Columbia - Debris Strikes the Orbiter

One of the most dangerous parts of a shuttle mission is when Houston gives the order to "go at throttle up." (5:03 into the clip.) It is the directive which tells the crew to increase their speed for the final push into space. Their escape velocity is nearly ten times the speed of sound.

About eighty two seconds into Columbia's last mission, after Commander Rick Husband executed "go at throttle up," a piece of insulation from the external fuel tank dislodged and fell away, striking the leading edge of the orbiter's left wing.

This video, at about 7:00 into the clip, reveals what NASA managers discovered the day after launch.