In the microgravity environment there is no such thing as "up," which means it's just as easy to sleep vertically as you would horizontally back home. It's also important to secure your arms (and legs) to avoid them hovering as you sleep.
When we settle into our beds at night, we usually experience a pleasant sense of unburdening. After a long day of walking, sitting, and standing, letting gravity do the work and sinking into a soft mattress can be a relief. But a little more than 200 miles (322 kilometers) above the Earth, astronauts live and work in zero gravity aboard the International Space Station (ISS), and going to sleep in zero gravity presents a much different situation.
The ISS is big -- it takes up about the same footprint as an American football field (including the end zones), and since launch now has more livable space than what you'd find in the average five-bedroom home, including two bathrooms, a gym (while in space, astronauts, on average, exercise for two hours every day in an effort to combat a side effect of life in space: bone and muscle loss), and a 360-degree bay window [source: NASA].
Since it docked in November 2000, the International Space Station has never been empty; in its first decade of operation more than 200 people visited the orbiting laboratory and spaceport, and it always has a permanent crew of six on board [source: NASA, Sample].
Crews on the ISS may live in space for long periods of time -- for example, Expedition 34 lived in space for 144 days -- and the details of each day they spend in space are scheduled beforehand. A typical weekday for the crew of Expedition 18 (the 18th permanent crew of the ISS), for instance, began with a 6 a.m. UTC (UTC is the same as GMT, which is used to reduce time zone confusion among countries) wake-up call, followed by 90 minutes of time for eating breakfast and getting ready for the day. By 7:30 a.m., the crew had conference calls with each country's control center, and embarked on a morning of science experiments, maintenance and small chores. Following an hour for lunch, the crew was back to work, along with more exercise much like the morning routine. With one final planning conference call with each control center, the day wrapped up around 5:30 or 6 p.m., followed by dinner at 8 p.m., and bedtime at 9:30 p.m. [source: Magnus].
After a busy day of exercising, research and maintenance work, the least an astronaut could ask for is a good night's sleep. But even the idea of "night" changes when you're in space, when an orbiter zooms around the Earth multiple times a day. And with the effects of microgravity and weightlessness, even the quality of sleep in space is different from that on Earth.
What's it like for astronauts to sleep in space? Do they just float around without anything to hold them down, or are they attached to something? Is it difficult to sleep in space, or do the effects of low gravity actually make it easier? To learn how astronauts get their Z's in zero gravity, read on.
Spacecraft like the International Space Station have pressurized cabins and are filled with the same kind of air we breathe on Earth, so the atmosphere on board is made to feel as close to sea level as possible. But microgravity causes astronauts to experience the effects of weightlessness, and setting up a mattress on the floor can't be part of the plan because not only would the astronaut float away after dozing off, the mattress itself would also drift off, creating the potential for midair collisions.
Because of this effect, astronauts could, theoretically, sleep almost anywhere in a spacecraft. Astronauts sleeping during space shuttle missions normally strap themselves into seats or attach sleeping bags to the walls; they'll avoid the cockpit since light from the sun can cause the area to heat up significantly and make slumber uncomfortable. Most of the crew on the ISS choose to sleep in their own cabin or in an ISS module -- American crew members' sleeping quarters are well-ventilated (to prevent breathing in the carbon dioxide you just breathed out), soundproof private cabin-for-one setups where an astronaut can not only catch some Z's but also catch up on e-mail. The catch is that they need to tether themselves to something to avoid floating away in the air currents. Most astronauts choose to sleep as closely to how they would on Earth, in sleeping bags tethered to the floor, the walls, or the ceiling. In the microgravity environment there is no such thing as "up," which means it's just as easy to sleep vertically as you would horizontally back home. It's also important to secure your arms (and legs) to avoid them hovering as you sleep.
Adjusting to sleep in space takes a long time for astronauts. Our bodies and brains are used to certain circadian rhythms -- the 24-hour cycle of waking and sleeping -- and disturbing them can cause sleep difficulties.
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