What Is a Spacewalk?
Anytime an astronaut gets out of a space vehicle, it is called an extravehicular activity, or EVA. This is also called a spacewalk.
Russian astronaut Alexei Leonov performed the first spacewalk on March 18, 1965. The first spacewalk was 10 minutes long.
Astronaut Ed White performed the first American spacewalk during the Gemini 4 mission on June 3, 1965. White's spacewalk lasted 23 minutes.
Today, spacewalks are done outside the International Space Station. Spacewalks usually last between five and eight hours, depending on the job.
The world record for the most spacewalks is held by Russian astronaut Anatoly Solovyev, with a total of 16 EVAs and more than 82 hours outside in space. NASA astronaut Michael López-Alegría holds the U.S. record with 10 spacewalks totaling more than 67 hours.
Why Do Astronauts Go on Spacewalks?
Astronauts go on spacewalks for many reasons. Spacewalks allow astronauts to work outside their spacecraft while still in space. One job astronauts do on a spacewalk is science experiments. Experiments can be attached to the outside of a spacecraft to see how the space environment affects different things. Astronauts place the experiments outside their spacecraft during a spacewalk. They go back outside to get the experiments when the tests are over.
Astronauts also can test new equipment and make repairs to satellites or to their spacecraft while in orbit. By going on spacewalks, astronauts can repair equipment that might otherwise have to be brought back to Earth for repair.
How Do Astronauts Go on Spacewalks?
When astronauts go on spacewalks, they wear spacesuits. Spacesuits protect spacewalkers from the harsh environment of space. They protect astronauts from extreme hot and cold temperatures, harmful space dust and radiation. Spacesuits also give astronauts oxygen to breathe and water to drink during spacewalks.
Astronauts don, or put on, their spacesuits several hours before a spacewalk. The suits are pressurized. This means that the suits are filled with oxygen. Spacesuits are pressurized to keep the fluids in the body in a liquid state.
Once in their suits, astronauts breathe 100 percent oxygen for several hours until all the nitrogen is out of their bodies. Nitrogen in the body during a spacewalk can cause gas bubbles to form in the body. These gas bubbles can cause astronauts to feel pain in their joints, such as their shoulders, elbows, wrists and knees. This condition is called "the bends" because it affects the places where the body bends. The same condition can affect divers who use oxygen tanks to breathe underwater.
Astronauts are now ready to exit their spacecraft. They leave the spacecraft through a special door called an airlock. The airlock has two doors. When astronauts are inside the spacecraft, the airlock is airtight so no air can get out. When astronauts get ready to go on a spacewalk, they go through the first door and lock it tight behind them. They can then open the second door without any air escaping from the spacecraft. After a spacewalk, astronauts go back inside through the airlock. When an astronaut takes off a spacesuit, it is called doffing.
Astronauts use handrails on the space station to help them move from place to place. Sometimes a large robotic arm is used to move astronauts on spacewalks. Astronauts are attached to the robotic arm using a foot restraint.
How Do Astronauts Stay Safe During Spacewalks?
When on a spacewalk, astronauts use safety tethers to attach themselves to their spacecraft. Tethers are like ropes. One end is attached to the spacewalker. The other end is connected to the vehicle. The safety tethers keep astronauts from floating away into space. Astronauts also use tethers to keep tools from floating away. They tether their tools to their spacesuits.
Another way astronauts stay safe during spacewalks is by wearing a SAFER. SAFER stands for Simplified Aid for EVA Rescue. SAFER is worn like a backpack. It uses small jet thrusters to let an astronaut move around in space. If an astronaut were to become untethered and float away, SAFER would help him or her fly back to the spacecraft. Astronauts control SAFER with a small joystick.
How Do Astronauts Train for Spacewalks?
One way astronauts train for spacewalks is by going for a swim. Floating in space is a lot like floating in water. Astronauts practice spacewalks underwater in a large swimming pool near NASA's Johnson Space Center in Houston, Texas.
The pool is called the Neutral Buoyancy Laboratory, or NBL. It holds 6.2 million gallons of water. For every one hour that astronauts will spend spacewalking, they must train for seven hours in the NBL.
Another way astronauts practice for a spacewalk is by using virtual reality. Astronauts wear a helmet with a video screen inside and special gloves. A video of the simulation is shown on the screen inside the helmet. The special gloves allow astronauts' movements to be shown with the video. The virtual reality simulation looks and feels just like a spacewalk.
Original Article: http://www.nasa.gov/audience/forstudents/5-8/features/what-is-a-spacewalk-58.html