Fiber composites are complex. Carbon fibers can be made to withstand compressive loads in that you make composites with the CF and other materials. Even so carbon fibers are about half as strong in compression as tension. Even so, carbon fiber might have a specific strength of around 3000 kN-m/kg, steels might be around 63 kN-m/kg. So it's not as simple as "carbon fiber isn't as good in compression as tension, never use it in compression." A lot of current research in aerospace is to produce better manufacturing methods and resins for carbon fibers to phase out aluminum and steel parts. Mostly in tension yes, but compression too, all parts without preloading generally are some degree in compression during their stress lives.

Should he have bought expired carbon fiber for a submarine? No. Is carbon fiber completely absurd in submarine usage? I don't imagine so. Though steel is plenty fine for a submarine, normally the hard part is the sinking by design, not the floating, so weight savings aren't super important.

First, he was an aerospace guy and several things he's said make me think he was sort of chauvinistic about deep sea exploration in general, stuff like "It’s perfectly fine. Having all these certifications for airplanes is one thing, but the carbon fiber was perfectly sound."

Second, his business model, taking four people down with him in something other than Cameronesque claustrophia, and doing so without the cost of owning a proper launch vessel, instead renting any ship that could hold and then monitor his launch sled, meant it was critical he make something big and light, by deep sea submersible standards, that was at least nominally expected to handle the load. Shit, I guess in some sense, he did, since it went down and back two or three times or whatever. At the absolute best, though, he'd invented a disposable sub, and he clearly didn't worry about that limitation any more than the rest.

And that they convinced multiple billionaires, who are generally assumed to be smarter and better educated than the rest of us, to step aboard that blatantly-unseaworthy deathtrap.

Stress fatigue and fractures doesn't show itself after one dive without completely tearing down the craft and inspecting components - and this was probably the deepest dive they've been on.

pressure increases on a log scale the deeper you go, so you need to account for that, evidently, they did not account for it, and they also failed to understand requirements for regular teardowns and inspections of prototypes.

Honestly I don't find it surprising at all.

There are multiple times where people have died due to fractures as a stress fatigue in different areas.

I remember a story about the crash of United Airlines flight 232, in where a DC-10 suffering an undetected stress fracture after many flights finally broke an engine to the point of it severing out all hydraulic lines to the control surfaces - they had to try and land the plane via throttle. It's actually a very interesting story if you want to look it up - they even made a movie for it.

The issue here is the number of dives it took before something failed catastrophicly - you usually engineer it to withstand the stress for X number of dives - 6 dives are far too few and and it is indicative of poor design and poor maintenance. - compare UA232 where it only happened after multiple years and 200+flights before it finally failed catastrophicly.

Problem: exists for decades and has not been solved by experts with tons of funding in all that time.

Redditor with zero knowledge or context: Why don't they just do X, Y, Z? It's so easy 😏

It's worse than that. They're narcissistic and think they have the answer to every problem. I worked for a boss like this who had Aspergers syndrome (undiagnosed, but clear case)

He literally had bumper stickers made up with "[his name] is the answer" - he wasn't joking. If there ever was a problem he would immediately solve the problem in his mind, and that was the way we MUST do it. He would not accept rationalization as to why that might be a bad idea. I learned real fast not to tell him we had a problem.... until I already had a proposal, who was involved, and costs involved to fix the problem before he had a chance to solve the problem himself.

Both. The drive to be a cheap pos caused him to believe he knew more than he did.

Not with that attitude.

Actually, money could have been saved... here's why:

1. The US Navy's submarine detection network heard a "boom" on the day of the implosion, which they kept close to their chests...
2. Sounded the alarm, they spent money and resources looking for something they were almost sure was lost...
3. After the expiration of time when the submarine "could be recoverable" was when they said "well... we did heard something the other day"...

Imagine the other possible scenario where the say on the first day "Hey, the sub imploded, we heard it on our underwater microphones, we won't spend money looking for these people..."
And then a future investigation reveals that they got stuck somewhere or lost power but were "buoyant" for 48 hours or so, and died for lack of oxygen when no one was looking for them.

Can you imagine the lawsuits?