About the news of missing Titan sub

[Vanadium 50]

All fibres in that layup are running in the plane of the cylindrical surface, none are radial.

There is a cabin in the way.

The radial forces are transferred to the collar of the hemispheres and to some degree the hoop fibers.

And epoxy is strong stuff as well.

 

[Baluncore]

The fibres used should have the same temperature coefficient, young's modulus, and speed of sound as the epoxy filler.

There is a cabin in the way.

The radial fibres should cross the wall, stitching the layers together, to prevent delamination.

And epoxy is strong stuff as well.

Then why use the carbon fibre in a compressive orientation. It would be better to avoid the fibre which will progressively delaminate if the temperature coefficient, modulus of elasticity, or speed of sound are different to the epoxy.

 

[Vanadium 50]

It may not look it, but tensile strength is critical. Compression is not the whole story.

The problem is not that the hull might evenly shrink under pressure, killing the passengers. The problem is that it might buckle. That has compression on one side and tension on the other.

This is why the US Navy uses high tensile strength steel for its submarines. They have not lost a submarine in over 50 years, even after driving at least one into a mountain.

 

[jrmichler]

I used a unidirectional carbon fiber rod in an application where we needed light weight, high stiffness, and Euler buckling for overload. Since a design review raised concern about it breaking when buckling, I ran a test. A 15" length of rod needed to buckle sideways about 3", and it did not fail until bent far enough that the free ends almost touched. It failed in tension. The failure was a sudden brittle fracture with a loud noise and pieces flying across the room. The test was repeated several times, and each failure was on the tension side. The tensile failure was interesting because the specifications for the rod call for it to be stronger in tension than compression:

The rated compressive strength of the rod is almost two orders of magnitude larger than the compressive strength of epoxy. I believe the compressive force are supported by the fibers, while the epoxy prevents local buckling of the fibers.

Since we needed to convince a number of people, we made a video of the test. I knew that it would shatter, so was wearing goggles and heavy leather gloves. I did not realize that I was standing under a bright light that made me look like some sort of demented mad scientist on the video. Several years later, that video was still being shown to new engineers, apparently to warn them about the guy in that office over there.

 

[gmax137]

I did not realize that I was standing under a bright light that made me look like some sort of demented mad scientist on the video.

Any way you can share the video, or at least a still frame?

 

[phinds]

Oh, come on. Now that you've shared that it happened, you HAVE to show us so that we can warn the newbies about the monster in our midst.

 

[Baluncore]

The problem is that it might buckle. That has compression on one side and tension on the other.

The tension that prevents buckling under external pressure is circumferential, on the inside of the cylinder.

That inner layer has been pre-compressed and shortened by hydrostatic pressure from outside the vessel, which is not helping to increase tension in the inner layer to prevent inward buckling.

When tension is applied to the inner hoop, that inner surface would tend to be pulled away from the concave neutral layer. I would expect any inner tension to result in a further crushing of the outer hoop layers that are then under greater load, with a delamination of the inner layers, and a failure to prevent the buckling.

Since any inner layer hoop tension must be countered by outer layer hoop compression, I see no advantage in relying on tension to prevent inward buckling of external pressure vessels.

 

[jedishrfu]

Latest from WIRED on the OceanGate tragedy:

https://www.wired.com/story/titan-submersible-disaster-inside-story-oceangate-files/

 

[phinds]

Latest from WIRED on the OceanGate tragedy:

https://www.wired.com/story/titan-submersible-disaster-inside-story-oceangate-files/

Paywall

 

[OmCheeto]

Paywall

I got in without paying.

...
IT WAS TIME for the engineers to hand it over to OceanGate’s operations team for testing at sea. But there was another snag. David Lochridge, who oversaw marine operations at the company and who needed to sign off on the transfer, became convinced that Titan was unsafe. In January 2018, Lochridge sent Rush a quality-control inspection report detailing 27 issues with the vehicle, from questionable O-ring seals on the domes and missing bolts to flammable materials and more concerns about its carbon-fiber hull. Rush fired him the next day. (Although Lochridge later made a whistleblower report to the Occupational Safety and Health Administration about Titan, Rush sued him for breach of contract. The settlement of that lawsuit resulted in Lochridge dropping his complaint, paying OceanGate nearly $10,000, and signing an NDA. Lochridge did not respond to WIRED.)
...
Several former employees said they were neither shocked nor surprised at OceanGate’s deadly accident. Three had left the company on safety grounds, and two separately described Titan as a ticking time bomb.
...

Don't like what the engineers say? Fire them and then sue them if they mention it, even if they did it via proper channels. Another example of science and business by litigation. Disgusting that Lochridge lost the case.

 

[BillTre]

NDAs should not override considerations of safety or law. Unfortunately, that is the world we live in.

 

[Baluncore]

The Juice Media, on Australian Whistle Blower Legislation.

 

[gmax137]

Rush sued him for breach of contract. The settlement of that lawsuit resulted in Lochridge dropping his complaint, paying OceanGate nearly $10,000, and signing an NDA.

I had to read that a few times. Sounds like a case of "rich guy has better lawyers" rather than justice.

Where I worked, we were required by law to report unsafe conditions to the feds if our company didn't address safety concerns to our satisfaction.

 

[Rive]

Don't like what the engineers say? Fire them and then sue them if they mention it, even if they did it via proper channels.

Seen that attitude, and not just once.... This guy just had more money, bigger say in the company - and more victims....

 

[jedishrfu]

Its odd how sometimes these guys have names that relate to the tragedy.

Stockton Rush “rushed” things and took shortcuts.

 

[Astronuc]

Log of “Titan” Sub Crew’s Final Words Deemed Fake, Investigation Finds: Report
https://news.yahoo.com/news/log-titan-sub-crew-final-171107867.html

A purported log of the Titan submersible crew's final words has reportedly been deemed fake.

A federal team of investigators “found no evidence” that the five people onboard the Titan sub on June 18, 2023 were aware of the pending implosion, according to The New York Times.

The transcript, which began circulating online just days after the submersible went missing in the Atlantic Ocean, offered a detailed timeline of the supposed events and conversations leading up to the implosion.

“I’m confident it’s a false transcript,” said Captain Jason Neubauer, a retired member of the U.S. Coast Guard who serves as chairman of the Marine Board of Investigation. “It was made up.”

federal investigators obtained records of the real communications between the submersible and the Polar Prince, which apparently disprove the viral transcript’s accuracy.

“Somebody did it well enough to make it look plausible,” Neubauer said.

James Cameron reveals devastating intelligence he received about doomed Titan submersible after disaster
https://www.independent.co.uk/news/...bmersible-titanic-investigation-b2560428.html

James Cameron Says Titan Sub Mission Shouldn't Have Been Allowed: They 'Broke The Rules'
https://www.yahoo.com/news/james-cameron-says-titan-sub-102608398.html

 

[Vanadium 50]

I find it interesting that engineers who warned of trouble don't want to be named, lest they be sued. I guess for being "insufficiently convincing".

 

[jedishrfu]

It might have to do with liability, culpability and delaying tactics common to these kinds of tragedies.

 

[pinball1970]

A $50m Lawsuit and a disturbing claim that the crew knew they were going to die.

"When the acoustic safety system’s alarm sounded, signaling the hull was “cracking under extreme pressure,” it prompted the pilot to release weight and attempt to abort the expedition.

The crew had no communications and likely would have had no power either. “Common sense dictates that the crew were well aware they were going to die, before dying,” the suit states."

https://www.independent.co.uk/news/...mersible-wrongful-death-lawsuit-b2592900.html