Space Shuttle
On the 24th of September 1966, NASA and the Air Force released a joint study concluding that a new vehicle was required to satisfy their respective future demands. The head of the NASA Office of Manned Space Flight, George Mueller, announced the plan for a reusable shuttle on the 10th of August 1968. NASA issued a request for proposal for designs of the Integral Launch and Reentry Vehicle on the 30th of October 1968. In December 1968, NASA created the Space Shuttle Task Group to determine the optimal design for a reusable spacecraft. Study contracts were issued to General Dynamics, Lockheed, McDonnell Douglas, and North American Rockwell. In July 1969, the Space Shuttle Task Group issued a report that determined the Shuttle would support short-duration crewed missions and space station operations. The report also created three classes of a future reusable shuttle: Class I, Class II, and Class III. 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. On the 5th of January 1972, President Richard Nixon approved the Shuttle. NASA decided on its final design in March 1972. The development of the Space Shuttle Main Engine remained the responsibility of Rocketdyne. The contract was issued in July 1971, and updated SSME specifications were submitted to Rocketdyne that April. The following August, NASA awarded the contract to build the orbiter to North American Rockwell. In August 1973, NASA awarded the external tank contract to Martin Marietta. In November 1973, the solid-rocket booster contract went to Morton Thiokol. On the 4th of June 1974, Rockwell began construction on the first orbiter, OV-101, dubbed Constitution. It was later renamed Enterprise. Construction was completed on the 17th of September 1976. Enterprise was moved to the Edwards Air Force Base to begin testing. Rockwell constructed the Main Propulsion Test Article, which was a structural truss mounted to the external tank with three RS-25 engines attached. It was tested at the National Space Technology Laboratory to ensure that the engines could safely run through the launch profile. Rockwell conducted mechanical and thermal stress tests on Structural Test Article 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. 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. Previous NASA spacecraft had used ablative heat shields, but those could not be reused. NASA chose to use ceramic tiles for thermal protection. Construction began on Columbia on the 27th of March 1975. It was delivered to the Kennedy Space Center on the 25th of March 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 the 5th of January 1979, NASA commissioned a second orbiter. Later that month, Rockwell began converting Structural Test Article 099 to OV-099, later named Challenger. On the 29th of January 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. 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.
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, which provided thrust during launch. It also contained the Orbital Maneuvering System, which allowed the orbiter to achieve, alter, and exit its orbit once in space. Its double-delta wings were long, and were swept 81 degrees at the inner leading edge and 45 degrees at the outer leading edge. Each wing had an inboard and outboard elevon to provide flight control during reentry. A flap located between the wings controlled pitch. The orbiter's vertical stabilizer was swept backwards at 45 degrees and contained a rudder that could split to act as a speed brake. The vertical stabilizer also contained a two-part drag parachute system to slow the orbiter after landing. The orbiter used retractable landing gear with a nose landing gear and two main landing gear. The main landing gear contained two brake assemblies each. The nose landing gear contained an electro-hydraulic steering mechanism. The instrument panels contained over 2,100 displays and controls. The commander and pilot were both equipped with a heads-up display and a Rotational Hand Controller to gimbal the engines during powered flight. Both seats also had rudder controls. The orbiter vehicles were originally installed with the Multifunction CRT Display System to display and control flight information. In 1998, Atlantis was upgraded with the Multifunction Electronic Display System. This glass cockpit upgrade replaced the eight MCDS display units with 11 multifunction colored digital screens. MEDS was flown for the first time in May 2000 on STS-101. The other orbiter vehicles were upgraded to it. The aft section of the flight deck contained windows looking into the payload bay. It also had an RHC to control the Remote Manipulator System 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. An internal airlock was installed as an external airlock in the payload bay on Discovery, Atlantis, and Endeavour to improve docking with Mir and the ISS. The Space Shuttle's fly-by-wire control system was entirely reliant on its main computer, the Data Processing System. The DPS controlled the flight controls and thrusters on the orbiter. It also controlled the ET and SRBs during launch. The DPS consisted of five general-purpose computers, two magnetic tape mass memory units, and the associated sensors. The original GPC used was the IBM AP-101B. From 1991 to 1993, the orbiter vehicles were upgraded to the AP-101S. This improved the memory and processing capabilities. Four of the GPCs were loaded with the Primary Avionics Software System. During ascent, maneuvering, reentry, and landing, the four PASS GPCs functioned identically to produce quadruple redundancy. In case of a software error, a fifth GPC ran the Backup Flight System. After achieving orbit, the crew would switch some of the GPC functions from guidance, navigation, and control to systems management and payload.
The Space Shuttle flew from the 12th of April 1981, until the 21st of July 2011. Throughout the program, the Space Shuttle had 135 missions, of which 133 returned safely. On the 12th of April 1981, the Space Shuttle launched for the first time. It was piloted by John Young and Robert Crippen. During the two-day mission, Young and Crippen tested equipment on board the shuttle. They 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. They determined there was no damage. Columbia reentered the atmosphere and landed at Edwards AFB on April 14. On the 4th of July 1982, STS-4, flown by Ken Mattingly and Henry Hartsfield, landed on a concrete runway at Edwards AFB. President Ronald Reagan and his wife Nancy met the crew. After STS-4, NASA declared its Space Transportation System operational. The orbiter vehicle's reentry was defined as starting at an altitude of 400,000 feet 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. This was controlled by means of angle of attack, as well as bank angle. A series of roll reversals were performed to control azimuth while banking. At an altitude of 30,000 feet, 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. They began lowering the angle-of-attack to 36 degrees. The approach and landing phase began when the orbiter vehicle was at an altitude of 1,500 feet and traveling at 220 miles per hour. The orbiter followed either a 20 degree or 18 degree glideslope and descended at approximately 175 miles per hour. The speed brake was used to keep a continuous speed. Crew initiated a pre-flare maneuver to a 1.5 degree glideslope at an altitude of 100 feet. The landing gear was deployed 10 seconds prior to touchdown. A final flare maneuver reduced the orbiter vehicle's descent rate to 7 feet per second. Touchdown occurred at 215 miles per hour, 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. They began wheel braking when the orbiter was traveling slower than 190 miles per hour. The primary Space Shuttle landing site was the Shuttle Landing Facility 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. It required extensive post-processing after exposure to the gypsum-rich sand.
On the 28th of January 1986, STS-51-L disintegrated 73 seconds after launch due to the failure of the right SRB. This killed 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. This led 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 50 degrees Fahrenheit had been ignored by NASA managers. On the 1st of February 2003, Columbia disintegrated during re-entry, killing all seven of the STS-107 crew. This happened because of damage to the 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. 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. They refused the request for the spacewalk. Thus, the feasibility of scenarios for astronaut repair or rescue by Atlantis were not considered by NASA management at the time. 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. 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 Challenger and Columbia reports explained that NASA culture had failed to keep the crew safe by not objectively evaluating the potential risks of the missions.
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. This 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. Development estimates made in 1972 projected a per-pound cost of payload as low as $1,109 in 2012 dollars. But the actual payload costs, not including the costs for research and development, were $37,207 in 2012 dollars 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. In 1982, NASA published an estimate of $260 million in 2012 dollars per flight. This 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 dollars 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 dollars. Accounting for the entire Space Shuttle program budget, the per-launch cost was $1.642 billion in 2012 dollars. 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 reuse 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. The Space Shuttle did not fly the intended 24 missions per year as initially predicted by NASA.
Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope. They conducted science experiments in orbit. They participated in the Shuttle-Mir program with Russia. They also participated in the construction and servicing of the International Space Station. The Space Shuttle fleet's total mission time was 1,323 days. The Spacelab module was a European-funded pressurized laboratory carried within the payload bay. It allowed for scientific research while in orbit. The Spacelab equipment was primarily stored in pallets. These provided storage for both experiments as well as computer and power equipment. Spacelab hardware was flown on 28 missions through 1999. It studied subjects including astronomy, microgravity, radar, and life sciences. Spacelab hardware also supported missions such as Hubble Space Telescope servicing and space station resupply. The Spacelab module was tested on STS-2 and STS-3. The first full mission was on STS-9. Beginning with STS-71, 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. Most missions involved staying in orbit several days to two weeks. 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. The Remote Manipulator System, also known as Canadarm, was a mechanical arm attached to the cargo bay. It could be used to grasp and manipulate payloads. It served as a mobile platform for astronauts conducting an EVA. The RMS was built by the Canadian company Spar Aerospace. It 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 15 meters. This was later improved to 18 meters.
The Space Shuttle retirement was announced in January 2004. President George W. Bush announced his Vision for Space Exploration. It 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 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. STS-135 launched on the 8th of July 2011, and landed at the KSC on the 21st of July 2011, at 5:57 a.m. EDT. From then until the launch of Crew Dragon Demo-2 on the 30th of May 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. Most of their components were permanently removed to prevent any dangerous outgassing. Atlantis is on display at the Kennedy Space Center Visitor Complex in Florida. Discovery is on display at the Steven F. Udvar-Hazy Center in Virginia. Endeavour is on display at the California Science Center in Los Angeles. Enterprise is displayed at the Intrepid Museum in New York. 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 future missions.
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Common questions
When was the Space Shuttle program officially approved by President Richard Nixon?
President Richard Nixon approved the Space Shuttle on the 5th of January 1972. NASA decided on its final design in March 1972 following this approval.
What were the names and construction dates for all five Space Shuttle orbiters?
Construction began on OV-101, later named Enterprise, on the 4th of June 1974 and completed on the 17th of September 1976. Construction started on Columbia on the 27th of March 1975. NASA commissioned a second orbiter on the 5th of January 1979 which became Challenger. NASA ordered Discovery and Atlantis on the 29th of January 1979. Construction of Endeavour began in February 1982 after the loss of Challenger.
How many total missions did the Space Shuttle fly and when did the program end?
The Space Shuttle flew from the 12th of April 1981 until the 21st of July 2011. Throughout the program the Space Shuttle had 135 missions with 133 returning safely. The final mission STS-135 landed at the Kennedy Space Center on the 21st of July 2011.
Why did the Space Shuttle Challenger disaster occur on the 28th of January 1986?
STS-51-L disintegrated 73 seconds after launch due to the failure of the right solid rocket booster O-ring seal caused by low temperature. Hot combustion gases escaped between booster sections and burned through the external tank leading to catastrophic events that killed all seven astronauts on board.
What was the actual per-launch cost of the Space Shuttle compared to initial estimates?
Development estimates made in 1972 projected a per-pound payload cost as low as $1,109 but actual costs were $37,207 per pound. Accounting for the entire Space Shuttle program budget the per-launch cost reached $1.642 billion in 2012 dollars.