Their bosses however, feeling the pressure to launch after a week of delays and in the full glare of the public spotlight due to the presence of the first "teacher in space" (Christa McAuliffe) among the crew, overroad their engineers and gave STS-51L the green light.
They should have listened.
Just 73 seconds after lift off the Thiokold engineer's worst nightmares were realized as super-heated gas leaking through a failed O-ring on the right hand SRB burned through the external fuel tank causing a cascading series of events that led to the breakup of the Shuttle Challenger 48,000 feet over the Atlantic. Contrary to popular belief at the time the Shuttle was not torn apart by the explosion of gases in the external fuel tank but instead by aerodynamic forces exerted on the orbiter when it veered off its intended trajectory due to thrust anomolies coming from the right SRB (which had broken loose) and the external fuel tank. The last words heard from Pilot Michael Smith just milliseconds before the orbitor was torn apart were an ominous "Uh oh."
In a grissly discovery made some weeks later it was learned that several members of the crew had apparently survived the orbiter's breakup and activated their emergency oxygen supplies. Indeed Pilot Michael Smith - in a valiant but hopeless attempt to gain control of the situation - had been working the control panel, activating switches in an apparent attempt to restore electicity after the breakup. Because of these discoveries many experts now believe that at least some of the crew members survived the entire 2 minute 45 second free fall to the ocean's surface and that it was that impact with the water - at 207 mph - that was the likely cause of death, not the explosion or orbiter's initial breakup.
In the aftermath of the Challenger disaster the Shuttle program was grounded for 31 months while changes to the decision making culture at NASA as well as new, more robust safety procedures were implemented.
The crew of STS-51L were: Dick Scobee, Michael J. Smith, Greg Jarvis, Judith Resnik, Ronald McNair, Ellison Onizuka and Christa McAuliffe.