Editorial use only STS-51L payload specialists taking a break from emergency egress training at the Johnson Space Center's (JSC) Shuttle Mock-up and Integration Laboratory. From left to right: Gregory Jarvis (1944-1986) of Hughes, Sharon Christa McAuliffe (1948-1986) and Barbara Morgan (born 1951) of the Teacher-in-Space Project. McAuliffe was selected as NASA's first citizen observer in the Space Shuttle Program and Morgan was named her backup. The NASA shuttle Challenger mission 51-L exploded seventy three seconds after lift off on the 28th January 1986. All seven crew members were killed. It is thought that the accident was caused by a failure of an 0-ring in a seal on the right hand solid rocket booster, with consequent ignition of the leaking fuel.