Photo Credit: NASAĪ little under eight seconds into the mission, Challenger cleared the tower of Pad 39B and began a programmed roll maneuver, moving onto the correct flight azimuth for a 28.45-degree-inclination orbit, then pitching onto her back under the control of her General Purpose Computers (GPCs). The photo shows an unusual plume in the lower part of the right-hand Solid Rocket Booster (SRB). This still photo of the STS-51L launch was taken from Camera Pad 10 north of Launch Complex 39B at 59.82 seconds after launch. By an incredible sequence of events, a chunk of solid fuel temporarily plugged the O-ring hole and the first minute of Challenger’s ascent proceeded normally. Years later, Morton Thiokol structural engineer Roger Boisjoly expressed profound astonishment that the vehicle did not explode on the launch pad. Any flame from the compromised booster could now play on the tank like a blowtorch, igniting its contents in a fireball and destroying Challenger, together with the entire launch complex. ![]() More significantly, the point of failure directly faced the External Tank and its volatile load of liquid oxygen and hydrogen propellants, which fed the shuttle’s main engines. The camera had identified the tell-tale result of both the primary and secondary O-rings-which were meant to stop searing gases from escaping between the booster-segment joints-failing, disintegrating, and streaming away in the moments after ignition. Had STS-51L succeeded, its primary objective was the deployment of the second NASA Tracking and Data Relay Satellite (TDRS-B), atop a Boeing-built Inertial Upper Stage (IUS). Clear evidence of the boosters’ fallibility, made public for the first time by the Rogers Commission into the tragedy, occurred serendipitously when, 0.678 seconds after liftoff, a video camera mounted close to Pad 39B captured “a strong puff of grey smoke…spurting from the vicinity of the aft field joint of the right Solid Rocket Booster.” It proved to be the failure of both the primary and secondary O-ring seals at the base of the right-hand booster, investigators would later conclude from photographic, physical and other evidence, that was directly responsible for the destruction of Challenger that day. ![]() Six and a half seconds before liftoff, Challenger’s three main engines thundered alive and, as the countdown clock touched zero, the assembled spectators at the Kennedy Space Center (KSC) were greeted by the ear-splitting staccato crackle of her twin Solid Rocket Boosters (SRBs). Members of the 51L flight crew during classroom training.
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