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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 g

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
    On the contrary, the specialized lab for volatiles has been in space for years already on ISS. They bring samples back to prove it works, and it does. You’re now moving the goalposts from “no food is edible for 5 years” to “MREs don’t count”. And the trip from Earth to Mars is only like 4 months if you use a BIG ROCKET. :) 4 months without resupply is no huge challenge.
    - idlewords 5y ago
      The volatiles analyzer on ISS works against a short list of known compounds. For anything else you just get a generic warning and have to rely on earth labs to figure out what's going on. You can't subsist on MREs for five years. Here's a cite for you about the space food problem: https://academic.oup.com/jn/article/150/9/2242/5870322 https://academic.oup.com/jn/article/150/9/2242/5870322 However fast your imaginary rocket goes, you have to wait 26 months for the planets to align so you can use it.
  - avmich 5y ago
    > You can bring 100 of something and still be screwed if it turns out to break because of a common cause. If it breaks in storage, without been used - yes. If it breaks in use, for reasons related to usage - no.
    - idlewords 5y ago
      If your common cause is a 200A electrical fault, no number of spare 100A fuses will help you.
      - Robotbeat 5y ago
        Component level repair is something NASA does actually do on ISS. And Big Rocket allows you to also bring dissimilar redundancy.
        avmich 5y ago
Robotbeat 5y ago
You claim “ There's a large class of space flight problems you can't giant rocket your way out of.” …but every single one of your examples is wrong and proves the point that large rocket DOES solve it. For example: > The closest they come to closed-loop anything is 93% re-use of water; a Mars mission (by NASA estimates) would need 99%+. Oh, really? Why precisely do you think NASA estimated 99%+ water recycling would be required? Because MASS. >trace volatiles In fact, ISS has had trace volatiles measured in real-time for years: https://ntrs.nasa.gov/citations/20070030106 https://ntrs.nasa.gov/citations/20070030106 ISS sends samples back to validate the instrument because ISS is a testbed. It isn’t absolutely required. > there's no food that stays edible for five years Wrong. Anything will stay edible for 5 years if put in a deep freezer. And canned food lasts a LOT longer than that. “Oh, it’s not as yummy and the nutrient profile changes”, well sure. It’s nice to have fresh food. But the claim no food stays edible for 5 years is trivially false. All of us have eaten food that old, and the radiation environment isn’t enough to change that equation massively. ISS can withstand long periods without resupply, and has done so when there has been launch failures. If you can prepare for it ahead of time, it’s just a matter of having a sufficient spare pool on-orbit instead of just having the spare pool on Earth. In other words, MASS. Waste management is annoying if you don’t have canisters to place the waste in, but again, that’s also just MASS. You can put the waste in double sealed containers and then just place it outside the airlock. Can do that on orbit, so that’s actually one advantage Mars has over ISS. And I don’t see why Mars can’t have a full time ground crew, too. Time delay annoying but not in any way a showstopper. In fact, a large rocket solves these problems so completely, people who should know better still haven’t wrapped their heads around just how completely it changes the situation. The water recycling thing you repeated is illustrative of this. It literally is just mass.
- avmich 5y ago
  Space-specific problems are: 1) weightlessness - but people can deal with that, and if needed, I'm sure centrifuges can help; 2) radiation - but large shields can alleviate this problem; 3) space debris, attacking with large speeds - but we can use radars, shields, plasma clouds to reduce problems from this. With all of these problems large rockets do help.

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
  On the contrary, the specialized lab for volatiles has been in space for years already on ISS. They bring samples back to prove it works, and it does. You’re now moving the goalposts from “no food is edible for 5 years” to “MREs don’t count”. And the trip from Earth to Mars is only like 4 months if you use a BIG ROCKET. :) 4 months without resupply is no huge challenge.
  - idlewords 5y ago
    The volatiles analyzer on ISS works against a short list of known compounds. For anything else you just get a generic warning and have to rely on earth labs to figure out what's going on. You can't subsist on MREs for five years. Here's a cite for you about the space food problem: https://academic.oup.com/jn/article/150/9/2242/5870322 https://academic.oup.com/jn/article/150/9/2242/5870322 However fast your imaginary rocket goes, you have to wait 26 months for the planets to align so you can use it.
- avmich 5y ago
  > You can bring 100 of something and still be screwed if it turns out to break because of a common cause. If it breaks in storage, without been used - yes. If it breaks in use, for reasons related to usage - no.
  - idlewords 5y ago
    If your common cause is a 200A electrical fault, no number of spare 100A fuses will help you.
    - Robotbeat 5y ago
      Component level repair is something NASA does actually do on ISS. And Big Rocket allows you to also bring dissimilar redundancy.
      - avmich 5y ago

Robotbeat 5y ago

You claim “ There's a large class of space flight problems you can't giant rocket your way out of.” …but every single one of your examples is wrong and proves the point that large rocket DOES solve it. For example: > The closest they come to closed-loop anything is 93% re-use of water; a Mars mission (by NASA estimates) would need 99%+. Oh, really? Why precisely do you think NASA estimated 99%+ water recycling would be required? Because MASS. >trace volatiles In fact, ISS has had trace volatiles measured in real-time for years: https://ntrs.nasa.gov/citations/20070030106 https://ntrs.nasa.gov/citations/20070030106 ISS sends samples back to validate the instrument because ISS is a testbed. It isn’t absolutely required. > there's no food that stays edible for five years Wrong. Anything will stay edible for 5 years if put in a deep freezer. And canned food lasts a LOT longer than that. “Oh, it’s not as yummy and the nutrient profile changes”, well sure. It’s nice to have fresh food. But the claim no food stays edible for 5 years is trivially false. All of us have eaten food that old, and the radiation environment isn’t enough to change that equation massively. ISS can withstand long periods without resupply, and has done so when there has been launch failures. If you can prepare for it ahead of time, it’s just a matter of having a sufficient spare pool on-orbit instead of just having the spare pool on Earth. In other words, MASS. Waste management is annoying if you don’t have canisters to place the waste in, but again, that’s also just MASS. You can put the waste in double sealed containers and then just place it outside the airlock. Can do that on orbit, so that’s actually one advantage Mars has over ISS. And I don’t see why Mars can’t have a full time ground crew, too. Time delay annoying but not in any way a showstopper. In fact, a large rocket solves these problems so completely, people who should know better still haven’t wrapped their heads around just how completely it changes the situation. The water recycling thing you repeated is illustrative of this. It literally is just mass.

avmich 5y ago
Space-specific problems are: 1) weightlessness - but people can deal with that, and if needed, I'm sure centrifuges can help; 2) radiation - but large shields can alleviate this problem; 3) space debris, attacking with large speeds - but we can use radars, shields, plasma clouds to reduce problems from this. With all of these problems large rockets do help.