Space Shuttle Columbia Disaster - Debris Strike During Launch

Debris Strike During Launch

Approximately 82 seconds after launch from Kennedy Space Center's LC-39-A, a suitcase-size piece of thermal insulation foam broke off from the External Tank (ET), striking Columbia's left wing reinforced carbon-carbon (RCC) panels. As demonstrated by ground experiments conducted by the Columbia Accident Investigation Board, this likely created a 6-to-10-inch (15 to 25 cm) diameter hole, allowing hot gases to enter the wing when Columbia later reentered the atmosphere. At the time of the foam strike, the orbiter was at an altitude of about 66,000 feet (20 km; 13 mi), traveling at Mach 2.46 (1,870 miles per hour or 840 meters per second).

The Left Bipod Foam Ramp is an approximately three-foot (one-meter) aerodynamic component made entirely of foam. The foam, not normally considered to be a structural material, is required to bear some aerodynamic loads. Because of these special requirements, the casting-in-place and curing of the ramps may be performed only by a senior technician. The shuttle's main fuel tank is covered in foam as an insulator, to avoid ice forming on it when full of liquid hydrogen and oxygen, which itself could damage the shuttle when shed during lift-off. The bipod ramp (having left and right sides) was originally designed to reduce aerodynamic stresses around the bipod attachment points at the external tank, but it was proven unnecessary in the wake of the accident and was removed from the external tank design for tanks flown after STS-107 (another foam ramp along the liquid oxygen line was also later removed from the tank design to eliminate it as a foam debris source, after complex analysis and tests proved this change safe).

Bipod Ramp insulation had been observed falling off, in whole or in part, on four previous flights: STS-7 (1983), STS-32 (1990), STS-50 (1992) and most recently STS-112 (just two launches prior to STS-107). Ironically, STS-112 had been the first flight with the "ET Cam", a video feed mounted on the ET for the purpose of giving greater insight to the foam shedding problem. Post-107 analysis revealed that two previous shuttle launches (STS-52 and -62) also had bipod ramp foam loss that went undetected. In addition, Protuberance Air Load (PAL) ramp foam had also shed pieces, and there were also spot losses from large-area foams. Previous strikes had caused no serious damage, and all affected shuttle missions completed successfully. NASA management came to refer to this phenomenon as "foam shedding." As with the O-ring erosion problems that ultimately doomed the Space Shuttle Challenger, NASA management became accustomed to these phenomena when no serious consequences resulted from these earlier episodes. This phenomenon was termed "normalization of deviance" by sociologist Diane Vaughan in her book on the Challenger launch decision process.

Video taken during lift-off of STS-107 was routinely reviewed two hours later and revealed nothing unusual. The following day, higher-resolution film that had been processed overnight revealed the foam debris striking the left wing, potentially damaging the thermal protection on the Space Shuttle. At the time, the exact location where the foam struck the wing could not be determined due to the low resolution of the tracking camera footage.