People who don’t understand engineering or material science are often quick to discount how a “seemingly minor change” to a small component or material can have a bad outcome. Especially if they really want the change in question to happen. Both of the Space Shuttle disasters, the loss of Challenger and the loss of Columbia, can both be traced to such changes.
I was reminded of this when writing the post on The St. Francis Dam collapse. Small details that management was unwilling to admit could have big consequences.
The article at the following link is perhaps not the best article on the shuttle disasters, but it has information on both of the disasters you know about, and a “near miss” that you probably don’t remember. Shuttle Danger a Result of Environmental Concerns?
If you are of the right age, you remember the Challenger disaster of 1986, and how O-rings were blamed when one of the solid-rocket boosters caused the external fuel tank to explode.
It is widely known that the 1986 explosion of the Challenger shortly after lift off was the result of a faulty O-ring which allowed hot gases to escape from the solid rocket booster and pierce the skin of the external fuel tank. What is less well-known – according to the report cited above – is that the faulty O-ring was also a “replacement part”.
For the Challenger’s mission, NASA had been forced to stop using a putty used to insulate the O-rings from hot gases (which had worked during the first nine flights) because the manufacturer stopped using asbestos in the paste. The manufacturer had bowed to public pressure to stop using the flame-retarding material it had produced since the Second World War.
So we outlawed asbestos, and NASA couldn’t get something that had been critical to the first 9 flights of the Space Shuttle. So why wasn’t the flight scrubbed, until they were sure of the replacement material? In part, because it was a small change. (What could go wrong?) This was in spite of the fact that the US Military had experienced similar failures after they could no longer get the asbestos paste. Can you say, “Failure of management?” There was plenty of that.
The Space Shuttle Columbia disintegrated on reentry in 2003 because several of its heat-shielding tiles were damaged by foam falling off the external fuel tank at liftoff. Most people will know that, but what they might not know is that the formulation of that foam changed, because of pressure from the EPA to stop using Freon.
In 1997, NASA bowed to environmental pressure from the EPA to change the chemical makeup of the foam used to coat the tank to exclude freon, a gas some have suggested led to ozone damage which was a major environmental point of contention in the 90’s. The new foam did not stick to the tank and was quicker to fail under the extreme conditions of a rocket launch. In the first launch with the new foam formula, the shuttle orbiter sustained eleven times more damage from failing foam than in launches using the freon-laced coating.
Doubts were raised by workers at the space agency, almost immediately, but went unheeded. [my emphasis. Z-Deb]
There was an exemption made available for NASA to keep using Freon, but they stuck (no pun intended) with the new formula, even though it was not nearly as good. What could go wrong?
Well in 2003 we had the Columbia disaster. And the near miss? In 2007, Space Shuttle Endeavour suffered from foam falling on the heat shielding tiles. But that crew managed to survive.
Small changes can have devastating consequences, especially when engineering concerns are discounted because the bean counters think it is too expensive, or they think that the engineers are just being silly. “It’s a tiny change. What could go wrong?” But then what would the response have been in Congress, the media, wherever, if someone had suggested grounding the entire Space Shuttle fleet because Freon was absolutely required? Or asbestos paste was needed for O-rings? Can you imagine the outcry? “Those engineers want to destroy the environment,” would probably have only been the opening salvo in that war.
I am sure this is not the last time that a “minor change” will be highlighted by engineers, discounted by management, and will result in a bad outcome. It is the way of the world. Especially when what is being discussed is complicated technology.