Space Shuttle Challenger (NASA Orbiter Vehicle Designation: OV-099) was NASA's second Space Shuttle orbiter to be put into service, after Columbia. Its maiden voyage was on April 4, 1983, and it made eight further round trips to low earth orbit before breaking up 73 seconds after the launch of its tenth mission, on January 28, 1986, killing all seven crew members. (For more on the Challenger disaster, see Space Shuttle Challenger disaster.) It would be replaced by the space shuttle Endeavour, launched six years after the 51-L disaster.

Challenger was constructed using a body frame (STA- 099) that had initially been built as a test article. STA-099 was not originally intended for spaceflight, but NASA discovered that recycling it would be less expensive than refitting the test shuttle Enterprise (OV-101) to be spaceworthy, as originally planned. The spacecraft was named after the HMS Challenger, a British corvette which carried out a pioneering global marine research expedition in the 1870s[1]. Unlike Columbia, Challenger was the first Orbiter to be delivered with fewer tiles on its Thermal Protection System. Most of the tiles were replaced with DuPont white nomex felt insulation on the payload bay doors, upper wing surface and rear fuselage surface, allowing Challenger to carry 2,500 lbs. more than Columbia. It was also the first Orbiter to have a heads-up display system similar to those found in military and newer civilian aircraft to allow the commander and pilot to see important data during reentry and landing, eliminating the need to look at the instrument panel during descent and allowing them to concentrate on flying the Orbiter.

Challenger, along with Discovery was modified at KSC to be able to carry the Centaur-G upper-stage in its payload bay. Had STS-51-L 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 was one of two space shuttles destroyed in an accident during a mission, the other being Columbia. The collected debris of the vessel are currently stored in decommissioned missile silos at Cape Canaveral Air Force Station. From time to time, further pieces of debris from the orbiter wash up on the Florida coast. When this happens, they are collected and transported to the silos for storage. Because of her early loss, Challenger is the only space shuttle that never wore the NASA "meatball" logo.

Challenger was destroyed in the second minute of STS-51-L, the orbiter's tenth mission, on January 28, 1986, when an O-ring seal on its right solid rocket booster failed due to record low temperatures. The O-ring became brittle and allowed a plume of flame to stream out of the SRB that weakened Challenger's external fuel tank, leading to the orbiter's rapid breakup under aerodynamic stresses. A subsequent investigation concluded that poor design of the SRB seals, unusually cold temperatures that weakened the O-rings, and lack of inspection were to blame for the disaster. Dr. Richard Feynman from the Rogers Commission, who discovered the flaw, publicly demonstrated his finding with nothing more than a sample of o-ring material, a clamp, and a glass of ice water.