Space Shuttle Challenger

Space Shuttle Challenger (OV-099) was a Space Shuttle orbiter manufactured by Rockwell International and operated by NASA. Named after the commanding ship of a nineteenth-century scientific expedition that traveled the world, Challenger was the second Space Shuttle orbiter to fly into space after Columbia, and launched on its maiden flight in April 1983. It was destroyed in January 1986 soon after launch in a disaster that killed all seven crewmembers aboard.

Initially manufactured as a test article not intended for spaceflight, it was used for ground testing of the Space Shuttle orbiter's structural design. However, after NASA found that their original plan to upgrade Enterprise for spaceflight would be more expensive than upgrading Challenger, the orbiter was pressed into operational service in the Space Shuttle program. Lessons learned from the first orbital flights of Columbia led to Challenger's design possessing fewer thermal protection system tiles and a lighter fuselage and wings. This led to it being 2,200 pounds (1,000 kilograms) lighter than Columbia, though still 5,700 pounds (2,600 kilograms) heavier than Discovery.

During its three years of operation, Challenger was flown on ten missions in the Space Shuttle program, spending over 62 days in space and completing almost 1,000 orbits around Earth. Following its maiden flight, Challenger supplanted Columbia as the leader of the Space Shuttle fleet, being the most-flown orbiter during all three years of its operation while Columbia itself was seldom used during the same time frame. Challenger was used for numerous civilian satellite launches, such as the first tracking and data relay satellite, the Palapa B communications satellites, the Long Duration Exposure Facility, and the Earth Radiation Budget Satellite. It was also used as a test bed for the Manned Maneuvering Unit (MMU) and served as the platform to repair the malfunctioning SolarMax telescope. In addition, three consecutive Spacelab missions were conducted with the orbiter in 1985, one of which being the first German crewed spaceflight mission. Passengers carried into orbit by Challenger include the first American female astronaut, the first American female spacewalker, the first African-American astronaut, and the first Canadian astronaut.

On its tenth flight in January 1986, Challenger broke up 73 seconds after liftoff, killing the seven-member crew of STS-51-L that included Christa McAuliffe, who would have been the first teacher in space. The Rogers Commission concluded that an O-ring seal in one of Challenger's solid rocket boosters failed to contain pressurized burning gas that leaked out of the booster, causing a structural failure of Challenger's external tank and the orbiter's subsequent breakup due to aerodynamic forces. NASA's organizational culture was also scrutinized by the Rogers Commission, and the Space Shuttle program's goal of replacing the United States' expendable launch systems was cast into doubt. The loss of Challenger and its crew led to a broad rescope of the program including replacing it with Endeavour, and numerous aspects — such as launches from Vandenberg, the MMU, and Shuttle-Centaur — were scrapped to improve crew safety; Challenger and Atlantis were the only orbiters modified to conduct Shuttle-Centaur launches. The recovered remains of the orbiter are mostly buried in a missile silo located at Cape Canaveral LC-31; one piece is on display at the Kennedy Space Center Visitor Complex.

Challenger was named after HMS Challenger, a British corvette that was the command ship for the Challenger Expedition, a pioneering global marine research expedition undertaken from 1872 through 1876. The Apollo 17 Lunar Module, which landed on the Moon in 1972, was also named Challenger.

Because of the low production volume of orbiters, the Space Shuttle program decided to build a vehicle as a Structural Test Article, STA-099, that could later be converted to a flight vehicle. The contract for STA-099 was awarded to North American Rockwell on July 26, 1972, and construction was completed in February 1978. After STA-099's rollout, it was sent to a Lockheed test site in Palmdale, where it spent over 11 months in vibration tests designed to simulate entire shuttle flights, from launch to landing. To prevent damage during structural testing, qualification tests were performed to a safety factor of 1.2 times the design limit loads. The qualification tests were used to validate computational models, and compliance with the required 1.4 factor of safety was shown by analysis. STA-099 was essentially a complete airframe of a Space Shuttle orbiter, with only a mockup crew module installed and thermal insulation placed on its forward fuselage.

NASA planned to refit the prototype orbiter Enterprise (OV-101), used for flight testing, as the second operational orbiter; but Enterprise lacked most of the systems needed for flight, including a functional propulsion system, thermal insulation, a life support system, and most of the cockpit instrumentation. Modifying it for spaceflight was considered to be too difficult, expensive, and time-consuming. Since STA-099 was not as far along in the construction of its airframe, it would be easier to upgrade to a flight article. Because STA-099's qualification testing prevented damage, NASA found that rebuilding STA-099 into a flightworthy orbiter would be less expensive than refitting Enterprise. Work on converting STA-099 to operational status began in January 1979, starting with the crew module (the pressurized portion of the vehicle), as the rest of the vehicle was still being used for testing by Lockheed. STA-099 returned to the Rockwell plant in November 1979, and the original, unfinished crew module was replaced with the newly constructed model. Major parts of STA-099, including the payload bay doors, body flap, wings, and vertical stabilizer, also had to be returned to their individual subcontractors for rework. By early 1981, most of these components had returned to Palmdale to be reinstalled. Work continued on the conversion until July 1982, when the new orbiter was rolled out as Challenger.

Challenger, as did the orbiters built after it, had fewer tiles in its Thermal Protection System than Columbia, though it still made heavier use of the white LRSI tiles on the cabin and main fuselage than did the later orbiters. Most of the tiles on the payload bay doors, upper wing surfaces, and rear fuselage surfaces were replaced with DuPont white Nomex felt insulation. These modifications and an overall lighter structure allowed Challenger to carry 2,500 lb (1,100 kg) more payload than Columbia. Challenger's fuselage and wings were stronger and lighter than Columbia's. The hatch and vertical-stabilizer tile patterns were different from those of the other orbiters. Challenger was the first orbiter to have a heads-up display (HUD) system for use in the descent phase of a mission, and the first to feature Phase I main engines rated for 104% maximum thrust.