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 mimic Earth’s gravity in space.
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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.
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Why does China want to build a kilometre-long spacecraft? And is it even possible?
“Thinking about the future, Harvey points to a Chinese report published in 2009 called Roadmap 2050, which is the blueprint for how China plans to become the world’s leading space-faring nation by the middle of the century. “The horizon to Chinese spaceflight is not years or decades but half-centuries,” he says.”
“On Episode 188, Bill Paloski, former director of the Human Research Program at NASA’s Johnson Space Center, explores the idea of artificial gravity within a spacecraft for long-duration missions and explains how it may affect the human body from what we have learned through Earth-based studies.”
What happens to bones in space?
“On a long-duration space flight, such as those planned for missions to Mars and beyond, bone loss can be a serious impediment. This loss may not hinder astronauts while they are in orbit, but upon return to Earth, their weakened bones will be fragile and at an increased risk of fractures. At this time, it is unknown whether this bone loss will eventually reach a plateau, or whether it will continue indefinitely.”
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