Construction

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.^[3] 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.^[4] 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.^[5] 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.^[6]

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.^[4]

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.^[4] 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.

Flights and modifications

After its first flight in April 1983, Challenger quickly became the workhorse of NASA's Space Shuttle fleet, flying six of nine Space Shuttle missions in 1983 and 1984. Even when the orbiters Discovery and Atlantis joined the fleet, Challenger flew three missions a year from 1983 to 1985. Challenger, along with Atlantis, was modified at Kennedy Space Center to be able to carry the Centaur-G upper stage in its payload bay. If flight STS-51-L had been successful, Challenger's next mission would have been the deployment of the Ulysses probe with the Centaur to study the polar regions of the Sun.

Challenger flew the first American woman, African-American, Dutchman, and Canadian into space; carried three Spacelab missions; and performed the first night launch and night landing of a Space Shuttle.

Final mission and destruction

STS-51-L was the orbiter's tenth and final flight, initially planned to launch on January 26, 1986 (after several technical and paperwork delays). This mission attracted huge media attention, as one of the crew was a civilian schoolteacher, Christa McAuliffe, who was assigned to carry out live lessons from the orbiter (as part of NASA's Teacher in Space Project). Other members would deploy the TDRS-B satellite and conduct comet observations.

Challenger blasted off at 11:38 am EST on January 28, 1986. Just over a minute into the flight, a faulty booster joint opened up, leading to a flame that melted securing struts which resulted in a catastrophic structural failure and explosion of the External Tank. The resulting pressure waves and aerodynamic forces destroyed the orbiter, resulting in the loss of all of the crew.

Challenger was the first Space Shuttle to be destroyed in a mission disaster.^[9] The collected debris of the vessel is currently buried in decommissioned missile silos at Launch Complex 31, Cape Canaveral Air Force Station. A section of the fuselage recovered from Space Shuttle Challenger can also be found at the "Forever Remembered" memorial at the Kennedy Space Center Visitor Complex in Florida. Debris from the orbiter sometimes washes up on the Florida coast.^[10] This is collected and transported to the silos for storage. Because of its early loss, Challenger was the only Space Shuttle that never wore the NASA "meatball" logo, and was never modified with the MEDS "glass cockpit". The tail was never fitted with a drag chute, which was fitted to the remaining orbiters in 1992. Challenger and sister ship Columbia are the only two shuttles that never visited the Mir Space Station or the International Space Station. In September 2020 Netflix released Challenger: The Final Flight, a four-part miniseries created by Steven Leckart and Glen Zipper documenting the tragedy firsthand.

Lawsuits

In March 1988 the federal government and Morton Thiokol Inc. agreed to pay $7.7 million in cash and annuities to the families of four of the seven Challenger astronauts as part of a settlement aimed at avoiding lawsuits in the nation's worst space disaster, according to government documents. The documents show that Morton Thiokol, which manufactured the faulty solid rocket boosters blamed for the accident, paid 60 percent, or $4,641,000. The remainder, $3,094,000, was paid by the government.

In September 1988 a federal judge dismissed two lawsuits seeking $3 billion from Space Shuttle rocket-maker Morton Thiokol Inc. by Roger Boisjoly, a former company engineer who warned against the ill-fated 1986 Challenger launch.^[11]