The loss of Columbia was caused by a piece of ET foam that impacted and resulted in a breach of the left wing
This Space Shuttle External Tank foam bullet (and sabot carrier) is an example of the small-scale ballistic testing material that researchers at NASA Glenn Research Center used to demonstrate that a foam strike could indeed break the reinforced carbon-carbon that protects the leading edge of the orbiter's wings. Glenn's Ballistics Impact Lab built a unique gas gun that enabled impact tests at low-pressure, low temperature conditions similar to those present during the Columbia foam strike. The lab was later modified to run tests that supported full-scale testing of a real RCC panel.
