5 ms·

I doubt it is about gravity; it is also about the horrifying air quality on the ISS

by zanfr 2y ago

echelon 2y ago
We evolved to fit the environment of our gravity well like a glove. There's a lot that just doesn't work optimally without the envelope of gas exchange, temperature ranges, nutrient inputs, and standard gravity we have on earth. This is why I find the idea of humans colonizing the galaxy ridiculous. It won't happen unless we change our bodies substantially. We're just animals. Animals fit to the conditions of earth. (But quite honestly, it'll likely be machine intelligences that inherit the stars instead of us with our biological shortcomings.)
- op00to 2y ago
  I think we are within grasping range of genetic engineering humans to eliminate a lot of the more “interesting” bits of biology, but we are waiting for the commercial requirements to be there before really making things happen.
  - jessetemp 2y ago
    How do you genetically engineer a resistance to fluid in the lungs, or radiation exposure, or whatever all the other interesting ways to die in space are? Imagine all the suffering caused by failed attempts, people living their whole life with bad lungs so a privileged few can get a little closer to their space fantasy. I wouldn't want to be born into that experiment
- api 2y ago
  Space stations need spin gravity for long duration use. As far as living on other planets goes: there is gravity. What we don't know is how much gravity we need. We could answer this with a space station with spin gravity by trying different rotational velocities and monitoring the health effects. The Moon has about 1/6 Earth gravity. Is that enough? We don't know. Mars has a little over 1/3. Long duration space flight probably needs spin gravity too. There are two ways to do it. One is a torus shaped spacecraft. The other is two spacecraft and a tether where once they insert themselves into their cruise transfer orbit they link, extend the tether, and start orbiting each other in a spin configuration. People could go between the ships if necessary by following the tether, though this would probably only be done when strictly necessary due to the risks. There's a calculator online for spin gravity based on what we currently know about human tolerance for the Coriolis effect: https://www.artificial-gravity.com/sw/SpinCalc/ https://www.artificial-gravity.com/sw/SpinCalc/ It's not too bad. There are various workable sweet spots. Playing around I find one at 20 meter radius and 0.66g (2/3) gravity. It looks like you can't get much smaller than 15 meters diameter without ill effects, but we actually don't know. We need to try this to see what humans can actually adjust to. The simplest test short of a centrifugal station would be to put two capsules or Starships in orbit and tether them and experiment with different tether lengths and rotational velocities. Edit: actually there's a third way to do gravity on long duration flights. If you watched/read The Expanse you saw it. Accelerate to the midpoint, flip, decelerate to the destination. Unfortunately that requires insane physicsts' nightmare propulsion systems like the fusion engines in The Expanse that we do not have and won't have for the foreseeable future unless there are some crazy fusion breakthroughs.
  - aftbit 2y ago
    Yeah if we had some kind of unlimited propulsion systems, the Expanse trajectory would be optimal in so many ways. Forget about transfer orbits - just point at the target and burn. The Expanse subreddit has a lot of people doing math on such things. https://www.reddit.com/r/TheExpanse/comments/128c8rv/update_interactive_diagram_of_a_flip_and_burn/ https://www.reddit.com/r/TheExpanse/comments/128c8rv/update_...
    - api 2y ago
      AFAIK the Epstein drive from The Expanse is pretty much at the edge of known physics in terms of being plausible, with a few additional caveats. The biggest of these is that IRL those ships would have to have large heatsinks. Even if the drive were phenomenally efficient you're going to have a minimum of hundreds of megawatts of waste heat to radiate into space to avoid melting the ship. The second one is that the drive itself would be a deadly weapon. Those scenes in The Expanse where they fire up the drive near other ships or near space stations? Nope, not unless you want to fry everyone on board with X-rays. You wouldn't fire up a drive anywhere near anything you didn't want to cook with hard radiation. This last point is known as Jon's Law in space engineering and sci-fi: any sufficiently powerful space drive is also by definition a weapon of mass destruction.
      - wnoise 2y ago
        Also known as the Kzinti Lesson, from Niven's "Known Space". https://tvtropes.org/pmwiki/pmwiki.php/Main/WeaponizedExhaust https://tvtropes.org/pmwiki/pmwiki.php/Main/WeaponizedExhaus...
- EGreg 2y ago
  Why not just use rotation to generate artificial gravity via centrifugal force? I guess the answer could be that the sideways motion will drive you crazy due to coriolis forces? See 6 minutes in https://www.youtube.com/watch?v=nxeMoaxUpWk https://www.youtube.com/watch?v=nxeMoaxUpWk But they can just substitute windows with monitors that compensate for the view. Incidentally, the viewscreens on Star Trek etc. always had the ship right side up, so they probably compensated exactly in this way :)
  - prerok 2y ago
    In Star Trek they had gravity plating, so that defined which way is down. Needless to say, we have no idea yet how that would even be possible :) So, for now, the question is whether we can still do it without such a solution.
- jwells89 2y ago
  The way I see it, it’s a matter of creating suitable environments for humans in space. For the most part, that’s perfectly achievable even with current technology; the primary bottleneck is quantity of building materials, as human-friendly habitats are by necessity large and complex (space for centrifugal gravity, plus room to move around for mental health, plus space for all the requisite air process facilities and such). So this is another area where bringing down cost of pound to orbit is highly impactful. If that becomes cheap, it becomes feasible to build in orbit crafts (orbital stations, ships, etc) sufficiently large to support human-friendly habitats. Should Starship+Superheavy succeed, it will be a significant step forward in this regard since it can put the interior volume of the ISS in orbit in a single launch, and perhaps in a few decades use of resources mined from asteroids could become a consideration.
nabla9 2y ago
I think it is. https://news.ycombinator.com/item?id=40273790 https://news.ycombinator.com/item?id=40273790 Submarines and Navy ships have similar dry air.
KennyBlanken 2y ago
It's almost certainly because the microbiome of the station and occupants rarely changes. You see a similar weakening of the immune system in people who obsessively disinfect their homes. Our immune system needs to be exposed to stuff constantly.
more_corn 2y ago
The impaired immune system is about gravity. The increased bacterial mutation rate is about radiation.

I doubt it is about gravity; it is also about the horrifying air quality on the ISS

by zanfr 2y ago

I doubt it is about gravity; it is also about the horrifying air quality on the ISS

We evolved to fit the environment of our gravity well like a glove. There's a lot that just doesn't work optimally without the envelope of gas exchange, temperature ranges, nutrient inputs, and standard gravity we have on earth. This is why I find the idea of humans colonizing the galaxy ridiculous. It won't happen unless we change our bodies substantially. We're just animals. Animals fit to the conditions of earth. (But quite honestly, it'll likely be machine intelligences that inherit the stars instead of us with our biological shortcomings.)

op00to 2y ago
I think we are within grasping range of genetic engineering humans to eliminate a lot of the more “interesting” bits of biology, but we are waiting for the commercial requirements to be there before really making things happen.
- jessetemp 2y ago
  How do you genetically engineer a resistance to fluid in the lungs, or radiation exposure, or whatever all the other interesting ways to die in space are? Imagine all the suffering caused by failed attempts, people living their whole life with bad lungs so a privileged few can get a little closer to their space fantasy. I wouldn't want to be born into that experiment
api 2y ago
Space stations need spin gravity for long duration use. As far as living on other planets goes: there is gravity. What we don't know is how much gravity we need. We could answer this with a space station with spin gravity by trying different rotational velocities and monitoring the health effects. The Moon has about 1/6 Earth gravity. Is that enough? We don't know. Mars has a little over 1/3. Long duration space flight probably needs spin gravity too. There are two ways to do it. One is a torus shaped spacecraft. The other is two spacecraft and a tether where once they insert themselves into their cruise transfer orbit they link, extend the tether, and start orbiting each other in a spin configuration. People could go between the ships if necessary by following the tether, though this would probably only be done when strictly necessary due to the risks. There's a calculator online for spin gravity based on what we currently know about human tolerance for the Coriolis effect: https://www.artificial-gravity.com/sw/SpinCalc/ https://www.artificial-gravity.com/sw/SpinCalc/ It's not too bad. There are various workable sweet spots. Playing around I find one at 20 meter radius and 0.66g (2/3) gravity. It looks like you can't get much smaller than 15 meters diameter without ill effects, but we actually don't know. We need to try this to see what humans can actually adjust to. The simplest test short of a centrifugal station would be to put two capsules or Starships in orbit and tether them and experiment with different tether lengths and rotational velocities. Edit: actually there's a third way to do gravity on long duration flights. If you watched/read The Expanse you saw it. Accelerate to the midpoint, flip, decelerate to the destination. Unfortunately that requires insane physicsts' nightmare propulsion systems like the fusion engines in The Expanse that we do not have and won't have for the foreseeable future unless there are some crazy fusion breakthroughs.
- aftbit 2y ago
  Yeah if we had some kind of unlimited propulsion systems, the Expanse trajectory would be optimal in so many ways. Forget about transfer orbits - just point at the target and burn. The Expanse subreddit has a lot of people doing math on such things. https://www.reddit.com/r/TheExpanse/comments/128c8rv/update_interactive_diagram_of_a_flip_and_burn/ https://www.reddit.com/r/TheExpanse/comments/128c8rv/update_...
  - api 2y ago
    AFAIK the Epstein drive from The Expanse is pretty much at the edge of known physics in terms of being plausible, with a few additional caveats. The biggest of these is that IRL those ships would have to have large heatsinks. Even if the drive were phenomenally efficient you're going to have a minimum of hundreds of megawatts of waste heat to radiate into space to avoid melting the ship. The second one is that the drive itself would be a deadly weapon. Those scenes in The Expanse where they fire up the drive near other ships or near space stations? Nope, not unless you want to fry everyone on board with X-rays. You wouldn't fire up a drive anywhere near anything you didn't want to cook with hard radiation. This last point is known as Jon's Law in space engineering and sci-fi: any sufficiently powerful space drive is also by definition a weapon of mass destruction.
    - wnoise 2y ago
      Also known as the Kzinti Lesson, from Niven's "Known Space". https://tvtropes.org/pmwiki/pmwiki.php/Main/WeaponizedExhaust https://tvtropes.org/pmwiki/pmwiki.php/Main/WeaponizedExhaus...
EGreg 2y ago
Why not just use rotation to generate artificial gravity via centrifugal force? I guess the answer could be that the sideways motion will drive you crazy due to coriolis forces? See 6 minutes in https://www.youtube.com/watch?v=nxeMoaxUpWk https://www.youtube.com/watch?v=nxeMoaxUpWk But they can just substitute windows with monitors that compensate for the view. Incidentally, the viewscreens on Star Trek etc. always had the ship right side up, so they probably compensated exactly in this way :)
- prerok 2y ago
  In Star Trek they had gravity plating, so that defined which way is down. Needless to say, we have no idea yet how that would even be possible :) So, for now, the question is whether we can still do it without such a solution.
jwells89 2y ago
The way I see it, it’s a matter of creating suitable environments for humans in space. For the most part, that’s perfectly achievable even with current technology; the primary bottleneck is quantity of building materials, as human-friendly habitats are by necessity large and complex (space for centrifugal gravity, plus room to move around for mental health, plus space for all the requisite air process facilities and such). So this is another area where bringing down cost of pound to orbit is highly impactful. If that becomes cheap, it becomes feasible to build in orbit crafts (orbital stations, ships, etc) sufficiently large to support human-friendly habitats. Should Starship+Superheavy succeed, it will be a significant step forward in this regard since it can put the interior volume of the ISS in orbit in a single launch, and perhaps in a few decades use of resources mined from asteroids could become a consideration.

nabla9 2y ago

I think it is. https://news.ycombinator.com/item?id=40273790 https://news.ycombinator.com/item?id=40273790 Submarines and Navy ships have similar dry air.

KennyBlanken 2y ago

It's almost certainly because the microbiome of the station and occupants rarely changes. You see a similar weakening of the immune system in people who obsessively disinfect their homes. Our immune system needs to be exposed to stuff constantly.

more_corn 2y ago

The impaired immune system is about gravity. The increased bacterial mutation rate is about radiation.