In the late 1950s, the Air Force began developing the partially reusable X-20 Dyna-Soar. ĭesign and development Historical background ĭuring the 1950s, the United States Air Force proposed using a reusable piloted glider to perform military operations such as reconnaissance, satellite attack, and air-to-ground weapons employment. relied on the Russian Soyuz spacecraft to transport astronauts to the ISS from the last Shuttle flight until the launch of the Crew Dragon Demo-2 mission in May 2020.
The three surviving operational vehicles were retired from service following Atlantis 's final flight on July 21, 2011. A fifth operational (and sixth in total) orbiter, Endeavour, was built in 1991 to replace Challenger. Of these, two were lost in mission accidents: Challenger in 1986 and Columbia in 2003, with a total of 14 astronauts killed. Four fully operational orbiters were initially built: Columbia, Challenger, Discovery, and Atlantis. The first orbiter, Enterprise, was built in 1976 and used in Approach and Landing Tests (ALT), but had no orbital capability.
If the landing occurred at Edwards, the orbiter was flown back to the KSC atop the Shuttle Carrier Aircraft (SCA), a specially modified Boeing 747. The orbiter was protected during reentry by its thermal protection system tiles, and it glided as a spaceplane to a runway landing, usually to the Shuttle Landing Facility at KSC, Florida, or to Rogers Dry Lake in Edwards Air Force Base, California. At the conclusion of the mission, the orbiter fired its OMS to deorbit and reenter the atmosphere. The SRBs were jettisoned before the vehicle reached orbit, while the main engines continued to operate, and the ET was jettisoned after main engine cutoff and just before orbit insertion, which used the orbiter's two Orbital Maneuvering System (OMS) engines. The Space Shuttle was launched vertically, like a conventional rocket, with the two SRBs operating in parallel with the orbiter's three main engines, which were fueled from the ET. Space Shuttle components include 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 fleet's total mission time was 1,323 days. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST), conducted science experiments in orbit, participated in the Shuttle- Mir program with Russia, and participated in construction and servicing of the International Space Station (ISS). Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011, launched from the Kennedy Space Center (KSC) in Florida. The first ( STS-1) of four orbital test flights occurred in 1981, leading to operational flights ( STS-5) beginning in 1982. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft where it was the only item funded for development. National Aeronautics and Space Administration ( NASA) as part of the Space Shuttle program. The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S.
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