4 ms·

Notwithstanding Musk's continuous lying about it, Starship would take nine months to get there, not six. Once there, of course, after a single trip around the

by ncmncm 4y ago

Notwithstanding Musk's continuous lying about it, Starship would take nine months to get there, not six. Once there, of course, after a single trip around the hab can (can hab?), you would start counting days ... sols ... until you could go home. Presuming it would be possible and permitted. If not, sucks to be you. Mars is a frozen wasteland with nothing of enduring interest. The only export of any value conceivable would be excess Raptor engines taken off of landers, with their bells cut off.

q7xvh97o2pDhNrh 4y ago
I wonder if they'd have some pseudo-restaurants in the habitation area, to help simulate some sense of normalcy. If they do, and if you then saw one of your fellow travelers eating an interesting-looking sandwich, and you wanted to find out what it was, you would have the rare perk of walking up and dropping a pun that's been decades in the making: "Can hab cheeseburger?"
notfish 4y ago
Nine months is the duration of a Hohmann transfer to mars, not necessarily the shortest possible for starship - since starship has ~6900 m/s delta v ( https://twitter.com/elonmusk/status/1151300180148252674 https://twitter.com/elonmusk/status/1151300180148252674 ) and an earth-mars transfer only requires 3900m/s I think 6 months is well within the realm of plausible.
- ncmncm 4y ago
  There is no possibility of a lone can blasting out there, whatever the delta-V it could muster. You need, at least, two cans to swing at ends of a boom so your crew does not arrive unable to walk. You might want something attached at the axis, besides. That thing might do all the boosting, with the cans' Raptors used just to land with. ISRU fantasies notwithstanding, they need to carry enough fuel to blast off again, come time to go home. The cans get benefit of aerobraking on the way down. The mainframe will need to shed its excess velocity some other way. There's nothing else near enough by to swing around. It will need to have brought along enough fuel to boost home, besides. Maybe it used ion thrusters all the way out, and can use them to creep back to Mars in time to pick up the cans and head home. An alternative is that there is no mainframe, just the boom, and you re-fold and stow it before arrival. Somebody else would have boosted your cans out there, maybe a pair of Superheavys, so your cans won't have to arrive empty. I wonder if a Superheavy with no can stacked on could make it to orbit in one stage. Probably you would unship their engines on orbit, and install a couple of vacuum Raptors in their place before sending them careering out of the solar system.
bryananderson 4y ago
I don’t know the numbers for Starship specifically, but this is a matter of how much fuel you have available to burn, and six months has long been considered reasonable. For a free-return trajectory (end up back at Earth if you’re not willing or able to conduct a Mars entry burn), the minimum-energy trajectory takes 250 days (8.3 months) and requires 3.34 km/s delta-V. Getting it down to 180 days takes 5.08 km/s, so about 50% more delta-V (and fuel). Getting there faster is possible but starts to run into diminishing returns, especially because it makes aerobraking at Mars more and more difficult, requiring even more fuel for slowing down on arrival. These numbers are from Robert Zubrin’s “The Case for Mars” (1996) which assumed a six-month transit time would be the norm for human missions. Fantasies of moving to Mars to escape climate change are stupid—even under the best terraforming projections and the worst climate change projections, Earth will be several orders of magnitude more habitable for centuries at least. But the scientific return from a once-warm-and-wet world is more than enough reason to go. Someone like NASA’s Jessica Watkins, who did her dissertation on Martian geology at Caltech, certainly would not be counting down the sols.

by ncmncm 4y ago

q7xvh97o2pDhNrh 4y ago

I wonder if they'd have some pseudo-restaurants in the habitation area, to help simulate some sense of normalcy. If they do, and if you then saw one of your fellow travelers eating an interesting-looking sandwich, and you wanted to find out what it was, you would have the rare perk of walking up and dropping a pun that's been decades in the making: "Can hab cheeseburger?"

notfish 4y ago

Nine months is the duration of a Hohmann transfer to mars, not necessarily the shortest possible for starship - since starship has ~6900 m/s delta v ( https://twitter.com/elonmusk/status/1151300180148252674 https://twitter.com/elonmusk/status/1151300180148252674 ) and an earth-mars transfer only requires 3900m/s I think 6 months is well within the realm of plausible.

ncmncm 4y ago
There is no possibility of a lone can blasting out there, whatever the delta-V it could muster. You need, at least, two cans to swing at ends of a boom so your crew does not arrive unable to walk. You might want something attached at the axis, besides. That thing might do all the boosting, with the cans' Raptors used just to land with. ISRU fantasies notwithstanding, they need to carry enough fuel to blast off again, come time to go home. The cans get benefit of aerobraking on the way down. The mainframe will need to shed its excess velocity some other way. There's nothing else near enough by to swing around. It will need to have brought along enough fuel to boost home, besides. Maybe it used ion thrusters all the way out, and can use them to creep back to Mars in time to pick up the cans and head home. An alternative is that there is no mainframe, just the boom, and you re-fold and stow it before arrival. Somebody else would have boosted your cans out there, maybe a pair of Superheavys, so your cans won't have to arrive empty. I wonder if a Superheavy with no can stacked on could make it to orbit in one stage. Probably you would unship their engines on orbit, and install a couple of vacuum Raptors in their place before sending them careering out of the solar system.

bryananderson 4y ago

I don’t know the numbers for Starship specifically, but this is a matter of how much fuel you have available to burn, and six months has long been considered reasonable. For a free-return trajectory (end up back at Earth if you’re not willing or able to conduct a Mars entry burn), the minimum-energy trajectory takes 250 days (8.3 months) and requires 3.34 km/s delta-V. Getting it down to 180 days takes 5.08 km/s, so about 50% more delta-V (and fuel). Getting there faster is possible but starts to run into diminishing returns, especially because it makes aerobraking at Mars more and more difficult, requiring even more fuel for slowing down on arrival. These numbers are from Robert Zubrin’s “The Case for Mars” (1996) which assumed a six-month transit time would be the norm for human missions. Fantasies of moving to Mars to escape climate change are stupid—even under the best terraforming projections and the worst climate change projections, Earth will be several orders of magnitude more habitable for centuries at least. But the scientific return from a once-warm-and-wet world is more than enough reason to go. Someone like NASA’s Jessica Watkins, who did her dissertation on Martian geology at Caltech, certainly would not be counting down the sols.