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Making Gravity: How Do You Steer a Giant, Spinning Spaceship?

NASA's hopes for artificial gravity will rely on solving this problem.
NASA astronaut Christa McAuliffe training in microgravity aboard the "vomit comet." Image: WikiMedia Commons

If there's one big gap between our science fiction view of space travel and our current reality, it's artificial gravity. Every fictional spacecraft from Star Trek to 2001: A Space Odyssey is equipped with some kind of system that simulates Earth-like gravity environments, enabling its occupants to briskly walk (rather than aimlessly float) around the ship. So why are our astronauts still floating?

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In NASA's recently published 2015 version of its technology roadmaps, the agency outlines its goals for finding a way to simulate Earth's gravity while hurtling through the vacuum of space.

"The artificial gravity capability goals are to reduce crew health degradation on long-duration spaceflight missions by providing a partial or full-Earth's gravity environment during the journey to and from a destination, thereby increasing human exploration safety, crew well-being, and productivity," the report states.

Scientists have long studied the effects of dropping an Earth-gravity-grown human into a low or zero gravity environment (and then, more importantly, bringing them back to Earth). The body loses blood volume, and our bones and muscles can atrophy when exposed to microgravity. One of the goals of astronaut Scott Kelly's one-year stay on the ISS is to measure the effects of microgravity at a genetic level by comparing to his twin brother, Mark, who is staying on Earth.

As the agency eyes up much longer-term manned missions, gravity will play a bigger and bigger role. If we start sending astronauts on years-long missions, the sustained exposure to low or zero gravity could have serious physical effects. Finding a way to mimic Earth's gravity, even if only for short stints at a time, is one possible solution.

NASA has had artificial gravity on its radar for decades, but figuring out how to manufacture fake gravity isn't an easy task. One of the most promising technologies, as outlined in the roadmap, is a rotating spacecraft that would create faux gravity through centrifugal force (sort of like those fairground rides that stick you to the wall as they spin). The problem? Trying to figure out how to steer a spacecraft that's constantly spinning.

To address this, NASA is investigating technology that would shift the center of gravity in order to balance the ship, use thrusters to adjust the spacecraft's course, and use this momentum to keep the ship spinning. It's complicated stuff, but that's why we literally have rocket scientists working on it.

Aside from improving astronauts' health when they return to Earth, NASA predicts artificial gravity would "increase crew productivity and well-being while reducing long-term human health and performance risks." The report also notes that since astronauts' physiology wouldn't be reduced during flight if using artificial gravity, then they'd be able to get right to work as soon as they land at their destination, such as Mars.

As with many of the ideas presented in the technology roadmap, NASA has presented a tantalizing view of how we could make our science fiction dreams a reality—and have a tangible, necessary impact on crew health in the process.