Riding Rockets - Mike Mullane [133]
The story was no different for the engineers at the SRB Thiokol factory in Utah. The pressure to keep flying was hammering them even while they were struggling with a major anomaly. The O-ring problem first seen on STS-2 had not gone away. In fact, it had gotten worse. Beginning with STS-41B, launched in February 1984, and up toChallenger, only three missions did not have O-ring problems. The other fifteen flights of this period returned SRBs with eroded O-rings. Astonishingly, in nine of these fifteen flights, the engineers had recorded “blow-by,” in which heat had not only eroded the primary O-rings but, for very brief moments, had gotten past those rings. On STS-51C, the blow-by had been exceptionally significant. That mission had launched in January 1985, after the stack had waited on the pad through a bitterly cold night. Engineers suspected that cold had reduced the flexibility of the rubberized O-rings, which, in turn, had allowed a more significant primary O-ring leak, resulting in a more significant blow-by. But in all cases none of the observed erosion equaled what had been recorded on STS-2’s damaged O-ring, and that mission had been fine. In effect the STS-2 experience had become the yardstick against which all following O-ring damage was being measured. If the damage was less (and it always was), then it was okay to continue flights. In what would later be defined as “normalization of deviance” inThe Challenger Launch Decision by Diane Vaughan, the NASA and contractor team responsible for the SRBs had gotten away with flying a flawed design for so long they had lost sight of its deadly significance. The O-ring deviance had been normalized into their judgment processes.
There were a handful of individuals who resisted this normalization of deviance phenomenon. Thiokol engineer Roger Boisjoly was one. In a July 31, 1985, memo to a company vice president, Boisjoly expressed his concern about continuing shuttle flights with the SRB O-ring anomaly. He concluded the memo with this prophetic sentence: “It is my honest and very real fear that if we do not take immediate action to dedicate a team to solve the problem with the field joint [a reference to the O-ring] having the number one priority, then we stand in jeopardy of losing a flight along with all the launch pad facilities.” Boisjoly feared a catastrophic failure at booster ignition that would not only destroy the shuttle and kill her crew, but would also destroy the launchpad.
Another engineer, Arnold Thompson, wrote to a Thiokol project