It's a good guess.

https://en.wikipedia.org/wiki/Byford_Dolphin

> Investigation by forensic pathologists determined that Hellevik, being exposed to the highest pressure gradient and in the process of moving to secure the inner door, was forced through the crescent-shaped opening measuring 60 centimetres (24 in) long created by the jammed interior trunk door. With the escaping air and pressure, it included bisection of his thoracoabdominal cavity, which resulted in fragmentation of his body, followed by expulsion of all of the internal organs of his chest and abdomen, except the trachea and a section of small intestine, and of the thoracic spine. These were projected some distance, one section being found 10 metres (30 ft) vertically above the exterior pressure door.

That's with a nine atmosphere pressure differential. The Titanic is at about 400 atmospheres.

That wiki page describes a decompression injury, which AFAIU is the opposite of implosion:

> This resulted in the chamber being explosively decompressed from a pressure of nine atmospheres to the one atmosphere of the unsealed chamber system.

Whereas an analogous description of the submarine implosion would describe the opposite, i.e. "explosively compressed from a pressure of one atmosphere to 400 atmospheres."

The point is the extreme, rapid force involved.

Imploding or exploding, nine atmospheres is gonna suck. 400 atmospheres is... like standing under a nuclear bomb. The good news is it doesn't hurt, at all.

Someone else on the thread posted a video of a one atmosphere implosion (https://www.youtube.com/watch?v=Zz95_VvTxZM). 400x the pressure here.

Indeed. I'd be curious if there would even be a body to find. I have to imagine it'd be compressed into paste. It's very disturbing to think about, but also a preferable way to die compared to suffering through 96 hours of uncertainty before slowly asphyxiating.

I tried to find [1] how much pressure explosion of a grenade would cause. It would take a lot of grenades to get to 400 atmospheres...

- [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5514183/#:~:tex...

I wonder if you even could, given the fact that that stuff is trying to get away from each other you'd have to get the timing right to a ridiculous degree of precision.

Why are people assuming this? How about a leak that fills the sub with water? Is a leak impossible to keep stable at those depths?

A slow leak that filled the sub would not necessarily have lead to the vessel's destruction.

That said, you can get leaks. I participated on a research cruise with a French submersible, and there was talk of small leaks with the main hatch seal occurring during descent. The "fix" was to go deeper so the pressure would essentially seal the hatch shut.

At 5800PSI, A leak with an area of 1/100th of a square inch would have 58 pounds of force behind the water coming in and a flow rate of about a half-a-gallon per second.

Sure I get that. A hole will be like a water cutter.

I was thinking more like a screw with resistance along the threads such that the pressure goes from 5800 psi to say 20 psi at the last thread or whatever. Then you might get a stable leak.

At that point, you're counting on the material that thread is sunk into to be capable of withstanding that pressure without brittle fracture, and from the wrong side.

A screw is there to resist being pulled out. If water got to those screw threads as you posit, that'd basically be like reversing the forces to which that fastener was meant to resist. You go from "big chunk of material to hold in screw" to "little triangular threadforms trying to stay joined to the material around them in spite of 5800 psi trying to transit a pressure gradient insisting otherwise."

I'm not saying it's impossible, I'm just saying if I remotely thought it was possible to end up in that situation, I'd be going back to the drawing board to try to rule out that possibility. My brain just shows me visions of a screw turned into a bullet that barely gets slowed down going through a human body after threadforms crush like tortilla chips, a water cutter blasting through somebody into the opposite ablating a hole and causing a cascaded failure that then shortly thereafter becomes diesel thoomp.

If you'll excuse me, I'm abandoning this train of thought.

It depends on the depth.

But if the leak is noticed at say 20m they would have surfaced.

A leak with the amount of pressure at 1000m would cause a high speed jet like from a water cutter. That in turn would cause the material around the leak to be ground away.

This is really bad for the structural integrity and boom the whole thing implodes in a fraction of a second.

> Why are people assuming this? How about a leak that fills the sub with water? Is a leak impossible to keep stable at those depths?

Part of this is the use of carbon fibre, which is a very brittle material. In bike frame failures, for example, carbon fibre doesn't tend to rip a little or bend, it often fractures greatly or even shatters.

Add the enormous pressure difference, and this is why most people assume instant catastrophic failure.

A leak at 400 atmospheres doesn't stay a leak.

That highly depends on the source of the leak. But if it does start to leak you better surface pdq.

They found a debris field. That's pretty conclusively not a slow leak.

i think any small breach is an instant implosion at 400 atm

Probably combusted? At 400 atms their biomass would compress into a gelatinous hydrocarbon fat blob with the oxygen present, resulting in automatic combustion. The amount of compression their bodies would experience is an order of magnitude greater than a diesel engine cylinder. The explosion would immediately be quenched by the surrounding water and the only thing remaining of the occupants would be ash.

This would happen on the order of milliseconds.

When it happened in that accident referred to elsewhere in the thread the water temp was elevated massively in that area (enclosed so measurable).

Their blood would combust instantly.

They found cooked blood after that accident too.

Edit: https://en.wikipedia.org/wiki/Byford_Dolphin

That accident was only 132 psi. A diesel engine causes combustion at around 300-500 psi. This accident was 3000-6000 psi, so I think it's safe to assume that the organic matter would combust almost instantly.

Why would anything, except possibly something particularly easy to ignite on a surface, ignite? The only thing being heated dramatically is the air, and a whole lot of cool water would be spraying everywhere at the same time.

Same way bubbles imploding have localised temps hotter than the sun, just that writ larger and at 400 times atmosphere.

This: https://www.dailyrecord.co.uk/news/uk-world-news/divers-bloo...

was 'only' at nine atmospheres the titanic is at four hundred!

Went to see titanic only to get turned into diesel, horrible fate

Someone put Mythbusters on the case

Yeah, it would be curious (if morbid) to see what happens to something like an animal carcass. In most cases of submarine failure at depth e.g. the USS Scorpion no bodies are ever found.

They sorta did one like this ...

https://www.youtube.com/watch?v=LEY3fN4N3D8

Adiabatic compression of air to 400 bar increases the absolute temperature by about a factor of 5.5, which would be the temperature of a flame.

Water, fat, etc are not nearly as compressible as air, and the thermal mass of the air involved would be a couple orders of magnitude lower than everything else.

400 bar is (from some quick searching) fairly mild for industrial hydraulic systems, and hydraulic fluid doesn’t get especially hot while in use.

On the other hand, a leak in a pressurized hydraulic system is extremely dangerous if you’re around it due to the extreme velocity of ejected fluid.

Hydraulics don't get hot while in use unless you introduce air into the system, in which case they do get hot and explosive. This is called hydraulic dieseling and microdieseling. The passengers would have been surrounded by oxygen and CO2 gas, and the oxygen tank would rupture as soon as the capsule imploded.