A A space shuttle consists of two rocket boosters, three engines, an external fuel tank and two smaller fuel tanks. It also has an orbiter, which puts the shuttle into orbit. The rockets are used to propel the shuttle into space. When the shuttle is about 45 kilometres (28 miles) high, the rockets fall off into the ocean and the three main engines of the shuttle take over. Just before the shuttle goes into orbit, its engines are shut down and the external fuel tank is discarded.