Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Study shows space travel is harmful to the brain

phys.org

Post reply on HN
Print view View original

11–20 of 20 posts

Re: Study shows space travel is harmful to the brain

#11

Post by paulovsk »

iwwr wrote: post #9

"While space is full of radiation, the earth's magnetic field generally protects the planet and people in low earth orbit from these particles." The magnetic field protects only against charged particles (usually coming from the Sun). Galactic cosmic rays or solar flares are not blocked. The atmosphere blocks most of that, as well as the planet itself. In low-Earth orbit, you have half the horizon covered by the plan…

How a rotating space would help the problems with lack of gravity? I mean, our gravity is up-down and the acceleration from a rotating environment would be lateral. Doesn't that make difference to our body?

Re: Study shows space travel is harmful to the brain

#12

Post by gliese1337 »

iwwr wrote: post #9

"While space is full of radiation, the earth's magnetic field generally protects the planet and people in low earth orbit from these particles." The magnetic field protects only against charged particles (usually coming from the Sun). Galactic cosmic rays or solar flares are not blocked. The atmosphere blocks most of that, as well as the planet itself. In low-Earth orbit, you have half the horizon covered by the plan…

  I don't understand why NASA has never built a rotating space habitat to solve this problem.
Because it's difficult to do right. There is a maximum usable RPM beyond which humans cannot function due to dizziness/disorientation, and a somewhat lower max beyond which excessive coriolis effects would make working in the habitat incredibly annoying; generally, you don't want to go about 2rpm, though you could push it by screening your astronauts for spin-adaptability. This puts a lower limit on how large the habitat must be to achieve any particular level of spin gravity; for anything approaching 1g, it's pretty large, and no one knows just how little gravity is required to prevent the physiological effects of microgravity. To get even half a g at 2rpm, you'd need a structure 112 meters in radius, which is pretty dang big for a spacecraft.

You could probably still manage that with current technology if you just have two small spacecraft modules at the ends of a 224m tether (or a somewhat shorter tether if you have some unmanned equipment that's heavier than the crew module and can serve as a counterbalance rotating with a smaller radius), but then you've got a bunch of other problems to deal with. How do you dock with a rotating structure? Safely approaching a rapidly spinning tether in orbit is not an easy task. Then you have to match rotation, unless there's a non-rotating hub, which would result in enormous complications to the structure. How do you move it / do stationkeeping? All thruster burns now have to account for the structure's angular momentum. And stationkeeping will be more of an issue that with 'normal' spacecraft because tidal effects will make a tether in orbit want to wobble. Additionally, there may be electromagnetic drag to deal with, and the associated voltage buildup across the structure that you'll need to find a way to safely discharge.

And then there's space debris. If the cable is damaged, you either get flung off into an unrecoverable orbit, or you hit the atmosphere and burn up.

So, all in all, hardly surprising that NASA hasn't bothered yet.

Re: Study shows space travel is harmful to the brain

#13

Post by Hoff »

iwwr wrote: post #9

"While space is full of radiation, the earth's magnetic field generally protects the planet and people in low earth orbit from these particles." The magnetic field protects only against charged particles (usually coming from the Sun). Galactic cosmic rays or solar flares are not blocked. The atmosphere blocks most of that, as well as the planet itself. In low-Earth orbit, you have half the horizon covered by the plan…

Why no 2001-style rotating orbital station? Probably because it's not easy, it'll be big and heavy, and Big and Heavy and Orbital is definitely not cheap.

Moving mass — people moving around — within a rotating structure will transmit vibrations throughout the structure, even with mass dampening.

As an example of the considerations around vibrations within ISS, astronaut Sunita Williams indicated that the ISS exercise equipment is intentionally isolated from the ISS structure, as the vibrations of the crew members exercising causes problems for the solar arrays.

Source: http://www.youtube.com/watch?v=doN4t5NKW-k

Re: Study shows space travel is harmful to the brain

#14

Post by gliese1337 »

paulovsk wrote: post #11
iwwr wrote: post #9

"While space is full of radiation, the earth's magnetic field generally protects the planet and people in low earth orbit from these particles." The magnetic field protects only against charged particles (usually coming from the Sun). Galactic cosmic rays or solar flares are not blocked. The atmosphere blocks most of that, as well as the planet itself. In low-Earth orbit, you have half the horizon covered by the plan…

How a rotating space would help the problems with lack of gravity? I mean, our gravity is up-down and the acceleration from a rotating environment would be lateral. Doesn't that make difference to our body?

No, it doesn't. "Down" is defined by the direction of acceleration, so saying that the centripetal gravity would be somehow sideways doesn't make sense; your body has no means of telling the difference.

What your body can sense is the presence of coriolis effects.

Re: Study shows space travel is harmful to the brain

#15

Post by paulovsk »

gliese1337 wrote: post #14
paulovsk wrote: post #11

Earlier quoted context omitted.

How a rotating space would help the problems with lack of gravity? I mean, our gravity is up-down and the acceleration from a rotating environment would be lateral. Doesn't that make difference to our body?

No, it doesn't. "Down" is defined by the direction of acceleration, so saying that the centripetal gravity would be somehow sideways doesn't make sense; your body has no means of telling the difference. What your body can sense is the presence of coriolis effects.

Ok, let me rewrite.

The acceleration I feel is in the head-feet direction, so it's relevant for the muscles, since their fibers seems to be aligned in this direction. The centripetal acceleration would be perpendicular to the usual muscular development, so... in this scenario, would that place still work for astronaut's body?

Re: Study shows space travel is harmful to the brain

#16

Post by gliese1337 »

paulovsk wrote: post #15
gliese1337 wrote: post #14

Earlier quoted context omitted.

No, it doesn't. "Down" is defined by the direction of acceleration, so saying that the centripetal gravity would be somehow sideways doesn't make sense; your body has no means of telling the difference. What your body can sense is the presence of coriolis effects.

Ok, let me rewrite. The acceleration I feel is in the head-feet direction, so it's relevant for the muscles, since their fibers seems to be aligned in this direction. The centripetal acceleration would be perpendicular to the usual muscular development, so... in this scenario, would that place still work for astronaut's body?

No, it wouldn't. There is no meaningful way for gravity to be "perpendicular to the usual muscular development". You would orient your head-foot axis to match the direction of the acceleration you feel. Floors and walls in a space habitat would be built in that orientation. Doing otherwise would be just as stupid as lying horizontally on Earth and then complaining that gravity goes the wrong way.

Re: Study shows space travel is harmful to the brain

#18

Post by mkr-hn »

gliese1337 wrote: post #12
iwwr wrote: post #9

"While space is full of radiation, the earth's magnetic field generally protects the planet and people in low earth orbit from these particles." The magnetic field protects only against charged particles (usually coming from the Sun). Galactic cosmic rays or solar flares are not blocked. The atmosphere blocks most of that, as well as the planet itself. In low-Earth orbit, you have half the horizon covered by the plan…

I don't understand why NASA has never built a rotating space habitat to solve this problem. Because it's difficult to do right. There is a maximum usable RPM beyond which humans cannot function due to dizziness/disorientation, and a somewhat lower max beyond which excessive coriolis effects would make working in the habitat incredibly annoying; generally, you don't want to go about 2rpm, though you could push it by s…

How about a giant donut balloon that inflates once in space? NASA could fill it with balls and charge admission while waiting for the expedition's supplies to reach Mars.

Re: Study shows space travel is harmful to the brain

#19

Post by gliese1337 »

mkr-hn wrote: post #18
gliese1337 wrote: post #12

Earlier quoted context omitted.

I don't understand why NASA has never built a rotating space habitat to solve this problem. Because it's difficult to do right. There is a maximum usable RPM beyond which humans cannot function due to dizziness/disorientation, and a somewhat lower max beyond which excessive coriolis effects would make working in the habitat incredibly annoying; generally, you don't want to go about 2rpm, though you could push it by s…

How about a giant donut balloon that inflates once in space? NASA could fill it with balls and charge admission while waiting for the expedition's supplies to reach Mars.

An inflatable torus might be a good way to create a friendly working environment for further construction, but further construction will be required. There're still the issue of docking to worry about, and you get new problems when you allow inhabitants to move around an arc; some active system is required to ensure that, as people and equipment move about, other stuff gets adjusted to ensure that the center of rotation always remains at the center of the torus. Otherwise, it will start to wobble, resulting in different gravity levels around the torus and inducing stretching force along some axis. If the balance is successfully restored (and the station does not tear itself apart) but not quickly enough, then you have vibration damping issues to worry about.

These problems become less severe as you make the structure large and larger (and thus the mass of the inhabitants less significant), but larger structures are of course more difficult and more expensive to construct.

Re: Study shows space travel is harmful to the brain

#20

Post by paulovsk »

gliese1337 wrote: post #16
paulovsk wrote: post #15

Earlier quoted context omitted.

Ok, let me rewrite. The acceleration I feel is in the head-feet direction, so it's relevant for the muscles, since their fibers seems to be aligned in this direction. The centripetal acceleration would be perpendicular to the usual muscular development, so... in this scenario, would that place still work for astronaut's body?

No, it wouldn't. There is no meaningful way for gravity to be "perpendicular to the usual muscular development". You would orient your head-foot axis to match the direction of the acceleration you feel. Floors and walls in a space habitat would be built in that orientation. Doing otherwise would be just as stupid as lying horizontally on Earth and then complaining that gravity goes the wrong way.

Oh, I see. So it was more of a question that I could not observe how this would be built than its effectiveness per se. Thanks for clarifying.

On a side note, they mention one equipment like that in this novel(a hell of a good scifi): The Martian, by Andy Weir. Available for free online, really funny.

Post reply on HN