STS-51-L was the 25th mission of the NASA Space Shuttle program, the program to carry out routine transportation for Earth-to-orbit crew and cargo; as well as the final flight of Space Shuttle Challenger.

Planned as the first Teacher in Space Project in addition to observing Halley's Comet for six days, the mission never achieved orbit; a structural failure during its ascent phase 73 seconds after launch from Kennedy Space Center Launch Complex 39B on January 28, 1986, killed all seven crew members – Commander Francis R. "Dick" Scobee, Pilot Michael J. Smith, Mission Specialists Ellison S. Onizuka, Judith A. Resnik and Ronald E. McNair, and Payload Specialists Gregory B. Jarvis and S. Christa McAuliffe – and destroyed the orbiter.

Immediately after the disaster, President Ronald Reagan convened the Rogers Commission to determine the cause of the explosion. The failure of an O-ring seal on the starboard Solid Rocket Booster (SRB) was determined to have caused the shuttle to break-up in flight. Space Shuttle flights were suspended while the hazards with the vehicle were addressed. Shuttle missions resumed in September 1988 with STS-26, launched 32 months after the accident.

.999 fine silver