The Space Shuttle
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. 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. The first (STS-1) of four orbital test flights occurred in 1981, leading to operational flights (STS-5) beginning in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011. They 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, participated in the Shuttle-Mir program with Russia, and participated in construction and servicing of the International Space Station (ISS). The Space Shuttle fleet's total mission time was 1,323 days.
The Space Shuttle
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 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. 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. At the conclusion of the mission, the orbiter fired its OMS to deorbit and reenter the atmosphere. 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. 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 first orbiter, Enterprise, was built in 1976 and used in Approach and Landing Tests (ALT), but had no orbital capability. Four fully operational orbiters were initially built: Columbia, Challenger, Discovery, and Atlantis. Of these, two were lost in mission accidents: Challenger in 1986 and Columbia in 2003, with a total of 14 astronauts killed. A fifth operational (and sixth in total) orbiter, Endeavour, was built in 1991 to replace Challenger. The three surviving operational vehicles were retired from service following Atlantis's final flight on July 21, 2011. The U.S. 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.
Endeavour successfully completed 25 missions into space, including the first service mission to the Hubble Space Telescope, as well as the first mission to add a U.S. component to the International Space Station.
Built to replace space shuttle Challenger, Endeavour was the final orbiter to join the shuttle fleet. Many newer features were added to Endeavour during construction, such as updated steering mechanisms, upgraded plumbing and electrical connections to allow for longer missions, and a drag chute that reduced wear and tear on the shuttle's brakes and tires. Many of the innovations that were developed for Endeavour were added later to the other shuttles in the fleet.
Another major mission for Endeavour was STS-61, the first service mission to the Hubble Space Telescope, which took place in December 1993. This mission was designed to correct a flaw in the Hubble's main mirror. During the mission, several elements were installed to fix the Hubble's "vision," which the popular media described as giving the Hubble "contact lenses" or "glasses." Without this technically challenging mission to fix the Hubble, we may have never seen some of the beautiful images from space that have made the Hubble famous.
The space shuttle's largest contribution was building the International Space Station, which remains in orbit today to conduct hundreds of science experiments annually on human health, engineering and other matters. The program is also remembered for launching and servicing the Hubble Space Telescope, visiting the Russian space station Mir, launching numerous satellites and probes, and performing thousands upon thousands of hours of basic science experiments.
The solid rocket boosters (SRBs) operated for the first two minutes of flight to provide additional thrust needed to get the shuttle into orbit. About 24 miles (45 kilometers) up, the boosters separated from the external tank and descended on parachutes into the Atlantic Ocean. Ships recovered them, and they were refurbished for reuse.
The orbiter is the component most people think of as "the shuttle." It was the heart and brains of the system and the actual ship that took people to space and brought them back. The orbiter was about the same size as a DC-9 aircraft. It was 122 feet (37 meters) long and had a wingspan of 78 feet (23 m). The crew compartment, located in the forward fuselage, normally carried crews of seven astronauts, but occasionally carried fewer people. The largest crew size for a shuttle mission was eight astronauts.
The mid-fuselage housed a 60-foot (18-meter) payload bay and robotic arm. The bay could hold satellites, modules containing whole laboratories, and construction materials for the International Space Station. The aft fuselage held the orbital maneuvering system, main engines and vertical tail. Smaller thrusters located at the shuttle's nose and aft fuselage were used for small flight adjustments.
The space shuttle grew out of several efforts to develop reusable spacecraft. The X-15 program in the 1950s tested the idea of flying a space plane. The U.S. Air Force also conducted studies on semi-reusable spacecraft in the 1960s. NASA began work on an Integrated Launch and Re-entry Vehicle (ILRV) in 1968, and by 1969 the space shuttle's development received approval from then-President Richard Nixon.
The original vision of the space shuttle program was to develop a vehicle that would launch into space very frequently (several times a month) to deploy and repair satellites as required. The military was also an active participant in the development, and the shuttle's payload bay (which carried equipment into satellites into space) was enlarged in the design phase to accommodate larger military satellites.
Specifically, the National Reconnaissance Office asked that the payload bay be enlarged and that the shuttle eventually run polar missions, which are suitable for satellites to see the entire Earth's surface below. The Air Force constructed a launch pad in Vandenberg, Calif., for polar-orbiting missions, but the idea was abandoned after the Challenger disaster of 1986. Although several shuttle military missions ran in the 1980s, the practice dwindled down and ceased after Challenger's explosion.
These activities greatly lessened (and then ceased) after the Challenger space shuttle explosion of 1986, when it became clear that space shuttles could only launch a few times a year instead of many. There was a concern that the astronauts were doing risky spacewalks. As well, military satellites were gradually moved to single-use rockets, providing more frequent launch opportunities at a lower cost.
What didn't change on space shuttle missions, however, was performing experiments. Over the 30 years of the space shuttle program, some 355 individual cosmonauts and astronauts used the space shuttle for launching, landing or both.. They collectively put in thousands upon thousands of hours of work in space investigating all sorts of science, ranging from human health to engineering to astronomy to animal studies.
The space shuttle flew 11 times to the Russian space station Mir between 1994 and 1998, with seven American astronauts doing extended stays on the space station. This was the first major in-space cooperation between Russia and the United States since the Apollo-Soyuz mission of 1975, when Americans and cosmonauts from the Soviet Union docked for a few brief days in space. After the Soviet Union collapse in 1991, NASA agreed to cooperation with the Russians that began with shuttle-Mir and continued with the International Space Station program.
Perhaps the most famous task that the shuttle undertook was bringing up astronauts, pieces and equipment to build the International Space Station. Completing the space station took 13 years and dozens of shuttle missions; the number of shuttle missions total that docked at the station was 37, or more than one-third of the shuttle's total count of 135 missions.
Besides hundreds of hours of astronaut spacewalks, some of the main components that the space shuttle itself contributed included the European Columbus laboratory, the Harmony node, the Tranquility node, the Japanese Kibo laboratory, solar panels, airlocks and the Canadarm2 robotic arm used for spacecraft berthing. The space shuttle also carried vital equipment needed for the interior, with some examples including exercise equipment, science racks, toilets and of course, fresh food.
NASA subsequently did servicing missions in 1997 (STS-82), 1999 (STS-103) and 2002 (STS-109). The last servicing mission was initially canceled in 2003 following concerns for astronaut safety after the Columbia disaster; since Hubble is on a different orbit from the International Space Station, the crew could not shelter at the station in case the shuttle was damaged.
While the shuttle program was mostly conducted in space, Enterprise was constructed for drop-and-landing tests in 1977, furthering previous NASA and military work on flying-wing space vehicles. Enterprise successfully did a series of rigorous tests, starting with taxi work and culminating in several free flights and touchdowns.. Enterprise was deployed on goodwill tours to several countries, and then became the property of the Smithsonian Institution. It temporarily was displayed at the Stephen F. Udvar-Hazy airport annex of the Smithsonian National Air and Space Museum in Fairfax, Va., and then moved permanently in 2012 to the Intrepid Sea, Air and Space Museum in New York City. 041b061a72