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It will be interesting to see how SpaceX approaches partially closed-loop life support. This is an unglamorous and refractory technical problem unrelated to wha

It will be interesting to see how SpaceX approaches partially closed-loop life support. This is an unglamorous and refractory technical problem unrelated to what they've done well in the past, but required to achieve their loftier goals.

Robotbeat 5y ago
Less important than you might think if you have as much mass margin as they do. You can do years with just oxygen (Starship HLS will use oxygen from the propellant tank) and regenerative CO2 scrubbers (which are pretty simple). Also, they have access to NASA’s technical expertise, and NASA has been working with closed loop life support for decades on ISS, now. Tons and tons and tons of mass margin covers a multitude of sins. A lot of the difficulties of “must haves” for Mars are really just a side effect of substantial mass constraints. Relax those, and it’s much simpler with tech close to what they’ve already demonstrated.
- rbanffy 5y ago
  > Tons and tons and tons of mass margin covers a multitude of sins This is also why building spacecraft is so expensive - they need to be engineered to the absolute minimum mass that does the job and that takes the majority of the time. Relax that and you cut design time to 10% of it used to be.
  - wffurr 5y ago
    There's a nice writeup of what 100X more launch capability means for space missions on this blog: https://caseyhandmer.wordpress.com/2021/10/28/starship-is-still-not-understood/ https://caseyhandmer.wordpress.com/2021/10/28/starship-is-st... We'll see if SpaceX can actually achieve their cost-to-orbit goals. Progress so far is promising, but they have a long way to go still.
    - Robotbeat 5y ago
      “ However, limited water, storage, crew time, and food preparation capability (e.g., add water, heat) restrict the crew to a limited choice of shelf-stable, single-serving food products either in their natural form or preserved by dehydration, retort thermostabilization, or irradiation.” So “limited water, storage, crew time, and food preparation capability (e.g., add water, heat)” all sound like things that can be addressed either directly or indirectly by “giant rocket.” And using a freezer for food (which a big rocket would allow) isn’t in the list of options they mainly considered. Deep frozen food is a very straightforward way of preserving food and high levels of nutrients for a very long time. And as far as SpaceX meeting their goals, I agree they haven’t done it YET, but in order for Artemis to work, they now have to achieve those goals. It takes on the order of 10 Starship launches per HLS mission, more than a Mars launch would require! And they’re only charging like $2.5 billion for that, which includes two HLS missions and HLS development. Starship working and meeting its goals (at least enough for initial Mars mission) is now something NASA is reliant on for the critical path for Artemis. NASA is effectively all-in on Starship now.
- idlewords 5y ago
  Everything's easy in space until it has to run for three years or more without breaking. The idea that mass margin fixes everything falls apart a bit when you get into details. Some examples: there's no good way to analyze air/water for trace volatiles on a spacecraft (ISS flies samples down to earth), there's no food that stays edible for five years, water recapture (which has to be closed loop) has been a headache for the entire life of ISS, so has managing trash and human waste. You're also wrong that ISS has had anything like closed-loop life support. They are entirely dependent on regular resupply, a full-time ground crew, and lab analysis done on earth. The closest they come to closed-loop anything is 93% re-use of water; a Mars mission (by NASA estimates) would need 99%+. There's a large class of space flight problems you can't giant rocket your way out of.
  - cnlevy 5y ago
    On the contrary, I'm convinced weight can (ab)solve many sins. The JWST's solar shade would have been much less difficult to develop if it wasn't so weight constrained. > Everything's easy in space until it has to run for three years or more without breaking. Only 90% reliability ? So let's bring 5 of each, since we're not limited by weight, we get to 99,999% > there's no good way to analyze air/water for trace volatiles on a spacecraft How much weights a specialized lab for that ? > there's no food that stays edible for five years Its been solved a long time ago: dried and salted food, basically https://www.atlasobscura.com/articles/ship-food-research-recreation-beer https://www.atlasobscura.com/articles/ship-food-research-rec... > Mars mission (by NASA estimates) would need 99%+ There are glaciers on Mars. Its about the only thing they wont have to bring.
    - idlewords 5y ago
      You can bring 100 of something and still be screwed if it turns out to break because of a common cause. You'd think people on this site of all places would understand that reliability engineering is hard. 2. There is no specialized lab for it that works in space. It has to be invented. 3. Astronauts can't survive on ship's biscuit and space MREs. Malnutrition is already a problem on ISS. 4. There are no glaciers between Earth and Mars, and by the way you're not allowed to touch the Martian glaciers because of contamination risk.

Robotbeat 5y ago

Less important than you might think if you have as much mass margin as they do. You can do years with just oxygen (Starship HLS will use oxygen from the propellant tank) and regenerative CO2 scrubbers (which are pretty simple). Also, they have access to NASA’s technical expertise, and NASA has been working with closed loop life support for decades on ISS, now. Tons and tons and tons of mass margin covers a multitude of sins. A lot of the difficulties of “must haves” for Mars are really just a side effect of substantial mass constraints. Relax those, and it’s much simpler with tech close to what they’ve already demonstrated.

rbanffy 5y ago
> Tons and tons and tons of mass margin covers a multitude of sins This is also why building spacecraft is so expensive - they need to be engineered to the absolute minimum mass that does the job and that takes the majority of the time. Relax that and you cut design time to 10% of it used to be.
- wffurr 5y ago
  There's a nice writeup of what 100X more launch capability means for space missions on this blog: https://caseyhandmer.wordpress.com/2021/10/28/starship-is-still-not-understood/ https://caseyhandmer.wordpress.com/2021/10/28/starship-is-st... We'll see if SpaceX can actually achieve their cost-to-orbit goals. Progress so far is promising, but they have a long way to go still.
  - Robotbeat 5y ago
    “ However, limited water, storage, crew time, and food preparation capability (e.g., add water, heat) restrict the crew to a limited choice of shelf-stable, single-serving food products either in their natural form or preserved by dehydration, retort thermostabilization, or irradiation.” So “limited water, storage, crew time, and food preparation capability (e.g., add water, heat)” all sound like things that can be addressed either directly or indirectly by “giant rocket.” And using a freezer for food (which a big rocket would allow) isn’t in the list of options they mainly considered. Deep frozen food is a very straightforward way of preserving food and high levels of nutrients for a very long time. And as far as SpaceX meeting their goals, I agree they haven’t done it YET, but in order for Artemis to work, they now have to achieve those goals. It takes on the order of 10 Starship launches per HLS mission, more than a Mars launch would require! And they’re only charging like $2.5 billion for that, which includes two HLS missions and HLS development. Starship working and meeting its goals (at least enough for initial Mars mission) is now something NASA is reliant on for the critical path for Artemis. NASA is effectively all-in on Starship now.
idlewords 5y ago
Everything's easy in space until it has to run for three years or more without breaking. The idea that mass margin fixes everything falls apart a bit when you get into details. Some examples: there's no good way to analyze air/water for trace volatiles on a spacecraft (ISS flies samples down to earth), there's no food that stays edible for five years, water recapture (which has to be closed loop) has been a headache for the entire life of ISS, so has managing trash and human waste. You're also wrong that ISS has had anything like closed-loop life support. They are entirely dependent on regular resupply, a full-time ground crew, and lab analysis done on earth. The closest they come to closed-loop anything is 93% re-use of water; a Mars mission (by NASA estimates) would need 99%+. There's a large class of space flight problems you can't giant rocket your way out of.
- cnlevy 5y ago
  On the contrary, I'm convinced weight can (ab)solve many sins. The JWST's solar shade would have been much less difficult to develop if it wasn't so weight constrained. > Everything's easy in space until it has to run for three years or more without breaking. Only 90% reliability ? So let's bring 5 of each, since we're not limited by weight, we get to 99,999% > there's no good way to analyze air/water for trace volatiles on a spacecraft How much weights a specialized lab for that ? > there's no food that stays edible for five years Its been solved a long time ago: dried and salted food, basically https://www.atlasobscura.com/articles/ship-food-research-recreation-beer https://www.atlasobscura.com/articles/ship-food-research-rec... > Mars mission (by NASA estimates) would need 99%+ There are glaciers on Mars. Its about the only thing they wont have to bring.
  - idlewords 5y ago
    You can bring 100 of something and still be screwed if it turns out to break because of a common cause. You'd think people on this site of all places would understand that reliability engineering is hard. 2. There is no specialized lab for it that works in space. It has to be invented. 3. Astronauts can't survive on ship's biscuit and space MREs. Malnutrition is already a problem on ISS. 4. There are no glaciers between Earth and Mars, and by the way you're not allowed to touch the Martian glaciers because of contamination risk.