ONE tiny fault with the Titan sub could have led to the "catastrophic" implosion that crushed five crew on board, an expert has revealed.
Investigators are facing the grim task of trying to piece together what went wrong with the doomed OceanGate vessel.
OceanGate said "true explorers" Stockton Rush, Brit billionaire Hamish Harding, Paul-Henri Nargeolet, Shahzada Dawood and his 19-year-old son Suleman tragically died on the dive to the Titanic wreck.
A deep-sea robot sub found five major pieces of debris of Titan two miles beneath the surface on Thursday.
Rear Admiral John Mauger, of the US Coast Guard, said the debris was 1,600ft from the bow of the Titanic - and "consistent with a catastrophic loss of the pressure chamber".
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The debris - including a landing frame and the tail cone - must now be raised 3,800m from the sea floor to uncover how the sub met its violent end.
Experts said one tiny flaw in the 21ft vessel could have led to disaster.
Maritime historian Dr Sal Mercogliano, from North Carolina Campbell University, said the "unforgiving" ocean only needed to find a single "weak point" in the construction of the sub.
"Unfortunately, at that depth where you have pressure, that’s 380 times what you have at the earth’s surface," he said.
"That little deformity, that flaw, will lead to catastrophic results."
And the strength of the hull under lots of pressure changes was not fully understood, Dr Mercogliano explained.
The bolts and attachments can "fray" at the edges - and there's also glue involved.
"The glue is important because the titanium caps are glued to the carbon fibre hull’s ends," Dr Mercogliano told news.com.au.
"The repeated stress of pressure and temperature should require constant inspection.
"I don’t know what OceanGate did after each dive with Titan."
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Dr Mercogliano said the shape of the sub could have also posed a potential problem.
The Titan was a simple carbon fibre tube with titanium end caps holding it together - and with no escape pod.
“This is what makes this vessel so unique,” says Dr Mercogliano.
“When you look at most submersibles that operate in that depth, they’re a sphere.
"They’re this round object because pressure acts uniformly on a sphere."
But pressure is unevenly distributed on a cylinder, he explained, meaning it would have been under immense strain.
The pressure where the debris was discovered is around 6,000 PSI - compared to 14.7 at sea level.
Dr David Gallo, a deep sea expert and friend of Paul-Henri Nargeolet, believes something happened as the sub was descending to the ocean floor.
"If they weren’t there (at the wreck), that means something had to happen mid-water that caused them to lose power or radio communications," he told Sky News.
The repeated stress of pressure and temperature should require constant inspection
Dr Sal Mercogliano
He also suggested a pressure hull failure was the most likely explanation.
"There’s no coming back from that. I would have to say that has got to be the number one option here – which is unpleasant to think about," he said.
Chairman of the US-based Manned Underwater Vehicles Committee, William Kohnen, said something "clearly disturbed the pressure hull".
"If you've ever held a balloon and it just pops, if you just hold it lightly... something happened," he told BBC Radio 4's Today programme.
"An implosion is just a reverse explosion, so it exploded inwards."
He said: "Anyone who operates in that depth of the ocean... knows the risks of operating under such pressure and that at any given moment, on any mission, with any vessel, you run the risk of this kind of implosion."
Rear Admiral Mauger, from the US Coast Guard, admitted the bodies of the five crew may never be recovered - describing the sea floor as an "incredibly unforgiving, incredibly complex environment".
"We will continue to work and search the area down there but I don’t have an answer for prospects at this time," he added.
He said the implosion would have made a "significant, broadband sound that the sonar buoys would have picked up".
And it would have killed the crew instantly, he added.
Dr Dale Molé, the former director of undersea medicine and radiation health for the US Navy, revealed what would have happened during the crew's tragic final moments.
Molé told the Daily Mail: "It would have been so sudden, that they wouldn't even have known that there was a problem, or what happened to them.
"It's like being here one minute, and then the switch is turned off. You're alive one millisecond, and the next millisecond you're dead."
He compared the implosion to the popping of a balloon when it has been blown up too much.
"They would have been ripped to shreds," Dr Molé explained.
"An implosion is when the wave of pressure is inward, whereas an explosion is when the pressure wave or the shock wave goes out from whatever the source of that is.
"When somebody stands on an empty soda can, it would support your weight, but then if you press on the sides, the can would collapse immediately."
Expert Ofer Ketter said the implosion would have occurred within a millisecond - meaning those on board "never knew it happened".
On Thursday, a US defence official revealed that the US navy heard "an acoustic anomaly consistent with an implosion" just hours after the sub lost contact on Sunday.
A top secret military system designed to spot enemy submarines detected the sound of the suspected implosion, Wall Street Journal reports.
The official said the information was given to the US Coast Guard team - who then apparently used it to narrow the search area.
Sounds of banging detected underwater on Wednesday had raised hopes of a last-gasp miracle - but experts now believe it was just the noises of other ships in the area.
If they weren’t there (at the wreck), that means something had to happen mid-water that caused them to lose power or radio communications
Dr David Gallo
Titanic film director James Cameron, who has completed 33 dives to the wreck, claimed he knew on Monday there had been an implosion - days before the debris was found.
Mr Cameron told CNN he received "confirmation that there was some kind of loud noise consistent with an implosion event" from his colleagues in "the deep submergence community".
He told BBC News: "I felt in my bones what had happened.
"For the sub's electronics to fail and its communication system to fail, and its tracking transponder to fail simultaneously - sub's gone."
The sub's owner OceanGate confirmed the five crew were dead in a statement on Thursday afternoon.
The vessel vanished less than two hours into its descent to the Titanic wreckage on Sunday.
Search crews had been frantically looking for the vessel in the Atlantic after it lost communication on Sunday with just 96 hours of life support.
The sub failed to resurface later that afternoon - with its final "ping" to mothership Polar Prince placing the sub directly above the ruins.
OceanGate has come under fire after it emerged that crucial safety blunders were made before the dive to the Titanic wreck.
The company faced a lawsuit over fears about the sub’s safety - and a former passenger revealed the vessel also went missing last year.
Guillermo Söhnlein, a co-founder of OceanGate, has hit back at some of the criticism.
He told BBC Radio 4's Today programme: "People keep equating certification with safety and are ignoring the 14 years of development of the Titan sub.
"Any expert who weighs in on this... will also admit that they were not there for the design of the sub, for the engineering of the sub, for the building of the sub and certainly not for the rigorous test programme the sub went through."
He said anyone operating in the deep ocean "knows the risk of operating under such pressure and that at any given moment".
"You run the risk of this kind of implosion," Söhnlein said.
