Morton Thiokol engineer Roger Boisjoly warned repeatedly that the Space Shuttle’s solid rocket booster O-rings could fail in cold weather. After examining a January 1985 booster, he found that one O-ring had failed and the second had been damaged. In a July 1985 memo, Boisjoly described the joint-seal design as a potentially catastrophic safety problem: booster-joint flexing could delay the O-rings’ movement into a sealing position, allowing hot gas to escape. Cold temperatures made the rubber less flexible and increased the risk of blow-by. By late 1985, he told managers that an unfixed defect could destroy a shuttle mission.
For the STS-51-L launch scheduled for January 28, 1986, overnight temperatures were forecast to fall to about −1 °C (30 °F), and Morton Thiokol engineers recommended delaying the flight during a NASA go/no-go conference. NASA officials challenged the recommendation; managers then reconvened without Boisjoly and the engineering team and reversed the company’s position, telling NASA that the data was inconclusive. Challenger launched at 11:38 a.m. on January 28. At 58 seconds, a damaged O-ring seal failed in high-altitude winds; at about 73 seconds, escaping hot gas weakened the external tank and the vehicle disintegrated, killing all seven crew members. The presidential commission ordered by President Ronald Reagan examined the decision-making process, while Boisjoly testified that the reversal reflected customer intimidation and an unethical management forum. He was later ostracized and reassigned, but received the AAAS Award for Scientific Freedom and Responsibility in 1988; his records were donated to Chapman University in 2010.
