The U.S. Space Shuttle is a reusable spacecraft designed to be launched into orbit by rockets and then to return to the Earth's
surface by gliding down and landing on a runway. The Shuttle was selected in the early 1970s as the principal space launcher and carrier vehicle to be developed by the National Aeronautics and Space Administration (NASA). Planned as a replacement for expensive, expendable booster rockets, it would complete NASA's new Space Transportation System (STS). The program finally got under way in the early 1980s.ComponentsThe three main components of the Space Shuttle are the orbiter, external tank, and solid
rocket boosters. The Shuttle weighs 2.0 million kg (4.5 million lb) at launch and stands 56.1 m (184.2 ft)
tall. It can carry up to 29,500 kg (65,000 lb) of cargo on one mission.The orbiter is 23.79 m (78.06 ft) across the wing tips and 37.2 m (122.2 ft) long. During launch it is a rocket stage, in orbit it is a spaceship, and on reentry and landing it is a hypersonic glider. A two-deck crew compartment and an attitude thruster module are in the nose, the midbody is the cargo hold, or payload bay (4.6 m/15 ft wide and 18.3 m/60 ft long), and the tail holds the three main engines plus maneuvering engine pods. Each engine, burning hydrogen and oxygen, produces up to 213,000 kg (470,000 lb) of thrust.The external tankÑan oxygen tank and hydrogen tank joined by a load-bearing intertankÑis the Shuttle's structural backbone. It is 8.38 m (27.56 ft) wide and 47 m (154.2 ft) tall and carries 709,750 kg (1,565,000 lb) of liquefied propellants for the main engines. Two solid rocket boosters, each 3.7 m (12.14 ft) wide and 45.5 m (149.16 ft) tall, are attached. Each produces a thrust of 1.20 million kg (2.65 million lb).