Columbia Accident Investigation Board Report, Volume I

Background

What it found

1. The Board finds that a piece of insulating foam from the External Tank struck the leading edge of Columbia's left wing during launch and breached it. On re-entry, superheated air entered the wing and melted its structure until the Orbiter broke apart. p. 9 p. 49

   “During re-entry this breach in the Thermal Protection System allowed superheated air to penetrate through the leading edge insulation and progressively melt the aluminum structure of the left wing, resulting in a weakening of the structure until increasing aerodynamic forces caused loss of control, failure of the wing, and breakup of the Orbiter. This breakup occurred in a flight regime in which, given the current design of the Orbiter, there was no possibility for the crew to survive.”

2. Foam had been coming off the tank since the first flight in 1981, against the design requirements. The report finds that NASA came to treat each strike as a maintenance problem rather than a danger, as it had treated O-ring erosion before Challenger. p. 122 p. 196 p. 196

   “Foam debris anomalies came to be categorized by the reassuring term ‘in-family,’ a formal classification indicating that new occurrences of an anomaly were within the engineering experience base. ‘In-family’ was a strange term indeed for a violation of system requirements.”

3. The Board found the Shuttle Program under pressure to meet a fixed date, 19 February 2004, for launching a key part of the International Space Station, a deadline on which the White House and Congress had in effect put NASA on probation. p. 131 p. 117 p. 132

4. During the flight, engineers asked three times for images of the damaged wing. Managers turned the requests down, having already judged foam no threat, and, the report finds, required the engineers to prove the Orbiter was unsafe. p. 140 p. 169 p. 170

   “Debris Assessment Team members had to prove unequivocally that a safety-of-flight issue existed before Shuttle Program management would move to obtain images of the left wing. The engineers found themselves in the unusual position of having to prove that the situation was unsafe – a reversal of the usual requirement to prove that a situation is safe.”

5. A study NASA carried out for the Board concluded that, had the damage been found early in the mission, a rescue by the Shuttle Atlantis would have been challenging but feasible. p. 173 p. 174

   “This rescue was considered challenging but feasible. To succeed, it required problem-free processing of Atlantis and a flawless launch countdown. If Program managers had understood the threat that the bipod foam strike posed and were able to unequivocally determine before Flight Day Seven that there was potentially catastrophic damage to the left wing, these repair and rescue plans would most likely have been developed, and a rescue would have been conceivable.”

6. The Board concludes that NASA's organisation and culture were as much a cause as the foam. Its safety organisation lacked independence and stayed silent, and the Shuttle Program held authority over schedule, cost and safety at once. p. 9 p. 177 p. 192

7. The report finds "echoes" of Challenger throughout, and concludes that the organisational causes identified after 1986 had not been fixed. It holds the White House and Congress, as well as NASA, responsible for the pressures that produced them. p. 195 p. 197 p. 203

8. Beyond immediate fixes to foam, imaging and wing repair, the Board recommends separating technical authority from schedule and cost, an independent safety organisation, and replacing the Shuttle as soon as possible. p. 9 p. 208 p. 210

Where to start reading

Short on time? These sections carry the report's argument. Each opens at the start of the section.

1. Executive summary p. 10 · Read →

   The physical cause and the organisational causes in two pages, and how the report is laid out.

2. A history of foam anomalies p. 122 · Read →

   How foam came off the tank on flight after flight, and how NASA came to live with it.

   “Photographic evidence of foam shedding exists for 65 of the 79 missions for which imagery is available.”

3. Schedule pressure p. 132 · Read →

   The February 2004 deadline for the Space Station, and what it did to the people preparing the Shuttle.

   “A screen saver (see Figure 6.2-3) was mailed to managers in NASAʼs human spaceflight program that depicted a clock counting down to February 19, 2004 – U.S. Core Complete.”

4. Decision-making during the flight p. 141 · Read →

   The Board's summary of the 16 days in orbit, when engineers sought images of the wing and managers declined them.

   “Managersʼ claims that they didnʼt hear the engineersʼ concerns were due in part to their not asking or listening.”

5. Possibility of rescue or repair p. 174 · Read →

   What could have been done had the damage been found, from a repair with scavenged metal and ice to a rescue by Atlantis.

6. The normalisation of deviance p. 197 · Read →

   The chapter's core comparison of foam and the Challenger O-rings, and how warning signs became routine.

   “Engineers and managers incorporated worsening anomalies into the engineering experience base, which functioned as an elastic waistband, expanding to hold larger deviations from the original design.”