Tourist submersible visiting the Titanic is missing Part 2 69

[waross]

The simulation seems to mimic an explosion, rather than a body.
A slow application of pressure will compress the air in the lungs, throat, etc and any gas in the intestines.
The body will collapse but still be recognizable.
We have all seen movies where a body explodes in a decompression chamber.
That is when the pressure is released, not when the pressure is applied.
Is it reasonable that the inertia of the imploding water will generate a great enough transient over-pressure that the release of that transient will cause a complete disintegration of the body?
I would expect that the limbs may be much less affected than the torso.
And, yes I realize, that this just addresses the pressure effects and does not account for debris impacting the bodies.

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

 

[1503-44]

Waross...human body does not resist water pressure transients. Every individual cell and enclosed structure imploded then anything remaining exploded. Nothing but soup. Basically indistinguishable from the surrounding mud, unless you have a mass spectrometer. Put a raspberry and 100ml of water in the blender.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[hpaircraft]

...Given that the hull was wound by a very reputable and experienced manufacturer of composite structures, I still maintain that failures due to a deviation from standard practices in the carbon fiber section itself are not likely. Certainly possible, but not likely...

Except, of course, the fact that according to design tools developed and used by folks who actually make DSVs, they used less than half as much carbon fiber as they ought for the specified parameters and safety factor. As discussed earlier (might be in Part 1), according to the CET tool, for a safety factor of 2.25 their hull should have been 11.5" thick. Their actual 5" thick hull, if properly made, would only have had a safety factor of 1.3. And I suspect that the noises it is reported to have made had something to do with the actual safety factor being subunity.

https://www.compositeenergytechnologies.com/underwater-carbon-fiber-pressure-vessels/

 

[SwinnyGG]

Except, of course, the fact that according to design tools developed and used by folks who actually make DSVs

Right, but the manufacturer of the hull didn't design the hull.

Design scope and manufacturing scope were separate parties. All I'm saying is that I suspect (can't confirm. Suspect.) that this is a case where a part was made which conformed with the drawings, but the drawings were wrong.

 

[hpaircraft]

Right, but the manufacturer of the hull didn't design the hull.

As reported in Composites World:

...Spencer Composites’ president Brian Spencer signed a contract with OceanGate for the Cyclops 2 hull in early January 2017 and was presented with very basic — but challenging — performance parameters: Length, 2,540 mm; outside diameter, 1,676 mm; service pressure, 6,600 psi; pressure safety factor, 2.25. “They basically said, ‘This is the pressure we have to meet, this is the factor of safety, this is the basic envelope. Go design and build it,’” Spencer reports. And he was given six weeks in which to do it....

The operant part of that snippet is the direct quote from Mr. Spencer. It seems odd to me that they were given an OD not an ID to design to, but that's what's in the article. I have to assume that at least the direct quote is accurate.

 

[SWComposites]

Ok, this discussion is all just wild speculation.

We don't know who built the actual composite cylinder that failed (that entity has wisely kept VERY quiet).
We don't know what materials were used in the composite cylinder that failed.
We don't know who designed the composite cylinder that failed, nor how they designed it.
We don't know who bonded the Ti end rings to the cylinder, nor what adhesive was used, nor what surface prep was used (if any), nor how the adhesive was cured, nor what the actual joint configuration was (though there is some speculation above based on some poor quality photos.

But the first composite cylinder built by Spencer Composites (see the Composites World article referenced somewhere above) was designed with a rubbish failure criteria, using who knows what material properties (likely some vendor datasheet values), and likely did not account for fiber waviness in the cured cylinder which would be expected for a 5" cylinder (for some info on potential effects of waviness see this paper:

https://journals.sagepub.com/doi/10.1177/073168449201100202

)
And that first cylinder was apparently fabricated with a mix of wet layup plies for hoop direction fibers and prepreg plies for axial direction plies, so likely two different resin systems with who knows what effect on final properties (no way in hell I would do that mix without a ton of test data behind it).

Then the online video of the bonding "process" may or may not have been used for the cylinder that failed. But that "process" was not done in a clean room, did not appear to have any means of adhesive thickness control, did not appear to have any means to ensure lack of voids or other defects in the bond (all of which violate best practices learned the hard way over the years). And then the joint configuration seems to have a rabbet machined into the composite cylinder, which is insanity for this design - it creates a large stress concentration to create a delamination in the laminate. And while the joint "designer" probably assumed that the "bond" was just to "seal" the connection between the Ti and composites as the joint would be in axial compression under pressure load, they probably did not consider the stiffness and CTE differences between the two parts nor the effects of repeated load cycles on the "bond".

And lastly the arrogant reliance on "structural health monitoring" to ensure "safety" is use of a completely unproven and likely unsuitable technology, particularly for this application.

 

[SwinnyGG]

The operant part of that snippet is the direct quote from Mr. Spencer. It seems odd to me that they were given an OD not an ID to design to, but that's what's in the article. I have to assume that at least the direct quote is accurate.

Fair enough - this is information I wasn't aware of. I stand corrected. If that was the same process shared for the second hull which failed, sounds like Spencer Composites probably has some responsibility here as well.

 

[blakmax]

I'm wth you SWComposites. There is a lot we don't know but what we do know is very curious indeed. Your most telling comment was :

And lastly the arrogant reliance on "structural health monitoring" to ensure "safety" is use of a completely unproven and likely unsuitable technology, particularly for this application.

As previously discussed I don't think the passengers would have had time to discuss the last acoustic indication of structural activities.

There are3 so many factors with relation to design of the composite structure, design of the adhesive joint, composite manufacture, surface preparation, cure cycle management for the composite and the adhesive, there are many aspects of this project that one could readily attach the adjective "cowboy" to many of these aspects.

 

[blakmax]

Has ANY of the composite structure been recovered?

Blax

 

[IRstuff]

Given that they only recovered one of the endcaps, I'd say no, particularly since the composite was the most likely to be completely disintegrated.

The original hull appeared to have a titanium spool upon which the composite was wound, but the new one either didn't or it was removed after winding.

TTFN (ta ta for now)
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[Brian Malone]

The New Yorker magazine has a very detailed story on OceanGate and describes many of the items David Lochridge was concerned about and insights into the operations at OG. The magazine website has a paywall but I believe you can view a limited number stories before a subscription is required.

https://www.newyorker.com/news/a-re...submersible-was-an-accident-waiting-to-happen

 

[Brian Malone]

It is rather disappointing to read some parts as it is apparent Stockton Rush really did not apply his engineering knowledge on many aspects of the development of the Titan submersible to ensure safety. He really got hell bent on achieving his vision on submersible design. As others have already noted, Stockton was free to risk his own life as he so wished, but he crossed a moral and ethical line by using deception on the safety of the sub's design and put other people's lives at risk. The whole engineering leadership/team at OceanGate is culpable as well. They must be bearing an extreme load of guilt. If not, they are really callous.

 

[IRstuff]

he crossed a moral and ethical line by using deception on the safety of the sub's design and put other people's lives at risk.

We don't know what he actually believed; even the most technical people can self-delude. He might have truly bought into the notion that everyone else in the world was wrong and he was the only one that was right, and that his craft was not risky. After all, he piloted the Titan himself, and unless he had a death-wish, he would not have knowingly risked his own life unless he was just cuckoo.

TTFN (ta ta for now)
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[Brian Malone]

IRStuff yes, you are correct, I cannot say Stockton willing deceived anyone. He and/or the OceanGate engineering team definitely ignored many red flags. I previously defended his actions because he did pilot the Titan and that indicated he trusted the engineering, assembly and materials - total respect for those who build and pilot their own airplanes, subs, and rockets! But yet there seems to be information missing on where his confidence came from. OceanGate engineering studies and test results? Contracted design and FEA? Industry guidance papers? (Likely not) I don't think he had a death wish but he trusted the sub and appears to have bulldozed anyone who was contrary to his opinion.

 

[IRstuff]

I used to be a firm believer that the objective truth would be easy to see, particularly for engineers, but it's become obvious that biases and beliefs can run roughshod over objective truth and lead to fallacious conclusions. Rush argued that regulations and testing weren't necessary because most incidents were not due to structural issues and therefore such regulation was overly burdensome and stifling innovation; but his biases failed to see that correlation was not causation, and it was the burdensome regulation and testing that prevented the structural failures so that all was left were the human factors. It's indeed sad that people died because of his delusions.

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[SwinnyGG]

The original hull appeared to have a titanium spool upon which the composite was wound, but the new one either didn't or it was removed after winding.

Both were mandrel wound, mandrels removed after autoclaving.

The original hull appeared to have a titanium spool upon which the composite was wound, but the new one either didn't or it was removed after winding.

My read on this was/is that while he had some engineering training and worked in engineering-adjacent fields (he was apparently briefly a test engineer on the F15 program in the early 80s), it seems like a case of someone who had some engineering training and experience but worked on an assumption that because they had experience in one field, that experience applied equally to all fields. Speculation of course.

 

[Brian Malone]

So far there has not been any indication Ocean Gate ran any full-scale tests to failure to check their design calcs and verify the capability of their Real Time Hull Monitor system - thus, it does appear Stockton Rush did suffer some self-delusion on the safety of the sub's design. Ego can only provide so much confidence - something else fuelled his trust in the sub. After a few successful dives did he become totally complacent to the magnitude of the force involved with an implosion? You guys have provided the calculations and analogs that show tickling the implosion dragon is/was not smart! Did his misplaced confidence and academic credentials and strong personality kowtow the rest of the OG engineering team (except David Lochridge)? Mention has been made of the team having young possibly less experienced engineers, but was this true for the whole team? The director of engineering, Tony Nissen, is no neophyte. The New Yorker story does indicate at least one member of the board of directors used his Coast Guard expertise to craft the business model to slide through regulatory loopholes. The BOD probably was on board and with confidence expressed and supported by top management the stage was set for tragedy. Certainly, not all BODs are technically astute or totally savvy to all company operations but if there was concern from the BOD it probably was minor. If there was an error of group think at OG then it parallels the error mode created by Denney Pate and the FIU pedestrian bridge failure.

 

[IRstuff]

while he had some engineering training and worked in engineering-adjacent fields

He supposedly graduated from Princeton with a BS in Aerospace Engineering, so ostensibly had gone whatever the math and physics requirements were. Of course "Cee's get degrees" so we don't know whether he was a diligent student or not.

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[TigerGuy]

If he paid attention in his classes, he would have understood the cumulative effects of material fatigue. There is a reason passenger jets are in service for a limited time. Just like plane wings, titanium and carbon fiber do not self-repair after they crack.

 

[TugboatEng]

I do see fatigue being mentioned a lot. One thing to consider is that the number of cycles may not be relevant if this were a creep related failure. And that case, time spent at depth would be a greater contributing factor. Carbon fiber itself may not be sensitive to creep, but when you load composite structures and compression, the resins are forced to hold the fibers together. Together. In this case, the resin may have been sensitive to creep.

On that note, I wonder how an unreinforced acrylic cylinder would perform versus the carbon fiber in the similar situation.