Space Shuttle Discovery begins liftoff at the start of STS-120. |
|
| Function | Manned orbital launch and reentry |
|---|---|
| Manufacturer | United Space Alliance: Thiokol/Alliant Techsystems (SRBs) Lockheed Martin/Martin Marietta (ET) Boeing/Rockwell (orbiter) |
| Country of origin | United States of America |
| Size | |
| Height | 56.1 m (184.2 ft) |
| Diameter | 8.7 m (28.5 ft) |
| Mass | 2,030 t (4,470,000 lbm) |
| Capacity | |
| Payload to LEO | 24,400 kg (53,600 lb) |
| Payload to GTO |
3,810 kg (8,390 lbm) |
| Payload to Polar orbit |
12,700 kg (28,000 lb) |
| Payload to Landing[1] |
14,400 kg (32,000 lb)[1] (Return Payload) |
| Launch history | |
| Status | Retired |
| Launch sites | LC-39, Kennedy Space Center SLC-6, Vandenberg AFB (unused) |
| Total launches | 135 |
| Successes | 134 successful launches 133 successful re-entries |
| Failures | 2: (launch failure, Challenger); and (re-entry failure, Columbia) |
| Maiden flight | April 12, 1981 |
| Last flight | July 21, 2011 |
| Notable payloads | Tracking and Data Relay Satellites Spacelab Great Observatories (including Hubble) Galileo, Magellan, Ulysses Mir Docking Module ISS components |
| Boosters (Stage 0) - Solid Rocket Boosters | |
| No. boosters | 2 |
| Engines | 1 solid |
| Thrust | 12.5 MN each, sea level liftoff (2,800,000 lbf) |
| Specific impulse | 269 s |
| Burn time | 124 s |
| Fuel | solid |
| First stage - External Tank | |
| Engines | 3 SSMEs located on Orbiter |
| Thrust | 5.45220 MN total, sea level liftoff (1,225,704 lbf) |
| Specific impulse | 455 s |
| Burn time | 480 s |
| Fuel | LOX/LH2 |
| Second stage - Orbiter | |
| Engines | 2 OME |
| Thrust | 53.4 kN combined total vacuum thrust (12,000 lbf) |
| Specific impulse | 316 s |
| Burn time | 1,250 s |
| Fuel | MMH/N2O4 |
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons. Major missions included launching numerous satellites and interplanetary probes,[2] conducting space science experiments, and 37 missions constructing and servicing the International Space Station. A major international contribution was the Spacelab payload suite, from the ESA.
Major components included the orbiters, recoverable boosters, external tanks, payloads, and supporting infrastructure — orchestrated by thousands of people.
Contents |
The Space Shuttle was a partially reuseable[3] launch system and orbital spacecraft operated by the U.S. National Aeronautics and Space Administration (NASA) for human spaceflight missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons. The first of four orbital test flights occurred in 1981 leading to operational flights beginning in 1982, all launched from the Kennedy Space Center, Florida. The system was retired from service in 2011 after 135 missions;[4] on July 8, 2011, with Space Shuttle Atlantis performing that 135th launch - the final launch of the three-decade Shuttle program.[5] The program ended after Atlantis landed at the Kennedy Space Center on July 21, 2011. Major missions included launching numerous satellites and interplanetary probes,[2] conducting space science experiments, and servicing and construction of space stations. Enterprise was a prototype orbiter used for atmospheric testing during development in the 1970s, and lacked engines and heat shield. Five space-worthy orbiters were built—two were destroyed in accidents and the others have been retired.
It was used for orbital space missions by NASA, the U.S. Department of Defense, the European Space Agency, Japan, and Germany.[6][7] The United States funded Space Transportation System (STS) development and Shuttle operations except for Spacelab D1 and D2 — sponsored by West Germany and reunified Germany respectively.[6][8][9][10][11] In addition, SL-J was partially funded by Japan.[7]
At launch, it consisted of the "stack", including a dark orange-colored external tank (ET);[12][13] two white, slender Solid Rocket Boosters (SRBs); and the Orbiter Vehicle (OV), which contained the crew and payload. Some payloads were launched into higher orbits with either of two different booster stages developed for the STS (single-stage Payload Assist Module or two-stage Inertial Upper Stage). The Space Shuttle was stacked in the Vehicle Assembly Building and the stack mounted on a mobile launch platform held down by four explosive bolts on each SRB which are detonated at launch.[14]
The Shuttle stack launched vertically like a conventional rocket. It lifted off under the power of its two SRBs and three main engines, which were fueled by liquid hydrogen and liquid oxygen from the external tank. The Space Shuttle had a two-stage ascent. The SRBs provided additional thrust during liftoff and first-stage flight. About two minutes after liftoff, explosive bolts were fired, releasing the SRBs, which then parachuted into the ocean, to be retrieved by ships for refurbishment and reuse. The Shuttle orbiter and external tank continued to ascend on an increasingly horizontal flight path under power from its main engines. Upon reaching 17,500 mph (7.8 km/s), necessary for low Earth orbit, the main engines were shut down. The external tank was then jettisoned to burn up in the atmosphere.[15] After jettisoning the external tank, the orbital maneuvering system (OMS) engines were used to adjust the orbit.
The orbiter carried people and payload such as satellites or space station parts into low Earth orbit, into the Earth's upper atmosphere or thermosphere.[16] Usually, five to seven crew members rode in the orbiter. Two crew members, the commander and pilot, were sufficient for a minimal flight, as in the first four "test" flights, STS-1 through STS-4. The typical payload capacity was about 22,700 kilograms (50,000 lb), but could be increased depending on the choice of launch configuration. The orbiter carried its payload in a large cargo bay with doors that opened along the length of its top, a feature which made the Space Shuttle unique among spacecraft. This feature made possible the deployment of large satellites such as the Hubble Space Telescope, and also the capture and return of large payloads back to Earth.
When the orbiter's space mission was complete, it fired its OMS thrusters to drop out of orbit and re-enter the lower atmosphere.[16] During descent, the orbiter passed through different layers of the atmosphere and decelerates from hypersonic speed primarily by aerobraking. In the lower atmosphere and landing phase, it was more like a glider but with reaction control system (RCS) thrusters and fly-by wire-controlled hydraulically-actuated flight surfaces controlling its descent. It landed on a long runway as a spaceplane. The aerodynamic shape was a compromise between the demands of radically different speeds and air pressures during re-entry, hypersonic flight, and subsonic atmospheric flight. As a result, the orbiter had a relatively high sink rate at low altitudes, and it transitioned during re-entry from using RCS thrusters at very high altitudes to flight surfaces in the lower atmosphere.
The formal design of what became the Space Shuttle began with "Phase A" contract design studies issued in the late 1960s. However, conceptualization began two decades earlier, before the Apollo program of the 1960s. One of the places the concept of a spacecraft returning from space to a horizontal landing originated was within NACA, in 1954, in the form of an aeronautics research experiment later named the X-15. The NACA proposal was submitted by Walter Dornberger.
In 1958, the X-15 concept further developed into proposal to launch a X-15 into space, and another X-series spaceplane proposal, called the X-20, which was not constructed, as well as variety of aerospace plane concepts and studies. Neil Armstrong was selected to pilot both the X-15 and the X-20. Though the X-20 was not built, another spaceplane similar to the X-20 was built several years later and delivered to NASA in January 1966 called the HL-10 ("HL" indicated "horizontal landing").
In the mid-1960s, the US Air Force conducted a series of classified studies on next-generation space transportation systems and concluded that semi-reusable designs were the cheapest choice. It proposed a development program with an immediate start on a "Class I" vehicle with expendable boosters, followed by slower development of a "Class II" semi-reusable design and perhaps a "Class III" fully reusable design later. In 1967, George Mueller held a one-day symposium at NASA headquarters to study the options. Eighty people attended and presented a wide variety of designs, including earlier Air Force designs as the Dyna-Soar (X-20).
In 1968, NASA officially began work on what was then known as the Integrated Launch and Re-entry Vehicle (ILRV). At the same time, NASA held a separate Space Shuttle Main Engine (SSME) competition. NASA offices in Houston and Huntsville jointly issued a Request for Proposal (RFP) for ILRV studies to design a spacecraft that could deliver a payload to orbit but also re-enter the atmosphere and fly back to Earth. For example, one of the responses was for a two-stage design, featuring a large booster and a small orbiter, called the DC-3, one of several Phase A Shuttle designs. After the aforementioned "Phase A" studies, B, C, and D phases progressively evaluated in-depth designs up to 1972. In the final design, the bottom stage was recoverable solid rocket boosters, and the top stage used an expendable external tank.[17]
In 1969, President Richard Nixon decided to support proceeding with Space Shuttle development. A series of development programs and analysis refined the basic design, prior to full development and testing. In August 1973, the X-24B proved that an unpowered spaceplane could re-enter Earth's atmosphere for a horizontal landing.
Across the Atlantic, European ministers met in Belgium in 1973 to authorize Western Europe's manned orbital project and its main contribution to Space Shuttle — the Spacelab program.[18] Spacelab would provide a multi-disciplinary orbital space laboratory and additional space equipment for the Shuttle.[18]
The Space Shuttle was the first operational orbital spacecraft designed for reuse. It carried different payloads to low Earth orbit, provided crew rotation for the International Space Station (ISS), and performed servicing missions. The orbiter could also recover satellites and other payloads from orbit and return them to Earth. Each Shuttle was designed for a projected lifespan of 100 launches or ten years of operational life, although this was later extended. The person in charge of designing the STS was Maxime Faget, who had also overseen the Mercury, Gemini, and Apollo spacecraft designs. The crucial factor in the size and shape of the Shuttle Orbiter was the requirement that it be able to accommodate the largest planned commercial and military satellites, and have the cross-range recovery range to meet the requirement for classified USAF missions for a once-around abort from a launch to a polar orbit. Factors involved in opting for solid rockets and an expendable fuel tank included the desire of the Pentagon to obtain a high-capacity payload vehicle for satellite deployment, and the desire of the Nixon administration to reduce the costs of space exploration by developing a spacecraft with reusable components.
Each Space Shuttle is a reusable launch system that is composed of three main assemblies: the reusable Orbiter Vehicle (OV), the expendable external tank (ET), and the two reusable solid rocket boosters (SRBs).[19] Only the orbiter entered orbit shortly after the tank and boosters are jettisoned. The vehicle was launched vertically like a conventional rocket, and the orbiter glided to a horizontal landing like an airplane, after which it was refurbished for reuse. The SRBs parachuted to splashdown in the ocean where they were towed back to shore and refurbished for later Shuttle missions.
Five space-worthy orbiters were built: Columbia (OV-102), Challenger (OV-099), Discovery (OV-103), Atlantis (OV-104), and Endeavour (OV-105). A mock-up, Inspiration (OV-100), currently stands at the entrance to the Astronaut Hall of Fame. An additional craft, Enterprise (OV-101), was not built for orbital space flight, and was used only for testing gliding and landing. Enterprise was originally intended to be made fully space-worthy after use for the approach and landing test (ALT) program, but it was found more economical to upgrade the structural test article STA-099 into orbiter Challenger (OV-099). Challenger disintegrated 73 seconds after launch in 1986, and Endeavour was built as a replacement for Challenger from structural spare components. Columbia broke apart during re-entry in 2003. Building Space Shuttle Endeavour cost about US$1.7 billion. One Space Shuttle launch costs around $450 million.[20]
Roger A. Pielke, Jr. has estimated that the Space Shuttle program has cost about US$170 billion (2008 dollars) through early 2008. This works out to an average cost per flight of about US$1.5 billion.[21] However, two missions were paid for by Germany, Spacelab D1 and D2 (D for Deutschland) with a payload control center in Oberpfaffenhofen, Germany.[22][23] D1 was the first time that control of a manned STS mission payload was not in U.S. hands.[6]
At times, the orbiter itself was referred to as the Space Shuttle. Technically, this was a slight misnomer, as the actual "Space Transportation System" (Space Shuttle) was the combination of the orbiter, the external tank, and the two solid rocket boosters. Combined, these were referred to as the "stack"; the components were assembled in the Vehicle Assembly Building, originally built to assemble the Apollo Saturn V rocket.
Responsibility for the Shuttle components was spread among multiple NASA field centers. The Kennedy Space Center was responsible for launch, landing and turnaround operations for equatorial orbits (the only orbit profile actually used in the program), the US Air Force at the Vandenberg Air Force Base was responsible for launch, landing and turnaround operations for polar orbits (though this was never used), the Johnson Space Center served as the central point for all Shuttle operations, the Marshall Space Flight Center was responsible for the main engines, external tank, and solid rocket boosters, the John C. Stennis Space Center handled main engine testing, and the Goddard Space Flight Center managed the global tracking network.[24]
The orbiter resembles a conventional aircraft, with double-delta wings swept 81° at the inner leading edge and 45° at the outer leading edge. Its vertical stabilizer's leading edge is swept back at a 50° angle. The four elevons, mounted at the trailing edge of the wings, and the rudder/speed brake, attached at the trailing edge of the stabilizer, with the body flap, controlled the orbiter during descent and landing.
The orbiter's payload bay measures 15 by 60 feet (4.6 by 18 m), comprising most of the fuselage. Information declassified in 2011 showed that the payload bay was designed specifically to accommodate the KH-9 HEXAGON spy satellite operated by the National Reconnaissance Office.[25] Two mostly symmetrical lengthwise payload bay doors hinged on either side of the bay comprise its entire top. Payloads are generally loaded horizontally into the bay while the orbiter is oriented vertically on the launch pad and unloaded vertically in the near-weightless orbital environment by the orbiter's robotic remote manipulator arm (under astronaut control), EVA astronauts, or under the payloads' own power (as for satellites attached to a rocket "upper stage" for deployment.)
Three Space Shuttle Main Engines (SSMEs) are mounted on the orbiter's aft fuselage in a triangular pattern. The engine nozzles can swivel 10.5 degrees up and down, and 8.5 degrees from side to side during ascent to change the direction of their thrust to steer the Shuttle. The orbiter structure is made primarily from aluminum alloy, although the engine structure is made primarily from titanium alloy.
The space-capable orbiters built were OV-102 Columbia, OV-099 Challenger, OV-103 Discovery, OV-104 Atlantis, and OV-105 Endeavour.[26]
The main function of the Space Shuttle external tank was to supply the liquid oxygen and hydrogen fuel to the main engines. It was also the backbone of the launch vehicle, providing attachment points for the two Solid Rocket Boosters and the Orbiter. The external tank was the only part of the Shuttle system that was not reused. Although the external tanks were always discarded, it was possible to take them into orbit and re-use them (such as for incorporation into a space station).[15][28]
Two solid rocket boosters (SRBs) each provided 12.5 million newtons (2.8 million lbf) of thrust at liftoff,[29] which was 83% of the total thrust needed for liftoff. The SRBs were jettisoned two minutes after launch at a height of about 150,000 feet (46 km), and then deployed parachutes and landed in the ocean to be recovered.[30] The SRB cases were made of steel about ½ inch (13 mm) thick.[31] The Solid Rocket Boosters were re-used many times; the casing used in Ares I engine testing in 2009 consisted of motor cases that had been flown, collectively, on 48 Shuttle missions, including STS-1.[32]
The orbiter could be used in conjunction with a variety of add-ons depending on the mission. This has included orbital laboratories (Spacelab, Spacehab), boosters for launching payloads farther into space (Inertial Upper Stage, Payload Assist Module), and other functions, such as provided by Extended Duration Orbiter, Multi-Purpose Logistics Modules, or Canadarm (RMS). An upper-stage called Transfer Orbit Stage (Orbital Science Corp. TOS-21) was also used once.[33] Other types of systems and racks were part of the modular Spacelab system — pallets, igloo, IPS, etc., which also supported special missions such as SRTM.[34]
A major component of the Space Shuttle Program was Spacelab, primarily contributed by a consortium of European countries, and operated in conjunction with the United States and international partners.[34] Supported by a modular system of pressurized modules, pallets, and systems, Spacelab missions executed on multidisciplinary science, orbital logistics, international cooperation.[34] Over 29 missions flew on subjects ranging from astronomy, microgravity, radar, and life sciences, to name a few.[34] Spacelab hardware also supported missions such as Hubble (HST) servicing and space station resupply.[34] STS-2 and STS-3 provided testing, and the first full mission was Spacelab-1 (STS-9) launched on November 28, 1983.[34]
Spacelab formally began in 1973, after a meeting in Brussels, Belgium, by European heads of state.[18] Within the decade, Spacelab would go into orbit and provide not only Europe, but also the United States, with an orbital workshop and hardware system.[18] International cooperation, science, and exploration were realized on Spacelab.[34]
The Shuttle was one of the earliest craft to use a computerized fly-by-wire digital flight control system. This means no mechanical or hydraulic linkages connected the pilot's control stick to the control surfaces or reaction control system thrusters.
A concern with digital fly-by-wire systems is reliability. Considerable research went into the Shuttle computer system. The Shuttle used five identical redundant IBM 32-bit general purpose computers (GPCs), model AP-101, constituting a type of embedded system. Four computers ran specialized software called the Primary Avionics Software System (PASS). A fifth backup computer ran separate software called the Backup Flight System (BFS). Collectively they were called the Data Processing System (DPS).[35][36]
The design goal of the Shuttle's DPS was fail-operational/fail-safe reliability. After a single failure, the Shuttle could still continue the mission. After two failures, it could still land safely.
The four general-purpose computers operated essentially in lockstep, checking each other. If one computer failed, the three functioning computers "voted" it out of the system. This isolated it from vehicle control. If a second computer of the three remaining failed, the two functioning computers voted it out. In the unlikely case of two out of four computers simultaneously failed (a two-two split), one group was to be picked at random.
The Backup Flight System (BFS) was separately developed software running on the fifth computer, used only if the entire four-computer primary system failed. The BFS was created because although the four primary computers were hardware redundant, they all ran the same software, so a generic software problem could crash all of them. Embedded system avionic software was developed under totally different conditions from public commercial software: the number of code lines was tiny compared to a public commercial software, changes were only made infrequently and with extensive testing, and many programming and test personnel worked on the small amount of computer code. However, in theory it could have still failed, and the BFS existed for that contingency. While the BFS could run in parallel with PASS, the BFS never engaged to take over control from PASS during any Shuttle mission.
The software for the Shuttle computers was written in a high-level language called HAL/S, somewhat similar to PL/I. It is specifically designed for a real time embedded system environment.
The IBM AP-101 computers originally had about 424 kilobytes of magnetic core memory each. The CPU could process about 400,000 instructions per second. They had no hard disk drive, and load software from magnetic tape cartridges.
In 1990, the original computers were replaced with an upgraded model AP-101S, which had about 2.5 times the memory capacity (about 1 megabyte) and three times the processor speed (about 1.2 million instructions per second). The memory was changed from magnetic core to semiconductor with battery backup.
Early Shuttle missions, starting in November 1983, took along the GRiD Compass, arguably one of the first laptop computers. The GRiD was given the name SPOC, for Shuttle Portable Onboard Computer. Use on the Shuttle required both hardware and software modifications which were incorporated into later versions of the commercial product. It was used to monitor and display the Shuttle's ground position, path of the next two orbits, show where the Shuttle had line of sight communications with ground stations, and determine points for location-specific observations of the Earth. The Compass sold poorly, as it cost at least US$8000, but it offered unmatched performance for its weight and size.[37] NASA was one of its main customers.[38]
The typeface used on the Space Shuttle Orbiter is Helvetica.[39] On the side of the Shuttle between the cockpit windows and the cargo bay doors is the name of the orbiter. Underneath the rear of the cargo bay doors have been various NASA insignia, the text "United States" and a flag of the United States.
Columbia, being the first orbiter built, had a flag of the United States on the left wing and a "USA" in bold on the left wing and the word "Columbia" on the Payload Bay Doors from STS-1 to STS-9. Afterwards it was moved to the usual position as on the other orbiters. Challenger wore the letters "USA" and the flag on the left wing, with the NASA worm lettering and the word "Challenger" below it on the right wing. Challenger also had a different hatch tile pattern. As a result of the early loss of Challenger, it is the only orbiter never to wear the "meatball" logo on its left wing. The subsequent orbiters benefited from technological advances in tile positioning and were largely similar.
The Space Shuttle was initially developed in the 1970s,[40] but received many upgrades and modifications afterward for improvements ranging from performance and reliability to safety. Internally, the Shuttle remained largely similar to the original design, with the exception of the improved avionics computers. In addition to the computer upgrades, the original analog primary flight instruments were replaced with modern full-color, flat-panel display screens, called a glass cockpit, which is similar to those of contemporary airliners. With the coming of the ISS, the orbiter's internal airlocks were replaced with external docking systems to allow for a greater amount of cargo to be stored on the Shuttle's mid-deck during station resupply missions.
The Space Shuttle Main Engines (SSMEs) had several improvements to enhance reliability and power. This explains phrases such as "Main engines throttling up to 104 percent." This did not mean the engines were being run over a safe limit. The 100 percent figure was the original specified power level. During the lengthy development program, Rocketdyne determined the engine was capable of safe reliable operation at 104 percent of the originally specified thrust. NASA could have rescaled the output number, saying in essence 104 percent is now 100 percent. To clarify this would have required revising much previous documentation and software, so the 104 percent number was retained. SSME upgrades were denoted as "block numbers", such as block I, block II, and block IIA. The upgrades improved engine reliability, maintainability and performance. The 109% thrust level was finally reached in flight hardware with the Block II engines in 2001. The normal maximum throttle was 104 percent, with 106 percent or 109 percent used for mission aborts.
For the first two missions, STS-1 and STS-2, the external tank was painted white to protect the insulation that covers much of the tank, but improvements and testing showed that it was not required. The weight saved by not painting the tank resulted in an increase in payload capability to orbit.[41] Additional weight was saved by removing some of the internal "stringers" in the hydrogen tank that proved unnecessary. The resulting "light-weight external tank" has been used on the vast majority of Shuttle missions. STS-91 saw the first flight of the "super light-weight external tank". This version of the tank is made of the 2195 aluminum-lithium alloy. It weighs 3.4 metric tons (7,500 lb) less than the last run of lightweight tanks. As the Shuttle was not flown unmanned, each of these improvements was "tested" on operational flights.
The SRBs (Solid Rocket Boosters) underwent improvements as well. Design engineers added a third O-ring seal to the joints between the segments after the 1986 Space Shuttle Challenger disaster.
Several other SRB improvements were planned to improve performance and safety, but never came to be. These culminated in the considerably simpler, lower cost, probably safer and better-performing Advanced Solid Rocket Booster. These rockets entered production in the early to mid-1990s to support the Space Station, but were later canceled to save money after the expenditure of $2.2 billion.[42] The loss of the ASRB program resulted in the development of the Super LightWeight external Tank (SLWT), which provided some of the increased payload capability, while not providing any of the safety improvements. In addition, the Air Force developed their own much lighter single-piece SRB design using a filament-wound system, but this too was canceled.
STS-70 was delayed in 1995, when woodpeckers bored holes in the foam insulation of Discovery's external tank. Since then, NASA has installed commercial plastic owl decoys and inflatable owl balloons which had to be removed prior to launch.[43] The delicate nature of the foam insulation had been the cause of damage to the Thermal Protection System, the tile heat shield and heat wrap of the orbiter. NASA remained confident that this damage, while it was the primary cause of the Space Shuttle Columbia disaster on February 1, 2003, would not jeopardize the completion the International Space Station (ISS) in the projected time allotted.
A cargo-only, unmanned variant of the Shuttle was variously proposed and rejected since the 1980s. It was called the Shuttle-C, and would have traded re-usability for cargo capability, with large potential savings from reusing technology developed for the Space Shuttle. Another proposal was to convert the payload bay into a passenger area, with proposals ranging from 30 to 74 seats, three days in orbit, and 1.5 million USD a seat.[44]
On the first four Shuttle missions, astronauts wore modified US Air Force high-altitude full-pressure suits, which included a full-pressure helmet during ascent and descent. From the fifth flight, STS-5, until the loss of Challenger, one-piece light blue nomex flight suits and partial-pressure helmets were worn. A less-bulky, partial-pressure version of the high-altitude pressure suits with a helmet was reinstated when Shuttle flights resumed in 1988. The Launch-Entry Suit ended its service life in late 1995, and was replaced by the full-pressure Advanced Crew Escape Suit (ACES), which resembled the Gemini space suit in design, but retained the orange color of the Launch-Entry Suit.
To extend the duration that orbiters could stay docked at the ISS, the Station-to-Shuttle Power Transfer System (SSPTS) was installed. The SSPTS allowed these orbiters to use power provided by the ISS to preserve their consumables. The SSPTS was first used successfully on STS-118.
Orbiter specifications[45] (for Endeavour, OV-105)
External tank specifications (for SLWT)
Solid Rocket Booster specifications
System Stack specifications
All Space Shuttle missions were launched from Kennedy Space Center (KSC). The weather criteria used for launch included, but were not limited to: precipitation, temperatures, cloud cover, lightning forecast, wind, and humidity.[49] The Shuttle was not launched under conditions where it could have been struck by lightning. Aircraft are often struck by lightning with no adverse effects because the electricity of the strike is dissipated through its conductive structure and the aircraft is not electrically grounded. Like most jet airliners, the Shuttle was mainly constructed of conductive aluminum, which would normally shield and protect the internal systems. However, upon liftoff the Shuttle sent out a long exhaust plume as it ascended, and this plume could have triggered lightning by providing a current path to ground. The NASA Anvil Rule for a Shuttle launch stated that an anvil cloud could not appear within a distance of 10 nautical miles.[50] The Shuttle Launch Weather Officer monitored conditions until the final decision to scrub a launch was announced. In addition, the weather conditions had to be acceptable at one of the Transatlantic Abort Landing sites (one of several Space Shuttle abort modes) to launch as well as the solid rocket booster recovery area.[49][51] While the Shuttle might have safely endured a lightning strike, a similar strike caused problems on Apollo 12, so for safety NASA chose not to launch the Shuttle if lightning was possible (NPR8715.5).
Historically, the Shuttle was not launched if its flight would run from December to January (a year-end rollover or YERO). Its flight software, designed in the 1970s, was not designed for this, and would require the orbiter's computers be reset through a change of year, which could cause a glitch while in orbit. In 2007, NASA engineers devised a solution so Shuttle flights could cross the year-end boundary.[52]
On the day of a launch, after the final hold in the countdown at T-minus 9 minutes, the Shuttle went through its final preparations for launch, and the countdown was automatically controlled by the Ground Launch Sequencer (GLS), software at the Launch Control Center, which stopped the count if it sensed a critical problem with any of the Shuttle's onboard systems. The GLS handed off the count to the Shuttle's on-board computers at T minus 31 seconds, in a process called auto sequence start.
At T-minus 16 seconds, the massive sound suppression system (SPS) began to drench the Mobile Launcher Platform (MLP) and SRB trenches with 350,000 US gallons (1,300 m3) of water to protect the Orbiter from damage by acoustical energy and rocket exhaust reflected from the flame trench and MLP during lift off (NASA article).[53]
At T-minus 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 main engine turbopumps also began charging the combustion chambers with liquid hydrogen and liquid oxygen at this time. The computers reciprocated this action by allowing the redundant computer systems to begin the firing phase.
The three main engines (SSMEs) started at T-minus 6.6 seconds. The main engines ignited sequentially via the Shuttle's general purpose computers (GPCs) at 120 millisecond intervals. The GPCs required that the engines reach 90 percent of their rated performance to complete the final gimbal of the main engine nozzles to liftoff configuration.[54] When the SSMEs started, water from the sound suppression system flashed into a large volume of steam that shot southward. All three SSMEs had to reach the required 100 percent thrust within three seconds, otherwise the onboard computers would initiate an RSLS abort. If the onboard computers verified normal thrust buildup, at T minus 0 seconds, the 8 pyrotechnic nuts holding the vehicle to the pad were detonated and the SRBs were ignited. At this point the vehicle was committed to liftoff, as the SRBs could not be turned off once ignited.[55] The plume from the solid rockets exited the flame trench in a northward direction at near the speed of sound, often causing a rippling of shockwaves along the actual flame and smoke contrails. At ignition, the GPCs mandated the firing sequences via the Master Events Controller, a computer program integrated with the Shuttle's four redundant computer systems. There were extensive emergency procedures (abort modes) to handle various failure scenarios during ascent. Many of these concerned SSME failures, since that was the most complex and highly stressed component. After the Challenger disaster, there were extensive upgrades to the abort modes.
After the main engines started, but while the solid rocket boosters were still bolted to the pad, the offset thrust from the Shuttle's three main engines caused the entire launch stack (boosters, tank and Shuttle) to pitch down about 2 m at cockpit level. This motion was called the "nod", or "twang" in NASA jargon. As the boosters flexed back into their original shape, the launch stack pitched slowly back upright. This took approximately six seconds. At the point when it was perfectly vertical, the boosters ignited and the launch commenced. The Johnson Space Center's Mission Control Center assumed control of the flight once the SRBs had cleared the launch tower.
Shortly after clearing the tower, the Shuttle began a combined roll, pitch and yaw maneuver that positioned the orbiter head down, with wings level and aligned with the launch pad. The Shuttle flew upside down during the ascent phase. This orientation allowed a trim angle of attack that was favorable for aerodynamic loads during the region of high dynamic pressure, resulting in a net positive load factor, as well as providing the flight crew with use of the ground as a visual reference. The vehicle climbed in a progressively flattening arc, accelerating as the weight of the SRBs and main tank decreased. To achieve low orbit requires much more horizontal than vertical acceleration. This was not visually obvious, since the vehicle rose vertically and was out of sight for most of the horizontal acceleration. The near circular orbital velocity at the 380 kilometers (236 mi) altitude of the International Space Station is 7.68 kilometers per second 27,650 km/h (17,180 mph), roughly equivalent to Mach 23 at sea level. As the International Space Station orbits at an inclination of 51.6 degrees, the Shuttle had to set its inclination to the same value to rendezvous with the station.
Around a point called Max Q, where the aerodynamic forces are at their maximum, the main engines were temporarily throttled back to 72 percent to avoid over-speeding and hence overstressing the Shuttle, particularly in vulnerable areas such as the wings. At this point, a phenomenon known as the Prandtl-Glauert singularity occurred, where condensation clouds formed during the vehicle's transition to supersonic speed. At T+70 seconds, the main engines throttled up to their maximum cruise thrust of 104% rated thrust.
At T+126 seconds after launch, explosive bolts released the SRBs and small separation rockets pushed them laterally away from the vehicle. The SRBs parachuted back to the ocean to be reused. The Shuttle then began accelerating to orbit on the main engines. The vehicle at that point in the flight had a thrust-to-weight ratio of less than one – the main engines actually had insufficient thrust to exceed the force of gravity, and the vertical speed given to it by the SRBs temporarily decreased. However, as the burn continued, the weight of the propellant decreased and the thrust-to-weight ratio exceeded 1 again and the ever-lighter vehicle then continued to accelerate towards orbit.
The vehicle continued to climb and take on a somewhat nose-up angle to the horizon – it used the main engines to gain and then maintain altitude while it accelerated horizontally towards orbit. At about five and three-quarter minutes into ascent, the orbiter's direct communication links with the ground began to fade, at which point it rolled heads up to reroute its communication links to the Tracking and Data Relay Satellite system.
Finally, in the last tens of seconds of the main engine burn, the mass of the vehicle was low enough that the engines had to be throttled back to limit vehicle acceleration to 3 g (29.34 m/s²), largely for astronaut comfort. At approximately eight minutes post launch, the main engines were shut down.
The main engines were shut down before complete depletion of propellant, as running dry would have destroyed the engines. The oxygen supply was terminated before the hydrogen supply, as the SSMEs reacted unfavorably to other shutdown modes. (Liquid oxygen has a tendency to react violently, and supports combustion when it encounters hot engine metal.) The external tank was released by firing explosive bolts, largely burning up in the atmosphere, though some fragments fell into the ocean, in either the Indian Ocean or the Pacific Ocean depending on launch profile.[45] The sealing action of the tank plumbing and lack of pressure relief systems on the external tank helped it break up in the lower atmosphere. After the foam burned away during re-entry, the heat caused a pressure buildup in the remaining liquid oxygen and hydrogen until the tank exploded. This ensured that any pieces that fell back to Earth were small.
To prevent the Shuttle from following the external tank back into the lower atmosphere, the Orbital maneuvering system (OMS) engines were fired to raise the perigee higher into the upper atmosphere. On some missions (e.g., missions to the ISS), the OMS engines were also used while the main engines were still firing. The reason for putting the orbiter on a path that brought it back to Earth was not just for external tank disposal but also one of safety: if the OMS malfunctioned, or the cargo bay doors could not open for some reason, the Shuttle was already on a path to return to earth for an emergency abort landing.
The Shuttle was monitored throughout its ascent for short range tracking (10 seconds before liftoff through 57 seconds after), medium range (7 seconds before liftoff through 110 seconds after) and long range (7 seconds before liftoff through 165 seconds after). Short range cameras included 22 16mm cameras on the Mobile Launch Platform and 8 16mm on the Fixed Service Structure, 4 high speed fixed cameras located on the perimeter of the launch complex plus and additional 42 fixed cameras with 16mm motion picture film. Medium range cameras included remotely operated tracking cameras at the launch complex plus 6 sites along the immediate coast north and south of the launch pad, each with 800mm lens and high speed cameras running 100 feet per second. These cameras ran for only 4–10 seconds due to limitations in the amount of film available. Long range cameras included those mounted on the External Tank, SRBs and orbiter itself which streamed live video back to the ground providing valuable information about any debris falling during ascent. Long range tracking cameras with 400-inch film and 200-inch video lenses were operated by a photographer at Playalinda Beach as well as 9 other sites from 38 miles north at the Ponce Inlet to 23 miles south to Patrick Air Force Base (PAFB) and additional mobile optical tracking camera was stationed on Merritt Island during launches. A total of 10 HD cameras were used both for ascent information for engineers and broadcast feeds to networks such as NASA TV and HDNet The number of cameras significantly increased and numerous existing cameras were upgraded at the recommendation of the Columbia Accident Investigation Board to provide better information about the debris during launch. Debris was also tracked using a pair of Weibel Continuous Pulse Doppler X-band radars, one on board the SRB recovery ship MV Liberty Star positioned north east of the launch pad and on a ship positioned south of the launch pad. Additionally, during the first 2 flights following the loss of Columbia and her crew, a pair of NASA WB-57 reconnaissance aircraft equipped with HD Video and Infrared flew at 60,000 feet (18,000 m) to provide additional views of the launch ascent.[56] Kennedy Space Center also invested nearly $3 million in improvements to the digital video analysis systems in support of debris tracking.[57]
Once in orbit, the Shuttle usually flew at an altitude of 200 miles (321.9 km), and occasionally as high as 400 miles.[58] In the 1980s and 1990s, many flights involved space science missions on the NASA/ESA Spacelab, or launching various types of satellites and science probes. By the 1990s and 2000s the focus shifted more to servicing the space station, with fewer satellite launches. Most missions involved staying in orbit several days to two weeks, although longer missions were possible with the Extended Duration Orbiter add-on or when attached to a space station.
Almost the entire Space Shuttle re-entry procedure, except for lowering the landing gear and deploying the air data probes, were normally performed under computer control. However, the re-entry could be flown entirely manually if an emergency arose. The approach and landing phase could be controlled by the autopilot, but was usually hand flown.
The vehicle began re-entry by firing the Orbital maneuvering system engines, while flying upside down, backside first, in the opposite direction to orbital motion for approximately three minutes, which reduced the Shuttle's velocity by about 200 mph (322 km/h). The resultant slowing of the Shuttle lowered its orbital perigee down into the upper atmosphere. The Shuttle then flipped over, by pushing its nose down (which was actually "up" relative to the Earth, because it was flying upside down). This OMS firing was done roughly halfway around the globe from the landing site.
The vehicle started encountering more significant air density in the lower thermosphere at about 400,000 ft (120 km), at around Mach 25, 8,200 m/s (30,000 km/h; 18,000 mph). The vehicle was controlled by a combination of RCS thrusters and control surfaces, to fly at a 40 degree nose-up attitude, producing high drag, not only to slow it down to landing speed, but also to reduce reentry heating. As the vehicle encountered progressively denser air, it began a gradual transition from spacecraft to aircraft. In a straight line, its 40 degree nose-up attitude would cause the descent angle to flatten-out, or even rise. The vehicle therefore performed a series of four steep S-shaped banking turns, each lasting several minutes, at up to 70 degrees of bank, while still maintaining the 40 degree angle of attack. In this way it dissipated speed sideways rather than upwards. This occurred during the 'hottest' phase of re-entry, when the heat-shield glowed red and the G-forces were at their highest. By the end of the last turn, the transition to aircraft was almost complete. The vehicle leveled its wings, lowered its nose into a shallow dive and began its approach to the landing site.
The orbiter's maximum glide ratio/lift-to-drag ratio varies considerably with speed, ranging from 1:1 at hypersonic speeds, 2:1 at supersonic speeds and reaching 4.5:1 at subsonic speeds during approach and landing.[59]
In the lower atmosphere, the orbiter flies much like a conventional glider, except for a much higher descent rate, over 50 m/s (180 km/h; 110 mph)(9800fpm). At approximately Mach 3, two air data probes, located on the left and right sides of the orbiter's forward lower fuselage, are deployed to sense air pressure related to the vehicle's movement in the atmosphere.
When the approach and landing phase began, the orbiter was at a 3,000 m (9,800 ft) altitude, 12 km (7.5 mi) from the runway. The pilots applied aerodynamic braking to help slow down the vehicle. The orbiter's speed was reduced from 682 to 346 km/h (424 to 215 mph), approximately, at touch-down (compared to 260 km/h (160 mph) for a jet airliner). The landing gear was deployed while the Orbiter was flying at 430 km/h (270 mph). To assist the speed brakes, a 12 m (39 ft) drag chute was deployed either after main gear or nose gear touchdown (depending on selected chute deploy mode) at about 343 km/h (213 mph). The chute was jettisoned once the orbiter slowed to 110 km/h (68.4 mph).
Media related to Landings of space Shuttles at Wikimedia Commons
After landing, the vehicle stayed on the runway for several minutes for the orbiter to cool. Teams at the front and rear of the orbiter tested for presence of hydrogen, hydrazine, monomethylhydrazine, nitrogen tetroxide and ammonia (fuels and by products of the control and the orbiter's three APUs). If hydrogen was detected, an emergency would be declared, the orbiter powered down and teams would evacuate the area. A convoy of 25 specially-designed vehicles and 150 trained engineers and technicians approached the orbiter. Purge and vent lines were attached to remove toxic gasses from fuel lines and the cargo bay about 45–60 minutes after landing. A flight surgeon boarded the orbiter for initial medical checks of the crew before disembarking. Once the crew left the orbiter, responsibility for the vehicle was handed from the Johnson Space Center back to the Kennedy Space Center[60]
If the mission ended at Edwards Air Force Base in California, White Sands Space Harbor in New Mexico, or any of the runways the orbiter might use in an emergency, the orbiter was loaded atop the Shuttle Carrier Aircraft, a modified 747, for transport back to the Kennedy Space Center, landing at the Shuttle Landing Facility. Once at the Shuttle Landing Facility, the orbiter was then towed 2 miles (3.2 km) along a tow-way and access roads normally used by tour busses and KSC employees to the Orbiter Processing Facility where it began a months-long preparation process for the next mission.[60]
NASA preferred Space Shuttle landings to be at Kennedy Space Center.[61] If weather conditions made landing there unfavorable, the Shuttle could delay its landing until conditions are favorable, touch down at Edwards Air Force Base, California, or use one of the multiple alternate landing sites around the world. A landing at any site other than Kennedy Space Center meant that after touchdown the Shuttle must be mated to the Shuttle Carrier Aircraft and returned to Cape Canaveral. Space Shuttle Columbia (STS-3) landed at the White Sands Space Harbor, New Mexico; this was viewed as a last resort as NASA scientists believe that the sand could potentially damage the Shuttle's exterior.
There were many alternative landing sites that were never used.[62][63]
An example of technical risk analysis for a STS mission is SPRA iteration 3.1 top risk contributors for STS-133:[64][65]
An internal NASA risk assessment study (conducted by the Shuttle Program Safety and Mission Assurance Office at Johnson Space Center) released in late 2010 or early 2011 concluded that the agency had seriously underestimated the level of risk involved in operating the Shuttle. The report assessed that there was a 1 in 9 chance of a catastrophic disaster during the first nine flights of the Shuttle but that safety improvements had later improved the risk ratio to 1 in 100.[66]
Below is a list of major events in the Space Shuttle orbiter fleet.
| Date | Orbiter | Major event / remarks |
|---|---|---|
| September 17, 1976 | Enterprise | Prototype Space Shuttle Enterprise was rolled out of its assembly facility in Southern California and displayed before a crowd several thousand strong.[67] |
| February 18, 1977 | Enterprise | First flight; Attached to Shuttle Carrier Aircraft throughout flight. |
| August 12, 1977 | Enterprise | First free flight; Tailcone on; lakebed landing. |
| October 26, 1977 | Enterprise | Final Enterprise free flight; First landing on Edwards AFB concrete runway. |
| April 12, 1981 | Columbia | First Columbia flight, first orbital test flight; STS-1 |
| November 11, 1982 | Columbia | First operational flight of the Space Shuttle, first mission to carry four astronauts; STS-5 |
| April 4, 1983 | Challenger | First Challenger flight; STS-6 |
| August 30, 1984 | Discovery | First Discovery flight; STS-41-D |
| October 3, 1985 | Atlantis | First Atlantis flight; STS-51-J |
| October 30, 1985 | Challenger | First crew of eight astronauts; STS-61-A |
| January 28, 1986 | Challenger | Disaster starting 73 seconds after launch; STS-51-L; all seven crew members died. |
| September 29, 1988 | Discovery | First post-Challenger mission; STS-26 |
| May 4, 1989 | Atlantis | The first Space Shuttle mission to launch a space probe, Magellan; STS-30 |
| April 24, 1990 | Discovery | Launch of the Hubble Space Telescope; STS-31 |
| May 7, 1992 | Endeavour | First Endeavour flight; STS-49 |
| November 19, 1996 | Columbia | Longest Shuttle mission at 17 days, 15 hours; STS-80 |
| December 4, 1998 | Endeavour | First ISS mission; STS-88 |
| February 1, 2003 | Columbia | Disintegrated during re-entry; STS-107; all seven crew members died. |
| July 25, 2005 | Discovery | First post-Columbia mission; STS-114 |
| February 24, 2011 | Discovery | Last Discovery flight; STS-133 |
| May 16, 2011 | Endeavour | Last Endeavour mission; STS-134[68][69] |
| July 8, 2011 | Atlantis | Last Atlantis flight and last Space Shuttle flight; STS-135 |
Sources: NASA launch manifest,[70] NASA Space Shuttle archive[71]
On January 28, 1986, Challenger disintegrated 73 seconds after launch due to the failure of the right SRB, killing all seven astronauts on board. The disaster was caused by low-temperature impairment of an O-ring, a mission critical seal used between segments of the SRB casing. The failure of a lower O-ring seal allowed hot combustion gases to escape from between the booster sections and burn through the adjacent external tank, causing it to disintegrate. Repeated warnings from design engineers voicing concerns about the lack of evidence of the O-rings' safety when the temperature was below 53 °F (12 °C) had been ignored by NASA managers.[72]
On February 1, 2003, Columbia disintegrated during re-entry, killing its crew of seven, 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, while NASA's chief thermal protection system (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 assistance and refused the request for the spacewalk,[73] and thus the feasibility of scenarios for astronaut repair or rescue by Atlantis were not considered by NASA management at the time.[74]
NASA retired the Space Shuttle in 2011, after 30 years of service. Discovery was the first of NASA's three remaining operational Space Shuttles to be retired.[75] Michael Suffredini of the ISS program said that one additional trip was needed in 2011 to deliver parts to the International Space Station.[76]
The final Space Shuttle mission was originally scheduled for late 2010, but the program was later extended to July 2011. Its final mission consisted of just four astronauts—Christopher Ferguson (Commander), Douglas Hurley (Pilot), Sandra Magnus (Mission Specialist 1), and Rex Walheim (Mission Specialist 2);[77] they conducted the 135th and last space Shuttle mission on board Atlantis, which launched on July 8, 2011 and landed safely at the Kennedy Space Center on July 21, 2011 at 5:57 AM EDT (09:57 UTC).[78]
NASA announced it would transfer space-worthy orbiters to education institutions or museums at the conclusion of the Space Shuttle program. Each museum or institution is responsible for covering the US$28.8 million cost of preparing and transporting each vehicle for display. Twenty museums from across the country submitted proposals for receiving one of the retired orbiters.[79] NASA also made Space Shuttle thermal protection system tiles available to schools and universities for less than US$25 each.[80] About 7,000 tiles were available on a first-come, first-served basis, limited to one per institution.[80]
On April 12, 2011, NASA announced selection of locations for the remaining Shuttle orbiters:[81][82]
Flight and mid-deck training hardware will be taken from the Johnson Space Center and will go to the National Air and Space Museum and the National Museum of the U.S. Air Force. The full fuselage mockup, which includes the payload bay and aft section but no wings, is to go to the Museum of Flight in Seattle. Mission Simulation and Training Facility's fixed simulator will go to the Adler Planetarium in Chicago, and the motion simulator will go to the Texas A&M Aerospace Engineering Department in College Station, Texas. Other simulators used in Shuttle astronaut training will go to the Wings of Dreams Aviation Museum in Starke, Florida and the Virginia Air and Space Center in Hampton, Virginia.[79]
In August 2011, the NASA Office of Inspector General (OIG) published a "Review of NASA's Selection of Display Locations for the Space Shuttle Orbiters"; the review had four main findings:[83]
The NASA OIG had three recommendations, saying NASA should:[83]
In September 2011, the CEO and two board members of Seattle's Museum of Flight met with NASA Administrator Charles Bolden, pointing out "significant errors in deciding where to put its four retiring Space Shuttles"; the errors alleged include inaccurate information on Museum of Flight's attendance and international visitor statistics, as well as the readiness of the Intrepid Sea-Air-Space Museum's exhibit site.[84]
Until another U.S. launch vehicle is ready, crews will travel to and from the International Space Station aboard Russian Soyuz spacecraft or possibly a future American commercial spacecraft. A planned successor to STS was the "Shuttle II" during the 1980s and 1990s, and later the Constellation program during the 2004–2010 period. CSTS was a proposal to continue to operate STS commercially, after NASA.[85] On September 14, 2011, NASA announced that it had selected the design of a new Space Launch System that it said would take the agency's astronauts farther into space than ever before and provide the cornerstone for future human space exploration efforts by the U.S.[86][87][88]
Space Shuttles have been featured in numerous works of fiction and nonfiction, from movies for kids to documentaries. Early examples include the 1979 James Bond film, Moonraker, the 1982 Activision videogame Space Shuttle: A Journey into Space (1982) and G. Harry Stine's 1981 novel Shuttle Down. In the 1986 film SpaceCamp, Atlantis accidentally launched into space with a group of U.S. Space Camp participants as its crew. The 1998 film Armageddon portrayed a combined crew of offshore oil rig workers and US military staff who pilot two modified Shuttles to avert the destruction of Earth by an asteroid. Retired American test pilots visited a Russian satellite in the 2000 Clint Eastwood adventure film Space Cowboys. In the 2003 film The Core, the Endeavour's landing is disrupted by the earth's magnetic core, and its crew is selected to pilot the vehicle designed to restart the core. The 2004 Bollywood movie Swades, where a Space Shuttle was used to launch a special rainfall monitoring satellite, was filmed at Kennedy Space Center in the year following the Columbia disaster that had taken the life of Indian astronautKC Chawla. On television, the 1996 drama The Cape portrayed the lives of a group of NASA astronauts as they prepared for and flew Shuttle missions. Odyssey 5 was a short lived sci-fi series that featured the crew of a Space Shuttle as the last survivors of a disaster that destroyed Earth.
The Space Shuttle has also been the subject of toys and models; for example, a large Lego Space Shuttle model was constructed by visitors at Kennedy Space Center,[89] and smaller models have been sold commercially as a standard "LegoLand" set.
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.[90]
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