When astronauts go on spacewalks, they wear spacesuits to keep themselves safe. Inside spacesuits, astronauts have the oxygen they need to breathe. They have the water they need to drink.
Astronauts put on their spacesuits several hours before a spacewalk. The suits are pressurized. This means that the suits are filled with oxygen.
Once in their suits, astronauts breathe pure oxygen for a few hours. Breathing only oxygen gets rid of all the nitrogen in an astronaut's body. If they didn't get rid of the nitrogen, the astronauts might get gas bubbles in their body when they walked in space. These gas bubbles can cause astronauts to feel pain in their shoulders, elbows, wrists and knees. This pain is called getting "the bends" because it affects the places where the body bends, Scuba divers can also get "the bends."
Astronauts are now ready to get out of their spacecraft. They leave the spacecraft through a special door called an airlock. The airlock has two doors.

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