We are all familiar with the so-called world-defining event; some joyous or, more often than not, catastrophic event that marks time in such a way that people know and remember exactly where they were or what they were doing when they first heard the news.
Such is the case with the Space Shuttle Challenger explosion, this month marking 40 years since the January 28, 1986 tragedy.
On that cold January morning, I was in my high school biology class. To be perfectly honest, I don’t recall if the class was watching the launch live or not; such is my memory of an event 40 years on. But it would have made sense, seeing as how a big deal was made of the fact that this mission was set to launch with the first teacher, Christa McAuliffe, going into space.
The facts from that day are well known, including what subsequent investigations revealed about the causes of the explosion. The bulk of the work came from the Rogers Commission, which held congressional hearings to determine what went wrong.
The Space Shuttle Challenger is carried by a Crawler-transporter on the way to its launch pad, December 1985. (Source, NASA)
As the Rogers Commission Report concluded, the primary cause of the accident centered on the O-rings that were a key part of the solid rocket boosters (SRB) that served to propel the Challenger into orbit. The O-rings’ function was to seal the field joints between sections of the SRBs in order to contain the hot gases produced by the burning of the solid propellant. However, the faulty design of the field joints and O-rings that was known by both the manufacturer of the SRBs, Morton Thiokol, as well as NASA, was accepted as normal without an effort to correct the issue, which also meant not fully dealing with how it would affect flight safety.
The O-rings were the main technical issue, but the culture at NASA and Morton Thiokol was in equal measure responsible for the accident. A practice known as ‘normalizing deviance’ played a role here. Normalizing deviance is the process of accepting a design or performance anomaly instead of finding the root cause of an issue and correcting it. In the case of the O-rings, both Morton Thiokol and NASA engineers knew of the problems with the O-rings not sealing properly as far back as 1977 when ignition tests were done on the SRBs. While some modifications were made, they did not address the root cause of the issue. Instead, repairs were made after each flight and the condition known as “blow by,” where hot exhaust gases would leak from the SRB joints, was noted and monitored.
The other fact that sealed the fate of the Challenger that morning was the launch recommendation decision by Morton Thiokol. In a teleconference call the night before the launch, engineers from NASA and Morton Thiokol discussed the issue of temperature at launch time, which was forecast to be well below freezing. As it was known that temperature adversely affected the O-rings ability to seal properly, the engineers at Morton Thiokol recommended the launch be postponed. This upset the NASA engineers as the mission had already been delayed and they were weary of even more delays.
So, during a 30-minute break, the management at Morton Thiokol pressed the engineers on their recommendation. At one fateful point, Jerald Mason, a senior VP, told Robert Lund, the VP of engineering, to “take off your engineering hat and put on your management hat,” when in that moment it was precisely the engineering hat that was needed, not the other way around.
As the cliché goes, hindsight is always 20/20. But still, in that moment, there was general agreement among the technical staff and engineers of what the right thing to do was; namely, postpone the launch because of the uncertainty over the critically low temperatures at launch time forecast for the morning, and the implications for the safety of the mission.
Nevertheless, the absence of any actual data for how the O-rings would perform at temperatures well outside any previous window of experience was central in forming a wedge that Thiokol management used to persuade engineers that since there wasn’t uniformity on their decision then it wasn’t a matter of technical reasons but a much more subjective judgement call.
And yet, 17 years later almost to the day, the world witnessed the failure of yet another Space Shuttle, the Columbia, as it burned up on reentry into the earth’s atmosphere, killing all of the astronauts on board and reviving old wounds of the Challenger disaster. Perhaps showing that not all of the relevant human and cultural issues had been corrected.
Miles Budimir
Senior Editor
Filed Under: Commentaries • insights • Technical thinking, NEWS • PROFILES • EDITORIALS
