In this photo of the STS-107 launch, you can see the piece of insulation foam which would break off the external tank and damage the space shuttle shortly after launch.
About the size of a suitcase, the foam struck the orbiter’s left wing, leaving a small hole in the wing’s heat-resistant-but-brittle reinforced carbon-carbon edge. It was this hole, less than a foot wide, that allowed hot gases to get inside the heat shield and orbiter structure during recently, leading to the break up of the spacecraft.
In their book Bringing Columbia Home, Michael Leinbach (former NASA launch director) and Jonathan Ward write about the incident and subsequent internal discussion at NASA over the severity of the issue. Complacency, pressure to keep on schedule, and poor management led NASA officials to dismiss the foam strike as a “nonissue.”
