Tourist submersible visting the Titanic is missing 101

[TigerGuy]

This video helped me understand implosion better than anything else I found.

https://www.youtube.com/watch?v=8tW4zfTeJqM

Why is anybody thinking they had attempted to abort and surface? Wasn't there an absence of communication?

 

[Pinwards]

I think that is coming from James Cameron's interviews where he said there was evidence/reports that they had dropped their weights and started to ascend. He had apparently spoken, in the early hours of the event, to insiders who must have provided that information, as I don't think any evidence or statement to that affect was ever released publicly. We probably won't know for sure until when/if a report on the investigation is ever released.
#

 

[Sym P. le]

From TigerGuy's link start at 6:22 then skip to 7:20.

 

[JStephen]

In the James Cameron interview, he said it "had been reported" that they had released weights and started up, and the only way anyone would have known that was if they had communicated that to the surface from the submersible. So if that was the case, there was some conversation which no one has publicly reported. And makes me curious what else was in that conversation. Meanwhile, the data/voice recorders from the surface ship is part of the investigation.

In the Hydraulic Press Channel video above, note that his sub is long and thin and a single piece of metal, so the failure mode is not necessarily the same as the Titan's. (If it was, the Titan would be on the ocean floor in one piece.)

 

[dik]

Does anyone have an idea of what the stress-strain curve of the carbon composite was?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[LittleInch]

Not actually certain the designers of the vessel knew either, given they had only 6 weeks to design the thing.

Given the immense depth I'm not sure how fast any text messaging worked, but I think it is rather slow, so "conversation" is probably pushing it a bit.

But one or two words - Coming up or similar might have made it before the implosion.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[kjoiner]

I just saw this story where Titan malfunctioned on a previous dive. The ballast weights would not release so they had to rock the sub side to side to get them to drop off. Sounds like a major red flag since Stockton Rush said there were 7 different ways to drop ballast for ascending.

https://www.yahoo.com/news/titanic-sub-once-malfunctioned-couldnt-140951310.html

 

[IRstuff]

It has been mentioned above and elsewhere about the diesel effect heating the air. They did have bottled oxygen onboard as well, and it occurs to me that if those bottles ruptured, there could be a considerable amount of combustion taking place very quickly in a very confined area. Rupture of that cylinder would also heat the cylinder itself, for that matter.

This and "diesel effect" are all irrelevant; the implosion lasted maybe 2 milliseconds, so anything that could have possibly happened was snuffed out within that time. You need a fairly high compression ratio, so say 6:1; that means the containment vessel was nearly completely crushed at that point, so whatever there might be to explode would have attempted to explode, but the surrounding water would have crushed it out in well under a millisecond

Moreover, dieseling requires a certain stoichiometry to occur, so unless there was something flammable in the air already, nothing would have happened anyway.

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[waross]

IR, I used dieseling to illustrate the temperatures rise possible.
You mentioned a compression ratio of 6:1 (typo? 16:1?) Not to judge. I am famous for much stupider typos.
Here the compression ratio was probably in the order of 300:1 (The exact depth of implosion is uncertain.)
What is the theoretical temperature when air is compressed 300 times from 5 degrees C ?
The victims lungs would not only be collapsed but may also be very hot.
By the way. Has anyone found a good source for the internal dimensions of the sub?
All I have found is the overall outer dimensions, repeated in multiple sites.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[IRstuff]

Not a typo; I was misremembering the typical compression ratio needed for diesel ignition, so I picked a low value. A much higher compression ratio would have eaten more of the timeline, making an ignition essentially an impossibility and moot. At 6:1, there's at least some chance of something happening, but the remaining timeline to complete destruction is so short as to make it completely academic and only of practical interest to slo-mo videographers.

As for the dimensions, we know that the cylinder walls were only about 5 inches thick.

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[Alistair_Heaton]

Wonder how they laid the carbon fibre, was it cam or hand? And what autoclave did they use.

 

[rodface]

Back of envelope calculation gives me 5.54 cubic meters of internal volume (work at bottom). I did not consider the height of the titanium interface rings which would give a little more L to the cylindrical volume. I also am treating the space enclosed by each end caps as being 50% of a perfect sphere.

From Composites World article:

> Length, 2,540 mm; outside diameter, 1,676 mm;

> Initial design work indicated that the hull, to be rated for 4,000m depth with a 2.25 safety factor, should be 114 mm thick or 4.5 inches, which OceanGate opted to round up to 5 inches (127 mm) to build in an additional safety margin.

Cylinder ID: 1676 - 127 - 127 = 1422 mm
Cylinder internal volume Cross-Section Area: 1588141.06 mm2
Volume of Cylinder: 1588141.06 x 2540 = 4.03 m3
Volume of a sphere with D = Cylinder ID: 1.51 m3

Total internal volume ~ 5.54 m3

 

[Cool_Controls]

The hull made by Spencer was not cured in a autoclave. This article gives a lot of detail on how Spencer built it Link. But this may not have been the hull in use on the last dive. This video shows the wrapping process for one of the hulls Link

 

[SWComposites]

debodine - just download the file and edit the file name by putting ".pdf" at the end.

 

[rodface]

Regarding the manufacturing process:

https://www.compositesworld.com/articles/composite-submersibles-under-pressure-in-deep-deep-waters

Regarding the laying process, I have seen the below press footage of what is presumably the beginning of the manufacturing process for the hull.

https://youtu.be/4PUTbK5AqY8?t=20

However all of this information could have changed, perhaps that video shows an older hull being built, etc. We have no idea what exactly was down there and the investigation will have to uncover the precise details.

 

[Tomfh]

I don't believe any of the carbon fibre shell remains in any reasonable sized fragments which are worth looking at or will tell you anything about the flaws int he material.

There will likely be pieces of the hull. Same as if you crack a walnut. The shell doesn’t vaporise

 

[MikeC88]

What is the impact resistance of CF like in this form?

My only experience is with thin walls (bike frames & paddles) but I noted in a video on YouTube by dallymd that a weighted mooring line has been thrown out to the sub 15:55 timestamp) and impacted the vessel.

In this case the weight hit the control section at the rear,not the CF passenger section, but it makes me wonder if this was standard operating procedure and whether the sub may have picked up damage.

But perhaps an insignificant observation

 

[SWComposites]

Max - good point about the failure criteria issue in the compression-compression quadrant. Per the CompositesWorld article linked way above, the Spencer built tube was designed using "micromechanics and FEA"; so it is highly likely that someone just dumped some fiber/resin or lamina properties into some codes and used Tsai-Wu failure criteria. UGH. There seems to be some confusion about who actually designed and built the composite tube that was used in the sub that imploded. At person/entity is probably lawyering up and keeping as quiet as possible.

 

[Cool_Controls]

I found this press release from 2021 Link notably Spencer Composites is not listed as a partner, but Boeing and NASA are listed as providing design and engineering support. So we really dont know how the failed hull was built presumably by Electroimpact and Janicki industries.

 

[Tomfh]

Do we even know which way the tube imploded? I've been picturing it the long way since there is more surface area along that axis. I guess it's possible it pancaked and the end caps collapsed together like symbols. Also, doesn't carbon fiber float?

How it failed would be very interesting to know. I suppose it’s possible that it crushed neatly like you mention, like the way you crush an aluminium can, but I suspect it failed more randomly than that. Once it began to fail (and where that initiated is the big question), other parts would have begun to fail near simultaneously. The whole thing was a very finely balanced series of stresses. If one part fails it becomes highly unstable.

Carbon fibre doesn’t float.