Titan Sub May Have Imploded Due to 'Micro-Buckling'

"Micro-buckling" in the hull of the Titan submersible may have caused it to collapse under pressure last summer, scientists have proposed.

OceanGate's Titan submersible went missing with five people on board on June 18, 2023, during an expedition to explore the wreck of the Titanic, found 13,000 feet down at the bottom of the Atlantic Ocean some 370 miles off the coast of Newfoundland, Canada.

Initially, the submersible—made of carbon fiber and titanium—was feared to have lost power or been otherwise unable to return to the surface, triggering mass search-and-rescue efforts over the subsequent days.

But it turned out the vessel had imploded mere hours into the trip, instantly killing everyone on board.

In a new paper in the journal Proceedings of the National Academy of Sciences (PNAS), researchers from the University of Houston studied how thin-walled structures can buckle as a result of tiny imperfections in their materials.

The Titan is a good example of such a structure. In a statement, research lead and professor of civil and environmental engineering Roberto Ballarini suggested that imperfections in the carbon fiber used to construct Titan's hull, compounded by any damage accrued during the vessel's previous dives, could have left it vulnerable to micro-buckling and, ultimately, the craft's collapse.

Thin-walled structures like that of Titan—or a car, or plane—can withstand large amounts of pressure, but are still vulnerable to collapse.

A perfectly shaped cylinder should theoretically be quite hardy, but any imperfections in manufacture can mean that the structure buckles at smaller forces than expected.

"[Titan's] integrity may have been compromised by the damage to the material used for its hull that accumulated during the many trips it took prior to collapse," Ballarini said in the statement.

"The material used for the Titan's hull was a carbon fiber composite. It is well known that under compression loading the fibers in such composites are susceptible to micro-buckling and that they may delaminate from the matrix that surrounds them.

"If the Titan's hull experienced such damage under the extreme compressive pressures it experienced during its dives, then its stiffness and strength would have significantly decreased, and together with the inevitable geometric imperfections introduced during its manufacturing, may have contributed to its buckling-induced implosion."

Using computer simulations, the researchers have predicted the average buckling strength of a shell with imperfections.

"We derived equations that allow us to predict the resistance to buckling of structures in terms of the parameters that are involved including the shapes and distribution of their imperfections," Ballarini said.

"Given the parameters that describe the imperfections, the equations we constructed using the results of the simulations 'spit out' the average buckling resistance of the structures.

"One must not forget that a structure's resistance to buckling failure is also affected by the strength and stiffness of the material from which it is made."

These simulations may reveal why the Titan submersible buckled when and where it did.

The buckling may have begun at the point of most severe imperfections, but since geometric imperfections are often randomly distributed around a shell like the Titan, the location of initial buckling may also be random.

"This randomness has profound implications for the statistics of the critical buckling pressure of the shell," said Ballarini.

OceanGate boss and Titan pilot Stockton Rush, 61, French Titanic expert Paul-Henri Nargeolet, 77, British billionaire Hamish Harding, 58, and Pakistani businessman Shahzada Dawood, 48, and his son, Sulaiman Dawood, 19, all died in the disaster.

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Update: 02/05/2024 7:44 a.m. ET: This article was updated with additional information.

Correction: 03/05/2024 7:59 a.m. ET: This article was updated to reflect the fact that the PNAS paper explored the buckling of thin-walled structures generally, and not the case of the Titan specifically.