On January 28, 1986, the NASA Space Shuttle orbiter undertaking mission STS-51-L and the tenth flight of Space Shuttle Challenger (OV-099) broke apart 73 seconds into its flight, killing all seven crew members: five NASA astronauts, one payload specialist, and a civilian school teacher.

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.

 

Approximately 17 percent of the American population witnessed the launch on live television broadcast because of the presence of high school teacher Christa McAuliffe, who would have been the first teacher in space. The Challenger disaster has been since been used as a case study in many discussions of engineering safety and workplace ethics.

 

STS-51-L crew: (front row) Michael J. Smith, Dick Scobee, Ronald McNair; (back row) Ellison Onizuka, Christa McAuliffe, Gregory Jarvis, Judith Resnik