The Space Shuttle Columbia disaster was a fatal incident in the United States space program that occurred on February 1, 2003, when the Space Shuttle Columbia disintegrated as it reentered the atmosphere, killing all seven crew members. The disaster was the second fatal accident in the Space Shuttle program, after the 1986 breakup of Challenger soon after liftoff.
During the launch of STS-107, Columbia's 28th mission, a piece of the spray-applied polyurethane foam insulation broke off from the Space Shuttle external tank and struck the reinforced carbon–carbon leading edge of the orbiter's left wing. Similar foam shedding had occurred during previous shuttle launches, causing damage that ranged from minor to nearly catastrophic, but some engineers suspected that the damage to Columbia was more serious. Before reentry, NASA managers had limited the investigation, reasoning that the crew could not have fixed the problem if it had been confirmed. When Columbia reentered the atmosphere of Earth, the damage allowed hot atmospheric gases to penetrate the heat shield and destroy the internal wing structure, which caused the spacecraft to become unstable and break apart.