r/interestingasfuck • u/ThugLeeVoguee • 1d ago

The implosion of the Titan submarine (OceanGate) was so rapid that the pain wasn't even registered by the brain. They didn't feel anything at all. Utterly instantaneous.

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u/ZenRage 1d ago edited 1d ago

One of the really great things about steel is that it is ductile. It is not a brittle material. Steel can undergo very great detectable deformation before it fails.

If you have even been in a (steel) submarine you know that it SHRINKS measurably as it dives. (e.g., A tight string/wire across a compartment will go slack during a dive.)

That deformation translates to notice about a pending failure and TIME to remedy it. ("It should not be bending like that; stop going down and start going back up...")

That is just not the case with brittle materials like carbon fiber. They fail suddenly and all at once. Think of a glass canning jar: if you drop it, it either breaks/cracks or is unharmed; there is no in-between.

Making a PROTOTYPE submarine out of carbon fiber and riding it down on what is effectively a test dive is suicide.

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u/chefbobbyjay 1d ago

Which is why you leave engineering to engineers and not try to build your own home made sub. Well explained.

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u/Chemical-Elk-1299 1d ago

Don’t forget he bragged about getting the carbon fiber secondhand

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u/Fear023 22h ago

Everyone should watch the ocean gate documentary. He did so much shit wrong. When the dive season ended, he left it out in freezing temps because he wanted to save money on transport costs.

That's when I think their qa manager left. You're apparently really not supposed to do that with carbon fibre.

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u/Rico_Solitario 16h ago

And the guy came from old money. He was not hurting for cash he was just a greedy arrogant son of a bitch

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u/Disastrous_Visit9319 9h ago

Bro was the personification of late stage capitalism. Do everything cheap as possible to maximize profits who cares if it harms customers maybe just pay a fine or bribe the cheeto. He forgot he was putting himself in the same position as the customers.

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u/lazylazygecko 5h ago

I remember there was a comic about billionaires escaping to their own man-made island, but people still managed to infiltrate it cause they had cut so many corners on security. At the time I thought that just sounded too implausible, and then the submarine implosion happened lol.

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u/jake04-20 1d ago

Didn't he also basically admit that he knew of other experts that stated carbon fiber was not the right material for something like that, and he pompously bragged something along the lines of "well clearly it's working for me, I've done X dives and the sub is fine?"

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u/faldese 1d ago edited 1d ago

Not the way he's done it, but it's worth noting that the material hasn't been written off by submersible experts. Initially OceanGate was doing much shallower dives, and a carbon fiber hull (not his carbon fiber hull though) might have been well-suited for that. But Stockton Rush wanted big big money and a big big reputation so he saw Titanic as the ultimate goal and, well, he did get the latter wish in the end.

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u/Gregorymendel 1d ago

He increased his net worth tremendously with that intelligent move 🙏🙏🙏

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u/bradimir-tootin 18h ago

I have 2 degrees in materials science, BS and PhD. I can put the sheer foolishness of this mistake in perspective. This is the kind of question you can ask a 2nd year mechanical, civil, or materials engineering student. It is also the sort of question that is considered a gimme.

Somewhere around the end of the first month of the intro to materials course you learn about ductile vs brittle fracture and materials. You are shown engineering diagrams, fracture surfaces, atomicistic and molecular reasons as to why materials are ductile or brittle etc. You learn that brittle materials fail fast and that the cracks in them propogate at the speed of sound (km / s). You also have quiz, hw, and exam questions about selecting materials for different applications. This mistake isn't even about leaving it to professional engineers this mistake is the kind of thing we use as freebee points on a quiz for the youngest students. THAT'S how bad this mistake was. We expect what are basically children to get this correct.

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u/chefbobbyjay 18h ago

Funny story. I’m a 2nd year engineering student and I’m taking intro to materials and.. yup. Ya nailed it lol

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u/Calculagraph 1d ago

I mean, how did the first engineer become an engineer? Checkmate.

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u/SuperCruisePanther 22h ago

What came first, the physicist or the engineer?

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u/PH_Prime 23h ago

Just wait until we have similar rich guys building subs from a chatgpt output

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u/Kaa_The_Snake 23h ago

I’ll also leave the diving to the engineers tyvm!

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u/chiefteef8 14h ago

He was an engineer. Just a bad and arrogant one 

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u/granitefloors 8h ago

He had engineers to build it. They just went along with it. The one engineer who spoke to was fired

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u/Festival_Vestibule 23h ago

He was an engineer. Aerospace.  Last time I checked James Cameron isnt an engineer either.

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u/Nerevarine91 21h ago

James Cameron doesn’t go down to the depth of the Titanic in submersibles he built himself out of cheap materials. You don’t have to be an engineer to avoid doing that

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u/fused_of_course 22h ago

James Cameron is smart enough to listen to engineers

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u/Festival_Vestibule 7h ago

I'm not defending the guy. Im just saying that he had an engineering degree from Princeton.  And now you know that too.

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u/fused_of_course 5h ago

When did I say I didn't know that? I just meant JC doesn't pretend to be an engineer - he just talks as an enthusiast. Rush didn't listen to other people.

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u/Festival_Vestibule 4h ago

Talks as an enthusiast?   He designed and built his own sub. He's widely regarded as an expert in the submersible industry.  Also holds more than one patent in underwater engineering technology.  Enthusiast my ass.

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u/fused_of_course 1h ago

So is he an engineer or an enthusiast? My dad built a car because he's an enthusiast not a mechanic. You made the point that there is a difference not me so don't try to put me on the spot to explain your point. If he's not an engineer - which you said he isn't - then what is he? Because the word used for an amateur who gains competence in a space is enthusiast.

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u/chefbobbyjay 22h ago

Well there ain’t no damn aero or space down there.

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u/Usual_Ask_7833 1d ago

It wasn't a test dive, the Titan actually made it to the Titanic 13 times prior.

The issue, as explained by James Cameron, was that each time a sub dives the material experiences fatigue damage and eventually fails. It's like a soda pop tab, it doesn't break the first or second time you bend it, but if you keep bending it then it will eventually break.

Rush didn't want to do the standard test to the hull after each dive because it was expensive and took a long time so he created his own acoustic monitoring system which obviously didn't work.

James Cameron says subs are normally retired after 6-8 dives, if Rush wasn't so cheap and replaced his sub more often he would probably still be doing dives today.

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u/FaudelCastro 1d ago

The acoustic monitoring worked, he ignored it.

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u/Spear_n_Magic_Helmet 23h ago

Yep. Also ignored the “oops we let the untethered submersible bang dozens of times against another vessel in heavy ocean for several minutes” on the mission prior. And left it outside in winter. And and and

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u/flaming_burrito_ 20h ago

This is why when you’re an inspector or safety supervisor in any serious position, they drill into you to never assume that people will follow a rule, no matter how obvious it is, or how many flashing lights you put in their face. Given enough opportunities, it is a near guarantee that eventually someone stupid will do the obviously stupid thing. Human creativity, and thus capacity for stupidity, is nearly infinite. People will find a way to bumble their way into situations you never even considered could be a possibility, because you are likely a reasonable person with a rational mind. They, however, are not.

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u/bigboyjak 15h ago

Even worse.. when you look at the data, even a layman like me can see that on dive 80 something OBVIOUSLY broke. The data from their own monitoring system shows obvious discrepancies from the dives before and dives after.

Mind you, this data is from how the hull is flexing and stressing under the dives.. Perhaps the most important data to a submersible.. and it was just ignored? Never looked at?

That's what I found most insane about the whole thing. Their own data showed something went wrong..

Here's an image I stole from another Reddit thread that shows the data I'm talking about. Blue is dive 80, orange is dive 81

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u/SpiritJuice 20h ago

Final report revealed that only five of the eight monitors were working at the final dive. Just more shit to add to the pile of things going wrong due to human error.

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u/AirconGuyUK 22h ago

I'm still surprised it managed to make it down even once. It's such an unsuitable material to make a submarine out of on paper.

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u/blackhorse15A 21h ago

each time a sub dives the material experiences fatigue damage and eventually fails

This is not true for all materials. Steal can be designed so that the load/deflection stays below a certain amount then there is not fatigue damage and you have infinite cycles. Design it or allow it to go past that load and then you will have a fatigue problem where repeated cycles add up until a failure happens. But it is possible to design steel for infinite cycles.

Aluminum however, does not have this property. No matter how small the load, how little the deflection, it will eventually fail due to the fatigue building up. That's why you can take a piece of aluminum and just bend it back and forth and back and forth until it eventually breaks. You can the part strong or the load on it smaller, that will increase the number of cycles, but there will always be a limited number of cycles and then it fail from fatigue.

Carbon fiber...well... cabon fiber in a resin polymer is not a metal. So technically it doesn't fail from fatigue the way metals do. But, that's actually kind of a bad thing because it's not as predictable. So under small loads carbon fiber is actually very good for fatigue- better than a lot of metals. However, they are many other factors that will degrade the resin or the fiber that metals would t be affected by. So a lot of other things are breaking it down even without any load at all, just sitting out in the sun or during storage. But when we start talking about very high loads (like deep ocean) that is very similar to metal fatigue in that it will start to create crack that propagate and then delamination occurs then failure. In metal that's a microscopic process at the grains of metal. In the carbon fiber it's a lot bigger and once it starts it can accelerate and then go catastrophic quick. So cyclic loading under high loads does cause carbon fiber to start to fail, and problem grows until it fails completely. Kind of like metal fatigue. But the process is different and the predictability isn't as good. Metal objects we could measure the deflection/load and just count the number of cycles then pull it out of service at a certain number (which is like 90% of expected life to account for variations and use different numbers based on how much safety margin you need.) But carbon fiber you'd really need to be inspecting it closely, like ultrasound the whole thing, regularly to keep an eye on it and detect the problem before catastrophic failure happens. Safety critical stuff might need that every time. Or, save a bunch of money and roll the dice and hope you don't die.

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u/IheartPickleSoda 20h ago

They did pressure tests of smaller scale models and not a single one passed.

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u/Theyul1us 15h ago

Dont forget that he fired and sued the engineer that said it wasnt safe

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u/Waffle-Crab 22h ago

I think the investigation found that the point of failure was the seam between the steel cylinder (connecting the front dome) & the carbon fiber hull.

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u/Featherforged 1d ago

Isotropic materials like steel are really easy to observe strain and check for flaws. Very easy for pressure vessels. However, ductile steel still fails in a brittle manner when cyclic loading is encountered.

Carbon fiber is blamed a lot here, but not for the right reasons. If 1 lb of carbon is used versus 1 lb of steel, the carbon pressure vessel is 7 times stronger and far, far safer.

The real problems are the novel and amateur ways it was used, the lack of knowledge on carbon submersibles, the abuse of the sub (towed, left in freezing weather, ice expansion, left outside), and the lower weight/lower strength walls used.

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u/TrulyWhatever09 1d ago

Isn't it also the case though that carbon fiber's strength is significantly under tension than compression?

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u/Featherforged 1d ago

Carbon fiber is 50-70% as strong in compression vs tension.. but still obliterates steel in a strength to weight comparison.

It also becomes more sensitive to fiber alignment in compression. 

Lb for lb, a carbon vessel is an absolute beast. A carbon bicycle that weighed as much as a steel bike would be an absolute insane structural monster.. but carbon is used to save weight, so it's seen a lot in failures because its cutting those lbs. And that's what ocean gate was doing, pushing strength limits (along with the worst design choices)

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u/MMRS2000 1d ago

👆🏻 This guy carbon fibres.

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u/steed_jacob 23h ago

Can you recommend me a book bro? U just seem to know some stuff that scratches my brain right

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u/Ya_Got_GOT 1d ago

Im not a structural engineer, but my understanding is  that the issue isn’t pound for pound strength or application so much as carbon fiber's high tensile strength not preventing incremental and unrecoverable delamination caused by cyclic compressive fatigue under deep-sea pressure. No matter how strong it can theoretically be, it is not stable enough under its intended use for the application. 

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u/Featherforged 1d ago

Carbon fiber is used safely in thousands of applications. A thin carbon bike can easily have more compression stress than a super thick walled ocean submersible. Fighter jets, passager jets, missiles, sailboats, all trust it.

This is more of a case of, we made the walls too thin, slapped it together in a dusty room with poor directionality, glued it with some random epoxy, then left this soaking wet sub in freezing ice conditions, in lightning, rain, and sunlight, towed it underwater for miles, banged it around, and had the engineering leadship quit and get sued because it was so scary.

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u/Ya_Got_GOT 1d ago edited 1d ago

I mean sure they fucked up many ways but CF being safe for a bike doesn’t make it safe for a deep sea submersible. Different stresses, and different consequences for failure. You shouldn’t even mention such unrelated applications. 

Specifically CF is bad for deep sea submersibles because tensile strength to weight ratio, which is mostly what makes it attractive for the examples you cited, is insufficient in and of itself. You need omnidirectional, not just tensile strength, and stability and observability as to the health of the material across compression/decompression cycles. That’s why the industry doesn’t use it. If they could do so they would because it would be cheaper. 

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u/Featherforged 1d ago

Carbon fiber in a submersible is just pure compression for a sphere. Insanely simple. Far simpler than bike geometry. (Going with a cylinder was a poor decision for ocean gate)

But aircraft wings are very similar with respect to consequences.

There's nothing inherently different about compression strength on a submersible wall versus a wing strut. If anything, wings are far far far more complex and weight sensitive.

Make a sphere with 12" thick carbon walls in a clean room and it's far safer than steel. (It is harder to detect flaws via xray and other methods and that is the largest flaw compared to isotropic steel, titanium, etc)

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u/Ya_Got_GOT 1d ago

Uhhh. Yeah so you clearly aren’t versed in the subject. Your parenthetical closing statement is like the entire fucking point dude. 

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u/Featherforged 23h ago

I'm a senior mechanical engineer.. been doing this stuff for forever. Am well versed.

My responses are of nuance. The pros and cons of carbon fiber, rather than it's all good or bad.

I think people like to dunk on it as a material, not understanding it fully. It's nuanced. It's crazy strong, light, stiff, it's directional. It's seen in failures because it's used at the very edge of it's strength (no one makes a 40lb carbon road bike, but if they did, it would be an absolute tank)

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u/SpiritJuice 1d ago

I followed this case quite a bit. As far as I know, the final report shows that a carbon fiber wasn't the cause of failure, as other carbon fiber hulls have been used for deep sea submersibles before. Yes, steel and titanium hulls in a sphere shape has been the standard for many reasons. The main issue is that the hull was at the end of its life due to how many dives it had been on and needed to be retired. A new sub needed to be built, but Stockton Rush was egotistical and in denial. Money played a huge part as well.

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u/IheartPickleSoda 20h ago

He was way upside down financially after enough failed dives and it seemed like he was ready to go down with the ship, unfortunately nonchalant about taking others with him.

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u/ZenRage 1d ago

That points to a different problem that steel ALSO solves.

Most materials have serious fatigue issues where repeated loading and unloading leads to loss of integrity and eventually catastrophic failure.

This occurs in most materials, even the ductile materials.

Steel is an exception: it has what is called endurance limit and it approaches it asymptotically over huge numbers of cycles where, effectively the life is practically infinite (it would take so many billions of cycles that we cannot expect to destroy it during the thousands of years remaining to human civilization).

This is another good reason not to use carbon fiber in an prototypical fashion at all much less used carbon fiber.

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u/MelangeBot 1d ago

Nobody knew it was end of life because you can't model a fibre resin, unlike steal or titanium where a model can tell you how many cycles are safe.

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u/kallebo1337 1d ago

A military submarine shrinks when diving? By how much?

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u/Adjective-Noun-nnnn 22h ago

Yep. Metals have a usefully wide region of elastic deformation. You can deform them a bit and they spring back.

Composites like carbon fiber can fail gradually, typically through delamination or the breaking of individual strands of fiber... which is exactly what that submersible did, and the moron who built it thought it was breaking in. Composites don't break in. They just break.

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u/ChimRichaldsOBGYN 1d ago

I’ve never watched and WILL never watch this documentary the whole story makes me sad and furious. But was there a reason why they used CB other than “I’m a hotshot CEO fuckhead and I watched F1 on Netflix and now I think carbon fiber sounds cool let’s do a bunch of that in a submersible”.

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u/Toastwitjam 21h ago

Also carbon fiber doesn’t undergo elastic deformation only plastic. Like aluminum aircraft hulls eventually after enough loading you will need to replace it. Cracks will form and propagate no matter how gentle you try and be with the cyclic loading.

With steel as long as you stay well within the elastic region there’s very few things that can make your loading situation cause failure eventually through fatigue behavior alone.

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u/5GCovidInjection 19h ago

So I agree with all that, but what makes carbon fiber suitable for commercial aircraft like the Boeing 787, which undergo similar pressurization cycles as a submarine?

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u/Tickle_My_Sphinxter 18h ago

Carbon fiber is a perfectly suitable material for both. The Titan sub was poorly designed, poorly built, poorly tested, used expired materials, damaged in storage/transport, etc. It failed catastrophicly as a result of all of those factors.

The Titan team simply lacked the knowledge and experience to be doing what they did. If they had made a steel sub, or a titanium sub, they would have eventually killed themselves a slightly different way.

The armchair reddit experts claiming that carbon doesn't have fatigue resistance or that it can't handle compressive loading are factually incorrect. We wouldn't be making cutting edge aircraft, F1 cars, bikes, skis, etc out of it if that were true. All of those applications involve cyclic compressive loading and minimizing weight. 

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u/ZenRage 7h ago

There are a few important differences there, not the least of which is the risk from failure.

If your sub fails at 110 atmospheres everyone on board dies right away. If your plane fails at 0.4 atmospheres such that the superstructure flies off of the steel infrastructure, the pilots descend to a safe altitude and fly to the closest airport and land. A few injuries and even some deaths may result but it is not instantly lethal for everyone. Something very much like that happened to Aloha Airlines Flight 243 on April 28, 1988: of the 95 people on board 94 survived.

Another important difference is the difference between high cycle and low cycle fatigue failure. All other variables being equal brittle materials like carbon fiber do quite well with high cycle (low load) fatigue and quite poorly with low cycle (high load) fatigue. Cycling between 110 atm and back to 1 is probably more like low cycle (high load) fatigue while cycling between 1 and 0.4 atm is probably more like high cycle (low load) fatigue.

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u/SLAMMERisONLINE 18h ago edited 18h ago

One of the really great things about steel is that it is ductile. It is not a brittle material. Steel can undergo very great detectable deformation before it fails.

Steel strain hardens. It becomes stronger right before failure. It's likely that it would've made significant noise as a result of strain hardening, potentially giving them a very loud "wake up" call before finally failing. With time to act, it could potentially have saved their lives.

Sudden and catastrophic failure is one of the big downsides of brittle materials.

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u/Autobacs-NSX 18h ago

The Titan went to Titanic depth something like 8 times successfully. The sub worked. It was on a particular dive (I want to say dive 87) that the Titan made an uncharacteristically loud BANG during surfacing and Stockton chose to ignore it. The next dive was the fateful one. 

So yeah. Carbon fiber pressure vessel works, even Stocktons janky ass one worked. It’s just disposable. But making a new one every handful of dives probably isn’t financially viable, so the business plan was not good. 

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u/tessathemurdervilles 17h ago

As a layperson who knows nothing- this is really interesting thank you!

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u/gergosaurusrex 1d ago

Carbon steel has similar mechanical properties to cold peanut butter, except it's as if a cat stepped on a cosmic keyboard and added a few extra 0s to its strength