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Artificial gravity breaks free from science fiction
Artificial gravity has long been the stuff of science fiction. Picture the wheel-shaped ships from films like 2001: A Space Odyssey and The Martian, imaginary craft that generate their own gravity by spinning around in space.
Now, a team from CU Boulder is working to make those out-there technologies a reality.
The researchers, led by aerospace engineer Torin Clark, can't mimic those Hollywood creations—yet. But they are imagining new ways to design revolving systems that might fit within a room of future space stations and even moon bases. Astronauts could crawl into these rooms for just a few hours a day to get their daily doses of gravity. Think spa treatments, but for the effects of weightlessness.
[...]"Astronauts experience bone loss, muscle loss, cardiovascular deconditioning and more in space. Today, there are a series of piecemeal countermeasures to overcome these issues," said Clark, an assistant professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences. "But artificial gravity is great because it can overcome all of them at once."
[...] In a series of recent studies, [they] set out to investigate whether queasiness is really the price of admission for artificial gravity. In other words, could astronauts train their bodies to tolerate the strain that comes from being spun around in circles like hamsters in a wheel?
The team began by recruiting a group of volunteers and tested them on the centrifuge across 10 sessions.
But unlike most earlier studies, the CU Boulder researchers took things slow. They first spun their subjects at just one rotation per minute, and only increased the speed once each recruit was no longer experiencing the cross-coupled illusion.
[...]The personalized approach worked. By the end of 10th session, the study subjects were all spinning comfortably, without feeling any illusion, at an average speed of about 17 rotations per minute. That's much faster than any previous research had been able to achieve. The group reported its results in June in the Journal of Vestibular Research.
Clark says that the study makes a strong case that artificial gravity could be a realistic option for the future of space travel.
"As far as we can tell, essentially anyone can adapt to this stimulus," he said.
(Score: 2) by Immerman on Monday July 08 2019, @03:46PM (3 children)
Let me be the one to poke holes this time: angular momentum is conserved, so as you play out the cable your rate of spin slows, and alternately, reeling in the cable causes your rate of spin to increase. Just as when an ice skater pulls in their arms to go from a slow spin into a fast tight one, and then extend them again to slow down so they can recover gracefully.
For something like a pendulum, where most of the mass is at a point far from the center of rotation, the moment of inertia (rotational analog to inertial mass) is given by I=m*r^2, while angular momentum is L*w (where w=angular frequency in radians per second). So halving the length of the cable causes you to spin 4x as fast in order to maintain constant angular momentum. That's going to get nauseating...
Also, centripetal acceleration = w^2*r, so if you started at 1g acceleration, then halved the cable length, that would increase by a factor of 2^2*1/2 = 2, to 2g. Assuming you've got a lot of halvings to go before you're fully reeled in that';s not going to just nauseate you, it's going to liquefy you.
Fortunately, slowing down the spin isn't actually that hard - just use ion drives or similar for a long slow deceleration with plenty of time to correct for any instabilities. It's only when completely stopped that instabilities become a major problem
(Score: 2) by deimtee on Monday July 08 2019, @05:06PM (2 children)
Runaway's idea could work if you kept a flywheel module at the hub to temporarily 'bank' your angular momentum. Might save some fuel on the spin-up/spin-down cycles if you anticipate having to reel the halves in and out a lot for some reason.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by Immerman on Monday July 08 2019, @11:30PM (1 child)
My argument was mainly against his "reel them in, *then* slow them down" - that's a recipe for liquefication. If you do both at the same time it's not a problem, but you're back to having to balance the dynamic instabilities which I don't think is actually a problem except as you approach zero rotation. So perhaps it would be a good final stage of the maneuver. (or alternately, one space ship lets go while the other reels in the cable)
I don't think a central flywheel would work well though - you're trying to transmit torque crosswise down a cable. It's going to want to wind the cable around the hub rather than change the speed of the ships on the ends. Which might have some really interesting potential, but I wouldn't want to be the one to test it.
(Score: 2) by deimtee on Tuesday July 09 2019, @04:17AM
You could do it with a small rigid section in the middle. Depending on how fast you want to reel them in, it could be fairly short. You just need to move the line of the cable off the line to the centre of mass.
TBH I think it is unlikely really. You can almost always make use of some delta V to get where you are going faster, and arranging the direction of thrust to both accelerate your ship and to either spin up or spin down is pretty trivial really. I mean, it's rocket science, but it's not difficult rocket science.
If you cough while drinking cheap red wine it really cleans out your sinuses.