Space Shuttle

• 1. Introduction

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  The Space Shuttle first left the ground on the 12th of April 1981, carried aloft by the combined fury of three main engines and two giant solid rocket boosters, piloted by John Young and Robert Crippen. It was a machine unlike anything humanity had built before: a spacecraft that launched like a rocket, orbited like a satellite, and landed like an airplane. For thirty years, across 135 missions, it carried people and cargo to and from low Earth orbit, built an international space station, deployed the Hubble Space Telescope, and flew into history. But the story of the Space Shuttle is also a story of staggering cost, two catastrophic disasters, and the tensions between ambition and safety. How did a program born from Cold War ambition become the backbone of American spaceflight? And what did it cost to get there?

• 2. A Long Road to Launch

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  Eugen Sanger and mathematician Irene Bredt sketched a winged rocket called the Silbervogel for the German government in the late 1930s, and the idea of a reusable spaceplane never quite left the engineering imagination. By the 1950s, the U.S. Air Force was studying piloted gliders for reconnaissance and satellite attack. In the late 1950s, the Air Force began developing the partially reusable X-20 Dyna-Soar, training six pilots for it as early as June 1961. Rising costs and the pull of Project Gemini killed the program in December 1963.

  NASA and the Air Force had also spent years testing lifting bodies - aircraft that generated lift from their fuselages rather than wings - testing designs including the Northrop M2-F2, the Northrop HL-10, and the Martin Marietta X-24B. These experiments proved that an unpowered vehicle could glide from high altitude and high speed to a runway, which was exactly what the shuttle would later do.

  On the 24th of September 1966, as the Apollo program neared completion, a joint NASA and Air Force study concluded that a new vehicle was needed and that partial reusability was the most cost-effective path. George Mueller, head of NASA's Office of Manned Space Flight, announced the plan for a reusable shuttle on the 10th of August 1968. Study contracts went to General Dynamics, Lockheed, McDonnell Douglas, and North American Rockwell. By July 1969, a task group envisioned three classes of shuttle: an orbiter on expendable boosters, a stage-and-a-half design, and a fully reusable orbiter plus booster.

  Max Faget, the NASA engineer who helped design the Mercury capsule, patented a straight-winged, fully recoverable two-stage design. The Air Force objected: a straight wing could not survive reentry stresses or meet cross-range and payload requirements. In January 1971, NASA and Air Force leadership settled on a delta-wing orbiter riding an expendable propellant tank. The Air Force required the payload bay to measure 15 by 60 ft and demanded the ability to lift 65,000 lb to an eastward orbit. In July 1971, NASA contracted Rocketdyne to develop the RS-25 engine. The final design was approved in March 1972, after President Richard Nixon gave the program his blessing in January of that year.

• 3. Building the Machine

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  On the 4th of June 1974, Rockwell broke ground on OV-101, a test vehicle originally named Constitution and later renamed Enterprise. Construction finished on the 17th of September 1976, and Enterprise was moved to Edwards Air Force Base to begin testing. Because it was a test vehicle, Enterprise carried no engines and no heat shielding.

  On the 12th of August 1977, Enterprise conducted its first free glide test, detaching from the back of a modified Boeing 747 and landing at Edwards. After four more flights, it moved to the Marshall Space Flight Center for vibration tests that simulated the stresses of launch. Enterprise later served in development of the launch complex at Vandenberg Air Force Base in 1984.

  The RS-25 main engine caused serious headaches. Pratt and Whitney challenged the contract awarded to Rocketdyne, delaying development by nine months. When the first engine was finally completed in March 1975, testing revealed multiple nozzle failures and broken turbine blades. Despite those problems, NASA ordered the nine engines needed for its three orbiters under construction in May 1978.

  Columbia, the first fully operational orbiter, presented its own difficulties. Construction began on the 27th of March 1975, and the vehicle was delivered to Kennedy Space Center on the 25th of March 1979 - but it still had 6,000 of its 30,000 thermal protection tiles to be installed at that point. Worse, many already-installed tiles had to be replaced. Two years of tile work followed before Columbia could fly.

  NASA chose ceramic tiles over the ablative heat shields used on earlier spacecraft because individual tiles could be replaced as needed. The tiles had to hold the orbiter's aluminum skin below 350 degrees Fahrenheit even as reentry pushed surface temperatures to 3,000 degrees. The nose cone and wing leading edges, the hottest spots of all, used reinforced carbon-carbon tiles. Other areas used borosilicate glass-coated silica fiber tiles or Nomex felt, depending on how much heat each surface faced.

  External tank construction was awarded to Martin Marietta in August 1973, and Morton Thiokol received the solid rocket booster contract in November 1973. The tank stood 153.8 ft tall and 27.6 ft wide. The solid rocket boosters were the largest solid-propellant motors ever flown: each 149.2 ft tall and 12.2 ft wide, packed with over 1.1 million lb of propellant. Challenger, Discovery, and Atlantis were ordered on the 29th of January 1979. Construction of a fifth orbiter, Endeavour, began in February 1982, though NASA later capped the fleet at four.

• 4. How It Flew

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  At T-6.6 seconds, the three RS-25 engines lit sequentially at 120-millisecond intervals. The engines had to reach 90 percent rated thrust by T-3 seconds or the computers would abort the launch. While the engines fired but before the solid rocket boosters ignited, the offset thrust bent the entire stack forward by 25.5 inches at the tip of the external tank. Engineers called this the "twang." The stack swung back toward vertical, and at T-0, eight frangible nuts detonated, the solid rocket boosters ignited, and the shuttle left the pad.

  The solid rocket boosters provided 71.4 percent of thrust at liftoff, each producing 2.8 million lbf of thrust - later raised to 3 million lbf beginning with STS-8. About 123 seconds after launch, at roughly 150,000 ft, pyrotechnic fasteners released the boosters. They coasted to an apogee of 220,000 ft before parachuting into the Atlantic Ocean, where recovery ships named MV Freedom Star and MV Liberty Star retrieved them. The rocket motors were then shipped to Thiokol for refurbishment and reuse.

  The main engines continued burning until about 8 minutes 30 seconds after launch. The external tank separated 18 seconds after engine cutoff, tumbled, broke up during reentry, and fell into the Indian or Pacific Ocean. It was the only major component never reused. Two firings of the smaller Orbital Maneuvering System engines then raised and circularized the orbit. Mission altitudes ranged from 120 to 335 nautical miles.

  Reentry began at 400,000 ft, traveling at approximately Mach 25. The computers flew the vehicle through a precise angle-of-attack plan to manage heating, and a series of banking roll reversals controlled the descent path. Descending through 150,000 ft, the speed brake on the vertical stabilizer opened. Below 10,000 ft, the crew took manual control, following a 20 or 18 degree glideslope at roughly 167 ft per second. The landing gear deployed 10 seconds before touchdown from an altitude of 300 ft. After wheels stopped, a drag chute deployed from the vertical stabilizer. Of the 133 successful landings, 78 occurred at Kennedy Space Center and 54 at Edwards Air Force Base.

• 5. Science, Satellites, and Station

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  STS-5, the first operational mission in 1982, established the basic rhythm of shuttle work: launching satellites and conducting experiments. Early missions routinely deployed commercial and government satellites. The shuttle's 60 by 15 ft payload bay could carry cylindrical payloads up to 15 ft in diameter, and the Canadarm - built by Canadian company Spar Aerospace - could deploy or retrieve payloads up to 65,000 lb, a figure later improved to 586,000 lb.

  The Spacelab module, funded by Europe, turned the payload bay into a pressurized laboratory. Astronauts reached it through a tunnel measuring either 8.72 or 18.88 ft. Spacelab flew on 28 missions through 1999, supporting research in astronomy, microgravity, radar, and life sciences, as well as servicing the Hubble Space Telescope and resupplying space stations.

  Beginning with STS-71, the shuttle began docking with Russia's Mir space station, a relationship that prefigured the International Space Station. In the shuttle's final decade, ISS construction became its primary purpose. The 17 day 15 hour STS-80 mission held the record as the longest shuttle flight.

  The National Reconnaissance Office, responsible for spy satellites, was a key shuttle customer throughout the program. Its relationship with the shuttle was classified until 1993. Following the Challenger disaster, NASA shifted many commercial payloads to expendable rockets such as the Delta II, and the shuttle's role tilted further toward scientific and government missions. The final payload specialist flew on STS-51-L; thereafter, all non-pilot crew members were designated mission specialists.

• 6. Challenger and Columbia

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  On the 28th of January 1986, Challenger broke apart 73 seconds after launch, killing all seven crew members of STS-51-L. A single O-ring seal between segments of the right solid rocket booster had failed in cold temperatures. Hot combustion gases escaped, burned through the external tank, and triggered a catastrophic sequence. Engineers had repeatedly warned managers that O-rings became unreliable below 53 degrees Fahrenheit, but those warnings went unheeded.

  After the disaster, NASA resumed production of a replacement orbiter, Endeavour, in September 1987. The solid rocket boosters were redesigned to maintain a constant seal regardless of ambient temperature. Crew members were also given the Launch Entry Suit, a partial-pressure garment replacing the light nomex flight suits worn since STS-5. In 1994, that suit was itself replaced by the full-pressure Advanced Crew Escape Suit.

  On the 1st of February 2003, Columbia disintegrated during reentry, again killing all seven on board. A piece of insulating foam had broken off the external tank during launch and struck the carbon-carbon leading edge of the wing. Ground engineers made three requests for high-resolution Department of Defense satellite images that might have shown the extent of the damage. NASA managers blocked those requests. NASA's chief thermal protection system engineer asked that the crew be allowed to conduct a spacewalk to inspect the damage; that request was refused as well. A rescue by Atlantis and the possibility of astronaut repair were never evaluated by management at the time.

  Early NASA safety analyses had put the chance of catastrophic failure anywhere from 1 in 100 to 1 in 100,000 launches. After both disasters, retrospective analysis placed the probability of catastrophic loss as high as 1 in 9 for the earliest missions. Both official accident reports concluded that NASA's organizational culture had failed to weigh crew safety against the pressure to maintain mission rates.

• 7. Cost and Legacy

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  The total Space Shuttle program budget has been estimated at $221 billion in 2012 dollars. The 1972 development estimates projected a per-pound payload cost as low as $1,109 in 2012 dollars; the actual cost, excluding research and development, came out to $37,207 per pound. A 1982 NASA estimate put per-flight cost at $260 million, premised on 24 flights per year over a decade - a rate the shuttle never approached. From 1995 to 2002, when operations were most stable, each launch cost $806 million. Accounting for the entire program, the per-launch average reached $1.642 billion in 2012 dollars.

  Retirement was announced in January 2004 by President George W. Bush as part of his Vision for Space Exploration. The shuttle would complete ISS construction and then stand down. STS-134 had been planned as the final mission, but Atlantis was kept ready as a rescue vehicle and ultimately flew as STS-135 with a four-person crew. It landed at Kennedy Space Center on the 21st of July 2011, at 5:57 a.m. EDT. From that moment until the 30th of May 2020, the United States launched its astronauts on Russian Soyuz spacecraft.

  The surviving orbiters went on public display: Atlantis at the Kennedy Space Center Visitor Complex, Discovery at the Steven F. Udvar-Hazy Center in Virginia, Endeavour at the California Science Center in Los Angeles, and Enterprise at the Intrepid Museum in New York. The RS-25 engines were not retired. They were removed and transferred for use on the Space Launch System. Artemis I alone carried components that had flown on 83 of the 135 Space Shuttle missions, some of which dated to the early 1980s.