While in college, future applicants should concentrate their studies in the technology, math, and science fields. An applicant should also make the effort to gain additional experience by interning in a related field. The selection board sends a list of the final candidates to the NASA Administrator. The Administrator makes the decision of who will actually join the program. Every two years, approximately twenty people are chosen to fill vacancies in the astronaut corps.
Astronauts are usually eligible for a flight assignment one year after completion of basic training.
The novice astronauts are trained in aircraft safety which includes ejection, parachute, and survival instruction. A Gulfstream II aircraft, which has been modified to simulate the handling of a Shuttle, is also used to train pilot astronauts. The astronauts are given a range of basic science, math, and technology courses. The astronauts receive training in a mock-up of the Space Shuttle. Each astronaut must also learn to function in weightless environments, and possibly even learn to perform a space walk.