The
NASA report above glosses over one tiny detail however. The explosion at 73 seconds probably did not kill the crew directly. After the remains of the orbiter were recovered from the ocean it was discovered some of the cabin air cylinders were activated; and the only explanation that anyone has come up with for this discovery is that the cylinders were triggered after the explosion, manually.
The implication is that the cabin was depressurising after the explosion, and that one or more of the astronauts were conscious. However at the altitude the accident occurred, air from a cylinder at the ambient pressure is not sufficient to preserve consciousness for long, pure oxygen might have done so, but these cylinders contained pressurised air. It is perhaps a blessing that they had only compressed air in fact since at that point there was nothing anyone could do; the Orbiter had lost a wing during the explosion and was tracked until impact with the sea at about 200 mph; which would have certainly killed any surviving astronauts.
Still, if that isn't depressing enough, it isn't known how big the leak would have been in Challenger, as the debris disintegrated upon impact, but if the leak was small enough, they could have been alive and conscious right to the end. No records exist of the final moments, as the power for the recording devices onboard were lost during the explosion, and no one knows if they were conscious, but it is thought to be unlikely.