A shuttle consists of an Orbiter with the appearance of a delta-wing aircraft, a huge expendable external propellant tank, on which the Orbiter is mounted at launching, and two solid-fuel rocket boosters. The whole system weighs about 2000 tonnes at launch and has an overall length of about 56 meters. The Orbiter is 37 meters in length.
The shuttle is launched in a vertical position by the simultaneous firing of its two rocket boosters and three very powerful liquid hydrogen/liquid oxygen main engines. About two minutes into the flight the empty rocket boosters are detached, parachute into an ocean area, and are recovered for further use. Just before the craft reaches its orbit the propellant tank is discarded and burns up in the atmosphere. The Orbiter can then maneuver by means of two on-board engines. The altitude, eccentricity, and inclination of the orbit can be varied, within limits, as can the flight duration – between about 7 and 30 days. On mission completion the Orbiter uses its rocket motors to put it into a reentry path, enters the atmosphere in a shallow glide, and finally makes an unpowered landing like a conventional glider.
The Orbiter has a large cargo bay – 18.3 meters long and 4.6 meters in diameter – in which the payload is housed. Spacelab first flew in the cargo bay in 1983. Satellites can be launched into orbit from the cargo bay and can also be brought back into the bay for servicing and redeployment or for return to Earth. Since the Challenger disaster, unpiloted boosters such as the Deltas have been used as the main launch vehicles for astronomy missions. But the space shuttle was employed for carrying the Hubble Space Telescope into orbit in 1990 and later for service and repair missions to it. The shuttles are also used for medical, scientific, and technological experiments conducted by the astronauts. A total mass of 29.5 tonnes can be carried into a low-altitude orbit, with smaller loads for higher or less accessible orbits. Payloads to be placed in orbits above the shuttle ceiling, such as a geostationary orbit, require additional propulsion; the shuttle ceiling is about 1000 km in altitude. A payload of 11.5 tonnes can be returned to Earth.
In 1995 a shuttle made the first of several flights to and from the Russian space station Mir, in preparation for the construction and utilization of the International Space Station (ISS). In 1998 shuttles and Russian Soyuz craft embarked upon the process of building the ISS, ferrying components into orbit and transferring personnel to and from the ISS modules as they were assembled. The suspension of shuttle flights after the loss of the Columbia temporarily halted the shuttles' contribution to this activity, but their collaboration in completing the ISS were scheduled to resume when they returned to service.