At T+72.284, the right SRB pulled away from the aft strut attaching it to the external tank.
Later analysis of telemetry data showed a sudden lateral acceleration to the right at T+72.525, which may have been felt by the crew.
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.

At T+73.124, the aft dome of the liquid hydrogen tank failed, producing a propulsive force that rammed the hydrogen tank into the LOX tank in the forward part of the ET.
At the same time, the right SRB rotated about the forward attach strut, and struck the intertank structure.
The external tank at this point suffered a complete structural failure, the LH2 and LOX tanks rupturing, mixing, and igniting, creating a fireball that enveloped the whole stack.

The breakup of the vehicle began at T+73.162 seconds and at an altitude of 48,000 feet (15 km).
With the external tank disintegrating (and with the semi-detached right SRB contributing its thrust on an anomalous vector), Challenger veered from its correct attitude with respect to the local airflow, resulting in a load factor of up to 20 g, well over its design limit of 5 g and was quickly ripped apart by abnormal aerodynamic forces (the orbiter did not explode as is often suggested, as the force of the external tank breakup was well within its structural limits).
The two SRBs, which could withstand greater aerodynamic loads, separated from the ET and continued in uncontrolled powered flight.
The SRB casings were made of half-inch-thick (12.7 mm) steel and were much stronger than the orbiter and ET; thus, both SRBs survived the breakup of the space shuttle stack, even though the right SRB was still suffering the effects of the joint burn-through that had set the destruction of Challenger in motion.

The more robustly constructed crew cabin also survived the breakup of the launch vehicle, as it was designed to survive 20 psi (140 kPa) while the estimated pressure it had been subjected to during orbiter breakup was only about 4–5 psi (28–34 kPa).
While the SRBs were subsequently destroyed remotely by the Range Safety Officer, the detached cabin continued along a ballistic trajectory and was observed exiting the cloud of gases at T+75.237.
Twenty-five seconds after the breakup of the vehicle, the altitude of the crew compartment peaked at a height of 65,000 feet (20 km).
The cabin was stabilized during descent by the large mass of electrical wires trailing behind it.
At T+76.437 the nose caps and drogue parachutes of the SRBs separated, as designed, and the drogue of the right-hand SRB was seen by a tracking camera, bearing the frustum and its location aids.

The Thiokol engineers who had opposed the decision to launch were watching the events on television.
They had believed that any O-ring failure would have occurred at liftoff, and thus were happy to see the shuttle successfully leave the launch pad.
At about one minute after liftoff, a friend of Boisjoly said to him "Oh God.
We made it.
We made it!"
Boisjoly recalled that when the shuttle was destroyed a few seconds later, "we all knew exactly what happened".
Veteran astronaut Robert Crippen was preparing to command STS-62-A, scheduled for mid-year, when his crew stopped training to watch the launch.
Pete Aldridge recalled, "I was waiting for the orbiter, as we all were, to come out of the smoke.
But as soon as that explosion occurred, Crippen obviously knew what it was.
His head dropped.
I remember this so distinctly".
At T+72.284, the right SRB pulled away from the aft strut attaching it to the external tank. Later analysis of telemetry data showed a sudden lateral acceleration to the right at T+72.525, which may have been felt by the crew. 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.
At T+73.124, the aft dome of the liquid hydrogen tank failed, producing a propulsive force that rammed the hydrogen tank into the LOX tank in the forward part of the ET. At the same time, the right SRB rotated about the forward attach strut, and struck the intertank structure. The external tank at this point suffered a complete structural failure, the LH2 and LOX tanks rupturing, mixing, and igniting, creating a fireball that enveloped the whole stack.
The breakup of the vehicle began at T+73.162 seconds and at an altitude of 48,000 feet (15 km). With the external tank disintegrating (and with the semi-detached right SRB contributing its thrust on an anomalous vector), Challenger veered from its correct attitude with respect to the local airflow, resulting in a load factor of up to 20 g, well over its design limit of 5 g and was quickly ripped apart by abnormal aerodynamic forces (the orbiter did not explode as is often suggested, as the force of the external tank breakup was well within its structural limits). The two SRBs, which could withstand greater aerodynamic loads, separated from the ET and continued in uncontrolled powered flight. The SRB casings were made of half-inch-thick (12.7 mm) steel and were much stronger than the orbiter and ET; thus, both SRBs survived the breakup of the space shuttle stack, even though the right SRB was still suffering the effects of the joint burn-through that had set the destruction of Challenger in motion.
The more robustly constructed crew cabin also survived the breakup of the launch vehicle, as it was designed to survive 20 psi (140 kPa) while the estimated pressure it had been subjected to during orbiter breakup was only about 4–5 psi (28–34 kPa). While the SRBs were subsequently destroyed remotely by the Range Safety Officer, the detached cabin continued along a ballistic trajectory and was observed exiting the cloud of gases at T+75.237. Twenty-five seconds after the breakup of the vehicle, the altitude of the crew compartment peaked at a height of 65,000 feet (20 km). The cabin was stabilized during descent by the large mass of electrical wires trailing behind it. At T+76.437 the nose caps and drogue parachutes of the SRBs separated, as designed, and the drogue of the right-hand SRB was seen by a tracking camera, bearing the frustum and its location aids.
The Thiokol engineers who had opposed the decision to launch were watching the events on television. They had believed that any O-ring failure would have occurred at liftoff, and thus were happy to see the shuttle successfully leave the launch pad. At about one minute after liftoff, a friend of Boisjoly said to him "Oh God. We made it. We made it!" Boisjoly recalled that when the shuttle was destroyed a few seconds later, "we all knew exactly what happened". Veteran astronaut Robert Crippen was preparing to command STS-62-A, scheduled for mid-year, when his crew stopped training to watch the launch. Pete Aldridge recalled, "I was waiting for the orbiter, as we all were, to come out of the smoke. But as soon as that explosion occurred, Crippen obviously knew what it was. His head dropped. I remember this so distinctly".
Space Shuttle Challenger disaster