The Space Shuttle Challenger disaster was a fatal incident in the United States space program that occurred on Tuesday, January 28, 1986, when the Space Shuttle Challenger (OV-099) broke apart 73 seconds into its flight, killing all seven crew members aboard. The crew consisted of five NASA astronauts, one payload specialist, and a civilian schoolteacher. The mission carried the designation STS-51-L and was the tenth flight for the Challenger orbiter.
The spacecraft disintegrated over the Atlantic Ocean, off the coast of Cape Canaveral, Florida, at 11:39 a.m. EST (16:39 UTC). The disintegration of the vehicle began after a joint in its right solid rocket booster (SRB) failed at liftoff. The failure was caused by the failure of O-ring seals used in the joint that were not designed to handle the unusually cold conditions that existed at this launch. The seals’ failure caused a breach in the SRB joint, allowing pressurized burning gas from within the solid rocket motor to reach the outside and impinge upon the adjacent SRB aft field joint attachment hardware and external fuel tank. This led to the separation of the right-hand SRB’s aft field joint attachment and the structural failure of the external tank. Aerodynamic forces broke up the orbiter.