"Titan" submersible investigation begins [28-June-2023]

I was going to post this as a follow-on in the original thread but I see that it’s closed. Pieces of the imploded submersible have been retrieved and have arrived in St. John’s, Newfoundland. The investigation will be a joint US-Canada effort.

The article below has a few pictures and videos. The front titanium end cap appears to be intact, but from the way it’s being hoisted the circular window is gone. The other end cap is said to be intact as well. The carbon fiber hull is shredded, but one piece that was pictured is surprisingly large considering the incredible forces that tore the vessel apart.

From the artical: All five people on board are believed to have been killed by the implosion.

WTF? Did they possibly make it to the surface and died there becasue no one was looking for them? Kill each other one by one? Run out of oxygen and then it imploded?

I assume it’s standard journalistic practice (e.g. “John Doe, found standing over Richard Roe’s body holding a bloody hatchet, is suspected of the murder.”)

Not enough lifeboats on board. When will they learn?

From the pics i have seen, the large pieces of fiberglass seem to be from the rear hpusing the encased the mobility gear. I haven’t seen any fiberglass that looked like part of the pressure vessel.

If anyone does, please link it?

Moderating: The prior thread created a lot of issues for the moderation team, and I request that you try to avoid that in this one. Please keep this thread to information about the investigation and recovery of stuff. Speculation about what went wrong is a natural part of that. But if y’all could keep statements about how rich people deserve to die in a pit thread (start one if there’s not already one) the mods would appreciate it.

I wonder if they removed the window to make it easier to hoist the titanium cap.

IANA enigineer, but at the force subjected, wouldn’t the fiberglass vessel pretty much shatter? There’s might not be any pieces big enough to salvage.

Hopefully not. Remember that window was only rated for about 1/3 of the depth that the Titan actually went to–so there is a fair amount of speculation that it broke.

I’m confused. It sounds like you’re hoping the window was the primary point of failure that caused the loss of the sub, i.e. you’re hoping the recovery team didn’t need to remove it (for hoisting purposes) because it had already been pushed into the interior of the sub during the implosion.

Can you clarify your meaning?

FWIW, the pressure vessel was carbon fiber, not fiberglass, though they’re both composite materials made via similar techniques. I’d expect that in either failure mode, either the window or the hull itself, the resulting force of pressure equalization would have shredded the hull. Composite materials are very strong right up until the moment they’re not, unlike metals which (if properly engineered) tend to bend and buckle rather than shatter.

As to the recovery team removing the window (or pieces thereof) to facilitate lifting … IMO that is extremely unlikely.

Whatever happened down there, any disassembly of the components except in a lab after everything has been measured & photographed and … to a T would be completely contrary to standard accident investigation technique.

Photograph the parts as they fell to document their spatial relationships, then bring each piece up as unmolested as possible. Even if you have to build special tools to cradle the chunks.

The fact they threaded a hoisting strap through the porthole opening pretty well guarantees there was absolutely no window (or fragment) present where / when the end cap was found on the seabed.

I spent the last 3 years working on computational fluid dynamics, albeit for situations not much like this believed implosion. Of course I’ve been watching news and pondering what went wrong from that point of view.
I’ve read, from sources who at first glance would appear worth paying attention to, that the implosion would have taken only seconds, or less than a second, or less than 40 milliseconds, or less than 1 millisecond. There’s a video of a railroad tank car “imploding” (more like “collapsing”) as a vacuum is drawn, which has at most 15 psid doing the work – and probably much less than that toward the end as the interior gets smaller. I read that the seawater would rush in radially at 1500 mph. I read bodies would be reduced to a murky stain in the water with even bones reduced to dust. I read that an implosion of this sort could damage and rearrange things in its vicinity.
But they’re pulling things up now, and some not very informative photos appear online at reputable news outlets. One looks to me like one of the two end rings bonded into the tube assembly, not an end bell with or without a window. The others look like parts of the vehicle that were outside the low pressure vessel.
I’m struck that things don’t look especially torn up, as though the implosion was not sufficiently violent to break up mechanical assemblies just a couple feet outside the vessel. This is making me think it was much less violent than the most extreme examples.

Yes, I’d forgotten that the tail section was just an unpressurized fairing. The article states that the OceanGate name was covered up as that large piece was being hoisted off the ship, and that fairing was where the name was located. I suspect that any pieces from the carbon fiber part of the pressure vessel are very small indeed. In a video that someone posted of a carbon fiber tube being crushed in a hydraulic press, the tube completely disintegrated. As @Mr.E notes, when composite materials fail, they fail catastrophically.

(Nitpick: carbon fiber, not fiberglass, as someone already noted.)

ISTM that PT meant he hopes no-one removed the window just to
facilitate recovery because that’d be potentially destroying evidence.

ETA: i see LSLguy has already addressed this issue, in other words, Ninjad.

I can’t speak to PastTense, but i hope they didn’t destroy evidence of whatever happened by disassembling pieces that were together when found

Sensible. I figured they might have made a note that the window was intact and then removed it to facilitate hoisting, but surely passing a sling through the portal wasn’t the only possible way to hoist that end cap.

Also sensible. I wonder if the window was blown outward by a water-hammer effect when the hull violently imploded. It’s designed so that exterior water pressure forces it snugly into its conical seat, so one would expect that they only added enough exterior clamping/retention hardware to keep the window from falling out until they get the whole sub underwater. that exterior hardware almost certainly would not have been designed to resist such a violent impact from the interior of the sub.

Here are a few photos. One is obviously the end bell minus its window, another looks like a tube end ring with distant house visible through it.

I can’t really tell much at all from the photos I can find. The fairing and whatnot within it could certainly have come out that intact after the pressure vessel imploded; even after that went the force might not totally destroy the mechanicals and titanium cap, but rather just project them away, since they were not meant to resist pressure at all from inside.

The other day I noted this quote from someone who’d gone on a ride on the Titan last year:

So, it might’ve been that, or maybe something else LIKE that. If they can actually pull up most or all of the debris, I have little doubt they’ll figure out the point of failure. It’s not a big or complicated thing.

It is perhaps easy to forget that this wasn’t the vehicle’s first trip; it made three previous trips down and got everyone back alive those times. I am suspicious, then, as to whether OceanGate was conducting appropriate inspections, or doing NDT or what have you, on the vehicle. Clearly, it WAS capable of descending to the Titanic and withstanding the pressure. The design was validated. What it apparently was not capable of was doing it a fourth time. That just screams one of two things to me:

  1. Structural fatigue, or
  2. Negligence in preparing the vessel for this trip.

Or a sperm whale got pissed off at it.

I think we’ll get some answers, but not necessarily a full picture. At a high level, if we’re lucky we may find out whether it was the viewport or some component around it that failed, or whether it was a junction between the composite hull and the titanium end caps, or whether the hull itself just collapsed. But I suspect that a lot of the report will be based on input from engineering experts on the mistakes that they believe were made, without necessarily a lot of supporting evidence. We’ll see.