OceanGate REALLY messed up - A Structural Engineer's Perspective | TITAN'S TRAGEDY

Was OceanGate's Titan Tragedy Preventable? Step aboard our virtual exploration as we uncover the story behind the Titan Submersible disaster. As a Structural Engineer, we meticulously examine the crucial aspects of its construction and operation, seeking answers to the question that lingers in our minds: What could have gone wrong? Join us as we analyze and discuss the potential engineering and design flaws that may have led to this catastrophic event. #titanic #titan #oceangate
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Narrator/Researcher/Lead Writer: Dr. Mayank Chadha
Lead Editor/Researcher/Producer: Shivank Chadha
Writer/Creative Director: Drishti Chadha
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TIME STAMPS
0:00 Introduction
0:59 What goes into Structural Analysis?
1:12 Effect of Water Pressure on Submersible
2:56 James Cameron's Take
3:29 Possible Structural Flaws of Titan
8:30 Red Flag: David Lochridge's Lawsuit
8:52 Red Flag: Rob McCallum's Emails to Stockton Rush
10:02 Red Flag: Marine Technology Society's (MTS) Letter
11:06 OceanGate's Legal Disclaimer
11:23 Communication and Electrical System Flaws
12:34 Lessons Learned
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MY WEBSITE : www.doctorchadha.com/
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WHO AM I? Hi. I am Mayank Chadha. I am a researcher at the University of California, San Diego, where I teach and do scientific research on a wide variety of engineering problems. I hold a Ph.D. in Structural Engineering focusing on Applied Mechanics and Mathematics. This KZbin channel is a pet project in collaboration with my brother Shivank Chadda, through which I plan to share the knowledge I have amassed over the years in Physics, Mathematics, and anything else I find interesting. You are welcome to join us on this journey and learn with us.

[@doctorchadha]

I appreciate your viewership and the valuable contributions you've made through your insightful comments. Thank you for watching! I’ll summarize some key/additional points that have been discussed in relation to Titan's failure: 1. *Understanding forces on the hull:* If we idealize the hull to a symmetrical cylinder, it is subjected to radially inward hydrostatic compression and forces transferred by the dome on to the hull (basically pressing the hull on top and bottom). As a result, any point on the hull is subjected to three perpendicular compressive stresses: (1) the longitudinal compression transferred from the dome in the direction of the axis of the cylinder; (2) radially inward compression (radial stress); (3) circumferential compression (hoop stress). 2. *Possible shear in the junction/bond between hull and dome:* Titanium and carbon fiber have different coefficient of thermal expansion (CTE). As a result, they contact/expand at different rates. This will introduce shear stresses at the junction/bond of the dome and the hull. Cyclic loading with such drastic pressure and thermal changes will have significant impact on the junction of the dome and the hull. 3. *Directionality of carbon fibers:* The carbon fiber composite material-comprising of carbon fibers and epoxy resin as the matrix-is an anisotropic material. That is, its strength depends on the direction of loading relative to the direction of the fibers. As observed in remark 1, any point in the hull is subjected to three compressive forces. If the carbon fibers are wound radially, the longitudinal compression and the radial compression acts perpendicular to the fiber, whereas the hoop stress acts parallel to the fiber. Although epoxy resists compression, the stress configuration would imply that the fibers should have been cross wound to provide stiffness in all the directions. 4. *Ignoring the possibility of damage after previous dives:* It was reported that OceanGate was aware of cracking sounds after the previous trips, but they kept operating. 5. *A structure is as safe as its weakest link:* Breach of hull by any means-including but not limited to crushing of carbon fiber, loss of contact between the dome or the hull, manufacturing defects, or crack in viewport-would have led to immediate implosion. Please feel free to comment here and I'll update the list. Thanks!

[@StoutProper]

Just to note that it is standard practice on subs to ensure your equipment is certified for +50% off your maximum diving depth. That is to say, you only dive to a maximum of 2/3 off the certified depth. So the Titan and all its components, insisting the viewport, should ideally have been certified to a depth of 6800 meters.

[@denfl6605]

@@StoutProper Certifying +50% off your maximum diving depth corelates to safety factors used in building structural engineering when ductile homogeneous materials such as steel are used because the behavior of such materials is very well explained by science, math is based not only on testing data but also by solid scientific calculations. When materials are non-homogeneous and/or brittle in failure, safety factors are so much higher. There are a lot of different products used in building construction that have safety factor of 5 simply because the only way to determine their capacity is testing in a lab. The fact that this sub is from carbon fiber, a composite material that has brittle compression failure means that the safety factors for this sub had to be a lot higher than typical +50% used for other subs manufactured from ductile homogeneous materials.

[@hagerty1952]

Regarding point #2, it's not just differential thermal expansion. The end rings were glued to the CF cylinder on the outside only. This is a terrible joint for pressure because Young's modulus (modulus of elasticity or distortion due to an applied force) is different for the two materials and that the CF tube would contract inwardly more than the titanium ring when under pressure. This puts the adhesive joint in tension in addition to the shear it was already getting from the rings being pushed towards each other from the pressure on the end domes (the two directions epoxy doesn't like). At the minimum, they should have used a ring thick enough to put a mating groove in it that would act as a socket to support the tube both inside and out, and from the ends. That would remove most of the strain problems with the glue joint, but do nothing about the buckling of the tube (think of squeezing a toilet paper tube between your hands). As others have pointed out, the mechanical properties of composite materials, like carbon fiber, are nearly impossible to model with any degree of precision. So much depends on how the test sample was made and how closely the actual device was fabricated to the test sample.

[@StoutProper]

@@denfl6605 good point but being as the carbon fibre was never certified at all and never has been for diving it’s a mute good point.

[@denfl6605]

@@StoutProper in building construction, carbon fiber strips are used for external concrete reinforcement when repairs are needed. Concrete is great in compression. So in this case, carbon fiber takes care of tensile loads only. I've never heard of using carbon fiber in applications when compression stresses control the design. That's why I was curious if there is any solid data for carbon fiber compressive strength.

[@simony2801]

The part about not needing certification at 11:00 because accidents within the industry are caused by human error and not engineering failures is like saying the certification actually is working really well.

[@LIONTAMER3D]

He was too stupid to see something so clear

[@edrose5045]

Yes I was about to say the same thing: structural failure is rare _because_ of the classification process, not despite of it!

[@whereisacbijustice-4ssrdis737]

THHHHis is huMan FAILURE FOR NOT,.TESTING FIRE FROM.ELECTRONIC TANGLEIN.FISHING,NEYT OR EXPLOSIONS..USALL.WITHTHE.LACK,OFINSPECTION,.SO WITH ENGINEERING FAILURES..;STOCKTON,RUSH,EMPLOYEES,, FIBRE N TITANIUM.DONT USE,IT,ITCAN.,LEAD TOOOO LDE-LAMIMATION,;*-##THEEEEE SEPARATION,OF FIBRE,LAYERS.. SEVERAL TRIOPS;BYCEO,STOCKTON,RUSH..IS TO TITANIC,CAN.LEADTOWEAR NTEAR.. OFTHE CARBONFIBRE,HULL,ANY,AIR,IN ITCRACKS AND BUBBLES CAN,LEAD.TO..EXOLOSION,IN,WATER..DONT USE RULE;- SCARBON FIBRE NOR NTITANIUM FOR HULL.;-THE DEOSAYS HE DID HEBROKETHERULES,,BECAUSEHETHOUGHT HEWAS ALWAYS RIGHT,.ANF THEN THE SUB,EXPLODE.UNDERWATER.. WENT.MISSING,COMMUNUCATION.CUT,.ALLBECAYSE OFTHE CEO CUTTING SAFETY CORNERSTO ,MAKE HIS CREATION THE MOST UNSSFE SUBMERMINE SUMBMERSIBLE EVER TO BE CREATED,ITRESUKTEDIN 5..MISSING,PASSENGERS,TOURISTS,,;- UNDER SEA.. INSTEAD

[@turbo_brian]

I mean, it's also because engineering has improved a lot over the years, but certifications and standardization definitely saves stupid people from themselves.

[@daemosblack]

@@turbo_brian yes engineering has indeed improved - and certification processes are in place to ensure that companies or individuals do not attempt to skirt around the cost of implementing that improved engineering because of cost cutting, failure to understand the dangers, blatant negligence, etc. Certification isnt for the engineers and designers, its for the buisness men and money counters

[@mikestanmore2614]

The most likely reason that most submersible accidents are user error, not material failure, is that every other submersible follows established design and construction methods. Changing the materials and construction voids that claim.

[@nitraM321]

yes, that's like saying, i can't drive, so i might as well make my car out of paper

[@cathybaldry7822]

This was more than user error Stockton engineered this submersible to fail.

[@jguenther3049]

A failure of logic.

[@Spamhard]

lol right. thats like saying "most planes crash because of user error, so actually there's no need to safety check them ever again, and actually we should just make them out of paper". Like. My guy, submersible accidents are mosly user error BECAUSE the risk of vehicle fialures have been minimised due to the regulations and safety checks you were so against, not in spite of them.

[@mikestanmore2614]

@@Spamhard "Submersible accidents are due to user error, not material failure. Here, at Oceangate, we plan to change that." 🤣

[@dorkf1sh]

I am reminded of my 13 year old self and my best friend. We built an "airplane" out of 2x4s and scrap aluminum tubes in my garage (mom and dad worked nightshifts in healthcare and were never home when we were building). We had it all planned out, rolling it out to the street to make sure the wings wouldn't hit the light poles and shrubs. We went so far as to go to the local municipal airport and talk and old mechanic into letting us take a worn out old wooden propeller as a "clubhouse decoration". Thank god my mom woke up early one afternoon to get ready for her night shift and caught us measuring the engine in her VW bug. She quickly got to the reason why we needed to know the dimensions and engine mount pattern and, for the first time in a few years, opened the garage to discover our nearly completed death trap. Dad was roused and quickly took an axe and saw to the contraption and we were grounded for the summer. I learned and grew out of such foolishness. Too bad for the Titan passengers and their families that Stockton Rush's mother never intervened when he was a foolish child.

[@whereisacbijustice-4ssrdis737]

Totally true..THIS IS A PERFECT EXAMPLE OF UTTERFOOLISHNESSIN CREATINGBA DEATH TRAP,FOR.OTHERS,IFRUSHS.MOM.STOPPED,RUSH,FROM,HUS CRAXY INVENTIINS.:-5PEOPLE WOULD BE BREATHING IN ALIVE ON THE EARTH AS THEY SHOULD BE,..WITH THEIR FAMILYSAND FRIENDS AND WORLD,.

[@ksmith1298]

Never happened

[@petrairene]

It's a miracle that this didn´t implode on the first Titanic dive.

[@mikestraley7201]

It's not a miracle at all period while the design was substandard and completely ignorant the material was strong enough To maintain integrity at multiple dives call my 13 is what I've heard That it made to that death corner that depth so no it's not a miracle 14 was the failing point

[@allangibson8494]

No - Carbon Fibre weakens with compressive cycling. Basically the pressure endurance halves with each load cycle.

[@apackofhoboes]

They say carbon fiber is at its strongest on its first go. After that, it only goes downhill.

[@budwhite9591]

Not necessarily. It could be good for one dive. It could be good for ten. He should have built an empty hull, and tested unmanned how many times it could go up and down until it pops.

[@allangibson8494]

@@budwhite9591 And operational testing showed it was good for 12. It failed on the 13th.

[@cassiemontgomery45]

I can't imagine taking such a drastic action, as building a vessel to go 2+ miles under water, without consulting with as many expert engineers as possible. Also, I'd conduct rigorous testing too. All of this can take years. I don't understand why Stockton Rush didn't do all this. He truly could have been a pioneer in safe deep sea diving if he had. It would seem he was in a rage to prove other engineers "wrong ". I'm greatly saddened that he took 4 others with him on this suicide mission.

[@doctorchadha]

Absolutely. Truly unfortunate and a preventable tragedy. The margin of error here was too narrow.

[@roystonboodoo7525]

Scriptures... Wisdom comes with having many advisors.

[@crackerjack5210]

Exactly!

[@kathykarns9829]

Probably nobody would ever certify such a system. There would be little precedent. Metals simply do not have the problem of air entrainment. But maybe someone tried and simply couldn’t certify. It’s like trying to fly. How?

[@wandanorthern8706]

It was about the money I'm thinjing

[@jungbrahs1379]

I’m obsessed with this incident. Thank you for the engineering education 😊

[@Leo-fk9ch]

I use structural engineering software on a daily basis, the software acquires its immense database of materials from several cloud based sources. I can test virtually any shape, material and a multitude of loads. Ocean Gate no doubt had access to the same engineering and modeling software. In my case, when I learned of the Titans general construction, after the accident, I ran several models based on its design. Watching videos of its construction, I was able to input all of the variables such as weave versus linear layup as in the composite construction seen in Titans case. In order to simply endure the pressures encountered at Titanic’s depth, my software dictated a weave layup and a hull thickness of 447MM or 17.6 inches. Far less than the Titans 5 inches . Further, and most alarming were the results when considering dissimilar end cap material. The different expansion and compression rates of composite against ( bonded ) titanium are substantial. Using the software, I noted failures exceeding 1MM, which would inevitably cause failures at the seams. All of this data in less than 8 hours, using widely acceptable and certified software. I’d conclude that Titan was doomed to catastrophic failure. I’m concerned that the data was known to its engineers and certainly the owner. My only guess could be the huge expense of the build outweighed terminating the dives in sake of safety. The price of an ego and profit/loss.

[@Leo-fk9ch]

I made a wording mistake, with regards to hull thickness. It should read that 17.6 inches is far more than titans 5 inch thick hull.

[@allangibson8494]

Titan didn’t use a woven carbon fibre hull - it was wrapped in unidirectional carbon fibre that was simply spooled onto the 6mm titanium hull.

[@MrShobar]

"...Ocean Gate no doubt had access to the same engineering and modeling software...". Why would you assume that?

[@weirdwes6725]

​@@MrShobarbecause any competent engineering company would.

[@amadablam8229]

@@weirdwes6725ocean gate was not a competent engineering company.

[@christopherlatham4254]

As a structural engineer the other potential problem I see is that the carbon fiber cylinder and the titanium end caps have different coefficients of thermal expansion. In addition to the pressure cycles on diving there were temperature cycles which put extra demands on the adhesive bonding the two materials together. Humanity got very lucky that concrete and steel have very similar coefficients of thermal expansion or reinforced concrete wouldn't work.

[@TheScotsalan]

I thought that too, and when I googled thermal expansion for carbon fibre, it turns out some CF composites have an opposite thermal expansion. So just by sitting in a non temp controlled room, its undergoing cycling stress.

[@Cam-ng8rk]

The two elements would also have a different stiffness due to different geometry and material. So you would expect this to cause large shear forces across the connection at this depth, as each element wants to deform a different amount.

[@TheScotsalan]

​@@Cam-ng8rkYup. If anything, this has got me thinking beyond my classic engineering training. I did not go a high enough level to know if there is a poissions ratio for compression. I done Lames equations, but this is the opposite. 🤝

[@jcjust1160]

Like - wow. Never thought of concrete and steel - humanity got lucky, Thanks!

[@LadyScaper]

As someone who knows nothing about engineering, that is what I thought too. Where the Titanic is, it’s around -17°C I think? The CEO said he wanted to expand to visiting hydrothermal vents? These two temperature extremes at such deep pressures, contrasted with the surface temperature at the the beginning of the dive, just didn’t make sense to me. Anyone who lives in a place with 4 seasons will notice their doorframe slightly contract unevenly during winter. That would wreak havoc on a submersible made of multiple materials. Stockton was incredibly foolish, but he thought by financially cutting corners, he could “innovate” and sell to his true customer, deep sea oil/gas and the developing industry of deep sea mining (😱). Coping with both temperature fluctuations and the pressure fluctuations is just more expensive then Stockton was willing to acknowledge. The more it cost, the less attractive to his future main customer. Greed & denial superseded his scientific education and did him in.

[@iamamish]

"While accepting unforeseen risks is a part of life, ignoring foreseeable risks is not only foolish, but also unnecessary" - 100% I'm a huge fan of innovation, but typically when people innovate in a dangerous environment, they take safety even MORE seriously, since they already have their hands full with the problems they didn't anticipate. Why let the problems you can anticipate be a problem too? Stockton's commentary is so arrogant. Very nice breakdown!

[@MrShobar]

Applies to the hijinks of Elon Musk as well.

[@yakuza01]

Yeah, I am definitively stealing this to argue with all the simpletons calling this maniac (Rush) and 'innovator' or 'pioneer'

[@listerdave1240]

@@MrShobar It doesn't seem to me to be the case at all. Musk has an entirely different approach to engineering and in particularly safety compared to Rush. I don't see any parallels at all except that they both claim to be innovative. However while one really is other is just reckless.

[@iamamish]

@@yakuza01 well unfortunately he was both, just not in the way you might want to be 'pioneering'

[@Minimojojoy]

Well said! And it would be different if Stockton had only been risking his life. But using an experimental vessel for tourism is just astoundingly ridiculous! Unless these people were proper deep sea experts they just couldn’t understand the risk they were taking. Especially when facing Stockton’s arrogance and delusional confidence in his vessel. His level of narcissism was just, infuriating. I’m fairly certain he’d at least be facing involuntary man slaughter charges if he hadn’t been in his vessel. Even if the guests signed a waiver there was clearly many undisclosed facts and risks.

[@pdubsweir3]

You make excellent points. I would also add the fact carbon fiber and titanium are notorious for galvanic corrosion when placed together. Boeing knew about this issue while creating the carbon fiber composites for the 787. They had to separate all titanium parts away from the carbon fiber wings and hull. The Titan had two titanium caps and interface that sat right against the carbon fiber hull. .

[@geoffreycodnett6570]

Carbon fibres would have been out of contact with the titanium parts if the epoxy was properly applied to the connector rings. This appeared to be the case. The idea that RMS Titanic continued head on into an ice field isn't correct. She changed course to the south after being informed of the presence of ice on her original course. Statements need to be accurate when criticising actions as comparisons.

[@pdubsweir3]

@@geoffreycodnett6570 Arguably everything is speculation at this point. I still stand by the fact carbon fiber and titanium are galvanic corrosive. Even if epoxy sealed, laminations can get micro-fissures or cracked over time and many cycles of compression and decompression. Plus the salt water can act as a conductive medium to accelerate galvanic reactions.

[@emitindustries8304]

Rush should have only been allowed to have a sub stuffed with turkey, ham, lettuce, pickles and and mayo (hold the onions), not people.

[@j81851]

Absolutely clever and correct!

[@malcolmwhite6588]

Ha ha very clever you😂

[@ZilogBob]

"Give me Hamm on 5, hold the Mayo".

[@karlschauff7989]

A friend of Stockton Rush that had been on Titan for one of the dives said in a recent TV interview that they could hear cracking noises as they made their descent.

[@chemech]

Creaking and cracking noises in a submerged vessel are "normal" due to the major compressive stresses being experienced. That is why you use a metal material - such as a pressure vessel steel alloy, or titanium - and design to remain in the elastice portion of the stress - strain properties. A brittle material has no plastic or ductile deformation characteristic, so you go from an elastic - linear deformation due to stress - directly to ultimate failure... do not Pass Go, do not collect $200-

[@pbxn-3rdx-85percent]

"What's that crackling sound? Is this thing really safe?" "Don't worry. It's just our pork rinds snacks I tied outside the hull."

[@nyki7fykxtjxyi]

It would be interesting to hear an audio recording in that thing during a dive.

[@PInk77W1]

@@chemechbut they collected $250k. A piece. Yikes

[@jcjust1160]

@@chemech You guys are such "geeks" - love it!! Thanks for sharing. Learning, considering - curiosity - need more of that. Blessings

[@nonmihiseddeo4181]

(12:26) Boeing, University of Washington (UW), and NASA have refuted Rush's statement that they worked with OceanGate on Titan.

[@doctorchadha]

Oh wow. In that case, it was irresponsible and misleading to make such a comment in the interview.

[@MrShobar]

@@doctorchadha The UW Applied Physics Laboratory participated in the design of a smaller, all metallic submersible for Rush ("Cyclops 1"). It was designed for a depth of only a fraction of that attempted by Titan. It made numerous successful dives, including to the wreck of the Andrea Doria and to the bottom of the Puget Sound for marine life studies. It is still in existence today. The UW-APL has issued a public statement that they played no role in the development of Titan. Boeing sold some expired prepreg material to Rush that could not be used in aircraft construction. Rush was unconcerned about using the expired material.

[@chemech]

@@doctorchadha Quite possibly fraudulent...

[@quinn4091]

He exaggerated his reaching out to them to ask questions as "working with them". The passengers probably thought Titan was somehow "approved" by Boing and NASA and trusted their lives to Rush, since he "played with the big boys"... After this tragedy I think NASA, Boing etc. must sue EVERYONE that claims misleadingly to work with them.

[@tamara6212]

It's all lies based on what these entities have stated. None of them had any involvement in his goofy "submersible ".

[@elennapointer701]

I think the worst aspect of OceanGate's design philosophy was the defensiveness of it. Every time Rush was called out for some decision he made that either cut a corner or violated a safety norm, he seemed to get angry about it, as if he was thinking "how dare these people question me?!" It's the kind of hubris that often leads to disaster. If you can't handle peer review, frankly, you're in the wrong line of work. Thank-you for this excellent explainer of the mechanics behind this tragedy.

[@lazerathhome]

The Structural Issue was the Seal between the Carbon Fibre Hull and the Titanium Circular Base the Titanium Hatch with View Window Bolts too. There is an Excellent video showing the Construction of that point and how the two peices are GLUED together! The Video/Photos of the wreckage shows how that section litteraly pulled itself apart. It looks like Carbon Fibre Spaghetti. Carbon Fibre is very strong but it is Extremely weak to break down if it is compressed and relaxed over and over. Which is what happeneds when you submerge it so darn deep in the ocean. The likely second option for the failure is the window if it truly was only rated for 1200m depth. My bet is on the Titanium and Carbon Fibre Seal as the initial fault! Metal can flex to a small degree before it succumbs to the pressure. CARBON Fibre with Glue ends up Cracking. Thats why it should NEVER be used as a Pressure Hull. That man was NOT a Genius or Extremely Intelligent. His Actions Prove the complete Opposite! Proving once again that just Because you are very wealthy doesnt mean you have a Lick of Common Sense!!

[@LadyScaper]

Yeah, probably his wealth helped him ignore his weaknesses. Any consequences while growing up could be easily be made to disappear. The laws of physics does not care about any of that though. That’s was Stockton’s greatest mistake, which he probably was never going to learn. I fell sorry for the families involved as they didn’t sign up for the risks. :(

[@jcjust1160]

@@LadyScaper true and kind

[@marilynevans8436]

If he was that wealthy, he didn't need to skimp on any of it

[@johnvanalstine9645]

The website talked about the hull monitoring system that would give the submersible real-time warning of any problem so they could then head for the surface. Unfortunately it appears the first sign of a problem is immediate implosion and death. No time for surfacing.

[@possumverde]

Actually, I think it was an attempted emergency ascent that caused the implosion. The runners they brought up showed little to no sign of damage. Due to how they were attached, they should have suffered very clear damage were they attached when it imploded. That tells me that he had time to initiate the emergency ascent protocol since dropping the runners was to only be done in an emergency. It wasn't needed for a normal ascent. The problem with an emergency ascent like that is that it temporarily increases the forces acting on the hull. You go from the water pushing down on you very hard to it doing so while you're essentially pushing back very hard due to increased buoyancy. So, if your hull is close to failing and you then do something that increases the stress upon it, it's probably going to fail. He probably heard the system warnings and overreacted by initiating a full emergency ascent. They would likely have imploded either way but a more gradual ascent might have given them a better chance of survival.

[@johnvanalstine9645]

@possumverde oh that's interesting. I didn't hear such specific info on the condition of individual parts. Is that in this video or where did you hear that? And what do you make of the hull monitoring system? Could it actually have provided enough warning of an increase in strain in the carbon fiber to make an ascent possible?

[@johncummins3860]

Sounds of cracking were the early warning alarms but they were ignored

[@ZilogBob]

@@johnvanalstine9645 Mr Rush held Patent number US 11,119,071 B1 for his hull monitoring system. If he applied as much care in designing it as he did to everything else, it's hard to believe it would have been very effective.

[@boeingdriver29]

This was amateur hour in the deep sea diving arena. These wealthy guys could have ordered a Triton 36,000/2 for 40 million and safely dove on the Titanic as many times as they liked. It makes no sense.

[@j81851]

Excellent comment and prudent advice. Cut corners on the surface....maybe. Cut corners at a few hundred feet down.......eh.... maybe. Cut corners at 12,500 feet ABSOLUTELY NOT! Excellent video, knowledgeable, personable presenter and absolutely great content! One of the best written, organized and presented videos on the topic I have watched since the tragedy. I subbed immediately and hope for more content. You are a joy to watch, very pleasant and have a great presence on camera, And as I said the content is five star quality! Bravo give us more I'll be back!

[@happyvocal]

I thought he only decided to make his own submarine after he could not buy one on the market? I wonder what exactly led him to reject one of their submarines.

[@elipotter369]

​@@happyvocalI read somewhere else that a sphere is the best submersible at depth, and the size takes one paying passenger. It's not profitable enough. Rush made a tube and wanted to make money.

[@jcjust1160]

@@j81851 Agreed! and with kindness to boot

[@kevinmyles6369]

@@j81851 exactly what I was thinking all the time! How the hell can you cut corners when doing a 4km dive for crying out loud!?!? Totally insane, immoral really!! Carbon fiber hull did survive 6 dives but apparently worn out fully when they went for this very last dive. Rush should have known better and now he's dead with 4 others! Tragic.

[@BabaWaba]

Earned yourself a sub with such a clear explanation of extremely complex scientific topics.

[@doctorchadha]

Thanks for watching and subscribing :)

[@darthwader4472]

Pun intended?

[@lawrencehalsey4149]

@@darthwader4472 Hahaha, you beat me.

[@jamesn3513]

Radial compression and longitudinal compression of the end of cylinder area. Poor epoxy resin didn’t have a chance with repeated 300-400 atm compressions.

[@chemech]

The join of the cylinder to the titanium ring flange at both ends was also of a slip-on joint, held only by the epoxy adhesive, with not provisions to resist tear-out.

[@jamesn3513]

@@chemech I agree. The differential in strain between the carbon fiber and titanium ring most likely created a large shearing force.

[@davidhowick3665]

The mating surface of the titanium and carbon fibre appears to be several inches only , not even a tapered join, such incompetence on the most basic of joints

[@32mybelle]

I heard that he was obsessed with Captian Kirk, but Kirk always put the safety of his crew ahead of his own. "The needs of the many outweigh the needs of the one".

[@LadyHeathersLair]

Which is a Spock quote, but I get your point.

[@isabelmauricio6394]

Captain Kirk was a fictional character. 🤷‍♀️

[@user-ih9dg3uz5y]

Captain Kirk was a Heroin addict

[@benjamincarr9233]

This tragedy could so easily have been avoided. Thankyou for your clear, calm explanation of the factors involved. I see that this is a new channel. You have gained a new subscriber. Keep up the good work and all the best for the future!

[@thedbcooperforum]

The sub was doomed from the start and Stockton was Destined to die in the sub, the avoidable part is allowing passengers to die with him..

[@wandanorthern8706]

Ditto that

[@user-ih9dg3uz5y]

It could never have been avoided ok

[@thedbcooperforum]

@@user-ih9dg3uz5y everything is avoidable, ok..

[@bowlampar]

A responsible 'extreme deep ocean' tour company will inspect thoroughly every inches of a safely returned manned-submersible's structural integrity before the next trip into the unknown danger zone again.

[@southpark4151]

To sum up - it's basically breaking of many golden rules of engineering and safety. They could have also saved ending up in tears by spending money and having the submersible dive unmanned down to 4000 m depth about 100 times. And do that for a few of their submersibles - all produced in the same way. If after 100 dives each - with no problem, then at least you can have 'some' confidence.

[@chrisehmke1651]

100 is really a large number. NASA puts astronauts on a new rocket when it has been flown unmanned 2 or 3 times. But they do a lot of ground tests too.

[@southpark4151]

@@chrisehmke1651 True! And also -- at least NASA engineers 'mainly' get it right. Except for example the O-ring debacle, and the loose foam/tile debacle.

[@andyharpist2938]

The end cap pressure on the ring were immense. The inward, cylindrical forces ( at 90 degrees to the end cap pressures) were also huge. These two combined together on the face of the carbon fibre at the joint with the titanium. At a point where there were differential strains ( movements) between the two materials, that had been simply glued together.

[@user-ih9dg3uz5y]

The pressure on my ring in the morning is f......kin immense too. I crack off some loud fat farts phew!!!

[@georgiosvergakis5666]

Conclusion, only the Wrights would have made it right, the Rush always rush, family name is important

[@stlaw08]

Sadly Stockton Rush was too personally invested in his Titan submersible to be impartial & professional.

[@DBCuzitis]

I believe the c.f. tubular body will end up being the failure point. All implosion testing I’ve seen (Mythbusters e.g.) tubular vessels (tanks, water heaters, liquid rail cars) all crush in the middle when the air is sucked out of them. The titanium end caps were rounded and probably fine but they’d put a inward pressure on the c.f. tube. The ends of the tube were the only place given any support because of the titanium end caps. The middle of the craft is the least supported area and the most likely to fail I think. The viewport window rating included a safety margin which is what I think S.R. counted on. He used its safety margin as extra depth - scary. I think if the viewport failed we’d find more of the body of the vessel intact which is why I think the c.f. tube failed first.

[@davidhowick3665]

Safety factor of 3 …for the window …oops run out of factors

[@johncummins3860]

Would a metal inner support ring installed in the middle of the carbon fibre tube have helped ?

[@doctorchadha]

Thank you for watching! Like and Subscribe for more! 🫡

[@afriedrich1452]

All videos, including this one, are missing the point about compression. @ 4:26 That way of testing compression strength is not applicable in Titan's case. Are you smart enough to tell me why? I am tired of repeating myself.

[@doctorchadha]

What you see at 4:26 is uniaxial compression test. My goal to incorporate that clip was to demonstrate "brittle failure" of carbon fiber under compression. It is certainly not a way of testing for the compressive strength of Titan. The stress configuration of an infinitesimal element in a pressure vessel is certainly not uniaxial. The carbon fiber is an anisotropic material and its compressive strength (usually measured by uniaxial compression test) is different if the load is applied parallel or perpendicular to the fibers. The two most important component of stresses (for simplicity, imagine an elastic hollow sphere subjected to hydrostatic compressive stresses) in submersible are radial stress component which has value of hydrostatics pressure at the outside of the vessel and 0 at the inside; and then you have tangential stresses. This stress configuration is very different from the stress configuration in uniaxial test. I am pretty sure that uniaxial compressive strengths (in parallel and perpendicular direction of fibers) are useful parameter to be considered for the design but a complex structure like titan needs a high fidelity finite element model to study the stress fields and investigate things like effect of pressure cycles on fatigue, and effect of manufacturing defects by introducing random defects in FEM model and performing monte Carlo style simulations. Please let me know if I missed something. Thanks!

[@CalebAchsah]

@@doctorchadha - I have no idea if you missed anything at all, but I just subscribed. Thank you for elevating KZbin with your presence!

[@fionamackie3357]

​@@afriedrich1452did you get your question answered? Or are you the same kind of arrogant as Rush?

[@xraylife]

@@afriedrich1452 If you were really smart you would have figured out that it was a False 🏴‍☠ by now.

[@Xan3119]

Thank you for being a voice of reason, it makes me sad to listen to that Madman Cackle on about safety being worthless. The hubris. Thank you for being a voice of reason

[@LadyScaper]

The thing is, lots of people and lots of CEOs in multiple industries think safety is worthless. Look at the train industry and East Palastine. Cancer Alley in Mississippi. Just in this case, it’s so visibly obvious to the public there is nowhere to hide. (And no lobbyists to help with the hiding.)

[@momv2pa]

Your detailed explanations on everything, in particular the construction of the Titan, really helped me understand. This was a terrible tragedy and so completely preventable. Brings tears to my eyes and raises the hair on my arms. RIP to those lost, and sending comfort and prayers to their families and friends.

[@CarolReidCA]

Thank you for your explanation. There were problems with some of the materials used, the engineering, the communications between divers and crew on a test dive to 33' weren't worked out beforehand, the "research" that was supposedly taking place (which was absent), and their seemingly simply lying to their passengers. They had many, many who allegedly warned that the Titan was likely to have a serious to catastrophic failure. Sadly, they seem to have fired and then sued the 1 engineer who had any sense. That lawsuit shown was against the engineer and his wife that they seemed to have fired. OceanGate was the plaintiff on that document. Unbelievable, and not only a senseless loss of life, but perhaps damage to the submersible industry doing actual deepwater work, research and exploration as well. The coming regulations will tell. Hopefully those following the safety protocols won't be adversely affected by new regulations because of this company.

[@donaldcarpenter5328]

According to the resin thats LEFT on the titanium end cap/door it DID debond as well as delaminate

[@chemech]

I've been hoping to see such evidence - based on my experience with adhesives and the difficulty of bonding to metal, especially a smooth machined surface, I fully expect to see such failures of the joins.

[@kukipett]

As a professional since 40 years in composite fabrication i would say that your explanations are very well done and accurate, that's the first time that i see an expert that seems to really know what he talks about about this accident.

[@mgkeoh]

Well said. This has been the best video I have seen on this fatality.

[@doctorchadha]

Thank you for your kind words!

[@kukipett]

@@doctorchadha There is suddently one thing that just went on my mind, it's the obvious flaw of the design and the flabergasting way the cabon cylinder was build. To make it simple, you have a cylinder with two hemispherical caps. So each cap press againts the tube ends with the pressure of the cross section, but the contact surface is from my estimation only 20-25% of the cross section so at 4000 meters you have on the tube ends a pressure of 4 times the pressure on the tube sides. But what is really idiotic it's that the cylinder has been fabricated by roling one directional carbon fiber. In this way you achieve the maximum resistance to side compression, but you have no resistance in the tube axis direction. Worse you have a huge risk of delamination in that axis and even worse at the tube ends, you have 4 time the pressure and no resistance in that axis. This is insane, you have only the matrix, epoxy resin that can absorb the pressure and in this way that resin will get a quick fatigue, will start to have cracks and become brittle. Then one day the tube ends will collapse and the whole tube will shatter. This design was made to fail, i don't know how there was not an engeneer to point to that huge fatal flaw!

[@doctorchadha]

Absolutely. Assuming the structure to be symmetric about vertical axis of the cylinder, every point on the hull was subjected to three compressive stresses: (1) the compression from the domes in z-direction; (2) the radial compression; (3) the circumferential compression-thats too much work for epoxy. And apparently, the fibers were not cross-wound. I would also think that the stresses coming from titanium dome on to the cylindrical hull could lead to local crushing due to stress concentration at the junction.

[@kukipett]

@@doctorchadha Yes the major flaw is that the carbon fibers have been rolled on the cylinder, there is a video showing the building of it. Usually you make a cross.wound at 45° to give the cylinder a homogenous resistance but of course to get the same resistance in one axis you need to make it thicker, so heavier and less space in the hull. I have build quite often small carbon cylinders and if you just roll the fiber like this, if you try to bend the tube it will break very easily. Making a pressure resistant tube the way they did it is absolute madness!

[@randystraub3012]

This is a very sound structural analysis overview relative to the Titan submersible and rightly highlights some questionable judgement used by the designers. Christopher L also brings up some good thermal expansion considerations. Thank you!

[@philiphusband2860]

This is the best analysis of the design faults of the Titan I have come across. I fully agree with you regarding the inappropriate use of carbon fibre as a component of the pressure hull; all I would add is that the differential rate of deformation under pressure at the interface of the CF cylinder and the Ti hemispheres might have led to the extreme shear forces that ultimately caused the pressure hull to implode after repeated cycles of exposure to 380 atmospheres of pressure.

[@nbrown5907]

Someone needs to verify the viewport claim. Everyone is quoting one source, what does the manufacturer say or we don't know who made it? If it as true then the accident was absolutely negligence right there. The carbon fiber not being fully tested also negligence I would think but I am just an observer.

[@simony2801]

I would assume the viewport’s low rating is an error, such an oversight would be unforgivable. It’s so silly it must be wrong.

[@MGJDMNJ]

Thank you for the amazing explanation on a deeper level than others. I’m not an engineer but this was super easy to follow

[@JohnHansknecht]

Wrap string around a balloon on all sides. Pressurize that balloon. It will hold pressure quite well. Now apply pressure to that same balloon from the outside. Totally different story. The string is not under tension anymore.

[@coolcat23]

It seems the main structural integrity was provided by the epoxy (and the inner Titanium hull). It seems obvious that Stockton's "design" might work a few times but was inevitably going to fail after some cycles of compression and decompression. That's not even taking the different material mix at the end caps into account. That was another accident waiting to happen.

[@RockandRollWoman]

​@coolcat23 I don't believe there was an inner titanium hull, but am willing to be wrong. Source for that?

[@coolcat23]

@@RockandRollWoman I tried to find the source, but failed. Maybe it was just an inner Titanium cylinder with no structural role, i.e., not technically part of the hull? I remember that it was much thinner than the carbon fibre hull but, unfortunately, could not find the source again. It seems obvious that they must have wound the carbon fibre around some cylinder; I believe the source I read referred to this part.

[@RockandRollWoman]

@coolcat23 Thanks for looking. The following from today's New York Times isn't related to the hull, but it's worth 5 minutes of reading time: "Bill Price ... went on a Titan dive in 2021. During the descent, Mr. Rush realized that Titan had lost its propulsion system on one side. He aborted the trip, Mr. Price said. But he could not get what he called the “drop-weight mechanism” to release ballast for the ascent, as designed, Mr. Price said. [In a prior video interview,] Rush had explained the ballast system, which included six 24-inch sewer pipes that weighed 37 pounds, “and we dump that pipe, one by one.” Mr. Rush calmly explained that the weights were loaded from the top with no stopper - so if they could rock the submersible enough, they would drop off. Everyone lined up in a row, rushed to one side, then the other, back and forth, to tip the Titan and dislodge the ballast, the way someone might rock a vending machine to free a candy bar stuck on a spindle. “After several rolls, we got momentum going,” Mr. Price said. “Then, we heard a clunk, and we all collectively knew one had dropped off. So we continued to do that, until the weights were all out.” None of this prevented Titan from making a dive the next day." New York Times, 2 July 2023. I have few words to add. The level of absurdity is unbelievable.

[@PurposePlastics]

Great production quality and enlightening discussion. Earned my sub

[@MaartenVisser2920]

Boeing and NASA have refuted Rush's statement that they worked with Ocean Gate on Titan. I think Rush lied, but tried to explain why the Titan had a so much similarities to the Spaceshittle and the 737 Max.

[@t-rex4211]

Yeah, Boeing did help design its predecessor though but apparently to save money they copied that design but altered it….without it being redesigned by Boeing

[@MrShobar]

The UW Applied Physics Laboratory has also disclaimed any responsibility for the development of Titan.

[@geoffreycodnett6570]

Proved exactly like the Spaceshittle and 737Max so Boeing certainly gave a hand!😂

[@MaartenVisser2920]

@@t-rex4211 Just like the Max......

[@t-rex4211]

@@MaartenVisser2920 oooh what happened there?

[@fjordking]

Let's see a carbon fiber tube with epoxyed titanium ends with no prototype destructive testing to even know how many cycles it could take, well he found out it was six

[@chemech]

And he was cheating death for at least three of the previous cycles.

[@paulinemegson8519]

The likelihood of a defect in the carbon fibre component was exacerbated by the fact that the “pressure vessel” of the veh was created by a spooling technique, rather than using a mesh construction, meaning a linear weekness was built in, and the wrapping was done in the air, instead of under a vacuum which is commonly done in cases where strength is an issue(under vacuum, the likelihood of an air bubble inclusion would be minimised) Add to that that Rush boasted that he’d sourced “expired for aviation use” carbon fibre from Boeing at a discount.

[@larrybud]

i love how all the experts only come out after the fact. Love to see ONE video where someone was ringing the warning bell BEFORE this thing imploded.

[@methylene5]

Underrated comment.

[@darthwader4472]

By now, we have seen the first pieces of the wreck having been recovered. It looks like the titanium dome has separated from the ring section. Any idea how this could have happened?

[@doctorchadha]

I can only speculate at this point and we would know for sure only after the results for investigation are out. However, if I were to bet, the failure occurred at hull. It initiated with a crack, that leads to loss of strength and stiffness, followed by redistribution of forces, followed by further growth of crack, and then implosion. Once the hull imploded, the titanium dome (almost a rigid body) simply separated. Imagine if your place an empty plastic coke bottle and crush it very quickly with your feet, the bottle will get crushed and the top cap would simply fly away.

[@TeemarkConvair]

@@doctorchadha notice the lift strap on the forward dome was THRU the missing viewport,, ?important?!

[@doctorchadha]

Interesting. It could have been the viewport as well. Lochridge lawsuit indicated that viewport was certified for 1300m only. Thanks for pointing that out.

[@darthwader4472]

@@doctorchadha Well, by "ring" I mean the titanium section, NOT the carbon cylinder. The hull has (had) five major parts: the two domes in each end, one of which functioning as the door, two rings, also metal, I assume titanium, and finally the carbon fiber cylinder in the middle. The carbon was glued to the rings, but the domes were screwed. Why would those be pulled apart when the pressure equalized? What force would rip 17 bolts? This is weird...

[@allangibson8494]

Implosions generated very high temperatures and pressures inside as the all the components of the vehicle ignite (like a diesel engine). Anything not designed for positive internal pressure will blow off (like the view port).

[@ibzilla007]

Great video. Appreciate the in-depth explanation into the engineering.

[@doctorchadha]

Glad you enjoyed it!

[@alanmorrison3598]

No many things do not have to go wrong! Just ONE thing!! As an example, if the plexiglass window in the metal end bell failed, that ONE failure would cause the submersible to fill with ocean water in a small fraction of a second taking the lives of all on board! Indeed the window was missing from the end bell when found and the window was not rated for the pressure involved! 0:22

[@anoramba]

Really great breakdown. This video deserves more views.

[@advaitkottary]

From one engineer to another, this is a fabulously explained video. Well done mate.

[@rosean374]

Also. What is the role of the engineers and employees when they know such unstable and dangerous vessels are being used by unsuspecting public. If you dont raise the red flag loudly enough and you allow innocent people to die you are also contributing to their death.

[@doctorchadha]

Truely unfortunate that even the red flags that were raised were either ignored or suppressed.

[@Leo-fk9ch]

I have been in situations where, as a professional licensed engineer, I have been exposed to unsound and or unsafe designs. All of which concerned people carrying vessels. I have alerted other engineers on the build team, management and govt representatives. The bureaucracy and red tape to effect change can often be insurmountable. Often leading to little change. Shouting unsafe is not enough, especially when tens of millions are at stake. The 737 Max comes to mind.

[@chemech]

Sadly, they do not seem to be teaching the Engineers Code of Ethics in undergraduate programs these days... probably not in graduate school either. As a licensed Prtofessional Engineer, I had to sign up to adhere to that Code as part of my licensing application. However, as this was a commercial application intended for international waters, there does not seem to have been any active effort to require OceanGate to employ the services of a PE, most critically a Mechanical Engineer who specializes in pressure vessel design. Also, the fabrication of the carbon fiber cylindrical segtion of the hull does not appear to have been conducted by an ASME certified pressure vessel fabricator's shop. While the late Mr. Rush was reportedly educated as an engineer, his actual engineering experience was rather limited, and did not extend into the arcane world of pressure vessels. His hubris and disdain for the opinions of the experienced professionals killed him, and sadly, four other people.

[@Syclone0044]

A great video case study involving this is the thrilling USCSB video on an Illinois synthetic quartz crystal manufacturer. They had 8 huge tall pressure vessels and a consultant saw red flags galore and sounded the alarm. The company did nothing and it exploded catastrophically killing an innocent motorist on the nearby highway!

[@outlawswwmc4059]

My heart goes out to the families. My condolences to each of them.

[@nancyfarmer4289]

I love your shelves! Thanks for the video. You have a wonderful way of presenting technical info to the interested layman and non-scientist. I appreciated the diagrams and documents .

[@doctorchadha]

Thank you 😊

[@Fido-vm9zi]

Love all the tech information, learning & thinking about future industry. Thank you!

[@jigyasumalhotra]

Great explanation 💯

[@rosean374]

I wish we could have more engineers like you in America.

[@doctorchadha]

Thanks for your kind words!

[@jpcaretta8847]

The US priority nowadays it to produce lawyers, mba, politicians , social pseudo science and other arrogant, greedy , stupid scumbags. Add woke, affirmative action ... et voila ! You cant tell an idiot he is one, fire him, as it offends him.

[@chemech]

We still have a few, and I hold out high hopes for my junior colleagues to succeed in spite of the sadly deficient state of engineering education ever since the Tax "Reform" Act of 1986 took full effect in the US in 1990, destroying industrial R&D funding and thus industrial experience among the PhDs who went on to become professors. The students still crave getting good instruction, with healthy doses of experience from their instructors... it is truly sad to see how our government is letting them down in this regard.

[@Still-Sitting]

Great work, sir! I’m hooked on learning as much as I can about this tragedy, and appreciate you sharing. Awesome video

[@pilotdane]

Thank you for a informative video that avoids much of the sensationalism and focuses more on the engineering of such a vessel.

[@youtux2]

Incredible :( A Darwin Award in engineering, sadly.

[@stargazer5784]

Natural selection at work.

[@psul42]

This was a very balanced and informative presentation. Well done.

[@CECE1839]

Excellent, explanation and breakdown of a very tragic situation…😢

[@MJSmithGroup]

Wouldn't it be funny if they recovered the game controller and it was still intact and fully functional?

[@gabrielleangelica1977]

🕹️! Here it is...

[@ZilogBob]

Logitech stuff is very well made. I'm typing this on a 20 year old Logitech keyboard.

[@RobertPaskulovich-fz1th]

Nobody has any basis to doubt any aspect of Doctor Chandra’s veracity.

[@cayrick]

The best, most concise and intelligent analysis I have seen on this terrible accident. Very will done and excellent explanation. The one option that had not entered my mind was buckling of the cylinder. I learned a lot from yoru explanation. Thanks! Will have to wait until the experts in the bureaucratic agencies pour over the wreckage and data for a year or so to get the actual cause. 😊.

[@Kalense]

Excellent video, very well put together, really intelligent analysis. Thank you.

[@bEEBO178]

Very interesting. Thank you for this! Very well filmed and narrated. This vessel was doomed from the beginning. Let this be a lesson for future development. RIP to those who paid the price with their life.

[@keeperofthegood]

Composite materials are great building materials. I think Airbus has been one of the biggest developers/innovators of it and its use. And of those uses, they use it for the non-pressure systems. Wings and spars. Not for structures that are pressurized like the skin of the plane. Got to think they may know a reason why eh ;) (HEY Folks, thank you for the information below, I reviewed use for the carbon fiber composite in Airbus and all detailed on the A series indicated aluminum skin, and the primary use in wing and spar. Compression v Tension v Shear will likely be a big topic over the course of this event.)

[@thinking-laaf]

and EVEN Airbus had delamination issues and crashes.

[@keeperofthegood]

@@thinking-laaf Oh for sure, it was a new technology and real world extended use hadn't happened. Lab testing can only get you so far. Between Airbus and NASA, failure analysis and material use understanding today is far richer than back when they started in the 1980s.

[@Gumbatron01]

For an airplane, carbon fiber composites would also be suitable for pressurized sections, because the pressure is a positive pressure, the skin is in tension. A submarine is the opposite, all of the pressure is compressive. The compressive strength of carbon fiber is ~0. In the submarine's case, the compressive strength was provided only by the resin that bonded the fibers together. It was always going to fail.

[@jpcaretta8847]

Fine fir the fuselge as it is pressurised, just that pressure cycle has to be considered. Vessel for high pressure gas make good use of weaved carbon fiber where it excels

[@allangibson8494]

The 787 uses a carbon fibre fuselage. The carbon fibre is however loaded in TENSION not Compression. Carbon Fibre is incapable of handling compressive loads - the epoxy matrix does all the compressive load handling.

[@manjsher3094]

Hello Dr Thanks for taking your time for this content. Thought out, concise and understandable. I subscribed because of your potential energy.

[@PugFaceMedia]

As a NASA-inspired engineer, I can say that the symmetrical rate of the expansion coefficient would counteract the molecular bond of the atomic structure thereby expanding the ionic energy further amplifying exponentially the burst ratio of the compressive nature of the tubular structure, coupled with the accelerated rate of decay of the half-life of the carbon fiber bonding symmetry.

[@jonathanr2830]

Excellent presentation. Very informative. Thank you very much!

[@garethburns1282]

This piece is an excellent analytical assessment.

[@MasterMayhem78]

The best analysis I’ve seen yet. You’ve earned a new subscriber 👍🏻

[@doctorchadha]

Thank you!

[@dpasek1]

Yay! Thank you for the detailed strength of materials description at the beginning of your video. Most people do not realize that fiber composites are highly anisotropic, and that this has to be accounted for in component design. Another concept that you point out is that the stresses are from isostatic compression. This means that the Titan was a vacuum chamber, not a pressure vessel. It is obvious that James Cameron is not clear on that concept. Now considering that, please make another video discussing the phenomenon of water hammer and how this would result from brittle failure of the cylinder, and the effects that the massively powerful water hammer would have on the materials and components of the Titan at both microscopic and macroscopic scale. Please also discuss further the chemical and physical properties of carbon fiber. Please discuss the nature of bonding to and support of the fibers by the resin matrix. Also discuss the surface chemistry of carbon fibers. It would seem that the pyrolysis manufacturing process would produce fibers that are much like very long carbon nanotubes, which would have very slippery surfaces similar to graphite flakes. Bare carbon fiber is physically slippery, like it has little opportunity for hydrogen bonding between adjacent fibers, so that it is not readily crosslinked by a resin matrix. It is also as brittle as glass and cannot be bent smaller than a certain characteristic radius. Would it be possible to chemically attach -OH or -NH2 groups at intervals along the carbon fibers to enable the bisphenol-a diglycidyl ether epoxy resin component of an epoxy polymer matrix to chemically bond to and crosslink the fibers? This treatment would significantly increase the axial compressive strength and fatigue life of carbon fiber composite materials. Thanks in advance.

[@danh9002]

Great video. Thank you for sharing.

[@roystonboodoo7525]

Excellent stuff, bro. Thorough structural engineering presentation .

[@4000angels]

This was an excellent video. Thank you.

[@elizabethraitanen5057]

Thank you for making this video!

[@richardernsberger5692]

Very well presented---thank you!

[@elliesimpson1313]

Excellent video. Thank you!!!

[@TheVicOlive]

Hello Dr Chadha, thank you for your accurate synopsis of this tragic event. However, as a structural engineer I would have thought that you may have gone into more detail about the actual structure and build of the craft (although I know very little is known about this in reality). I have a suspicion that the main thing that causes this to fail may have been the way that the Carbon Fibre was wound onto the bobbin to produce the hull. From the videos I have seen it would appear that the fibres were wound only in a straight axial direction with no weave or fibres in the longitudinal direction, whether this is true or not I am unsure, but if this is true, there would be almost no tensional strength in the walls of the hull. So of course when the pressures deflected the walls at the centre of the cylinder, the inner part of the wall would have been subject to immense tensional stress as it was stretched by the effect of the wall being pushed in,. If the Carbon Fibre strands were not woven or if there were no fibres in the longitudinal direction the only thing resisting this tension would have been the strength of the resin bonded to the fibres. This would have caused the inner call to axially crack then crack would have propagated from the inside to the outside. The water would then have entered the inside and then would have blown out the window and both end caps off the hull.

[@stargazer5784]

A video I saw on another channel showed that the fibers alternated direction by 90 degrees in each of the approximately 480 layers in the hull. That being said, the most likely cause of failure was the cylindrical shape in conjunction with the vessels' size. Very small cylindrical structures (too small for an occupant) can withstand huge amounts of pressure, as is evidenced by the recovery of a small cylindrical perfume bottle from the wreck site with it's contents still intact, glass stopper still in place. Larger, deep diving, man rated vessels require a spherical shape. Truthfully, they were lucky it didn't pop on the first deep dive. Composite fiber and glue just isn't safe for this kind of vessel. Imho. I'm not an engineer, but physics was one of my majors in college, and this whole thing kind of seems like a no brainer. There's a huge difference between being an aeronautical engineer and being a naval architect and engineer. Two different pursuits entirely. Both require a high degree of skill, yet they are as different as night and day.

[@everTriumph]

The external pressure would cause compressive stresses along the length of the hull as well as radially. The blending of end caps and body is always problematic (ask Boeing). The hoop stresses will be compressive. That is not a good way to load unidirectional CF wound circumferentially.

[@TheVicOlive]

@@stargazer5784 Hi, in the video I saw the winder was merely going from end to end with straight fibres. I saw another video of a pressure vessel being wound with a cross weave of fibres but this was of a small vessel. When you wind a cylinder made from a cross weave of fibre the resulting cylinder has visible cross weave patterns on the outer surface, however when you look at videos of the Titan vessel end caps going on the outside of the CF vessel is absolutely smooth which leads me to surmise that the fibres in fact had no cross weave. It would be good for the company that wound the fibres onto this bobbin to comment on the way it was constructed wouldn't it?

[@nathangainer6828]

Thank you most informative video so far. Subscribed.

[@wolfhalupka8992]

from one engineer to another- thanks very much for a very clear, precise explanation.

[@doctorchadha]

Glad it was helpful!

[@clivewismayer2404]

Thank you Doc. Good luck with the channel.

[@christophercripps7639]

I am not sure aviation experience with carbon fiber-resin composites (CFRC) provides more than a basic starting point for manufacturing, certifying & operational inspection in a submersible. For starters, I can't think of an aviation application with 5" thick CFRC members of the size of Titan's pressure hull. Second in aircraft/spacecraft the pressurized fluid is inside and the delta P is far smaller (at most 1 atmosphere in crew compartments). For pressure vessels of this sort the exterior should be in tension with the maximum stress on the exterior surface where fatigue cracks are more easily spotted. TBH I have no idea where the max stresses will be in a thick walled cylinder under compression. I've only been exposed to items like water tube boilers, hot water heaters, driveshafts in torsion, fuselages and the like where fatigue cracks are almost always found on exterior surfaces.

[@stephenhicks826]

A respectful and clear explanation of what we know so far about this engineering failure. Thank you.

[@doctorchadha]

Thanks for watching!

[@burtbackattack]

Excellent and insightful video.

[@micaelauriarte3233]

so clear explanation, thank you!

[@jenna2431]

As a more artsy person, I'm really glad there are minds who thrive on this stuff.

[@starboy1100]

A very good analysis of the situation leading to the outcome.

[@doctorchadha]

Thank you!

[@emitindustries8304]

The first bathysphere was a perfect ball, to withstand the pressure.

[@doctorchadha]

You bring a great point. A “Sphere” with appropriate thickness is the best geometry to resist radially compressive loads.

[@chemech]

@@doctorchadha A cylinder however, can be an acceptable design, provided the proper design, selection of materials, and fabrication are followed.

[@michaeltb1358]

Best explanation of the problems I have seen.

[@AmanChowdhury888]

Great presentation. Someone in another video pointe out the various screws being bolted nto the hull to support the display monitors and lights fixtures, also factored in to further reduce the structural integrity of the already sketchy hull made of a carbon. The little screws bolted into the 5 inch hull directly, causes stress and reduces integrity a materIAL that's susceptible to brittle break offs

[@gellis7975]

Thank you for your objective and rational analysis of the factors involved in this tragedy. I am now well-informed regarding the possible points of failure that bedeviled the ill-fated submersible, and I will be able to understand the results reported by official investigators appointed to examine the likely causes of this avoidable human disaster.

[@doctorchadha]

I am glad it was useful!

[@MrFlareone]

I'm not a carbon fiber xpert but have assisted in making a hood for a racecar and I was taught by a vfn fiberglass tech the important details.we first layer in a controlled environment kinda like a paint booth.second it's very important that the resin to bond the layers of carbon sheets is mixed 100% properly and at the correct temperature. 3rd we did a counter weave do add rigidity. If we layer the fiber directly onto each other it wouldn't be as strong as changing direction 45-90 and so on.then you have the whole process of removing the air from the resin.was this vessel vacuum sealed or how was this process done as well as what bonding agent Was used not for the titanium to carbon but to bond the carbon hull itself?Was the hull then sealed and gel coated to prevent the salt water eating the resin away thus weakening the fiber structure?even down to a basic surfboard that lives its life in the saltwater there is a very specific process to follow..The videos I have seen of them making the hull and fitting the titanium caps they follow no clean ,control ssop's at all when working with the carbon fiber or when they mounted(glued/jb welded)the end caps on...

[@snowmiaow]

I was hoping for more of an analysis. Thanks for the diagram on carbon fiber fatigue.

[@sushimamba4281]

Imagine trusting your life to an acrylic view port that was only rated to 1300m! Mind boggling.

[@robertlevine2152]

I appreciate your insight into the engineering aspects of the Titan. One thing I have noticed in OceanGate's video of the construction of the carbon fiber hull is that there seems to be only a radial wrapping of the carbon fiber mat When you look at say the construction of the carbon fiber air tanks used for fireman's self-contained breathing apparatus (SCBA) the tanks are wrapped in a diagonal weave so there is a crossing pattern to the weave. The radial layered method is simpler to fabricate in comparison to a crossing weave. I wonder about the ability to distribute the load and prevent delamination, and fatigue strength. Another area I have to question is the design of the "hatch". According to reports the end bell, which included the viewport, was held in place with 17 bolts. In comparison 48" dia. 300 psi flange has 44 bolts. I realize that there is a difference between having the pressure outside vs. Inside. But 17 bolts results in an odd loading distribution around the flange.

[@johncummins3860]

Apparently there should have been 18 bolts but the top one wasn't used as it was difficult to reach !!

[@7thsealord888]

A clear and very thorough analysis. Thank you.

[@ruperterskin2117]

Right on. Thanks for sharing.

[@joes7968]

Thank you for your comprehensive overview and engineering analysis. Very informative for those of us without an engineering degree.

[@doctorchadha]

Thank you!

[@Jet-stream898]

Brilliant analysis

[@jtveg]

Thanks for sharing. 😉👌🏻