For all the millions upon millions of systems necessary to make the shuttle go, one of the few wonderfully simple ones was the insulation that covered the external tank. The tank carried fuel, which was cryogenically cold, and something was needed to hold in the cold so that the liquid oxygen and hydrogen wouldn’t turn to vapor. So every tank was sprayed with a fluffy orange foam that was comparatively cheap, added little weight and did the job reliably. But sprayed foam soon becomes hard foam, and if a piece broke off during a shuttle’s high-speed ascent it could pack quite a wallop. Other shuttles had lost foam, but never as much as the suitcase-sized piece that fell away during Columbia’s launch, striking a wing and chipping away a piece of the carbon-carbon armor that protected it from the heat of reentry. The damaged area did no harm during the 15 days the spacecraft remained in orbit, but during descent through the atmosphere, it allowed superheated plasma to stream into the wing and then the belly of the ship, causing Columbia to disintegrate in a trail of debris across three states. Seven more people were lost to a bad idea and a dangerous ship.