Tuesday, June 20, 2023

Titanium as a pressure hull? My $00.02 on the loss of the Oceangate Titan

I'm no expert on submarines and know next to nothing on metallurgy - but I do know enough that a red flag is raised in my head as I read reports about the Oceangate submersible, Titan.

The Titan commenced a dive early Sunday morning and maintained contact with its support ship for the first 1h 45m of the dive.

Since then, nothing.

Just about all of the available media now available is focusing on the results and procedures of the search. My interest is in the submersible itself...how does it dive, how does it surface and what redundancies are in place?

When I learned of the hull material - carbon-fiber and titanium - I immediately recalled a conversation that took place onboard another submarine during a mid-watch somewhere beneath the Pacific Ocean.

This was in the 1980's and the Soviets had just commissioned an Alfa-class submarine. Our engineering officer, a Naval Academy-degreed nuclear chemist, was commenting on the operational cost of using titanium as a pressure hull, as was the case with the Alfas.

The benefit to titanium is that those submarines were impervious to detection techniques that relied on a magnetic signature. Unlike US steel-hulled submarines, titanium is non-ferrous.

But also unlike steel, titanium is brittle and does not flex. Furthermore, it is weakened by repeatedly being stressed.

What this meant for the Soviet submarines is that their maximum depth had to be de-rated each time the submarine went to that maximum depth.

The Oceangate Titan claims to have a maximum depth of 4000 meters. The wreckage of the Titanic is at 3810 meters. The Titan has made over 200 dives, including several to near its max depth beginning in 2019 and yet its max depth appears to have never been de-rated.

As for the carbon-fiber component of the hull, this is an untested material for such use. Carbon-fiber can fail suddenly and catastrophically in other applications.

If a collapse of the hull is the cause for the loss of the Titan, SOSUS reports of the acoustics (if declassified) will confirm that in the coming weeks. The crew will have died instantly.

UPDATES (3 July 2023):







  1. A very interesting point, and one I hadn't seen discussed elsewhere. Carbon fiber composite is also a tricky material. It's great for keeping a structure's weight down, which is why it's used extensively in racing yachts, but it's quite brittle and can fail in insidious ways after even a minor impact.

    Of couse it might not have been a material failure at all, and we may never know what really happened.

  2. Watching them unloading the debris I noted that the nose of the submersible was being lifted with a strap through the viewport. The 1300 meter rated plexiglass window was missing. I doubt they removed it before analysis to facilitate lifting so I'm presuming it departed as part of the failure. Whether it blew in and caused the sinking, or out as the carbon fiber shell failed is the question.

    1. I have a lot of questions that I hope will be answered in the coming months:

      Who (by individual name(s), not company) designed the submersible and what were their credentials?
      What was the transition material from titanium to carbon-fiber and how were the differing compression rates of these three materials accounted for?
      By what basis was it rated to 4000m and was a time limit a part of that depth rating?
      Why was there no acoustic beacon onboard? These cost about $6000 (maybe that answers the question) and are commonly available for depths down to 6500m. One would have drastically shortened the search time.

      It's well known by now that Stockton Rush ignored a lot of safety protocols but the intrinsic design of the sub itself seems to have completely disregarded any suggestion of competent engineering.

  3. Also the carbon fiber was a 'left-over' outdated batch from the airlines and rejected for use in the air. What were they thinking? Mike C.