OceanGate’s CEO and founder Stockton Rush had a problem. He wanted to take passengers to see the Titanic shipwreck. They would pay an enormous amount of money ($250,000/person) for the opportunity. But the wreck lay on the ocean floor almost 4,000 meters below the surface and his passenger-carrying submersible could only go to a depth of 500 meters. The pressure at 4,000 would crush the Cyclops faster than a beer can at a frat party.
A video from WABASH using a tanker trailer, a shell with stiffener rings, which shows the speed and suddenness of an implosion. The severity at the depths the Titan was at would have caused a much greater pressure differential, but its walls were thicker than the tanker trailer’s. Also, the behavior of carbon fiber in an implosion is far different than it is for metal and it is uncertain whether the collapsed carbon fiber hull would have stayed in one piece. Video: YouTube.
But the swashbuckling Rush, a former commercial pilot with an aerospace engineering degree, had a solution: a thick wall cylinder held together with carbon fiber composite. Why not? Carbon fiber had worked for the Boeing 787 Dreamliner.
Never mind that every deep ocean submersible before it had shied away from carbon fiber for behavior in compression that is problematic and unpredictable. Some had been quite outspoken about using the material. Rush prided himself on breaking rules.
The task of designing the carbon fiber-enforced hull, now under scrutiny as a likely cause of the submersible’s failure, initially fell to Spencer Composites located in Sacramento, California, led by Brian Spencer. Spencer, with his multiple engineering degrees, including a PhD from the University of Nebraska in engineering mechanics and publications galore, was an expert on filament winding, a technique he had already applied to many a land-based and aerospace product—and most important to this story—for Steve Fossett’s DeepFlight Challenger, so named because it appeared to be more like an airplane than a submersible.
[Ed note: The carbon fiber-enforced hull of the ill-fated mission was made by Electroimpact, located north of Seattle, Washington.]
Millionaire adventurer Steve Fossett, who was the first to fly a hot-air balloon around the world and the first to fly around the world without refueling, was already a legend. He planned to add to his achievements by going to the bottom of the Mariana Trench, the deepest known point in the ocean, past 19,500 meters.
Fossett was given the task of designing a carbon fiber hull for the DeepFlight Challenger. Spencer had analyzed it using COSMOS/M, by Structural Research and Analysis Corp (now incorporated into Dassault Systèmes and branded SOLIDWORKS Simulation). He had built it on a 4-axis CNC machine adapted for filament winding.
The result, a simple-looking thick-walled cylindrical pressure chamber (with the pressure on the outside, of course) in which Fossett was to lie hid a carefully placed network of carbon fibers, each placed precisely either tangentially or axially to the cylinder. Spencer’s composite design for the hull involved alternate double layers of wound carbon fiber around a core (acting against the compressive hoop stress) and a layer of fibers laid axially (against the compressive axial stress that would develop from the pressure on the hemispherical endcaps, according to a 2010 CompositesWorld.
|
2010 |
2017 |
2023 |
|
DeepFlight Challenger |
OceanGate’s Cyclops 1 |
OceanGate’s Titan (Cyclops 2) |
|
Steve Fossett |
Stockton Rush |
Stockton Rush |
|
19,500 meters |
500 meters |
4,000 meters |
|
1 person |
5-6 people |
5-6 people |
|
1.5 factor of safety |
2.25 factor of safety |
2.25 factor of safety |
|
6-inch-thick wall |
5-inch-thick wall |
5-inch-thick wall |
|
|
1.676-meter outside diameter |
1.676-meter outside diameter |
However, Fossett died in a 2009 light aircraft accident and never got to use the DeepFlight Challenger. The DeepFlight Challenger was then sold.
Similarities to the carbon fiber composite in this video of the Titan’s initial hull are similar to what was described in the design of Fossett’s DeepFlight Challenger: 2 layers of wound carbon fiber for each layer of axially oriented fiber. The hull on the Titan when it imploded was created by Electroimpact. Video: OceanGate via YouTube.
Because Spencer Composites was contracted a few years later by OceanGate to design the hull of the Cyclops 2 (renamed the Titan), we will assume the same wound and axial fiber composite design was used in OceanGate’s carbon fiber hulls1. A big difference, and perhaps a fatal one, is the DeepFlight Challenger needed to accommodate only one person, so it would have had less surface area, and therefore less compressive forces due to pressure, even though was designed to go to depths 5x deeper than the Titan.
Never mind that the DeepFlight Challenger’s use of a carbon fiber hull was unproven. Spencer had to use the same carbon fiber construction it had suggested for the DeepFlight Challenger for OceanGate’s submersibles. And the clock was ticking. Spencer was given 6 weeks and told he had to meet a few design constraints—a length of 2.54 m, 1.676 m outside diameter, service pressure of 6,600 psi (roughly the pressure at 4,000 meters), and a safety factor of 2.25, according to a 2017 article in CompositeWorld.
Spencer Composites’ first design of the OceanGate submersible used carbon fiber for all the structure, the hemispherical endcaps as well as the cylindrical body, according to an interview with Rush found on the University of Washington’s website. The Applied Physics Laboratory at the University of Washington, Seattle, near OceanGate’s headquarters (which Rush referred to as OceanGate’s “engineering partner”) ran pressure tests on a scale model of the Titan with carbon fiber cylinder and was at the time considering making all of the Titan’s main structure out of carbon fiber, including the hemispheric domes. However, the carbon fiber domes failed, letting water through at 3,000 meters. This probably led to the titanium domes that were actually used in the Titan.
Next: Simulation Reveals Exactly How Titan Submersible Imploded
Correction
July 21,2023. Added possibility that Titan's hull was made by another company, not Spencer Composites.
August 4, 2023. Named Electroimpact as the company that made the hull on the Titan that imploded.
Endnotes
1. There are reports (Reference 3) as well as a comment below that "during 2020 and 2021, the Titan’s hull was either repaired or rebuilt by two Washington state companies, Electroimpact and Janicki Industries" and possibly used different materials (higher strength) and possibly changed the laminate schedule but neither company has confirmed this by the time of this writing.
References
- “Composite Submersibles: Under Pressure in Deep, Deep Waters,” Jeff Sloan, CompositesWorld, May 10, 2017.
- “Deepsea Submersible Incorporates Composite Pressure Capsule,” Sara Black, CompositesWorld, August 31, 2010.
- A Whistleblower Raised Safety Concerns About OceanGate's Submersible in 2018. Then he Was Fired, Mark Harris, Tech Crunch, June 20, 2023