title: Controversial Reddit communities

text: In mid-December 2013, users from r/MensRights, as well as 4chan, spammed the Occidental College Online Rape Report Form with hundreds of false rape reports, following a user's complaint that the form was vulnerable to abuse as a result of the submitter's ability to remain anonymous. Around 400 false rape accusations were made by men's rights activists against members of the college, feminists, and fictional people.


title: Controversial Reddit communities

text: r/NoFap is a subreddit dedicated to supporting those who wish to give up pornography or masturbation.


title: Controversial Reddit communities

text: Some journalists have reported that NoFap's forums were filled with misogyny, stating that "there is a darker side to NoFap. Among the reams of Reddit discussions and YouTube videos, a fundamentally misogynistic rhetoric regularly emerges", that the subreddit idolizes testosterone and inherently masculine qualities, and that "the NoFap community has become linked to wider sexism and misogyny, reducing women to sexual objects to be attained or abstained from, and shaming sexually active women."


title: Controversial Reddit communities

text: In 2019, r/piracy was threatened with a ban after receiving dozens of DMCA takedown notices. The moderators said that Reddit did not investigate the infringement claims to find if they actually infringed copyright law, often they related to content such as sharing the URL to a streaming site, asking if such sites were working, and posting guides to install programs. Users of the subreddit voted to delete all content older than six months, as it was not feasible to investigate all past content.


title: Controversial Reddit communities

text: r/PiratedGames, whose discussions focused specifically on pirated video games, was banned on 17 August 2022 for excessive DMCA claims, even though the subreddit explicitly banned sharing pirated content. With over 300,000 subscribers, it was among the largest piracy-related subreddits. It was restored the next day following an appeal from the moderators. "TorrentFreak" in separate articles said the ban was part of Reddit's increasing crackdown on copyright infringement, noting that the year prior around 2,625 subreddits had been banned for similar reasons, and that DMCA takedowns on Reddit had increased by over 15,000% in the past five years.


title: Controversial Reddit communities

text: The subreddit r/Portugueses is often home to Portuguese nationalist and nativist rhetoric. It also contains racism, homophobia, sexism, and other Reddit-policy violations. Moderators and volunteer moderators of other subreddits who remove or report hate speech and other policy violations coming from r/Portugueses are often threatened for doing so.


title: Controversial Reddit communities

text: r/Russia, the national subreddit for Russia, was quarantined on 1 March 2022, and the site's administrators removed one of the moderators, for spreading disinformation about the Russian invasion of Ukraine. Among the disinformation promoted by the sub's moderators were claims that the Ukrainian military was controlled by Nazis, that Ukraine was using human shields to raise the conflict's death toll, and that the Ukrainian leadership was refusing calls for peace negotiations. The sub had over 265,000 subscribers prior to the quarantine. Sister sub r/RussiaPolitics was also quarantined for similar reasons.


title: Controversial Reddit communities

text: In April 2014, it was made apparent that moderators of r/technology, a subreddit with 5 million subscribers, were using automatic filters to remove submissions that contained certain keywords, such as "Aaron Swartz", "Tesla", "Comcast", "NSA", and "Snowden". This ultimately led to community protests, claims of censorship from users, and r/technology losing its default subreddit status.


title: Controversial Reddit communities

text: Alluding to the symbol of the "red pill" from the film "The Matrix", r/TheRedPill is devoted to discussions of male sexual strategy in which participants are ranked as "alpha" or "beta" males. The subreddit promotes antifeminism, rape culture, hegemonic masculinity, and traditional gender roles. Users discuss diet and physical fitness alongside "pick-up" techniques for seducing women, while also displaying different levels of misogyny ranging from virulent hatred of women to simple frustration with contemporary male experience. The Southern Poverty Law Center describes it as one of several male supremacist subreddits featuring xenophobic discourse. It has been associated with several right-wing movements and the alt-right because of its attacks on feminism and mockery of rape.


title: Controversial Reddit communities

text: In 2017, it was revealed that New Hampshire legislator Robert Fisher created the subreddit and posted demeaning comments about women. After this discovery, he resigned from office. "The New Statesman" has described this subreddit as one of the most misogynistic subreddits on Reddit, which aims to radicalize men. , the subreddit is quarantined.


title: Controversial Reddit communities

text: In accordance with its policies at the time on free speech, Reddit's admins stated in 2013 that they did not ban communities solely for featuring controversial content. Reddit's general manager Erik Martin noted that "having to stomach occasional troll [sub]reddits like r/picsofdeadkids or morally questionable [sub]reddits like r/jailbait are part of the price of free speech on a site like this," and that it is not Reddit's place to censor its users. The site's former CEO, Yishan Wong, stated that distasteful subreddits would not be banned because Reddit as a platform should serve the ideals of free speech. Critics of Reddit's position argued at the time that it had not been consistent in following its free speech philosophy. In a 2015 discussion on the site's content policy, founder Steve Huffman stated that "neither Alexis [Ohanian] nor I created Reddit to be a bastion of free speech".


title: Controversial Reddit communities

text: With the banning of r/The Donald, Reddit expanded the kinds of content that was banned on the site, implementing new rules that directly prohibit hate speech. In 2021, Reddit stated that they allowed conversations that "question or disagree with popular consensus" regarding the COVID-19 pandemic, stating that "dissent is a part of Reddit and the foundation of democracy" despite criticism by site moderators. Although it banned r/NoNewNormal after moderator protests, this was for unduly influencing other communities, not the subreddit's content.


title: Space Shuttle

text: The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft where it was the only item funded for development. The first (STS-1) of four orbital test flights occurred in 1981, leading to operational flights (STS-5) beginning in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011. They launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST), conducted science experiments in orbit, participated in the Shuttle-"Mir" program with Russia, and participated in construction and servicing of the International Space Station (ISS). The Space Shuttle fleet's total mission time was 1,323 days.


title: Space Shuttle

text: Space Shuttle components include the Orbiter Vehicle (OV) with three clustered Rocketdyne RS-25 main engines, a pair of recoverable solid rocket boosters (SRBs), and the expendable external tank (ET) containing liquid hydrogen and liquid oxygen. The Space Shuttle was launched vertically, like a conventional rocket, with the two SRBs operating in parallel with the orbiter's three main engines, which were fueled from the ET. The SRBs were jettisoned before the vehicle reached orbit, while the main engines continued to operate, and the ET was jettisoned after main engine cutoff and just before orbit insertion, which used the orbiter's two Orbital Maneuvering System (OMS) engines. At the conclusion of the mission, the orbiter fired its OMS to deorbit and reenter the atmosphere. The orbiter was protected during reentry by its thermal protection system tiles, and it glided as a spaceplane to a runway landing, usually to the Shuttle Landing Facility at KSC, Florida, or to Rogers Dry Lake in Edwards Air Force Base, California. If the landing occurred at Edwards, the orbiter was flown back to the KSC atop the Shuttle Carrier Aircraft (SCA), a specially modified Boeing 747.


title: Space Shuttle

text: The first orbiter, "Enterprise", was built in 1976 and used in Approach and Landing Tests (ALT), but had no orbital capability. Four fully operational orbiters were initially built: "Columbia", "Challenger", "Discovery", and "Atlantis". Of these, two were lost in mission accidents: "Challenger" in 1986 and "Columbia" in 2003, with a total of 14 astronauts killed. A fifth operational (and sixth in total) orbiter, "Endeavour", was built in 1991 to replace "Challenger". The three surviving operational vehicles were retired from service following "Atlantis"s final flight on July 21, 2011. The U.S. relied on the Russian Soyuz spacecraft to transport astronauts to the ISS from the last Shuttle flight until the launch of the Crew Dragon Demo-2 mission in May 2020.


title: Space Shuttle

text: During the 1950s, the United States Air Force proposed using a reusable piloted glider to perform military operations such as reconnaissance, satellite attack, and air-to-ground weapons employment. In the late 1950s, the Air Force began developing the partially reusable X-20 Dyna-Soar. The Air Force collaborated with NASA 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, a fully reusable spacecraft that was never developed beyond the initial design phase in 1962–1963.


title: Space Shuttle

text: Beginning in the early 1950s, NASA and the Air Force collaborated on developing lifting bodies to test aircraft that primarily generated lift from their fuselages instead of wings, and tested the NASA M2-F1, Northrop M2-F2, Northrop M2-F3, Northrop HL-10, Martin Marietta X-24A, and the Martin Marietta X-24B. 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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, 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, 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, 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 for transfers between orbits and the Moon, and a reusable nuclear upper stage for deep space travel.


title: Space Shuttle

text: 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, 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.


title: Space Shuttle

text: 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. 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 to begin development on the RS-25 engine.


title: Space Shuttle

text: 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 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, and the external tank contract to Martin Marietta.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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, as the shuttle could then be constructed of lightweight aluminum, 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: After it arrived at Edwards AFB, "Enterprise" underwent flight testing with the Shuttle Carrier Aircraft, 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 in 1984.


title: Space Shuttle

text: 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 and Robert Crippen. 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.


title: Space Shuttle

text: NASA conducted three additional test flights with "Columbia" in 1981 and 1982. On July 4, 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, and delivered a speech. After STS-4, NASA declared its Space Transportation System (STS) operational.


title: Space Shuttle

text: 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, which contained the crew and payload, the external tank (ET), and the two solid rocket boosters (SRBs).


title: Space Shuttle

text: 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 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 handled main engine testing, and the Goddard Space Flight Center managed the global tracking network.


title: Space Shuttle

text: 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 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 was swept backwards at 45° 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, each containing two tires. The main landing gear contained two brake assemblies each, and the nose landing gear contained an electro-hydraulic steering mechanism.


title: Space Shuttle

text: 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, 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 and STS-51-J to serve as a military representative for a National Reconnaissance Office payload. A Space Shuttle crew typically had seven astronauts, with STS-61-A flying with eight.


title: Space Shuttle

text: 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 (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.


title: Space Shuttle

text: 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, until the loss of "Challenger", the crew wore one-piece light blue nomex 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 (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 and first four missions, but these were disabled after STS-4 and removed after STS-9.


title: Space Shuttle

text: 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 (HUD) and a Rotational Hand Controller (RHC) to gimbal the engines during powered flight and fly the orbiter during unpowered flight. Both seats also had rudder 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, 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 during cargo operations. Additionally, the aft flight deck had monitors for a closed-circuit television to view the cargo bay.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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 and the ISS, 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. 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.


title: Space Shuttle

text: The orbiter was equipped with an avionics system to provide information and control during atmospheric flight. Its avionics suite contained three microwave scanning beam landing systems, three gyroscopes, three TACANs, three accelerometers, two radar altimeters, two barometric altimeters, three attitude indicators, two Mach indicators, and two Mode C transponders. 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 trackers 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 (INS), which provided more accurate location information. In 1993, NASA flew a GPS 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 in August 2007.


title: Space Shuttle

text: 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 transceivers, and could transmit and receive information. The other two S band radios were frequency modulation transmitters and were used to transmit data to NASA. As S band radios can operate only within their line of sight, NASA used the Tracking and Data Relay Satellite System 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 K 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 and astronauts conducting EVA.


title: Space Shuttle

text: The Space Shuttle's fly-by-wire 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 (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.


title: Space Shuttle

text: 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 and Intel laptops.


title: Space Shuttle

text: The payload bay comprised most of the orbiter vehicle's fuselage, 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.


title: Space Shuttle

text: 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 (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".


title: Space Shuttle

text: 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 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 .


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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 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.


title: Space Shuttle

text: 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 area. The normal maximum throttle was 104 percent, with 106% or 109% used for mission aborts.


title: Space Shuttle

text: The Orbital Maneuvering System (OMS) consisted of two aft-mounted AJ10-190 engines and the associated propellant tanks. The AJ10 engines used monomethylhydrazine (MMH) oxidized by dinitrogen tetroxide (NO). The pods carried a maximum of of MMH and of NO. 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.


title: Space Shuttle

text: 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 .


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: For the first two missions, STS-1 and STS-2, 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. 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: The rocket motors were each filled with a total of solid rocket propellant (APCP+PBAN), and joined in the Vehicle Assembly Building (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 (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. 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.


title: Space Shuttle

text: The SRBs underwent several redesigns throughout the program's lifetime. STS-6 and STS-7 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 used cases that were thinner than the standard-weight cases, which saved . After the "Challenger" disaster as a result of an O-ring failing at low temperature, the SRBs were redesigned to provide a constant seal regardless of the ambient temperature.


title: Space Shuttle

text: 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 (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 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 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 comprised three locomotives that transported SRB segments from the Florida East Coast Railway in Titusville to the KSC.


title: Space Shuttle

text: 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 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.


title: Space Shuttle

text: 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, 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 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.


title: Space Shuttle

text: 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 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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 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.


title: Space Shuttle

text: 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 .


title: Space Shuttle

text: 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, Spacelab, and the 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. 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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 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.


title: Space Shuttle

text: 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 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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 on May 30, 2020.


title: Space Shuttle

text: 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).


title: Space Shuttle

text: 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.


title: Space Shuttle

text: On February 1, 2003, "Columbia" disintegrated during re-entry, killing all seven of the STS-107 crew, 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 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.


title: Space Shuttle

text: 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.


title: Space Shuttle

text: 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 (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.


title: Space Shuttle

text: 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 and 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 "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.


title: Space Shuttle

text: 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 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 Crew Dragon Demo-2 on May 30, 2020, the US launched its astronauts aboard Russian Soyuz spacecraft.


title: Space Shuttle

text: 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 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.


title: Space Shuttle

text: 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]].


title: Apollo program

text: The Apollo program, also known as Project Apollo, was the third United States human spaceflight program carried out by the National Aeronautics and Space Administration (NASA), which succeeded in preparing and landing the first humans on the Moon from 1968 to 1972. It was first conceived in 1960 during President Dwight D. Eisenhower's administration as a three-person spacecraft to follow the one-person Project Mercury, which put the first Americans in space. Apollo was later dedicated to President John F. Kennedy's national goal for the 1960s of "landing a man on the Moon and returning him safely to the Earth" in an address to Congress on May 25, 1961. It was the third US human spaceflight program to fly, preceded by the two-person Project Gemini conceived in 1961 to extend spaceflight capability in support of Apollo.


title: Apollo program

text: Kennedy's goal was accomplished on the Apollo 11 mission when astronauts Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Module (LM) on July 20, 1969, and walked on the lunar surface, while Michael Collins remained in lunar orbit in the command and service module (CSM), and all three landed safely on Earth in the Pacific Ocean on July 24. Five subsequent Apollo missions also landed astronauts on the Moon, the last, Apollo 17, in December 1972. In these six spaceflights, twelve people walked on the Moon.


title: Apollo program

text: Apollo ran from 1961 to 1972, with the first crewed flight in 1968. It encountered a major setback in 1967 when an Apollo 1 cabin fire killed the entire crew during a prelaunch test. After the first successful landing, sufficient flight hardware remained for nine follow-on landings with a plan for extended lunar geological and astrophysical exploration. Budget cuts forced the cancellation of three of these. Five of the remaining six missions achieved successful landings, but the Apollo 13 landing was prevented by an oxygen tank explosion in transit to the Moon, crippling the CSM. The crew barely returned to Earth safely by using the lunar module as a "lifeboat" on the return journey. Apollo used the Saturn family of rockets as launch vehicles, which were also used for an Apollo Applications Program, which consisted of Skylab, a space station that supported three crewed missions in 1973–1974, and the Apollo–Soyuz Test Project, a joint United States-Soviet Union low Earth orbit mission in 1975.


title: Apollo program

text: Apollo set several major human spaceflight milestones. It stands alone in sending crewed missions beyond low Earth orbit. Apollo 8 was the first crewed spacecraft to orbit another celestial body, and Apollo 11 was the first crewed spacecraft to land humans on one.


title: Apollo program

text: Overall the Apollo program returned of lunar rocks and soil to Earth, greatly contributing to the understanding of the Moon's composition and geological history. The program laid the foundation for NASA's subsequent human spaceflight capability, and funded construction of its Johnson Space Center and Kennedy Space Center. Apollo also spurred advances in many areas of technology incidental to rocketry and human spaceflight, including avionics, telecommunications, and computers.


title: Apollo program

text: The Apollo program was conceived during the Eisenhower administration in early 1960, as a follow-up to Project Mercury. While the Mercury capsule could support only one astronaut on a limited Earth orbital mission, Apollo would carry three. Possible missions included ferrying crews to a space station, circumlunar flights, and eventual crewed lunar landings.


title: Apollo program

text: The program was named after Apollo, the Greek god of light, music, and the Sun, by NASA manager Abe Silverstein, who later said, "I was naming the spacecraft like I'd name my baby." Silverstein chose the name at home one evening, early in 1960, because he felt "Apollo riding his chariot across the Sun was appropriate to the grand scale of the proposed program."


title: Apollo program

text: In July 1960, NASA Deputy Administrator Hugh L. Dryden announced the Apollo program to industry representatives at a series of Space Task Group conferences. Preliminary specifications were laid out for a spacecraft with a "mission module" cabin separate from the "command module" (piloting and reentry cabin), and a "propulsion and equipment module". On August 30, a feasibility study competition was announced, and on October 25, three study contracts were awarded to General Dynamics/Convair, General Electric, and the Glenn L. Martin Company. Meanwhile, NASA performed its own in-house spacecraft design studies led by Maxime Faget, to serve as a gauge to judge and monitor the three industry designs.


title: Apollo program

text: In November 1960, John F. Kennedy was elected president after a campaign that promised American superiority over the Soviet Union in the fields of space exploration and missile defense. Up to the election of 1960, Kennedy had been speaking out against the "missile gap" that he and many other senators felt had developed between the Soviet Union and the United States due to the inaction of President Eisenhower. Beyond military power, Kennedy used aerospace technology as a symbol of national prestige, pledging to make the US not "first but, first and, first if, but first period". Despite Kennedy's rhetoric, he did not immediately come to a decision on the status of the Apollo program once he became president. He knew little about the technical details of the space program, and was put off by the massive financial commitment required by a crewed Moon landing. When Kennedy's newly appointed NASA Administrator James E. Webb requested a 30 percent budget increase for his agency, Kennedy supported an acceleration of NASA's large booster program but deferred a decision on the broader issue.


title: Apollo program

text: On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first person to fly in space, reinforcing American fears about being left behind in a technological competition with the Soviet Union. At a meeting of the US House Committee on Science and Astronautics one day after Gagarin's flight, many congressmen pledged their support for a crash program aimed at ensuring that America would catch up. Kennedy was circumspect in his response to the news, refusing to make a commitment on America's response to the Soviets.


title: Apollo program

text: On April 20, Kennedy sent a memo to Vice President Lyndon B. Johnson, asking Johnson to look into the status of America's space program, and into programs that could offer NASA the opportunity to catch up. Johnson responded approximately one week later, concluding that "we are neither making maximum effort nor achieving results necessary if this country is to reach a position of leadership." His memo concluded that a crewed Moon landing was far enough in the future that it was likely the United States would achieve it first.


title: Apollo program

text: On May 25, 1961, twenty days after the first US crewed spaceflight "Freedom 7", Kennedy proposed the crewed Moon landing in a "Special Message to the Congress on Urgent National Needs":


title: Apollo program

text: At the time of Kennedy's proposal, only one American had flown in space—less than a month earlier—and NASA had not yet sent an astronaut into orbit. Even some NASA employees doubted whether Kennedy's ambitious goal could be met. By 1963, Kennedy even came close to agreeing to a joint US-USSR Moon mission, to eliminate duplication of effort.


title: Apollo program

text: With the clear goal of a crewed landing replacing the more nebulous goals of space stations and circumlunar flights, NASA decided that, in order to make progress quickly, it would discard the feasibility study designs of Convair, GE, and Martin, and proceed with Faget's command and service module design. The mission module was determined to be useful only as an extra room, and therefore unnecessary. They used Faget's design as the specification for another competition for spacecraft procurement bids in October 1961. On November 28, 1961, it was announced that North American Aviation had won the contract, although its bid was not rated as good as Martin's. Webb, Dryden and Robert Seamans chose it in preference due to North American's longer association with NASA and its predecessor.


title: Apollo program

text: Landing humans on the Moon by the end of 1969 required the most sudden burst of technological creativity, and the largest commitment of resources ($25 billion; $ in US dollars) ever made by any nation in peacetime. At its peak, the Apollo program employed 400,000 people and required the support of over 20,000 industrial firms and universities.


title: Apollo program

text: On July 1, 1960, NASA established the Marshall Space Flight Center (MSFC) in Huntsville, Alabama. MSFC designed the heavy lift-class Saturn launch vehicles, which would be required for Apollo.


title: Apollo program

text: It became clear that managing the Apollo program would exceed the capabilities of Robert R. Gilruth's Space Task Group, which had been directing the nation's crewed space program from NASA's Langley Research Center. So Gilruth was given authority to grow his organization into a new NASA center, the Manned Spacecraft Center (MSC). A site was chosen in Houston, Texas, on land donated by Rice University, and Administrator Webb announced the conversion on September 19, 1961. It was also clear NASA would soon outgrow its practice of controlling missions from its Cape Canaveral Air Force Station launch facilities in Florida, so a new Mission Control Center would be included in the MSC.


title: Apollo program

text: In September 1962, by which time two Project Mercury astronauts had orbited the Earth, Gilruth had moved his organization to rented space in Houston, and construction of the MSC facility was under way, Kennedy visited Rice to reiterate his challenge in a famous speech:


title: Apollo program

text: The MSC was completed in September 1963. It was renamed by the US Congress in honor of Lyndon Johnson soon after his death in 1973.


title: Apollo program

text: It also became clear that Apollo would outgrow the Canaveral launch facilities in Florida. The two newest launch complexes were already being built for the Saturn I and IB rockets at the northernmost end: LC-34 and LC-37. But an even bigger facility would be needed for the mammoth rocket required for the crewed lunar mission, so land acquisition was started in July 1961 for a Launch Operations Center (LOC) immediately north of Canaveral at Merritt Island. The design, development and construction of the center was conducted by Kurt H. Debus, a member of Dr. Wernher von Braun's original V-2 rocket engineering team. Debus was named the LOC's first Director. Construction began in November 1962. Following Kennedy's death, President Johnson issued an executive order on November 29, 1963, to rename the LOC and Cape Canaveral in honor of Kennedy.


title: Apollo program

text: The LOC included Launch Complex 39, a Launch Control Center, and a Vertical Assembly Building (VAB). in which the space vehicle (launch vehicle and spacecraft) would be assembled on a mobile launcher platform and then moved by a crawler-transporter to one of several launch pads. Although at least three pads were planned, only two, designated AandB, were completed in October 1965. The LOC also included an Operations and Checkout Building (OCB) to which Gemini and Apollo spacecraft were initially received prior to being mated to their launch vehicles. The Apollo spacecraft could be tested in two vacuum chambers capable of simulating atmospheric pressure at altitudes up to , which is nearly a vacuum.


title: Apollo program

text: Administrator Webb realized that in order to keep Apollo costs under control, he had to develop greater project management skills in his organization, so he recruited Dr. George E. Mueller for a high management job. Mueller accepted, on the condition that he have a say in NASA reorganization necessary to effectively administer Apollo. Webb then worked with Associate Administrator (later Deputy Administrator) Seamans to reorganize the Office of Manned Space Flight (OMSF). On July 23, 1963, Webb announced Mueller's appointment as Deputy Associate Administrator for Manned Space Flight, to replace then Associate Administrator D. Brainerd Holmes on his retirement effective September 1. Under Webb's reorganization, the directors of the Manned Spacecraft Center (Gilruth), Marshall Space Flight Center (von Braun), and the Launch Operations Center (Debus) reported to Mueller.


title: Apollo program

text: Based on his industry experience on Air Force missile projects, Mueller realized some skilled managers could be found among high-ranking officers in the U.S. Air Force, so he got Webb's permission to recruit General Samuel C. Phillips, who gained a reputation for his effective management of the Minuteman program, as OMSF program controller. Phillips's superior officer Bernard A. Schriever agreed to loan Phillips to NASA, along with a staff of officers under him, on the condition that Phillips be made Apollo Program Director. Mueller agreed, and Phillips managed Apollo from January 1964, until it achieved the first human landing in July 1969, after which he returned to Air Force duty.


title: Apollo program

text: Once Kennedy had defined a goal, the Apollo mission planners were faced with the challenge of designing a spacecraft that could meet it while minimizing risk to human life, cost, and demands on technology and astronaut skill. Four possible mission modes were considered:


title: Apollo program

text: In early 1961, direct ascent was generally the mission mode in favor at NASA. Many engineers feared that rendezvous and docking, maneuvers that had not been attempted in Earth orbit, would be nearly impossible in lunar orbit. LOR advocates including John Houbolt at Langley Research Center emphasized the important weight reductions that were offered by the LOR approach. Throughout 1960 and 1961, Houbolt campaigned for the recognition of LOR as a viable and practical option. Bypassing the NASA hierarchy, he sent a series of memos and reports on the issue to Associate Administrator Robert Seamans; while acknowledging that he spoke "somewhat as a voice in the wilderness", Houbolt pleaded that LOR should not be discounted in studies of the question.


title: Apollo program

text: Seamans's establishment of an ad hoc committee headed by his special technical assistant Nicholas E. Golovin in July 1961, to recommend a launch vehicle to be used in the Apollo program, represented a turning point in NASA's mission mode decision. This committee recognized that the chosen mode was an important part of the launch vehicle choice, and recommended in favor of a hybrid EOR-LOR mode. Its consideration of LOR—as well as Houbolt's ceaseless work—played an important role in publicizing the workability of the approach. In late 1961 and early 1962, members of the Manned Spacecraft Center began to come around to support LOR, including the newly hired deputy director of the Office of Manned Space Flight, Joseph Shea, who became a champion of LOR. The engineers at Marshall Space Flight Center (MSFC), which had much to lose from the decision, took longer to become convinced of its merits, but their conversion was announced by Wernher von Braun at a briefing on June 7, 1962.


title: Apollo program

text: But even after NASA reached internal agreement, it was far from smooth sailing. Kennedy's science advisor Jerome Wiesner, who had expressed his opposition to human spaceflight to Kennedy before the President took office, and had opposed the decision to land people on the Moon, hired Golovin, who had left NASA, to chair his own "Space Vehicle Panel", ostensibly to monitor, but actually to second-guess NASA's decisions on the Saturn V launch vehicle and LOR by forcing Shea, Seamans, and even Webb to defend themselves, delaying its formal announcement to the press on July 11, 1962, and forcing Webb to still hedge the decision as "tentative".


title: Apollo program

text: Wiesner kept up the pressure, even making the disagreement public during a two-day September visit by the President to Marshall Space Flight Center. Wiesner blurted out "No, that's no good" in front of the press, during a presentation by von Braun. Webb jumped in and defended von Braun, until Kennedy ended the squabble by stating that the matter was "still subject to final review". Webb held firm and issued a request for proposal to candidate Lunar Excursion Module (LEM) contractors. Wiesner finally relented, unwilling to settle the dispute once and for all in Kennedy's office, because of the President's involvement with the October Cuban Missile Crisis, and fear of Kennedy's support for Webb. NASA announced the selection of Grumman as the LEM contractor in November 1962.


title: Apollo program

text: The LOR method had the advantage of allowing the lander spacecraft to be used as a "lifeboat" in the event of a failure of the command ship. Some documents prove this theory was discussed before and after the method was chosen. In 1964 an MSC study concluded, "The LM [as lifeboat]... was finally dropped, because no single reasonable CSM failure could be identified that would prohibit use of the SPS." Ironically, just such a failure happened on Apollo 13 when an oxygen tank explosion left the CSM without electrical power. The lunar module provided propulsion, electrical power and life support to get the crew home safely.


title: Apollo program

text: Faget's preliminary Apollo design employed a cone-shaped command module, supported by one of several service modules providing propulsion and electrical power, sized appropriately for the space station, cislunar, and lunar landing missions. Once Kennedy's Moon landing goal became official, detailed design began of a command and service module (CSM) in which the crew would spend the entire direct-ascent mission and lift off from the lunar surface for the return trip, after being soft-landed by a larger landing propulsion module. The final choice of lunar orbit rendezvous changed the CSM's role to the translunar ferry used to transport the crew, along with a new spacecraft, the Lunar Excursion Module (LEM, later shortened to LM (Lunar Module) but still pronounced ) which would take two individuals to the lunar surface and return them to the CSM.


title: Apollo program

text: The command module (CM) was the conical crew cabin, designed to carry three astronauts from launch to lunar orbit and back to an Earth ocean landing. It was the only component of the Apollo spacecraft to survive without major configuration changes as the program evolved from the early Apollo study designs. Its exterior was covered with an ablative heat shield, and had its own reaction control system (RCS) engines to control its attitude and steer its atmospheric entry path. Parachutes were carried to slow its descent to splashdown. The module was tall, in diameter, and weighed approximately .


title: Apollo program

text: A cylindrical service module (SM) supported the command module, with a service propulsion engine and an RCS with propellants, and a fuel cell power generation system with liquid hydrogen and liquid oxygen reactants. A high-gain S-band antenna was used for long-distance communications on the lunar flights. On the extended lunar missions, an orbital scientific instrument package was carried. The service module was discarded just before reentry. The module was long and in diameter. The initial lunar flight version weighed approximately fully fueled, while a later version designed to carry a lunar orbit scientific instrument package weighed just over .


title: Apollo program

text: North American Aviation won the contract to build the CSM, and also the second stage of the Saturn V launch vehicle for NASA. Because the CSM design was started early before the selection of lunar orbit rendezvous, the service propulsion engine was sized to lift the CSM off the Moon, and thus was oversized to about twice the thrust required for translunar flight. Also, there was no provision for docking with the lunar module. A 1964 program definition study concluded that the initial design should be continued as Block I which would be used for early testing, while Block II, the actual lunar spacecraft, would incorporate the docking equipment and take advantage of the lessons learned in Block I development.


title: Apollo program

text: The Apollo Lunar Module (LM) was designed to descend from lunar orbit to land two astronauts on the Moon and take them back to orbit to rendezvous with the command module. Not designed to fly through the Earth's atmosphere or return to Earth, its fuselage was designed totally without aerodynamic considerations and was of an extremely lightweight construction. It consisted of separate descent and ascent stages, each with its own engine. The descent stage contained storage for the descent propellant, surface stay consumables, and surface exploration equipment. The ascent stage contained the crew cabin, ascent propellant, and a reaction control system. The initial LM model weighed approximately , and allowed surface stays up to around 34 hours. An extended lunar module weighed over , and allowed surface stays of more than three days. The contract for design and construction of the lunar module was awarded to Grumman Aircraft Engineering Corporation, and the project was overseen by Thomas J. Kelly.


title: Apollo program

text: Before the Apollo program began, Wernher von Braun and his team of rocket engineers had started work on plans for very large launch vehicles, the Saturn series, and the even larger Nova series. In the midst of these plans, von Braun was transferred from the Army to NASA and was made Director of the Marshall Space Flight Center. The initial direct ascent plan to send the three-person Apollo command and service module directly to the lunar surface, on top of a large descent rocket stage, would require a Nova-class launcher, with a lunar payload capability of over . The June 11, 1962, decision to use lunar orbit rendezvous enabled the Saturn V to replace the Nova, and the MSFC proceeded to develop the Saturn rocket family for Apollo.


title: Apollo program

text: Since Apollo, like Mercury, used more than one launch vehicle for space missions, NASA used spacecraft-launch vehicle combination series numbers: AS-10x for Saturn I, AS-20x for Saturn IB, and AS-50x for Saturn V (compare Mercury-Redstone 3, Mercury-Atlas 6) to designate and plan all missions, rather than numbering them sequentially as in Project Gemini. This was changed by the time human flights began.


title: Apollo program

text: Since Apollo, like Mercury, would require a launch escape system (LES) in case of a launch failure, a relatively small rocket was required for qualification flight testing of this system. A rocket bigger than the Little Joe used by Mercury would be required, so the Little Joe II was built by General Dynamics/Convair. After an August 1963 qualification test flight, four LES test flights (A-001 through 004) were made at the White Sands Missile Range between May 1964 and January 1966.


title: Apollo program

text: Saturn I, the first US heavy lift launch vehicle, was initially planned to launch partially equipped CSMs in low Earth orbit tests. The S-I first stage burned RP-1 with liquid oxygen (LOX) oxidizer in eight clustered Rocketdyne H-1 engines, to produce of thrust. The S-IV second stage used six liquid hydrogen-fueled Pratt & Whitney RL-10 engines with of thrust. The S-V third stage flew inactively on Saturn I four times.


title: Apollo program

text: The first four Saturn I test flights were launched from LC-34, with only the first stage live, carrying dummy upper stages filled with water. The first flight with a live S-IV was launched from LC-37. This was followed by five launches of boilerplate CSMs (designated AS-101 through AS-105) into orbit in 1964 and 1965. The last three of these further supported the Apollo program by also carrying Pegasus satellites, which verified the safety of the translunar environment by measuring the frequency and severity of micrometeorite impacts.


title: Apollo program

text: In September 1962, NASA planned to launch four crewed CSM flights on the Saturn I from late 1965 through 1966, concurrent with Project Gemini. The payload capacity would have severely limited the systems which could be included, so the decision was made in October 1963 to use the uprated Saturn IB for all crewed Earth orbital flights.


title: Apollo program

text: The Saturn IB was an upgraded version of the Saturn I. The S-IB first stage increased the thrust to by uprating the H-1 engine. The second stage replaced the S-IV with the S-IVB-200, powered by a single J-2 engine burning liquid hydrogen fuel with LOX, to produce of thrust. A restartable version of the S-IVB was used as the third stage of the Saturn V. The Saturn IB could send over into low Earth orbit, sufficient for a partially fueled CSM or the LM. Saturn IB launch vehicles and flights were designated with an AS-200 series number, "AS" indicating "Apollo Saturn" and the "2" indicating the second member of the Saturn rocket family.


title: Apollo program

text: Saturn V launch vehicles and flights were designated with an AS-500 series number, "AS" indicating "Apollo Saturn" and the "5" indicating Saturn V. The three-stage Saturn V was designed to send a fully fueled CSM and LM to the Moon. It was in diameter and stood tall with its lunar payload. Its capability grew to for the later advanced lunar landings. The S-IC first stage burned RP-1/LOX for a rated thrust of , which was upgraded to . The second and third stages burned liquid hydrogen; the third stage was a modified version of the S-IVB, with thrust increased to and capability to restart the engine for translunar injection after reaching a parking orbit.


title: Apollo program

text: NASA's director of flight crew operations during the Apollo program was Donald K. "Deke" Slayton, one of the original Mercury Seven astronauts who was medically grounded in September 1962 due to a heart murmur. Slayton was responsible for making all Gemini and Apollo crew assignments.


title: Apollo program

text: Thirty-two astronauts were assigned to fly missions in the Apollo program. Twenty-four of these left Earth's orbit and flew around the Moon between December 1968 and December 1972 (three of them twice). Half of the 24 walked on the Moon's surface, though none of them returned to it after landing once. One of the moonwalkers was a trained geologist. Of the 32, Gus Grissom, Ed White, and Roger Chaffee were killed during a ground test in preparation for the Apollo 1 mission.


title: Apollo program

text: The Apollo astronauts were chosen from the Project Mercury and Gemini veterans, plus from two later astronaut groups. All missions were commanded by Gemini or Mercury veterans. Crews on all development flights (except the Earth orbit CSM development flights) through the first two landings on Apollo 11 and Apollo 12, included at least two (sometimes three) Gemini veterans. Dr. Harrison Schmitt, a geologist, was the first NASA scientist astronaut to fly in space, and landed on the Moon on the last mission, Apollo 17. Schmitt participated in the lunar geology training of all of the Apollo landing crews.


title: Apollo program

text: NASA awarded all 32 of these astronauts its highest honor, the Distinguished Service Medal, given for "distinguished service, ability, or courage", and personal "contribution representing substantial progress to the NASA mission". The medals were awarded posthumously to Grissom, White, and Chaffee in 1969, then to the crews of all missions from Apollo 8 onward. The crew that flew the first Earth orbital test mission Apollo 7, Walter M. Schirra, Donn Eisele, and Walter Cunningham, were awarded the lesser NASA Exceptional Service Medal, because of discipline problems with the flight director's orders during their flight. In October 2008, the NASA Administrator decided to award them the Distinguished Service Medals. For Schirra and Eisele, this was posthumously.


title: Apollo program

text: Two Block I CSMs were launched from LC-34 on suborbital flights in 1966 with the Saturn IB. The first, AS-201 launched on February 26, reached an altitude of and splashed down downrange in the Atlantic Ocean. The second, AS-202 on August 25, reached altitude and was recovered downrange in the Pacific Ocean. These flights validated the service module engine and the command module heat shield.


title: Apollo program

text: A third Saturn IB test, AS-203 launched from pad 37, went into orbit to support design of the S-IVB upper stage restart capability needed for the Saturn V. It carried a nose cone instead of the Apollo spacecraft, and its payload was the unburned liquid hydrogen fuel, the behavior of which engineers measured with temperature and pressure sensors, and a TV camera. This flight occurred on July 5, before AS-202, which was delayed because of problems getting the Apollo spacecraft ready for flight.


title: Apollo program

text: Two crewed orbital Block I CSM missions were planned: AS-204 and AS-205. The Block I crew positions were titled Command Pilot, Senior Pilot, and Pilot. The Senior Pilot would assume navigation duties, while the Pilot would function as a systems engineer. The astronauts would wear a modified version of the Gemini spacesuit.


title: Apollo program

text: After an uncrewed LM test flight AS-206, a crew would fly the first Block II CSM and LM in a dual mission known as AS-207/208, or AS-278 (each spacecraft would be launched on a separate Saturn IB). The Block II crew positions were titled Commander, Command Module Pilot, and Lunar Module Pilot. The astronauts would begin wearing a new Apollo A6L spacesuit, designed to accommodate lunar extravehicular activity (EVA). The traditional visor helmet was replaced with a clear "fishbowl" type for greater visibility, and the lunar surface EVA suit would include a water-cooled undergarment.


title: Apollo program

text: Deke Slayton, the grounded Mercury astronaut who became director of flight crew operations for the Gemini and Apollo programs, selected the first Apollo crew in January 1966, with Grissom as Command Pilot, White as Senior Pilot, and rookie Donn F. Eisele as Pilot. But Eisele dislocated his shoulder twice aboard the KC135 weightlessness training aircraft, and had to undergo surgery on January 27. Slayton replaced him with Chaffee. NASA announced the final crew selection for AS-204 on March 21, 1966, with the backup crew consisting of Gemini veterans James McDivitt and David Scott, with rookie Russell L. "Rusty" Schweickart. Mercury/Gemini veteran Wally Schirra, Eisele, and rookie Walter Cunningham were announced on September 29 as the prime crew for AS-205.


title: Apollo program

text: In December 1966, the AS-205 mission was canceled, since the validation of the CSM would be accomplished on the 14-day first flight, and AS-205 would have been devoted to space experiments and contribute no new engineering knowledge about the spacecraft. Its Saturn IB was allocated to the dual mission, now redesignated AS-205/208 or AS-258, planned for August 1967. McDivitt, Scott and Schweickart were promoted to the prime AS-258 crew, and Schirra, Eisele and Cunningham were reassigned as the Apollo1 backup crew.


title: Apollo program

text: The spacecraft for the AS-202 and AS-204 missions were delivered by North American Aviation to the Kennedy Space Center with long lists of equipment problems which had to be corrected before flight; these delays caused the launch of AS-202 to slip behind AS-203, and eliminated hopes the first crewed mission might be ready to launch as soon as November 1966, concurrently with the last Gemini mission. Eventually, the planned AS-204 flight date was pushed to February 21, 1967.


title: Apollo program

text: North American Aviation was prime contractor not only for the Apollo CSM, but for the SaturnV S-II second stage as well, and delays in this stage pushed the first uncrewed SaturnV flight AS-501 from late 1966 to November 1967. (The initial assembly of AS-501 had to use a dummy spacer spool in place of the stage.)