My uncle told me when he was studying engineering his professor told the class , If you ever design a bridge that fails you had better be standing under it.

The more I learn about this contraption, the more it seems this Rush character and his team of engineers at Oceangate have put in it the same amount of sense as the dudes that used to close themselves into wooden barrels and plunged from the Niagara Falls.

Nothing more interesting than to watch/ listen to an engineer who knows his facts well done to you

Yes, submarines also share the tube-shaped body as the Titan submersible did, but no submarines go down to the depth at which the Titanic rests, 13,000 ft. At that depth, a ball shaped chamber has the best strength. This is one thing that people tried to point out to Stockton Rush, who ignored their concerns.

Speaking as an electrical engineer myself, this video was amazing. You did an outstanding job explaining everything.

The more I learn about this sub and its construction, the more it sounds like it was definitely a matter of when, not if it was going to catastrophically fail. Physics - 1 S. Rush - 0

I am not an engineer, but I have to tell you I feel that you explained it well. I understood everything that you said. Seems to me that with a CEO like him would have spent the money wisely and developed this vehicle in the correct manner. Not to take financial shortcuts. As a result all those people (including himself) paid with their lives. What makes this more horrible is that it could have been avoided.

You are a great communicator. This stuff is extremely technical and you manage to break it down clearly and informatively. Please keep at what you are doing. You have a gift.

I learned more from this 8 minute video than I have watching dozens of videos by other 'engineeers'. As others have said, the more I learn about the sub, the more appalled I get.

Rush was warned by many many experts in deep sea diving, and his ego ignored them all, ironically just like the owners of the Titanic.

Thank you for a well presented explanation of this complex area. I was horrified to find that according to one video, fittings (such as lights) inside the hull had been attached by drilling into the pressure hull and presumably screwing the fixings into the hole, with or without epoxy filling. This struck me as a likely to create a serious "stress riser" point wherever this was done and seems especially dangerous if any holes were located away from the titanium supported ends in the main cylinder. Even partial thickness holes (as I imagine they were) would seem very dangerous given the enormous cyclical loading the hull was expected to endure. Your comments will be valued. Tim D (Old submariner - welded steel hulls and much lower depths, but still scary sometimes.)

You hit the nail on the head. This is the first explanation I have seen of the flaw in using carbon fiber. Great for a spacecraft where the fibers are stretched by internal pressure but no good being compressed by external pressure in deepsea diving.

I'm not an engineer, but I taught soft-skill communication techniques to engineers in many fields for many years. You get an A+ for this vid. 🤗

Pro tip: Even if your domain resides outside regulations, it's a good idea to adhere to professional standards, especially for critical life systems. Rush should have determined the Mean Time Before Failure, minimum time to First Failure, and crush depth, on prototypes before the first human stepped on board. Every Oceangate engineer should have their license revoked.

A transcript of text messages between the sub and the mothership shows that just prior to the loss all warning indicators were in the red, also the sub had been descending far more rapidly then intended and when noted despite releasing all ballast and the landing frame and using maximum thrust ascent was extremely slow indicating the sub was overweight, most likely due to leaks in the joints between the carbon fibre and end caps. Sadly it appears the occupants were aware for about 20 minutes that they were in dire straits prior to the final implosion.

The greatest contributing factor to the loss of the Titan was hubris. It's like Rush and OceanGate learned nothing from the sunken ship they were so keen to view. Excellent video my friend, very well explained 👍Thank you.

I subscribed because your explanation was very clear and unpretentious. Additionally I normally find mechanical engineering very tedious and I rarely bother to immerse myself in the subject but you made this explanation very interesting. I am going to look at your other videos now. Have a great day and thanks for the upload and the work you did producing it.

You explained this better than anyone I have seen so far and I have been watching hours of coverage. A+

Good explanation of why carbon fiber is a poor choice for a submersible. Another issue was the difference in compressibility between the titanium end cap and carbon cylinder, creating high shear force on the glued connection. This in turn can cause small cracks in the glued seam allowing hi pressure water to enter and quickly propagate any potential void space at the edge of the carbon shell itself, thus causing rapid delamination. - Kinda like a jet sprayer hitting the side of plywood where water can work it's way in-between the laminated layers. This could also explain why they had several successful dives before it imploded.

Thanks for a very informative video about this incident. One thing I've not seen mentioned either here or elsewhere is the standard engineering proof for a vessel like this which is to build a second vessel and take it right through the planned loading duty cycle - say 200 cycles to depth if the planned structural life is 100 missions (inside a pressure rig or, cheap option but still effective, by winching the thing down and up in the actual ocean.) Followed, if the vessel hasn't failed by then, by a test to destruction, looking for (aerospace background here) a pressure loading of 150% of the planned 12000 ft. The NDT would be carried out continuously during that development testing and MIGHT give options for design revision if problems were found. Use of more rigorous NDT during operation, whilst it might have saved lives, wouldn't save the programme if the vessel had to be scrapped after the 10th or 20th mission. Real-time NDT, for a failure mode that would be expected propogate instantaneously, doesn't really seem to help. And the bravado in showing how "engineering" can be much faster and cheaper than the experts think, as exemplified by the game controller, shows just how ill-conceived this venture was. Sure, all these corner cuttings do indeed get you there a lot faster and a lot cheaper that those stuffy old professional engineers would allow but you might not want to be there when the shortfalls of the methodology become clear...

When Carbon fiber is laid up without a vacuum, microscopic bubbles form against each fiber. When the pressure increased the bubbles got smaller and smaller and when the pressure decreased the bubbles got larger. Each cycle tore at the fibers weakening the entire 5 inches. enough cycles and the entire hull failed and the sub imploded. Rush did not spend the extra money to gas out the epoxy resin in a vacuum chamber and this is the major reason it failed.

There was too many red flags to ever allow this submersible to dive with passengers. They really talked it up how good it was. The whistle blowers were scared of going public against a rich and powerfull CEO that could ruin them. The submersible community should have leaked info to the media about the submersibles being lemons. It would have saved lives.

In the unconfirmed Transcript from the submersible, they mention a crackling sound coming from the AFT part of the hull. That being said I think it was the connection between the titanium and carbon fiber that ultimately did it in as that is the literal point of most stress and variation (squeezing in the middle and rigid titanium on the size, thus max movement and pull on the edges). I actually think the acoustic sensors did their job long in time, but the the water "started splitting" the ring area and lamination a good 15 minutes before it went pop.

Very nice job explaining this in laymen terms. Also, I'm American, and appreciate the subtitles but I understood you completely without them. Namaste my friend. I wish Rush had you on his team. He still probably wouldn't have listened to you as he did with others on his team. He had a God complex.

Successful deep sea subs are very different in two respects - the material used (titanium or surface treated aluminum) has a hardness rating that is about 6 times that of epoxy - the outer layer and glue that binds together carbon fibers in a composite hull. The second key point of weakness is what you alluded to - non uniform resistance to outside stresses due to the directional nature of the carbon fibers themselves. The titanium and aluminum hull submersibles have no such vulnerability. In addition to being a lot harder than epoxy and better resisting material displacement under high unevenly supported loads, their material structure is much more uniform and therefore the resistance to outside stresses is more uniform and predictable. It's really not that complicated and you would have to be a complete idiot to ignore these colossal drawbacks to the use of composites in high pressure environments. It's pretty clear that spending a good deal of money to build a bad design doesn't confer extra levels of intelligence or brilliance on the part of the spender. The Darwin Rule really doesn't care how big your wallet is. Arrogance and stupidity are still a deadly combination.

Another detail that most folks are ignoring is the cylinder was subject to tremendous axial loads. While those titanium end caps were strong enough to withstand the pressures, they also have to be 'kept separated' by the cylinder. That's over 58 MN (13 million lbf) applied 'across the fiber'. A narrow walled cylinder subjected to much axial load could suddenly buckle, especially if the cylinder deformed even a little bit from some growing defect.

I'm not an engineering student, but your explanation and visuals kept me so interested in the video! Really loved it!

Thank you for this video. As other people have said, I'm not an engineer either, but you explained this clearly and concisely! You did a wonderful job explaining terminology and concepts. You answered ask the questions I've had in a way that was easy to understand and follow. The video felt much shorter - like only a couple minutes rather than the almost 10 that actually is! Well done!

What an excellent video!! I remember when carbon fiber was first used on mountain bikes. It was used in frames, suspension struts, handlebars and seat posts. The stuff FAILED ALL THE TIME. Usually the failure was sudden!! Using carbon fiber without proper stress testing and without proper re examination after every dive made the Oceangate a DEATH TRAP!!

According to leaked transcripts, looks the rate of descent was too fast: they were 1h earlier than scheduled at 3700m depth, and being lighthearted about it. For a sub, a faster rate of descent means buoyancy is off. Indeed smth was off because when they tried to ascend after alerts, they were slow (6m per min). Had procedures been taken seriously, the ship would have asked the sub to slow their descent, they would not have been able to comply easily, which would have triggered an abort when it was still in a safe zone. The company did not toy with one boundary, but all at once. They did not learn or even tried to learn anything from previous mishaps. Brashness and overconfidence killed ppl.

Seriously man, Thank you for doing this. I actually understood what you were showing. Thank you

Carbon fiber is not an ideal choice for a cylinder being used to resist compressive forces across the center of the fiber, but Titan suffered from a second major weak spot; the transition from the CF hull tube to the titanium end hemispheres. As the different materials would tend to compress unequally under the same outside pressure, repeated cycling would tend to create and enlarge defects at the material transition, which is made more sensitive by the use of unreinforced epoxy to secure that joint.

Excellent video. Your explanation of composite engineering and failure was very concise.

My two cents. Based on current available information, I would say CF hulls for deep sea exploration is a no-go.

Excellent analysis, thank you. Since the submersible was to carry people, I believe tit should have been tested repeatedly at depth until destruction so the limits of the sub would be known and better studied.

Maybe they should have used a weaving pattern in constructing the hull versus a unidirectional wrap. This would have made the strength multidirectional. With all of the wrap going in one direction, the weakness you pointed out was inherent in the design.

One of the best engineering reviews of the Titan I’ve heard. I wonder if Ocean Gate had the benefit of this information? I expect the information was available and not acting on it makes Rush a fool. That Rush took others with him is troubling.

One of the others noted that the window was missing. He was indicating that he thought the window failed. This is unlikely because the ring that hold the window in was also gone. This would indicate that the window was blown out from the inside. Think of water moving at 1K mph from the inside of the window. I do agree that the tube failed first, Likely at the junction of the fiber and the rings at the ends.

You are the first, I have heard, to address the actual issue that brought Titan to its tragic end. Narcissistic Arrogance and the inability to admit there may be critical design risk that dictate rigorous testing after every dive or reported anomaly. Thank you

You have made the best factual review on this than anyone on the internet. Well done sir, very well done!

Fascinating video exploring the different loading properties of carbon fiber composite materials. Very well done! Thanks for this!

Thank you, I think you were great at explaining how carbon fiber works and withstand pressure. What do you think about the edges? Where the carbon fiber attached to the titanium rings. There, wouldn't both materials move in different ways when subject to pressure, leading to a potential rupture point?

It's strange how the vessel is built to withstand such pressures and yet fish and other soft skin creatures dewl in such conditions. Fascinating mother nature.

Thank you for being the first mechanical engineer on KZfaq to outline the application of FRP construction and its difficulties (in this case dangers).

Something that almost everyone has missed is the bending moments applied to the carbon tube along its length since its ends were more or less constricted and the central portion only had 1 bar atmospheric pressure supporting it.

I'm no super expert, but the minute they described a pressured vessel with carbon fiber, exactly what you describe here came to mind. I've dealt with some carbon fiber in bicycle construction and realize it's great in tension, but not nearly as good in pressure. Secondly, the transition from the titanium to fiber boundary would leave me to question, along with the temperature variations. Sounds to me like a case of someone with money and vision, but not so much real world experience.

What all these engineers are missing with the technology that was installed to detect a integrity issue within the hull, is that it doesn’t account for the fact at the depths they were operating, even if a crack had started to form, the pressure would have continued regardless if the decent was arrested and they returned to the surface… the change in depth going up, would have increase the failure rate of a formed integrity issue…..so the alarm, would have merely been a reminder, that it was game over. Not to stop a catastrophic failure.

Very good. Probably the best of the current crop of Titan videos, as it gives a much more comprehensive and knowledgable view of the sub's weak points and what probably happened. Combine this with one of the videos about the leaked text message transcript (assuming it's real) and you've probably got about the best understanding of this tragedy you're going to get for now. Thank you.

My understanding is that carbon fiber composites may crack abruptly when twisted. This might be due to the matrix or glue cracking. So, the carbon fiber body may have distorted under load, leading to cracking, and the glue holding the ends together may have cracked under the combination of cold, wet environment and twisting load. I heard an alleged transcript of the conversations between the submersible and host vessel, which indicated the "Titan" was descending considerably faster than expected, and then had difficulty ascending. Might it be possible that the "Titan" was becoming waterlogged, perhaps even flooding in some areas, almost as soon as it submerged? Perhaps the weight of this extra water would have stressed the frame, especially during its struggle to ascend.

Would be really interesting to see a model that includes the locations of all penetrations and mounting points on the hull. Penetrations and mounting holes (or regions that are stiffer if external mounts are attached with welding (or glue) can change the symmetry of deformation under load and cause stress concentrations. Even how the lifting points are designed and distributed can have an affect on it's integrity (it is over 10 tons in weight after-all... ) Do you have access to any engineering documents / drawings that include that info. A model including that would be awesome to see!

If the leaked transcript is real, it sounded more like the equipment bay sprung a leak. This created additional weight which accelerated the descent. It also seemed to knock out one of the batteries. If water was streaming in at that depth, it was probably like a cutting beam and cut through whatever was in its path.

That was an excellent explanation, better than any others I've come across since this event. Thank you.....and I've subscribed as I hope many more will.

There are lots of posts on this subject of various quality- this is the best one out there. Well done. I have been working with composites for 40 years and agree with 98% of the content . My only comment is that it is best to view the loading case as a flexural bending situation. This gives tension on the inside of the tube, compression on the outside, and shear on the centre section of the laminate. The compression and shear performance is very sensitive to defects. Great video 😊

My first thought about the failure, was the bonding between the titanium ring and the carbon fibre ends. I still feel, that was the point of failure. The excellent graphics shows the tube deforming lengthwise, narrowing in the middle. That is surely going to stress the bond with the rings, as the outer layers will pull against the bonding in the ring.

Revolutionary Engineering, a channel of might, A source of knowledge, a guiding insight. With gratitude, I watch and learn, So much to gain, so much to earn. Mechanical stress, pressure, tension, Tensile strength, a world of invention. In Revolutionary Engineering’s videos I see, A world of wonder, a world of glee. I love engineering, it’s plain to see, The power of creation, the power to be. Thank you Revolutionary Engineering, for all you do, For sharing your knowledge and helping us through. Your videos are valuable, a treasure to clutch, A source of learning, they mean so much.

Of all the voices on here since the demise of titan I feel yours is the best as it's backed with facts.

Great job and thank you for hard work. I'm sure you'll have 200,000 subscribers soon and keep up the great work. I'm sure you worked many hours on this and it is excellent. Thank you.

They said flat out it has been making cracking noises on prior trips and this was the second hull,acoustic sensors were a bad idea but it's moot since he didn't listen to them and stop diving

Excellent explanation, thank you. I work as a Test Inspector for a company that manufactures gas compression equipment dealing with pressure vessels of many different materials. Carbon fiber is an excellent material, but as you described the act of compression and decompression over a period of time can create stress fractures, and this along with extended periods of exposure to pressure perpendicular to the fiber strands was an invitation for catastrophic failure. Great job at making this understandable for everyone.

Excellent video. This is the most depth I've seen anyone go into on potential failure modes of the carbon fibre itself and contained some interesting new ideas.

You have explained the technicals so very well.. Not even those American channels have understood these basics while sending that plastic can so deep. Or probably they were just stupendous in this act.

Excellent video. Hope that this gets lots of views in the US where public education is imploding faster than the Titan. Thank you for an excellent analysis.

VERY informative video that helps non-engineers such as myself understand the physics of repeated stress and tension on carbon fiber. Thank you! New sub from Toronto, Canada :)

Agreed. I don't think anyone really understands the failure mode of this structure. We can say for sure that it was associated with fatigue however - it worked previously. Carbon fibre is more vulnerable to fatigue than titanium. The cylindrical shape was not adequately catered for - Radially wound CF. Supported at the ends by titanium. No mid or any internal support. No NDT. Glued end joints. I think that the tin can comparison is valid. The two end caps were waiting to come together and all it took was a slight change in force vectors as the tube buckled due to fatigue failure.

How would the cold temperatures at the depth of the Titanic affect carbon fiber. I know it can stand a lot of heat but, from what I've read, it looks like it isn't so good when it gets very cold.

Finally, someone talking about the tension vs compression stresses in an element particularly where the fibers can't significanlty resist the compression stresses on a cyclic basis over time. Someone needs to go to jail for this, experimental or not! Very good video. Well done!

Glad to see a small KZfaqr get these kinda numbers

Detailed and persuasive analysis, thank you.

If anyone ever asks me if I want to go see the Titanic in a submarine, I'm gonna say, "No thanks!"

Thank you for producing one of the more intelligently produced, informative, and well narrated videos regarding this tragic topic.

Thank You for excellent discourse on this subject! My opinion was that there was differential thermal issues with the binding agent holding the carbon fiber and titanium together. That the difference between the three materials created expansion and contraction issues creating micro cracks in the seal especially if it was used repeatedly. I believe that they dove to fast not allowing the temperatures and pressures to occur in controlled manner within tolerances. I believe that this was a fine submersible for working depth of 1,200 meters and a maximum of 1,600 meters. I believe that the porthole window should have been upgraded and been certified. There should have been a sister vessel on standby. They should have had multiple additional rov’s... I believe that carbon fiber is workable material for submersible vehicles but that it’s limitations and weaknesses must be recognized... I would have placed a additional layer of carbon over the titanium and carbon fiber hull creating protection for the edge of the titanium at the joint with carbon fiber. The glue seal should have been completely protected... A second titanium ring should have bolstered the structure from the inside. At that depth in that vessel my protocol would have been to slowly lower the vessel by remote control without any passengers for the maiden voyage... Give it a full pressure test and all systems check... Slowly returning to the surface. Perform all checks and maintenance. Only then proceeding with the maned mission. Then only using the vessel that one time at that depth. I believe that would have kept it within safety parameters. At 1,000 meters that I think that vehicle would have a fine number of service hours and dive numbers. At greater depth there is no cutting corners and saving money for lower cost tickets or increased profits. The narcissistic thinking led to confirmation biases and a lack of appreciation for the physics involved. I am afraid to ask if they even had spare controllers? Don’t place faith in material things. Material things will fail you. I would like to build a sailboat that is submersible... only to 60’ for standard use. In this way the sailboat can seal up and duck underwater in a storm. Then pop back up for good weather. For my purpose carbon fiber would be a good choice... but I don’t know what lottery I would have to win to pay for that much carbon fiber in the thickness required. LOL You can’t cut corners on materials and engineering.

Carbon fiber, with "glued on titanium rings" for attachment is simply an engineering nightmare for starters. No glue on Earth is tested and certified for such depth as the Titantic. Either the glue and/or stressed carbon fiber from depth cycling is the only apparent reason for failure.

I assume something laminated and subject to huge compression is going to stress the bonded layers. Which will then delaminate.

Brilliant inspection of the factors . Love your work

I'd never seen your channel and was expecting a lot of gibberish, but this is the most informative video I've seen on this subject by a long long margin. Congrats!

Great explanation! Nothing like an engineer who starts to build from the basics!

Stupidity...Laziness...and hiring on the cheap = DEATH

You look to be showing the side pressure of the tube part. You didn't mention the end to end pressure of the ends. Any slight difference in deformation of the tube part is amplified by the end to end pressure.

Yr explanation is so simple n easy to understand for pple like me who are not frm an engineering background...I'm shocked that a mere video game controller was used!!

Very well explained and thorough, I'm impressed. Reaching a higher bar than the majority of KZfaq channels

Supposedly the carbon fiber had sat on the shelf for a year at Boeing - they rate the material for 1 year of shelf life and were discarding it - in some way got rid of it - Oceangate probably got a huge discount on it. Your models probably don’t account for expired carbon fibers.

I also can't help but notice at 8:01, the computer monitor seems to be bolted directly into the inside wall of the sub.

Subscribed. Love the video! You’re very well spoken and speak very intelligently and eloquently.

It's not just the carbon fibre issues, but the use of titanium and carbon fibre together that caused this disaster. The cumulative fatigue between the two, caused by having different pressure coefficients is the culprit here, resulting in delamination of the carbon fibre shell. Imagine the occupants sitting inside that thing for 20 minutes, alarms going off (sonic tests failing), listening to the 'crackling' sounds - it's the stuff of nightmares.

I have no engineering background. Have heard it said that carbon fiber is best wrapped in overlapped diagonal layers. Video of Titan hull being wrapped it all goes in one direction like a spool of thread. Would this have made a difference?

This was a very informative video. Thanks for making it in a way that even a non-engineer can understand. So it sounds a lot like OceanGate was extremely negligent, essentially.

A very good and comprehensive analysis, thanks.

All the carbon fiber vessels for _deep sea_ purposes are generally designed as _1 time use vehicles._ As I understand it Rush took inspiration from 1 (2 time technically, they test then the run) time use vehicles and tried to make something reusable with the same materials, while ignoring why everyone else only used those materials for single use vehicles.

I’m inclined to think the pilot of submersible lost control on descent & it nosedived onto the bottom of the ocean & imploded. Perhaps too many people were in the nose trying to look out the window. Perhaps Rush jettisoned too much air from the ballasts & didn’t have enough compressed air re-establish sufficient positive buoyancy or account for the inertia on descent.

What a clear and understandable explanation for someone who focused more on the arts than the sciences in school. Thank you! ❤️

I appreciate your knowledge and how clearly you explained all of this. Thank you. I will look up your other videos.

Now its time for you to become a Engineering professor / teacher! Your explanations were very easy to comprehend, and you kept the conversation interesting! Thank you!

Very informative video, thank you. I would hope that the design process and testing will be investigated so that we will be able to judge whether they had answers to the criticisms that have been made. At present I feel that many people are simply saying 'it failed, therefore they did it wrong', and just pick their favourite explanation from those on offer. It is suggested that they detected the impending failure of the hull and tried to ascend, but the craft failed to ascend fast enough. By having the means to detect damage within the hull they acknowledged this failure mode was a likelihood, and seem to believe that when it occurred they would have time to ascend. So whilst there may well be basic flaws in design of the vessel, it might be that the real question to ask is why didn't it ascend sufficiently when the (predicted) hull damage occurred? If it did, they would all be alive to tell the tale.

Lexan or a similar material should be examined as a lightweight alternative to steel or titanium. The bulletproof windows of the White House are made of Lexan. The hull of the Titan likely derived its compressive strength from the epoxy that held it together and might have been stronger if carbon fibre were altogether absent.

One of the finest explanations and video of the failure.

That was very informative. Thank you. You seem like a very kind man. I will send this video to my people.

Great video. Thanks It is my opinion that any cyclic fatigue would be multiplied in the epoxy/titanium interface. I have deep concerns from the brief glimpses I’ve seen of that interface design.

Terrific video, very informative. The one question I have is how were the controls (thrusters, ballast and sled drop) operated from inside the pressure vessel?

This is the most detailed information I have seen on the performance and issues with carbon fiber. I'm not an engineer, but it would stand to reason that exhaustive, unmanned, testing should be done on any unit, especially one that was not manufactured to the existing standards, before putting lives at risk. People think that because it is used for plans it is ok for submersibles. Plane cabins are pressured from the inside, whereas the pressure on anything going to the bottom of the ocean is from the outside. The affect is not the same. Planes undergo structural testing all the time due to the stress on the fuselage. They do not undergo testing while the plane is in mid take off, in flight or landing. So the theory that if we hear cracking we can just abort and return to the surfaces is codswallap. I saw on another post that the material they used was rejected for planes so they were able to buy it at a lower cost. Going "on the cheap" to the bottom of the ocean, yeah that's a hard no!

Excellent explanation. I am in construction but I am not an engineer and I enjoy learning from an engineer's perspective. Well done, thank you for making this video. I am going to subscribe to your channel!