Rescuers embark on race to save the Titanic sub crew

While coast guard officials remain ‘hopeful’, only a handful hours are left before ozygen supply for the five on board runs out.

Underwater search equipment flown in by US Air Force planes is loaded on to the Horizon Arctic in the port of St Johns, Newfoundland, in Canada. Picture: Reuters

A massive search and rescue effort for a missing submersible near the wreck of the Titanic was at a critical stage on Thursday, with just hours left before the ­oxygen supply for the five people on board runs out.

While coast guard officials remained “hopeful,” with a surge of assets and experts joining the operation and sonar picking up unidentified underwater noises, the challenge of locating and recovering the crew alive appeared increasingly formidable.

“Sometimes you’re in a position where you have to make a tough decision. We’re not there yet,” said US Coast Guard captain Jamie Frederick, adding that it remained a search-and-rescue mission “100 per cent”.

Organisers of the multinational response – which includes US and Canadian military planes, coast guard ships and teleguided robots – are focusing their efforts in the North Atlantic close to multiple “underwater noises” detected by sonar late on Tuesday and on Wednesday.

The sounds raised hopes that passengers on the small tourist craft were alive, though experts have not been able to confirm their source. “We don’t know what they are, to be frank with you,” Captain Frederick said.

“We have to remain optimistic and hopeful.”

Titan began its descent at 8am on Sunday and had been due to resurface seven hours later, according to the US Coast Guard.

Rescuers, who have received help from around the world, estimate the passengers may run out of oxygen just after 9pm on Thursday AEST, based on the sub’s capacity to hold up to 96 hours of emergency air.

The ship Deep Energy joins the search for the Titan. Picture: US Coast Guard via AFP

The 6.5m tourist craft lost communication with its mothership less than two hours into its trip to see the remains of the ­Titanic, which sit nearly 4km below the North Atlantic.

The submersible, named Titan, was carrying British billionaire Hamish Harding, Pakistani tycoon Shahzada Dawood and his son Suleman, who also have British citizenship.

OceanGate Expeditions charges $US250,000 for a seat on the submersible.

Also on board is the company’s CEO, Stockton Rush, and French submarine operator Paul-Henri Nargeolet, known as “Mr Titanic” for his frequent dives at the site.

Ships and planes have scoured some 20,000sq km of surface water looking for the vessel, which was trying to dive about 650km off the coast of Newfoundland, Canada.

After noises were detected by a Canadian P-3 aircraft, rescuers relocated two remotely operated vehicles that search under the water and one surface vessel with sonar capability. The ROV searches have not yielded results but data from the Canadian aircraft has been shared with US Navy experts for acoustics analysis. “There have been multiple reports of noises and every one of those noises is being analysed,” said Carl Hartsfield, from the Woods Hole Oceanographic Institution.

He said the sounds “have been described as banging noises.”

Captain Frederick said the number of surface vessels in the search would double from five to 10 within 24 to 48 hours.

The US Navy has sent a specialised winch system for lifting heavy objects from extreme depths, other equipment and personnel; the Pentagon has deployed three C-130 aircraft and three C-17s. A deep-sea underwater robot sent by France’s oceanographic institute was to arrive on Thursday. A Canadian ship carrying medical personnel and a decompression chamber was also en route.

The pressure at that depth as measured in atmospheres is 400 times what it is at sea level.

Mike Reiss, an American television writer who visited the ­Titanic wreck on the same sub last year, told the BBC the experience was disorientating.

Alistair Greig, professor of marine engineering at University College London, has suggested two possible scenarios based on images of the Titan.

He said if it had an electrical or communications problem, it could have surfaced and remained floating, “waiting to be found” – bearing in mind the vessel can reportedly be unlocked from the outside only.

“Another scenario is the pressure hull was compromised – a leak,” he said. “Then the prognosis is not good.”

In 2018, OceanGate Expeditions’ former director of marine operations David Lochridge alleged in a lawsuit that he had been fired after raising concerns about the company’s “experimental and untested design” of the craft.

AFP