3 ms·

Did you read the book? The limitation was that it takes 6 months+ to get there. Assemble a mission from scratch in weeks - it'll still take you six months to

Did you read the book? The limitation was that it takes 6 months+ to get there. Assemble a mission from scratch in weeks - it'll still take you six months to get there.

basementcat 5y ago
With a big enough rocket, you're no longer constrained to use a minimum energy trajectory. You can cut down the travel time but you'll need to do additional burns to speed up and slow down (with corresponding additional risks).
- rbanffy 5y ago
  Not only that - with cheaper launches you could have more frequent launches. At any given time there would be at least one supply ship on its way to Mars that could be diverted to a different landing site. Even if the capability for multiple launches a day never materializes, it'd be safe to assume there could be a vehicle ready to launch in weeks. With a payload capacity of 100 tons, it could do a significantly higher energy trajectory with supplies for a single person. With 5 tons of food and replacement parts per flight, you'd still have 95 fewer tons to push to Mars. Not sure about my math, but it looks like it'd have about 11 km/s of extra delta-v, which seems to be a lot (more than twice what you need for an optimal trip from the Earth to Mars). And that is if the only upper stage developed for Superheavy is the reusable Starship. An expendable upper stage could carry a lot more fuel and cargo. On a mission you don't expect the vehicle to return, it'd be fine to use a lighter one. I'm thinking a truncated Starship with a Red Dragon lander, doing a burn to slow down enough the lander can get safely to the surface with the supplies needed. Finally, with that much launch capacity, I'd be pretty sure there would be more than one crew on Mars at any time. Watney's rescuers could probably just drive to his door with food from over the hills.
- fpoling 5y ago
  You do not necessary need more fuel to slow down. Mars atmosphere can absorb few extra km/s above 5 km/s with typical landing maneuver as long as the heat shield can handle that. On Earth Starship must handle 8 km/s re-entry and potentially up to 11 km/s if direct landing from Lunar orbit will be feasible.
m4rtink 5y ago
I read the book and that was one of the least believable parts, that they were already into the third Mars landing mission without any cheap reusable launch vehicles! Like seriously, how much that must have cost so far ?? Not just money, but all the time thousands of people would have invested into producing maybe hundreds of booster stages that would then be just dumped to the sea. Such a colloidal waste it must have been! No wonder every margin is so thin in the book and even just launching a module with food is a major hurdle... Also there is really no apparent orbital infrastructure mentioned anywhere in the book, likely again due to the stupidly high ELV launch costs. In a proper RLV/Starship world Watney would either most likely not get stranded due to the whole operation being done by a fleet of ships, with some likely kept in reserve as spares. And even if he managed to get stranded and was lacking supplies to last to the next synod (say the crate with emergency supplies turned out to by logistic mistake contain chainsaws instead) you could very likely get a sacrificial starship with a couple tons of payload, fueled from one of your propelant depots in Earth orbit, to Mars very quickly.
- rbanffy 5y ago
  We have to remember that, when The Martian was written, reusable boosters were... science fiction.
- numpad0 5y ago
  Wasn’t the Martian LV an Ares series vehicle? The good old Shuttle SRB with a capsule on top. Those are kind of cheap as they are.
  - m4rtink 5y ago
    The original Ares 1 dumped also an expensive hydrogen upper stage, all that while barely bringing the crew capsule into orbit, ideally not shaking the crew to death (IIRC the main reason for it bring canceled in the end). But maybe the society in The Martian universe is just so unimaginably rich they can pull that all off even using those super inefficient expendable rockets. :)
    - 5y ago
jhgb 5y ago
> The limitation was that it takes 6 months+ to get there. Assemble a mission from scratch in weeks - it'll still take you six months to get there. I'm pretty sure the plans are for ~4 month Starship trips to Mars. The real limitation may be in launch windows. But with SpaceX's "shotgun approach" the real solution would probably be to use an already landed cargo Starship.

Did you read the book? The limitation was that it takes 6 months+ to get there. Assemble a mission from scratch in weeks - it'll still take you six months to get there.

basementcat 5y ago

With a big enough rocket, you're no longer constrained to use a minimum energy trajectory. You can cut down the travel time but you'll need to do additional burns to speed up and slow down (with corresponding additional risks).

rbanffy 5y ago
Not only that - with cheaper launches you could have more frequent launches. At any given time there would be at least one supply ship on its way to Mars that could be diverted to a different landing site. Even if the capability for multiple launches a day never materializes, it'd be safe to assume there could be a vehicle ready to launch in weeks. With a payload capacity of 100 tons, it could do a significantly higher energy trajectory with supplies for a single person. With 5 tons of food and replacement parts per flight, you'd still have 95 fewer tons to push to Mars. Not sure about my math, but it looks like it'd have about 11 km/s of extra delta-v, which seems to be a lot (more than twice what you need for an optimal trip from the Earth to Mars). And that is if the only upper stage developed for Superheavy is the reusable Starship. An expendable upper stage could carry a lot more fuel and cargo. On a mission you don't expect the vehicle to return, it'd be fine to use a lighter one. I'm thinking a truncated Starship with a Red Dragon lander, doing a burn to slow down enough the lander can get safely to the surface with the supplies needed. Finally, with that much launch capacity, I'd be pretty sure there would be more than one crew on Mars at any time. Watney's rescuers could probably just drive to his door with food from over the hills.
fpoling 5y ago
You do not necessary need more fuel to slow down. Mars atmosphere can absorb few extra km/s above 5 km/s with typical landing maneuver as long as the heat shield can handle that. On Earth Starship must handle 8 km/s re-entry and potentially up to 11 km/s if direct landing from Lunar orbit will be feasible.

m4rtink 5y ago

I read the book and that was one of the least believable parts, that they were already into the third Mars landing mission without any cheap reusable launch vehicles! Like seriously, how much that must have cost so far ?? Not just money, but all the time thousands of people would have invested into producing maybe hundreds of booster stages that would then be just dumped to the sea. Such a colloidal waste it must have been! No wonder every margin is so thin in the book and even just launching a module with food is a major hurdle... Also there is really no apparent orbital infrastructure mentioned anywhere in the book, likely again due to the stupidly high ELV launch costs. In a proper RLV/Starship world Watney would either most likely not get stranded due to the whole operation being done by a fleet of ships, with some likely kept in reserve as spares. And even if he managed to get stranded and was lacking supplies to last to the next synod (say the crate with emergency supplies turned out to by logistic mistake contain chainsaws instead) you could very likely get a sacrificial starship with a couple tons of payload, fueled from one of your propelant depots in Earth orbit, to Mars very quickly.

rbanffy 5y ago
We have to remember that, when The Martian was written, reusable boosters were... science fiction.
numpad0 5y ago
Wasn’t the Martian LV an Ares series vehicle? The good old Shuttle SRB with a capsule on top. Those are kind of cheap as they are.
- m4rtink 5y ago
  The original Ares 1 dumped also an expensive hydrogen upper stage, all that while barely bringing the crew capsule into orbit, ideally not shaking the crew to death (IIRC the main reason for it bring canceled in the end). But maybe the society in The Martian universe is just so unimaginably rich they can pull that all off even using those super inefficient expendable rockets. :)
  - 5y ago

jhgb 5y ago

> The limitation was that it takes 6 months+ to get there. Assemble a mission from scratch in weeks - it'll still take you six months to get there. I'm pretty sure the plans are for ~4 month Starship trips to Mars. The real limitation may be in launch windows. But with SpaceX's "shotgun approach" the real solution would probably be to use an already landed cargo Starship.