Timeline of the STS-51-L mission

The STS-51-L mission started with the ignition of Challenger's main engines until the remote destruction of the two Solid rocket boosters (SRBs), and includes a transcript of crew conversations from the cockpit voice recorder on board the orbiter.

However, at around T+36 seconds and an altitude of just over 3,000 m (9,800 ft), Challenger experienced the strongest wind shear ever felt during a Space Shuttle launch.

The pitch and yaw commanded by the shuttle's computers in order to counter this wind caused the solid fuel plug to become dislodged from the field joint on the right SRB.

[1] At around T+58 seconds, cameras noted the creation of a plume on the aft attachment strut on the right-hand SRB, as ignited gas began to force itself through a rapidly growing hole in the field joint.

At T+68, the CAPCOM informed the crew – "Challenger, go at throttle up", and Commander Francis R. "Dick" Scobee confirmed the call.

The last statement captured by the crew cabin recorder came just half a second after this acceleration, when Pilot Michael J. Smith said, "Uh oh".

Smith may also have been responding to onboard indications of main engine performance or to falling pressures in the external fuel tank.

[2] With the external tank disintegrating, Challenger veered from its correct attitude with respect to the local air flow and was immediately torn apart by aerodynamic forces, resulting in a load factor of up to 20g – well over its design limit.

The two SRBs, which could withstand greater aerodynamic loads, separated from the ET and continued in uncontrolled powered flight for another 37 seconds.

[4] The list also contains a transcript from the shuttle's Cockpit Voice Recorder (CVR), from ignition of the main engines to T+73 seconds.