Experts have shared why the Titan submarine may have imploded – including a new theory about how it was towed behind its ‘mothership’ to the Titanic site.
Stockton Rush, CEO of OceanGate, who died along with four fare-paying passengers from his company in the June 18 disaster, reinvented Titan’s unique design, which he hoped would become a new industry standard.
But several moves aimed at cutting costs and making marine exploration more profitable could also have had disastrous results, engineering experts told The New York Times in an article published on Friday.
By comparing the Titan to the Alvin, a US government research submersible that has safely completed more than 4,500 deep-sea dives since 1973, the experts point to a number of design and protocol changes that may have doomed the Titan.
Unlike the Titan, the Alvin was designed as a sphere with an all-titanium hull that was transported to the dive site on the deck of a mother ship, while the Titan was towed across the rough waters of the North Atlantic on her small dive platform, potentially damaging the shabby ship was damaged before imploding, killing five people.
The Polar Prince is seen towing the Titan submersible aboard its launch pad. Experts say a number of cost-cutting measures may have contributed to the sub’s catastrophic implosion
Stockton Rush, CEO of OceanGate, who died along with four fare-paying passengers from his company in the June 18 disaster, re-engineered Titan’s unique design to reduce costs
The Titan, owned and operated by OceanGate Expeditions, began ferrying passengers to Titanic in 2021 for up to $250,000 per passenger per trip.
It was touted for a roomier carbon fiber cylindrical cabin – a departure from the spherical titanium cabins used on most submersibles.
The Titan submersible lost communications with its support ship on June 18 while descending to the wreck of the Titanic about 12,500 feet below the surface.
Days later, the wreckage was recovered from the seabed and investigators believe the submarine was crushed under the tremendous pressure of the deep sea.
In addition to Rush, four others died: British adventurer Hamish Harding, 58; Pakistani tycoon Shahzada Dawood, 48, and his son Suleman Dawood, 19, French Titanic expert Paul-Henry Nargeolet, 77.
Before the Titan, submersibles, including the Alvin, had a strong track record of safety. Submersibles differ from submarines in that they must be launched from a mother ship at sea.
Theories as to what led to the disaster include…
The Titan was towed across rough seas and not kept safely on deck
The Alvin research submarine is transported to dive sites on the deck of a custom mothership equipped with custom winches and a large crane that lowers it into the sea.
In contrast, the Titan had no mother ship of her own and was towed out to sea on the fatal dive by a smaller charter ship, the Polar Prince, to save money.
Polar Prince, a decommissioned Canadian Coast Guard icebreaker, was smaller and older than the ships OceanGate had operated in previous years, which Rush used as a cost-cutting measure.
Using a tow cable, the ship towed the Titan across hundreds of miles of open sea on the launch platform used to immerse and retrieve the submarine.
When asked if there was a risk of damage if Titan was towed, a company spokesman told the Times, “OceanGate is unable to provide any further information at this time.”
The Alvin research submarine is transported to dive sites on the deck of a custom mothership equipped with custom winches and a large crane that lowers it into the sea
In contrast, the Titan (above) did not have its own mother ship and was towed out to sea by a chartered ship, the Polar Prince, to save money
The Titan is seen being towed to a dive site. In May there was a “near-disaster” between the submarine and the platform and they were partially sunk in the open sea, a witness reported
Arnie Weissmann, the editor-in-chief of Travel Weekly, took an OceanGate trip in May on the same Polar Prince mothership that towed the submarine some 435 miles from St. John’s, Newfoundland, to the Titanic base.
“I thought the sub and the platform were being thrown around pretty roughly,” Weissmann told the Times.
Although he spent a week aboard Polar Prince waiting for clearer weather, the dive was eventually abandoned and Weissmann was never able to descend with Titan.
In a column for Travel Weekly, Weissman told the harrowing story of a “near-disaster for the submarine and the platform” on the high seas.
“At the end of the rope connecting the stern of the ship to the platform, we saw that the front of the platform and the submarine were submerged,” he wrote.
It was not clear what happened, but crew members suspected that a fishing buoy spotted in the area may have tangled a line in the platform and pulled it under the platform, causing the air tanks to fill with water.
Attempts to raise the platform using a buoy on the towline were unsuccessful, and Rush had to send out divers to clear the water from the platform’s bouncy tanks, which took half a day.
Fishing line was found to have become tangled in the platform, leaving the cause of the incident shrouded in mystery.
Weissman recalled that when asked if the incident endangered the submarine, Rush joked, ‘So a submarine is submerged.’ Why is that a problem?’
Pill-shaped design instead of the tried and tested spherical shape, which better withstands pressure
Alvin, the United States Navy’s famous research submersible and operated by the Woods Hole Oceanographic Institution, has a spherical design.
In the depths of the ocean, a sphere is the optimal shape to withstand crushing pressures, which can reach three tons per square inch, because the pressure is evenly distributed throughout the hull.
The downside of the Alvin is its limited capacity – the submarine can only take three people to the bottom of the sea.
Rush, which charged $250,000 per passenger for its dives to the Titanic wreck, could have carried just two customers per trip with a similar design if an OceanGate pilot had come along.
Instead, its titanium design was more spacious, seating five people in a pill-shaped submarine constructed from a carbon fiber tube capped at both ends with titanium hemispheres.
Alvin, the United States Navy’s famous research submersible, has a spherical titanium hull for passengers, as shown in the schematic above on the left
Alvin has safely completed more than 4,500 deep sea dives since 1973. Above is the staff sphere with space for three people in the other support apparatus
Titan’s design was more spacious, seating five people in a pill-shaped submarine constructed from a carbon fiber tube capped with titanium hemispheres at both ends
Tim Foecke, a retired forensic metallurgist, told the Times that changing the Titan’s hull geometry — from a narrow sphere to a long tube — may have contributed to the submarine’s catastrophic failure.
He found that the larger a submarine, the stronger and thicker its hull must be to withstand the same pressure.
Given two submarines with the same hull thickness, the larger one would “collapse or buckle” first, he said.
CARBON FIBER HULL MORE SENSITIVE TO COMPRESSION
One of Rush’s key innovations with the Titan was the use of carbon fiber for much of the fuselage, which is cheaper and lighter than titanium.
On its website, OceanGate advertised the Titan’s carbon fiber construction with titanium end caps as “lighter weight and more efficient mobilization than other deep-water submersibles”.
The material reduced Titan’s weight to 21,000 pounds, compared to Alvin’s 45,000 pounds.
However, experts say that carbon composites are much more resistant to tensile forces than compressive forces.
One of Rush’s key innovations with the Titan was the use of carbon fiber for much of the fuselage, which is cheaper and lighter than titanium
OceanGate boss Stockton Rush can be seen in the Titan’s carbon tube hull
The tube was five inches thick and made of several layers of carbon fiber
“I was very surprised” by the fiber construction of the Titan, Foecke told the Times, because compression was the main force the submersible encountered during its deep-sea dives.
Carbon composites also have a finite lifespan when subjected to excessive stress or poor design, leading to stress concentrations, said Jasper Graham-Jones, associate professor of mechanical engineering and shipbuilding at the University of Plymouth in the UK.
“Yes, composites are extremely strong. Yes, composites are extremely durable. But we have issues with composites and the fact that composites fail in slightly different ways than other materials,” he told the Associated Press.
In addition, Titan’s 5-inch thick hull had been subjected to repeated stresses over the course of about two dozen previous dives, Graham-Jones said.
Tiny cracks would appear in the structure with every ride. “It might be small and unobtrusive at first, but soon it would become critical and lead to rapid and uncontrollable growth,” he said.
The use of different materials increases the risk of the joints wearing out more quickly
The Titan’s design required the attachment of its carbon fiber tube to the Titan end caps, which was accomplished with strong glue.
But experts say maintaining a seal between them can be a challenge, as different materials deform at different rates under pressure.
Alfred S. McLaren, a retired Navy submariner and president emeritus of the Explorers Club of New York City, explained that the various materials in the Titan’s hull “have different coefficients of expansion and compression, which works against maintaining a watertight connection.”
In other words, if the carbon fiber tube was compressed a little differently than the titanium end caps, it could have compromised the seal between them, especially after repeated dives.
This image shows a titanium ring connecting to the Titan’s carbon tube hull. Because different materials change shape at different rates under pressure, maintaining a seal between them can be challenging
Debris from the Titan submersible, recovered from the seabed near the Titanic wreckage, is unloaded from the vessel Horizon Arctic at the Canadian Coast Guard pier
The launch platform used for the Titan submarine is towed back to shore at St. John’s Harbor in Newfoundland, Canada, after the submarine was wrecked
Experts have also questioned OceanGate’s refusal to use external testing and certification for the Titan.
Graham-Jones said it is standard engineering practice to seek outside expertise to ensure ships meet the highest industry standards.
In a 2019 company blog post, OceanGate criticized the third-party certification process as time-consuming and inhibiting innovation.
“Keeping an outside company in the loop about any innovation before it’s put into practice is anathema to rapid innovation,” the post says.