Titanic tourist sub missing

[TellyKNeasuss]

Possibly, or perhaps the result of multiple dives.

We don't know what the maximum depth that the submersible could be expected handle. If it wasn't much more than the depth of the Titanic, material fatigue could have occurred. It is my understanding (from only a short time trawling around the Internet) that the rated depth of military submarines is (depending on the country) 1/2 to 2/3 of the depth that the designers believe to be the crush depth of the submarine. I know that in the USA firefighting equipment is normally designed to be able to handle at least 1.5 times the rated capacity (and fire departments normally don't exceed 90 percent of the rated capacity except in life-or-death situations).

 

[dudalb]

Ah yes and the first talking head on television mentioned the Byford Dolphin, my go to example of "They way you don't want to die" as a comparison.

In War it is even worse.At least the people here did not have to go through a depth charge attack.
Seeing "Das Boot" back in the early 80's convinced me that if I went into the service, it would not be in Submarines...

 

[dudalb]

"Yeah, remember all that **** we were saying about timed banging at regular intervals consistent with Naval protocol? Turned out we were just making **** up. Looked real busy though, didn't we?"

And anybody who ran Sub Detection gear in the US navy can tell you, the "Silent Deep"is anything but silent

 

[jimbob]

Carbon fibre seems an odd material choice, given what I thought it's properties are..

And relying on acoustic reports because one cannot scan through 5" of carbon fibre composite is not a good reason.

Design for testability is key to safety-critical reliability.

It does seem to have a similar approach to engineering risk and where novelty is appropriate to SpaceX.

 

[Dr.Sid]

So I guess the carbon fiber failed after all. Well, that would be very quick death.

 

[LondonJohn]

With any luck it happened so fast nobody even realized there was a problem.

It would've done. They might have heard a few worrying groans/cracks in the final 1/2 second or so, but once the hull was breached they'd all have (unfortunately, but gruesomely) been pulverised to minced meat near-instantaneously. The pressures would have been tantamount to jumping into a 50-ton auto-parts press just as it was descending.

And that, also unfortunately, is why they'll never recover any meaningful body parts. They'll probably find recognisable bits of clothing/boots, but the bodies themselves will have dispersed in very small pieces, soon to be reclaimed by the ocean.

I think all reasonably well-informed people, armed with the initial information set (especially the way in which they suddenly lost all comms from a redundant system), pretty much knew that this was a catastrophic implosion on day 1. But of course ethically one keeps trying to locate and rescue right up until one finds proof positive of the loss of the vessel.

 

[Foster Zygote]

That struck me as an oddity also, especially given the properties of carbon fiber.

Without credentials I didn't want to speculate about engineering matters, but it occurred to me early on (after reading about how the craft was designed) that even if the titanium parts and the carbon fiber part of the pressure hull individually resisted the pressure perfectly well, if they responded differently to the pressure in any way, it would be disastrous.

I hope Lochridge can be at peace knowing that he said and did what he could to prevent a disaster, apparently at considerable personal cost.

I've watched Formula 1 for years. I've seen how incredibly strong composite materials are, but I've also seen how suddenly and catastrophically they fail when pushed beyond their load limits. My wife is a materials engineer, and when she heard about the carbon fiber tube
capped with titanium hemispheres, she shook her head. That's a long ascent from the bottom, so even if they had warnings from the hull sensors, it seems rather optimistic to assume that they could ascend fast enough to reduce the pressure sufficiently before the structure failed.

I just watched an interview with both Bob Ballard and James Cameron, and they said that many people within the deep diving community had expressed grave concerns for the safety of the craft, primarily because of the use of two different materials in three different hull components. They talked about the fact that since the Trieste in 1960, there have been thousands of deep dives in manned submersibles with no loss of life up until this point, and how all of those craft had hulls made from a single, contiguous piece of steel or titanium. They also talked about how this craft had essentially no back up safety systems.

The only consolidation is that they most likely died so fast they never knew it was happening.

 

[dudalb]

Bob Ballard's opinions on deep sea explortation I will respect; James Cameron, not so much.

 

[LondonJohn]

It's possible, but I wouldn't call it pretty likely. There's a reason the word "implosion" comes up in such scenarios. If you're thinking along the lines of the hull being crushed like a beer can, that's probably not the kind of end result you'd see. Think instead of a balloon popping, except inward instead of outward. (It's not a great metaphor but it's the same kind of distinction. The air could leak slowly out the hole in the balloon but it doesn't usually play out that way.) Also, composite carbon fiber doesn't bend like metal. It's really strong but when it does break, it splinters apart almost like wood.

Yes. In this small pressure hull, a catastrophic implosion would have reduced the crew's bodies to piles of mush almost immediately. The pressure of the imploding hull, and the force of matter hitting the crew (which would be a mixture of pieces of the CF tube travelling at extremely high speed, plus water travelling at extremely high speed) would have torn their bodies to bits. The energy involved in an implosion at these depths is absolutely awesome.

(The only reason why in certain implosion-based submarine losses some of the crew survived the implosion is because there are multiple waterproof pressure hatches in submarines and SOP is to keep them locked shut as much as possible. So, for example, when the Kursk exploded at the bow end (which caused a blowback implosion once the hull was breached by the explosion), the crewmembers who survived for several days were all at the back of the boat and behind a number of locked hatches.)

 

[LondonJohn]

The cause of the banging has been determined to be two kids with snorkels and a fake shark fin.

SOMEONE CHECK THE POND!!!!

 

[Myriad]

Wouldn't that show up in test dives?

Not that they wouldn't respond differently, but whether the difference was significant with regard to integrity.

I'd worry most about some unforeseen cumulative change as a result of repeated differential responses to the duty cycle of pressures and temperatures. Some kind of "creep," speaking very generally. Imagine, for instance, a crack forming inside the wall of the carbon fiber tube, parallel to the curve of the wall, near where it's bonded (no idea how they're actually attached together) to one of the end caps, caused by differential expansion and contraction during changes of pressure and/or temperature. (It's hard to explain where I mean. Shove a movie ticket into one end of a full roll of toilet paper, between the paper layers, a half inch from the outer circumference. That's the place I mean.) The tube is spec'ed to resist radial pressure or tension across or along the whole tube, but perhaps unexpected tension across the thickness of one wall had an unexpected effect that wasn't tested for, and wouldn't be visible without removing the end caps.

Probably not specifically that, but something of that nature.

More tests at well above the expected pressure should have been done, in between manned excursions. Obviously, in hindsight.

 

[LondonJohn]

Coast Guard announced that the noises heard were probably had no connectinon to the Titan.

Indeed. Bear in mind that noises travel an extremely long way underwater. With extremely sensitive listening buoys, they could potentially pick up noises from a few hundred miles' radius. Could've been one of a large number of things. But it wasn't anything to do with the Titan.

 

[LondonJohn]

Carbon fibre seems an odd material choice, given what I thought it's properties are..

And relying on acoustic reports because one cannot scan through 5" of carbon fibre composite is not a good reason.

Design for testability is key to safety-critical reliability.

It does seem to have a similar approach to engineering risk and where novelty is appropriate to SpaceX.

In principle carbon fibre would be a totally acceptable material for that centre tube. We had a discussion about this yesterday. Basically, assuming that the tube was constructed out of properly-layered (ie at specific different angles per sheet overlay) CF with epoxy resin binders (standard for CF), and provided it was cured properly in an autoclave, it should have been extremely resilient to both compression and tension.

The problem, however, is that the laminate substrate flexes every time the sub descends and ascends. This can cause fatigue in the resin layer, and eventual delamination. Once a section of the tube becomes seriously delaminated, it's a prime candidate for compressive failure.

I was suggesting yesterday that at a bare minimum - given the massively extreme operating conditions of this vessel - the sub should have been completely stripped down after every voyage and very carefully checked over before reassembly, including ultrasound/x-ray checks of the carbon fibre hull tube. And I also suggested that a prudent operator might well consider completely replacing that CF centre tube after every 2-3 voyages. From the sounds of things, I don't think this level of scrutiny in maintenance was ever applied to the Titan.....

 

[LondonJohn]

I've watched Formula 1 for years. I've seen how incredibly strong composite materials are, but I've also seen how suddenly and catastrophically they fail when pushed beyond their load limits. My wife is a materials engineer, and when she heard about the carbon fiber tube
capped with titanium hemispheres, she shook her head. That's a long ascent from the bottom, so even if they had warnings from the hull sensors, it seems rather optimistic to assume that they could ascend fast enough to reduce the pressure sufficiently before the structure failed.

I just watched an interview with both Bob Ballard and James Cameron, and they said that many people within the deep diving community had expressed grave concerns for the safety of the craft, primarily because of the use of two different materials in three different hull components. They talked about the fact that since the Trieste in 1960, there have been thousands of deep dives in manned submersibles with no loss of life up until this point, and how all of those craft had hulls made from a single, contiguous piece of steel or titanium. They also talked about how this craft had essentially no back up safety systems.

The only consolidation is that they most likely died so fast they never knew it was happening.

Yes, the fewer joints the better in this situation. As you say, there were very obvious potential points of failure in both of the large circular joints either side of the centre tube, where it attached to the bow and stern titanium end caps. It may have been one of these joints which failed, or it might have been delamination failure of the cf tube itself. That's something the investigation should be able to figure out, seeing as (IIRC) they've already located both of the end caps.

 

[Orphia Nay]

Pure 100% copium. The sub is almost certainly a pile of scrap on the ocean floor.

Edit: the complete and total loss of communication despite said system having redundancy strongly suggests they suffered a catastrophic hull failure.

You were right.

5:16
Sounds weren't coming from the sub - US Coast Guard
There doesn't appear to be any connection between the noises and the location on the sea floor, Rear Adm Mauger says.

-BBC News

 

[jimbob]

I've watched Formula 1 for years. I've seen how incredibly strong composite materials are, but I've also seen how suddenly and catastrophically they fail when pushed beyond their load limits. My wife is a materials engineer, and when she heard about the carbon fiber tube
capped with titanium hemispheres, she shook her head. That's a long ascent from the bottom, so even if they had warnings from the hull sensors, it seems rather optimistic to assume that they could ascend fast enough to reduce the pressure sufficiently before the structure failed.

I just watched an interview with both Bob Ballard and James Cameron, and they said that many people within the deep diving community had expressed grave concerns for the safety of the craft, primarily because of the use of two different materials in three different hull components. They talked about the fact that since the Trieste in 1960, there have been thousands of deep dives in manned submersibles with no loss of life up until this point, and how all of those craft had hulls made from a single, contiguous piece of steel or titanium. They also talked about how this craft had essentially no back up safety systems.

The only consolidation is that they most likely died so fast they never knew it was happening.

Yes.

These days, there is no reason to have such experimental craft with humans in it as opposed to recording devices.

It might be novel technology, but it's not achieving anything novel.

 

[dudalb]

SO help me , James Cameron has become the go to interview as an "expert" on this.
It is like interviewing somebody who chartered and then flew as a passenger in a 747 as an expert on aeronautics.
God, I hate the age of Celebriity.

 

[LondonJohn]

Yes.

These days, there is no reason to have such experimental craft with humans in it as opposed to recording devices.

It might be novel technology, but it's not achieving anything novel.

Ah, but this vessel's entire raison d'etre was to allow very wealthy people to go and see the Titanic wreck with their own eyes (albeit via a very small porthole*).


*Incidentally, the porthole might have been another potential point of failure. I understand that it was built of thick perspex. But perspex is (very slightly) compressible, so it's really not the best material for this kind of environment. It's.... very cheap though. The gold standard would be something like a thick piece of clear sapphire cut from a single crystal. But that would be.... expensive.

 

[MarkCorrigan]

Despite everything I do hope the end was quick and they didn't suffer.

Based on what I've read death would have been instantaneous.

Again, despite the ghoulish nature of the journey in the first place and the serious problems with the company that made this slapdash plastic cup of a submarine, these are still humans who died and that is a tragedy.

 

[LondonJohn]

SO help me , James Cameron has become the go to interview as an "expert" on this.
It is like interviewing somebody who chartered and then flew as a passenger in a 747 as an expert on aeronautics.
God, I hate the age of Celebriity.

Oh but Cameron now really does think he's a bona fide expert on all things related to Titanic and deep sea exploration in general.

I've seen Titanic-related programmes where he gathers in a panel of (true) experts and goes over the sinking and the discovery etc. And because he's paid for all the computer modelling and scale models and impressive graphics etc, they all effectively defer to his grandstanding.