That Whole Rigamarole

Saturday, February 01, 2003

Thinking Back to Challenger

I thought today a little about the Challenger accident. There's a very good book by Edward R. Tufte that includes an interesting treatment of that accident. He points out that the Challenger accident has served as an example for a wide variety studies of engineering tools. I have seen that accident used to illustrate a set of techniques knows as TRIZ; Failure Mode and Effects Analysis; Fault Tree Analysis; and I'm sure that there are dozens or hundreds more.

Tufte writes about communicating through graphics. He points out in this book that the engineers at Morton Thiokol essentially understood the relationship of o-ring performance and cold weather. They had some data. What they couldn't seem to do is present those data in a way that clarified the risk of launching the Challenger on that January morning in 1986. Tufte shows how, with just a modicum of graphical savvy and the data they already had, they could have made the risk very clear indeed. It's one of the saddest things I've ever read.

With regard to today's loss of Columbia, the scenario involving damage from a piece falling off the system during launch is very suggestive. I heard this described briefly on television this morning, and the reporter mentioned that the engineers had examined the possibilities of damage and concluded that there was no cause for concern. I thought "How would they know what damage had been done?" I don't remember hearing about any EVAs on this mission, but I don't follow it closely. What occurred to me was the possibility that they had no choice even if the damage was thought to be potentially catastrophic. How would they get down? Go to the Space Station and wait for another Shuttle? How would that work?

I can easily envision a case in which engineers can't really provide solid information about whether the vehicle is safe to re-enter, and without a convincing disaster scenario, all the pressure is going to be for the vehicle to come back. I was reminded of Dilbert author Scott Adams observing about engineers that if they do a really great job, they get a certificate of appreciation in a handsome plastic frame. If they do a poor job, people get killed and the engineers get the blame. We may see that play out before long.


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