Experts have shared why the Titan sub may have imploded – including a new theory about how it was dragged out to the Titanic site behind its ‘mothership’.
OceanGate CEO Stockton Rush, who was killed in the June 18 disaster alongside four of his company’s paying passengers, innovated the Titan’s unique design, which he hoped would become a new industry standard.
But several moves designed to slash costs and make sea exploration more profitable may have also come with disastrous consequences, engineering experts told the New York Times in an article published on Friday.
By comparing the Titan with the Alvin, a US government research submersible that has safely completed more than 4,500 deep sea dives since 1973, the experts point out 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, which was transported to the dive site on the deck of a mothership, while the Titan was towed across the rough waters of the North Atlantic on its small dive platform, potentially damaging the shoddy vessel before it imploded and killed five.
The Polar Prince is seen towing the Titan submersible aboard its launch platform. Experts say a number of cost-cutting measures could have contributed to the sub’s catastrophic implosion
OceanGate CEO Stockton Rush, who was killed in the June 18 disaster alongside four of his company’s paying passengers, innovated the Titan’s unique design to slash costs
The Titan, owned and operated by OceanGate Expeditions, first began taking people to the Titanic in 2021, at up to $250,000 per passenger per trip.
It was touted for a roomier cylinder-shaped cabin made of a carbon-fiber – a departure from the sphere-shaped titanium cabins used by most submersibles.
The Titan submersible lost communications with its support vessel on June 18, during a descent to the wreck of the Titanic roughly 12,500 feet beneath the surface.
Days later, its debris was recovered from the ocean floor, and investigators believe the sub was crushed under the immense 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 at sea from a mothership.
Among the theories on what led to the disaster are…
TITAN WAS DRAGGED ACROSS ROUGH SEAS – NOT KEPT SAFELY ON DECK
The Alvin research sub is transported to dive sites on the deck of a dedicated mothership, which is outfitted with custom winches and a large crane that places it in the ocean.
In contrast, Titan had no dedicated mothership, and to cut costs it was towed out to sea on the fatal dive by a smaller chartered vessel, the Polar Prince.
The Polar Prince, a decommissioned Canadian Coast Guard icebreaker, was smaller and older than the ships OceanGate had used in previous years, in a cost-cutting move by Rush.
Using a tow cable, the ship dragged the Titan across hundreds of miles of open sea on top of the launch platform that was used to submerge and retrieve the sub.
Asked if towing Titan risked damage, a company spokesman told the Times: ‘OceanGate is unable to provide any additional information at this time.’
The Alvin research sub is transported to dive sites on the deck of a dedicated mothership, which is outfitted with custom winches and a large crane that places it in the ocean
In contrast, Titan (above) had no dedicated mothership, and to cut costs it was towed out to sea by a chartered vessel, the Polar Prince
The Titan is seen being towed to a dive location. In May, the sub and platform met with ‘near-disaster’ and partially submerged on the open sea, one witness recounted
Arnie Weissmann, the editor in chief of Travel Weekly, took an OceanGate voyage in May, using the same Polar Prince mothership that towed the sub about 435 miles from St. John’s, Newfoundland, to the Titanic site.
‘I thought the sub and platform were being tossed around pretty roughly,’ Weissmann told the Times.
Though he spent a week aboard the Polar Prince waiting for weather to clear, the dive was ultimately called off and Weissmann never got to descend in the Titan.
In a column for Travel Weekly, Weissman recounted a harrowing tale of a ‘near-disaster for the sub and platform’ during high seas.
‘At the end of the rope that linked the stern of the ship to the platform, we saw that the front of the platform and the sub were under water,’ he wrote.
It was not clear what had happened, but crew members theorized that a fishing buoy spotted in the area may have gotten a line tangled with the platform and dragged it under, filling air tanks with water.
Attempts to lift the platform with a buoy on the tow line were unsuccessful, and Rush had to send divers out to clear water from the platform’s bouncy tanks, a process that took half a day.
The no fishing line was discovered tangled in the platform, leaving the cause of the incident a mystery.
Weissman recalled that, when asked about whether the incident jeopardized the sub, Rush joked: ‘So a sub is under water. Why is that a problem?’
PILL-SHAPE DESIGN INSTEAD OF TRIED-AND-TESTED SPHERICAL SHAPE THAT BETTER RESISTS PRESSURE
Alvin, the famous research submersible owned by the United States Navy and operated by the Woods Hole Oceanographic Institution, has a spherical design.
At the depths of the ocean deep, a sphere is the optimal shape to resist crushing pressures that can reach three tons per square inch, because the pressure is equally distributed across the hull.
The downside to the Alvin is its cramped capacity — the sub is only capable of taking three people to the ocean floor.
Rush, who was charging $250,000 per passenger for his dives to the Titanic wreckage, would have only been able to take two customers per trip with a similar design, assuming an OceanGate pilot went along.
Instead, his Titan design was roomier, with space for five people in a pill-shaped sub, which consisted of a carbon-fiber tube capped by titanium hemispheres on each end.
Alvin, the famous research submersible owned by the United States Navy, has a spherical titanium hull for passengers, as seen left in the above schematic
Alvin has safely completed more than 4,500 deep sea dives since 1973. Above, the personnel sphere with room for three can been seen housed inside the other support apparatus
Titan’s design was roomier, with space for five people in a pill-shaped sub, which consisted of a carbon-fiber tube capped by titanium hemispheres on each end
Tim Foecke, a retired forensic metallurgist, told the Times that the Titan’s change in hull geometry — from a tight sphere to a lengthy tube — may have contributed to the sub’s catastrophic failure.
He noted that the larger a sub is, the stronger and thicker its hull must be in order to withstand the same pressure.
In two subs with the same hull thickness, the larger one would ‘collapse or buckle’ first, he said.
CARBON-FIBER HULL THAT’S MORE VULNERABLE TO COMPRESSION
One of Rush’s main innovations in the Titan was the use of carbon fiber for much of the hull, which is cheaper and lighter than titanium.
OceanGate promoted the Titan’s carbon fiber construction – with titanium endcaps – as ‘lighter in weight and more efficient to mobilize than other deep diving submersibles’ on its website.
The material reduced Titan’s weight to 21,000 pounds, compared with Alvin’s 45,000 pounds.
But experts say carbon composites are much tougher against pulling forces than they are against crushing forces.
One of Rush’s main innovations in the Titan was the use of carbon fiber for much of the hull, which is cheaper and lighter than titanium
OceanGate boss Stockton Rush is seen inside the Titan’s carbon tube hull
The tube was five inches thick, and constructed by wrapping many layers of carbon fiber
‘I was very surprised’ by the fiber construction of Titan, Foecke told the Times, because compression was the main force that the submersible encountered on its deep sea dives.
Carbon composites also have limited life when subject to excessive loads or poor design which leads to stress concentrations, said Jasper Graham-Jones, an associate professor of mechanical and marine engineering at the University of Plymouth in the United Kingdom.
‘Yes, composites are extremely tough. Yes, composites are extremely long lasting. But we do have issues with composites and the fact that composites fail in slightly different ways than other materials,’ he told the Associated Press.
Furthermore, the Titan’s 5-inch thick hull had been subjected to repeated stress over the course of about two dozen previous dives, Graham-Jones said.
Each trip would put tiny cracks in the structure. ‘This might be small and undetectable to start but would soon become critical and produce rapid and uncontrollable growth,’ he said.
USE OF VARIOUS MATERIALS RAISED RISK OF JOINTS WEARING OUT MORE QUICKLY
The Titan’s design required attaching its carbon-fiber tube to the titanium endcaps, which was achieved with powerful glue.
But experts say that because different materials change shape at different rates under pressure, maintaining a seal between them can be challenging.
Alfred S. McLaren, a retired Navy submariner and president emeritus of the Explorers Club of New York City, explained that the different materials in the Titan’s hull ‘have different coefficients of expansion and compression, and that works against keeping a watertight bond.’
In other words, if the carbon fiber tube compressed in a slightly different way than the titanium end caps, it could have compromised the seal between them, particularly after repeated dives.
This image shows a titanum ring being bonded 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 ocean floor near the wreck of the Titanic, is unloaded from the ship Horizon Arctic at the Canadian Coast Guard pier
The launch platform used for the Titan submersible, is towed back to shore at the Port of St. John’s in Newfoundland, Canada after the sub was destroyed
Experts have also questioned OceanGate’s refusal to seek outside testing and certification for the Titan.
Graham-Jones said it’s standard procedure in engineering to seek outside expertise the ensure that vessels conform to the highest industry standards.
In a 2019 company blog post, OceanGate criticized the third-party certification process as one that is time-consuming and stifles innovation.
‘Bringing an outside entity up to speed on every innovation before it is put into real-world testing is anathema to rapid innovation,’ the post said.