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Engineering assessment of the OceanGate Titan failure

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Re: Engineering assessment of the OceanGate Titan failure

#61

Post by rich_sasha »

ceejayoz wrote: post #4
rich_sasha wrote: post #2

I know nothing, literally nothing, about material engineering, past what I can skim off wikipedia and ingest on cycling websites. But I always thought composite nonmetal materials are hard to test nondestructively, which is the main limiting factor for their use in aerospace. Metals can be X-rayed to assess their condition, carbon not. Is that wrong? What am I missing? Just curious.

I don't think you're missing anything. Others, including those in-the-know, were left scratching their heads too. https://www.nytimes.com/2023/06/20/us/oceangate-titanic-miss... > Years before OceanGate’s submersible craft went missing in the Atlantic Ocean with five people onboard, the company faced several warnings as it prepared for its hallmark mission of taking wealthy passengers to tour the Titanic’s wreckage.…

I was more referring to TFA which seemed to assert that you can test carbon fibre, with some kind of EM radiation.

That it was all a mess at OceanGate, that bit I got :)

Re: Engineering assessment of the OceanGate Titan failure

#62

Post by engineer_22 »

hef19898 wrote: post #54
engineer_22 wrote: post #49

This isn't an engineering assessment, at best it's speculation about what caused the loss of the Titan.

Whatever the exact failure mode, it was the most dangerous thing that let to Titan's destruction and the death of five people: the combination of stupidity and hubris.

Speculation

Re: Engineering assessment of the OceanGate Titan failure

#63

Post by tylergetsay »

ghostpepper wrote: post #44

> Consider the fact that most engineers can explain the cause of the Hyatt Regency walkway collapse (if you can’t, you shouldn’t be an engineer), the Tacoma Narrows bridge failure, the Union Carbide Bhopal disaster, and the space shuttle Challenger disaster Does anyone know of a good documentary about famous engineering failures? Bonus points if they actually go into detail about the scientific explanation, as oppose…

There's a podcast called "well there's your problem" that covers them. their style isn't for everyone but I find it very entertaining

Re: Engineering assessment of the OceanGate Titan failure

#64

Post by toss1 »

I own a carbon fiber design & manufacturing shop that does aerospace and undersea work. Watched the video by "Just Alex" and the section the bonding of the titanium end-caps and the cylinder absolutely gave me the creeps.

The video was absolutely right to mention lack of dust-free environment (vs open warehouse), lack of temperature control, and lack of degassing equipment. We also have no idea about the properties of the epoxy used to bond it, whether it has the suitable amount of compliance, properties under temperature change, etc.

Worse yet, I saw no precautions being taken to avoid entrapped air in the bond, in fact, it seemed quite likely, and the sections with entrapped bubbles would be NOT bonded. Same for any sections with entrapped dust, debris, or whatever else was floating around that warehouse. I would want to see, along with the all of the above steps, either or both applying very substantial pressure to the Ti/Carbon parts while curing to force out any air, and/or doing the whole process in a vaccum environment.

The out-of-date carbon fiber? Sure, it is fine, for some months, for noncritical applications. For critical applications? NO WAY. And the CEO's claim that aerospace needs to be more stringent than undersea 5000psi is just beyond stupid. You need absolutely the best bond between layers that you can get.

Also, the 480-odd layer layup and cure is hugely experimental by itself, and I've read elsewhere that the shop was given six weeks to design and fabricate the hull. Insane. I'd feel like six weeks to design and run a few initial proof-of-concept tests of a 5-inch thick layup would be too quick.

I could keep going for pages just on the carbon-fiber crimes I've read about.

My absolute disgust for the CEO grows every time I read more. He got what he deserved, but the passengers he suckered into taking the trip did not.

Re: Engineering assessment of the OceanGate Titan failure

#65

Post by onlyrealcuzzo »

philjohn wrote: post #53
onlyrealcuzzo wrote: post #41

Earlier quoted context omitted.

> Nothing they did showed that they ever chose the more expensive option. It's so absurd. Deep sea tourism is going to be something only for the .1% for a while. They can afford a vessel that's 1000x more expensive. Your market is about 50 people. They've got unlimited money, basically. Why cheap out and die? I just don't get it.

I suspect their end goal was to sell deep sea subs to the oil and gas industry, and this was a testbed.

Why would you do that manned instead of using remote control?

I'm assuming your engineering requirements for an unmanned sub would be substantially easier for a number of reasons (not needing to worry about killing someone, mainly).

Re: Engineering assessment of the OceanGate Titan failure

#66

Post by gnfargbl »

MobileVet wrote: post #3

> From all available sources, it is apparent that the viewport was designed and certified down to a depth of 1300 meters, not 4000 meters. Wow. What kind of hubris could look past that huge red flag? Apparently the kind that thinks it is interesting that it deforms by several inches and not scary

> What kind of hubris could look past that huge red flag?

I don't think it was outright hubris. I think it was commercial necessity, driven by the business model that OceanGate used: Rush needed rich tourists to fund the business, and he got rich tourists by offering them a close-up view of a famous shipwreck. To give his passengers a view that they were willing to pay for, he needed an oversized viewport.

He had already proven this business model with his earlier submarines, so it is understandable that he wanted to carry it on as he built vehicles intended to go deeper. Less understandable is that he set aside the reality that a large-enough viewport could not actually be safely procured. That's not really hubris though, just plain old profit-driven idiocy. The whole thing feels like it has less in common with the Titanic and more in common with the Ford Pinto.

Re: Engineering assessment of the OceanGate Titan failure

#67

Post by plegresl »

SV_BubbleTime wrote: post #19
jamincan wrote: post #6

Earlier quoted context omitted.

It's pretty much 1/3 the depth which is suspiciously close to a 3x safety factor which is what I've always heard engineers use. They certainly seemed cavalier with safety, so it wouldn't surprise me if they reasoned about it in that way.

A rocket might have a factor of safety of around 1.1. This is because at 1.3, they’ll never leave the ground. This is why they are so carefully monitored and tested, and still fail. It’s all relative. Good engineering doesn’t mean higher number. No one knows what the FOS for this sub was. Given the information from the CEO, things like that were just slowing down innovation! EDIT: Not all rockets, just using an examp…

Falcon 9 uses a factory of safety of 1.4: https://www.nasa.gov/pdf/164283main_2nd_exp_conf_24_Commerci...

Re: Engineering assessment of the OceanGate Titan failure

#68

Post by hef19898 »

engineer_22 wrote: post #62
hef19898 wrote: post #54

Earlier quoted context omitted.

Whatever the exact failure mode, it was the most dangerous thing that let to Titan's destruction and the death of five people: the combination of stupidity and hubris.

Speculation

Of course, we have to wait for the various investiagtions before we know for sure.

Re: Engineering assessment of the OceanGate Titan failure

#69

Post by kodah »

anon_cow1111 wrote: post #58
kodah wrote: post #22

> It was previously stated by the CEO that each time he descended to that depth, the viewport deformed several inches inward. It takes an incredible level of density to ignore this once, but multiple times? Can someone tell me what happens to a human body when suddenly exposed to ~5000 psi? Edit: I looked it up. The human body almost instantly incinerates. It takes a matter of milliseconds.

>Edit: I looked it up. The human body almost instantly incinerates. It takes a matter of milliseconds. This is most likely BS- consider that a shotgun shell is made from a low melting-temp plastic and handles higher pressures and temperatures without issue (and repeatedly if you're reloading them). Probably your hair and light clothing would burn somewhat during an implosion, but would be extinguished as soon as the…

Feel free to give this a read, it has an answer for your assertion about waters role: https://mindofjp.medium.com/what-really-happens-to-a-human-b...

Re: Engineering assessment of the OceanGate Titan failure

#70

Post by mechanicalpulse »

SV_BubbleTime wrote: post #18
ramesh31 wrote: post #14

Earlier quoted context omitted.

My question is just... why? It's not like carbon fiber was any cheaper than just making the thing out of steel or titanium like literally every other submersible. It just doesn't make any sense. You have none of the weight penalties that exist in aviation, so the heavier and the thicker the better.

As I understood it, you do have a weight penalty for a sub. You need to get back up by powered movement, or down by it. You are limiting your dive time either way. They can’t use foam for flotation at that depth. There is a concrete like “synthetic foam” if you want unpowered rise to surface but it’s expensive. I read early on they wanted carbon to be light enough to get back up by releasing weights on powerloss. Fro…

> They can’t use foam for flotation at that depth. There is a concrete like “synthetic foam” if you want unpowered rise to surface but it’s expensive. I read early on they wanted carbon to be light enough to get back up by releasing weights on powerloss.

This would make sense. The first bathyscapes (FNRS-2, Trieste) used the same iron ballast method via electromagnets, but bouyancy was provided by an external tank filled with a liquid of lower density than water -- gasoline.

I hadn't heard of the foam before, but I looked to see how modern deep submersibles provided bouyancy. The first one I checked was the one I'm most familiar with from my childhood fascination with the Titanic -- DSV Alvin, commissioned in 1964 and taken by Robert Ballard on the very first expedition to the wreck -- and it uses such a foam developed around the same time. A minor correction, though: the foam is called "syntactic foam"; the term shares its etymology with "syntax": from Greek σύν (sún, “together”) and τάξις (táxis, “arrangement”). These foams are composite materials containing what they call "cenospheres" or "microballoons": tiny, rigid, hollow spheres. Why use a large steel ballast filled with flammable hydrocarbons when you can use thousands of much smaller ones made out of an assortment of materials from ceramic to titanium to polymers?

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