The Space Shuttle program was the fourth human spaceflight program carried out by the U.S. National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its official program name was carried over from the 1969 plan for the Space Transportation System (STS) of reusable spacecraft. Only the shuttle and supporting rockets were funded for development; a proposed nuclear lunar shuttle in the plan was canceled in 1972. It flew 135 missions and carried 355 astronauts from 16 countries, many on multiple trips. The Space Shuttle, composed of an orbiter launched with two reusable solid rocket boosters and a disposable external fuel tank, carried up to eight astronauts and up to 50,000 lb (23,000 kg) of payload into low Earth orbit (LEO). When its mission was complete, the orbiter would reenter the Earth's atmosphere and land like a glider at either the Kennedy Space Center or Edwards Air Force Base. The Shuttle is the only winged crewed spacecraft to have achieved orbit and landing, and the first reusable crewed space vehicle that made multiple flights into orbit. Its missions involved carrying large payloads to various orbits including the International Space Station (ISS), providing crew rotation for the space station, and performing service missions on the Hubble Space Telescope. 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. Original selling points on the shuttles were over 150 launches over a 15-year operational span with a 'launch per month' expected at the peak of the program, but extensive delays in the development of the International Space Station never created such a peak demand for frequent flights.
Background Various shuttle concepts had been explored since the late 1960s. The program formally commenced in 1972, becoming the sole focus of NASA's human spaceflight operations after the Apollo, Skylab, and Apollo–Soyuz programs in 1975. 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. The stalled plans for a U.S. space station evolved into the International Space Station and were formally initiated in 1983 by President Ronald Reagan, but the ISS suffered from long delays, design changes and cost over-runs and forced the service life of the Space Shuttle to be extended several times until 2011 when it was finally retired—serving twice as long as it was originally designed to do. In 2004, according to 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, only five years after the Shuttle program was formally initiated; 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.
Conception and development
Program history
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