You do risk innovating when human lives are at stake, we wouldn't have a moon landing otherwise. And I never said engineers concerns were unfounded, quite the

You do risk innovating when human lives are at stake, we wouldn't have a moon landing otherwise. And I never said engineers concerns were unfounded, quite the opposite in fact, engineers know what can go wrong. If your engineers don't say "no", either they are incompetent or they are heartless. And because Allan McDonald was a great engineer and human being, he said "no". My point was more general than the Challenger disaster. When to listen to engineers and when to take unreasonable risks? Here, the answer is obvious, and we know that in general, Allan McDonald was someone to listen to but we have hindsight. How do we make the difference between chances you can't take and over-caution that can drag project forever? It would be interesting to know how risk was calculated in the space shuttle program since we have problems going both ways: two catastrophic accidents, and runaway costs which are, for a large parts, safety-related in response to these accidents.