But Rush-manufactured carbon fiber subs DO have a 100% failure rate, over the life of the sub. Which ends when they fail. This isn’t a 100% failure rate over 60 years, or something, this is 100% failure within a year of manufacture.
Besides, deep diving subs should have a zero % failure rate in service. They should be retired before they get to that point.
I think we are splitting semantic hairs.
Yes he did, and it did work for a bit. But I also posted elsewhere here that if there were 2-3 more internal titanium support rings along the cylindrical hull, that might be enough for a hull serviceable for maybe 25x to Titanic.
It’d have to be failure tested and certified, of course.
Maxim 11:
Everything is air-droppable at least once.
Life is livable. Usually once.
Titanium rings could also have no effect, or they could somehow make it worse.
Unfortunately, since Rush sidestepped any of the engineering rigor or certifications these things normally need, we’ve essentially learned nothing from the Titan. For all we know he flipped a coin 12 times and it came up in his favor, until the 13th. The next Titan could have imploded on its first dive. We just don’t know.
Was that intentional? When he got into the sub, his name was Rush. But by the end, it was mush…
That’s not how these things work, usually. One can imagine a spectrum with these endpoints:
They both have the same average lifetime. But the second one will always last 100%/X% uses, whereas the first might fail on the first try.
Almost any engineered device falls between these two endpoints. The failure rate is not constant. Usually, this is described as a “bathtub curve”, such that there is a high failure rate at the beginning, which is usually eliminated by testing, a long period of a low failure rate, and then high failure rate at the end, when things start to wear out.
Maybe the sub did just have a constant 10% failure rate. More likely, though, it suffered internal “wear” as the carbon fiber started delaminating, forming voids, and so on. Eventually the damage added up and it failed. There was probably, on top of that, some random factor that also increased in variance as time went on.
Most engineered things will eventually fail in this way. Aluminum, for instance, will always fail eventually, even when the stresses on it are kept arbitrarily low. Neverthess, we can still build aluminum airplanes and other things because we can model that fatigue limit adequately.
Yes, as you say, there’s a possibility that we can build carbon fiber subs and monitor their wear and tear like OceanGate intended. That’s how we trust aircraft after all, whether they’re aluminum or CF, or bridges, or lots of things that fatigue.
Point being, it’s also possible that deep sea submersibles will never work with this particular material/design, so anyone who says “Well he proved it’s possible, it just needs more R&D” is speculating just as much as Stockton Rush did.
Like, people have proven it’s possible to survive Niagara Falls in a wooden barrel.
It’s possible. It just doesn’t seem very likely given that we can characterize CF in other applications like aircraft. Is there something special about submarines that means we’ll be forever unable to understand and characterize the failure modes? Maybe, but I think the balance of evidence points the other way. Especially as Rush’s incompetence has broad explanatory power for why this particular one failed.
We also have some pretty good knowledge of aluminum failure modes and testing protocols to let us know when the object in question is getting to that point.
I’m not sure where the science is on that for carbon fiber.
Well, it’s good enough that the 787 is considered a safe aircraft. But there’s still enormous research in the area which I’d say has yet to catch up with the depth of knowledge of traditional metals.
There’s also the question of how the state of the art knowledge and techniques trickle down to applications that aren’t quite as rigorous as aerospace. The tools, training, and general knowledge base takes time to spread out. Especially when the people involved don’t seem too interested in seeking out state of the art knowledge.
I feel like we long ago discussed the differences between the mostly tensile forces acting on an aircraft versus the compressive forces on a submersible.
Yes, they aren’t exactly the same thing (although it’s not as simple as that, either: a composite wing has both tensile and compressive forces on it). Which is why I say the depth of knowledge isn’t at the same level of aluminum, etc. But there also isn’t much reason to believe it couldn’t be improved.
Agree w @Dr.Strangelove that a well-funded patient quality engineering effort to develop design standards and construction techniques for CF submersibles & submarines may very well yield happy results.
Or not.
But we won’t know until we try, and what Rush did was just kids building a tree platform by comparison to engineering a skyscraper. We (humanity) haven’t tried yet, for any meaningful definition of “try”.
We’re collectively no smarter than 10 years ago for his ignorant blundering about the ocean.
But we are once burned, so maybe twice shy.
I used to laminate surfboards a long time ago, such a messy thing, more of an art then (bubbles and voids? haha…I was a hack…)Resin composite technology has come a long way at least.
That said, the very pressures that the ocean inflicts on metal hulls, has a way of strengthening them, with the micro molecule dislocations healing like a tough scar. With the carbon fiber composites, its the opposite, the glass fibers, or carbon, and the resins, epoxy and whatever else, really have no resistantance to high compression (from my quick AI readings). That said, Im not sure I would go that deep even in a titanium sphere!! Just kinda spooks me.
Mush was a reference to Musk, not Rush. (Rush was not a billionaire
like Musk or Bezos)
I recall a very casual conversation with an aerospace stress engineer who told me about meeting a submersible stress engineer and geeking out about how the math was exactly the same, only backwards!
That said, the behavior of the materials aren’t always as strong in the opposite directions, but that memory amuses me
The fact that there currently isn’t an industry guidance such as an ASTM or SAE standard for carbon fiber crewed submersible pressure vessels tells me the science is still a long way off from being commercially viable. Those “backwards numbers” are very very big!
From a Futurama episode, when the Planet Express spaceship sank in the ocean:
Farnsworth: Dear lord, that’s over 150 atmospheres of pressure!
Fry: How many atmospheres can the ship withstand?
Farnsworth: Well, it’s a spaceship, so I’d say anywhere between zero and one.
It did make it to the Titanic on multiple occasions. He built a rickety skyscraper out of popsicle sticks… but it stood, at least for a little while.
I’m a believer in proofs of concept. A POC doesn’t have to be perfect; it just has to work once. The Wright Flyer was a POC. While the Wright bros were undoubtedly more diligent and competent than Rush, the Wright Flyer was arguably even more of a deathtrap than the Titan, and had even less commonality between modern aircraft design than the Titan did with modern sub design. But it proved the concept of controlled heavier-than-air flight.
Of course, taking paying passengers onboard was inexcusable. And you may well be right that this turns people off from carbon fiber subs for a long time. Nevertheless, it did prove that it can be done once, and history suggests that if you can do something once you can do it again with enough effort.