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The Space Shuttle is a retired, partially reusable
low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...
al spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the
Space Shuttle program 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 ...
. 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 STS-5 was the fifth NASA Space Shuttle mission and the fifth flight of the Space Shuttle ''Columbia''. It launched on November 11, 1982, and landed five days later on November 16, 1982. STS-5 was the first Space Shuttle mission to deploy comm ...
) 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 The John F. Kennedy Space Center (KSC, originally known as the NASA Launch Operations Center), located on Merritt Island, Florida, is one of the National Aeronautics and Space Administration's (NASA) ten field centers. Since December 1968 ...
(KSC) in
Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
. Operational missions launched numerous
satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
s, interplanetary probes, and the
Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...
(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 The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
(ISS). The Space Shuttle fleet's total mission time was 1,323 days. Space Shuttle components include the Orbiter Vehicle (OV) with three clustered
Rocketdyne Rocketdyne was an American rocket engine design and production company headquartered in Canoga Park, in the western San Fernando Valley of suburban Los Angeles, in southern California. The Rocketdyne Division was founded by North American Avia ...
RS-25 The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is currently used on the Space Launch System (SLS). Designed and manufactu ...
main engines, a pair of recoverable
solid rocket boosters A solid rocket booster (SRB) is a large solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and space shuttle, have used SRBs to giv ...
(SRBs), and the expendable
external tank The Space Shuttle external tank (ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplied the fuel and oxidizer under pressure to ...
(ET) containing
liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33  K. However, for it to be in a fully l ...
and
liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an app ...
. 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 Orbit insertion is the spaceflight operation of adjusting a spacecraft’s momentum, in particular to allow for entry into a stable orbit around a planet, moon, or other celestial body. This maneuver involves either deceleration from a speed ...
, which used the orbiter's two
Orbital Maneuvering System In spaceflight, an orbital maneuver (otherwise known as a burn) is the use of propulsion systems to change the orbit of a spacecraft. For spacecraft far from Earth (for example those in orbits around the Sun) an orbital maneuver is called a ' ...
(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 Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the entr ...
tiles, and it
glided Gliding is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word ''soaring'' is a ...
as a
spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes te ...
to a runway landing, usually to the
Shuttle Landing Facility The Shuttle Landing Facility (SLF) also known as Launch and Landing Facility (LLF) is an airport located on Merritt Island in Brevard County, Florida, United States. It is a part of the Kennedy Space Center and was used by Space Shuttle for ...
at KSC, Florida, or to
Rogers Dry Lake Rogers Dry Lake is an endorheic desert salt pan in the Mojave Desert of Kern County, California. The lake derives its name from the Anglicization from the Spanish name, Rodriguez Dry Lake. It is the central part of Edwards Air Force Base as its ...
in Edwards Air Force Base,
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
. If the landing occurred at Edwards, the orbiter was flown back to the KSC atop the
Shuttle Carrier Aircraft The Shuttle Carrier Aircraft (SCA) are two extensively modified Boeing 747 airliners that NASA used to transport Space Shuttle orbiters. One (N905NA) is a 747-100 model, while the other (N911NA) is a short range 747-100SR. The SCAs were used ...
(SCA), a specially modified Boeing 747. The first orbiter, ''
Enterprise Enterprise (or the archaic spelling Enterprize) may refer to: Business and economics Brands and enterprises * Enterprise GP Holdings, an energy holding company * Enterprise plc, a UK civil engineering and maintenance company * Enterpris ...
'', 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 Discovery may refer to: * Discovery (observation), observing or finding something unknown * Discovery (fiction), a character's learning something unknown * Discovery (law), a process in courts of law relating to evidence Discovery, The Discover ...
'', and ''
Atlantis Atlantis ( grc, Ἀτλαντὶς νῆσος, , island of Atlas) is a fictional island mentioned in an allegory on the hubris of nations in Plato's works '' Timaeus'' and '' Critias'', wherein it represents the antagonist naval power that b ...
''. 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 Soyuz () is a series of spacecraft which has been in service since the 1960s, having made more than 140 flights. It was designed for the Soviet space program by the Korolev Design Bureau (now Energia). The Soyuz succeeded the Voskhod spacecraf ...
to transport astronauts to the ISS from the last Shuttle flight until the launch of the
Crew Dragon Demo-2 Crew Dragon Demo-2 (officially Crew Demo-2, SpaceX Demo-2, or Demonstration Mission-2) was the first crewed test flight of the Crew Dragon spacecraft. The spacecraft, named '' Endeavour'', launched on 30 May 2020 on a Falcon 9 booster, and ca ...
mission in May 2020.


Design and development


Historical background

During the 1950s, the
United States Air Force The United States Air Force (USAF) is the Aerial warfare, air military branch, service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part ...
proposed using a reusable piloted glider to perform military operations such as reconnaissance, satellite attack, and air-to-ground weapons employment. In the late 1950s, the Air Force began developing the partially reusable
X-20 Dyna-Soar The Boeing X-20 Dyna-Soar ("Dynamic Soarer") was a United States Air Force (USAF) program to develop a spaceplane that could be used for a variety of military missions, including aerial reconnaissance, bombing, space rescue, satellite maintena ...
. The Air Force collaborated with
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
on the Dyna-Soar and began training six pilots in June 1961. The rising costs of development and the prioritization of Project Gemini led to the cancellation of the Dyna-Soar program in December 1963. In addition to the Dyna-Soar, the Air Force had conducted a study in 1957 to test the feasibility of reusable boosters. This became the basis for the
aerospaceplane The US Air Force's Aerospaceplane was a basic research project led by Weldon Worth at the Wright-Patterson AFB concerning the design of future recoverable spaceplanes. The effort was started in 1957 as a result of the USAF official SR-89774 ("SR ...
, a fully reusable spacecraft that was never developed beyond the initial design phase in 1962–1963. Beginning in the early 1950s, NASA and the Air Force collaborated on developing
lifting bodies A lifting body is a fixed-wing aircraft or spacecraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage ...
to test aircraft that primarily generated lift from their fuselages instead of wings, and tested the
NASA M2-F1 The NASA M2-F1 was a lightweight, unpowered prototype aircraft, developed to flight-test the wingless lifting body concept. Its unusual appearance earned it the nickname "flying bathtub" and was designated the M2-F1, the M referring to "manned", ...
,
Northrop M2-F2 The Northrop M2-F2 was a heavyweight lifting body based on studies at NASA's Ames and Langley research centers and built by the Northrop Corporation in 1966. Development The success of Dryden's M2-F1 program led to NASA's development and cons ...
, Northrop M2-F3,
Northrop HL-10 The Northrop HL-10 was one of five US heavyweight lifting body designs flown at NASA's Flight Research Center (FRC—later Dryden Flight Research Center) in Edwards, California, from July 1966 to November 1975 to study and validate the concept of ...
,
Martin Marietta X-24A The Martin Marietta X-24 was an American experimental aircraft developed from a joint United States Air Force-NASA program named PILOT (1963–1975). It was designed and built to test lifting body concepts, experimenting with the concept of u ...
, and the
Martin Marietta X-24B Martin may refer to: Places * Martin City (disambiguation) * Martin County (disambiguation) * Martin Township (disambiguation) Antarctica * Martin Peninsula, Marie Byrd Land * Port Martin, Adelie Land * Point Martin, South Orkney Islands Austr ...
. The program tested aerodynamic characteristics that would later be incorporated in design of the Space Shuttle, including unpowered landing from a high altitude and speed.


Design process

On September 24, 1966, NASA and the Air Force released a joint study concluding that a new vehicle was required to satisfy their respective future demands and that a partially reusable system would be the most cost-effective solution. The head of the NASA Office of Manned Space Flight, George Mueller, announced the plan for a reusable shuttle on August 10, 1968. NASA issued a request for proposal (RFP) for designs of the Integrated Launch and Re-entry Vehicle (ILRV), which would later become the Space Shuttle. Rather than award a contract based upon initial proposals, NASA announced a phased approach for the Space Shuttle contracting and development; Phase A was a request for studies completed by competing aerospace companies, Phase B was a competition between two contractors for a specific contract, Phase C involved designing the details of the spacecraft components, and Phase D was the production of the spacecraft. In December 1968, NASA created the Space Shuttle Task Group to determine the optimal design for a reusable spacecraft, and issued study contracts to General Dynamics, Lockheed,
McDonnell Douglas McDonnell Douglas was a major American aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own merger with Boeing in 1997, it pro ...
, and
North American Rockwell North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F- ...
. In July 1969, the Space Shuttle Task Group issued a report that determined the Shuttle would support short-duration crewed missions and space station, as well as the capabilities to launch, service, and retrieve satellites. The report also created three classes of a future reusable shuttle: Class I would have a reusable orbiter mounted on expendable boosters, Class II would use multiple expendable rocket engines and a single propellant tank (stage-and-a-half), and Class III would have both a reusable orbiter and a reusable booster. In September 1969, the Space Task Group, under the leadership of Vice President
Spiro Agnew Spiro Theodore Agnew (November 9, 1918 – September 17, 1996) was the 39th vice president of the United States, serving from 1969 until his resignation in 1973. He is the second vice president to resign the position, the other being John ...
, issued a report calling for the development of a space shuttle to bring people and cargo to low Earth orbit (LEO), as well as a
space tug ''Space Tug'' is a young adult science fiction novel by author Murray Leinster. It was published in 1953 by Shasta Publishers in an edition of 5,000 copies. It is the second novel in the author's Joe Kenmore series. Groff Conklin gave it a mixed ...
for transfers between orbits and the Moon, and a reusable nuclear upper stage for deep space travel. After the release of the Space Shuttle Task Group report, many aerospace engineers favored the Class III, fully reusable design because of perceived savings in hardware costs.
Max Faget Maxime Allen "Max" Faget (pronounced ''fah-ZHAY''; August 26, 1921 – October 9, 2004) was a Belizean-born American mechanical engineer. Faget was the designer of the Mercury spacecraft, and contributed to the later Gemini and Apollo spac ...
, a NASA engineer who had worked to design the Mercury capsule, patented a design for a two-stage fully recoverable system with a straight-winged orbiter mounted on a larger straight-winged booster. The Air Force Flight Dynamics Laboratory argued that a straight-wing design would not be able to withstand the high thermal and aerodynamic stresses during reentry, and would not provide the required cross-range capability. Additionally, the Air Force required a larger payload capacity than Faget's design allowed. In January 1971, NASA and Air Force leadership decided that a reusable delta-wing orbiter mounted on an expendable propellant tank would be the optimal design for the Space Shuttle. After they established the need for a reusable, heavy-lift spacecraft, NASA and the Air Force determined the design requirements of their respective services. The Air Force expected to use the Space Shuttle to launch large satellites, and required it to be capable of lifting to an eastward LEO or into a
polar orbit A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of about ...
. The satellite designs also required that the Space Shuttle have a payload bay. NASA evaluated the F-1 and J-2 engines from the Saturn rockets, and determined that they were insufficient for the requirements of the Space Shuttle; in July 1971, it issued a contract to
Rocketdyne Rocketdyne was an American rocket engine design and production company headquartered in Canoga Park, in the western San Fernando Valley of suburban Los Angeles, in southern California. The Rocketdyne Division was founded by North American Avia ...
to begin development on the
RS-25 The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is currently used on the Space Launch System (SLS). Designed and manufactu ...
engine. NASA reviewed 29 potential designs for the Space Shuttle and determined that a design with two side boosters should be used, and the boosters should be reusable to reduce costs. NASA and the Air Force elected to use solid-propellant boosters because of the lower costs and the ease of refurbishing them for reuse after they landed in the ocean. In January 1972, President
Richard Nixon Richard Milhous Nixon (January 9, 1913April 22, 1994) was the 37th president of the United States, serving from 1969 to 1974. A member of the Republican Party, he previously served as a representative and senator from California and was ...
approved the Shuttle, and NASA decided on its final design in March. That August, NASA awarded the contract to build the orbiter to North American Rockwell, the solid-rocket booster contract to
Morton Thiokol Thiokol (variously Thiokol Chemical Corporation(/Company), Morton Thiokol Inc., Cordant Technologies Inc., Thiokol Propulsion, AIC Group, ATK Thiokol, ATK Launch Systems Group; finally Orbital ATK before becoming part of Northrop Grumman) was an ...
, and the external tank contract to Martin Marietta.


Development

On June 4, 1974, Rockwell began construction on the first orbiter, OV-101, which would later be named ''Enterprise''. ''Enterprise'' was designed as a test vehicle, and did not include engines or heat shielding. Construction was completed on September 17, 1976, and ''Enterprise'' was moved to the Edwards Air Force Base to begin testing. Rockwell constructed the Main Propulsion Test Article (MPTA)-098, which was a structural truss mounted to the ET with three RS-25 engines attached. It was tested at the National Space Technology Laboratory (NSTL) to ensure that the engines could safely run through the launch profile. Rockwell conducted mechanical and thermal stress tests on Structural Test Article (STA)-099 to determine the effects of aerodynamic and thermal stresses during launch and reentry. The beginning of the development of the RS-25 Space Shuttle Main Engine was delayed for nine months while Pratt & Whitney challenged the contract that had been issued to Rocketdyne. The first engine was completed in March 1975, after issues with developing the first throttleable, reusable engine. During engine testing, the RS-25 experienced multiple nozzle failures, as well as broken turbine blades. Despite the problems during testing, NASA ordered the nine RS-25 engines needed for its three orbiters under construction in May 1978. NASA experienced significant delays in the development of the Space Shuttle's
thermal protection system Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the entr ...
. Previous NASA spacecraft had used
ablative In grammar, the ablative case (pronounced ; sometimes abbreviated ) is a grammatical case for nouns, pronouns, and adjectives in the grammars of various languages; it is sometimes used to express motion away from something, among other uses. ...
heat shields, but those could not be reused. NASA chose to use ceramic tiles for thermal protection, as the shuttle could then be constructed of lightweight
aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
, and the tiles could be individually replaced as needed. Construction began on ''Columbia'' on March 27, 1975, and it was delivered to the KSC on March 25, 1979. At the time of its arrival at the KSC, ''Columbia'' still had 6,000 of its 30,000 tiles remaining to be installed. However, many of the tiles that had been originally installed had to be replaced, requiring two years of installation before ''Columbia'' could fly. On January 5, 1979, NASA commissioned a second orbiter. Later that month, Rockwell began converting STA-099 to OV-099, later named ''Challenger''. On January 29, 1979, NASA ordered two additional orbiters, OV-103 and OV-104, which were named ''Discovery'' and ''Atlantis''. Construction of OV-105, later named ''Endeavour'', began in February 1982, but NASA decided to limit the Space Shuttle fleet to four orbiters in 1983. After the loss of ''Challenger'', NASA resumed production of ''Endeavour'' in September 1987.


Testing

After it arrived at Edwards AFB, ''Enterprise'' underwent flight testing with the
Shuttle Carrier Aircraft The Shuttle Carrier Aircraft (SCA) are two extensively modified Boeing 747 airliners that NASA used to transport Space Shuttle orbiters. One (N905NA) is a 747-100 model, while the other (N911NA) is a short range 747-100SR. The SCAs were used ...
, a Boeing 747 that had been modified to carry the orbiter. In February 1977, ''Enterprise'' began the Approach and Landing Tests (ALT) and underwent captive flights, where it remained attached to the Shuttle Carrier Aircraft for the duration of the flight. On August 12, 1977, ''Enterprise'' conducted its first glide test, where it detached from the Shuttle Carrier Aircraft and landed at Edwards AFB. After four additional flights, ''Enterprise'' was moved to the Marshall Space Flight Center (MSFC) on March 13, 1978. ''Enterprise'' underwent shake tests in the Mated Vertical Ground Vibration Test, where it was attached to an external tank and solid rocket boosters, and underwent vibrations to simulate the stresses of launch. In April 1979, ''Enterprise'' was taken to the KSC, where it was attached to an external tank and solid rocket boosters, and moved to LC-39. Once installed at the launch pad, the Space Shuttle was used to verify the proper positioning of launch complex hardware. ''Enterprise'' was taken back to California in August 1979, and later served in the development of the SLC-6 at
Vandenberg AFB Vandenberg Space Force Base , previously Vandenberg Air Force Base, is a United States Space Force Base in Santa Barbara County, California. Established in 1941, Vandenberg Space Force Base is a space launch base, launching spacecraft from th ...
in 1984. On November 24, 1980, ''Columbia'' was mated with its external tank and solid-rocket boosters, and was moved to LC-39 on December 29. The first Space Shuttle mission, STS-1, would be the first time NASA performed a crewed first-flight of a spacecraft. On April 12, 1981, the Space Shuttle launched for the first time, and was piloted by
John Young John Young may refer to: Academics * John Young (professor of Greek) (died 1820), Scottish professor of Greek at the University of Glasgow * John C. Young (college president) (1803–1857), American educator, pastor, and president of Centre Col ...
and
Robert Crippen Robert Laurel Crippen (born September 11, 1937) is an American retired naval officer and aviator, test pilot, aerospace engineer, and retired astronaut. He traveled into space four times: as Pilot of STS-1 in April 1981, the first Space Shuttl ...
. During the two-day mission, Young and Crippen tested equipment on board the shuttle, and found several of the ceramic tiles had fallen off the top side of the ''Columbia''. NASA coordinated with the Air Force to use satellites to image the underside of ''Columbia'', and determined there was no damage. ''Columbia'' reentered the atmosphere and landed at Edwards AFB on April 14. NASA conducted three additional test flights with ''Columbia'' in 1981 and 1982. On July 4, 1982,
STS-4 STS-4 was the fourth NASA Space Shuttle mission, and also the fourth for Space Shuttle ''Columbia''. Crewed by Ken Mattingly and Henry Hartsfield, the mission launched on June 27, 1982, and landed a week later on July 4, 1982. Due to parachu ...
, flown by
Ken Mattingly Thomas Kenneth Mattingly II (born March 17, 1936) is an American former aviator, aeronautical engineer, test pilot, rear admiral in the United States Navy and astronaut who flew on the Apollo 16, STS-4 and STS-51-C missions. Mattingly had b ...
and
Henry Hartsfield Henry Warren Hartsfield Jr. (21 November 1933 – 17 July 2014) was a United States Air Force Colonel and NASA astronaut who logged over 480 hours in space. He was inducted into the United States Astronaut Hall of Fame in 2006. Personal data ...
, landed on a concrete runway at Edwards AFB. President Ronald Reagan and his wife Nancy met the crew, and delivered a speech. After STS-4, NASA declared its Space Transportation System (STS) operational.


Description

The Space Shuttle was the first operational orbital spacecraft designed for reuse. Each Space Shuttle orbiter was designed for a projected lifespan of 100 launches or ten years of operational life, although this was later extended. At launch, it consisted of the
orbiter A spacecraft is a vehicle or machine designed to spaceflight, fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth ...
, which contained the
crew A crew is a body or a class of people who work at a common activity, generally in a structured or hierarchical organization. A location in which a crew works is called a crewyard or a workyard. The word has nautical resonances: the tasks involved ...
and payload, the
external tank The Space Shuttle external tank (ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplied the fuel and oxidizer under pressure to ...
(ET), and the two
solid rocket boosters A solid rocket booster (SRB) is a large solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and space shuttle, have used SRBs to giv ...
(SRBs). Responsibility for the Shuttle components was spread among multiple NASA field centers. The KSC was responsible for launch, landing, and turnaround operations for equatorial orbits (the only orbit profile actually used in the program). The U.S. Air Force at the
Vandenberg Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in Key West, Florida * Vandenberg Sp ...
was responsible for launch, landing, and turnaround operations for polar orbits (though this was never used). The Johnson Space Center (JSC) served as the central point for all Shuttle operations and the MSFC was responsible for the main engines, external tank, and solid rocket boosters. The
John C. Stennis Space Center The John C. Stennis Space Center (SSC) is a NASA rocket testing facility in Hancock County, Mississippi, United States, on the banks of the Pearl River at the Mississippi–Louisiana border. , it is NASA's largest rocket engine test facility. ...
handled main engine testing, and the Goddard Space Flight Center managed the global tracking network.


Orbiter

The orbiter had design elements and capabilities of both a rocket and an aircraft to allow it to launch vertically and then land as a glider. Its three-part fuselage provided support for the crew compartment, cargo bay, flight surfaces, and engines. The rear of the orbiter contained the Space Shuttle Main Engines (SSME), which provided thrust during launch, as well as the Orbital Maneuvering System (OMS), which allowed the orbiter to achieve, alter, and exit its orbit once in space. Its double- delta wings were long, and were swept 81° at the inner leading edge and 45° at the outer leading edge. Each wing had an inboard and outboard
elevon Elevons or tailerons are aircraft control surfaces that combine the functions of the elevator (used for pitch control) and the aileron (used for roll control), hence the name. They are frequently used on tailless aircraft such as flying wings. A ...
to provide flight control during reentry, along with a flap located between the wings, below the engines to control pitch. The orbiter's
vertical stabilizer A vertical stabilizer or tail fin is the static part of the vertical tail of an aircraft. The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, s ...
was swept backwards at 45° and contained a
rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adve ...
that could split to act as a
speed brake In aeronautics, air brakes or speed brakes are a type of flight control surface used on an aircraft to increase the drag on the aircraft. Air brakes differ from spoilers in that air brakes are designed to increase drag while making litt ...
. The vertical stabilizer also contained a two-part
drag parachute A drogue parachute is a parachute designed for deployment from a rapidly-moving object. It can be used for various purposes, such as to decrease speed, to provide control and stability, or as a pilot parachute to deploy a larger parachute. V ...
system to slow the orbiter after landing. The orbiter used
retractable landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...
with a nose landing gear and two main landing gear, each containing two tires. The main landing gear contained two brake assemblies each, and the nose landing gear contained an electro-hydraulic steering mechanism.


Crew

The Space Shuttle crew varied per mission. The test flights only had two members each, the commander and pilot, who were both qualified pilots that could fly and land the orbiter. The on-orbit operations, such as experiments, payload deployment, and EVAs, were conducted primarily by the mission specialists who were specifically trained for their intended missions and systems. Early in the Space Shuttle program, NASA flew with payload specialists, who were typically systems specialists who worked for the company paying for the payload's deployment or operations. The final payload specialist,
Gregory B. Jarvis Gregory Bruce Jarvis (August 24, 1944 – January 28, 1986) was an American engineer and astronaut who died during the destruction of the Space Shuttle ''Challenger'' on mission STS-51-L, where he was serving as payload specialist for Hughes ...
, flew on STS-51-L, and future non-pilots were designated as mission specialists. An astronaut flew as a crewed spaceflight engineer on both
STS-51-C STS-51-C (formerly STS-10) was the 15th flight of NASA's Space Shuttle program, and the third flight of Space Shuttle ''Discovery''. It launched on January 24, 1985, and made the fourth shuttle landing at Kennedy Space Center, Florida, on Janu ...
and
STS-51-J STS-51-J was the 21st NASA Space Shuttle mission and the first flight of Space Shuttle ''Atlantis''. It launched from Kennedy Space Center, Florida, on October 3, 1985, carrying a payload for the U.S. Department of Defense (DoD), and landed a ...
to serve as a military representative for a
National Reconnaissance Office The National Reconnaissance Office (NRO) is a member of the United States Intelligence Community and an agency of the United States Department of Defense which designs, builds, launches, and operates the reconnaissance satellites of the U.S. fe ...
payload. A Space Shuttle crew typically had seven astronauts, with STS-61-A flying with eight.


Crew compartment

The crew compartment comprised three decks and was the pressurized, habitable area on all Space Shuttle missions. The flight deck consisted of two seats for the commander and pilot, as well as an additional two to four seats for crew members. The mid-deck was located below the flight deck and was where the galley and crew bunks were set up, as well as three or four crew member seats. The mid-deck contained the airlock, which could support two astronauts on an
extravehicular activity Extravehicular activity (EVA) is any activity done by an astronaut in outer space outside a spacecraft. In the absence of a breathable Earthlike atmosphere, the astronaut is completely reliant on a space suit for environmental support. EVA inc ...
(EVA), as well as access to pressurized research modules. An equipment bay was below the mid-deck, which stored environmental control and waste management systems. On the first four Shuttle missions, astronauts wore modified U.S. Air Force high-altitude full-pressure suits, which included a full-pressure helmet during ascent and descent. From the fifth flight,
STS-5 STS-5 was the fifth NASA Space Shuttle mission and the fifth flight of the Space Shuttle ''Columbia''. It launched on November 11, 1982, and landed five days later on November 16, 1982. STS-5 was the first Space Shuttle mission to deploy comm ...
, until the loss of ''Challenger'', the crew wore one-piece light blue
nomex Nomex is a flame-resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967. Properties Nomex and related aramid polymers are related to nylon, but have aromatic backbones, and hence are more rigid and mo ...
flight suits and partial-pressure helmets. After the ''Challenger'' disaster, the crew members wore the Launch Entry Suit (LES), a partial-pressure version of the high-altitude pressure suits with a helmet. In 1994, the LES was replaced by the full-pressure
Advanced Crew Escape Suit The Advanced Crew Escape Suit (ACES), or "pumpkin suit", is a full pressure suit that Space Shuttle crews began wearing after STS-65, for the ascent and entry portions of flight. The suit is a direct descendant of the U.S. Air Force high-altitu ...
(ACES), which improved the safety of the astronauts in an emergency situation. ''Columbia'' originally had modified SR-71 zero-zero ejection seats installed for the
ALT Alt or ALT may refer to: Abbreviations for words * Alt account, an alternative online identity also known as a sock puppet account * Alternate character, in online gaming * Alternate route, type of highway designation * Alternating group, mathema ...
and first four missions, but these were disabled after STS-4 and removed after STS-9. The flight deck was the top level of the crew compartment and contained the flight controls for the orbiter. The commander sat in the front left seat, and the pilot sat in the front right seat, with two to four additional seats set up for additional crew members. The instrument panels contained over 2,100 displays and controls, and the commander and pilot were both equipped with a
heads-up display A head-up display, or heads-up display, also known as a HUD (), is any transparent display that presents data without requiring users to look away from their usual viewpoints. The origin of the name stems from a pilot being able to view informa ...
(HUD) and a Rotational Hand Controller (RHC) to
gimbal A gimbal is a pivoted support that permits rotation of an object about an axis. A set of three gimbals, one mounted on the other with orthogonal pivot axes, may be used to allow an object mounted on the innermost gimbal to remain independent of ...
the engines during powered flight and fly the orbiter during unpowered flight. Both seats also had
rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adve ...
controls, to allow rudder movement in flight and nose-wheel steering on the ground. The orbiter vehicles were originally installed with the Multifunction CRT Display System (MCDS) to display and control flight information. The MCDS displayed the flight information at the commander and pilot seats, as well as at the aft seating location, and also controlled the data on the HUD. In 1998, ''Atlantis'' was upgraded with the Multifunction Electronic Display System (MEDS), which was a glass cockpit upgrade to the flight instruments that replaced the eight MCDS display units with 11 multifunction colored digital screens. MEDS was flown for the first time in May 2000 on
STS-98 STS-98 was a 2001 Space Shuttle mission to the International Space Station (ISS) flown by Space Shuttle '' Atlantis''. It was the first human spaceflight launch of the 21st century. STS-98 delivered to the station the ''Destiny'' Laboratory Mod ...
, and the other orbiter vehicles were upgraded to it. The aft section of the flight deck contained windows looking into the payload bay, as well as an RHC to control the
Remote Manipulator System Canadarm or Canadarm1 (officially Shuttle Remote Manipulator System or SRMS, also SSRMS) is a series of robotic arms that were used on the Space Shuttle orbiters to deploy, manoeuvre, and capture payloads. After the Space Shuttle ''Columbia'' ...
during cargo operations. Additionally, the aft flight deck had monitors for a closed-circuit television to view the cargo bay. The mid-deck contained the crew equipment storage, sleeping area, galley, medical equipment, and hygiene stations for the crew. The crew used modular lockers to store equipment that could be scaled depending on their needs, as well as permanently installed floor compartments. The mid-deck contained a port-side hatch that the crew used for entry and exit while on Earth.


Airlock

Additionally, each orbiter was originally installed with an internal airlock in the mid-deck. The internal airlock was installed as an external airlock in the payload bay on ''Discovery'', ''Atlantis'', and ''Endeavour'' to improve docking with
Mir ''Mir'' (russian: Мир, ; ) was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. ''Mir'' was the first modular space station and was assembled in orbit from 1986 to&n ...
and the
ISS The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA (J ...
, along with the Orbiter Docking System. The airlock module can be fitted in the mid-bay, or connected to it but in the payload bay.NASA Space Shuttle - Owners manual - Haynes With an internal cylindrical volume of 1.60 m (5 ft 3 in) diameter and 2.11 m (6 ft 11 in) in length, it can hold two suited astronauts. It has two 'D' shaped hatchways 1.02 m (40 in) long (diameter), and 0.91 m (36 in) wide.


Flight systems

The orbiter was equipped with an
avionics Avionics (a blend of ''aviation'' and ''electronics'') are the electronic systems used on aircraft. Avionic systems include communications, navigation, the display and management of multiple systems, and the hundreds of systems that are fit ...
system to provide information and control during atmospheric flight. Its avionics suite contained three microwave scanning beam landing systems, three gyroscopes, three
TACAN A tactical air navigation system, commonly referred to by the acronym TACAN, is a navigation system used by military aircraft. It provides the user with bearing and distance (slant-range or hypotenuse) to a ground or ship-borne station. It is a mor ...
s, three
accelerometer An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is acc ...
s, two
radar altimeter A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrain presently beneath an aircraft or spacecraft by timing how long it t ...
s, two
barometric altimeter An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. The m ...
s, three
attitude indicator The attitude indicator (AI), formerly known as the gyro horizon or artificial horizon, is a flight instrument that informs the pilot of the aircraft orientation relative to Earth's horizon, and gives an immediate indication of the smallest o ...
s, two Mach indicators, and two Mode C
transponders In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight tran ...
. During reentry, the crew deployed two air data probes once they were traveling slower than Mach 5. The orbiter had three inertial measuring units (IMU) that it used for guidance and navigation during all phases of flight. The orbiter contains two
star tracker A star tracker is an optical device that measures the positions of stars using photocells or a camera. As the positions of many stars have been measured by astronomers to a high degree of accuracy, a star tracker on a satellite or spacecraft may ...
s to align the IMUs while in orbit. The star trackers are deployed while in orbit, and can automatically or manually align on a star. In 1991, NASA began upgrading the inertial measurement units with an
inertial navigation system An inertial navigation system (INS) is a navigation device that uses motion sensors (accelerometers), rotation sensors ( gyroscopes) and a computer to continuously calculate by dead reckoning the position, the orientation, and the velocity (dir ...
(INS), which provided more accurate location information. In 1993, NASA flew a
GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
receiver for the first time aboard STS-51. In 1997, Honeywell began developing an integrated GPS/INS to replace the IMU, INS, and TACAN systems, which first flew on
STS-118 STS-118 was a Space Shuttle mission to the International Space Station (ISS) flown by the orbiter '' Endeavour''. STS-118 lifted off on 8 August 2007 from launch pad 39A at Kennedy Space Center (KSC), Florida and landed at the Shuttle Landing Fac ...
in August 2007. While in orbit, the crew primarily communicated using one of four S band radios, which provided both voice and data communications. Two of the S band radios were
phase modulation Phase modulation (PM) is a modulation pattern for conditioning communication signals for transmission. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Phase modulation is one of the two principal forms of ...
transceiver In radio communication, a transceiver is an electronic device which is a combination of a radio ''trans''mitter and a re''ceiver'', hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. Thes ...
s, and could transmit and receive information. The other two S band radios were
frequency modulation Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing. In analog fre ...
transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...
s and were used to transmit data to NASA. As S band radios can operate only within their
line of sight The line of sight, also known as visual axis or sightline (also sight line), is an imaginary line between a viewer/observer/ spectator's eye(s) and a subject of interest, or their relative direction. The subject may be any definable object taken ...
, NASA used the
Tracking and Data Relay Satellite System The U.S. Tracking and Data Relay Satellite System (TDRSS) is a network of American communications satellites (each called a tracking and data relay satellite, TDRS) and ground stations used by NASA for space communications. The system was desig ...
and the Spacecraft Tracking and Data Acquisition Network ground stations to communicate with the orbiter throughout its orbit. Additionally, the orbiter deployed a high-bandwidth Ku band radio out of the cargo bay, which could also be utilized as a rendezvous radar. The orbiter was also equipped with two UHF radios for communications with
air traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airs ...
and astronauts conducting EVA. The Space Shuttle's
fly-by-wire Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires, and flight control ...
control system was entirely reliant on its main computer, the Data Processing System (DPS). The DPS controlled the flight controls and thrusters on the orbiter, as well as the ET and SRBs during launch. The DPS consisted of five general-purpose computers (GPC), two magnetic tape mass memory units (MMUs), and the associated sensors to monitors the Space Shuttle components. The original GPC used was the IBM AP-101B, which used a separate
central processing unit A central processing unit (CPU), also called a central processor, main processor or just Processor (computing), processor, is the electronic circuitry that executes Instruction (computing), instructions comprising a computer program. The CPU per ...
(CPU) and input/output processor (IOP), and non-volatile solid-state memory. From 1991 to 1993, the orbiter vehicles were upgraded to the AP-101S, which improved the memory and processing capabilities, and reduced the volume and weight of the computers by combining the CPU and IOP into a single unit. Four of the GPCs were loaded with the Primary Avionics Software System (PASS), which was Space Shuttle-specific software that provided control through all phases of flight. During ascent, maneuvering, reentry, and landing, the four PASS GPCs functioned identically to produce quadruple redundancy and would error check their results. In case of a software error that would cause erroneous reports from the four PASS GPCs, a fifth GPC ran the Backup Flight System, which used a different program and could control the Space Shuttle through ascent, orbit, and reentry, but could not support an entire mission. The five GPCs were separated in three separate bays within the mid-deck to provide redundancy in the event of a cooling fan failure. After achieving orbit, the crew would switch some of the GPCs functions from guidance, navigation, and control (GNC) to systems management (SM) and payload (PL) to support the operational mission. The Space Shuttle was not launched if its flight would run from December to January, as its flight software would have required the orbiter vehicle's computers to be reset at the year change. In 2007, NASA engineers devised a solution so Space Shuttle flights could cross the year-end boundary. Space Shuttle missions typically brought a portable general support computer (PGSC) that could integrate with the orbiter vehicle's computers and communication suite, as well as monitor scientific and payload data. Early missions brought the Grid Compass, one of the first laptop computers, as the PGSC, but later missions brought
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...
and
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...
laptops.


Payload bay

The payload bay comprised most of the orbiter vehicle's
fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraf ...
, and provided the cargo-carrying space for the Space Shuttle's payloads. It was long and wide, and could accommodate cylindrical payloads up to in diameter. Two payload bay doors hinged on either side of the bay, and provided a relatively airtight seal to protect payloads from heating during launch and reentry. Payloads were secured in the payload bay to the attachment points on the longerons. The payload bay doors served an additional function as radiators for the orbiter vehicle's heat, and were opened upon reaching orbit for heat rejection. The orbiter could be used in conjunction with a variety of add-on components depending on the mission. This included orbital laboratories, boosters for launching payloads farther into space, the Remote Manipulator System (RMS), and optionally the EDO pallet to extend the mission duration. To limit the fuel consumption while the orbiter was docked at the ISS, the
Station-to-Shuttle Power Transfer System The electrical system of the International Space Station is a critical resource for the International Space Station (ISS) because it allows the crew to live comfortably, to safely operate the station, and to perform scientific experiments. The ...
(SSPTS) was developed to convert and transfer station power to the orbiter. The SSPTS was first used on STS-118, and was installed on ''Discovery'' and ''Endeavour''.


Remote Manipulator System

The Remote Manipulator System (RMS), also known as Canadarm, was a mechanical arm attached to the cargo bay. It could be used to grasp and manipulate payloads, as well as serve as a mobile platform for astronauts conducting an EVA. The RMS was built by the Canadian company
Spar Aerospace SPAR Aerospace was a Canadian aerospace company. It produced equipment for the Canadian Space Agency to be used in cooperation with NASA's Space Shuttle program, most notably the Canadarm, a remote manipulator system. The company went through a s ...
and was controlled by an astronaut inside the orbiter's flight deck using their windows and closed-circuit television. The RMS allowed for six degrees of freedom and had six joints located at three points along the arm. The original RMS could deploy or retrieve payloads up to , which was later improved to .


Spacelab

The Spacelab module was a European-funded pressurized laboratory that was carried within the payload bay and allowed for scientific research while in orbit. The Spacelab module contained two segments that were mounted in the aft end of the payload bay to maintain the center of gravity during flight. Astronauts entered the Spacelab module through a or tunnel that connected to the airlock. The Spacelab equipment was primarily stored in pallets, which provided storage for both experiments as well as computer and power equipment. Spacelab hardware was flown on 28 missions through 1999 and studied subjects including astronomy, microgravity, radar, and life sciences. Spacelab hardware also supported missions such as Hubble Space Telescope (HST) servicing and space station resupply. The Spacelab module was tested on STS-2 and STS-3, and the first full mission was on STS-9.


RS-25 engines

Three RS-25 engines, also known as the Space Shuttle Main Engines (SSME), were mounted on the orbiter's aft fuselage in a triangular pattern. The engine nozzles could gimbal ±10.5° in pitch, and ±8.5° in yaw during ascent to change the direction of their thrust to steer the Shuttle. The
titanium alloy Titanium alloys are alloys that contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness (even at extreme temperatures). They are light in weight, have extraordinary corrosion resista ...
reusable engines were independent of the orbiter vehicle and would be removed and replaced in between flights. The RS-25 is a staged-combustion cycle cryogenic engine that used liquid oxygen and hydrogen and had a higher chamber pressure than any previous liquid-fueled rocket. The original main combustion chamber operated at a maximum pressure of . The engine nozzle is tall and has an interior diameter of . The nozzle is cooled by 1,080 interior lines carrying liquid hydrogen and is thermally protected by insulative and ablative material. The RS-25 engines had several improvements to enhance reliability and power. During the development program, Rocketdyne determined that the engine was capable of safe reliable operation at 104% of the originally specified thrust. To keep the engine thrust values consistent with previous documentation and software, NASA kept the originally specified thrust at 100%, but had the RS-25 operate at higher thrust. RS-25 upgrade versions were denoted as Block I and Block II. 109% thrust level was achieved with the Block II engines in 2001, which reduced the chamber pressure to , as it had a larger
throat In vertebrate anatomy, the throat is the front part of the neck, internally positioned in front of the vertebrae. It contains the pharynx and larynx. An important section of it is the epiglottis, separating the esophagus from the trachea (windpip ...
area. The normal maximum throttle was 104 percent, with 106% or 109% used for mission aborts.


Orbital Maneuvering System

The Orbital Maneuvering System (OMS) consisted of two aft-mounted AJ10-190 engines and the associated propellant tanks. The AJ10 engines used
monomethylhydrazine Monomethylhydrazine (mono-methyl hydrazine, MMH) is a highly toxic, volatile hydrazine derivative with the chemical formula . It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as ...
(MMH) oxidized by dinitrogen tetroxide (N2O4). The pods carried a maximum of of MMH and of N2O4. The OMS engines were used after main engine cut-off (MECO) for orbital insertion. Throughout the flight, they were used for orbit changes, as well as the deorbit burn prior to reentry. Each OMS engine produced of thrust, and the entire system could provide of velocity change.


Thermal protection system

The orbiter was protected from heat during reentry by the thermal protection system (TPS), a thermal soaking protective layer around the orbiter. In contrast with previous US spacecraft, which had used ablative heat shields, the reusability of the orbiter required a multi-use heat shield. During reentry, the TPS experienced temperatures up to , but had to keep the orbiter vehicle's aluminum skin temperature below . The TPS primarily consisted of four types of tiles. The nose cone and leading edges of the wings experienced temperatures above , and were protected by reinforced carbon-carbon tiles (RCC). Thicker RCC tiles were developed and installed in 1998 to prevent damage from micrometeoroid and orbital debris, and were further improved after RCC damage caused in the ''Columbia'' disaster. Beginning with STS-114, the orbiter vehicles were equipped with the wing leading edge impact detection system to alert the crew to any potential damage. The entire underside of the orbiter vehicle, as well as the other hottest surfaces, were protected with high-temperature reusable surface insulation. Areas on the upper parts of the orbiter vehicle were coated in a white low-temperature reusable surface insulation, which provided protection for temperatures below . The payload bay doors and parts of the upper wing surfaces were coated in reusable felt surface insulation, as the temperature there remained below .


External tank

The Space Shuttle external tank (ET) carried the propellant for the Space Shuttle Main Engines, and connected the orbiter vehicle with the solid rocket boosters. The ET was tall and in diameter, and contained separate tanks for liquid oxygen and liquid hydrogen. The liquid oxygen tank was housed in the nose of the ET, and was tall. The liquid hydrogen tank comprised the bulk of the ET, and was tall. The orbiter vehicle was attached to the ET at two umbilical plates, which contained five propellant and two electrical umbilicals, and forward and aft structural attachments. The exterior of the ET was covered in orange spray-on foam to allow it to survive the heat of ascent. The ET provided propellant to the Space Shuttle Main Engines from liftoff until main engine cutoff. The ET separated from the orbiter vehicle 18 seconds after engine cutoff and could be triggered automatically or manually. At the time of separation, the orbiter vehicle retracted its umbilical plates, and the umbilical cords were sealed to prevent excess propellant from venting into the orbiter vehicle. After the bolts attached at the structural attachments were sheared, the ET separated from the orbiter vehicle. At the time of separation, gaseous oxygen was vented from the nose to cause the ET to tumble, ensuring that it would break up upon reentry. The ET was the only major component of the Space Shuttle system that was not reused, and it would travel along a ballistic trajectory into the Indian or Pacific Ocean. For the first two missions, STS-1 and
STS-2 STS-2 was the second Space Shuttle mission conducted by NASA, and the second flight of the orbiter ''Columbia''. The mission, crewed by Joe H. Engle and Richard H. Truly, launched on November 12, 1981, and landed two days later on November 14 ...
, the ET was covered in of white fire-retardant latex paint to provide protection against damage from ultraviolet radiation. Further research determined that the orange foam itself was sufficiently protected, and the ET was no longer covered in latex paint beginning on STS-3. A light-weight tank (LWT) was first flown on STS-6, which reduced tank weight by . The LWT's weight was reduced by removing components from the hydrogen tank and reducing the thickness of some skin panels. In 1998, a super light-weight ET (SLWT) first flew on
STS-91 STS-91 was the final Space Shuttle mission to the ''Mir'' space station. It was flown by Space Shuttle ''Discovery'', and launched from Kennedy Space Center, Florida, on 2 June 1998. Crew Mission highlights STS-91 marked the final Shuttle/''M ...
. The SLWT used the 2195 aluminum-lithium alloy, which was 40% stronger and 10% less dense than its predecessor, 2219 aluminum-lithium alloy. The SLWT weighed less than the LWT, which allowed the Space Shuttle to deliver heavy elements to ISS's high inclination orbit.


Solid Rocket Boosters

The Solid Rocket Boosters (SRB) provided 71.4% of the Space Shuttle's thrust during liftoff and ascent, and were the largest solid-propellant motors ever flown. Each SRB was tall and wide, weighed , and had a steel exterior approximately thick. The SRB's subcomponents were the solid-propellant motor, nose cone, and rocket nozzle. The solid-propellant motor comprised the majority of the SRB's structure. Its casing consisted of 11 steel sections which made up its four main segments. The nose cone housed the forward separation motors and the parachute systems that were used during recovery. The rocket nozzles could gimbal up to 8° to allow for in-flight adjustments. The rocket motors were each filled with a total of solid rocket propellant (
APCP Ammonium perchlorate composite propellant (APCP) is a solid-propellant rocket fuel. It differs from many traditional solid rocket propellants such as black powder or zinc-sulfur, not only in chemical composition and overall performance but al ...
+ PBAN), and joined in the
Vehicle Assembly Building The Vehicle Assembly Building (originally the Vertical Assembly Building), or VAB, is a large building at NASA's Kennedy Space Center (KSC), designed to assemble large pre-manufactured space vehicle components, such as the massive Saturn V and th ...
(VAB) at KSC. In addition to providing thrust during the first stage of launch, the SRBs provided structural support for the orbiter vehicle and ET, as they were the only system that was connected to the
mobile launcher platform A mobile launcher platform (MLP), also known as mobile launch platform, is a structure used to support a large multistage space vehicle which is assembled (stacked) vertically in an integration facility (e.g. the Vehicle Assembly Building) and t ...
(MLP). At the time of launch, the SRBs were armed at T−5 minutes, and could only be electrically ignited once the RS-25 engines had ignited and were without issue. They each provided of thrust, which was later improved to beginning on
STS-8 STS-8 was the eighth NASA Space Shuttle mission and the third flight of the Space Shuttle ''Challenger''. It launched on August 30, 1983, and landed on September 5, 1983, conducting the first night launch and night landing of the Space Shuttl ...
. After expending their fuel, the SRBs were jettisoned approximately two minutes after launch at an altitude of approximately . Following separation, they deployed drogue and main parachutes, landed in the ocean, and were recovered by the crews aboard the ships MV ''Freedom Star'' and MV ''Liberty Star''. Once they were returned to Cape Canaveral, they were cleaned and disassembled. The rocket motor, igniter, and nozzle were then shipped to Thiokol to be refurbished and reused on subsequent flights. The SRBs underwent several redesigns throughout the program's lifetime. STS-6 and
STS-7 STS-7 was NASA's seventh Space Shuttle mission, and the second mission for the Space Shuttle ''Challenger''. During the mission, ''Challenger'' deployed several satellites into orbit. The shuttle launched from Kennedy Space Center on June 18, ...
used SRBs that were lighter than the standard-weight cases due to walls that were thinner, but were determined to be too thin. Subsequent flights until
STS-26 STS-26 was the 26th NASA Space Shuttle mission and the seventh flight of the orbiter ''Discovery''. The mission launched from Kennedy Space Center, Florida, on September 29, 1988, and landed four days later on October 3, 1988. STS-26 was decla ...
used cases that were thinner than the standard-weight cases, which saved . After the ''Challenger'' disaster as a result of an
O-ring An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more par ...
failing at low temperature, the SRBs were redesigned to provide a constant seal regardless of the ambient temperature.


Support vehicles

The Space Shuttle's operations were supported by vehicles and infrastructure that facilitated its transportation, construction, and crew access. The crawler-transporters carried the MLP and the Space Shuttle from the VAB to the launch site. The
Shuttle Carrier Aircraft The Shuttle Carrier Aircraft (SCA) are two extensively modified Boeing 747 airliners that NASA used to transport Space Shuttle orbiters. One (N905NA) is a 747-100 model, while the other (N911NA) is a short range 747-100SR. The SCAs were used ...
(SCA) were two modified Boeing 747s that could carry an orbiter on its back. The original SCA (N905NA) was first flown in 1975, and was used for the
ALT Alt or ALT may refer to: Abbreviations for words * Alt account, an alternative online identity also known as a sock puppet account * Alternate character, in online gaming * Alternate route, type of highway designation * Alternating group, mathema ...
and ferrying the orbiter from Edwards AFB to the KSC on all missions prior to 1991. A second SCA (N911NA) was acquired in 1988, and was first used to transport ''Endeavour'' from the factory to the KSC. Following the retirement of the Space Shuttle, N905NA was put on display at the JSC, and N911NA was put on display at the Joe Davis Heritage Airpark in Palmdale, California. The Crew Transport Vehicle (CTV) was a modified airport
jet bridge A jet bridge (also termed jetway, jetwalk, airgate, gangway, aerobridge/airbridge, skybridge, finger, airtube, expedited suspended passenger entry system (E-SPES), or its official industry name passenger boarding bridge (PBB)) is an enclosed, ...
that was used to assist astronauts to egress from the orbiter after landing, where they would undergo their post-mission medical checkups. The Astrovan transported astronauts from the crew quarters in the Operations and Checkout Building to the launch pad on launch day. The
NASA Railroad The NASA Railroad is a Class III industrial short-line railroad at the Kennedy Space Center in Cape Canaveral, Florida. The railroad consists of of track connecting the mainline of the Florida East Coast Railway and trackage at the Cape Canav ...
comprised three locomotives that transported SRB segments from the Florida East Coast Railway in Titusville to the KSC.


Mission profile


Launch preparation

The Space Shuttle was prepared for launch primarily in the VAB at the KSC. The SRBs were assembled and attached to the external tank on the MLP. The orbiter vehicle was prepared at the Orbiter Processing Facility (OPF) and transferred to the VAB, where a crane was used to rotate it to the vertical orientation and mate it to the external tank. Once the entire stack was assembled, the MLP was carried for to
Launch Complex 39 Launch Complex 39 (LC-39) is a rocket launch site at the John F. Kennedy Space Center on Merritt Island in Florida, United States. The site and its collection of facilities were originally built as the Apollo program's "Moonport" and later m ...
by one of the crawler-transporters. After the Space Shuttle arrived at one of the two launchpads, it would connect to the Fixed and Rotation Service Structures, which provided servicing capabilities, payload insertion, and crew transportation. The crew was transported to the launch pad at T−3 hours and entered the orbiter vehicle, which was closed at T−2 hours. Liquid oxygen and hydrogen were loaded into the external tank via umbilicals that attached to the orbiter vehicle, which began at T−5 hours 35 minutes. At T−3 hours 45 minutes, the hydrogen fast-fill was complete, followed 15 minutes later by the oxygen tank fill. Both tanks were slowly filled up until the launch as the oxygen and hydrogen evaporated. The launch commit criteria considered precipitation, temperatures, cloud cover, lightning forecast, wind, and humidity. The Space Shuttle was not launched under conditions where it could have been struck by
lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an avera ...
, as its exhaust plume could have triggered lightning by providing a current path to ground after launch, which occurred on Apollo 12. The NASA Anvil Rule for a Shuttle launch stated that an
anvil cloud A cumulonimbus incus (Latin ''incus'', "anvil"), also known as an anvil cloud, is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape. It signifies the thunderstor ...
could not appear within a distance of . The Shuttle Launch Weather Officer monitored conditions until the final decision to scrub a launch was announced. In addition to the weather at the launch site, conditions had to be acceptable at one of the Transatlantic Abort Landing sites and the SRB recovery area.


Launch

The mission crew and the Launch Control Center (LCC) personnel completed systems checks throughout the countdown. Two built-in holds at T−20 minutes and T−9 minutes provided scheduled breaks to address any issues and additional preparation. After the built-in hold at T−9 minutes, the countdown was automatically controlled by the Ground Launch Sequencer (GLS) at the LCC, which stopped the countdown if it sensed a critical problem with any of the Space Shuttle's onboard systems. At T−3 minutes 45 seconds, the engines began conducting gimbal tests, which were concluded at T−2 minutes 15 seconds. The ground launch processing system handed off the control to the orbiter vehicle's GPCs at T−31 seconds. At T−16 seconds, the GPCs armed the SRBs, the sound suppression system (SPS) began to drench the MLP and SRB trenches with of water to protect the orbiter vehicle from damage by
acoustical Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician ...
energy and rocket exhaust reflected from the flame trench and MLP during lift-off. At T−10 seconds, hydrogen igniters were activated under each engine bell to quell the stagnant gas inside the cones before ignition. Failure to burn these gases could trip the onboard sensors and create the possibility of an overpressure and explosion of the vehicle during the firing phase. The hydrogen tank's prevalves were opened at T−9.5 seconds in preparation for engine start. Beginning at T−6.6 seconds, the main engines were ignited sequentially at 120-millisecond intervals. All three RS-25 engines were required to reach 90% rated thrust by T−3 seconds, otherwise the GPCs would initiate an RSLS abort. If all three engines indicated nominal performance by T−3 seconds, they were commanded to gimbal to liftoff configuration and the command would be issued to arm the SRBs for ignition at T−0. Between T−6.6 seconds and T−3 seconds, while the RS-25 engines were firing but the SRBs were still bolted to the pad, the offset thrust would cause the Space Shuttle to pitch down measured at the tip of the external tank; the 3-second delay allowed the stack to return to nearly vertical before SRB ignition. This movement was nicknamed the "twang." At T−0, the eight frangible nuts holding the SRBs to the pad were detonated, the final umbilicals were disconnected, the SSMEs were commanded to 100% throttle, and the SRBs were ignited. By T+0.23 seconds, the SRBs built up enough thrust for liftoff to commence, and reached maximum chamber pressure by T+0.6 seconds. At T−0, the JSC Mission Control Center assumed control of the flight from the LCC. At T+4 seconds, when the Space Shuttle reached an altitude of , the RS-25 engines were throttled up to 104.5%. At approximately T+7 seconds, the Space Shuttle rolled to a heads-down orientation at an altitude of , which reduced aerodynamic stress and provided an improved communication and navigation orientation. Approximately 20–30 seconds into ascent and an altitude of , the RS-25 engines were throttled down to 65–72% to reduce the maximum aerodynamic forces at Max Q. Additionally, the shape of the SRB propellant was designed to cause thrust to decrease at the time of Max Q. The GPCs could dynamically control the throttle of the RS-25 engines based upon the performance of the SRBs. At approximately T+123 seconds and an altitude of , pyrotechnic fasteners released the SRBs, which reached an apogee of before parachuting into the Atlantic Ocean. The Space Shuttle continued its ascent using only the RS-25 engines. On earlier missions, the Space Shuttle remained in the heads-down orientation to maintain communications with the tracking station in Cooper's Island, Bermuda, Bermuda, but later missions, beginning with STS-87, rolled to a heads-up orientation at T+6 minutes for communication with the tracking and data relay satellite constellation. The RS-25 engines were throttled at T+7 minutes 30 seconds to limit vehicle acceleration to 3 ''g''. At 6 seconds prior to main engine cutoff (MECO), which occurred at T+8 minutes 30 seconds, the RS-25 engines were throttled down to 67%. The GPCs controlled ET separation and dumped the remaining liquid oxygen and hydrogen to prevent outgassing while in orbit. The ET continued on a ballistic trajectory and broke up during reentry, with some small pieces landing in the Indian or Pacific Ocean. Early missions used two firings of the OMS to achieve orbit; the first firing raised the apogee while the second circularized the orbit. Missions after STS-38 used the RS-25 engines to achieve the optimal apogee, and used the OMS engines to circularize the orbit. The orbital altitude and inclination were mission-dependent, and the Space Shuttle's orbits varied from to .


In orbit

The type of mission the Space Shuttle was assigned to dictate the type of orbit that it entered. The initial design of the reusable Space Shuttle envisioned an increasingly cheap launch platform to deploy commercial and government satellites. Early missions routinely ferried satellites, which determined the type of orbit that the orbiter vehicle would enter. Following the ''Challenger'' disaster, many commercial payloads were moved to expendable commercial rockets, such as the Delta II. While later missions still launched commercial payloads, Space Shuttle assignments were routinely directed towards scientific payloads, such as the
Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...
, Spacelab, and the Galileo (spacecraft), Galileo spacecraft. Beginning with STS-74, the orbiter vehicle conducted dockings with the Mir space station. In its final decade of operation, the Space Shuttle was used for the construction of the
International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
. Most missions involved staying in orbit several days to two weeks, although longer missions were possible with the Extended Duration Orbiter pallet. The 17 day 15 hour STS-80 mission was the longest Space Shuttle mission duration.


Re-entry and landing

Approximately four hours prior to deorbit, the crew began preparing the orbiter vehicle for reentry by closing the payload doors, radiating excess heat, and retracting the Ku band antenna. The orbiter vehicle maneuvered to an upside-down, tail-first orientation and began a 2–4 minute OMS burn approximately 20 minutes before it reentered the atmosphere. The orbiter vehicle reoriented itself to a nose-forward position with a 40° angle-of-attack, and the forward reaction control system (RCS) jets were emptied of fuel and disabled prior to reentry. The orbiter vehicle's reentry was defined as starting at an altitude of , when it was traveling at approximately Mach 25. The orbiter vehicle's reentry was controlled by the GPCs, which followed a preset angle-of-attack plan to prevent unsafe heating of the TPS. During reentry, the orbiter's speed was regulated by altering the amount of drag produced, which was controlled by means of angle of attack, as well as bank angle. The latter could be used to control drag without changing the angle of attack. A series of roll reversals were performed to control azimuth while banking. The orbiter vehicle's aft RCS jets were disabled as its ailerons, elevators, and rudder became effective in the lower atmosphere. At an altitude of , the orbiter vehicle opened its speed brake on the vertical stabilizer. At 8 minutes 44 seconds prior to landing, the crew deployed the air data probes, and began lowering the angle-of-attack to 36°. The orbiter's maximum glide ratio/lift-to-drag ratio varied considerably with speed, ranging from 1.3 at hypersonic speeds to 4.9 at subsonic speeds. The orbiter vehicle flew to one of the two Heading Alignment Cones, located away from each end of the runway's centerline, where it made its final turns to dissipate excess energy prior to its approach and landing. Once the orbiter vehicle was traveling subsonically, the crew took over manual control of the flight. The approach and landing phase began when the orbiter vehicle was at an altitude of and traveling at . The orbiter followed either a 20° or 18° glideslope and descended at approximately . The speed brake was used to keep a continuous speed, and crew initiated a pre-flare maneuver to a 1.5° glideslope at an altitude of . The landing gear was deployed 10 seconds prior to touchdown, when the orbiter was at an altitude of and traveling . A final flare maneuver reduced the orbiter vehicle's descent rate to , with touchdown occurring at , depending on the weight of the orbiter vehicle. After the landing gear touched down, the crew deployed a drag chute out of the vertical stabilizer, and began wheel braking when the orbiter was traveling slower than . After the orbiter's wheels stopped, the crew deactivated the flight components and prepared to exit.


Landing sites

The primary Space Shuttle landing site was the
Shuttle Landing Facility The Shuttle Landing Facility (SLF) also known as Launch and Landing Facility (LLF) is an airport located on Merritt Island in Brevard County, Florida, United States. It is a part of the Kennedy Space Center and was used by Space Shuttle for ...
at KSC, where 78 of the 133 successful landings occurred. In the event of unfavorable landing conditions, the Shuttle could delay its landing or land at an alternate location. The primary alternate was Edwards AFB, which was used for 54 landings. STS-3 landed at the White Sands Space Harbor in New Mexico and required extensive post-processing after exposure to the gypsum-rich sand, some of which was found in ''Columbia'' debris after STS-107. Landings at alternate airfields required the Shuttle Carrier Aircraft to transport the orbiter back to Cape Canaveral. In addition to the pre-planned landing airfields, there were 85 agreed-upon emergency landing sites to be used in different abort scenarios, with 58 located in other countries. The landing locations were chosen based upon political relationships, favorable weather, a runway at least long, and TACAN or Distance measuring equipment, DME equipment. Additionally, as the orbiter vehicle only had UHF radios, international sites with only VHF radios would have been unable to communicate directly with the crew. Facilities on the east coast of the US were planned for East Coast Abort Landings, while several sites in Europe and Africa were planned in the event of a Transoceanic Abort Landing. The facilities were prepared with equipment and personnel in the event of an emergency shuttle landing but were never used.


Post-landing processing

After the landing, ground crews approached the orbiter to conduct safety checks. Teams wearing self-contained breathing gear tested for the presence of hydrogen, hydrazine, monomethylhydrazine, nitrogen tetroxide, and ammonia to ensure the landing area was safe. Air conditioning and Freon lines were connected to cool the crew and equipment and dissipate excess heat from reentry. A flight surgeon boarded the orbiter and performed medical checks of the crew before they disembarked. Once the orbiter was secured, it was towed to the OPF to be inspected, repaired, and prepared for the next mission.


Space Shuttle program

The Space Shuttle flew from April 12, 1981, until July 21, 2011. Throughout the program, the Space Shuttle had 135 missions, of which 133 returned safely. Throughout its lifetime, the Space Shuttle was used to conduct scientific research, deploy commercial, military, and scientific payloads, and was involved in the construction and operation of Mir and the ISS. During its tenure, the Space Shuttle served as the only U.S. vehicle to launch astronauts, of which there was no replacement until the launch of
Crew Dragon Demo-2 Crew Dragon Demo-2 (officially Crew Demo-2, SpaceX Demo-2, or Demonstration Mission-2) was the first crewed test flight of the Crew Dragon spacecraft. The spacecraft, named '' Endeavour'', launched on 30 May 2020 on a Falcon 9 booster, and ca ...
on May 30, 2020.


Budget

The overall NASA budget of the Space Shuttle program has been estimated to be $221 billion (in 2012 dollars). The developers of the Space Shuttle advocated for reusability as a cost-saving measure, which resulted in higher development costs for presumed lower costs-per-launch. During the design of the Space Shuttle, the Phase B proposals were not as cheap as the initial Phase A estimates indicated; Space Shuttle program manager Robert Thompson acknowledged that reducing cost-per-pound was not the primary objective of the further design phases, as other technical requirements could not be met with the reduced costs. Development estimates made in 1972 projected a per-pound cost of payload as low as $1,109 (in 2012) per pound, but the actual payload costs, not to include the costs for the research and development of the Space Shuttle, were $37,207 (in 2012) per pound. Per-launch costs varied throughout the program and were dependent on the rate of flights as well as research, development, and investigation proceedings throughout the Space Shuttle program. In 1982, NASA published an estimate of $260 million (in 2012) per flight, which was based on the prediction of 24 flights per year for a decade. The per-launch cost from 1995 to 2002, when the orbiters and ISS were not being constructed and there was no recovery work following a loss of crew, was $806 million. NASA published a study in 1999 that concluded that costs were $576 million (in 2012) if there were seven launches per year. In 2009, NASA determined that the cost of adding a single launch per year was $252 million (in 2012), which indicated that much of the Space Shuttle program costs are for year-round personnel and operations that continued regardless of the launch rate. Accounting for the entire Space Shuttle program budget, the per-launch cost was $1.642 billion (in 2012).


Disasters

On January 28, 1986, STS-51-L disintegrated 73 seconds after launch, due to the failure of the right SRB, killing all seven astronauts on board ''Challenger''. The disaster was caused by the low-temperature impairment of an O-ring, a mission-critical seal used between segments of the SRB casing. Failure of the O-ring allowed hot combustion gases to escape from between the booster sections and burn through the adjacent ET, leading to a sequence of catastrophic events which caused the orbiter to disintegrate. Repeated warnings from design engineers voicing concerns about the lack of evidence of the O-rings' safety when the temperature was below had been ignored by NASA managers. On February 1, 2003, ''Columbia'' disintegrated during re-entry, killing all seven of the STS-107 crew, because of damage to the Reinforced carbon-carbon, carbon-carbon leading edge of the wing caused during launch. Ground control engineers had made three separate requests for high-resolution images taken by the Department of Defense that would have provided an understanding of the extent of the damage, while NASA's chief TPS engineer requested that astronauts on board ''Columbia'' be allowed to leave the vehicle to inspect the damage. NASA managers intervened to stop the Department of Defense's imaging of the orbiter and refused the request for the spacewalk, and thus the feasibility of scenarios for astronaut repair or rescue by ''Atlantis'' were not considered by NASA management at the time.


Criticism

The partial reusability of the Space Shuttle was one of the primary design requirements during its initial development. The technical decisions that dictated the orbiter's return and re-use reduced the per-launch payload capabilities. The original intention was to compensate for this lower payload by lowering the per-launch costs and a high launch frequency. However, the actual costs of a Space Shuttle launch were higher than initially predicted, and the Space Shuttle did not fly the intended 24 missions per year as initially predicted by NASA. The Space Shuttle was originally intended as a launch vehicle to deploy satellites, which it was primarily used for on the missions prior to the ''Challenger'' disaster. NASA's pricing, which was below cost, was lower than expendable launch vehicles; the intention was that the high volume of Space Shuttle missions would compensate for early financial losses. The improvement of expendable launch vehicles and the transition away from commercial payloads on the Space Shuttle resulted in expendable launch vehicles becoming the primary deployment option for satellites. A key customer for the Space Shuttle was the
National Reconnaissance Office The National Reconnaissance Office (NRO) is a member of the United States Intelligence Community and an agency of the United States Department of Defense which designs, builds, launches, and operates the reconnaissance satellites of the U.S. fe ...
(NRO) responsible for spy satellites. The existence of NRO's connection was classified through 1993, and secret considerations of NRO payload requirements led to lack of transparency in the program. The proposed Shuttle-Centaur program, cancelled in the wake of the ''Challenger'' disaster, would have pushed the spacecraft beyond its operational capacity. The fatal ''Challenger'' and ''Columbia'' disasters demonstrated the safety risks of the Space Shuttle that could result in the loss of the crew. The spaceplane design of the orbiter limited the abort options, as the abort scenarios required the controlled flight of the orbiter to a runway or to allow the crew to egress individually, rather than the abort escape options on the Apollo (spacecraft), Apollo and Soyuz (spacecraft), Soyuz space capsules. Early safety analyses advertised by NASA engineers and management predicted the chance of a catastrophic failure resulting in the death of the crew as ranging from 1 in 100 launches to as rare as 1 in 100,000. Following the loss of two Space Shuttle missions, the risks for the initial missions were reevaluated, and the chance of a catastrophic loss of the vehicle and crew was found to be as high as 1 in 9. NASA management was criticized afterwards for accepting increased risk to the crew in exchange for higher mission rates. Both the ''Rogers Commission Report, Challenger'' and ''Columbia Accident Investigation Board, Columbia '' reports explained that NASA culture had failed to keep the crew safe by not objectively evaluating the potential risks of the missions.


Retirement

The Space Shuttle retirement was announced in January 2004. President George W. Bush announced his Vision for Space Exploration, which called for the retirement of the Space Shuttle once it completed construction of the ISS. To ensure the ISS was properly assembled, the contributing partners determined the need for 16 remaining assembly missions in March 2006. One additional Hubble Space Telescope servicing mission was approved in October 2006. Originally, STS-134 was to be the final Space Shuttle mission. However, the ''Columbia'' disaster resulted in additional orbiters being prepared for STS-3xx, launch on need in the event of a rescue mission. As ''Atlantis'' was prepared for the final launch-on-need mission, the decision was made in September 2010 that it would fly as STS-135 with a four-person crew that could remain at the ISS in the event of an emergency. STS-135 launched on July 8, 2011, and landed at the KSC on July 21, 2011, at 5:57 a.m. EDT (09:57 UTC). From then until the launch of SpaceX Dragon 2#Crew Dragon, Crew Dragon Demo-2 on May 30, 2020, the US launched its astronauts aboard Russian Soyuz spacecraft. Following each orbiter's final flight, it was processed to make it safe for display. The OMS and RCS systems used presented the primary dangers due to their toxic hypergolic propellant, and most of their components were permanently removed to prevent any dangerous outgassing. ''Atlantis'' is on display at the Kennedy Space Center Visitor Complex, ''Discovery'' is at the Steven F. Udvar-Hazy Center, Udvar-Hazy Center, ''Endeavour'' is on display at the California Science Center, and ''Enterprise'' is displayed at the Intrepid Sea-Air-Space Museum. Components from the orbiters were transferred to the US Air Force, ISS program, and Russian and Canadian governments. The engines were removed to be used on the Space Launch System, and spare RS-25 nozzles were attached for display purposes.


In popular culture

The U.S. Postal Service has released several postage issues that depict the Space Shuttle. The first such stamps were issued in 1981, and are on display at the National Postal Museum.


See also


Notes


References


External links


NSTS 1988 Reference manual


*[https://web.archive.org/web/19991008105340/http://spaceflight.nasa.gov/shuttle/ NASA Human Spaceflight – Shuttle]
High resolution spherical panoramas over, under, around and through ''Discovery,'' ''Atlantis'' and ''Endeavour''
* {{Authority control Space Shuttle program, * Aircraft first flown in 1977 American inventions Articles containing video clips Crewed spacecraft Historic American Engineering Record in Texas NASA space launch vehicles Partially reusable space launch vehicles Reusable spaceflight technology Vehicles introduced in 1981