Before revision: In outer space STS-103 closing the airlock Airlocks are used in outer space, especially during human spaceflight, to maintain the internal habitable environment on spacecraft and space stations when persons are exiting or entering the spacecraft.
After revision: Outer space STS-103 closing the airlock Airlocks are used in outer space, especially during human spaceflight, to maintain the internal habitable environment on spacecraft and space stations when persons are exiting or entering the spacecraft.