The remarkable 27-year career of the space shuttles, Discovery, has come to an end. The orbiter landed at the Kennedy Space Center in Florida on Thursday after a 12-day final mission to the International Space Station. Discovery is destined now to go to a museum. NASA's two other re-usable space planes will follow it into retirement in the coming months. On its final flight, Discovery delivered a new store room and a sophisticated humanoid robot to the International Space Station.