In July 2022, David Pogue, a correspondent, embarked on a nine-day sea voyage with Stockton Rush, the CEO of OceanGate and creator of the Titan submersible. Their purpose was to document a dive to the wreckage of the Titanic for “CBS Sunday Morning.” Following this, Pogue conducted additional interviews with Rush at OceanGate’s headquarters the next month.
Tragically, Rush and four others lost their lives in June 2023 due to a catastrophic implosion during a dive with the Titan. The conversations during their time together largely revolved around the factors that have since been scrutinized after the Titan disaster, including the carbon-fiber hull, the unique design, and Rush’s inclination to save costs and challenge conventions. The following excerpts from the interviews have been edited for brevity and clarity.
July 2022 Interviews
The Carbon-Fiber Shell
RUSH: The crucial aspect of our pressure vessel is that it is made of carbon fiber. Carbon fiber is an excellent material, superior to titanium and many others. However, it is possible to experience catastrophic failure due to imperfections in the structure that would not occur in a metal vessel. Therefore, it’s important to be mindful of how it is manufactured.
POGUE: If carbon fiber could lead to potential death with even a minor crack, why did you choose to use it instead of a heavier material?
RUSH: Because carbon fiber is three times stronger than titanium when it comes to strength-to-buoyancy ratio underwater. The focus is on strength-to-buoyancy, not weight. By using carbon fiber, the pressure vessel becomes lighter than the water it displaces. It is one of the best materials for constructing a submersible, as long as it is done correctly.
POGUE: So, if the entire submersible were made of titanium…
RUSH: It would weigh twice as much and require a significant amount of foam for buoyancy. If you look at other deep-diving subs like Alvin, Shinkai, or Jiaolong, they rely on foam with their spherical designs.
Sealing the Dome
POGUE: Would the submersible float if it were made entirely of titanium?
RUSH: No, in that case, I would have to add a substantial amount of foam. Those subs I mentioned earlier, like Jiaolong, have a large amount of foam for buoyancy.
POGUE: Has anyone else considered using carbon fiber for their submersibles looking at what you’ve achieved?
RUSH: No, to my knowledge, there aren’t many others pursuing this approach at the moment. However, I believe that eventually more people will explore the potential of carbon fiber.
RUSH: Our carbon fiber cylinder is a complex structure. We collaborated with Boeing and had a design contract with them. We experimented with various designs. They had previously created a deep-sea autonomous vehicle called the Deep Sea Glider that was designed to reach 6,000 meters. Our objective was to scale it up.
We carried out numerous tests, and when Boeing analyzed the hull, it required 24 hours on their supercomputer to complete the analysis. They examined every single fiber, which numbered in the millions, and how they responded. Constructing a dome from carbon fiber proved to be a greater challenge. Consequently, we used titanium for the domes, which have a thickness of three-and-a-quarter inches.
The tolerance for the domes is extremely precise, with a fluctuation of only 5,000th of an inch over a five-foot diameter. Maintaining this tight tolerance is crucial. A single O-ring is used to maintain pressure at shallow depths.
One limitation of carbon fiber is that it cannot have holes cut into it. Therefore, we pass cables through the titanium to allow data transfer. This is how we access and operate instruments within the submersible.
POGUE: So, nothing makes direct contact with the carbon fiber part—no pipes, wires, cables, or tubes?
RUSH: That’s correct. The carbon fiber remains untouched.
The Hull-Monitor System
POGUE: How many backup systems are in place to prevent the collapse of the submersible?
RUSH: Our key safeguard is an acoustic monitoring system. Carbon fiber produces sound, as there are millions of fibers in the structure. In this five-inch section, there are 667 layers of thin carbon fiber. When the submersible is pressurized for the first time, some fibers, which are comparatively weaker, may snap and produce cracking noises. When we reach a certain depth, say, 1,000 meters, it will generate considerable noise. However, once we reduce the pressure, it ceases until the maximum depth is surpassed again.
We have eight acoustic sensors that listen for these sounds. If we hear crackling at 1,000 meters, we immediately investigate whether there has been any unexpected impact or cyclic fatigue on the submersible. This system provides ample warning. During testing, we have intentionally destroyed several structures, and there is a significant amount of warning before implosion occurs, up to 1,500 meters.
POGUE: So, if you heard the carbon fiber making popping sounds…
RUSH: If I hear the carbon fiber going pop, pop, pop, the gauge indicates multiple events.
POGUE: Would you have enough time to ascend to the surface, which is about three hours away?
RUSH: Yes, because once you halt the descent, it becomes easier due to reduced pressure. You just need to stop going down. We extensively tested this, determining the warning signs. As I mentioned, there is approximately 1,500 meters of pressure difference between the point where we realize the hull is not stable and when it implodes. This gives us plenty of time to release weights, ascend to the surface, and assess the situation.
POGUE: What else is there to be concerned about?
RUSH: The things people often overlook, such as being on a ship in the open ocean. I worry more about potential injuries like falls, head traumas, broken bones, and collarbones. Being on a boat poses significant risks.
POGUE: Do you consider the boat more dangerous than the submersible?
RUSH: Yes, once you are sealed inside the submersible, equipped with four days’ worth of life support, it becomes the safest place on Earth. Even if a catastrophic event occurs outside, such as a nuclear bomb destroying the ship, we would still have four days to survive. It’s like being in the world’s safest container. As long as we manage carbon dioxide levels and supply oxygen, we would be fine for a considerable period.
Scrubbing Carbon Dioxide
POGUE: Speaking of managing carbon dioxide, what if the system fails?
RUSH: We have two systems in place. One is a process called Sodasorb, which utilizes calcium hydroxide. This system is commonly used in hyperbaric chambers to remove carbon dioxide. In the event of a failure, which could occur due to a battery issue, we have lithium-hydroxide blankets that can scrub carbon dioxide from the ambient environment. Additionally, we carry an ample supply of oxygen, enough for four days.
Overall, Rush’s insights shed light on the considerations and safeguards implemented in designing the Titan submersible and highlight the unique properties of carbon fiber that make it a favorable choice for constructing such vessels.
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