How Astronauts Sleep in Space

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 onboard is made to feel as close to sea level as possible. But microgravity causes astronauts to experience the effects of weightlessness, so setting up a mattress on the floor isn't quite a part of the plan -- not only would the astronaut float away after dozing off, but the mattress would also drift off, creating the potential for midair collisions.

Astronaut Sally Ride, the first American woman in space, is shown zipped up in her sleep restraint during flight aboard the Space Shuttle Challenger II.
Time Life Pictures/NASA/Getty Images
Astronaut Sally Ride, the first American woman in space, is shown zipped up in her sleep restraint during flight aboard the Space Shuttle
Challenger II.
This means that astronauts can sleep practically anywhere in a spacecraft, as long as they tether themselves to something: the floor, the walls or the ceiling. While some astronauts, such as Canada's first astronaut Marc Garneau, prefer to sleep "free floating," which simply consists of curling up and going to sleep, most others use sleeping bags to mimic the way we sleep on Earth. A free floater would bounce around and flail his or her limbs around, so a sleeping bag keeps everything nice, cozy and normal.

Astronauts sleeping during space shuttle missions normally strap themselves into seats or attach sleeping bags to the walls, and they'll avoid the cockpit since light from the sun can cause the area to heat up significantly and make slumber uncomfortable. ISS astronauts, on the other hand, have personal sleeping compartments in the Russian Zvezda Service Module, the current living quarters for the crew. Tiny closets are set into the 43 foot (13.1 meter) long module, where astronauts hang a sleeping bag and keep a pillow, light source, air vent and any personal belongings like books or family photos with them. Pillows, of course, need to be strapped to astronauts' heads during sleep so they don't float away.

There are only two compartments on the Zvezda, so when three astronauts are onboard, someone has to stake out a personal space elsewhere throughout the ISS. For example, Susan Helms slept on the opposite side of the ISS in the U.S. Destiny Laboratory Module during her stay.

Adjusting to sleep in space takes a long time for astronauts. After thousands of years of evolution on Earth, our bodies and brains are used to circadian rhythms, the 24-hour cycle of waking and sleeping. To learn how astronauts adapt to sleeping in space and read about some of the difficulties they can experience, see the next page.