> The Challenger failed because, while the O-Rings were within tolerances, they shouldn't have been varying at all. So because they were varying unexpectedly, t

> The Challenger failed because, while the O-Rings were within tolerances, they shouldn't have been varying at all. So because they were varying unexpectedly, they inevitably failed. That's not entirely correct. The idea that "the o-rings were within tolerance" isn't right. There is effectively no tolerance on the o-ring, either it's very, very nearly perfect or there's something wrong with your design, just like the bridge. The o-rings should be getting immeasurably small amounts of wear so the idea that they were "only" burning up 1/3 is a huge red flag. Any measurable wear on them is a problem, so 1/3 of them being gone means they were perhaps 30 or 300 times over tolerance.