The first astronauts from the United States were selected in 1959. To this day there are 240 men and women who make up

the NASA astronaut program. Astronaut candidates must go through an extensive and competitive selection process. They must   

complete two years of training before they begin specialized mission training. During their "boot camp" they are taught how to

use the shuttle and space station systems as well as earth sciences, meteorology, space science, and engineering. Once training

is competed, the new astronauts are assigned to work with experienced astronauts. There are two types of astronauts: pilot

astronauts and mission specialists. Pilot astronauts fly the space shuttle and command missions where as mission specialists

conduct spacewalks, work with robotic equipment, and perform scientific research.