Humans Might Need Artificial Gravity for Space Travel

Missions that will return humans to the moon or send them on extended journeys to Mars are looming in the not-too-distant future, which means astronauts could be spending months or years in microgravity. Despite the fact that floating around in space looks like a certified blast, it’s not something the human body is optimized for. In order to make these trips possible, scientists are going to have to figure out how to take Earth’s gravity into space. We evolved with gravity constantly pulling on us at a rate of about 9.8 m/s2, or 1 g. Our bodies are built in a way that takes that into account. Our rigid bones can hold us up, our cardiovascular system can pump blood to and from our extremities, our vestibular system in our ears keeps us balanced, and so on. Our bodies are also good at adapting to our needs, which means when you take gravity away the body starts to change. Bones lose mineral density, hearts weaken, and the vestibular system shuts off because suddenly there is no “up” anymore. So long as the body stays in space these changes aren’t really a problem, but coming back to Earth and readapting to 1 g can be painful and disorienting. To make the transition to Earth easier, astronauts on the ISS have to spend two and a half hours every day doing aerobic and resistive exercise. It takes a lot of valuable time and still doesn’t prevent all bodily changes, so maybe some sort of artificial gravity could be a better solution. The only practical way to recreate the effects of gravity would be by using centrifugal force, aka spinning. If you’ve ever clung for dear life to one of those whirligigs on a playground you know what I’m talking about. If astronauts could somehow be spun around that might mimic gravity enough to keep their bodies from changing too drastically. There have actually been several proposals on how to leverage centrifugal force, and each of them has its downsides. One of them is a staple of sci-fi: a spacecraft with a gigantic rotating section. Inside the astronauts would be pushed towards the outermost wall and that would become the “floor”, so to speak, while the rest of the station would remain stationary and in microgravity. But a spacecraft like this would be really complex and expensive to build. Another design is a long spacecraft that twirls like a baton, creating Earth-like acceleration at either end. If the craft were about a kilometer long it would only need to rotate once or twice a minute, but a kilometer-long spacecraft would be about 10 times longer than the ISS and an incredible engineering feat. It would also make steering and spacewalks really complex. And both these designs would sacrifice precious internal volume. Ironically in space, space is at a premium, but one upside of microgravity is every cubic meter can be utilized. Walls, floors, ceilings, it makes no difference. Every nook and cranny can be used as storage or a workstation or a sleeping area. But make the room spin and suddenly all that volume above the astronaut’s head isn’t as accessible. When you factor in cost, complexity, and usable space, a rotating craft becomes more trouble than it’s worth. The most likely solution is a small-scale centrifuge big enough for just one person that spins very fast. It could generate 1 g at the heart, while the feet would experience more acceleration because of its small size and high speed. Astronauts couldn’t use it 24/7, but maybe a few hours in the centrifuge combined with exercise could be enough. It’s also possible that living with the gravity on Mars or the Moon could keep bodily systems robust enough to transition back to Earth’s gravity. Unfortunately, we just haven’t been able to test many of the variables yet. Studying how to best implement artificial gravity up in space just hasn’t been a priority. A small centrifuge was proposed for the ISS years ago but preparing the station for the device’s vibrations carried too high a price tag. An experiment with rodents in a smaller centrifuge was also proposed when the ISS was new but it was ultimately canceled. With the Moon and Mars beckoning, space agencies are going to have to start testing these personal-scale centrifuges in space soon. It may be a vital part of making humans a multiplanetary species for good. Hey thanks for watching, if you like this episode and want to learn more about the future of space exploration, you should check out our other channel Seeker+. We just did a 3-part series on the ISS and I actually interviewed a couple of astronauts aboard the station and asked them grand philosophical questions and one really immature one. But that one was suggested by you guys. If you’re gonna check it out, say “space toilet” in the comments. Thanks for watching and I’ll see you next time on Seeker!

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