Oceangate-gate....

Very sad. There will be a prolonged investigation if they aren’t found alive.
Both sides already sniping, I can’t imagine the cost of this rescue mission.
They should have called the pedo for assistance

 

Uh... by whom?

The company fought tooth and nail to make sure this sub was not classified as a passenger-carrying vehicle. Notice that all five individuals are referred to as "crew." I doubt any regulatory agency has any regulations to bear on it and no need to investigate the failure.

Oceangate itself could do such, but I kind of suspect that the market for deep-dive tourism is going to be toned down for a while no matter what they learn about the failure. I have doubts that any of their investors would be willing to pay for that failure analysis knowing it could be decades before people feel like trying this again.

The "crew" (probably) died doing the kind of high-risk adventure they were known to appreciate, and if by some miracle they are rescued? They'll have the best adventure story around for many years, well worth the cost of the ticket.

 

The ntsb

 

Why would they care? It didn't happen in the USA, nor did it involve a vehicle classified for passenger transportation.

 

My thought is that it was an accident waiting to happen.

The pressure vessel is made of carbon fiber composite, which is fibers of carbon held together by an epoxy matrix. Any bubble or flaw in the "cake" might not show up until after multiple pressurization and depressurization.

That happened with the De Havilland Comet in the 1950's and later on, the USN submarines Scorpion and Thresher. .

The deep of the oceans is very unforgiving.

 

2 former OceanGate employees voiced safety concerns years ago about the hull of the now-missing vessel

"The former employee became concerned when the carbon fiber hull of the Titan arrived, he said, echoing Lochridge’s concerns about its thickness and adhesion in his conversation with CNN. The hull had only been built to five inches thick, he said, telling CNN company engineers told him they had expected it to be seven inches thick."

"Lochridge brought up concerns that no non-destructive testing had been performed on the Titan’s hull to check for “delaminations, porosity and voids of sufficient adhesion of the glue being used due to the thickness of the hull,” the suit says. When Lochridge raised the issue, it says, he was told no equipment existed to perform such a test."


OceanGate was warned of potential for ‘catastrophic’ problems with Titanic mission

 

Carbon fiber should have never been used for the pressure vessel. Unlike steel or even aluminum, it is subject to brittle fracture rather than deformation or ductile shrinkage under pressure before failure.

Aluminum, used in the Aluminaut, was not ideal eather. De Havilland Aircraft, in the 1950' discovered that cycles of depressurization and presurizatization, unlike steel, need not be close to the yield point before developing metal fatigue. On that account, the Aluminaut was withdrawn from service and now sits in a Richmond, Virginia museum as an exhibit.

 

This wasn’t their first rodeo

 

Maybe NOT. But it might likely be their LAST.

 

Possibly. Accidents happen

 

Yeah, it was one by design and waiting to happen.

 

Article I read said this was only that sub's 3rd dive to that depth. So no, not first but...

 

Ironically, it is believed that the sinking of the Titanic in 1912 was due the brittle fracture of the steel hull plates.

I remember there were experimental submersibles using crystalline glass spheres as pressure hulls. That too was abandoned due to glass being susceptible to brittle fracture especially from scratches.

 

Apparently, the ceo was onboard

 

Carbon fiber reinforced plastics might be light and strong, but is is no miracle material as often touted in popular culture.

Like all materials, it has its limitations and must be used with care. It should NOT been used to make such a pressure vessel on a deep sea submersible.

 

I'm remembering metal fatigue at crack-prone square corners being an issue on the Comet. And failure of brazed (not welded) pipe joints as one of several hypotheses for the loss of Thresher, which then imploded after sinking to crush depth. But I'm not recalling anything similar publicly known about Scorpion, and the possibilities seem to focus mostly on other equipment failures or enemy action while near the surface, not at depth. Yes, it was crushed at depth, but that was the end of the event chain, not the start.

 

I'm particularly puzzled about why anyone would push to use lightweight materials underwater. Unlike air and space vehicles, or even land surface vehicles, there is no advantage for an underwater vehicle to be light. The overall vessel needs to be as heavy as the water it displaces -- the passenger space is inherently much lighter than its displaced water -- so any lightweight construction necessarily needs additional ballast to make up for the reduced weight. One may as well go for the strongest material economically available, regardless of weight or density,

The only thing I see going for the carbon fiber of this vessel is the relative ease of fabrication of the large uniform cylinder body. Just spin a forming tube and gradually wind the carbon fiber tape in even layers to the desired thickness, possibly easier than fabricating a sufficiently uniform metal cylinder of that size and thickness. At the pressures involved, uniformity is critical. But as some articles mentioned, the company seemingly didn't do any form of testing to verify that structural uniformity or integrity of this part of the vessel. Or even know how to do it.

 

Well noted. A sphere is much more difficult to fabricate than a cylinder, but the sphere is much stronger, Two spheres with only wired communication between them and dual redundant controls would have been much safer, but they wanted physical contact.

 

the ceo (who is aboard) has made statements in the past that safety protocols were slowing innovation, and he seemed determined to circumvent them. poor judgement?

a reporter who was on one of the previous dives said he had to sign paperwork exonerating the company from all liability, and that he understood the risks and dangers.

even a judge in a related court case said she might take him up on an offer for a free ticket to davy jones locker