'Banging' noises and less than 24 hours left: How the search for the missing submarine is unfolding.

Rescuers are racing against the clock to find the submersible which disappeared on the way to the Titanic wreck, with less than 24 hours of breathable air left on board.

The vessel, which is carrying five passengers, began its journey towards the wreckage site off Canada's coast on Sunday morning, before contact was lost about one hour and 45 minutes into its dive, the US coast guard said. 

The six-metre submersible, named Titan, has the capacity to stay underwater for 96 hours, according to its specifications - giving the five people aboard until early on Thursday before air runs out.

Rescuers are now concentrating their efforts on a remote area of the North Atlantic where a series of undersea noises have been detected.

On Wednesday, the US Coast Guard wrote on Twitter that a Canadian aircraft had detected the "underwater noises" in the search area. 

Canadian P-3 aircraft detected underwater noises in the search area. As a result, ROV operations were relocated in an attempt to explore the origin of the noises. Those ROV searches have yielded negative results but continue. 1/2

— USCGNortheast (@USCGNortheast) June 21, 2023

The statement came after Rolling Stone, citing what it described as internal US Department of Homeland Security emails on the search, said that teams heard "banging sounds in the area every 30 minutes."

In underwater disasters, a crew unable to communicate with the surface relies on banging on their submersible's hull to be detected by sonar. However, no official has publicly suggested that's the case and noises underwater can come from a variety of sources.

Remotely operated vehicle (ROV) searches were later deployed in the area where the noises were recorded.

However, US coast guard captain Jamie Frederick said at a press conference that analysis of the noises has been "inconclusive".

"We don't know what they are, to be frank with you," he said.

"We're searching in the area where the noises were detected."

As of now, these are the completed searches for the Titan, a 21-foot submersible from the Polar Prince, as of Wednesday afternoon.#Titanic pic.twitter.com/alpYBFA8kQ

— USCGNortheast (@USCGNortheast) June 21, 2023

On Monday, OceanGate Expeditions, which operates the submersible, said they were "mobilising all options" to rescue those on the vessel. 

"Our entire focus is on the crewmembers in the submersible and their families," they said in a statement on social media. 

Here's everything we know about the missing submersible.

The five people onboard the sub.

British billionaire Hamish Harding.

Image: Twitter. 

58-year-old British billionaire Hamish Harding was the first to be identified as one of the passengers onboard.

In a now-deleted Facebook post, Harding's stepson, Brian Szasz, said he had "gone missing on [a] submarine" and asked for "thoughts and prayers". 

Harding and his wife, Linda, share two sons, Rory and Giles. He also has a stepdaughter named Lauren.

Over the weekend, Harding posted on Facebook that he would be aboard the sub.

"Due to the worst winter in Newfoundland in 40 years, this mission is likely to be the first and only manned mission to the Titanic in 2023," he wrote. 

"A weather window has just opened up and we are going to attempt a dive tomorrow."

There have been no posts from Harding since.

The 58-year-old is the chairman of aircraft firm Action Aviation and is a renowned adventurer who has flown to space.

He is also a holder of three Guinness World Records for the longest duration at full ocean depth by a crewed vessel, the longest distance traversed at full ocean depth by a crewed vessel and the fastest circumnavigation via both poles by aeroplane.

Two of these feats were achieved by Harding and ocean explorer Victor Vescovo when they dived to the lowest depth of the Mariana Trench – the deepest part of the ocean – in a two-person deep-submergence vehicle in March 2021.

In June last year, Harding travelled to space with fellow billionaire Jeff Bezos' Blue Origin company. 

He was also part of a team that achieved the fastest circumnavigation of earth via both geographic poles by plane with a time of 46 hours, 40 minutes and 22 seconds, in 2019.

Paul-Henri Nargeolet aka 'Mr Titanic'.

Image: Mike Coppola/Getty/Mamamia.

77-year-old Paul-Henry Nargeolet is a former French Navy diver and the director of underwater research at a company that owns the rights to the Titanic wreck. 

Nicknamed 'Mr Titanic', he has been studying the ship for 35 years and was part of the first expedition to visit the wreck in 1987, just two years after it was discovered. 

Father and son Shahzada and Suleman Dawood.

Shahzada Dawood. Image: Facebook.

Shahzada Dawood is the vice-chair of Pakistani conglomerate Engro Corporation, a large fertiliser firm.

The 48-year-old is travelling with his 19-year-old son, Suleman, on the submersible.

According to the BBC, Suleman has been described as a "big fan of science fiction literature and learning new things", in a family statement.

Stockton Rush. 

Image: OceanGate.

Stockton Rush is the CEO and founder of OceanGate. 

According to the company website, the 61-year-old oversees "OceanGate’s financial and engineering strategies and provides a clear vision for development of 4,000-metre- (13,123ft) and 6,000-metre-capable crewed submersibles".

Last year, he defended the price of the expedition, which costs $US250,000 ($A365,100) per person, telling The New York Times it is a "fraction of the cost of going to space and it's very expensive for us to get these ships and go out there".  

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The challenging rescue effort. 

Rescuers face significant obstacles both in finding the Titan and in saving the people aboard. 

According to OceanGate's website, the expedition starts in St John's, a city on Newfoundland island off Canada's coast, before heading out approximately 640km into the Atlantic to the wreckage site. 

It takes about two hours to descend approximately 3,800 metres to the Titanic, which infamously sunk on its maiden voyage in 1912, killing more than 1500 people.

If the submersible experienced an emergency mid-dive, the pilot would likely have released weights to float back to the surface, according to Alistair Greig, a professor of marine engineering at University College London.

But without communication, locating a van-sized submersible in the vast Atlantic Ocean could prove challenging, he said.

The submersible is sealed with bolts from the outside, which means the occupants cannot escape without assistance even if it surfaces.

If the Titan is on the ocean floor, a rescue effort would be even more challenging due to the extreme conditions below the surface.

The Titanic lies 3810 metres underwater, where light does not penetrate. Only specialised equipment can reach those depths without getting crushed by the massive water pressure.

"It's really a bit like being an astronaut going into space," said Titanic expert Tim Matlin, as per AAP. 

"I think if it's on the seabed, there are so few submarines that are capable of going that deep. And so, therefore, I think it was going to be almost impossible to effect a sub-to-sub rescue."

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A post shared by OceanGate, Inc. (@oceangate)

David Pogue, a CBS reporter, dove to the site on board the Titan last year.

In a December news report, he read aloud the waiver he had to sign, which noted the submersible had "not been approved or certified by any regulatory body" and could result in death.

In an interview on Tuesday, Pogue said the OceanGate has successfully gone down to the wreck about two dozen times and that the company does a meticulous safety check before each attempt.

"They treat this thing like a space launch," he said, according to AAP. 

"It is definitely a culture of safety."

- With PA and AAP. 

This article was originally published on June 20, 2023, and was updated on June 22, 2023. 

Feature Image: AAP/OceanGate/Facebook/Getty/Twitter.

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