[..]  In spite of these variations from case to case, officials behaved as
    if they understood it, giving apparently logical arguments to each
    other often depending on the "success" of previous flights. For
    example. in determining if flight 51-L was safe to fly in the face of
    ring erosion in flight 51-C, it was noted that the erosion depth was
    only one-third of the radius. It had been noted in an experiment
    cutting the ring that cutting it as deep as one radius was necessary
    before the ring failed. Instead of being very concerned that
    variations of poorly understood conditions might reasonably create a
    deeper erosion this time, it was asserted, there was "a safety factor
    of three." This is a strange use of the engineer's term ,"safety
    factor." If a bridge is built to withstand a certain load without the
    beams permanently deforming, cracking, or breaking, it may be designed
    for the materials used to actually stand up under three times the
    load. This "safety factor" is to allow for uncertain excesses of load,
    or unknown extra loads, or weaknesses in the material that might have
    unexpected flaws, etc. If now the expected load comes on to the new
    bridge and a crack appears in a beam, this is a failure of the
    design. There was no safety factor at all; even though the bridge did
    not actually collapse because the crack went only one-third of the way
    through the beam. The O-rings of the Solid Rocket Boosters were not
    designed to erode. Erosion was a clue that something was wrong.
    Erosion was not something from which safety can be inferred.

It's even worse, you drive a truck over it, afterwards 1/3 of the steel is cracked, so you conclude that it must be able to safely accept 3x the weight. Nonesense! This is the sort of moronic engineering that killed the crew of the Challenger.

1. http://science.ksc.nasa.gov/shuttle/missions/51-l/docs/roger...

Note that it wasn't even engineering, reading the story in full (it's great, and covers the software side for which Feynman had nothing but praise) Feynman repeatedly noted that engineers were fairly realistic[0] and had been ringing alarms pretty much all along, this was entirely manglement mangling.

[0] unless the spectre of manglement was involved, at least for some of them

Something which, as summarized by Feynman's quote above, should be patently obvious to any engineer as bullshit.

Feynman's appendix is the only part that even tries, but it doesn't go far enough through no fault of Feynman's, he had no resources to pursue this line of inquiry. It was a struggle just to get that appendix into the report.

They should have interviewed every single person in any way remotely involved in that O-ring decision, find out if they objected to it, and if they didn't what money/institutional/social obstacles there were to prevent that.

Did some engineer actually sign off on the aforementioned "safety factor"? We don't know, but somehow I doubt that's language management came up with on their own, and if they did that there was no way for an engineer to spot that and report "wtf? The system doesn't work like that!".

Reading between the lines some engineer actually did come up with that estimate, but likely that engineer was where he was because NASA had a culture of promoting mindless yes-men.

I've read that too. You're dangerously close to getting me to re-read everything Feynman's written, again. I don't know whether to curse you or thank you :)

> And then what? [...]

I feel we're in violent agreement as to what the actual problem at NASA was, yes, I'm under no illusion that if some engineer had raised these issues it would have gone well for him. This is made clear in the opening words of Feynman's analysis,:

    [...] It appears that there are enormous differences of opinion as to the
    probability of a failure with loss of vehicle and of human life. The
    estimates range from roughly 1 in 100 to 1 in 100,000. The higher
    figures come from the working engineers, and the very low figures from
    management. What are the causes and consequences of this lack of
    agreement? Since 1 part in 100,000 would imply that one could put a
    Shuttle up each day for 300 years expecting to lose only one, we could
    properly ask "What is the cause of management's fantastic faith in the
    machinery?"

The real flaw in the report is that it didn't explore how that came to be institutional practice at NASA, Feynman is the only one who tried.

> That's really not what I read behind the lines.

Regardless of what sort of dysfunctional management practices there were at NASA they couldn't have launched the thing without their engineers. If they were truly of the opinion that shuttle reliability was 3 orders of magnitude less than what management thought, perhaps they should have refused to work on it until that death machine was grounded pending review.

Of course that wouldn't have been easy, but it's our responsibility as engineers to consider those sorts of options in the face of dysfunctional management, especially when lives are on the line.

The real issue was that that's not how NASA presented it outwardly. I doubt that teacher that blew up with Challenger was told about her odds of surviving in those terms.

As human launch vehicles go I think the shuttle's reliability was fine. The reason I called it a death machine is that if you make a vehicle that explodes 1% of the time you better advertise that pretty thoroughly before people step on board. NASA didn't.

Seems like it was politically impossible for NASA to say outright that there was a 1% chance of failure for every launch -- it would have led to loss of public support for the Shuttle program. So we have a systems failure where both politicians and the public contributed by making NASA admins feel compelled to lie and cover up to make the launches work.

I mean, the courageous thing to do would be to stand up and say space travel is inherently risky, people might die, but it's still worth it. But courageous politicians regularly get voted out of office, and I would bet a courageous NASA admin who said that would end up fired.

Additionally, when you have a civilian on board, I think it really changes how you think about what an appropriate level of risk is (13% might have been ok with professional astronauts who knew the risks beforehand, but likely was too high for a civilian).

And the line engineers at Morton Thiokol fought back pretty hard on the decision, even if it might have impacted their careers negatively.

I wonder if you told the management that, in those words, if they would have still believed such a ludicrous idea.