Challenger (STS-51-L) explodes 73 seconds after launch 1986

STS-51-L crew 

Back row (L-R): Ellison Onizuka, Christa McAuliffe, Gregory Jarvis, Judith Resnik. 

Front row (L-R): Michael J. Smith, Francis "Dick" Scobee, Ronald McNair.

STS-51-L Mission patch

Space Shuttle Challenger (STS-51-L), launched January 28, 1986, exploded 73 seconds after launch.  The cause of the disaster was determined to have been a failure of an O-ring seal on the starboard Solid Rocket Booster.  The disaster grounded the space shuttle program for 32 months.  Its crew consisted of Commander Francis Scobee, Pilot Michael Smith, Ellison Onizuka, Judith Resnick, Ronald McNair, Gregory Jarvis and Christa McAuliffe.  All crew perished in the disaster.