Titanic tourist sub goes missing sparking search

[Dan]

And what was the determined point of stress failure?

Using carbon fiber composite hull as pointed by James Cameron around 7 minutes of video interview, below (posted by @O-ring upthread). Unlike metal that can go many pressure cycles (as long as the stress is applied under its yield stress and within the linear stress-strain curve), carbon fiber composite would delaminate and break like glass when pressure is applied from outside.

The right application of carbon fiber composite is when the pressure is applied from inside, like in the airplane hull.

 

[chillyinCanada]

For what it's worth, I concur with this analysis:

​

One point is worth clarification, "off the shelf" components. A great number of "off the shelf" components are used in commercial and military aircraft, nuclear submarines, saturation diving systems, and DSVs (manned Deep Submergence Vehicle). However, there is a HUGE difference between industrial and Mil-Spec grade products like Swagelok, CPV, Airpax, and DG O’Brien versus consumer products like game controllers and big box hardware store parts.

Oh, he's angry

 

[Wookie]

I thought it was only 13 prior Titanic dives, not counting shallow test dives in Puget Sound and deep dives in the Bahamas. Were there 10 test dives?

Does the number matter?

 

[Wookie]

Does the number matter?

Actually, with Carbon Fiber (I’m no expert) the only thing that matters is the number.

 

[chillyinCanada]

Actually, with Carbon Fiber (I’m no expert) the only thing that matters is the number.

It was going to fail. The only thing that mattered was the time.

 

[chillyinCanada]

https://www.cbc.ca/news/canada/newfoundland-labrador/oceangate-expeditions-search-and-rescue-costs-1.6888482

 

[Russjstewart]

Will there be criminal prosecutions?

On Saturday, Canadian investigators from the Transportation Safety Board were dispatched to St. John’s to gather information and conduct interviews, the agency said. The Royal Canadian Mounted Police confirmed that it’s determining whether a criminal investigation is warranted but declined to comment further.

Titan Disaster Probes Face Tricky Test of Criminal Liability

By Joel Rosenblatt and Teresa Xie (Bloomberg) — US and Canadian officials are looking into what went wrong in a commercial deep-sea adventure and whether crimes were committed that led the...

gcaptain.com

 

[makar0n]

https://www.cbc.ca/news/canada/newfoundland-labrador/oceangate-expeditions-search-and-rescue-costs-1.6888482

"Privatize the profits, socialize the losses"
Lemon socialism, underwater billionaire edition.

 

[HalcyonDaze]

Does the number matter?

Well, we are seeing claims that the submersible's carbon fiber hull was de-rated from 4,000 to 3,000 meters after the test dive series and needed repair work or possibly even replacement. If that happened after 10 test dives over two years, inspection and repairs were done, there were 13 dives in two years on Titanic, and there was no inspection or repair of the hull before the last dive ... that raises a big red flag as to OceanGate's operations, and further reinforces the assessments of the sub not being suitable for repeated dives.

 

[broncobowsher]

I'm still trying to understand the use of carbon fiber. Going the opposite direction, Carbon fiber wrapped gas cylinders they are a thin walled aluminum cylinder that can't take the pressure, but carbon fiber is wrapped around it to hold it together. The aluminum layer is what makes the cylinder gas tight, the carbon fiber keeps if from failing. And many, if not most, are not rated for in water service as water gets into the fibers. Yes, there are some diving rated carbon wrapped cylinders.

As I understand it Carbon fiber layup is generally a bit porous. They are just fibers and need a resin to glue them together. The rule I know of is the less glue, but still enough, is best for strength to weight ratio. But that is just a layer of glue on the fibers. It is not a solid block of resin that happens to have fibers in it. If you look at a typical fiberglass boat (glass fibers instead of carbon) it is typically referred to as Fiberglass reinforced plastic. The plastic being the main component, the fiberglass being the added structure. The opposite of carbon fiber where I typically know of vacuum bagging a part for the reason of removing the plastic resin as much as possible.

Now I can assume that the carbon fiber layup was done with a heavy resin to fill the voids, but that weakens the carbon fiber layup and adds weight.

I can't help but to think that the layup isn't a sealed and solid mass. Add pressure, and cycles, microscopic porosity through the structure. I just can't see anything good coming out of it.