A space shuttle is a type of spacecraft designed to transport astronauts and cargo to and from space. It consists of three main parts: the orbiter, which carries the crew; the solid rocket boosters, which provide the initial thrust for launch; and the external tank, which holds fuel for the main engines. Space shuttles were primarily used by NASA from 1981 to 2011. The most famous space shuttle program was the Space Shuttle Program, which completed 135 missions. Notable missions included deploying satellites, servicing the Hubble Space Telescope, and constructing the International Space Station. The program helped advance space exploration and technology.