French robot offers 'main hope' of finding missing Titanic sub

As hopes fade of finding survivors on the five-man Titan submersible, a French robot that can dive to 6,000 metres underwater has arrived over the Titanic wreck site to join the search.

This undated image shows the Titan submersible launching from a platform. Rescue teams are in a race against time to find a Titan deep-diving tourist submersible that went missing near the wreck of the Titanic with five people on board. AFP - HANDOUT

The unmanned robot, called Victor 6,000, can dive deeper than other equipment now at the site in the North Atlantic and has arms that can be remotely controlled to cut cables or perform other manoeuvres to release a stuck vessel, the operator said.

The robot, which is aboard the French oceanographic vessel L'Atalante, has a limited window to provide assistance now the missing submersible's air supply is expected to have run out.

"Victor is not capable of lifting the submarine up on its own," said Olivier Lefort, the head of naval operations at Ifremer, the state-run French ocean research institute which operates the robot.

But he told Reuters the robot could help hook the 10-tonne submersible called Titan to a ship with the capacity to lift it to the surface.

Four days missing

Titan went missing with five people on board shortly after starting its descent on Sunday to the Titanic, the British ocean liner that sank in 1912 after hitting an iceberg. The wreck lies at a depth of about 3,810 metres.

"Victor is able to do visual exploration with all the video equipment it has. It is also equipped with manipulating arms which could be used to extricate the sub, such as by sectioning cables or things that would be blocking it at the bottom," he said.

Ifremer was part of the team that located the wreck of the Titanic in 1985 with American underwater archaeologist Robert Ballard.

French explorer Paul-Henri Nargeolet, 77, who is reported to be among the five people inside the missing submersible, previously worked at Ifremer and piloted its flagship Nautile submarine that was used to examine the Titanic wreck.

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Ifremer sent the Atalante ship with its robot at the request of the US Navy. "This is the logic of seafarers. Our attitude was: We are close, we have to go," Lefort said.

The robot is operated by a 25-strong crew. "We can work non-stop for up to 72 hours, we don't need to stop at night," he said.

The US Coast Guard said Canadian aircraft equipped to find submarines had detected noises in the area. U.S. media reported that those sounds included banging at 30-minute intervals.

"We don't know what happened. The noises that were heard give us hope the submarine is on the seabed and that people are still alive, but other scenarios are possible," Lefort said. "Even if hope is slim, we'll go all the way."