US authorities say a debris field located in the North Atlantic leads to a conclusion that OceanGate's Titan submersible suffered a "catastrophic implosion" (a violent collapse inwards), instantly killing all five passengers on board.

The US navy says it detected sounds "consistent with an implosion" shortly after the sub lost contact on Sunday during a descent to the Titanic wreck at 3,800m below sea level – but this information was only made public on Thursday, June 22, 2023.

The loss of the deep-water vessel was finally confirmed after a huge search mission in the area off Canada's Newfoundland island.

What caused the implosion?

Titan's hull is believed to have collapsed as a result of enormous water pressure. 

The sub was built to withstand such pressure – and experts will now be trying to determine what exactly went wrong. Analysis of the debris may help to establish this.

Titan is believed to have been 3,500m below sea level when contact was lost.

The vessel was so deep that the amount of water on it would have been equivalent to the weight of the Eiffel Tower, tens of thousands of tonnes.

If there were a rupture to the structure, the pressure outside would be much greater than the one inside the hull, compressing the vessel.

What happens in an implosion?

When a submarine hull collapses, it moves inward at about 2,414km/h – that's 671m per second, says Dave Corley, a former US nuclear submarine officer.

The time required for complete collapse is about one millisecond, or one thousandth of a second.

A human brain responds instinctively to a stimulus at about 25 milliseconds, says Corley. Human rational response – from sensing to acting – is believed to be at best 150 milliseconds.

The air inside a sub has a fairly high concentration of hydrocarbon vapours.

When the hull collapses, the air auto-ignites and an explosion follows the initial rapid implosion, says Corley.

Human bodies incinerate and are turned to ash and dust instantly. 

How the investigation is likely to proceed

Any investigation is sure to focus on the carbon fibre mid-section of the Titan sub.

The pressure vessels of deep vehicles like this are normally constructed from a robust metal such as titanium and are shaped in a sphere, to spread the immense pressure equally around the passenger compartment.

But to fit more people inside, the OceanGate sub adopted a cylindrical shape, with a carbon fibre tube inserted between to titanium end caps. Carbon fibre is very tough - they use it to build aeroplane wings and racing cars.

But did that immense pressure at depth – more than 300 times the atmosphere at the sea surface – play on the material to expose flaws in the original fabrication or to introduce and then worsen instabilities over repeated dives?

Any investigation would want to know about the practice non-destructive testing.

Aircraft are subjected to regular, very fine-scale inspections to ensure their materials are not developing cracks or that their layers are not starting to separate.

Photographing the Titan debris found on the ocean floor and bringing them back to the surface for study in a forensic lab may allow engineers to identify where on the sub structural integrity was lost, initiating the catastrophic implosion.

Rear Admiral John Mauger of the US First Coast Guard District says investigators would attempt to find out what had happened to Titan: “I know there are also a lot of questions about how, why and when did this happen. Those are questions we will collect as much information as we can about now,” he says, adding that it was a “complex case” that happened in a remote part of the ocean and involved people from several different countries. 

 

The US navy has said it had detected an “anomaly” likely to have been the fatal implosion of the Titan, while the film director James Cameron says his deep-sea exploration sources have detected a “loud bang” that could have marked the moment when those on board lost their lives.

The navy analysed its acoustic data after the submersible was first reported lost on its voyage to the wreck site on Sunday morning (June 18). According to The New York Times, the data came from a secret network of underwater sensors designed to track hostile submarines.

It found an anomaly “consistent with an implosion or explosion in the general vicinity of where the Titan submersible was operating when communications were lost”, according to a statement. The navy, which did not consider the information to be definitive, passed it on to the coastguard as it continued its search for the missing men.

Cameron – who has made 33 dives himself to the Titanic wreck and claims to have spent “more time on the ship than the captain did back in the day” – said he had known the submersible was lost from the start of the four-day search. He also said his sources had reported similar information about the Titan’s fate.

“We got confirmation within an hour that there had been a loud bang at the same time that the sub comms were lost,” the director told Reuters. “A loud bang on the hydrophone. Loss of transponder. Loss of comms. I knew what happened. The sub imploded.”

Cameron became a deep-sea explorer in the 1990s while researching and making his Oscar-winning blockbuster Titanic, and is part owner of Triton Submarines, which makes submersibles for research and tourism.

He said he told colleagues in an email on Monday (June 19): “We’ve lost some friends,” and: “it’s on the bottom in pieces right now.” 

After the deaths of those onboard the Titan were announced, Cameron said he wished he had sounded the alarm earlier, adding that he had been sceptical when he heard OceanGate was making a deep-sea submersible with a composite carbon fibre and titanium hull.

“I thought it was a horrible idea. I wish I’d spoken up, but I assumed somebody was smarter than me, you know, because I never experimented with that technology, but it just sounded bad on its face,” Cameron told Reuters.

The cause of the Titan’s implosion has not been determined, but Cameron said he presumed the critics were correct in warning that a carbon fibre and titanium hull would enable delamination and microscopic water ingress, leading to progressive failure over time.

Other experts in the industry and a whistle-blowing employee raised alarms in 2018, criticising OceanGate for opting against seeking certification and operating as an experimental vessel. 

In 2019, OceanGate said it was concerned the certification process could slow down development and act as a drag on innovation. “Bringing an outside entity up to speed on every innovation before it is put into real-world testing is anathema to rapid innovation,” it said.

Earlier on Thursday, Cameron appeared on ABC News and said that many people in the submersible sector had been concerned by Titan.

“A number of the top players in the deep submergence engineering community even wrote letters to the company, saying that what they were doing was too experimental to carry passengers and that it needed to be certified and so on,” he said.

“We celebrate innovation, right? But you shouldn’t be using an experimental vehicle for paying passengers that aren’t themselves deep ocean engineers,” he added.

However, Stockton Rush’s former business partner, Guillermo Söhnlein, pushed back at such claims, insisting that the pair had put safety first when they co-founded OceanGate.

“[Rush] was extremely committed to safety,” Söhnlein told Britain’s Times Radio. “He was also extremely diligent about managing risks, and was very keenly aware of the dangers of operating in a deep ocean environment. So that’s one of the main reasons I agreed to go into business with him in 2009.”

Söhnlein said it was too soon to say what happened to the Titan, adding that it was “tricky to navigate” to formulate global regulations for submersibles designed to go ultra deep.

Cameron, meanwhile, drew parallels between the loss of the Titanic and the Titan, claiming both tragedies were preceded by unheeded warnings. In the Titanic’s case, the captain sped across the Atlantic on a moonless night despite being told about icebergs.

“Here we are again,” Cameron said. “And at the same place. Now there’s one wreck lying next to the other wreck for the same damn reason.”

Engineering experts weigh in 

1) Dr Jasper Graham-Jones, associate professor in mechanical and marine engineering at Plymouth University

“It is very sad that these crew and adventurers have lost their lives. The US coastguard detailed the wreckage was found 1,600ft from Titanic’s bow in five pieces. These include critical forward and rear sections of the sub's pressure bulkhead.

"Normally, such craft pressures’ bulkhead are round like a ball as it provides the strongest shape. To increase passenger numbers, the composite craft was extended. This increases loads in mid sections above normally seen in the rounded end. Imagine an eggshell, that can withstand high loads but is very brittle if bent. Extending the cabin pressure longitudinal bulkhead puts increased fatigue and delamination loads.

"Fatigue is where you can bend a wire backward and forward and then break under a lower load. Delamination is like splitting wood down the grain of a log, easier to do than chopping across the grain. The debris field of multiple small parts show the catastrophic and rapid failure of the sub which has imploded extremely quickly.

'Basic standard engineering taught to all engineering students'

“This craft has lasted 25 runs down to the Titanic and back to the surface. Each return run would put cracks in the pressure bulkheads. This might be small and undetectable to start but soon become critical and produce rapid and uncontrollable growth. The loading and critical crack size is basic standard engineering taught to all engineering students.

“Composite structures, like carbon fibre, or glass fibre are very good in reducing these fatigue cracks. It is this reason why most modern aircraft wings and helicopter blades are made of composite structures.   

“Has there been regular non-destructive testing and evaluations of any surface or subsurface cracks? Was that done by an independent qualified staff?

“Engineering is complex, and not everybody can know everything. We need to check our calculations, assumptions, and implement engineering best practice. Throughout all industries class association is there to give this very helpful technical information. (From Wikipedia: 'A ship classification society or ship classification organisation is a non-governmental organisation that establishes and maintains technical standards for the construction and operation of ships and offshore structures. Classification societies certify that the construction of a vessel comply with relevant standards and carry out regular surveys in service to ensure continuing compliance with the standards.') 

“In July 2022, Dr Dawn Wright and Caladan Oceanic completed a scientific expedition to Challenger Deep at the southern end of Mariana Trench – the deepest place on Earth, using a crewed deep-submergence vehicle called Limiting Factor. This was commercially certified by Det Norske Veritas Norway (DNV) for dives to full ocean depth, and is operated by a pilot, with facilities for an observer.

Marine classification

“Currently, more than 50 organisations describe their activities as including marine classification. Why did OceanGate submersible not do the same as every other deep-sea craft and use the services of marine classification to confirm it was safe for paying passengers?

"In international water, where the Titanic sank, there are no rules that require such regulations. If, as an individual, you want to put yourself down in unsuitable craft, that is your risk. However, this should be very different when it comes to paying passengers, and no legal waivers that you might sign can remove legal responsibility and duty of care.”

“I hope the design is fully examined by various classification organisations so that lessons can be learnt, and freely published. Carbon composites are excellent materials but have limited life when subject to excessive loads or poor design which leads to stress concentrations.

Non-destructive testing of composites

"These stress concentrations mean a normal functioning parts failure sooner and under lower loads then previously seen. This could be measured but required experts in non-destructive testing (NDT) of composites. In the same manner used by aircraft and helicopter manufacturers.

“Failure investigations start by collecting all available parts. This I have done on many occasions. Critical making sure you try and collect carefully so that no further damage is caused to collected parts. Also, a log of parts and locations from the largest to the smallest. These locations will spread from the surface through the water column to the sea floor.

"From visual and magnified views, components’ crack paths can be recorded. Typically, a map of all these crack paths this can be fixed to a few initial locations. From these initial locations possible failure causes can be suggested.   

“This might require scanning electron microscopes and X-ray detection, to analyse material compositions and crack growth rates and directions. This is likely to take six months plus as there are many interested in the results, both personally, and for legal redress. 

“Critical are the composite hull. The rear cover and landing frame could separate from the carbon fibre hull. If the debris include past of the carbon fibre hull this this is likely to be an implosion failure, that could have been by delamination fatigue failure.”

2) Prof Roderick A Smith, FREng, Imperial College London

“It looks likely that the issue is a failure of the pressure hull. As much debris as possible needs to be brought to the surface for close examination. The site of the rupture needs to be identified 

"The body consists of a carbon fibre cylinder end capped by titanium hemispheres. Carbon fibre fails by delamination or from internal defects in its construction.

"The joints between the carbon fibre and the titanium need very careful inspection. It is also possible that the bolted-down sealing device which allowed entry has failed. The violence of the implosion means that it may be very difficult to determine the sequence of events. Hence the need for retrieval and painstaking examination if possible.”

(Reuters; AP; Agence France-Presse; BBC; The Guardian; and Science Media Centre all contributed to this article.)