Space Shuttle missions from 1981 to 2011, launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST); conducted science experiments in orbit; and participated in construction and servicing of the International Space Station. The Shuttle fleet's total mission time was 1322 days, 19 hours, 21 minutes and 23 seconds. Shuttle components included the Orbiter Vehicle (OV) with three clustered Rocketdyne RS-25 main engines, a pair of recoverable solid rocket boosters (SRBs), and the expendable external tank (ET) containing liquid hydrogen and liquid oxygen. The Space Shuttle was launched vertically, like
Space Shuttle program launched on September 29, 1988. The longest Shuttle mission was STS-80 lasting 17 days, 15 hours. The final flight of the Space Shuttle program was STS-135 on July 8, 2011. Since the Shuttle's retirement in 2011, many of its original duties are performed by an assortment of government and private vessels. The European ATV Automated Transfer Vehicle supplied the ISS between 2008 and 2015. Classified military missions are being flown by the US Air Force's unmanned space plane, the X-37B. By 2012, cargo to the International Space Station was already being delivered commercially under NASA's Commercial Resupply Services by SpaceX's