Unusual design may have led to submarine tragedy

The cylindrical design and carbon fiber construction, unlike conventional submersibles, may make the Titan unable to withstand deep-sea pressure.

The cylindrical hull can cause uneven pressure distribution across the surface of the ship. Photo: AP

The crushing of the Titan submersible has raised questions about whether the Titanic exploration vehicle was destined for disaster due to its unusual design and the manufacturer’s refusal to conduct an industry-standard independent inspection. All five people aboard the Titan died when the vehicle was crushed near the world’s most famous shipwreck, Coast Guard Rear Adm. John Mauger confirmed on June 22. Authorities ended the search on June 18 after the Titan lost contact with its mother ship in the North Atlantic, according to the AP .

The Titan, owned and operated by OceanGate Expeditions, will first take people to the Titanic wreck in 2021. The ship is described as having a more spacious cylindrical cabin made of carbon fiber, as opposed to the spherical titanium cabins used by most submersibles. However, a sphere is the perfect shape because the water pressure is evenly distributed throughout, according to Chris Roman, a professor at the University of Rhode Island's Graduate School of Oceanography. Roman has not been on the Titan, but has made several deep dives with the Alvin, which is operated by the Woods Hole Oceanographic Institution in Massachusetts.

At 22 feet long and 24,000 pounds, the Titan's larger interior volume means it's still cramped for its maximum capacity of five people, but it's also more pressurized. The extended cabin space inside the submersible increases the compression forces in the middle, which reduces the strength of the material and increases the pressure on the laminate, said Jasper Graham-Jones, associate professor of mechanical and marine engineering at the University of Plymouth in England. In addition, the Titan's 5-inch-thick hull has been repeatedly stressed over dozens of previous dives. Each trip creates tiny cracks in the structure. "The cracks may start out small and hard to detect, but they quickly grow larger and get out of control," Graham-Jones said.

OceanGate advertises that the submersible’s carbon-fiber construction, with a titanium lid, is “lighter and more efficient at maneuvering than other deep-sea submersibles.” The company also claims the sub is designed to safely dive to 2.5 miles (4 kilometers). But carbon composites have limited lifespans when subjected to overloads or poor design that lead to stress buildup, Graham-Jones said.

OceanGate has also been warned that the failure to have a third-party inspect the vessel during its development could pose safety concerns. In a 2018 lawsuit, David Lochridge, OceanGate’s former director of marine operations, said the company’s inadequate inspection and licensing process could have potentially put passengers in danger on the experimental submersible. Lochridge called for “non-destructive testing” of the hull design, such as sonar scans, but the company refused.

Ultrasonic testing can help identify areas within a structure where composite materials are vulnerable to cracking, says Neal Couture, executive director of the American Society for Nondestructive Testing, a professional organization. “When a boat is submerged and pressurized, the composites are compromised. Nondestructive testing is a way to evaluate structures and determine whether they are still functional or vulnerable to failure,” Couture explains.

The Marine Technology Association, a group of marine engineers, technologists, policymakers, and educators, also raised concerns with OceanGate about the Titan’s size, construction materials, and lack of third-party testing of the prototype. Will Kohnen, the organization’s president, said the permitting process was flawed and threatened to have dire consequences for everyone in the industry. Graham-Jones said it was standard practice to seek expert advice to ensure the ship met the highest standards. In a 2019 post, OceanGate criticized the process as time-consuming and inflexible.

Titanic director James Cameron, who has dived to the wreck many times, said there were several possible reasons for the submersible's destruction, but the most likely was damage to the composite hull.

The Titan submersible is made from carbon fiber and titanium, according to OceanGate. Measuring 22 feet by 9 feet by 8 feet, the Titan is designed to carry a pilot and four passengers. It can travel at a top speed of 3,400 mph and dive to depths of 13,000 feet.

The ship has no dedicated steering system, but is controlled by a PlayStation controller. To communicate with the mothership, Titan sends messages via a sonar system (USBL).

The Titan submersible went missing on June 18 while carrying five people on a tour of the Titanic wreck at the bottom of the Atlantic Ocean, about 600 km off Newfoundland, Canada. According to the company's website, the underwater expedition to the Titanic wreck is being conducted by OceanGate from 2021, at a cost of $250,000 per person.