Astronaut training is conducted in the JSC's Mission Operations Directorate. Training to be an astronaut is vigorous and requires the efforts of hundreds of people and numerous facilities. Since manned space flight programs have become more sophisticated over the years, the complexity and length of the training process changes to meet the new demands of operating the Space Shuttle.

The training for new candidates consists of a series of short courses in aircraft safety, including instruction in ejection, parachute and survival to prepare them in the event their aircraft is disabled.

In the formal academic areas, the novice astronauts are given lessons on basic science and technical courses, including mathematics, earth resources, meteorology, guidance, navigation, astronomy, physics, and computer sciences.

Knowledge of the Shuttle system is obtained through lectures, briefings, textbooks and flight operations manuals.

As training progresses, the student astronauts gain valuable experience in the single systems trainers (SST). The SST's contain computer databases with software allowing students to interact with controls and displays like those of a Shuttle crew station. They can develop work procedures and react to disastrous situations in a Shuttle-like environment. Other major operations training facilities at JSC include the Computer-Aided Instructional Trainer (CAIT), which fills the gap between textbook lessons and more complex trainers and simulators. The Crew Software Trainer (CST) used to demonstrate orbiter software capabilities before students go on to the SSTs, which then moves the students on to the Shuttle Mission Simulator (SMS). Finally, the Orbiter Crew Compartment Trainer, used to train crew members for most of their on-orbit duties.