Person trained to pilot a spacecraft , operate any of its systems, or conduct research aboard it during spaceflights.
The term commonly refers to those participating in U.S. space missions; cosmonaut is the Russian equivalent. Extensive training, including classroom study of technical subjects as well as practice in computer-controlled simulators and full-sized mock-ups of spacecraft to experience free fall , prepares astronauts physically and psychologically for space missions. Astronauts also learn to use the control, communication, and life-support systems of any given spacecraft and conduct difficult flight operations. See also Edwin Aldrin ; Neil Armstrong ; Guion S. Bluford, Jr. ; Yury A. Gagarin ; John H. Glenn, Jr. ; Mae Jemison ; Sally Ride ; Alan B. Shepard, Jr. ; Valentina Tereshkova .