Beginning at about T+37 and for 27 seconds, the shuttle experienced a series of wind shear events that were stronger than on any previous flight.

At T+58.788, a tracking film camera captured the beginnings of a plume near the aft attach strut on the right SRB.
Unknown to those on Challenger or in Houston, hot gas had begun to leak through a growing hole in one of the right-hand SRB joints.
The force of the wind shear shattered the temporary oxide seal that had taken the place of the damaged O-rings, removing the last barrier to flame passing through the joint.
Had it not been for the wind shear, the fortuitous oxide seal might have held through booster burnout.

Within a second, the plume became well defined and intense.
Internal pressure in the right SRB began to drop because of the rapidly enlarging hole in the failed joint, and at T+60.238 there was visual evidence of flame burning through the joint and impinging on the external tank.

At T+64.660, the plume suddenly changed shape, indicating that a leak had begun in the liquid hydrogen (LH2) tank, located in the aft portion of the external tank.
The nozzles of the main engines pivoted under computer control to compensate for the unbalanced thrust produced by the booster burn-through.
The pressure in the shuttle's external LH2 tank began to drop at T+66.764, indicating the effect of the leak.

At this stage the situation still seemed normal both to the crew and to flight controllers.
At T+68, the CAPCOM Richard O. Covey informed the crew that they were "go at throttle up", and Commander Dick Scobee confirmed, "Roger, go at throttle up"; this was the last communication from Challenger on the air-to-ground loop.
Beginning at about T+37 and for 27 seconds, the shuttle experienced a series of wind shear events that were stronger than on any previous flight.
At T+58.788, a tracking film camera captured the beginnings of a plume near the aft attach strut on the right SRB. Unknown to those on Challenger or in Houston, hot gas had begun to leak through a growing hole in one of the right-hand SRB joints. The force of the wind shear shattered the temporary oxide seal that had taken the place of the damaged O-rings, removing the last barrier to flame passing through the joint. Had it not been for the wind shear, the fortuitous oxide seal might have held through booster burnout.
Within a second, the plume became well defined and intense. Internal pressure in the right SRB began to drop because of the rapidly enlarging hole in the failed joint, and at T+60.238 there was visual evidence of flame burning through the joint and impinging on the external tank.
At T+64.660, the plume suddenly changed shape, indicating that a leak had begun in the liquid hydrogen (LH2) tank, located in the aft portion of the external tank. The nozzles of the main engines pivoted under computer control to compensate for the unbalanced thrust produced by the booster burn-through. The pressure in the shuttle's external LH2 tank began to drop at T+66.764, indicating the effect of the leak.
At this stage the situation still seemed normal both to the crew and to flight controllers. At T+68, the CAPCOM Richard O. Covey informed the crew that they were "go at throttle up", and Commander Dick Scobee confirmed, "Roger, go at throttle up"; this was the last communication from Challenger on the air-to-ground loop.
Space Shuttle Challenger disaster