What is the foam insulation and why does it fall off?
Foam insulation is sprayed onto the the external fuel tanks in a gooey form and then becomes hard as a brick but light, like Styrofoam. It keeps the liquid hydrogen and the liquid oxygen fuel super cold. Shuttles ride these 15-story tanks during liftoff, then the tanks separate. NASA video showed that 81 seconds into the flight, a 20-inch, 2 1/2-pound piece of the foam fell off and struck Columbia’s left wing. The shuttle Columbia was moving more than at twice the speed of sound. The impact is thought to have involved a relative speed of no more than 500 mph. The foam is fragile enough to have been damaged once in a hailstorm, forcing a previous shuttle mission to be delayed while the insulation was repaired. Chunks have come off in flight before, too. They can be ice-coated, making them heavy projectiles. Columbia sustained damage in this way in 1992 and 1997, and foam struck a booster rocket of Atlantis in October. “The thing of this is, almost since Day One, the insulation has been
