5 ms·

Make the transit ship spin. Surround the habitable parts with water and other materials. It’s so simple but nobody seems to be aware that these are solved probl

by seaorg 5y ago

Make the transit ship spin. Surround the habitable parts with water and other materials. It’s so simple but nobody seems to be aware that these are solved problems.

Supermancho 5y ago
> It’s so simple but nobody seems to be aware that these are solved problems. It isnt reasonable to assume napkin solutions are "so simple" in practice or have not been considered. There are plenty of people smarter than either of us that look at these problems.
- seaorg 5y ago
  The problem isn’t the smart people who look at these problems. It’s the collective behavior of the masses to have amnesia about basic physics.
  - defterGoose 5y ago
    Maybe the problem is people filling air with pseudo-scientific BS all the time, for instance, i dunno, Scientology?
    - seaorg 5y ago
      I’m not a Scientologist.
jccalhoun 5y ago
Lots of people have thought of similar things. I know I have read scifi which uses water for shielding but I can't think of a specific name. However, water isn't light. According to this post on stack exchange it would take something like 330,000kg of water to shield a crew. Getting that into orbit is a big task.
- nojokes 5y ago
  Does something have better shielding mass ratio? But water itself can be more useful perhaps.
- seaorg 5y ago
  It’s just money.
Symmetry 5y ago
You need a pretty big ship to do that fast enough for Earth gravity and not have the astronauts nauseous all the time. You could use a tether but NASA has had problems with tethers in the past and is a bit shy about them.
- mdorazio 5y ago
  You don't need Earth gravity. All the problems with bone loss and ailments are from microgravity. I can't find any studies on reduced gravity (it would be really hard to test), but there's no reason to assume that something like half a gravity + exercise and supplements wouldn't significantly reduce health issues.
- seaorg 5y ago
  What’s the minimum radius?
maccam94 5y ago
Prior to Starship, just getting large enough structures and mass into space has been the limiting factor. There is a minimum diameter for spin gravity to avoid disorienting vestibular side-effects. Spinning two spacecraft attached by a tether might work for short-term use cases, but I don't know how feasible it is to keep that stable for months or years. Transporting adequate volumes of water shielding is probably infeasible for SpaceX's planned Mars mission profile: - you need 1 meter of water shielding to reduce radiation to safe levels[0] - each cubic meter of water is 1 metric ton - Starship's circumference is ~28 meters Assuming you only shield 4 meters of the length of the ship, not counting the top and bottom cross sections of the cylinder, you've already blown past the 100T payload capacity of Starship. [0]: https://space.stackexchange.com/a/1826 https://space.stackexchange.com/a/1826
- nojokes 5y ago
  You can use multiple deliveries when water is added in orbit.
  - maccam94 5y ago
    Yes, that works fine for a space station, but not so much for a rocket that needs to accelerate and decelerate it on a trip to Mars (and back).
    - nojokes 5y ago
      Especially for such rocket because you may need also additional fueling.
      - maccam94 5y ago
        Starship already requires in-orbit fueling to fully refill its tanks for the outbound journey to Mars when loaded to its 100T payload limit. It cannot carry additional fuel to accelerate and decelerate another 100T+ of water shielding. SpaceX currently plans that Starship will return to Earth from the Martian surface without in-orbit refueling. I don't know the payload capacity for that trip offhand, but again water shielding would exceed the 100T mark and it would be an incredible amount of added complexity to do in-orbit refueling there with the limited fuel generation infrastructure.
prerok 5y ago
Since it's basic physics, how much power do you think is required to spin a cubic meter of water at 1g centrifugal force? How much energy is required to do that for a year? I'm pretty sure it's lots :) I think that we just haven't figured out how to do this, so the "obvious" solution is not on the table (yet).
- seaorg 5y ago
  You should learn basic physics before you presume to know it... It’s not a question of power. You could could get it spinning quickly or slowly with high or low power respectively but the question you are trying to ask it how much energy is required. The amount of energy to get the thing spinning is the same no matter what. And once you get it spinning, you’re done. It will keep spinning. I think there is a certain law that pertains to that. Something to do with fig newtons. The amount of energy that is required is trivial compared to the other energy budgets. And it would be spun up at low power over the course of hours or days.

by seaorg 5y ago

Make the transit ship spin. Surround the habitable parts with water and other materials. It’s so simple but nobody seems to be aware that these are solved problems.

Supermancho 5y ago

> It’s so simple but nobody seems to be aware that these are solved problems. It isnt reasonable to assume napkin solutions are "so simple" in practice or have not been considered. There are plenty of people smarter than either of us that look at these problems.

seaorg 5y ago
The problem isn’t the smart people who look at these problems. It’s the collective behavior of the masses to have amnesia about basic physics.
- defterGoose 5y ago
  Maybe the problem is people filling air with pseudo-scientific BS all the time, for instance, i dunno, Scientology?
  - seaorg 5y ago
    I’m not a Scientologist.

jccalhoun 5y ago

Lots of people have thought of similar things. I know I have read scifi which uses water for shielding but I can't think of a specific name. However, water isn't light. According to this post on stack exchange it would take something like 330,000kg of water to shield a crew. Getting that into orbit is a big task.

nojokes 5y ago
Does something have better shielding mass ratio? But water itself can be more useful perhaps.
seaorg 5y ago
It’s just money.

Symmetry 5y ago

You need a pretty big ship to do that fast enough for Earth gravity and not have the astronauts nauseous all the time. You could use a tether but NASA has had problems with tethers in the past and is a bit shy about them.

mdorazio 5y ago
You don't need Earth gravity. All the problems with bone loss and ailments are from microgravity. I can't find any studies on reduced gravity (it would be really hard to test), but there's no reason to assume that something like half a gravity + exercise and supplements wouldn't significantly reduce health issues.
seaorg 5y ago
What’s the minimum radius?

maccam94 5y ago

Prior to Starship, just getting large enough structures and mass into space has been the limiting factor. There is a minimum diameter for spin gravity to avoid disorienting vestibular side-effects. Spinning two spacecraft attached by a tether might work for short-term use cases, but I don't know how feasible it is to keep that stable for months or years. Transporting adequate volumes of water shielding is probably infeasible for SpaceX's planned Mars mission profile: - you need 1 meter of water shielding to reduce radiation to safe levels[0] - each cubic meter of water is 1 metric ton - Starship's circumference is ~28 meters Assuming you only shield 4 meters of the length of the ship, not counting the top and bottom cross sections of the cylinder, you've already blown past the 100T payload capacity of Starship. [0]: https://space.stackexchange.com/a/1826 https://space.stackexchange.com/a/1826

nojokes 5y ago
You can use multiple deliveries when water is added in orbit.
- maccam94 5y ago
  Yes, that works fine for a space station, but not so much for a rocket that needs to accelerate and decelerate it on a trip to Mars (and back).
  - nojokes 5y ago
    Especially for such rocket because you may need also additional fueling.
    - maccam94 5y ago
      Starship already requires in-orbit fueling to fully refill its tanks for the outbound journey to Mars when loaded to its 100T payload limit. It cannot carry additional fuel to accelerate and decelerate another 100T+ of water shielding. SpaceX currently plans that Starship will return to Earth from the Martian surface without in-orbit refueling. I don't know the payload capacity for that trip offhand, but again water shielding would exceed the 100T mark and it would be an incredible amount of added complexity to do in-orbit refueling there with the limited fuel generation infrastructure.

prerok 5y ago

Since it's basic physics, how much power do you think is required to spin a cubic meter of water at 1g centrifugal force? How much energy is required to do that for a year? I'm pretty sure it's lots :) I think that we just haven't figured out how to do this, so the "obvious" solution is not on the table (yet).

seaorg 5y ago
You should learn basic physics before you presume to know it... It’s not a question of power. You could could get it spinning quickly or slowly with high or low power respectively but the question you are trying to ask it how much energy is required. The amount of energy to get the thing spinning is the same no matter what. And once you get it spinning, you’re done. It will keep spinning. I think there is a certain law that pertains to that. Something to do with fig newtons. The amount of energy that is required is trivial compared to the other energy budgets. And it would be spun up at low power over the course of hours or days.