Titanic tourist sub missing

Darat said:
It is astonishing the hull lasted for as many dives it did before it's final dive.
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What I've never been able to fathom is, what did they think the sudden loud gunshot-like cracking sounds during the previous dives were? Something harmless? Seals slipping? Materials flexing? Those aren't harmless! Delaminations are the obvious most likely cause, and no one could possibly think that was harmless in that context, right?
 
JayUtah said:
If your glue turns to dust, you're going to have a bad day. But trying to sensationalize the surface area of the glue layer doesn't really impress me. We've been laying up aerospace structures using epoxy for many decades without issue. The wing spars on a Boeing 777 routinely exceed 500 sq ft of glue area. The shocking fact is not that so much glue was used, but that the engineering process did not include any direct-examination exercise to determine the effectiveness of their layup plan. They simply inferred success from final strain testing.


It necessarily did. The point was to smooth out imperfections in the fiber layup so that new fiber layers would have a perfectly cylindrical base to adhere to. In theory the layers were glued together and the glue baked to join it all together in one integral hull. But the video shows that this process did not work, and the engineers relied on tests that did not have the capacity to reveal that.

The micrographs in the video did not explicitly connect the failure of the glue layer to adhere to the grind areas. The voids seem fairly evenly distributed.


I don't disagree. I build a lot of prototypes. But "Move fast and break things" is not about learning more from prototypes than from whiteboard analysis or simulation. It's about a culture that rewards being first to market and can tolerate a high failure rate. The Silicon Valley software model emphasized a minimum viable product (MVP). Whoever got that first enjoyed an essentially winner-take-all payout. And as you conclude, that's acceptable for low-stakes stuff like some software that can tolerate a high failure rate.


Yes, for engineering but not so much for software. Software cost is just guys sitting at chairs. This is not to make light of the effort and skill involved. It's simply to say that the cost of iteration is considerably lower than building physical prototypes of actual objects. Either way, however, you have to be prepared to sacrifice economy for speed. You're trying to get to market first, or be the first to roll out a viable disruption. There really are few prizes for second place.


Exactly. Good enough in consumer or commodity engineering is general a much lower bar than good enough in something that people are going to trust their lives to. Your tolerance for failure in that case has to be much, much higher. That's when the procedure has to be, "Go slow and check each step."


I would agree. My manufacturing process involve some pretty straightforward steps that we can prototype effectively using 3D printers before we get into injection molding, chem milling, and 5-axis machining. We don't need a lot of whiteboard time, and we do a lot of physical modeling to shake out bugs in the manufacture and assembly. This used to take a whole DFM/DFA cycle that was its own department.

But we also have some epoxy encapsulation processes that we invented. We're putting sensitive instruments into highly hostile environments rife with radiation, chemical contamination, high heat, and the absence of atmospheres. At least half of our engineering effort there is in figuring out ways to test the manufacture to ensure ourselves that our design assumptions are being met. These involve x-ray and ultrasound methods. But we also just sacrifice a few units to saw apart and verify the epoxy layup.
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Gracias por la elucidación adicional!

It occurs to me that one time you'd want to be first to market with a buggy MVP is when it's an entirely new market. Give people a capability they've never had before, and they'll be willing to accept a few risks and setbacks to get in on it.

But nobody's that desperate for manned space flight at the moment.
 
theprestige said:
But nobody's that desperate for manned space flight at the moment.
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An astute observation. During the space race, the Soviets were first to "market" with a lot of stuff, and it was objectively worse engineering but it got the job done. The Mercury capsule was technologically superior to the Vostok, but was a month late. The Gemini capsule was technologically superior to the Voskhod, but came later. The Apollo CSM was superior to the Soyuz at the time, and was available about the same time because NASA was fast catching up. But all those early Soviet successes were largely due to Krushchev insisting they move fast, break things, and be first to market.

Stockton Rush was trying to disrupt the market, which is similar to being first to market with a first-of-breed product. We've had steel-sphere submersibles forever, and even private dives to Titanic. He wanted to show that a composite submersible was not only technically possible but commercially competitive for this purpose. Compare this to James Cameron, who built and operated his own deep submersible. But he used proper engineering practice, tried methods, and endangered only himself.

Ethically the question is whether Ocean Gate properly disclosed the danger to its potential customers. Legally they were not passengers, but rather "trained mission specialists." [Kathryn Hahn wink picture here] When the ice cream machine at McDonald's goes down, it's disappointing but we move on. When you're participating in a dive where most failures are fatal, the engineer has an ethical duty not only to disclose the risk, but often to decide on behalf of lay persons that the danger is too great.
 
Myriad said:
What I've never been able to fathom is, what did they think the sudden loud gunshot-like cracking sounds during the previous dives were? Something harmless? Seals slipping? Materials flexing? Those aren't harmless! Delaminations are the obvious most likely cause, and no one could possibly think that was harmless in that context, right?
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He said they were the weak fibers snapping, leaving only the strong fibers. None of his passengers knew that it was simply cumulative damage, it wasn't going to stop once all the 'weak' fibers had broken.
 
Silly Green Monkey said:
He said they were the weak fibers snapping, leaving only the strong fibers. None of his passengers knew that it was simply cumulative damage, it wasn't going to stop once all the 'weak' fibers had broken.
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It doesn't take much to debunk that excuse. Even if they were weak fibres, the fact that they snapped means that they were under tension and thus bearing some of the load. The load that they were bearing then had to be redistributed to the strong fibres until eventually, even the strong fibres are too weak.
 
jeremyp said:
It doesn't take much to debunk that excuse. Even if they were weak fibres, the fact that they snapped means that they were under tension and thus bearing some of the load. The load that they were bearing then had to be redistributed to the strong fibres until eventually, even the strong fibres are too weak.
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The thing is he was bringing rich tourists down in the sub, not likely to be the kind of people with the knowledge base or experience for that kind of thinking.
 
jeremyp said:
It doesn't take much to debunk that excuse. Even if they were weak fibres, the fact that they snapped means that they were under tension and thus bearing some of the load. The load that they were bearing then had to be redistributed to the strong fibres until eventually, even the strong fibres are too weak.
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I wonder if the pops could have been internal shear.
 
Gulliver Foyle said:
The thing is he was bringing rich tourists down in the sub, not likely to be the kind of people with the knowledge base or experience for that kind of thinking.
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Well I thought of it and I'm not a materials scientist or an engineer. I don't think rich people are necessarily more stupid than I am, although, of course the ones that are less stupid than me probably wouldn't go near the sub.
 
jeremyp said:
I was wondering that too. I would have thought that most of the forces would be compression forces. However, I was replying to a specific claim that it was only the weak fibres that were snapping which implies tension.
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I know you were, and that's still possible. Given the shear analysis we saw presented above, it's possible the inboard elements of each layer and/or of the whole bonded structure were subject to tension beyond their yield strength. But your mention of audible pops got me thinking about all the different things that could produce it. So I'm not contradicting you in the least. I'm just adding another, "It could also be..." hypothesis. If we see shear failure at the layer boundaries (and we do), then noise from shear failure is not surprising.
 
JayUtah said:
An astute observation. During the space race, the Soviets were first to "market" with a lot of stuff, and it was objectively worse engineering but it got the job done. The Mercury capsule was technologically superior to the Vostok, but was a month late. The Gemini capsule was technologically superior to the Voskhod, but came later. The Apollo CSM was superior to the Soyuz at the time, and was available about the same time because NASA was fast catching up. But all those early Soviet successes were largely due to Krushchev insisting they move fast, break things, and be first to market.
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And why the soviet space program had so many more deaths. But think now you can be like a soviet cosmonaut just by flying in the US as the new moto of the FAA is move fast and break things coming from it being taken over by Space X.
 
jeremyp said:
Well I thought of it and I'm not a materials scientist or an engineer. I don't think rich people are necessarily more stupid than I am, although, of course the ones that are less stupid than me probably wouldn't go near the sub.
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You have the advantage of knowing the sub failed. They do not.
 
jeremyp said:
Well I thought of it and I'm not a materials scientist or an engineer. I don't think rich people are necessarily more stupid than I am, although, of course the ones that are less stupid than me probably wouldn't go near the sub.
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It's not so much that they are stupid (though they often are, inherited wealth is a great disguise), it's that because they often have others do their thinking for them (even in the case of "self made" ones), they've lost the ability to think critically, or never developed it in the first place.
 
Gulliver Foyle said:
It's not so much that they are stupid (though they often are, inherited wealth is a great disguise), it's that because they often have others do their thinking for them (even in the case of "self made" ones), they've lost the ability to think critically, or never developed it in the first place.
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I've been thinking about it and I'm not sure I agree with your general characterisation.

I think the vast majority of self made very rich people are not stupid, at least not in whatever area they made their money in. The sample of people who went down in a death trap submersible is very small compared to the size of the very rich people population, so you can't make generalisations from that.

Then there's this reply to one of my previous messages
rjh01 said:
You have the advantage of knowing the sub failed. They do not.
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Titan has always seemed a bit of a death trap to me, but the first time I heard of it, it had already puréed its owner and four other unfortunate passengers. Would I have the same opinion, knowing only that it had made several successful dives to Titanic? I'd hope so. There were some red flags, but would I have spotted them?
 
jeremyp said:
I've been thinking about it and I'm not sure I agree with your general characterisation.

I think the vast majority of self made very rich people are not stupid, at least not in whatever area they made their money in. The sample of people who went down in a death trap submersible is very small compared to the size of the very rich people population, so you can't make generalisations from that.

Then there's this reply to one of my previous messages

Titan has always seemed a bit of a death trap to me, but the first time I heard of it, it had already puréed its owner and four other unfortunate passengers. Would I have the same opinion, knowing only that it had made several successful dives to Titanic? I'd hope so. There were some red flags, but would I have spotted them?
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There are vanishingly few self made rich people. Even the ones that are considered self made come from a background of wealth or of sufficiently high class to have the right contacts. Unless you start from a high base in a capitalist economy it's nearly impossible to become rich, but if you're already there it's easy to become very rich.
 
Gulliver Foyle said:
There are vanishingly few self made rich people.
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Compared to the total population, maybe. Compared to two stupid self made very rich people in a death trap submarine, no.

Even the ones that are considered self made come from a background of wealth or of sufficiently high class to have the right contacts.
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Well no. Such people are not in the class of "self made very rich people" by definition
Unless you start from a high base in a capitalist economy it's nearly impossible to become rich, but if you're already there it's easy to become very rich.
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I do not dispute that but the impression I am getting is you want to believe that self made rich people are not self made. This is, of course, self contradictory.

However, let's step back a bit and just consider the class of very rich people. Are they less able to think critically and assess risk than the general population? I don't think there's any evidence that they are and I think your opinion is formed from a combination of your antipathy towards very rich people and a few well publicised examples.
 
JayUtah said:
If your glue turns to dust, you're going to have a bad day. But trying to sensationalize the surface area of the glue layer doesn't really impress me.
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I think it's a valid point. Not on its own, sure, but in conjunction with the void fraction. If you've got, say, 10% voids but the area involved is really small, that may not be so consequential. But 10% voids on a really big area is a ◊◊◊◊ ton of voids. Giving a sense of how much voids there actually were seems pretty relevant.
JayUtah said:
We've been laying up aerospace structures using epoxy for many decades without issue.
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And also achieving really low void fractions.
 
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