NASA's Space Shuttle Program, officially called the Space Transportation System (STS), was the United States government's manned launch vehicle program from 1981 to 2011, with the program officially beginning in 1972.
History and DescriptionEdit
The winged Space Shuttle orbiter was launched vertically, usually carrying four to seven astronauts (although two and eight have been carried) and up to 50,000 lb (22,700 kg) of payload into low Earth orbit (LEO). When its mission was complete, the Shuttle could independently move itself out of orbit using its Orbital Maneuvering System (it oriented itself heads down and tail first, firing its OMS engines, thus slowing it down) and re-enter the Earth's atmosphere. During descent and landing the orbiter acted as a re-entry vehicle and a glider, using its RCS system and flight control surfaces to maintain altitude until it made an unpowered landing at either Kennedy Space Center or Edwards Air Force Base. The Shuttle is the only winged manned spacecraft to have achieved orbit and land, and the only reusable manned space vehicle that has ever made multiple flights into orbit (the Russian shuttle Buran was very similar and had the same capabilities but made only one unmanned spaceflight before it was cancelled). Its missions involved carrying large payloads to various orbits (including segments to be added to the International Space Station), providing crew rotation for the International Space Station, and performing service missions. The orbiter also recovered satellites and other payloads (e.g. from the ISS) from orbit and returned them to Earth, though its use in this capacity was rare. Each vehicle was designed with a projected lifespan of 100 launches, or 10 years' operational life. The program formally commenced in 1972, although the concept had been explored since the late 1960s, and was the sole focus of NASA's manned operations after the final Apollo and Skylab flights in the mid-1970s. The Shuttle was originally conceived of and presented to the public in 1972 as a 'Space Truck' which would, among other things, be used to build a United States space station in low Earth orbit during the 1980s and then be replaced by a new vehicle by the early 1990s. When the concept of the U.S. space station evolved into that of the International Space Station, which suffered from long delays and design changes before it could be completed, the service life of the Space Shuttle was extended several times until 2011 when it was finally retired — serving at least 15 years longer than it was originally designed to do. In 2004, according to the President George W. Bush's Vision for Space Exploration, use of the Space Shuttle was to be focused almost exclusively on completing assembly of the ISS, which was far behind schedule at that point. The first experimental orbiter "Enterprise" was a high-altitude glider, launched from the back of a specially modified Boeing 747, only for initial atmospheric landing tests (ALT). Enterprise's first test flight was on February 18, 1977; leading to the launch of the first space-worthy shuttle Columbia on April 12, 1981 on STS-1. The Space Shuttle program finished with its last mission, STS-135 flown by Atlantis, in July 2011, retiring the final Shuttle in the fleet. The Space Shuttle program formally ended on August 31, 2011. Retirement of the Shuttle - the most complex vehicle ever built - ended the era in which all of America's varied space activities were performed by one craft -or even one organization. Functions performed by the Shuttle for 30 years will be done by not one but many different spacecraft currently flying or in advanced development. Secret military missions are being flown by the US Air Force's "highly successful" unmanned mini-space plane, the X-37B. By 2012, cargo supply to the International Space Station began to be flown by privately owned commercial craft under NASA's Commercial Resupply Services by SpaceX's successfully tested and partially reusable Dragon spacecraft, followed by Orbital Sciences' Cygnus spacecraft in late 2013. Crew service to the ISS will be flown exclusively by the Russian Soyuz while NASA works on the Commercial Crew Development program. For missions beyond low Earth orbit, NASA is building the Space Launch System and the Orion spacecraft.