5 ms·

This is more the sort of engine you develop if you're going for an Apollo style mission where there's a mother craft that goes into orbit and a separate lander

This is more the sort of engine you develop if you're going for an Apollo style mission where there's a mother craft that goes into orbit and a separate lander goes down to the surface. A NTR's poor TWR compared to conventional combustion rockets means it would be a bad ascent stage. I wouldn't assume the plan relies on ISRU at all but if it do having to carry the resulting hydrogen up to orbit on the ascent stage will be a big limiting factor so not keeping the oxygen isn't so large a flaw. And if you're carrying the fuel to orbit on another rocket you want to get as high an ISP as you can manage with what you bring up. All of which isn't to say this would be a good plan. I've drunk the SpaceX koolaid on the topic. But if it's a bad plan at least it isn't a stupid one and there are reasons behind things.

jhgb 4y ago
Yeah, I did notice that the original NTR plans arose from the wish to upgrade Saturn V with its limited "throw weight" at third stage separation (http://www.astronautix.com/s/saturnc-5n.html http://www.astronautix.com/s/saturnc-5n.html). It doesn't seem to make a lot of sense to design a propulsion unit for a sixty year old mission architecture today, though.
ncmncm 4y ago
Yeah, the SpaceX Kool-aid, at least as regards Mars colonization, is about as lethal as the Jonestown variety. There will be no Mars colonization on Starships, whatever Elon says. Starship is just wholly inadequate to the task. Neither will there be any sub-orbital passenger or freight service on it. Starship should be adequate for lofting lots of Starlinks, for getting to the moon, and for boosting just amazingly well-equipped 100t outer solar system probes and telescopes. It might suffice for a quick visit to Mars with a half-dozen crew. (BTW, 9, not 6 months, each way.) Probably the only way to make even that work would be to send two ships strung on a cable, nose to nose, spun for centrifugal gee force, so they could still walk when they got there. Maybe the second ship carries hydrogen (as ammonia?) to bond to ISR carbon to come home on. And solar panels, to crack the carbon. But the first thing any attempted colonist would transmit back is "Can I please come home?"
- pfdietz 4y ago
  A Mars colony will involve living in small metal boxes, surrounded by danger, with ruinous prices on things, if they are available at all. We can get the same experience today, without going to Mars, in places called "prisons".
  - skissane 4y ago
    I think, in the medium term, all Musk is actually aiming at, is a crewed research station on Mars, with a few dozen people living in it. Rather similar to what we already have in Antarctica. People will sign up to go. First person to step foot on Mars gets their name in the history books, next to Neil Armstrong. The rest get to join a very elite club. I suppose prison is kind of a club too, but nothing elite about it. And Musk will call it a "colony"–aspirational naming. And maybe, one day, in centuries to come, it will actually evolve into one. I don't think Musk has really thought a lot about how to get from the "colony-in-name-only crewed research station" to a genuine colony – that's too many steps ahead. He just trusts he'll work it out when he gets there, or if he doesn't live that long, somebody else will.
    - ncmncm 4y ago
      "Aspirational naming" is quite a curious synonym for lying. And to say that Musk has not thought much about X, for any X, is quite an understatement. The closer you look at anything he says, the less evidence of thought you can find. Today is a golden age for glib grifters.
      - skissane 4y ago
        Well, look at SpaceX: he founded it, he remains its CEO&CTO, and in 10 years it has gone from 0% market share to over 50% global market share–which was achieved, not through anticompetitive subterfuge, but simply by building a substantially better product at a substantially lower cost (and whatever government subsidies were involved, were made available in even greater amounts to competing companies which failed to leverage them into the same market success). Obviously he must have some capacity for intelligent thought to be able to pull that off. Of course, he employs many brilliant engineers, without whom none of that would have been possible–but, as founder/CEO, he created and sustained the corporate environment which made it possible for them to achieve that.

jhgb 4y ago

Yeah, I did notice that the original NTR plans arose from the wish to upgrade Saturn V with its limited "throw weight" at third stage separation (http://www.astronautix.com/s/saturnc-5n.html http://www.astronautix.com/s/saturnc-5n.html). It doesn't seem to make a lot of sense to design a propulsion unit for a sixty year old mission architecture today, though.

ncmncm 4y ago

Yeah, the SpaceX Kool-aid, at least as regards Mars colonization, is about as lethal as the Jonestown variety. There will be no Mars colonization on Starships, whatever Elon says. Starship is just wholly inadequate to the task. Neither will there be any sub-orbital passenger or freight service on it. Starship should be adequate for lofting lots of Starlinks, for getting to the moon, and for boosting just amazingly well-equipped 100t outer solar system probes and telescopes. It might suffice for a quick visit to Mars with a half-dozen crew. (BTW, 9, not 6 months, each way.) Probably the only way to make even that work would be to send two ships strung on a cable, nose to nose, spun for centrifugal gee force, so they could still walk when they got there. Maybe the second ship carries hydrogen (as ammonia?) to bond to ISR carbon to come home on. And solar panels, to crack the carbon. But the first thing any attempted colonist would transmit back is "Can I please come home?"

pfdietz 4y ago
A Mars colony will involve living in small metal boxes, surrounded by danger, with ruinous prices on things, if they are available at all. We can get the same experience today, without going to Mars, in places called "prisons".
- skissane 4y ago
  I think, in the medium term, all Musk is actually aiming at, is a crewed research station on Mars, with a few dozen people living in it. Rather similar to what we already have in Antarctica. People will sign up to go. First person to step foot on Mars gets their name in the history books, next to Neil Armstrong. The rest get to join a very elite club. I suppose prison is kind of a club too, but nothing elite about it. And Musk will call it a "colony"–aspirational naming. And maybe, one day, in centuries to come, it will actually evolve into one. I don't think Musk has really thought a lot about how to get from the "colony-in-name-only crewed research station" to a genuine colony – that's too many steps ahead. He just trusts he'll work it out when he gets there, or if he doesn't live that long, somebody else will.
  - ncmncm 4y ago
    "Aspirational naming" is quite a curious synonym for lying. And to say that Musk has not thought much about X, for any X, is quite an understatement. The closer you look at anything he says, the less evidence of thought you can find. Today is a golden age for glib grifters.
    - skissane 4y ago
      Well, look at SpaceX: he founded it, he remains its CEO&CTO, and in 10 years it has gone from 0% market share to over 50% global market share–which was achieved, not through anticompetitive subterfuge, but simply by building a substantially better product at a substantially lower cost (and whatever government subsidies were involved, were made available in even greater amounts to competing companies which failed to leverage them into the same market success). Obviously he must have some capacity for intelligent thought to be able to pull that off. Of course, he employs many brilliant engineers, without whom none of that would have been possible–but, as founder/CEO, he created and sustained the corporate environment which made it possible for them to achieve that.