What happens to a submarine when it implodes?

SHAH ALAM - In a tragedy that seems worthy of a movie plot, a group of affluent explorers went on what would later be the last adventures of their lives.

The pilot and four passengers of the Titan submersible had vanished during a mission to explore the Titanic wreckage, and days of desperate searching for the vessel were launched after it lost contact with a surface vessel on Sunday, as search crews hoped it was simply stuck.

However, things took a turn for the worse after the United States Coast Guard confirmed on Thursday that debris found 1,600 feet from the bow of the Titanic belonged to the missing vessel.

Expeditions company OceanGate announced that those onboard, British billionaire explorer Hamish Harding, UK citizens Shahzada Dawood and his 19-year-old son Suleman Dawood, French national Paul-Henri Nargeolet and OceanGate Expeditions chief executive Stockton Rush had "sadly been lost".

The US Coast Guard offered its "deepest condolences" to the families after the tail cone of the vessel was found around 1,600ft from the bow of the Titanic wreck.

It was reported that the debris is evidence that the submersible likely suffered a catastrophic implosion during its descent to the Titanic on Sunday.

Submersibles are designed to withstand crushing underwater pressures, like those 12,500 feet below the surface. Down there, the pressure is about 400 times greater than at sea level.

It is said that any damage or defect to the hull of the vehicle could result in a leak which would trigger the vessel to immediately implode under those extreme pressures.

In a press conference earlier, Rear Admiral John Mauger, of the First Coast Guard District, did not confirm when the vehicle became irreparably damaged but said the sonar buoys deployed by teams would have picked up an implosion.

"This was a catastrophic implosion of the vessel which would have generated a significant broadband sound down there that the sonar buoys would have picked up," he was reported as saying.

According to Naval History Magazine, the implosion would have pulled the metal vessel apart "like taffy." "Complete destruction would occur in 1/20th of a second, too fast to be cognitively recognized by the men within the submarine." An implosion is basically the exact opposite of an explosion.

Instead of pressure from within moving outward, you have pressure from outside rushing in. Similar to an explosion, there is unlikely to be much left of the vessel and its cargo.

"I know it's no great comfort to the families and the spouses, but they did die instantaneously. They were not even aware that anything was wrong," journalist David Pogue said on CNN.

According to National World, "an implosion could occur if any part of the submersible's carbon fibre and titanium hull has suffered a small crack or fault." The implosion itself looks like a bubble created by the water's weight.

"If the pressure vessel has failed catastrophically, it's like a small bomb going off. The potential is that all the safety devices might be destroyed in the process," Stefan Williams, a professor of marine robotics at the University of Sydney told The Guardian.

Dr David Gallo, a senior adviser with RMS Titanic Inc, the company that owns the rights to the original underwater gravesite, said the timeline suggests something happened "mid-water" that caused them to lose power or radio communications.

However, with news of the debris and a likely implosion, the passengers probably did not suffer for long. "If that's what happened that's what would have happened four days ago," Guillermo Söhnlein, one of the founders of OceanGate, told BBC.

Moreover, the implosion would have been almost instantaneous, lasting only milliseconds, according to the Journal of Physics: Conference Series. Something similar happened in 1961 to the USS Thresher, a submarine, which is thought to have imploded.

If a submarine implodes, it means that it collapses inward on itself as a result of the water's high pressure, according to HITC.

The event would be catastrophic to those on board, and no one would be able to survive.

Officials are still unsure of the timeline of when exactly the vessel imploded into the dive; there have been various speculations that it may have happened right away and could be why the sub never resurfaced.

Or, it may have happened after they lost communication.

A video of a train imploding has also been racking up views on Twitter, with many saying this is the best explanation for what happened to the millionaires on board the Titan submersible.

The video depicts a train tank vacuum implosion at 1 atmospheric pressure. The depth at Titan is around 375 atmospheres.

It basically shows the vessel crumpling in on itself.

Former Navy submarine operator Mark Barry told a local news outlet it was likely the submersible had some deficiencies in the structure of its hull.

"Simply put, water weighs a lot more than air; for example, 33 feet of water depth overhead is equal to the entire weight of the atmosphere above each of us every day.

"At 12,500 feet, that pressure is almost 400 times greater across the boundary of, say, the submersible. Even the slightest defect in that boundary can allow a pathway for that pressure to rush in. When it does, it does so in the blink of an eye. Thankfully, a human wouldn't even feel it; it would happen so fast that no amount of suffering would occur. The deconstruction of this incident will reveal exactly what failed, but we just need time," he had said.