Bringing Columbia Home: The Untold Story of a Lost Space Shuttle and Her Crew

by Michael D. Leinbach

Investigators wanted incontrovertible proof that foam from the external tank was capable of inflicting mortal damage on the shuttle’s thermal protection system. That foam could damage the wing seemed counterintuitive on many levels. How could a piece of lightweight insulation—about the density of Styrofoam and weighing less than two pounds—fall off the tank and cause that kind of damage? And wasn’t it traveling at about the same speed as the shuttle? In fact, analysis showed a significant velocity difference between the shuttle and the foam at the time of impact. NASA estimated that the shuttle was traveling faster than 1,500 mph—and accelerating—when the foam fell off the tank. After falling off, the foam immediately and rapidly decelerated due to air resistance. The block slowed to about 1,000 mph in the 0.2 seconds between when it came off the tank and when the shuttle’s wing impacted the foam. The relative difference in speeds between the shuttle and foam was therefore more than 500 mph.5 The piece of foam that struck Columbia was four hundred times larger than the pieces tested previously by SwRI. Using a special compressed air cannon, SwRI planned to simulate the collision by firing foam blocks at more than 500 mph into samples of shuttle tiles and wing leading edge panels. High-speed cameras photographed the test firings and impacts, and over two hundred sensors measured the effects of the collisions. By the time the equipment and procedures were ready for the first...