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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, @03:21PM (2 children)
>As much as I like what Musk is doing, that BFR is a joke.
Not hardly. It's small in the grand scheme of things, surely, and I believe he's already mentioned that he's planning to do another order of magnitude step up in the future. But trying to build such a huge rocket today *would* be a joke. Because the limiting factor on space travel hasn't been engineering prowess in many decades. The limiting factor is funding, and the BFR is the biggest launch vehicle they could design that has a credible shot at being more cost effective than the current options, for current launch demands. When you're operating on a shoestring budget, you have to build things that will break even quickly. Which means you have to build for current demands, even as you strive to prepare for future ones.
And of course there's the other important detail if you're going to start talking spaceships - BFR, and even BFS specifically are NOT spaceships. They're a launch vehicle whose second stage can also function as a usable spaceship, but they are first and foremost a launch vehicle - something that will probably remain true of every vehicle designed to get from Earth's surface into space for a very long time.
Even once we start building real purpose-built spaceships things like the BFR and its descendants will likely still have a role to play as "longboats" - just as you can't land a ship on the beach, you can't land a spaceship on a planet. But that last step is a doozy on foot...
Of course *way* down the line we may have beanstalks to get to and from the surface, establishing "ports" in freefall, but though those will dwarf even proper spaceships in their size and cost, as well as being extremely dangerous to the entire planet should they ever fail. So perhaps we'll stick to more modest launch options like pinwheels, mass drivers, launch loops, etc. which still require some sort of vehicle capable of surviving the stresses.
(Score: 2) by HiThere on Monday July 08 2019, @05:28PM (1 child)
You don't need beanstalks. Beanstalks are a great idea, but only for planets with gravity significantly weaker than Earth. In our gravity the materials need to be too strong, and only if we develop electrically enhanced bonds would they be able to carry much more than their own weight. (And then what happens in a power failure.) For the moon, Kevlar is strong enough, and we could build one for
Mars, if we had reason to. But even monofilament graphene isn't strong enough in Earth's gravity...and you'd need some way to bond the filaments together...and even braiding would decrease the strength/gram-meter value.
OTOH, building a PinWheel (rotating skyhook) is relatively simple. It doesn't decrease the launch cost quite as much, and you need to balance traffic down against traffic up, but it would be dramatically cheaper than any existing system. You'd need to catch a plane to grab onto one of the arms as it rotated by, and the higher you position the catch position the better. (You don't want to keep making correction to correct for atmospheric friction.) But I think a strong ion-rocket at the center should suffice. Also it's "catastrophic failure modes" are considerably less damaging.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by Immerman on Monday July 08 2019, @11:22PM
You're preaching to the choir here, I'm a huge fan of skyhooks and pinwheels, especially around the major planets (my understanding is that skyhook typically refers to the rotating cable, while pinwheel more often refers to the ultimate full-circle extension of the idea). Not least of all because of the fact that they can act as roughly 100% efficient momentum batteries, absorbing orbital energy from landing vehicles and transferring it to vehicles launched later. Of course that does require that incoming ships be able to reliably and almost perfectly intercept the incredibly fast moving top end of the hook - we're talking docking windows measured in milliseconds if the bottom end is matching speed with the Earth's atmosphere. Some sort of "towing harpoon" would expand that somewhat, as well as dramatically lowering the risk profile, by allowing the final rendevous to be done by a light, easily-accelerated "harpoon" on a substantial tether, rather than the entire ship. It's still gong to be a very narrow intercept window near the fast end of a highly elliptical orbit, but I think it could be done even with modern automated systems, much less those of a few decades from now.
There's also some really interesting skyhook potential around the moon - the combination of its motion around the moon, with the moon's motion around Earth, makes for an incredibly wide range of trajectories it could impart to payloads lifted directly off the surface. Beyond your choice of Mars or Venus using a cable a few thousand km long, without ever exceeding 0.25g - if I remember my calculations correctly (Obviously you'd need some sort of retractable tip for the cable to avoid hitting mountains and the like). Of course it's all but impossible to orbit the moon stably, but you're going to want rockets to "de/recharge" it when payloads aren't balanced in both directions anyway, so it might be feasible. Sadly my calculations sggest that it's not possible to launch to/from Earth gracefully with anything that matches speed with the lunar surface. Though the moon would also be a great place for a beanstalk (they're actually possible through the L1 and L2 points, though nowhere else), which is probably violently incompatible with skyhooks.
I think I would avoid having a hub altogether - the spinning cable will be a substantial navigation hazard when getting anywhere near it, while the tips are already traffic central. Have "tip stations" instead - perhaps not right at the tips, but close enough for fuel transfer elevators, etc. to be feasible. You put the (ion?) rockets near the tips, and then you can alter both it's orbital speed and rotation speed depending on when the rockets fire - fire constantly as it spins and there will be no net orbital change (aside from some precession and timing adjustments maybe), but plenty of spin change. Keep reversing direction halfway through the spin and you'll get no net spin change, but can apply all sorts of orbital tweaks. Or any combination thereof.