A Third Hand Version Of The Challenger Disaster

The other day I met a guy who claims to have worked for the company who made the ill-fated O-rings that caused the first space shuttle disaster aboard the Challenger. He told me his version of the story which I then fact checked (well, ok, it was only Wikipedia).

First, his (abbreviated) version:

Steve the general contractor says the Shuttle disaster wasn't caused by faulty O-rings, but because they launched the shuttle when it was too cold. The O-rings were known not to be effective below 68 degrees. The contractor said "don't launch", Reagan said "Launch, I want a teacher in space for my state of the union speech". A too-cold rod that held the rocket in place snapped. The top of the rocket tilted out, the bottom tilted in and punctured the fuel tank. Boom. Disaster.

Steve says the shuttle launched that day with over 350 critical issues, any one of which would result in a complete loss of the vehicle. He says that today they only launch with 150 critical issues. Progress? He also said that NASA figured that they would lose 1 out of every 25 launches. In 27 years, they've only lost 2. Success?

Now the official version:

[Wikipedia] Disintegration of the entire vehicle began after an O-ring seal in its right solid rocket booster (SRB) failed at liftoff. The O-ring failure caused a breach in the SRB joint it sealed, allowing pressurized hot gas from within the solid rocket motor to reach the outside and impinge upon the adjacent SRB attachment hardware and external fuel tank. This led to the separation of the right-hand SRB's aft attachment and the structural failure of the external tank. Aerodynamic forces promptly broke up the orbiter.

The Rogers Commission found that NASA's organizational culture and decision-making processes had been a key contributing factor to the accident. NASA managers had known that contractor Morton Thiokol's design of the SRBs contained a potentially catastrophic flaw in the O-rings since 1977, but they failed to address it properly. They also disregarded warnings from engineers about the dangers of launching posed by the cold temperatures of that morning and had failed to adequately report these technical concerns to their superiors.

Thiokol engineers argued that if the O-rings were colder than 53 °F (12 °C), they did not have enough data to determine whether the joint would seal properly. This was an important consideration, since the SRB O-rings had been designated as a "Criticality 1" component—meaning that there was no backup if both the primary and secondary O-rings failed, and their failure would destroy the Orbiter and its crew.

One argument of NASA people in contest to Thiokol's concerns was that if the primary O-ring failed the secondary O-ring would still seal. This was unproven, and was in any case an illegitimate argument for a Criticality 1 component. (As astronaut Sally Ride cited in questioning NASA managers before Congress, it is forbidden to rely on a backup for a Criticality 1 component. The backup is there to provide redundancy in case of unforeseen failure, not to replace the primary device, leaving no backup.) The engineers at Thiokol also argued that the low overnight temperatures would almost certainly result in SRB temperatures below their redline of 40 °F (4 °C). However, they were overruled by Morton Thiokol management, who recommended that the launch proceed as scheduled.^[4] Despite public perceptions that NASA always maintained a "fail-safe" approach, Thiokol management was influenced by demands from NASA managers that they show it was not safe to launch rather than prove conditions were safe. It later emerged in the aftermath of the accident that NASA managers frequently evaded safety regulations to maintain the launch manifest (schedule).

So Steve's story was true in the main, if not the particulars. Interesting ...