Challenger Disaster

As Challenger ascended, it encountered tremendous wind shear 32 to 62 seconds after liftoff. (It was the worst wind shear any shuttle launch had ever faced.) Already weakened by the cold weather, the O-rings (which may have been resealing after liftoff) lost all chance to keep from completely eroding.

As the O-rings eroded, the aft field joint came completely out of alignment. A gap had opened through which blow-by gases could come into contact with Challenger's external tank. The potentially fatal failure cycle - known to responsible officials before liftoff - had commenced.

At 58.32 seconds, an unusual plume in the lower part of the right Solid Rocket Booster was recorded by cameras tracking Challenger's liftoff. At 58.772 seconds the first indication of smoke is visible from the right SRB. A fraction of a second later, at 58.778, the "first flickering flame appeared on the right SRB in the area of the aft field joint." By 59.262, the flickering flame had grown into "a continuous, well-defined plume."

At 64.660 seconds after liftoff,

...there was an abrupt change in the shape and color of the plume. This indicated that it was mixing with leaking hydrogen from the External Tank...Within 45 milliseconds of the breach of the External Tank, a bright sustained glow developed on the black-tiled underside of the Challenger between it and the External Tank.

Meanwhile, the crew was given the command to give the shuttle more power:

You are go at throttle up

The last response (this video includes historical footage, recreations and animations) ever publicly heard from Challenger, rebroadcast many times the night of the disaster, was:

Roger, go at throttle up

People watching the news that night took some small measure of comfort from those last words: "At least they never knew what happened."

Except - those were not the last recorded words of Challenger's crew.