Comment by mikeash | Hacker News Reader

Comment by mikeash | Hacker News Reader

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What were the other warning signs which seemed as severe as the O-ring problem without the benefit of hindsight?

Your quote claims that it would have been much more expensive to address all of these things, but what's the support for that statement?

My (extremely limited, to be sure) understanding is that there wasn't anything else that severe. The O-ring problem was dire, and the only reason it didn't get attention was because schedule pressure and go-fever caused management to minimize the problem.

Note that the warning signs mentioned in the quote were not just theoretical test results, but also several cases where fire was getting where it was not supposed to be during actual flights. Further, there was strong evidence that these incidents were linked to cold weather. "Don't fly when it's really cold" wouldn't have been a particularly expensive mitigation, either, even if you argue that suspending flights until the problem was investigated and fixed was not reasonable. I mean, you're launching from Florida, a restriction not to launch in temperatures under 50F wouldn't have been a terrible burden.

How many other warning sings were as severe as the O-rings and as easy to mitigate? My money is on "zero" in which case this argument is just so much noise.

> My (extremely limited, to be sure) understanding is that there wasn't anything else that severe.

That's my understanding as well. Boisjoly wrote a detailed essay describing the thought process that they went through to arrive at their conclusion that the O-rings were a critical problem (the other three authors are a professor and two students at RIT):

https://people.rit.edu/wlrgsh/FINRobison.pdf

The essay is a response to a criticism by Edward Tufte that the engineers did not present the issue properly during the telcon the night before the launch, and that this was the reason that NASA did not agree to scrub the launch. It makes clear that, at least in the minds of the engineers, there was no other issue even close to being this critical. Granted, they were concerned with only one subsystem, the SRBs--but the fact that this issue also dominated the telcon the night before the launch indicates that there was no other issue even close to being that critical in any other subsystem either.

[Edit: It's interesting, btw, that in the essay linked to above, Boisjoly accuses Tufte of precisely the thing Yudkowsky is talking about in his article: hindsight bias. He argues that Tufte did not recognize or allow for the fact that the engineers at the time had limited information, but talks as though they knew everything that was known in hindsight.]

This is a good read. I do think the Tufte essay is excellent except for one detail. I don't think it's fair that he places blame on the the engineers for failing to convince NASA management to stop the launch. It is possible that better designed slides would have helped NASA management grasp the problem. But I think the fault is more so on them.

The premise of "failing to convince management" relies on the notion that "management can do no wrong". For example, if you tell your boss that we're about to drive the bus off a cliff, and he doesn't listen, it's your fault.

This is the way things work in many organizations, it's an old-school approach to management, but to me it is purely dysfunctional. When someone tells me I'm about to drive off a cliff, I say, "Wow, thanks! What did I fail to see that got us into this mess in the first place?"

Aside from Tufte's notion of blame, I think his essay is very instructive.

> It is possible that better designed slides would have helped NASA management grasp the problem. But I think the fault is more so on them.

I completely agree, and AFAIK the Tufte essay does not even mention a critical point in this regard, which the Boisjoly paper does. The engineers had already tried to get all flights stopped until the O ring issue could be investigated and properly understood, in the August before the Challenger flight. NASA had refused. So the NASA managers were already aware that there was a critical flight risk, and they had already chosen to ignore it. That means it definitely wasn't a case of bringing new information to management's attention in order to drive a decision. It was a case of trying to get them to change, at least in part, a decision they had already made.

The argument about cold temperatures has to be viewed in that light--it was an attempt to find something, in the absence of good, hard data and a solid understanding of what was going on, that would at least get NASA to delay some flights, since they had already refused to delay all flights. In fact, considered solely on engineering grounds, the argument about cold temperatures was fairly weak (as Boisjoly points out in his essay). But it was weak not because cold temperature flights were almost as safe as warm temperature flights; it was weak because warm temperature flights were almost as unsafe as cold temperature flights! (A previous flight with significant blow-by had been made at a temperature of 75 F, and test stand data showed that the O-rings were not sealing completely at any temperature below 100 F.) But the engineers couldn't say that the night before the Challenger flew, because they had already said it back in August and had been ignored.

> I do think the Tufte essay is excellent except for one detail.

I don't think that one detail is the only serious flaw in the essay. As far as I can tell, Boisjoly's criticisms--that Tufte misunderstood the actual issue (it was blow-by, not erosion), and that he misunderstood what information the engineers did and did not have (for example, they didn't have reliable temperature data for many flights)--are valid.

> "Don't fly when it's really cold" wouldn't have been a particularly expensive mitigation, either

The SRBs were not designed to work below 40F, so it would have been very reasonable to postpone launch (yet again). However, Reagan was going to give his State of the Union speech on that same evening, and putting a teacher in space was supposed to be a highlight of the speech...

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