Titan Sub | carbon fiber - Detailed Tour

[@fridaycaliforniaa236]

As a guy who worked a lot around advanced composites on [military] aircraft, and also the ones used on sports car in my spare time, all I can say it that CFRP is light and strong, but it gives almost no warning when it has to give... Just look at F1 cars when they hit something, and you'll have the whole view of what happens when CFRP fails : it shatters like a little grenade ! Thousands of sharp little black carbon blades spinning in all directions. And to add to the injury, CFRP is not good at withstanding compressive loads. I mean way less than what it is able to do in terms of tensile strength. That's why many helium/nitrogen/oxygen/"gaseous whatever you want" high pressure tanks are made of composites in aviation and rockets and work very well. That's also why nobody ever decided to build a fiber-reinforced plastic submarine before. If composites were good for submarines, the military subs would have done it a long time ago. - Pressure trying to escape from inside = yes - Pressure trying to crush from outside = big no

[@catsupchutney]

Exactly! I hate to be an armchair engineer (though I have an engineering degree), but nowhere in the "Why carbon fibre was a very good idea" was mention of demonstrated repeatable reliability as a pressure vessel. I remember one instructor hammering home that software models are never as reliable as actual tests; software models are used to save testing costs. This design was *never* demonstrated to be a good idea. Every design team member should have been asked to send their favorite pet on test dives in that thing for several years. Lets see have cavalier they would have been then.

[@johndoles3713]

@@fridaycaliforniaa236 the fukery

[@linuxrwanda]

You hit the nail on the head: in an application where the loads are compressive, CFRP is not a good choice.

[@shawnhoem487]

From someone who works around advanced composites in aviation. Carbon fiber composites are strong in their narrow operation limits. Outside of those, stuff is like paper. Additionally, it requires inspections. If not done.... You have a mess just like this.

[@mhughes1160]

Still waiting for the official results 🤔

[@thatguy9088]

Out of curiosity, how does temperature and torque affect such materials? Not to imply those were a factor here, I am just simply curious. Everyone talks about the tensile strength and the like, but not other things.

[@shawnhoem487]

@@thatguy9088 well, with bonded materials temperature is a big deal. The glue that holds a composite together can be greatly affected. For example (remember when operated outside its limits) as it gets hot, the glue loses its ability to keep its chemical bond and the composite delaminates. As for torque, compression, and tension that really depends on the weave and the bias of the fabric in the composite. A general overview hope it helps.

[@thatguy9088]

@@shawnhoem487 It does help, thank you. I was just musing on if temperature might play a factor as well. Not in this circumstance, just the material in general. Thank you for your time and thoughts on the matter.

[@goldengoat1737]

I know from mountain bikes it is theoretically really strong and lite but if there is one hairline fracture the whole integrity is toast. I prefer aluminum it might not be quite as strong but is way more durable

[@tjw4947]

The primary problem with Titan was the temperament of it's creator. Too many corners cut for limited success.

[@ElectricalExistence]

maybe if he had hired more 50 yo white guys, the ones he said he didn't want, cause not diverse enough, he'd still be alive.

[@CJODell12]

@@ElectricalExistence”wokeness” had nothing to do with it. It was Sterling’s massive ego that did them in.

[@ElectricalExistence]

@@CJODell12 whatever bud.

[@callmesceptical9114]

Arrogant, egotistical, fool! Unfortunately he took 4 naive souls with him to an avoidable demise.

[@jamesadams893]

The primary problem with Titan was it imploded

[@TheOneWhoMightBe]

I remember seeing the edited videos of the build process, and what stood out to me as a non-expert was the process of bonding the ends to the CF tube; the glue was hand-applied (and the surface apparently not cleaned beforehand), bare hands were touching the CF during the application process, it was not done in any sort of clean-room (lots of dirt and dust in the air), and there was exactly no squeeze-out when each sphere was slid onto the tube, meaning there were almost certainly voids.

[@MisterDeets]

Agreed. I wonder if they had significantly extended the flanges on each end and properly glued them if the sub could have made more cycles before imploding. I suspect that might have been the case.

[@jeerzinqd6831]

No squeeze out is what shocked me.

[@LordPrometheous]

That stood out to me as well. This was not the time for handmade structural components.

[@strayblackcatsmeow]

I agree, glue being the only joint between dissimilar material shear. Should have been pocketed so compression could only push the parts tighter, improving seal and not shear from partial glue failure.

[@Kieselmeister]

​@@strayblackcatsmeowIt WAS pocketed, the titanium flange had a 'U' shaped profile that the carbon fiber slotted into. The glue is a red herring, because so long as the carbon fiber tube remained intact the end caps would be held in place by water pressure alone. The real problem with the joint is the shear stress from differential expansion at the point where the titanium 'U' no longer overlaps the carbon wrapped tube. Carbon fiber has negative thermal expansion while Titanium has positive thermal expansion, and carbon fiber is extremely rigid while Titanium has high ductility. There is also the problem of the differential expansion between the composite overwrap and the inner metal tube, which would cause the tube to shrink faster than the carbon fiber, which would promote delamination and buckling of the individual carbon strands. Additionally, the pressure cycling in compression would compress the polymer resin matrix of the composite more than the carbon fiber, which would lead to microcracking of the resin when the pressure was released. This would have potentially allowed saltwater to infiltrate the matrix, which could leave salt deposits behind when it was squeezed back out of the cracks during the next cycle. The salt crystals could then induce layer delamination, or even direct shearing of the carbon fiber strands.

[@wazza33racer]

Ive worked with Carbon fiber based competition race cars......it is a fantastic material given its strength and rigidity for the weight. However, every and any material must be tested exhaustively to make sure it is suitable for an application and not just "shell be right mate". Same goes for the attachment methods of the end domes......testing is needed.

[@prestonburton8504]

indeed! Haas! F1

[@itoibo4208]

Yes. I can see how the expense of this thing could cause someone not to want to destroy it, but I would not be comfortable with it until I had pushed it well beyond its target conditions for many cycles. It should have been pressurized, dropped, banged with rocks and things, until one was sure it could handle the loads.

[@alext3811]

Exactly. In areas it has been used for decades like race cars (as you mentioned), or aviation, they know proper implementation. Oceangate didn't, but they acted like they did.

[@phillyphil1513]

@@alext3811 re: "In areas it has been used for decades like race cars (as you mentioned), or aviation, they know proper implementation." bingo, i personally was using Carbon Fiber at Agusta Aerospace for the doors of the A109 (ie, the helicopter featured in the first Jurassic Park movie) back in 1993 or 30 years ago as a "mature application", and the material was already in use with NASA and the Military way before that. so see, the problem comes in that those who are "baby young to the world" and have no life experience are EGOTISTICAL and naturally tend to think things were just invented, rather than seeing things properly through a "lens of history".

[@phillyphil1513]

@@alext3811 re: "Oceangate didn't, but they acted like they did." see Wikipedia entry for FRAUD. also entry for Bernie Madoff/2008 Collapse of US Housing, Beth Holmes/Theranos, Trevor Milton/Nikola, Sam Fried/FTX Crypto, Charlie Javice/Frank, and Elon Musk/Tesla/FSD.

[@bt81-]

Mike, I don't often comment on content I come across online, however I believe you have provided the clearest, most concise yet suitably detailed and realistic summary of what may have happened, with the available information and a solid understanding of materials and processes. It goes without saying that there could easily be a lot more maths and physics to quantify but then this would become a lesson in engineering rather than a clear relatable clip. The perfect balance, and your included animation is second to none. Well done sir!

[@Mike-Bell]

Thanks. Much appreciate your comment!!

[@eschdaddy]

His video is just plain wrong. I’m a mechanical engineer who has experience in carbon fiber and he completely misses the point. There is no counter force from CF tube for the pressures required. Aviation is completely different than this application. MANY engineers warned him and he ignored all of them.

[@NewEarth79]

I agree, I've seen about 40 video's related to titan and this is one of, if not the best one I've seen.

[@EugeneSamuel-h9w]

Agreed well put together little doco

[@eschdaddy]

@@EugeneSamuel-h9w : But completely wrong. Doesn’t matter how professional the video if the info is still wrong. I hope next time he does the same quality video editing, but along with accurate info.

[@tcmtr6]

The Titan is really compact now.

[@vanderlinde4you]

There where 5 people added to the already existing graveyard. I remember a video of titanic explorers saying to look through the window of the titanic and having the feeling to be looked at back. It is a scary place down the bottom of the ocean. Really scary.

[@phillipschaber7836]

I woudlnt say compact so much as its now a "lego set" with a few thousand pieces to be put back together...

[@GrahamHomes]

Great piece of work. I worked in endurance testing high pressure equipment up to around 3000 Bar. This sub failed at around 400 Bar. The failures at these pressures progress through the structure as shock wave rather similar to an explosive event at around the speed of sound for that material. The stress is already in the carbon fiber and you get a cascade failure as the local support is removed by the failing material. I have no data for the speed of sound in carbon fiber in this configuration and pressure but it will around 3000 meters/sec per second much faster than the speed of sound in water at 1450 meters/sec. This means the tube may well failing faster than the water can keep up with . This would cause a huge mass of water accelerate conically inward ( the open end toward the direction of travel) in the direction of the end that did not fail first. As the in rushing water ( many tons) is at really high speed ( 150 mph +) when it collides in the center it creates an even faster flow towards the remaining end . When this hits the end you get the mother of all water hammer events blowing out the window. The violence of this event is difficult to comprehend. This explains why the window was not with the sub. The blown outward flange was on this end too so I think this could be included in this violent event. The whole thing would look a bit look like the copper in a shaped charge anti tank round going off. All this happened in less four thousandths of a second the victims could not have sensed any of this thank goodness.

[@protator]

The way they glued the titanium rings to the CF alone, absolutely ridiculous. They rolled the glue onto both parts, set the ring on top of the tube, done. No elaborate resin infusion technique or so to prevent voids in the glue, no vacuum bagging afterward, no autoclave curing. Nothing. They built pressure vessels like it was an Arts'n Crafts project for their Etsy shop or something. And then there's the combination of CF and titanium. I'd have to look up the exact numbers, but I'm pretty sure titanium has at least twice the the temperature expansion rate of carbon. They glued that hull together during summer judging from their clothes and sweaty foreheads, then repeatedly sent it down to the bottom of the ocean where it's 0°C. The internal sheer stresses in those halfassed glue joints must've been substantial.

[@kevingalgay]

Listen as a plumber I was concerned it might leak.

[@kuei12]

I wonder if it would have worked if they had not been so sloppy in their manufacturing process.

[@alienastarz3043]

And they left it a whole year in parking lot not even indoors-plus every time travelling in open ocean with it just hugging behind the ship cause there was on space to fit it on top -plus it was struck by a lightning 🎉

[@carbonking53]

I have a family member who holds a PhD physics that has 40 years of experience in carbon fiber development and production. Having designed and built several carbon fiber production facilities all over the globe, I trust his expertise. He told me there was no way he would have ever even gone diving in the deep end of a swimming pool in that "contraption," as he called it, much less down to 12,000 feet. He knew right away based on the construction and lack of attention to detail and safety of the operation that they suffered a catastrophic implosion.

[@ElectricalExistence]

i think it was the dissimilar materials compressing at different magnitudes that made it fail,perhaps he should have just made it 7 tons heavier.

[@ElectricalExistence]

if he had made it properly, perhaps there would have been less issues actually being able to get people to pay him tons of money to dive in it. the only people that did go were, well, fools.

[@dlsimmonsjr1]

Thank u!

[@gummiente3622]

​@@ElectricalExistencethere is no way to do this properly. You can not use different materials with different behavior unter pressure to build something like a sub.

[@Toobzilla]

common sense alone would tell you multiple, if any dives to bottom is a death wish. that said, im of the limited knowledge based opinion that if they would have dived at more controlled rate the hull may have been up to keeping the 5 alive.. its my undsrstanding that they descended at almost 3x the desired rate. too much pressure increase too soon means the hull saw way too much change in pressure way too quick, flex, shrinkage, warpage all too much too soon. slower dive rate means the hull would have time to acclimate itself *sort of* to the slower pressure changes keeping the vessel from rapidly flexing & ultimately crushing itself to leak status then.... im by no means suggesting that carbon fiber could be used. i have common sense & very little experience with carbon fiber motorcycle parts. im qualified to suggest or recommend anything except objecting to making hulls going to extreme pressure depths made from stale carbon fiber.

[@Herzankerkreuz67]

After seeing the accommodation, I can honestly say that there isn't enough money or any other temptation humans usually respond on in order to get me into such a ridiculous excuse of a submersible sardine can. Absolutely nuts.

[@itoibo4208]

I have little interest in seeing an old steel ship wreck. The real thrill would be in designing, building, and testing/operating it.

[@juri_xiii9977]

It was a Pipe Bomb basically.. And I think Titanic is a Grave site, no Tourists should get to it. It's a Tomb to hundreds of people.

[@pazsion]

No point in doing it if you don’t have and assurances that you would survive. None of that was there, yet they all got in it anyway… They seemed to of gotten into a mindset of not speaking up anymore and just let him manipulate them without questioning… that right there should have been more than enough to back out.

[@ProfessorDIY]

It was not designed to be a luxury sub so the accommodations are not relevant

[@charlesspringer4709]

@@pazsion 16% of the population has an IQ below 85.

[@seanpeacock4290]

you started by saying that the media made the carbon fiber hull as a bogie man and then you described how you think the carbon fiber failed. Wrinkles verse de laminating is really just semantics for the average person. The key is that the hull was untested and went straight to commercial use at extreme depth. Even aircraft with aluminum hulls at 1 atmosphere need to be regularly tested for cracks caused by regular pressurization.

[@Vincerama]

Thank you for this video! It's the only video or article I've seen that actually attempted to show the Titan components, what was on board, what was in the tail cone, etc.

[@anninaut]

Best explanation video i've seen about the titan sub. When they did put the first Titan sub model into the pressure chamber the cf started failing at the titanium dome at that glued joints. Thats why the cf hull was ribbeled appart in axial direction and also tearing appart the small titanium overlap parts. And i very much believe the exact same axial failiure of the cf hull at the glued titatium rings happened again, as it already happened with the test titan in that pressure chamber. There are photos on the internet about that ribbeled-off cf hull. Sorry for bad english. 👯

[@DanielVerberne]

I'm a layperson without any engineering knowledge, but I like what I'm hearing in this video. It sounds reasoned and I like that credit is given where due, caveats are clearly stated and safety and reliability is upheld beyond all else. I appreciate the expertise and knowledge and background work that has clearly gone into making this video - thank you.

[@vanderlinde4you]

There was a CEO so convinced enough to drag down 4 people with him deep below the sea. Tragic. However the speed of collapsing and death where instant.

[@captainwin6333]

The big difference between composite and metals is metals can compress at a molecular level under pressure then expend back to normal when the pressure is removed. It can do this repeatedly and engineers can work out how many times it can safely do this. Composites on the other hand don't compress well because it's not a homogenous material. The carbon fibres and resin have different properties and on top of that, finished carbon fibre is not homogenous like Titanium or Steel. It will have differences throughout the material. Some parts may have a bit more resin, some less, some fibres might be closely aligned while others a little bit further apart. That doesn't make much difference in normal applications but 4KM down in the ocean under those sorts of pressure, small variations can have enormous consequences for the strength of the vessel as a whole. It was reported that the carbon fibers’ axial compressive strength is only 10%-60% of their tensile strength and their transverse compressive strength is 12%-20% of axial compressive strength. Titanium on the other hand, it's compressive strength is more than twice it's tensile strength. Stockton Rush was a snake oil salesman and he knew that's what he was. He knew he was taking a massive risk with his sub. The structure of his company illustrated this. The holding company was registered in the USA while the company that operated the sub and rented out the seats was based in the Bahamas, thereby avoiding US regulations.

[@jeebusk]

I agree he was primarily a salesman,

[@prestonburton8504]

so, not being argumentative - i was involved in aerospace when composites first entered. everyone said that nothing would replace aluminum (titanium/steel in empennage/landing gear main spars and stringers) - we witness today, 787 that have mostly solved these issues.

[@SuperLordHawHaw]

Metals will develop fatigue cracks but that is something you should be monitoring. CF will crack and they heard crackling noises on some test dives. They didn't seem to do enough testing and were overly optimistic about the lifetime of the sub.

[@jeebusk]

@@SuperLordHawHaw an employee was asking to scan the hull and he was fired.

[@alfredomarquez9777]

​@@prestonburton8504SORRY, BUT your saying is completely NONSENSE... Comparing a composite to aircraft aluminium is wrong, but trying to compare the stress field of an external pressure vessel with the stresses on any airplane is ridiculous. Assuring that, because composites have displaced (SOME) of the uses of aluminium in aircraft, regardless of the resistance to change many years ago is completely wrong. THERE IS A REASON A COMPOSITE PRESSURE HULL IS NOT A GOOD IDEA.

[@The.Spicy.Raccoon]

I always appreciate your ability to take such complex concepts and communicate them visually and verbally in a way non engineers can grasp these very complex concepts in a more tangible and meaningful way. Thank you for your hard work. I always learn so many new concepts to learn more about.

[@SpaTZz9]

I think one of the main issues was the repeated stress on the Carbon fiber. It can only be subjected to these stresses for so many cycles. Also, you have to take into consideration of the four different materials. The carbon fiber, Titanium, the adhesive used and the view port.

[@Markus117d]

Exactly, Those materials all behave differently in such extreme conditions, Bonding them together put extra stresses through eachother..

[@ouknow1446]

So one or two dives. Maybe three, then implosion.

[@Toobzilla]

add corrosive salt water to the mix and....

[@Toobzilla]

@@ouknow1446 as much as i disagree with the whole recipe, i gotta wonder, if the descent wasnt so rapid & the pressures were allowed to acclimate, does the titan make another successful dive?

[@ouknow1446]

@@Toobzilla No need to wonder. Why dare risk it? It's all or nothing. One crack and its done. What wasn't there before the dive is there afterwards who knows where?

[@mah6786]

Finally a well researched video that doesn't zero in on the game controller (which was probably the most reliable part of the sub). The truth is that composite construction is commonly used in modern subermersibles. But usually fiberglass instead of CF and rated to shallow depths with a factor of safety of 10+ for both crush pressure and fatigue life, for the very reasons mentioned in this video--this construction is very sensitive to defects and it's hard to both validate the design AND the process without a large sample size to build confidence. And you certainly don't use the sound of fibers snapping to decide it's time to go back up.

[@Belzediel]

Oh, indeed, I concur, on the controller. Baffling to me that something being cheap to purchase is most people's method of evaluating reliability, not the tens of millions of units tested to destruction. Plus, they can afford to keep a few spares in the boat, so even if one of them goes tits up there's others. Baffling. I'd also be fairly sure that Kemptown Racecourse knew any failure would be instantly catastrophic, and so any kind of safety feature in-dive would be a joke, the sound whatsit etc weren't anything more than a token gesture to calm the gullible, like having a 'main tank explosion' warning light on the shuttle. "And if the main tank explodes, mate, this little light goes red." "And then what do you do?" "Well, then we'll descend to the surface of the earth as a slightly pink mist, in a cloud of very expensive confetti."

[@gavinminion8515]

Okay, so I will take you up on the game controller - which had little to do with it's general reliability. The problem with using a game controller to operate titan was to do with failure mode analysis. When designing anything which is safety critical, one of the exercises performed is to identify modes of failure and possible outcomes (FMEA). There is no chance the designers of a game controller would have done any such analysis. They wouldn't have been concerned if a single component failure causes an issue as the worst case would be a player losing a game. Imagine therefore if, whilst manoeuvring a dry joint on the circuit board caused a button to jam and rammed the submersible into jagged metal wreckage. Sure they could have a spare controller lying around, but by that point it's not going to matter. Sure, the military also use game controllers, but I assure you if they ever intended to use them in life critical situations, they will do a full FMEA on it. From what I have read, there were a lot of other things wrong with this submersible which were much worse than the game controller, but it is a good example of how jerry rigged the whole show was so I don't blame folks for pointing it out.

[@josephoberlander]

@@gavinminion8515 That said, there is little to go wrong on the controllers. The main issue is operating in a marine environment. I worked as one of my first jobs as a repair tech and the computers we would get in in from people who lived next to the ocean was.. full of rust and other insanity. One actually had a hole through the motherboard due to condensation causing water to drip down for several months.

[@Belzediel]

​@@gavinminion8515OK, cool, interesting point. But... I'd be pretty damn certain the controller has a good idea what the odds are of button failure, and I'd be fairly certain they're low. Any controlling device, whether Sony or bespoke would carry such a risk, and Sony have data on hundreds of thousands of units, whereas if you build one for the Titan you have data on one. You don't actually know if the testing was done by Oceangate, you're assuming it wasn't. I'd agree but it is an assumption. The outcome of a failure is different, sure, one you lose Tekken, the other you explode, but that doesn't make any difference to the failure mode or the failure frequency, certainly the probability of a failure prone device doesn't kill anyone playing games, but it is going to be a serious threat to the survival of your business. You might not care AS MUCH, but there's a world of difference between caring about losing billions and flat out not giving a shit. Specific fail point issues seem pretty easy to resolve via software, if concern about a specific button or button emperilising the submersible, you only need one to say 'controller buggered, disregard until this button is pressed again' I take your point, I do, I just don't see why it'd be less safe to use a device with, by now, trillions of hours of fail state testing instead of building one unique device. It'd be one thing if the controller was being used outside the thing, but the inside of the Tube o Doom was, obviously, well within the normal operating environment. I mean, if the controller hasn't been tested whilst immersed in seawater, that doesn't really matter, because in the condition where it was, you have whole other issues far more pressing. Pun absolutely intended. What would be the Mean Probability of Failure figure that would be acceptable for this use? Because I'd be absolutely certain Sony exceed that value, and equally certain it would not be possible to generate such a number with a bespoke unit. In any case, it is at least very refreshing to natter about the thing with someone who has a reason for doing so that's better than 'it's a toy' so, thank you for taking the time to explain, it is appreciated :-)

[@gavinminion8515]

@@Belzediel Hi, thanks for the response. To be clear, using a controller that is produced and tested in the millions would 'likely' be more reliable than using a device you built yourself. However, that would not be the outcome of an FMEA investigation. If you were to look at this controller in failure mode terms, even though the chance of a particular failure (i.e. jammed button) is quite small, and the chance of it's effect (collision with debris) is smaller, the outcome (Loss of vessel with all souls) would be so great that you would do what many other manned submersibles (and surface vessels) do. You would have two control systems with redundancy and failsafe changeover. The instant that button jams, you would let go the first controller and pick up the second. You would not wait to change batteries or reprogram a wireless connection because those seconds might be critical. As an example, here is a quote from an old copy of the DNV rules on redundant propulsion systems: "The bridge propulsion control system shall be independent for each propulsion line; so that any single failure will only affect one of them, and that operation of the remaining system can continue on the normal means of operation (e.g. levers). Alternatively a system arranged with redundancy can be accepted if in addition independent back-up control system for each propulsion system is arranged. The redundant system must be so arranged that any single failure will not prevent continued normal control of the complete propulsion system. The independent back-up control system shall be based upon similar input devices as the normal means of operation (e.g. levers)." So to answer in brief - there is no mean probability of failure which would be acceptable - only redundancy with separation. Nothing I read about the game controller or any part of this vessel suggested they had the required redundancy - or had done the analysis which would have demonstrated where that redundancy was required. An assumption maybe, but one which I have yet to find evidence to disprove - unfortunately.

[@10191927]

Good analysis, another thing to point out here you didn’t mention. The carbon fiber tube(both models), were constructed in a warehouse, not a hermetic environment free from dust and other airborne particles that could’ve been introduced into the in between layers of the cabon fiber as it was being weaved. Also Ocean Gate removed a lot of their videos showing these construction processes(likely to hide evidence), and you can actually see air bubbles and imperfections in the layering process of the finished carbon fiber tube. Also a former engineer told Stockton to make the fiber tube at least 8 inches thick to ensure it was strong enough to withstand the ocean pressure at depth, Stockton went against this and it was only 5 inches thick. So I think imperfections in the tube hull combined with it not being thick enough as well as the flanges were weakening with each subsequent dive, and maybe water was beginning to ingress into the layers of the carbon fiber or finally penetrated the flanges and the glue and it was just enough to cause the catastrophic implosion. That’s my take on it anyways given what’s available.

[@JoeLinux2000]

I doubt any contamination was significant. Do you think leaves were blowing into the layup?

[@jamesn3513]

Very well done. As an engineer, I appreciate someone who has the knowledge to present this topic. Thank you.

[@salmonsoule3203]

It is all related to the repeated loading and unloading, this video is well done, those loud cracking during dives cannot be good health signs, if my guess is right, there was some leakage near the end bonds before this failure occurred?

[@defendermodsandtravels]

As another engineer I can say this video is pure speculation by someone with limited technical knowledge. No evidence to support his claims. You surely spotted the error he made on the ratio of hoop to axial stresses?

[@radpugguy]

I had not realized just how cramped it was on the inside, makes perfect sense. But somehow I was picturing something a bit less claustrophobic and horrible. Great video!

[@williamhaynes7089]

There are some videos taken by passengers you should watch.. its crazy tight inside for 5 people

[@shamancredible8632]

what a way to spend your final moments: surrounded by smelly dudes in a dark cold damp pressurized can.

[@northernskunkworks]

Rarely comment but as an experienced and qualified engineer this is the best video on this event by far. Clearly there isn’t anything inherently incorrect in using composites for this application and fascinating that you deduce the axial crinkles in the carbon fibres the likely failure mode and source of the repeated noises in the run up to catastrophic failure.

[@Sidowse]

You can't push fibres!

[@niallvbrennan6629]

A thorough, detailed and plausible explanation,Mike. Kudos to you. As an engineer with limited experience of CFRP, one issue has always concerned me: ongoing inspection of multi-use CFRP structures. It is, I believe more difficult to detect for an accumulation of voids, cracks and fibre alignment issues in CFRP over time, particularly for a substantial structure such as Titan's hull. As you pointed out, it is quite possible that the axial fibre integrity was compromised gradually over repeated dives. CFRP can certainly withstand significant compressive stresses, if well designed and fabricated. However, it appears to me that it is difficult to detect the build up of material issues which could undermine the integrity of the original structure. Perhaps much more attention should have been paid to this issue by OceanGate. I wonder if this will be one of the findings from the ongoing investigation. Thanks again for a wonderfully presented explanation.

[@grahamfoulkes7321]

Working on the development of carbon fibre wide chord aero engine fan blades back in the late 60's, I have some knowledge of the processes and characteristics associated with CF. The development program for the fan blades was the result of the need for a light weight structure, capable of resisting the centrifugal forces on the blade at the tip, as well as absorbing the torquing stresses due to loading. Carbon fibre composite was the only material that met those criteria at the time. unfortunately, it failed the blade impact test, also known as the bird strike test, as mandated by the USA FAA, a nine pound bird fired into the engine running at full throttle, (it passed the UK CAA bird strike test using a seven pound bird). The carbon fibre delaminated, shredded! Years later, General Electric in the US adopted CF for the engines supplied to Boeing on the 777. They experienced the same problem, delamination until they came up with a design which involved three dimensional weaving, with the lay up having cross filaments incorporated in the weave specifically to prevent the delamination, apparently a sixteen hour layup cycle! If the Titan CF centre section had been constructed on the same lines, maybe this could have resulted in a structure capable of withstanding the enormous external pressure. BTW, I dispute carbon fibre composite has good compressional strength, a function of the matrix that binds it together, glue.

[@superfly3990]

😊 Obviously the Engineering wasn't at all sound. A hideous design that wasn't structurally tested. The Carbon Composite cylinder was too long resulting in a deflection near the mid section. The wrapped strands without any overlap with the Titanium Bulkheads was another design flaw. Using this fiber material in any type of loading other than Tension is Idiotic. Throw the potential for an undetected craftsmanship error and you have really Big Trouble. And one more thing, especially for you Carbon Composite Experts, this is similar to Fiberglass for everyone to understand. This isn't all that special. I'll bet you that there won't be another composite submarine any time soon ! One more thing, military submarines have really nice hulls, but they don't go deeper than 2000 feet. Think about that. Titanic is at 12,500 feet.

[@barenekid9695]

Ahhh.. as in the infamous RR engines.... that Pilots universally Hate as they can't fully trust them??

[@bschwand]

do you have any video of the 3 dimensional fiber weaving ? I can not imagine what it could look like. Would be very interesting.

[@josephoberlander]

@@superfly3990 It's not necessarily idiotic as CF has a compression strength of roughly 650 Mpa. But titanium alloys that are over 1000 are easy to obtain. Even some steel alloys can exceed this. The issue is weight. But weight isn't really a huge concern for operating underwater. Using an alloy would have been dead simple and done. Of course, leaving many other issues to deal with.

[@BrokeWrench]

Exactly! Compression strength is good pound for pound but CF's real strength is that the carbon strands absolutely refuse to stretch, but the resin is most of the comprehensive strength. Plastic isnt Exactly known for its compressive strength

[@uuzd4s]

A couple of things, while this Carbon Fiber pressure vessel was being testing out in the Bahamas one day, it was struck by Lightning at least once. Pre-preg Carbon Fiber holds up VERY POORLY to Lightning Strikes as it usually causes serious Delamination's. Unless OceanGate incorporated some proper and well-placed bonding to the entire assembly, and within the CF material itself, there was likely Damages caused by that strike. Second, Anytime that you're bonding dissimilar materials with Epoxy, like Carbon Fiber to Titanium, you must be absolutely certain there are NO oils or other contaminants on either surface before bonding. Watch the released video of the OceanGate submersible assembly where the technician is wiping a Titanium mating ring w/ a rag (presumably with some acetone) and then handling that same area with his ungloved other hand ? ? ? Any good NDT Technician (non-destructive testing), or proper X-Ray composite viewer could have found any imperfections, delam's, distortions or defects within the materials used. It's Insane that they fired the manager who pushed for those NDT checks and they drove on so blindly without that assurance. Edited for spelling and Lightning Strike location.

[@mytmousemalibu]

Those titanium end rings had very little flange on them too. With water pressure trying to squeeze this thing into an hourglass, that also struck me as a very poor design decision. Atmospheric layup with expired pre-preg? I can't imagine how many defects that thing had in it. The biggest defect was Rush.

[@uuzd4s]

@@mytmousemalibu Yea, Rush seemed too "over the top" in some aspects, rebellious to ideas that weren't his own at times and behaved like that Salesman who will tell you what you need or want at times. He also had hiring policies that attracted those who were OK w/ stepping outside of normal engineering & maintenance procedures. I worked in a small R&D group in Seattle in the 80's thru 90's, not far from where these guys were. We were reinventing some very antiquated, 30's vintage, Seafood Processing machines. The Owner/Head of the Co was Genius, happened to be Greek, and was Way out there with his mindset & approach towards how he viewed most things when compared to what most would see. That trend, of operating outside of the norms, turns out to be what most Genius minds have in common. High Intelligence in people can be very appealing or attractive w/ the "WoW factor" associated with it. It can also border on weird or even dangerous. Rush had some of those qualities that a Genius might possess but he was also closed minded to ideas that weren't his own. Genius Good, Self centered Bad is my take on the guy. It's just sad how his talents combined w/ his short-sightedness led to the death of others.

[@nadapenny8592]

Why why why why why WHY was no non destructive inspection done??? WHY WHY WHY

[@jonf2009]

​@@nadapenny8592because he wanted to be the McDonald's mass producer of subs. Destructive testing would cost money he didn't have and his company was bleeding red ink as is. Sadly this self assurance of the flawed computer models coupled with his need to succeed caused his death.

[@uuzd4s]

@@nadapenny8592 Yea, you can be sure that question will be brought up in the courts. Just as Bizarre were Rush's hiring practices. He intentionally went for new graduate students who were willing to step outside of proven engineering norms and experiment. The Manager who pushed for more thorough testing represented industry standards that Oceangate intentionally avoided. You could almost hear the Attorney's clamoring to represent those lost souls who were victim to Oceangate's methods. The experimental status that this submersible was allowed to operate under may not have regulatory oversight and that needs to change.

[@josephstevano5905]

I don't know if KZbin gives out awards but, if it does, this video deserves to be nominated: 1) the graphics are amazing and 2) the narration is superb (both the narrator's voice as well as the content). Thank you for a tremendous video.

[@Mike-Bell]

Wow, thank you! 🤩 I appreciate the comment.

[@edkiely2712]

Appreciate the time and effort put into this presentation! The gradual, patient, and detailed layout of the discussion, with the intricate graphics and comprehensive editing, truly allows for better insight into the whole process behind the making of the Titan submersible.

[@Mike-Bell]

I'm glad it was helpful!

[@TheRealRobG]

The fact that the flanges at the end failed outwards is a clue to the failure mode of the pressure vessel. I don't agree that it would shatter uniformly like glass. The more likely initial failure is that one part of the cylinder became weaker than the rest and was forced towards the centre by the pressure - this compression on one side would (like if you were crushing a toilet roll) force other sections of the cylinder outwards for a fraction of time before complete failure occurs. That's what ripped the flange apart.

[@tbrowniscool]

I agree it would not act like glass as it is not glass! That flange blew outwards and the pressure was equalised instantly inside.

[@ruk2023--]

You need to listen more. This is why so many half truths are floating around. Because people hear what they want to here. The narrator said that CF fails suddenly like glass does. He didn't say it was glass or that it fractured in the same way. He simply said that it fails without warning which is a property shared with glass.@@tbrowniscool - there is plenty of information on Google as well about how CF shatters into lots of pieces under extreme pressure.

[@Aaron-zu3xn]

the can of pringles doesn't need to completely shatter for the cap to pop off. this thing was doomed from the moment it was glued together it didn't matter how strong the CF or titanium are the difference between the two creates a gap and that's all the water needs even a pinhole and this thing will tear itself apart at that joint

[@WoodysAR]

Yeah all that FIBER Just shattering,? This whole video was incorrect. The flangers were blown out at 1 end. Which just says that the other end was the failure.. And the end with the flash is pushed out is where the air had to go... (the other seam between different materials) ... One failed as an implosion then the other failed is an explosion. Without knowing whether or not the end that has the flange is pushed outward is the front of the back... I would bet that it's the front because they were hearing noises in the back.. That's where the failure happened, Then it pushed the Port hole glass and the flanges out of the front. They must have been Spaghettified instantly when it actually failed. The fact that stockton mentioned the sphincter shrinking noises with the first hull... Leads me to believe the transcript is correct, That as the layers of Carbon fiber were being infiltrated with water and compressed that it failed progressively ...up until a point, after which it was instantaneous. The opposite of a Jack in the Box.

[@WoodysAR]

​@tbrowniscool LOL... The flange just blew outward? Lol.. (no offense,. But that is funny.) Clearly it blew OUT because the other end blew IN! One end failed imploding, the air had to go somewhere, ... It blasted out the other end! Like a Coup/Contrecoup pattern in Titanium! ❤😊😊

[@Rafa_guitars]

The acoustic monitoring system did work but they ignored the sings. There was a loud bang the previous dive

[@cameltrophy3]

Your videos are always awesome. It was reported that the US Coast Guard has recovered the aft titanium dome and other parts of Titan, not previously recovered at the time of the incident.

[@Mike-Bell]

@cameltrophy3 Yes, the reports on the recovery of the aft pressure dome came out just after I posted my video. It's a pity I couldn't include that in my video.

[@Tinman97301]

What has happened will set the carbon composite science back decades. Now any time someone brings up using them in any safety capacity this will het talked about and not tried. Proper testing is sooooo important.

[@Bristolcentaurus]

not sure about that, cf is embedded in industry its a 'niche' product its uses are well known and growing all rush has done is to show that his configuration is one to avoid

[@pingwingugu5]

Very interesting video. I like your take on this subject. 13:28 Yes titanium and carbon are bonded in aviation, but aviation is not a good analog for deep see usage. Carbon fibre composites compress much more than titanium. The haul would simply shrunk way way more that titanium faring under the deep see pressure. That isn't as big of a problem in aviation, where pressure differences are magnitudes smaller. This was a crucial potential failure point, but there was no proper examination or testing of this bond. Not to mention that they didn't even glue it in a proper clean and temperature controlled environment. Comparing Titan haul to an airplane wing is also not the best. Those wings are baked under pressure in autoclaves during the drying stage, which reduces the chance of any dry spots, bubbles and other imperfections. They are also thin enough that they can be properly examined (x-rayed) and tested. Nothing like that was done for Titan. I like your theory about axial fibbers, it's another example of how many corners did they cut and how botched the whole build was. I agree with your conclusions. Could you build a carbon fiber haul for submarine? Probably, but you need to go above and beyond with research, quality control and testing. Those guys didn't do you it, they were only interested in cutting costs.

[@scottperry9581]

This contained some information I had not seen before. Thanks.

[@wamingo]

Had me think it was the scrubber that was the culprit for a while there.

[@Mike-Bell]

😂

[@itoibo4208]

lol me too. I think the designer got that tote at a dollar store.

[@PartanBree]

This is really interesting, thanks. I still feel that, given the extremely tight requirements for the layup, "composite isn't suitable for this" is still a reasonable simplification of the facts. I can certainly understand the classification societies' reluctance to assess it, because the actual strength depends so much on the tiny details of the layup, which would be very difficult to verify unless the surveyor is present for the entire layup process. One place I disagreed with you is that I don't feel a safety factor of 2.6 is all that generous. I would default to 3 for applications far less hazardous than this. We will all be really interested to see the results of the investigation.

[@zemm9003]

Carbon fiber for those who don't know is essentially a rope. Think about the cables that hold some bridges, they are designed in a way that their tensile strength is much higher than their compression strength, the material is so strong that it could sustain strong compressive forces but only at a fraction of what they can support went tensed. Carbon fiber is by its design meant to be extremely impressive when tensed but it can only hold a fraction when compressed. Steel hulls are extremely strong under compression when using basic geometric shapes like a cylinder. To be an innovative application of carbon fiber one would have to understand how to weave it in a certain pattern and calculate a certain geometry for the submersible so that under uniform pressure the carbon fiber would have to extend in order to keep everything in place instead of contracting. This is admitting such a solution even exists. The other option would be to brute force the problem by creating such a thick and dense carbon fiber hull that even if the compression limit is only 10% of the extension limit it would still be enough to easily go back down to 5km and come back up. I am not even going into more technical details such as computer modeling. It is extremely easy to model the behavior of a cylindrical uniform Steel or Titanium hull (so much so that a noob could do it) whereas it is extremely complex to model a material composed of two or more due to the non linearity of the partial differential equations which results in bad behavior of the numerical solutions that your software will generate.

[@Mike-Bell]

Be careful getting your technical explanation of carbon fibre from James Cameron 😂

[@PungiFungi]

It appears carbon fiber maybe useful for submersibles for shallow dives...but not for trips to the TItanic or to the Mariana Trench.

[@zviratko]

Rope is a wrong analogy as rope is itself made from strands to be flexible in many directions, those are strips. For a better analogy try folding paper more than 7 times over ;-)

[@scroopynooperz9051]

So this is why he was supposed to test the design. He could have done a couple of test dives to increasingly deeper depths - say start with a depth to 1km first, then ultrasound the hull and check the structural implications. If all is OK, he could gradually increase the dive depth, rinse and repeat until there is confidence in achieving the required depth. That's the least he could have done for passengers. Instead, he was a cavalier cowboy with delusions of grandeur.

[@Mike-tu7uw]

😂Yeah that sounds great but unfortunately all the real experts who do submersibles for a living say carbon fiber isn’t suitable for deep submersibles

[@genius1a]

This was a very reasonable overview of the craft, with great insights on possible weak points. The craft itself was working astounding 15 times, but as you pointed out - we (and them neither) had a clue, of what the safety margins were , and how much role material fatigue played in the catastrophic accident. That ist really unfortunate, because the idea itself still looks pretty promising - even from a technical standpoint! Thank you for carefully pointing out how a responsible path to such a submersible could look like.

[@lukeamato2348]

It didnt work well 15 times lmao. The use of the carbon was wrong

[@lukeamato2348]

The thing had cracks you could hear happening. It was weaking 15 times

[@genius1a]

@@lukeamato2348 The first Jet airliner type "De Haviland Comet" used riveted Aluminium wrong. It killed around 100 people before the FAA finally revoked the flight permisssion. After that, they did a proper investigation and found out about the extremely rapid fatigue due to the pressurized cabin stress on the metal. They changed little things on the manufacturing process on that type (and the window shape, but that wasn't the origin of the cracks), and used several new built ones for the UK military as survey planes up to 2011. So while the manufacturing had catastrophic flaws, the overall idea and construction of the plane type was fine. Alas, Passengers would have refused to use it due to its record and it had gotten too small anyways, compared to the competition. So it never went back into passenger service on scale. This video shows the possibility of similar causes for another new material and manufacturing process, that could have led to the catastrophy. Maybe it could easily have been avoided - but we know too little if that was the cause. Concluding by what we know so far, that this idea of high pressure vessel construction is completely wrong from a material scinece standpoint, seems a bit premature and amateurish to me.

[@captainwin6333]

They had to rebuild it. One worked 6 times, the other 7, well 6.

[@pyropulseIXXI]

It doesn't look promising at all; homogenous materials can undergo tens of thousands of stress/no-stress cycles

[@johnwright291]

I used to haul gravel on barges. When he said that the round port hole had 2700 tons pressure on it I imeaditly thought of a barge loaded with that weight. It would fill the deck area 15 feet high on a barge that is about 180 feet by 45 feet wide. That puts it in perspective.

[@Toobzilla]

when i heard that the port hole was affixed from the outside only & that to get out there needed to be supporting crew?.. i knew then that maverick engineering was not going to be applied.. that was a simple correction & if that highly plausible life ender wasnt corrected?!?!..

[@zviratko]

Wow. Actually not a clickbait video like all the others. Thank you. I wonder, though, is carbon fiber really that strong in compression? I failed to find much about it (maybe because the opposite notion is trending so much). I am not an engineer, but I handled carbon fiber strips and composites, and based on that I would never imagine it being strong under compression. At most it would be good at keeping the epoxy in check and not deforming, but in reality it would be under tension (inward) and just keeping the geometry consistent enough to withstand the pressure. How much weight of the hull was CF and how much was the epoxy bonding? I guess epoxy made the bulk of the real strength, or am I completely wrong? In either case, any delamination (like the endcaps pushing on the end of the carbon fiber strands and pushing them apart) would spell disaster, once you compromise the intended geometry the whole strength is just gone, so hearing any kind of crackling should warrant immediate testing of the hull.

[@fuglbird]

@zviratko Take a look again. I've found several scientific papers with measured compression strength of carbon fiber composites. I've seen values between 20 % and 60 % of the tensile strength and airasj1 has experience higher values in his work. The compression strength is highly dependent of how the specimens are made.

[@josephoberlander]

@@fuglbird And that's the issue. Based on what we saw, I'd gather closer to 20% at the joint due to the fibers not being under tension. Add in even from the videos that we did have, obvious bubbles in the epoxy and a fairly dirty environment (definitely not a clean room), certainly not anywhere near the 60% end of the scale. Metal alloys, on the other hand are almost idiot-proof as you simply order a tube to be made, like they did with the end caps, and are done. Decades of testing already done on the alloys and one factor removed from the design's (rather large) list of worries.

[@tonamg53]

This is the best KZbin video on the Titan. No drama, just pure facts and very detailed as well. 10/10 I just want to add more on the “Real time monitoring system” Assuming the leaked transcript is real… The system actually seems to work as intended. It first sounded alarm at [09:28:16] and the last message from Titan wasn’t until [09:46:37] So that would’ve give them about 20 minutes or more to react… which should be more than enough to initiate emergency ascend procedure. but then 2 minutes after the alarm sounded, a message from Titan reads “no change with thrust the *rate of descent is increasing* At 35. Going to release the ballast now.” The only logical explanation I can think of is that the Titan had somehow, gained some weight… which strongly suggests that the water was leaking inside the hull between layers of the carbon fibre. So the process in which the hull failed does not seem to be immediate but took place over 20 minutes until it gave up and imploded. If not that, then Titan was most likely attacked by a giant squid which cling on to the hull (activating the alarm and increasing the rate of descent) and after 20 minutes of tentacle handling… finally crushed the hull into pieces. Again, this is based on if the leaked transcript is real. So far, I can’t proved that it is real, but I also can’t proved that it isn’t either. Note that the content of the leaked transcript all seems to check out with the available evidence. Also, both the authorities and Ocean Gate have not come out to denied the leaked transcript either… so most likely it is legit.

[@umbreonpokemon8190]

Lol giant squid? What drugs are you on pal? Then you conveniently say you can't prove if your theory is right or wrong. Oceangate is keeping their mouth shut as they should while this investigation plays out. It does them no justice to entertain that stupid TikTok video and make a statement about it.

[@zach446]

"most likely attacked by giant squid" lmao the Internet never ceases to amaze me

[@tonamg53]

@@zach446 I know it’s funny right… even funnier when you realised that it is actually an entirely plausible scenario given how little we know about these deep sea creature. Only 2 videos of these creature in its natural habitat had ever been recorded. One thing we know is that it does attacked whale and shark… basically about the same size as Titan submersible.

[@moonasha]

"giant squid" lmao

[@tonamg53]

@@moonasha Unlikely but still entirely possible though 🤷🏻‍♂️ Also worth noting that Giant Squid has been confirmed to be an aggressive hunter. So it will proactively hunt down and aggressively attack whatever it is preying upon. It might be worth noting as potential risk going forward and avoid designing a submersible in the shape of a sperm whale…

[@qdusen]

BTW, 20mm is not 3-1/4" (aka 3.25") as shown in the graphic for acrylic compression. 20mm is around 3/4" (aka 0.75").

[@machendave]

He did not want ultrasound testing on the hull.

[@enhancedphysique6452]

To much money for one 2 he knew the second they saw it was junk expired carbon fiber, the test stops right then an he fails

[@drizler]

What could possibly be wrong with that. It sounds so typical of the attitude of being “ smarter than everyone else”. It’s suicidal in itself but when you take paying passengers along it’s pure criminal!

[@adarkmattercloud]

Just in his add

[@nutsackmania]

a hospital just blew up in gaza but this is what youre freaking out about

[@jonm7272]

​@@nutsackmaniaare you going to post that comment on every single video comment section on the whole of KZbin? Yeh, a bunch of people got killed in yet another war in the middle east, very sad, but if we only ever talk about people killing each other in the middle east we'd have done nothing else for the last 2000 years. Go shout about it on a video that's actually focusing on the war in Gaza, this one is about composite engineering.

[@motolifts]

Excellent video! Really appreciate the time you took to put this together. Did graduate level courses on composite materials in the process of getting my masters in ME. After this happened and the video was circulated of the team gluing the titanium end rings on in what looked like vacant warehouse it blew my mind that it survived 15 dives. Everything we created in my labs was done in a clean room type environment and that was something just for testing not to support and keep lives safe. They didn’t have on respirators, eye protection, even using clean rags and wearing gloves to keep hand oil off the bonding surfaces and out of the epoxy mix was apparently too difficult. While I agree with your analysis on how the sub failed and highly doubt it was the titanium to carbon fiber surface, this video just showed the overall lazy approach to working with a composite that even someone making a car hood or bumper would have had a basic level of understanding on and had avoided. With all of the failures that occurred during manufacturing and design I would argue that it proved carbon fiber as being a suitable material for submarine use.

[@Mike-Bell]

The video of the gluing was of the first hull. I couldn’t find video of them bonding the second one but it seems second time things were done more professionally. Nevertheless the general attitude seemed rather blasé.

[@koriko88]

The video starts out by suggesting that carbon fiber is just fine in this application, but then at 10:40 begins to explain why carbon fiber is the wrong material to be using for this application. Only on paper does carbon fiber work well, in that it has the theoretical strength to do the job, but in practice if there are any tiny mistakes or it isn't done to the tightest possible tolerances, it is unforgiving and will kill you before you know what happened. Further, the references to aircraft are irrelevant - submersibles must handle much higher pressures and stress.

[@SuperLordHawHaw]

One basic thing about the whole sub business concept is people subjecting themselves to such an extreme risk just to take cell phone pics through a porthole. It isn't like climbing or scuba diving where you are intimately connected to the journey and process. Here you are just sitting and totally passive and then you glance out a window. There really is not much difference in the end than if they'd had just stayed on the surface and operated a robotic sub and taken pics that way. Maybe they could've done it while being bolted into a cold tube lol One thing people starting new businesses like this share is an almost blind self-confidence. You really need to be insanely cocky to not be cowed by all of the risk and not scared of failure. Unfortunately this self-confidence bled over into the engineering and safety aspects of the sub.

[@Mike-Bell]

I couldn’t agree with you more. But as a designer I do admire the design process and trying to turn idea into reality. And I really admire those who with endless dedication and hard-work make reliable and dependable things useful to society. A sub for the uber wealthy to get their dopamine rush does not satisfy my definition of useful to society. I’m really hoping someone on the inside gives me some new information on this story…. I can’t help being fascinated by it all.

[@itoibo4208]

That is kind of like saying going into space is stupid because all you get to do is stare through a window. I think knowing the water around you could kill you in a split second will add to your feelings of being on adventure that you cannot get from a remote view, not to mention the cold, and any other effects you might feel. If you wore a pressure suit, you would just be in a much smaller submarine, really, albeit one that lets you interact more with the environment. Still, what would you do at the titanic? You probably should not touch anything if you want to keep it as a preserved site.

[@Mike-Bell]

@@itoibo4208 They are entirely different. Going to space was for furthering science and exploration. Going to the Titanic is only for the entertainment of the uber wealthy and to give them bragging rights.

[@SuperLordHawHaw]

@@itoibo4208Going into space is more than just sightseeing though. You are encased against a hostile environment for a bigger purpose.

[@vanderlinde4you]

There is nothing else in regards of going that deep to see the Titanic. The titanic won't be there in 20 to 50 years since salty water is chewing up that boat at the bottom. There's nothing wrong with a deep sea dive - but it has to be solid, safe and rated to dive to such depths. The pressure down there is huge.

[@dannyboyy31]

This is the first time I've watched one of your videos. I thought it was really interesting and well produced, avoiding all the speculation and just looking at the bare facts (and even questioning the mighty Real Engineering channel!). Subscribed 👍

[@Mike-Bell]

Welcome aboard!

[@DinkyDoughnut]

That was a BriLliant ExpLanatory view on the Ocean Gate failings.! Thank You and I look forward to your next findings.! ❤

[@kukipett]

Ah ! finally we have someone who explains what happened. This is exactly what i explained to my friends as i work with carbon fiber since more than 20 years in racing car applications. The big problem come from the end caps, applying 5-6 times the pressure on the tube ends because of geometry, so after a while and many pressure variations the tube end got some wear coming from the resin aging through the process and the fiber becoming slighly wrinkled as you explained. So cracks start to form and one day you have a sudden major failure .

[@SteadySteve1024]

By far the best explanation of what really happened. Thank you for taking the time and patience to put it all together.

[@Mike-Bell]

Thanks 😊

[@halomultiplayermoments]

Agreed, excellent video. Balanced view.

[@thomassutrina7469]

I have written this multiple times. The composite hull tube gained weight due to water entering cracks between the fiber and the epoxy. That is obvious, the faster then normal descent rate is due to not taking into account the water in the composite tube. The other affect of cracks is changing the diameter average where dept pressure is applied. The radial stress at diameters greater then the dept pressure diameter is tension instead of compression. This further increases the rate of crack propagation. Failure didn't have to happen. This cracking problem is well known in composite pressure vessels. The solution is simply to put a barrier that prevents water from contacting the composite cylinder. It needs to not be permeable for water at depth pressure. A plastic or rubber is the likely choice, however; metal would also work. The pressure would cause this thin cylinder to compress, reduce diameter, until it contacted the composite cylinder.

[@medstudent639]

The fact remains even the most exceptionally well crafted carbon composite hull cannot be inspected properly after each dive for structural integrity. There's no such issue with titanium pressure hulls.

[@TheGamersRace]

And I like how he brings up the carbon composite compressive strength, and then immediately debunks it with the exact reason it's not suitable for this application.

[@dwh5512]

Thanks for a comprehensive and accurate depiction of the flaws built into this vessel. When carbon fiber first came out, we (who worked in composits) were all taught that the 60/30 angle of layup would provide a vastly superior strength. When I first stated seeing similar reports on the tragedy, I figured it had to be a massive error in the laying up of the fiber. You illustrate this perfectly. I also thought his warning system had to be little more than wishful thinking. Lastly, I'm stunned he never utilized NDT like ultra sound. This was a programmed accident. Pride & confidence are not equal to good old-fashioned NDT & destructive testing. Thanks for such a good report. I subscribed. 👍🏻

[@Mike-Bell]

Welcome aboard. I agree. The acoustic early warning system was a marketing gimmick and self-hoodwinkery and self-delusion by Mr Rush

[@timothybrophy4188]

This sub was built on the cheap with arrogance sprinkled in by Rush . Titanium and carbon fiber are two materials with different compression along with the glue .There was already known science for building a safe submersible.

[@Jorge.ALXNDR]

I actually thought this was going to be one more of the videos I've seen about the topic with the same information, but I was really surprised to see how much more detailed and scientificly explained the whole incident was. I subscribed in the first minutes.

[@Mike-Bell]

Thanks. More to come!!

[@JoeLinux2000]

Yes, it's a very well done video.

[@denniss3980]

This sub suffered from multiple systems failures in 80% of its dive attempts, and none of those had anything to do with the CF or game controller, I would love to see a follow up video on these failures

[@gingernutpreacher]

I thought one of them was and they got away with a software update middive

[@prestonburton8504]

very true -

[@pyropulseIXXI]

So the CF hull making loud noises isn't a concern at all? I don't get why you people are trying to defend composite materials when it was very obviously the cause of failure.

[@prestonburton8504]

because, like airframes -it gets better. Boeing had nasa to help- @@pyropulseIXXI

[@itoibo4208]

@@pyropulseIXXI the material could be fine, but you have to remember that designs have trade-offs. This is nore likely a failure caused by some of these design goals, and not the material. Subs all make noises, as far as I know, but a carbon fiber one should probably not be making sounds like a gunshot, at least not after the first dive or two.

[@dennyliegerot4021]

When this happened the first thought that came to mind was the difference in material compression between titanium and carbon composite. Primarily as how it would effect the glue joints and internal/external flanges where the 3 materials come together to form a bond/seal. The other thing is how thin and short the flanges were in comparison to the thickness of the material they were binding...

[@jeffreyrudolph5061]

The splitting (flanges) in & outwards, seems to suggest a force of fragmentation ?

[@Toobzilla]

the flanges were fully intact upon offloading the salvage.

[@christhorney]

their are a few things in this vid that i have slight issues with, seeing the outter flange hanging after the thing has been salvaged from the bottom of the ocean, stuck on a ship and then unloaded at a port, and you see the flange hanging down and assume it got blown outwards? perhaps it got sheerd inwards while attached to the carbon then its weight and the salvage process makes it look now like its hanging outside, doesnt mean it got blown outwards. also something i still dont see anyone mention is the fact that the glue bonding the cylinder to the titanium flange had to not only take the stress of the dissimilar materials incomtatable compression properties each cycle, but the amount of hours they spent with the door hanging open in rough seas troubleshooting the long list of issues, the amount of missions that got scrubbed, each time with the door spending hours open with all that uneven force from that heavy ass door hanging from one side must have been putting serious load and fatuige on the bond that it just wouldnt deal with well like it would all the other loads its subjected to, i truly beleive its that hindge and hemisphere being swung open and kept open far too often that caused the most stress and fatuige on the bonding surface that it just does not look to me like it was designed with that load in mind, yes its got a well engeneered joint structure to put up with the stress of dives, where its all evenly compressed and both hemispheres are basically pressed inwards onto the bond while diving, but its got a sheering, twisting, peeling load put on it from the door

[@dzzzzbutube]

Those flanges look like a good thing to look at further to me. They are quite thin if you consider what the axial forces are doing to the cf tube. Could it be that the cf tube was being compressed to such a degree that there was high load being placed sideways on those flanges? The animation did not show a radius at the bottom of the flange recess so I wonder if there could be some progressive cracking showing up in the flange breaks, note the inner flange was shown to be broken too.

[@christhorney]

@@dzzzzbutube its very possible, but i think its more probable the forces involved are so insane

[@michaelalldritt7649]

i think you are are right, maybe an internal metal skeleton to support the weight of the doors and not put twisting forces on the carbon fiber when they were left open

[@danieldupuys2002]

The flanges and titanium end caps are blown outward, the bolts between them are blown, and the window also. Big explosion (just after implosion) like a diesel.

[@barrymayson2492]

The flange could be peeled open due to a failure of the CF tube as when it collapsed it would natural bend in the middle but push out at the ends and hence push the flange outward. Also as it failed the end domes would be pushing inward and would also push the flange out when the collapse started. In it self I don't think it was a problem with the flange but the CF and glue used, in my opinion. I await the report but it may never be fully disclosed as it's such a contentious subject already. It is sad when people die but the the correct testing could of saved them and may have improved the design to a point it could be usable tech.

[@Jath2112]

I...can't help but feel anxiety just imagining sitting inside this thing while they bolt it shut. Fascinating video here, thanks for taking the time to do such a detailed breakdown. ... ugh... my word choice feels...off.

[@dextermorgan1]

Me either. You'd never get me in that thing.

[@prestonburton8504]

amazing - yes. but no matter what - always trust in God.

[@rvarsigfusson6163]

@@prestonburton8504 trust your self...... trust in God is insanity

[@jamesm5787]

Yeah, there's a damn good reason why certified submersibles have a hatch on top, openable from both sides. If something goes wrong, they can open the hatch on the surface, without outside help.

[@prestonburton8504]

just like our defense subs, right? certified to 300ft (the test depth is classified) they have no openings - neither forward or aft, on on the sides. yep, just looked back. you are right. @@jamesm5787

[@joeb465]

HMM, Stockton Rush said he took it to 4000 meters and it made a lot of noise which is a VERY sphincter tightening experience

[@stevemolina8801]

I ran across this on my feed and found this extremely interesting and well done, Great work!

[@Mike-Bell]

Glad to hear that 👌🏻

[@flomojo2u]

I really appreciate the thoughtful, rational way you explained this. I'm so sick of armchair experts who have no experience whatsoever in the design and construction of such a unique vessel. SR obviously made some literally fatal mistakes in how he treated risk and testing, but there's no reason that some company/institution couldn't spend the time and money to properly test and overspec such a craft successfully. He really was blind to the risks, or at least chose to ignore enormous issues with the whole design and build process, skimping on testing and lacking a willingness to seek outside expert advice and admit he needed such help. It would be amazing to see someone do it right and open up more of the ocean's depths and mysteries to people who ordinarily would have as much chance of experiencing such environments as the average person would to stepping foot on the moon.

[@perwestermark8920]

But many "airmchair experts" are experts. And all strength formulas depends on there being zero delamination. Because a normal rope is enough to show delamination isn't an issue for tensile strength. But a huge issue for compressive strength. And no one has yet shown *existing* manufacturing able to properly solving the delamination issues for this usage case. Which makes lots of "armchair experts" correct. It's irrelevant what the theoretical compressive strength is, when you can't actually build a hull to that level.

[@barenekid9695]

Reality being the Man built an Amusement park ride. No more.. No less Cost cutting was endemic.

[@Bristolcentaurus]

and add to that the problems of the cf/metal joint it is possible to design and build a better joint at greater cost, but there comes a point were the fatigue life deems the hull unsafe in any event and you have to make another, is the cost of making replacements in c/f cheaper or more expensive then an all titanium or steel hull in the first place@@perwestermark8920

[@hotcakesism]

The author of this video is an aerospace engineer, not a naval engineer. AEs do work on submarine design but that's no reason alone to take his statements on authority.

[@troppoandante]

The conjecture regarding waviness in the longitudinal fibers sounds plausible to me. There is a very well documented case in which this was the failure mode. DG-300 gliders were manufactured in Germany for years with no issues. Production was later subcontracted to a foreign company that neglected to follow proper procedure in laying up the wing spar carbon strands. This manufacturing error introduced a slight waviness in the fibers at the wing roots that resulted in a fatal accident and the grounding of all the fleet.

[@Timba-w7f]

Just looking at the interior photos gives me the creeps. I wouldn't have gotten locked in that thing on dry dock if they paid me $250,000.

[@The68lespaul]

I think id have to consider climbing in it at dry dock for Half a Billion , not a penny less, no trick,s lol, oh, the clock starts the moment my last foot leaves the ground, then as soon as the clock strikes 3-minutes, Done, im back out, with my half a Billion in hand, on my way to the airport !! its been real,Fun, nice seeing everyone, gotta go, W/H/W 10/11/23

[@jsax01001010]

Fantastic video! This is the most comprehensive and detailed description and model of how the submersible was constructed that I've seen so far. Also, this is the first time I've seen that video clip of the carbon fiber being laid axially.

[@JoeLinux2000]

Yes, it's one of the most informative videos on the subject, and many of the comments are better too.

[@TylerMeyers0070]

Not getting on a sub with Mike, he didn’t learn the lesson about carbon fiber… The carbon fiber used was a fabric but what is holding that fabric rigid? It’s a resin, the only thing holding the layers of fabric together is that resin. Even under tension the resin will break down which is why the Boeing 787’s fuselage has a life cycle of 44,000 pressurized flights. Everyone who previously went on the sub discussed vary loud cracking sounds, which is a clear sign of delamination between the layers of fabric. If the sub had gone down and stayed down, it would probably still be intact. The issue is going down and coming back up, essentially the equivalent of a flight cycle. Each time it compresses and contracts, the cracks are getting bigger, and more frequent. Rush knew this but still neglected to do an x-ray because he knew it would be the end of Ocean gate, why not go out with a bag. Congratulations Rush you made it into history, I’m sure you’ll be in lots of engineering textbooks for decades to come.

[@vanderlinde4you]

Good point - i assume they calculated that the titan would be capable of doing a couple of dives which it did and reached over 4km deep. But this time the last dive was completely imploded.

[@ak983625]

As an engineer and once scuba diver, I’ve always had issue with MSM assumptions about this loss. Starting with nonstop criticism of wireless game controllers. Any and all propulsion controllers need robust design and redundancy, no matter the specifics of their design. These controllers may have been perfect for the application. MSM automatically demonized this. As for carbon, its simply not just the material. Its was likely the lack of truly thorough testing and finite element analysis, destructive testing, ultrasound and independent third party testing and review. Not simply the “carbon”.

[@itoibo4208]

Yes. and I also wonder why all the hate on the controller. It worked fine? needs no wires through the hull. seems like a good idea.

[@brandononishenko2841]

@@itoibo4208plus, a reliable technology that has been in use for decades

[@theontologist]

Only the most shallow media focused on the game controller. Most tried to refute the mania and focus on the depth rating (or lack thereof) of the CF and viewport.

[@jooch_exe]

This is by far the best 3D model of the Titan. Thank you for sharing!

[@Mike-Bell]

Glad you think so!! 🫡

[@philshorten3221]

One suggestion has been:- Passengers moved forward to look out of the Front Port Hole and the entire sub tipped nose nose down, causing everyone to then fall into the front. If Titan had been thrusting forward at the time it would now be thrusting straight down. In the confusion control was lost, pressure would have increased much more rapidly and this might have been at least a contributing factor. It sounds a bit odd that any passengers would be allowed to move without instruction but if something of great interest swam past (6 Gill Shark or something) I guess it's possible a couple of passengers may have suddenly moved forward to look? Or is this just complete speculative rubbish? Thoughts anyone?

[@curiouscat8457]

The best information about the overall design of the submersible I found so far, thank you. One of the most important points: it has confirmed my suspicion the sub wasn't using variable buoyancy system, and its buoyancy has been solely controlled by solid balast. One of the unique (not necessarily bad) features of the contraption.

[@itoibo4208]

I would prefer using a pump and water for ballast, but I have to say I am impressed that the crew could, if all power failed, just lean the craft over by all going to one side, and causing the ballast to dump out.

[@NIOC630]

@@itoibo4208 lets assume you want to change boyancy by 100kg for going back to the surface, youd have to push 100l of water volume against 500 atmospheres of outside pressure, thats 5 megajoules of energy, 1400Wh, thats a huge battery pack to do this a single time. If you want to periodically go up and down for navigating it needs a hell of a pump as well, lets say you need to change 100N in 5s (like accelerating some thruster) thats pushing out 10kg of water in 5s which turns out to be 100kW of power.

[@itoibo4208]

@@NIOC630i prefer something dynamic but I see your point. That would take a lot of power.

[@malcomreynolds4103]

the submarine that went all the way down to challenger deep used the same thing

[@Mike-Bell]

@curiouscat8457 Yes routine bouyancy control was with solid ballast only. For emergency they had a high pressure air tank that would inflate a bladder for fast surfacing but I havent read anywhere that they used it or tested it. There was a pump system inside for the crew to operate to open the air tank.

[@hillbilly4895]

Personally, I don't understand why anyone would risk anything to see the Titanic.

[@petebarrow274]

Yeah, it was a pretty good movie, but not worth dying for.

[@MAS-ok5tp]

Not an engineer at all, just a thought that came to mind; Is using an A350 wing a good comparison? Seems to me that when the wing flexes one side would be in expansion the other in compression, thus exploiting it's strength . Titan's hull would be in total compression.

[@williambunting803]

Good point on the chamber cylinder axial loads. My take on this failure is in that carbon fibre is stronger than the epoxy to fibre bond strength. So the other loading on the hull material for a layered construction is radial. Without a radial tensile component in the build there was nothing to prevent the inner layers developing longitudinal ripples as the inner layers progressively delaminated under the compressive shrinking of the diameter. Mid layers are kept straight by surrounding material but the inner layers can wrinkle inwards to restore their original circumference. Also I would have opted for a shallow “V” tapered tube end socketing into the titanium end caps. The stripping of the titanium groove ring suggests that the hull ultimately on one side rather than Uni formally.

[@matthewbadger8685]

I'm astounded it lasted as long as it did.

[@BELCAN57]

It would be interesting to see what OceanGate's process was for generating the CF portion of the hull. Seeing videos of the layup process, I was surprised that there wasn't more attention paid to area cleanliness as well as temperature and atmosphere. A documented process review would prove interesting.

[@dustyflair]

documented? we dont need no stinkin documents.

[@UncleKennysPlace]

It literally looked lumpy.

[@electricgarage6556]

I believe the flanges blew out due to the port hole acrylic window failing. I believe its been said it was only rated for half the depth it was typically traveling to.

[@petertalvi8511]

Very well done. Best presentation I've seen overall. And not to take away from that in the least, am still not convinced the transcript is fake. The work in the main presentation is very solid.

[@spikester]

I fail to see where they said they were using the thrusters to dive in the transcript, but instead using them to lower their descent rate to no avail...

[@jonbeno9926]

Thank you for posting this video! I'm an aerospace engineer and completely agree with all points you make, especially the issues with maintaining fiber alignment in the axial direction being a very problematic aspect of the design. I get frustrated with the argument that CF can't be use in compression safely. It's simply wrong. It conveys the wrong message to the general public and the next generation of engineers about material selection and the use of composites. Engineers need to understand the limitations of the materials they select, and nothing can replace proper testing of a design.

[@Mike-Bell]

Thanks 🤙🏻 The “CF is crap in compression” comments have been relentless. They become very boring but at least they are good for engagement and assist in YT promoting the video. I carefully researched this video and so your comment is much appreciated 😀

[@prestonburton8504]

sweeeeet! God blesses your continued research

[@patrickmccarthy4089]

Just viewing this now and pleased with your analysis. Maybe this has been discussed but wirth mentioning, after 12 years of research and development the US Navy launched an unmanned submersible, the AUSS in 1983, capable to depths of 20,000 feet. The Advanced Unmanned Search System made 114 dives, is 17' long, 31" diameter and weighs 2800 lbs. And, is tubular, constructed with titanium end caps and it's center section of carbon fiber. So, there was a precedent for carbon fiber/titanium in submersible design. Granted, OceanGate did not have the budget of the US Navy. PMc

[@alpinegoat2054]

Axial Compressive strength of carbon fibers is 10-50% of their tensile strength. And transverse compressive strength is 10-20% of axial compressive strength… even without defects

[@Mike-Bell]

What is your point? Yes, in tension carbon fibre is in a class of its. In compression it surpasses most steels.

[@miketan4803]

​​​You must work in vacuum to manufacture w/o defects. Even then it could be stronger. Titanium would have offered better margin for error.

[@jamesdellaneve9005]

@@miketan4803Margins for manufacturing tolerances and errors )within margins) should be considered for the primary design. I worked on the C-17 cargo jet. The wing broke prior to it’s theoretical limit during it’s ultimate load test. There was a Defense Science Board called by President Clinton. I got to hear some of the results of the analysis. It was interesting to hear how conservative the designs were. One interesting thing was that the aircraft had twice the number of rivets and other mechanical fasteners than needed. Allowing for some very poor manufacturing margins.

[@Scalettadom]

​@miketan4803 exactly. With an autoclave. There were so many questionable procedures and lack of controls. Maybe cf could work for subs, but we certainly didn't learn much if anything from Titan in that regard thanks to Stockton's haste. He should have been testing after every stress cycle. X-ray and ultrasound.

[@Scalettadom]

@@Mike-Bell the fact that it surpasses most steels is meaningless. Most steel tubes are not fit to withstand such immense pressures. It's not a matter of being better than something, rather, strong enough to do its job...

[@LordSandwichII]

15:14 This is what I've been saying for so long; the excursion price was too LOW! It was so low that I now describe it as predatory. I say this because it put the Titanic excursion within the range of affordability to diehard fans (people who have wanted to see the Titanic up close their entire lives) who could now actually afford to re-mortgage their house to get on board the sub, and some of them did just that. I think these were the people that Stockton Rush was actually aiming at. Now even if there really is something to this whole "carbon fibre submersible" idea, it's become a poison chalice that no investors will touch for years to come. Thanks a lot Stockton Rush!

[@TheKruxed]

With outward flange bends it makes it seem like the joint between the titanium and the carbon started to shift at the rear and so instead of the typical implosion you would normally get you would actually get an instability in the pressure chamber which would then feed the pressure change through into the cabin and cause the explosion style damage as it would get ripped and pushed rather than crushed. It should mean there is 1 large piece of carbon to go along with the many smaller pieces due to the rotational force that would have existed and so I'm sure someone will recover it in the future

[@faircompetition1203]

The key to Carbon is it fails like glass and it suffers hidden stress failures from repeated deformation . We use it in sailing all the time and it is great stuff , light and strong . When it breaks it does not break a little bit .

[@vanderlinde4you]

And there is no acoustic sensor in the world being able to detect, premature cracking up. Due to the depth you don't have slow ingress of water or "leaks" but a violent implosion with such force, turning human beings into pasta in roughly 0.2 seconds.

[@killer1963daddy]

This reminds me of the darwinian advancement of early aircraft, when the designers were the test pilots. The good designers lived to spawn more designs...the bad ones not so much. 😮

[@itoibo4208]

haha it would help to be a good pilot, too, and a bit of luck. At least he left some clues for anyone wanting to try this again.

[@foxymetroid]

Of course, back then, the science wasn't completely understood. Compare that to 21st century deep-sea submersible design where designers have decades of research and experiments to help guide them.

[@s3cunit]

I'm just a guy who is curious about science and I found this was fascinating, thank you for putting it together. As usual, the media just ran with whatever got the the most views, damn the science or facts.

[@jacknoble1808]

Oceangate Submersible Titan Implosion Analysis June 30, 2023 Jack Noble Composite barrel information from internet: 55.9 inch inside diameter; 95 inch length; 5 inch wall thickness; 0/90 CFRP laminate. With a CFRP modulus of 8 million psi in the 90 degree direction and because the stabilizing effect of the end rings is about 10 times the thickness away from the center, the failure mode will be buckling in the middle of the barrel. The stability formula in Roark & Young yields a failure pressure of 8900 psi. Dividing by the design pressure of 5700 psi give a factor of safety of 1.56. This gives a strain level of .0044 in the composite and a radial deflection of the barrel of .145 inches. At the ends of the barrel, although insufficient information on the rings is available to determine elastic properties, it appears safe to say that the radial deflection of the rings due to pressure will be much less than the barrel. This means that the rings will be holding the barrel out at the ends, flaring the barrel like a cooling tower and creating significant bending stresses in the barrel and where you have bending, you have interlaminar shear, the achilles heel of composite laminates. Metals typically have allowable shear stresses of over 50% of the allowable axial stresses while composite laminates have interlaminar shear stress allowables of 2% to 3% of the axial stress allowables. If only 1.5% of the pressure load on the barrel was transferred to the rings the shear stresses would be enough to cause delamination in the center of the thickness of the layup all the way around which would account for the noises heard on initial dives but would not be visible and would not cause failure because the critical stability section is at the middle of the barrel. On subsequent dives this delamination would progress toward the middle of the barrel creating smaller noises, also reported. This delamination is converting the 5 inch thick composite barrel into two concentric barrels 2.5 inches thick. The critical buckling pressure of two concentric barrels 2.5 inches thick is only 25% of the critical buckling pressure of one barrel 5 inches thick so the margin of safety would be gone long before the delamination reached the middle. Since there is only one design condition of overall pressure it may have been possible to tune the stiffness of the titanium ring to more closely match the deflection of the composite barrel and avoid this problem but the fact that the composite shear allowable was less than the applied pressure would almost certainly lead to the initiation of delamination somewhere on the barrel. The only protection from this delamination would be to install several hundred 5 inch long bolts through the shell and the potential for leaks would render that fix impractical. It appears that it is probably not possible to successfully use this material in this application.

[@gregsmith7428]

This is probably the best presentation on what happened. Someone soon may be able to use carbon fiber installed to withstand pressure. It'll require better testing to insure safety over multiple dives.

[@michaellavery4899]

Correct. It is only with proper research and testing do we find better ways to explore this planet and beyond.

[@dustysgirl1434]

Really? It didn’t even get the date right in the description. It wasn’t June 8th. It was June 18th. If he got that wrong, what else did he get wrong? Fool me once, shame on you…

[@piperg6179]

Yes, a good presentation but he presents a problematic justification of carbon composite. In the real world where cost of development can astronomical for this kind of material application AND the improbability that such structure could be manufactured without imbedding a lethal flaw AND the fear an educated potential customer would have…this is a nonstarter choice of material. Great advatages, impractical use.

[@oldmech619]

I understand the carbon fiber shell was designed to be 7 inches, not 5 as built.

[@captainwin6333]

@@oldmech619 Even then its problem was it was gradually being destroyed every time it went down there because after high compression, carbon fibre doesn't recover, it stays permanently damaged, although only in a small way. You've heard people talking about the loud cracking noises, that's delamination and individual fibres splitting and resin cracking. The sub gets weaker with each use. You don't get that issue with Titanium. It can be modelled on a computer to accurately know how many dives at that depth it will take while staying in spec. The only reason Rush went with CF was to save weight and squeeze more paying customers through the door. There is no reason why the global submersible world would choose to dump Titanium for CF because A Titanium is well understood and easily modelled in computers to predict strength which you can't do well with CF and B, they don't need to run it as a bus, cramming loads of people in to turn a profit. CF might be an idea for small subs that could be used on coral reefs, but the bottom of the ocean? Nah.

[@Sean006]

Refreshing to hear some new ideas on what happened. An interesting watch. Thanks 👍

[@selkieboat]

This was a well presented discussion regarding the Titan implosion with truly excellent graphics. But the one point of interest that was not mentioned is the elastic modulus of the two materials, carbon fibre hull and titanium end caps. They do not react the same under pressure, so over time there is going to be degradation.

[@Mike-Bell]

Great point but 90% of my audience doesnt really want technical detail so I am hesistant to give too much detail and bore them. The good thing about combining Titanium and Composite is their rate of deflection is very similar to the extent that differential movement is usually not a big factor. And surprising to me when explained this by the expert I consulted is composite deflects slightly than titanium and that explains why carbon fiber is rigid and therefore brittle. I am glad you are interested in the technical details because so am I.

[@nielsharksen78]

​@@Mike-BellI certainly appreciate the detail. Perhaps you can add it as a "foodnote" at the end of the video, so those interested can continue watching while the general audience has an on-the-point first 15 minutes.

[@halomultiplayermoments]

Yes more technical details are essential

[@prestonburton8504]

very good!

[@Apollo49152]

Great video. I hadn't looked beyond the headlines until I saw this video. I'm glad I found this first.

[@veganbutcherhackepeter]

As someone else put it quite nicely: with just a few strands of carbon fiber, you can drag a car down the road, but try pushing a car down the road with the same carbon fiber strands. Doesn't work so well anymore now, does it. In aircrafts, carbon fiber is used to withstand internal pressurization, not external one. It is an amazing material to handle a pull on its structure, not a push. Because under such conditions, the fibre itself doesn't add anything to the structural integrity of the hull and you're basically sitting in a hull of just epoxy.

[@eddjordan2399]

that,s simply not true. think of carbon fiber like reinforced concrete the carbon fiber is the rebar and concrete is the resin. Engineers other wise wouldn't make aircraft wings out of the stuff. but what dose matter is how its put together and that its tested to know its limits.

[@tiitsaul9036]

This is a superb analysis. Thank you for sharing.

[@Mike-Bell]

Glad you liked it!

[@M14armorer]

Hands down the most professional presentation on Titans failure I’ve seen. Very well done sir

[@Mike-Bell]

Wow, thanks!

[@torferguson3866]

Rush knew the second shell was close to expiration because he lucked out receiving audio warnings with the first shell, ascended and survived. I've heard people speak to the legitimacy of the transcript as well, as I recall it came out not long after the event. That timeline suggests he had about 20 minutes to make decisions, his messages are very brief and if it is fake it's still a very feasible timeline. The transcript also suggests he had a lot of issues with ascension and this makes sense as the sub was objectively very unreliable. My theory is that he descended faster knowing the shell was close to it's shelflife due date. The more dives he got out of a shell the more money he saved. The ultimate gamble

[@SteveRichfield]

My theory: Tiny air bubbles at atmospheric pressure that were inadvertently included in the carbon fiber imploded one-by-one under extreme pressure. First the bubbles near the outer surface imploded, which weakened the outer surface, then deeper air bubbles imploded, until the carbon fiber still l@@ked like carbon fiber, but it was broken up around imploded air bubbles on a microscopic scale until it was unable to carry the load. Has anyone looked at THIS possibility?!

[@razor1uk610]

Yes, that is how pressurised delamination works, each micro bubble that is compressed, provides more microscopic room for fibre movement to occur at that point, with a change in pressure changing irrespective of if it is an increase or a lessening. Then it is a question of time and when, not if; once enough fractures between the individual fibres and the resin matrix to fall below the structural threshold for a given pressure, force or other loading being upon the the resin and or the fibres. .......it will then fail instantly.

[@pyropulseIXXI]

This is nonsensical; it is a fiber and doesn't do well under compressive forces. It survived 12 or so dives before catastrophically failing. And bubbles wouldn't implode if they are in a carbon fiber resin matrix; this makes no sense, as what is putting all the pressure to implode it; if it is air, it would just compress; the carbon fiber is under pressure from the water, and the bubbles aren't under pressure from the carbon fiber; but the bubble gap means the carbon fiber has less 'support,' thus the carbon fiber implodes, not the bubbles. Again, if the air bubbles do 'implode,' it is a consequence of the carbon fiber hull failing and not the cause of the hull failing (at least not directly). It failed because water isn't perfectly incompressible, and it elastically rebounded upon the carbon fiber once the carbon fiber shattered, thus causing devastation.

[@pyropulseIXXI]

@@razor1uk610 This is wrong; even if you have no bubbles at all, the carbon fiber would still fail; it has micro-fractures and cracks, which has nothing to do with bubbles causing this; the bubbles, if anything, are a consequence of this failure

[@KP-bq8sr]

Further to that, CF undergoes an extremely unique form of delamination called Snap Buckling. It's been found occuring on underwater cables. A very terrifying form of delamination when the inner most layer of CF is actually the first to go setting it an instant chain reaction.

[@prestonburton8504]

possible! it withstood multiple dives -

[@brucebadeau9906]

I have worked with Titanium and Carbon Fabre for yachting purposes. My limited engineering knowledge is asking about differential thermal expansion and contraction... and Youngs Modulus is different for both materials... As you mentioned a rounded filament wound shape similar to SCUBA tanks would have been a better design... or a sphere... BUT then you have holes at the ends for access... and there would likely be a higher resin to fiber ratios due to the geometry in those areas --- plus more sharp radius curves === and possibly some cutting of the fibers for access ports. === and this could be a place of weakness --- it just doesn't take more than a pin hole to start cutting and rupturing materials at those pressures ... or worse yet a catastrophic failure... Look at the water jet cutters --- that could happen down under .... with no way to stop the intrusion.

[@jbyrd655]

20 mm = .75 inch (3/4, not 3 and one quarter) 200 mm = 7.87 inches. Leaving aside the "how many elephants" hyperbole, pressure at 12000 ft is 5600 psi, 380 times that at the surface, but is by no means extraordinary. Consider that some hardwoods are able to withstand this pressure...

[@daviddempsey8721]

Thanks for providing such a detailed and insight filled presentation. It’s an antidote to the flap, clickbait and sensational guesswork on some channels.

So far, the best review of the situation I've found. I constantly doubted that popular opinion about carbon not being good in compression. I thought, hey, we have composite plane wings,.. man, something does not add up. And longitudinal load (*facepalm*) this adds a lot to think about. How did I not considered it. Circular windings being held up just by resin would simply collapse like a slinky. Those straight fibers really could have been the actual part that gave away. Thanks for fine insights.

[@Mike-Bell]

I'm happy you liked it. They did a second salvage 2 weeks ago. There was a foto of the recovered aft pressure dome they brought ashore. I have seen nothing of the carbon fibre shards they may or may not have recovered but therein will lie vital clues as to how the tube may have failed. I certainly hope there is a definitive explanation for how this happened.

[@lepompier132]

An aircraft wing is very different from a sub. One is exposed to stress by flexing from positive and negative G loads. When the sub was exposed to stress from heavy loads from pressures from the deep sea. And also the pressure difference, a plane at 12500 feet won't have the same pressure compared to the sub at minus 12500 feet with all the weight of the water on top of them and around them. And carbon fiber will react in a very different way between the upper atmosphere at 12500 feet and minus 12500 feet down in the sea. And Carbon Fiber has it's limits and can be the weakess point in a vehicle if not properly used or has defects in the manufacturing process.

[@ruk2023--]

Chinese whispers was likely responsible for that one. Someone who knew the truth would have said that CF isn't as good in compression strength as tensile strength which is true and that will have become CF is not good in compression over time.

[@numeristatech]

@@lepompier132 the ambiant air pressure is not so much the issue but the compression of the wing spars that make up the wing frame and attach to the fuselage. These are bouncing up and down holding the weight of the aircraft. Parts will be in tension, other parts will be in compression as the aircraft bounces through the air, turbulence, manoeuvres, but the key is in the testing and designing that wing box to not fail under known loading so that tue wings don't fold up under normal and some abnormal loads. You can see some photos and videos of wing testing where aircraft wings are being bent to 45+ degrees without failing: the bottom parts of the wing structure is under tension and the top part under compression as the wing is not a flat 1 dimensional part - and we know that things can fail, so we design in a safety factor so the wings won't fall off an airbus after 10 takeoffs :)

[@StillAliveAndKicking_]

We have repeated pressure cycling of a plastic cylinder glued to metal ends, and repeated temperature cycling of materials with dissimilar thermal expansion coefficients. Then we have compression forces at each end, pushing against the cyclinder ends. Then we have repeated pressure cycling of the plastic cylinder. Just take a look at the other submersibles that are capable of descending to the Titanic, they have thick metal pressure hulls. This was a Primark/Lidl submersible.

[@cornerofthemoon]

Regarding your comment about the crew not wasting time typing messages to the surface ship during a crisis, that may be true for a normal person but this is Stockton Rush we’re talking about. He had a propensity of being flippant about danger and never seemed to stop talking so I think the messages could be credible.

[@MrChopsticktech]

Great point. The typing/messaging system was probably one of the few things that worked at that time.

[@mikaturunen2354]

And he had so great trust on his design that most likelly he did not even sense the danger? He had get accustomed of loud bangs of the material. And it seems that nearly all of the dives had some problems. It was a "normal day's work" for him untill split of a second... The messages can be legitimate.

[@nessunodorme3888]

Skepticism about the messages on grounds the crew wouldn't be wasting its time like that in a crisis implies they would've been busy with other tasks to save the day. But, like what? Maybe each could grab a Gameboy controller and bash madly at the keys. But, this austere submarine tribute to Steve Jobs and Elizabeth Holmes was little more than an automatic elevator, remember? The term "crew" is overblown. A better word would be, passengers or even "cargo" for the little "crew" had to do. By design, Titan was dependant on the surface ship and crew for everything. Even a successful return to the surface would end in tragedy if the surface ship guys couldn't locate to laboriously unbolt and free them from the thing. Under the circumstances, typing messages to the surface was the only meaningful thing any of them could do in a crisis or any other time. So, it's shocking but no surprise, Titan had no more reliable means of communicating with the surface crew than they did, no emergency last ditch measure, say, the equivalent of tin cans connected by a string. Of course they were typing messages!

[@theontologist]

No. Past transcripts were super-brief and concise. The messages in this fake were out of character.