Space Shuttle Columbia disaster

On February 1, 2003, Space Shuttle Columbia disintegrated as it re-entered the atmosphere over Texas and Louisiana, killing all seven astronauts on board. It was the second of two Space Shuttle missions to end in disaster, after the loss of Challenger and crew in 1986.

The mission, designated STS-107, was the 28th flight for the orbiter and the 113th flight of the Space Shuttle fleet. It was dedicated to research in various fields, mainly on board the SpaceHab module inside the shuttle's payload bay.

During launch, a piece of the insulating foam broke off from the Space Shuttle external tank and struck the thermal protection system tiles on the orbiter's left wing. Similar foam shedding had occurred during previous Space Shuttle launches, causing damage that ranged from minor to near-catastrophic, but some engineers suspected that the damage to Columbia was more serious. When Columbia re-entered the atmosphere of Earth, the damage allowed hot atmospheric gases to penetrate the heat shield and destroy the internal wing structure, which caused the orbiter to become unstable and break apart.

After the disaster, Space Shuttle flight operations were suspended for more than two years, as they had been after the Challenger disaster. Construction of the International Space Station (ISS) was paused until flights resumed in July 2005 with STS-114. NASA made several technical and organizational changes to subsequent missions, including the addition of an on-orbit inspection to determine how well the orbiter's thermal protection system (TPS) had endured the ascent, and continual readiness of designated rescue missions in case irreparable damage was found. Except for one mission to repair the Hubble Space Telescope, subsequent Space Shuttle missions were flown only to the ISS to allow the crew to use it as a haven if damage to the orbiter prevented safe re-entry. The remaining three orbiters were retired after the building of the ISS was completed.

Flight risk management

After Columbia entered orbit, the NASA Intercenter Photo Working Group conducted a routine review of videos of the launch. The group's analysts did not notice the debris strike until the second day of the mission. None of the cameras that recorded the launch had a clear view of the debris striking the wing, leaving the group unable to determine the level of damage sustained by the orbiter. The group's chair contacted Wayne Hale, the Shuttle Program Manager for Launch Integration, to request on-orbit pictures of Columbia's wing to assess its damage. After receiving notification of the debris strike, engineers at NASA, United Space Alliance, and Boeing created the Debris Assessment Team and began working to determine the damage to the orbiter. Intercenter Photo Working Group believed that the orbiter's RCC tiles were possibly damaged; NASA program managers were less concerned over the danger caused by the debris strike.

Boeing analysts attempted to model the damage caused to the orbiter's TPS from the foam strike. The software models predicted damage that was deeper than the thickness of the TPS tiles, indicating that the orbiter's aluminum skin would be unprotected in that area. The Debris Assessment Team dismissed this conclusion as inaccurate, because of previous instances of predictions of damage greater than the actual damage. Further modeling specific to the RCC panels used software calibrated to predict damage caused by falling ice. The software predicted only one of 15 scenarios that ice would cause damage, leading the Debris Assessment Team to conclude there was minimal damage due to the lower density of foam to ice.

To assess the possible damage to Columbia's wing, members of the Debris Assessment Team made multiple requests to get imagery of the orbiter from the Department of Defense (DoD). Imagery requests were channeled through both the DoD Manned Space Flight Support Office and the Johnson Space Center Engineering Directorate. Hale coordinated the request through a DoD representative at KSC. The request was relayed to the US Strategic Command (USSTRATCOM), which began identifying imaging assets that could observe the orbiter. The imagery request was soon rescinded by NASA Mission Management Team Chair Linda Ham after she investigated the origin of it. She had consulted with Flight Director Phil Engelauf and members of the Mission Management Team, who stated that they did not have a requirement for imagery of Columbia. Ham did not consult with the Debris Assessment Team, and cancelled the imagery request on the basis that it had not been made through official channels. Maneuvering the orbiter to allow its left wing to be imaged would have interrupted ongoing science operations, and Ham dismissed the DoD imaging capabilities as insufficient to assess damage to the orbiter. Following the rejection of their imagery request, the Debris Assessment Team did not make further requests for the orbiter to be imaged.

Throughout the flight, members of the Mission Management Team were less concerned than the Debris Assessment Team about the potential risk of a debris strike. The loss of bipod foam on STS-107 was compared to previous foam strike events, none of which caused the loss of an orbiter or crew. Ham, scheduled to work as an integration manager for STS-114, was concerned with the potential delays from a foam loss event. Mission management also downplayed the risk of the debris strike in communications with the crew. On January 23, flight director Steve Stich sent an e-mail to Husband and McCool to tell them about the foam strike and inform them there was no cause for concern about damage to the TPS, as foam strikes had occurred on previous flights.

The crew were also sent a fifteen-second video of the debris strike in preparation for a press conference, but were reassured that there were no safety concerns.

On January 26, the Debris Assessment Team concluded that there were no safety concerns from the debris strike. The team's report was critical of the Mission Management Team for asserting that there were no safety concerns before the Debris Assessment Team's investigation had been completed. On January 29, William Readdy, the Associate Administrator for Space Flight, agreed to DoD imaging of the orbiter, but on the condition that it would not interfere with flight operations; ultimately, the orbiter was not imaged by the DoD during the flight. At a Mission Management Team meeting on January 31, the day before Columbia reentered the atmosphere, the Launch Integration Office voiced Ham's intention to review on-board footage to view the missing foam, but concerns of crew safety were not discussed.