transfer_orbit https://en.wikipedia.org/wiki/Geostationary_transfer_orbit

Armisael16 11y ago

Eh - I'd say that it's pretty even. It takes about twice as much delta-v to get into low martian orbit as low lunar orbit, which is still less than half what it takes to get into low earth orbit. Earth has a lot of gravity and a lot of atmosphere, which is nice for living there but a real pain in the ass when you're trying to leave.

rolandog 11y ago

I've always wondered why don't they allow the testing of those rockets in stable ground? We've done crazier tests, like nuclear testing: https://www.youtube.com/watch?v=LLCF7vPanrY https://www.youtube.com/watch?v=LLCF7vPanrY

MrZongle2 11y ago
I thought the reason involved the FAA requiring SpaceX's to prove that the first stage could be guided accurately to the general pad area instead of plowing into a populated region. Landing on a barge out at sea reduces the risk of the latter.
- 001sky 11y ago
  Yep, a flyover of populated areas is avoided with an offshore lz/barge.