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It's only one part of your argument, but: > Waterfalls? With what gravity? Mars has gravity, and any serious space habitat would have a rotating section to si

by adwn 4y ago

It's only one part of your argument, but: > Waterfalls? With what gravity? Mars has gravity, and any serious space habitat would have a rotating section to simulate gravity.

perardi 4y ago
Yes, on that one I should have said “within a ship or station”. But within that domain, my point still stands. We have no plausible way to construct such a ship or station that produces significant pseudo-gravity by rotating. Building such a thing is basically impossible with anything we can manufacture—building a “wheel” that can rotate fast enough and be large enough to not cause wild motion sickness and have the structural integrity to hold enough mass to sustain an ecosystem is beyond our materials science, and would be impossible to lift into space.
- ceejayoz 4y ago
  > would be impossible to lift into space Why on earth would you try that?
  - m4rtink 4y ago
    Exactly, while an interesting exercise, that would be insane! But built from Lunar/asteroid material ? Sure, you can build 8 by 32 km cylinder from steel with dirt for shielding with that has a standard earth gravity just fine. No exotic materials required: https://en.wikipedia.org/wiki/O%27Neill_cylinder https://en.wikipedia.org/wiki/O%27Neill_cylinder
rich_sasha 4y ago
> rotating section to simulate gravity. thats an interesting one. Humans can only just about tolerate rotation rates of about 1 rev/min or slower or get dizzy. That means the radius of such a rotating habitat has to be quite large to achieve any meaningful acceleration, which leads to its own challenges. For example, to achieve 0.5g at rotation rate of 1/60 per second requires an arm length of 0.5 x 9.81 x 60^2 or about 10 miles. If you tentuple the rotation speed, ie 10 revs / min, you still need a radius of 180m
- sio8ohPi 4y ago
  I believe you're missing a factor of 1/(4 pi ** 2), which gives a 446m radius for 0.5g @ 1RPM.
m4rtink 4y ago
A have been thinking about all the things you could do in an aqua-park on a sizeable habitat in the zero-g section. Circular rotating pools - hello up there! And think about all the slides - possibilities are endless! :D

by adwn 4y ago

It's only one part of your argument, but: > Waterfalls? With what gravity? Mars has gravity, and any serious space habitat would have a rotating section to simulate gravity.

perardi 4y ago

Yes, on that one I should have said “within a ship or station”. But within that domain, my point still stands. We have no plausible way to construct such a ship or station that produces significant pseudo-gravity by rotating. Building such a thing is basically impossible with anything we can manufacture—building a “wheel” that can rotate fast enough and be large enough to not cause wild motion sickness and have the structural integrity to hold enough mass to sustain an ecosystem is beyond our materials science, and would be impossible to lift into space.

ceejayoz 4y ago
> would be impossible to lift into space Why on earth would you try that?
- m4rtink 4y ago
  Exactly, while an interesting exercise, that would be insane! But built from Lunar/asteroid material ? Sure, you can build 8 by 32 km cylinder from steel with dirt for shielding with that has a standard earth gravity just fine. No exotic materials required: https://en.wikipedia.org/wiki/O%27Neill_cylinder https://en.wikipedia.org/wiki/O%27Neill_cylinder

rich_sasha 4y ago

> rotating section to simulate gravity. thats an interesting one. Humans can only just about tolerate rotation rates of about 1 rev/min or slower or get dizzy. That means the radius of such a rotating habitat has to be quite large to achieve any meaningful acceleration, which leads to its own challenges. For example, to achieve 0.5g at rotation rate of 1/60 per second requires an arm length of 0.5 x 9.81 x 60^2 or about 10 miles. If you tentuple the rotation speed, ie 10 revs / min, you still need a radius of 180m

sio8ohPi 4y ago
I believe you're missing a factor of 1/(4 pi ** 2), which gives a 446m radius for 0.5g @ 1RPM.

m4rtink 4y ago

A have been thinking about all the things you could do in an aqua-park on a sizeable habitat in the zero-g section. Circular rotating pools - hello up there! And think about all the slides - possibilities are endless! :D