An astronaut is a person who is trained for travelling in a spacecraft. someone who travels and works in a spacecraft (astro- + -naut (as in aeronaut; AERONAUTICS)). 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