Jettisoned Space Shuttle fuel tank falling back to Earth. The Space Shuttles are reusable spacecraft flown by NASA since 1981. When the fuel in the external tank is finished, the main engines shut down, the tank is discarded, and the Shuttle's orbital engines are used to finalise its orbit. The Shuttle detaches from the external tank 9 minutes after launch. The tank mostly burns up in the atmosphere, and the remnants fall into the ocean 40 minutes later. This tank was discarded by the Space Shuttle Discovery. Photographed on 4 July 2006, during mission STS-121.