Zero gravity, changing sunrise patterns, motion sickness and homesickness affect astronauts' health when they are in space. Their pre-mission training helps them cope.
Astronauts need to exercise for two hours every day to avoid the deterioration of bone and muscle in zero gravity. A stationary bicycle or treadmill is provided in the spacecraft.
An astronaut's on-mission diet includes tasty and nutritious ready-to-eat space foods. The meals are light, fresh, and rehydrating.
Astronauts use eye masks and earplugs to block light and sound. Astronauts strap themselves into sleeping bags attached to a seat or wall to avoid bumping into things. They sleep for about eight hours.
Astronauts spit their toothpaste into a towel and take sponge baths in space. Their shampoo does not need rinsing. Instead of a flush, toilets have fans to suck air and urine into a wastewater tank.
Oxygen generation is part of the Environmental Control and Life Support System (ECLSS). The optimal level of oxygen is continuously maintained in the cabin.