Risk Analysis of the Space Shuttle: Pre-Challenger Prediction of Failure

Abstract

The Rogers Commission report on the space shuttle Challenger accident concluded that the accident was caused by a combustion gas leak through a joint in one of the booster rockets, which was sealed by a device called an O-ring. The commission further concluded that O-rings do not seal properly at low temperatures. In this article, data from the 23 preaccident launches of the space shuttle is used to predict O-ring performance under the Challenger launch conditions and relate it to the catastrophic failure of the shuttle. Analyses via binomial and binary logistic regression show that there is strong statistical evidence of a temperature effect on incidents of O-ring thermal distress. In addition, a probabilistic risk assessment at 31°F, the temperature at which Challenger was launched, yields at least a 13% probability of catastrophic field-joint O-ring failure. Postponement to 60°F would have reduced the probability to at least 2%. To assess uncertainty in estimates and for any future prediction under the Challenger scenario, a postanalysis prior distribution of the probability of a catastrophic failure is derived. The mean and median for this distribution for 31°F are at least .16 and .13, and for 60°F they are at least .004 and .02, respectively. The analysis of this article demonstrates that statistical science can play an important role in the space-shuttle risk-management process.

Key Words:

• Catastrophic failure
• Data analysis
• O-rings
• Probability risk assessment
• Statistical science