Comment by oritron

It's the same explaination. When the SRB joints flexxed the o-rings were meant to stay in place, but the joints were defective and NASA knew the o-rings were moving. However NASA also believed the o-rings could still take the abuse, because although they were moving they were getting shoved deeper into the joint, in a way that wasn't intended but was nonetheless at least marginally effective at stopping exhaust blow-by shortly after it began. But when the o-rings were cold and stiff... they didn't move the same way, exhaust blew by them longer and cut right through. At that point the SRB turns into a cutting torch (the SRBs didn't actually explode until after the shuttle broke up and range safety sent the signal to kill the boosters.

>>I find that highly surprising, because "it was the O-rings" explanation seems universally believed and sanctified by no lesser authority than the Nobel prize laureate Richard Feynman.

Essentially you are mischaracterizing what Feynman did or say, although this is also Feynman fault :-), by doing the famous public demonstration, with the ice water in a glass [2], although even there he only said it has "significance to the problem...". In other words, we should not simplify, even for the general public, what are complex subtle engineering issues. This is also the reason why current AI, will fail spectacularly, but I digress...

Feynman documented the joint rotation problem in his written Appendix F, but his televised demonstration became the explanation...[3]

Camarda is correct here. There was a fundamentally flawed field joint design, meaning the tang-and-clevis joint opened under combustion pressure instead of closing. This meant the O-rings were being asked to chase a widening gap something the O-ring manufacturer explicitly told Thiokol O-rings were never designed to do. Joint rotation was known as early as 1977, a full nine years before the disaster.

The cold temperature made things worse by stiffening the rubber so it could not chase the gap as quickly, but O-ring erosion and blow-by were occurring on flights in warm weather too and nearly every flight in 1985 showed damage.

The proof is how they fixed. NASA redesigned the joint metal structure with a capture feature to prevent rotation, added a third O-ring for redundancy, and installed heaters but kept the exact same Viton rubber. If the O-rings were the real problem, you would change the O-rings. They did not need to.

The report [1] is public for everybody to read...but not from the NASA page... who funnily enough has a block on the link from their own page, so I had to find an alternative link...

[1] - https://www.govinfo.gov/content/pkg/GPO-CRPT-99hrpt1016/pdf/...

[2] - https://youtu.be/6TInWPDJhjU

[3] - https://calteches.library.caltech.edu/3570/1/Feynman.pdf

Without being too familiar with the subject - another commenter referred to the "swiss cheese model": the O-ring design, the temperature etc. weren't the single cause, they were contributing factors, and the more contributing factors you eliminate, the more certain you can be that you won't have a repeat accident. AFAIK there weren't any more Shuttle launches at such low temperatures after that anymore either?

My recollection is that a rocket design was scaled up from one that worked, by people who didn't consider how an o-ring should be loaded in order to function properly. They inadvertently changed the design rather than simply scale it. I don't think Feynman got this wrong either. His demo was because the justifications for flight were based on the fact that failure had a temperature correlation, and they had a model representing how damaged the o-rings would be.

The o-ring failure was a measurable consequence of the joint design failure. The data behind the model didn't go down to temperatures as low as that at Challenger's launch date.

For more inappropriate extrapolation to justify a decision: the data for the heat shield tile loss model was based on much less damage than sustained by Columbia (3 orders of magnitude IIRC).

Now they are looking at the same style of fallacy and don't even have a model based on damage sustained in flights.

Another parallel I haven't seen discussed here yet, though I haven't read all comments: I recall Feynman feeling like he was on the investigation panel as a prop, that the intention of the investigation was to clear NASA of any wrongdoing. They used a model, considered risks, etc. Feynman recognized the need for a clear and powerful visual to cut through an information dump and pull it to front page news. The invitation of Camarda to a presentation with a pre-determined conclusion has the same feeling. I don't know what Camarda can do to put it on a (non-HN) front page today.

> "it was the O-rings" explanation seems universally believed and sanctified by no lesser authority than the Nobel prize laureate Richard Feynman.

If you read Feynman's account in the book What Do You Care What Other People Think?, you'll see that he realized afterwards that he was prompted to make the demonstration he made at a NASA press conference--putting a piece of O-ring material in a glass of ice water, clamped with a C-clamp, and then taking it out and releasing the clamp to show that the material did not spring back--to get public attention focused on problems with the joint in a way that could not be ignored. But, as has been pointed out downthread, when the joint was redesigned, the new design did not change the O-rings at all. So the specific issue that was shown in Feynman's demonstration was not the issue that actually needed to be fixed. It was just a convenient way to show the public that there were problems with the joint, with a simple demonstration that everyone could understand. Trying to show the actual problem--that the entire joint design was fundamentally flawed and needed to be changed--would not have worked in a context like that.

Using the same o-rings afterwards is surprising, I've heard that the manufacturer was surprised that they were being used for that purpose because they weren't rated for that.

Also I'm not sure the assertion is correct. If the sealant and O-Rings were adequate, the joint would not have failed. It was suboptimal, and increased risk, sure, but it in itself wasn't the reason for the accident. It was the joint and the o-rings in combination. The holes in the swiss cheese model lined up that day, and a lot of small problems combined into one big problem

Both things can be true. A better O-ring with the same joint might have prevented the disaster. A better designed joint with the same O-ring might also. Feynman knew that a little theater would go a long way. The O-ring explanation, albeit a partial explanation, made for good theater.

There’s a pretty good explanation here: https://exrocketman.blogspot.com/2021/12/the-seal-failure-in...

The bigger an organization gets, the more internal overhead it has. At some point, it would take divine intervention for important things not to get overlooked or lost at some junctions in the org chart.

I've often thought world leaders, upon election/selection, should get a free few orbits of the earth, to give them some perspective on the job they're about to undertake. Maybe offer the first one on Artemis II, a deferred one for the current US administration?

Based on some rough numbers, NASA's budget (around $24B) would be <4% of the US's total spending on entertainment, with a pretty great return in research, engineering and education to boot.

I also looked up the NSF's 2024 budget, which, at $9B, was much lower than I expected.

Hard disagree. some of our best technologies came about to solve problems related to space travel which we later found useful for mundane problems at home. gps, digital cameras immediately come to mind. The only other phenomena I can think of with similar effects on human progress is war... I'll take a space race thanks

could the government rent out monopoly grants for televised football on the moon in exchange for sponsoring manned space exploration?

No no no. Space will be colonized. At least our local solar system will see sustained human exploration and inhabitation. This requires physical presence. This is one of those black swans which seem silly when looking forward, but obvious in retrospective. The future belongs to those who do seemingly silly things today. The first industrialists often faced ridicule because they spent time designing machines instead of doing the task and making the immediate money. Set aside your need for immediate gratification. Hard things lead to good outcomes.

I'd prefer if we just wrote off space-x and pretend they don't exist.

This is when you hire someone with autism and give them a direct report.

Their inability at social cues will cut right through.

Works every time.

The shuttle people never looked.

That there was blowby where there should be none was known, but nobody dug into why. There was no determination that it wasn't enough to be a problem, just an observation that it hadn't blown the booster up yet. For something with a wide spread in the data points, no way to model the maximum expected values.

Once they got serious about looking it didn't take much to reproduce the problem. They built a single joint, mostly filler inside, fuel to model the real thing during ignition. Maybe worked, maybe spot-welded, maybe complete failure. The colder the more likely to fail.

I think it's still very important for adaptability. yes, a land rover can run for years and run thousands of experiments, but it's limited to whatever scientific probes it was equipped with. Humans are right now more flexible and could adapt experiments to findings, which would then inform the next rovers. And when the time comes that we start mining and building on the moon, a few humans will probably need to live there. So any data on human survival outside the Earth is useful data. https://humanresearchroadmap.nasa.gov/