Space Shuttle Columbia, 2003: A Foam Strike and Organizational Causes

What happened

Space Shuttle Columbia (mission STS-107) launched on January 16, 2003 for a 17-day science mission. On February 1, 2003, during re-entry, the orbiter broke up and its seven crew members were lost, about 15 minutes before the scheduled landing at Kennedy Space Center.

What the Board found

• Physical cause: a breach in the thermal protection system on the leading edge of the left wing. A piece of insulating foam separated from the left bipod ramp of the External Tank 81.7 seconds after launch and struck the wing near the lower half of Reinforced Carbon-Carbon panel number 8. During re-entry the breach let superheated air in, which progressively melted the aluminum structure of the wing until aerodynamic forces caused loss of control and breakup.
• Organizational causes: the Board concluded they were rooted in the Space Shuttle Program's history and culture, including the original compromises needed to gain approval for the Shuttle, years of resource constraints, fluctuating priorities, schedule pressures, and describing the Shuttle as operational rather than developmental.
• Practices detrimental to safety were allowed to develop. The Board lists among them reliance on past success as a substitute for sound engineering practice, such as testing to understand why systems were not performing as required, and organizational barriers that prevented effective communication of critical safety information.
• The Board said it placed as much weight on these organizational factors as on the more easily understood and corrected physical cause.

Apply the lesson

• Look for a recurring anomaly in your own work that everyone has learned to accept because "it has always come back fine". What test would show why it happens?
• List the paths by which a safety concern from an engineer reaches the person who can stop the work. Where could it be filtered or lost?
• Ask who has independent authority over technical requirements and waivers, and whether that person reports through the schedule or the safety line.

Engineering lesson: past success is not a test result. An unexplained deviation that has not caused harm yet is a warning to understand, not a margin to spend.

What the Board recommended

The Board issued two preliminary recommendations on April 17, 2003, before its final report. The first was a comprehensive inspection plan to determine the structural integrity of all Reinforced Carbon-Carbon system components, using advanced non-destructive inspection technology. The second was to make on-orbit imaging a standard requirement for each Shuttle flight.

Its final report includes recommendations that address both the physical and the organizational causes. Three examples, in the Board's words in summary:

• R3.2-1: Initiate an aggressive program to eliminate all External Tank Thermal Protection System debris-shedding at the source, with particular emphasis on the region where the bipod struts attach to the External Tank.
• R6.2-1: Adopt and maintain a Shuttle flight schedule that is consistent with available resources. Schedule deadlines are an important management tool, but they must be regularly evaluated so that any added risk is recognized, understood and acceptable.
• R7.5-1: Establish an independent Technical Engineering Authority responsible for technical requirements and all waivers to them, and make it the sole waiver-granting authority for technical standards.

Sources

• Columbia Accident Investigation Board, Report Volume I, August 2003 (NASA)
• NASA: STS-107 Columbia accident and investigation page