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"Not at all, because carbon fiber is better compression then tension. And that's what nobody understands. It's completely opposite of what everyone else says. Everyone's, oh, carbon fiber can't handle compression. They're full of shit, and I've proven they're full of shit."

- Man crushed by custom carbon fiber submersible

The funny thing is that it's trivially untrue of carbon fiber, which has a compressive strength ~40% of its tensile strength.

Being weaker in compression than in tension is not the same as being unable to handle compression. 40% of carbon fiber's tensile strength is still comparable to the compressive strength of high strength steel.

> Not at all, because carbon fiber is better compression then tension.

That's still false though.

So there's a NASA/Lockheed report on this.

> https://ntrs.nasa.gov/citations/19810045017

As 95% of the carbon fiber market is T300, and as T300 hasn't changed in the years since, I think it holds up.

Long story short, raw carbon fiber has a high compressive strength, but it's still just ~40% of its tensile strength. Carbon fiber composite single-plies or tapes have a reduced, but still reasonably high, compressive strength. When you get to multi-ply 0/90° or 0/45/90° composite laminates, "allowable" A-Basis (<1% likelihood of failure) compressive strength is very low -- around 400MPa -- well under the compressive strength of good steel.

And that's under ideal conditions. You've got to apply knock-downs for ply angle, moisture, through-thickness shear, impact damage, and manufacturing defects.

...Hence the Titan sub failed at a compressive load of something like 200MPa.

I'm not accusing you of this, but one of the issues with carbon fiber is that people see on a specsheet that it has, e.g., a "tensile strength = 4000MPa" and they assume that composite parts will exhibit a practical tensile strength of 4000MPa. The properties of CFRP -- CF composites with epoxy or PEEK or whatever -- are always way reduced, and sometimes quite difficult to pin down.

That said, the tensile strength of CF is always high, as a rule of thumb. Its compressive strength really isn't.

I would not call 400 MPa "very low" that's better than the best structural steel. Further, the important thing is the specific strength. CFRP has a density 5 times lower than steel, meaning you can use 5 times as much for the same weight, bearing 5 times the load. A good steel has a compressive strength around 1000 MPa, the best superalloys have compressive strength around 1500 MPa, the same weight of CFRP can withstand the equivalent of around 2000 MPa.

Sure this is idealized, but so is the strength of steel.

The concern with carbon fiber is its potential for delamination, not its compressive strength. Titan's failure was after delamination.

400 MPa is not better than the best structural steel. And 1000 MPa is way higher than the best structural steel (compressive strength and tensile strength are essentially equal for steel). Most structural steel has an ultimate tensile strength of around 500 MPa. Ultimate tensile strength is the comparable strength parameter when discussing rupture/fracture.

400 MPa is better than the best structural steel. 1000 MPa is not for structural steel, it is for high grade steel, the sort you make submarines out of. Why would I list 400 and 1000 for the same value?

Steel is weaker in compression than tension. It's more isotropic than say concrete, but the difference is meaningful in practice.

We're not discussing rupture here. That's for when the pressure is higher internally than externally. We are discussing a submarine, which is a pressure vessel under compression which must also remain buoyant. The specific yield compressive strength is the value which matters.

When someone says "structural steel" they are normally talking about something similar to A572. A572 comes in multiple grades, with grade 42 being the lowest. Grade 42 has a yield strength of 42 ksi (hence grade 42) and a rupture strength of 60 ksi by spec. 60 ksi is 414 MPa. Even A36 (which is basically the weakest structural steel commercially available nowadays) has a rupture strength of around 60 ksi and a yield strength of 36 ksi. Hence, even the weakest "structural steels" have a rupture strength of around 400 MPa.

When I use the word "rupture" I am talking about the material property, not the specific submarine loading condition at play. When comparing steel, which is a ductile material, to carbon fiber, which is a brittle material, you should use the steel's rupture strength instead of yield strength. Steel is for all intents and purposes an isotropic material, and the difference between tensile strength and compressive strength is not material in practice (because steel in compression is nearly always governed by macro-scale geometric issues leading to buckling rather than the material strength in compression being exceeded).

The '~' is important: composites are in general very difficult to predict, and under compression even more so.

(To build some intuition: carbon fibre, is just that, i.e. a fabric. No-one expects to be able to push on the edges of a sheet of fabric get any real resistance at all. If you then embed that it a plastic, i.e. make a composite, the plastic is mainly what makes it hold its shape. It's only really made stronger in tension by the fibers in it, why would you expect the compression to be better?)

"Now, if it fails, then you have to stop, and it's -- again, this is not something that just happens all of a sudden. It doesn't just implode. It screams like a mother before it implodes."

- Man crushed by an instantly imploding submersible

Management classes will write textbooks about Stockton Rush, but not in the way he would have hoped

Why? There’s already a plentiful list of disastrously wrong arrogant cocksure assholes. Still doesn’t stop people from thinking they’re the Steve Jobs flavor of arrogant cocksure asshole.

Steve Jobs, who very famously died of pancreatic cancer because he delayed surgical treatment in favor of fruit juice? That Steve Jobs?

the disastrously wrong arrogant cocksure assholes don't hear that part, they just hear "people told him he was wrong" and "millions of dollars"

Right next to the O-rings will survive in temperatures colder than they were designed. At least Rush's backside cashed the check his mouth wrote where as the NASA engineers were still around after their decision. Does that make one better/worse than the other? Rush took other people with him though when he cashed that check.

For the record, NASA engineers recommended against launching, but were overridden by, as usual, management.

And again when Boeing's management overridden engineers in decision that Max 8 was safe to fly and new flight stabulity electronics were good enough.

For the record, Rush was management as well

To be fair, it did scream before it imploded.

They just disregarded the screams because they couldn't afford to make sure it was still working.

“Now, you can Google this on Google”

"what are you gonna do, stab me"

- Man crushed by custom carbon fiber submersible

> But instead they left Titan winter on the parking lot in Saint Johns where it was not protected from any exposure because that was cheaper.

This came up in the hearings. It's standard practice to do this but it's probably different leaving say the metallic Antipodes [1] outside than carbon fiber.

[1]: https://en.wikipedia.org/wiki/Antipodes_(submersible)

The report here more or less outright says that leaving it outside was a major factor in the incident. The incident on dive 80 was adjudged to be partial delamination of the carbon fiber layers, and leaving it outside subjected it to freeze-thaw cycles that propagated the delamination into near-total delamination, which promptly failed the next time the hull was pressurized. Although there is also the aborted dive 87, which subjected to the submersible to a lot of percussive damage via wave action.

One wonders if any of these people have ever heard the term, "Don't poke the bear."

Reading this is like watching someone gamble their life savings away because they know the next round/hand is gonna be the one where they win it all back.

Some real gems here and learned some things I wasn't aware of.

> "Now, if it fails, then you have to stop, and it's -- again, this is not something that just happens all of a sudden. It doesn't just implode. It screams like a mother before it implodes."

> On dive 80 during surfacing people heard a "loud bang" from the submersible (according to a witness it sounded like a gunfire)

Well, there you go.

> But instead they left Titan <during the> winter on the parking lot in Saint Johns where it was not protected from any exposure because that was cheaper.

> During hauling it become loose and started knocking against the hauling platform (LARS) because of the waves. Day later they did a dive where it imploded.

Early on, it was made clear that carbon fiber hulls could not easily be inspected for integrity issues like metal hulls can be. I'm not an expert, but I'm guessing sensitive instruments have been around for a while for the purpose of inspection. Having a hull you cannot easily inspect would/should make most people/companies nervous.

This transcript is of CEO Stockton Rush interviewing redacted "Director of Marine Operations"? Do I have that right?

Why is there a transcript of the CEO interviewing one of his own employees, apparently in front of the NTSB, from 2018?

Edit: the transcript is between Stockton Rush and his former director of marine operations, David Lochridge, plus three other staff. [...] Lochridge: "That meeting turned out to be a two-hour, 10-minute discussion… on my termination and how my disagreements with the organisation, with regards to safety, didn't matter." [...] The 2018 meeting was recorded.

https://www.bbc.com/news/articles/c7819kx4498o

I believe it was a recorded phone call

Has anyone written up a narrative of this, presented that transcript in context, and so forth? If not, thank you for presenting it.

> They then made plan to inspect the hull after dive 83. But instead they left Titan winter on the parking lot in Saint Johns where it was not protected from any exposure because that was cheaper.

The things I'm working on have a much lower (zero?) chance of death but this is a tale as old as time. _Looks longingly into the backlog..._

> This was a disaster of organization with messianic CEO dismissing all concerns with bravado

While I love this list, I do not like that you are blaming everything on CEO.

This company followed current ethical policies, and used them to exclude actual experts and skilled people. CEO operated in environment that supports this behaviour, and only cares about irelevant metrics!

Not surprised this is posted by a throwaway account. I would think this is Rush himself, if he was alive of course.

Start-up idea: LLM service that will post online to defend you after you die.

Or nice idea for a new black mirror episode.

In the Year Of Our Lord 2025, there is no difference between the two.

various estates (e.g. Tolken, etc) already have trusts that can and do hire lawyers and even marketing firms.

in this case you'd just hire a marketing org that uses AI a lot and hope that the trust has enough money to keep them doing their job for a while

Maybe listen to some of his interviews. His opinion about "old" experts is on record. And old Oceangate HR pages are still in archives.

But again, this is not juzt about CEO (he deserves the blame), but why he was able to operate for so long, and why his critics vere silenced!

his critics were silenced? bro they were loud as hell and consistently so.

the dude did everything he could to fly under the radar, but only just enough. it is why the report is so damning -- much of what he did was just blatantly, balls-out bad, and all of the signs were there consistently.

But that person is right. Co owners, board and even layer that knowingly helped to relatiate against whistle blower with fake accusations are all guilty too. At least in the ethical sense.

Rush is dead, so it is comfortable for the above to blame only him.

The board knew about the issues. The layer knew the accusation is fake and designed to shut up the whistleblower.

Its fair to blame Stockthon because he fired or treated to sue everyone who didn’t buy into his spiel about this being revolutionary disruption of private submarines. Leves of staff rotation were insane in this company, their lead eng. at the time of implosion was a software dev because everybody else left or was laid off.

High staff rotation is typical for such companies. Qualified person with other options, will not work in such toxic company, after CEO had racist and ageist rant!

My point is where such companies get funding?! They produce garbage and should go bankrupt pretty fast! But somehow "investors" kept feeding them money, because they are super "ethical"!