[Positive]

But the Challenger did explode.

An "O ring" on one of the external boosters gave out and a "torch like" side ways flame caused the main rocket to explode.

[Alberta's Child]

The Challenger event was not so much an "explosion" as it was a large-scale ignition -- it was comparable to the difference between a car that "explodes" with a full gas tank and one that explodes with a nearly-empty one. The shuttle itself appeared to break up primarily as a result of the friction forces that resulted when it was no longer flying forward.