Investigation of the Challenger Accident

Background

What it found

1. Like the Rogers Commission, the Committee concluded that the accident was caused by the failure of the aft field joint on the right-hand solid rocket motor, a faulty design that neither NASA nor its contractor, Morton Thiokol, fully understood. p. 4 p. 7

2. Where the Commission pointed to a flawed decision-making process, the Committee concludes that the underlying problem was not poor communication but poor technical decision-making, over several years, by top NASA and Thiokol managers. Information on the joint's flaws had been presented to every level of Shuttle management. p. 4 p. 5 p. 172

   “Information on the flaws in the joint design and on the problems encountered in missions prior to 51-L was widely available and had been presented to all levels of Shuttle management. Despite the presence of significant amounts of information and the occurrence of at least one detailed briefing at Headquarters on the difficulties with the 0rings, the NASA and Thiokol technical managers failed to understand or fully accept the seriousness of the problem.”

3. Seals had been eroding on flight after flight. The report finds that NASA came to treat this damage as "acceptable" and "within experience base", and chose to keep flying while a measured, 27-month fix proceeded. p. 62 p. 5 p. 146

   “The Committee concurs with Dr. Feynman's analysis that NASA had no understanding of the O-ring erosion phenomenon, and their rationale for accepting it was not based on sound engineering principles.”

4. On the eve of the launch, Thiokol engineers warned that the cold would impair the seals. The report finds that the response of Marshall managers led Thiokol's management to set aside their own engineers' judgement and recommend launch, and that the decision rested on faulty engineering analysis. p. 10 p. 219 p. 220

   “The decision to launch STS 51-L was based on a faulty engineering analysis of the SRM field joint seal behavior.”

5. The Committee found that NASA's drive for 24 flights a year created pressure that contributed directly to unsafe launch operations, and it acknowledges that the Committee itself, Congress and the Administration helped create that pressure. p. 2 p. 2 p. 123

   “The Committee found that NASA's drive to achieve a launch schedule of 24 flights per year created pressure throughout the agency that directly contributed to unsafe launch operations.”

6. The Committee confirms the Commission's finding that NASA's safety, reliability and quality assurance programmes were grossly inadequate, and finds nothing to show that NASA's safety staff ever evaluated the seal problem. p. 4 p. 218

7. It goes beyond the Commission on other hardware, raising concerns about the margins of the Shuttle's main engines and recommending a new specification for its landing gear, tyres and brakes. It also finds that NASA's management waived its own launch commit criteria on the morning of the launch without a valid technical reason. p. 5 p. 5 p. 11

Where to start reading

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

1. Conclusions p. 4 · Read →

   The Committee's verdict in a few pages, including where and why it parts company with the Rogers Commission, followed by a digest of every finding.

   “NASA management and the Congress must remember the lessons learned from the Challenger accident and never again set unreasonable goals which stress the system beyond its safe functioning.”

2. History p. 51 · Read →

   The joint problem from the 1973 contract to the night before launch, set out as a chronology of what NASA and Thiokol knew and when.

   “At seven different times in the Shuttle Program, NASA and Thiokol managers made poor technical decisions that ultimately permitted continued flight of an unsafe Solid Rocket Motor design.”

3. Summary of Casing Joint Design p. 61 · Read →

   How the booster joint worked, why it failed, and how erosion of its seals came to be treated as acceptable.

   “But rather than identify this condition as a joint that didn't seal, that is, a joint that had already failed, NASA elected to regard a certain degree of erosion or blow-by as "acceptable."”

4. Pressures on Shuttle Operations p. 115 · Read →

   Where the pressure to fly more often came from, and what it did to training, planning and safety.

   “Without operating pressures the program might have been stopped months before the accident to redesign or at least understand the SRB joint. Without operating pressure the flight could have been stopped the night of January 27.”

5. Technical Management p. 139 · Read →

   Why senior managers did not act on the seal problem, including a NASA manager's own account of how they talked themselves into it.

   “When we recognized that it had design deficiency, we did not fix it. Then we continued to fly with it, and rationalized why it was safe, and eventually concluded and convinced ourselves that it was an acceptable risk.”

6. The STS 51-L Launch Decision p. 208 · Read →

   The flight readiness reviews, the teleconference of 27 January, and the ice on the launch pad the next morning.

   “Clearly evident is the fact that the Flight Readiness Review procedure cannot compensate for poor engineering analysis.”