Material Interactions, Application and Catastrophic Results

[Former Member]

When I heard about the sub going missing and heard about the construction material I thought neat and my hinter voice started nagging, it took me a while to figure out why.

Carbon Fibre, Salt and Metal have bad interactions and result in corrosion of either the carbon fibre or the metal if not properly isolated.

A few exotic car owners found that out in salt winter conditions (which is why I remember it).

In a sub that goes to those depths I'm sure minor stress cracks occur in the isolating coating which if missed in maintenance leads to the exact conditions you don't want. Is this what caused the failure, don't know but I suspect it is going to come into play and review.

So let this be a lesson to all of us, to consider what, where and how we use materials which could cause failure.

 

[Rauce]

I think I read that the metal used in the sub in addition to carbon fibre was titanium?

That's the best structural metal for combining with carbon fibre with regards to corrosion, they're both on the cathodic end of the galvanic series so there's little interaction.

Steel and aluminum don't play well with carbon fibre in the presence of an electrolyte unless they're isolated from each other. In carbon fibre bicycles frames aluminum components that are bonded to carbon fibre (like threaded inserts or bearing seats) are usually anodized and have a layer of glass fibre or glass microspheres and epoxy in order to prevent corrosion.

 

[Arbutus]

Yeah, I read about that. You know I work with carbon fibre a lot and its wonderful stuff. Except when it fails. And the problem there, is that the failure is usually invisible, until the next stress cycle when normal elastic material movement focusses the stress at the edge of previous micro-fractures then - pop!
There's some other things about the description of the sub shell structure raise my hackles as an engineer (Naval Architect actually). We are discussing what is basically a laminated pressure shell designed to resist intense compressive forces. That's perfect if everything is moving and squeezing at the same rate. In any pressure hull there are openings for hatches and ports. Each of these structures causes a 'hard point' in an otherwise flexible hull. Now if the hull is TOO rigid, then excessive compressive stress builds up at the corners of these hardpoints, and in the case of a laminated structure, could easily introduce inter-laminar failures due to shear or peeling.
So in the worst case there's a titanium shell, supported by a carbon fibre shell. If either fails or delaminates at a point of extreme stress then catastrophic failure could occur without warning. I have not seen the construction plans at this point. They should behave as one piece, with the loads properly distributed. The extreme stiffness of the shell is probably not an advantage here. In the case of a classically built submarine, there is an outer and an inner hull, the inner hull provides the structural support against water pressure. As the boat dives, the elasticity of the steel allows the structure to adapt to the changing loads. With a relatively stiff and brittle structure where there is reliance on a perfect glue lamination between titanium and carbon fibre, well - I am very sceptical about the fundamental structural design of the Titan.

Thats my $0.02. until we know more.

 

[Former Member]

One of the articles I read indicated a lot of "cost effective light weight" methods where used (or as stated by some....short cuts). I guessing that meant not all parts where titanium which gets back to the original comment of interaction.

Again the point is, use this as a lesson not to make a mistake.

 

[Arbutus]

a lot of "cost effective light weight" methods where used ! Light weight is not part of the design goals for a submarine!!

 

[whydontu]

a lot of "cost effective light weight" methods where used ! Light weight is not part of the design goals for a submarine!!

Apparently some of the design criteria for Oceangate were aimed at non-engineering goals.

In 2018, a former employee of OceanGate Expeditions, submersible pilot David Lochridge, voiced concerns about the safety of the Titanic tour sub and filed a lawsuit against the company.

Lochridge, who was fired by OceanGate and sued by the company for allegedly disclosing confidential information in a whistleblower complaint to the Occupational Safety and Health Administration, said in a court filing that the Titan would carry passengers as deep as 4,000 meters even though that depth had never been reached in a sub with its type of carbon fiber hull. According to his claim, he learned the vessel was built to withstand a certified pressure of 1,300 meters, although OceanGate planned to take passengers to 4,000 meters.

Lochridge was not the only skeptic. The same year his complaint was filed, other industry leaders approached OceanGate with questions about the safety of its submersible. William Kohnen, president and CEO of Hydrospace Group, outlined his concerns in a 2018 letter to OceanGate, originally published by The New York Times, that warned of potentially "catastrophic" issues with the "experimental" sub, which was not certified. Kohnen told CBS News on Wednesday that although he did not send it, the letter was leaked to OceanGate and prompted the company to "amend a number of details that made sure the public knew" the submersible had not received its certification.

"The letter to Oceangate was meant as a professional courtesy to the CEO expressing industry concerns that the company was not following a traditional classification route for the certification of the submersible," Kohnen said. "The industry operates along an established and dynamic set of safety regulations and protocols that have served the submersible industry worldwide."

 

[Tom Kitta]

Here is James Cameron take on it (he went to challenger deep and 33 times to Titanic & designed his own subs):

Essentially:
1. This is mature science - diving has been done for half a century+
2. Certification is mandatory - there has not been any major accidents in certified subs
3. Material choice was questioned by everyone
4. There was no room for "experimental" stuff in commercial sub operations
5. A lot of people wrote letters to the company about issues above
6. He is truck to similarity of the disaster of Titanic and Titan - both commanders ignored warnings and went ahead
7. There is indication that the sensors on the hull (body was carbon fiber - end caps are titanium) did indicate delamination - it was just too fast to do much.
8. A lot of other safety stuff was simply ... ignored.

 

[Tom O]

The one I watched was saying that there was no backup systems like there is on planes.
I would rather it had a more radius on the sides right now it looks like he dreamed up the design having a beer at the cabin.

The viral video that reveals what happened to the Titan submarine

This video has millions of views and shows how the implosion would have occurred to OceanGate’s Titan submersible.

en.as.com

 

[Tecnico]

I've seen a reported reference to a statement by the company (link on their site is down) saying it was designed to comply with DNV (Det Norske Veritas) classification rules but not certified by DNV. I'll leave it to the experts & investigators and ultimately lawyers to decide whether the claim is valid.

The justification was said to be that certifying, essentially demonstrating to a DNV witness that by analysis and experimentally that the classification rules have been followed, would delay the development process. Having designed to DNV/Lloyds/ABS etc., there is some overhead involved. For normal industry practice, see @Tom Kitta bullet 2 above.

Another tidbit; it has been reported that when the US Navy heard that communication with the sub was lost they immediately started listening with (classified) underwater acoustic sensor systems (like SOSUS) and shortly thereafter heard a sound consistent with an implosion event in the area but not confirmed. I would have thought that they would have been continuously been recording data anyway for other military reasons so maybe they went back to their recordings for the event.

The on-scene management was advised but since it was not verified they naturally continued as though there was a chance of rescue.

James Cameron has said that he thought that a catastrophic event occurred when he heard that both communication and position data signals were lost simultaneously. His reasoning was that those systems were independent and the position data equipment was in a separate pressure vessel.

D

 

[Former Member]

a lot of "cost effective light weight" methods where used ! Light weight is not part of the design goals for a submarine!!

Oh I whole heartly agree on that statement!

This sounds similar to bean counting for the HMS Sheffield sunk in the Falklands conflict by make the hull from Aluminium on a Missile Destroyer Class Ship.

Again, I'm going to leave the final review to the experts on both the design and materials used for the sub as there are questionable items.

The point of the thread is to remind ourselves not to make misguided mistakes.

 

[Former Member]

The more I hear and read from third parties about the Sub, even if they are 25% truths it is being to show like a this is not how to do things plan.

God bless those that lost their lives because of such faulty thinking.

 

[Tom O]

Apparently while when early testing it by himself he noted the cracking sounds of the carbon fiber! Why he continued with that design I have no idea the only constellation is he went with it.

 

[slow-poke]

From what I have read there were numerous red flags raised and ignored. I'm somewhat of a risk taker, but considering the shortcuts, warnings, failed dives, law suites etc. I would not have gone down in that thing even if they paid me. One of the controllers was an OTS unit from "camping world". What could possibly go wrong?

Lance, the Duke University professor, echoed some of these concerns. She said the unconventional combinations of materials used in the Titan posed safety risks because “over the course of repeated pressurizations, they tend to weaken."

"This is not exactly what, in my opinion, would be innovation because this is already a thing that has been tried and it simply didn’t work,” she said.

Sounds like this is another one of those situations were the "expert" calling the shots either lacked the required expertise or simply ignored the warnings because it was incongruent with his vision.

 

[Susquatch]

I must be a cold hearted monster.

You wouldn't catch me in a submarine of any design going a mile down to look at a sunken ship even if the cost was $20Cdn instead of $250,000 US. I don't like ferris wheels let alone ultra deep subs. I'm just not a thrill seeker.

In a very strange way, many people pay to put their lives at risk all the time! Am I supposed to be surprised when a bungie jumper's cord breaks? Or a parachute doesn't open? Would I do a detailed material analysis on the quality of the bungie cord or the proper folding of the chute? Isn't the odd death almost a requirement to establish the death risk factor?

Is there such a thing as a risk free submarine trip to the Titanic? Is there such a thing as reasonable risk in such an adventure?

We are not talking about a flight to Toronto here.

The only lesson I take from this simply reaffirms my own belief in living my life using plain old common sense. Taking chances like that is just not for me.

The only people I feel sorry for is the billionaires son who may not have wanted to go and the friends and families of those who died.

I think trying to figure out what happened is a waste of tax payer dollars. If a bunch of "adventurous risk takers" want to go out in the middle of the Atlantic beyond our borders and take chances, they are welcome to do so, but don't ask me to finance it or to get upset.

Others are free to agree to disagree.

 

[Former Member]

I must admit I'm a risk taker, to the point of being the "crazy" one in the family.

I live by a simple rule of "crazy", I fully know what the risks are, and have the skills and equipment to stack the deck in my favour allowing me to push that limit just that little further. Stupid on the other hand is not accepting, knowing, ignoring or taking the precautions required for the risk you take.

This falls under if the "crazy" one thinks its "stupid" its likely a really bad idea. This goes back to my initial post, hinter voice is going oh oh.

 

[StevSmar]

Not an implosion, but a catastrophic pressure explosion story.

In my late teens, early 20’s I was shown how you could make a rocket out of a pressurized 1.25(?) litre pop bottle partially filled with water. Unbelievable how high this would go.

A few years later, I was sitting at a friends house and heard a muffled “whomp“ sound. And then later the sound of ambulances. A fellow across the road was flying his rocket and it exploded putting a piece of plastic through his hand, I believe his was off work for several months. He’d apparently ignored the white lines that appeared in the plastic from when the rocket hit the ground.

In hindsight I should have had proper PPE on durning my own successful adventures… some are lucky, other not.

 

[StevSmar]

I fully know what the risks are

I think I largely lack common sense.

I think I know what the risks are, but it seems all my good experience is largely based on bad experience. And the more I learn the more unique and unanticipated the scenarios seem to be.

Perhaps too much “ready, fire, aim”…

 

[whydontu]

I’m with @Susquatch on this, with one caveat: if I’m taking a risk, it has to be that I’m the one in control. Ferris wheel? Nope. Skydive? Nope. Drive a 1961 Chev pickup at 160 kph around a blind corner, or knee dragging a sports bike on the track? No problem, because I trust my own skills. As long as I make the decision and have confidence in the machinery then I will do it. But I wouldn’t do any of these with passengers.

 

[Tom O]

At least it was quick

 

[Tom Kitta]

I must be a cold hearted monster.

You wouldn't catch me in a submarine of any design going a mile down to look at a sunken ship even if the cost was $20Cdn instead of $250,000 US. I don't like ferris wheels let alone ultra deep subs. I'm just not a thrill seeker.

In a very strange way, many people pay to put their lives at risk all the time! Am I supposed to be surprised when a bungie jumper's cord breaks? Or a parachute doesn't open? Would I do a detailed material analysis on the quality of the bungie cord or the proper folding of the chute? Isn't the odd death almost a requirement to establish the death risk factor?

Is there such a thing as a risk free submarine trip to the Titanic? Is there such a thing as reasonable risk in such an adventure?

We are not talking about a flight to Toronto here.

The only lesson I take from this simply reaffirms my own belief in living my life using plain old common sense. Taking chances like that is just not for me.

The only people I feel sorry for is the billionaires son who may not have wanted to go and the friends and families of those who died.

I think trying to figure out what happened is a waste of tax payer dollars. If a bunch of "adventurous risk takers" want to go out in the middle of the Atlantic beyond our borders and take chances, they are welcome to do so, but don't ask me to finance it or to get upset.

Others are free to agree to disagree.

I guess the fact that by the end of August I am going for a 6 week expedition to Nepal where I try to climb Manaslu solo without oxygen 8165m means I am a bit crazy

It is all about risk management. Any risk that can be managed away is managed away. I.e. I am not climbing say naked (was attempted). I will also not climb when avalanche conditions are "certain avalanche" - also was done. I will not climb when winds are over 100 km/h etc.

I may not have the best gear in the world - and I do cut some corners - but I know the system I have worked in the past and I do have backups.

In case of this sub, they cut corners at every possible area. They were purely negligent. In canyoneering and other sports I led in US we had "death" wavers. It was necessary. But we knew that these will not protect if we do something plain stupid.

For example, if we check the weather and weather services says perfect weather, no chance of any rain or even touch of a storm we did our due diligence. If there is totally unexpected storm, a bit far away, that still in canyon catchment and someone dies - we can point to a waver - no one knew super freak event will happen. We did standard checks. Same with an event where there is a dam and you call them and ask, will there be any release of water. If they have release due to an accident and someone dies - waver can be used. What happened on that sub was similar to simply never checking the weather. Totally suicidal. It was only a matter of time. Eventually your luck runs out - there is a strong thunderstorm and most people or all in your team end up dead.

The company is done for. And I would not be shocked if they sued the owner personally and priced through corporate veil.

Incidentally deep see diving is quite safe. The actual *certified* old submersible this company purchased second hand has like 1300 dives on the clock - no accidents. Key words here - certified and not build by them There are many other submersibles out there - all safe, certified etc. The capsule made out of carbon fiber that was to go to challenger deep was designed for a SINGLE dive. Yep, go once, recycle.

DSV Alvin - Wikipedia

en.wikipedia.org

This is from bloody 1964. In service since 1964. Test depth of 6500m.

Yeah, that is almost 60 years of service. Every few years total overhaul & inspection. They did not make junk in the 60s, like my lathe - good stuff.