> 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 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.