[cloudbonsai]

Among the interviews, one with the former engineering director was the most eye-opening for me.

https://data.ntsb.gov/Docket/Document/docBLOB?ID=17236880&Fi...

It appears that all the engineers -- system designer, material engineer and structural analyst -- thought that OceanGate CEO was going to kill himself:

    If you ever find <name-of-the-engineer>, he’s not going
    to have a whole lot of nice to say. He was very frustrated
    with the company. (...) And I understand why. He thought
    Stockton was going to kill himself.

And the director himself declined to dive on Titan when asked:

    Now, the question is, why wouldn’t the engineer get inside
    his own vehicle? It was because of what I felt -- and I have a
    background in Navy diving in EOD operations. I knew firsthand
    that the operations group was not the right group for that role,
    and I told him as much, that I don’t trust operations and who he
    has there.

[bambax]

The number of stupid decisions that went in the design and construction of the Titan is astonishing. One of my favorites was that, after putting on the carbon fiber around the tube, they would sand imperfections to make the surface perfectly smooth, severing layers in the process! It shouldn't require an engineering degree from MIT to recognize this as ill-advised.

[lazide]

Even without that, the material is just wrong. It’s strong in tension, not so much compression. Tends towards sudden brittle fractures. Doesn’t like impacts, as it tends to have issues with delaminating.

It’s just not what you ever want as a sub hull. It’s dumb.

And weight is not even a huge issue for a sub!

[bambax]

Yes, using carbon fiber was also a very bad decision; it was known for a very long time that it was only good for single-use sub, because after the first dive it was too damaged to continue. In 2014, Virgin Oceanic, which had similar plans with similar technology, closed shop because it didn't make economic sense to build a new sub for each dive.

But weight is absolutely an issue; the basic and tried-and-true metal sphere design allows for only three people. Since size and thickness grow exponentially, making a sphere for more than three people becomes more and more difficult. And it should also be possible to lift the vehicle with a crane.

But if you want to carry paying passengers (like Oceangate did), having only two per dive is very limiting. That's why they went with a tube design, and carbon fiber to limit weight. But it couldn't work, and it didn't.

[schiffern]

  >size and thickness grow exponentially

It's a [reverse] pressure vessel, so it follows pressure vessel scaling. Mass scaling is linear with internal volume.

[FabHK]

It’s funny how “literally” often means “figuratively” now, and “exponentially” means “polynomially”.

[bambax]

Yep.

https://books.google.com/ngrams/graph?content=exponentially%...

[bambax]

Ok yes "exponentially" was hyperbolic. Mass scales linearly with volume, but volume is proportional to the cube of the radius (not linear).

Also, in practice, small imperfections can have a disproportionate impact on the resistance of the sphere so design codes typically apply conservative reductions that can have a big impact on actual thickness requirements.

[wkat4242]

Did this thing meet any design codes though? I doubt it.

[owenversteeg]

“Strong in tension, not compression” is a meme, and obviously wrong. It is certainly stronger in tension, but it is also remarkably strong in compression. That’s why it’s used - yes, in compression - in modern passenger aircraft. You don’t even need to know that, though; the simple fact is that the Titan had a double-digit number of deep dives. If it was weak in compression it would not have survived diving to 3.7 kilometers deep or even a fraction of that depth _once_.

That said, yes, it’s a difficult material to use properly, and they were a bunch of cowboys slapping things together. It’s no surprise that they missed several critical steps and created a sub doomed to fail.

N.b. all of this was kickstarted by James Cameron saying that carbon fiber has “no strength in compression” in a New York Times “science” article, which the Times printed directly.

[lazide]

Aircraft fuselages are typically loaded in tension. It’s a key part of the design.

Carbon fiber compressive strength is only ~ 30-50% of it’s tensile strength because of the way the fibers and the epoxy interact. When compressed, the carbon fibers don’t do as much. [https://www.sciencedirect.com/science/article/abs/pii/S02638...]

But don’t believe me, actually read a useful paper on the subject.

In fact, it’s a major factor limiting it’s wider use. As is it’s fatigue behavior, which would probably also explain why it eventually imploded!

I never followed James Cameron’s interview, but it sounds like he knows what he is talking about!

[owenversteeg]

James Cameron certainly knows a lot about submarines, but if he says something factually incorrect then it’s factually incorrect, period. Carbon fiber does not have “no strength in compression” and it is used in compression in countless applications, for example airplane wings. Again, the fact that the sub - built at absurdly low cost for its size, built by a bunch of cowboys that didn’t know what they were doing - DID survive to 3.7 km deep on several occasions is proof sufficient. If CF had no compressive strength than the whole thing would have failed at a tiny fraction of that depth. If CF had no compressive strength then what kept the sub together during the successful dives? Hopes and dreams?

I’m not here to defend the decision to use carbon fiber, and as I’ve said I completely agree that there are many issues with using it in this application. Delamination, water ingress, bonding the titanium to the carbon fiber, difficulty of manufacture including varying layer thickness and voids, sensitivity to impact, the list goes on. But _those_ are the issues, not the compressive strength.

[lazide]

Moved the goalposts again eh? While completely ignoring the cites and discussion? What, were you a major shareholder? Family member?

[buildbot]

Speaking of which I heavily recommend reading interview the prime ancestor comment to this chain linked. It’s really clear he knows what he is talking about.

[franktankbank]

I don't like this interpretation of things. Its worthwhile to experiment and try things. They were basically mentally ill as a group and rejected genuine concern. Everyone wants to shit on the build but it was the human relations that killed it.

[nativeit]

Also, honestly, the build. That “genuine concern” they ignored was that the build was critically flawed. I don’t think anyone here would have these takes if a small group of curious engineers tried their hand at a composite submersible, it was when they kept doing it after all the qualified engineers had said, “This is crazy, I’m out.”

The build was kind of dumb, and I’m hardly an engineer. It’s common sense. Carbon fiber composites are interesting because they’re strong relative to their weight. Remove either of those features and they become pointless.

Who cares if a submarine is heavy?

[potato3732842]

A submarine needs to be light to be neutrally buoyant in order to fly though the water properly. Otherwise you have a bathyscaphe, which has some other not nice failure modes (in addition to the "implodes if you f it up" one) and are much less maneuverable and arguably the whole system is less durable more costly for high tempo operations. "Just build a tube strong enough and big enough to not need all that" is a better answer, if you can pull it off.

[bokohut]

'And the director himself declined'

An anecdotal personal story as it aligns with this exact statement although no one got killed but data breaches certainly occurred.

Many years ago now I was propositioned to be on the board of a financial technology company and they spared no expense in literally rolling out the red carpet for my arrival. I found it all very laughable being solely focused on business and the technical details as I was not being fooled by all the schmoozing. After hearing all the unrealistic business objectives and the promise of having the Philadelphia Flyers involved I then asked to meet the technology team that built the product to see a demo. They bring in one young guy who built it all, the executives are still present mind you, and they allow me to ask any and all questions about the platform that nearly no one in management comprehended. After seeing the demo which involved several blatant security issues I asked only one more question of the sole developer: "Would you put your financial information into this system?"

He provided his answer in front of the companies executive board and I can still see their reactions to this very day. I then stood up and thanked everyone for opportunity and left.

[robot-wrangler]

Wow! Man, an insider with these kinds of concerns isn't exactly exonerating or excusing themselves with such a testimony. Whistle-blowing to any relevant authority as hard as possible seems like the bare minimum? And if there's no governing agency to pass the responsibility over to, I think you gotta quietly approach the first customer (or victim) with these concerns if not a newspaper

[idontwantthis]

I read that the pilot was also basically suicidal. His wife had died, and he was completely fine with the danger because he would die doing what he loved, and he didn't really want to live anymore.

[djmips]

Wasn't the pilot Stockton Rush? His wife was alive. Who are you referring to? I tried to check your claim but I couldn't verify it.

[nagaiaida]

they're talking about nargeolet

> Wreck expert Paul-Henri "P.H." Nargeolet, who was also onboard, told me he wasn't worried about what would happen if the structure of the Titan itself were damaged when at the bottom of the ocean. "Under that pressure, you'd be dead before you knew there was a problem." He said it with a smile.

(as recounted by Arnie Weissmann, in Travel Weekly article published June 22, 2023)

[idontwantthis]

Yeah I got the roles of pilot and guide mixed

https://www.newyorker.com/news/a-reporter-at-large/the-titan...

[netsharc]

There was only one other crew member in that vessel (well, actual crew and not paper "mission specialist"). He was an older gentleman, and it's quite common for older people to have lost their spouse. Was that so hard to figure out?

[djmips]

yeah but he remarried