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  • Writer's pictureNed Patton

When Hubris Overtakes Reason – People DIE!

Well, this week, I just had to do this. This post is going to be about the tragic loss of the Titan submersible. This submersible was on its way down to the Titanic wreck site on the bottom of the Atlantic, in about 12,500 feet of seawater (3800 meters). This is deep, and the pressure at that depth is more than 6000 psi.

The reason I’m writing this of course is that it is the carbon fiber cylindrical section of the Titan pressure hull that imploded, killing all five passengers aboard. What I’m going to talk about is how this tragedy was so easy to avoid, if the CEO of OceanGate, Stockton Rush had listened to reason instead of having the incredible hubris that he displayed. He effectively killed himself and everyone on board, because he did not listen to reason and did not have the submersible classed by ABS, DNV, or any other of a number of subsea vehicle certification agencies.

A fairly brief description of submersible pressure hull design and fabrication is in order here. A pressure hull for a submersible vehicle for these depths is typically made from Titanium (6-4 ELI for those of you metallurgists out there). This is because Titanium has the highest strength to weight ratio of all engineering metals. I’m not going to get into a treatise on why Titanium here, I just wanted everyone to know what the typical construction of a deep ocean manned submersible looks like. The design itself looks a lot like a medicine capsule, it has hemispherical ends with a long cylindrical center section. This is the basic design of every pressure hull that has ever been successful, and is common design practice.

Usually, these pressure hulls are made from a very high strength, low weight material – hence Titanium for the deeper diving vessels. Alvin in fact has a Titanium pressure hull, built by my alma mater Southwest Research Institute. And the reason that I know about all of this and can write about it is that I was in that business for 10 years, and the guy who designed and had built the new Titanium Alvin pressure hull is a good friend of mine. And of course, the Alvin has been to the bottom of the Marianas Trench a number of times – the deepest place in the ocean.

This is typical of every deep diving what are called one-atmosphere submersibles. What this means is that the pressure on the inside of the submersible is one atmosphere, or the air pressure at the surface of the ocean. The depth rating of one of these vessels is based on the strength of the material that the pressure hull is made out of when the outside pressure is what pressure the water is at the depth where the submersible is qualified to dive. To figure that out, a good rule of thumb is that the pressure increases by about a half a psi per foot of water depth.

The design of the OceanGate Titan was somewhat different than the typical deep diving submersible pressure hull in that Stockton Rush used a carbon fiber / epoxy material for the cylindrical section. The end hemispheres of the Titan were both Titanium, but the center cylinder was a hoop wound graphite / epoxy composite. This means that the fibers (in the form of unidirectional tape from what I understand) mostly went around the circumference of the cylinder with a few plies laid down in along the axis of the cylinder to hold it all together. The pic attached here shows a couple of views of this design. In this pic you see that there are two end caps, which are made out of Titanium, and a center cylindrical section made of carbon fiber / epoxy. It is this center section that imploded at the depth that the Titan reached, probably fairly close to the Titanic.

So, was it the fact that the center section was made from carbon fiber / epoxy that the Titan imploded at depth? Or was it something else? These questions will of course be answered as soon as the Canadian and US investigators pore over all of the operations of OceanGate and the construction, maintenance, and inspection records of the Titan submersible. However, we have a few clues that have popped up fairly recently, which is what I want to talk about for a little bit here, and is the reason for the title of this post.

I have posted articles about failure in Composites before, like “How Stuff Breaks” and “How to Keep it from Breaking”. In those articles I talk a little bit about delamination between layers of composite and what drives that delamination. As it turns out, in an externally pressurized cylinder that is fairly thick (the Titan Composite section was 5” thick), the strains on the interior layers are different than the strains on the outer layers. This means that there is a shear stress between the layers in the pressure hull. And this shear stress has to be taken up by the glue that is holding the layers together – the epoxy resin itself. The problem with this is that epoxy is not all that strong in shear and tends to fail in a brittle manner rather than a ductile manner. In other words, it doesn’t just yield a little bit, it breaks instead.

What has to happen then, is that after every dive, the entire composite part of the pressure hull needs to be inspected and undergo a complete ultrasonic and radiographic inspection, looking for delaminations or matrix cracking. If the Titan had actually gone through class certification with ABS or DNV, or even Lloyds Register, OceanGate would have had to do this inspection after every dive. They did not.

So, what happened to the Titan. Well, I have it on good authority that the Quality Engineer brought this to the attention of the CEO of OceanGate, and was fired for doing so. He has a lawsuit pending for wrongful termination, but that had not made it to the courts yet. I’m sure that the Canadian and US investigators are questioning this guy right now.

So, what is Ned’s prediction for what the investigators are going to come up with? It is my opinion that the composite portion of the pressure hull had developed a delamination or several delaminations that together were large enough to cause the instantaneous collapse of the carbon fiber portion of the pressure hull.

That is why this post is titled “When Hubris Overtakes Reason – People DIE!” Because that is exactly what I am sure happened. So, the hubris of the CEO of OceanGate in first not getting the vehicle classed by a certification agency for operation at the depth of the Titanic, and also for neglecting the most important thing that he could have done to ensure safety of himself and his passengers, inspect the composite hull thoroughly after every dive. It he had just done one or two inspections over the course of the several dives that the Titan had made, it is entirely possible that he would have found the delaminations and had time to fix them before going down and losing his life and the life of all of his passengers.

Hubris overtaking Reason is the cause of the tragic loss of the Titan submersible.

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Jun 27, 2023
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Ned, an excellent article for sure. I recently contacted NAFEMS to say that the computer simulation industry may have to have a good look at itself over this. More comments below but good on yer.

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