Titanic: What is the 'submersible' that has disappeared near the Titanic wreck? How long can people survive on the Titan?

The submersible has enough oxygen to last until Friday

It is described by some people as a “tourist submersible”, but in practice, generally attracts people with experience of sub sea adventures – or similar activity.

The OceanGate website says its expeditions, which cost upwards of $250,000 (£195,000), typically involve one pilot, a “content expert” and three paying passengers. US authorities have said the five people on board include one pilot and four “mission specialists”.

It is believed the occupants of the vessel Titan include adventurer and chairman of Action Aviation, Hamish Harding, Pakistani businessman Shahzada Dawood and his son Sulaiman Dawood and Titanic expert and explorer Paul-Henri (PH) Nargeolet.

Equipment and boats fill the docks at the the US Coast Guard Station Boston in Boston, Massachusetts. A submersible vessel used to take tourists to see the wreckage of the Titanic in the North Atlantic has gone missing, triggering a search-and-rescue operation, the US Coast Guard said.

Stockton Rush, chief executive of OceanGate, the company that operates the vessel, is also believed to be on board.

What is the vessel Titan and what was the mission?

The OceanGate submersible has been operating since 2021, according to the company’s website.

Made of carbon fibre and titanium and measuring 6.7m long, it is constructed to withstand the intense pressure beneath the sea and weighs 10,432kg. The submersible can reach depths of just over 13,000 feet.

It attempts a small number of missions a year, many of which have to be abandoned due to weather and other conditions.

This group lost contact with a surface team one hour and 45 minutes into the trip, which aimed to reach the wreck of Titanic, which lies 435 miles south of St John's, Newfoundland, Canada.

OceanGate’s website says it has made successful expeditions to the wreck in 2021 and 2022, and would continue to return annually to “further document the Titanic and its rate of decay”.

However, like other subs used to access the Titanic wreck – such as that used by film director James Cameron, who created the film based on the story of the iconic ship – the technology is surprisingly basic.

A video filmed by the BBC and featuring OceanGate chief executive Mr Rush shows how it is controlled using a video game controller akin to that on a PlayStation.

"It’s got one button, that’s it,” he said, explaining how “if you want to go forward, you press forward”.

A journalist who took part in an OceanGate expedition last year said the vessel “seemed improvised”. “I couldn't help noticing how many pieces of this sub seemed improvised, with off-the-shelf components,” said David Pogue, a CBS News Sunday correspondent.

“These submersibles are one-offs. They are sometimes jerry rigged. The lights he bought from camperworld.com – something like that. ”All of them are like this.”

He said there were seven ballasts on board – some which he described as made from “abandoned construction pipes” - that the submersible could jettison to float to the top of the sea, making it possible to locate where the vessel was if it was in trouble.

“Either they are bobbing on the surface and have no power,” he said. “Or something happened that overrode all seven of those ballasts.”

Mr Pogue added: “Or the really horrible possibility is the capsule developed a leak, and they'd be dead in a fraction of a second.”

How long can people survive on the vessel?

Coast Guard officials estimated on Monday afternoon the vessel had “somewhere between 70 to the full 96 hours” of oxygen. This could give rescuers until Friday to locate and retrieve the submersible. However, experts have warned if those on board began to panic and move around, they could end up using up more oxygen faster.

Issues such as low temperatures – if the submersible has lost power and sunk to the ocean floor – could also be a major problem for those inside the capsule. The atmosphere pressures will be about 380 times more than would normally be felt.

Another man, Mike Reiss, an American writer, took a trip on the submersible last year.

He said: "You sign a massive waiver that lists one way after another that you could die on the trip. They mention death three times on page one, so it's never far from your mind."

"As I was getting onto the sub, my thought was ‘this could be the end’. So nobody who's in this situation was caught off guard. You all know what you are getting into.”

It has been reported the waiver states: “This experimental vessel has not been approved or certified by any regulatory body, and could result in physical injury, emotional trauma, or death.”

How difficult is a rescue?

The US Coast Guard has sent two C-130 Hercules aircraft to search on the surface of the water, along with a Canadian C-130, and a P8 aircraft equipped with underwater sonar capability. Sonar buoys are also being deployed in the area.

However, if the vessel is under water – potentially on the ocean floor – the nuclear-powered submarines used by the US Navy are unlikely to be able to reach it, as they usually operate at 800 feet or less. They are not able to dive down to the ocean floor, where water pressure on the submarine hull could cause it to implode.

The Navy does have specialised rescue submersibles, but even those can only make rescues at depths up to 2,000 feet, according to the Navy’s Underwater Rescue Command.

If any rescue can take place, it would be 11,000 feet deeper than the deepest ever successful undersea rescue, which took place when Roger Mallinson and Roger Chapman’s submersible Pisces III became trapped 1,575 feet under the sea off the coast of Ireland in 1973 after a faulty hatch broke.

Experienced submariners, Mr Mallinson and Mr Chapman employed various methods to conserve carbon dioxide and survive on scant supplies. Other submersibles were flown to Cork from off Aberdeen, Canada and California and managed to bring the vessel to the surface, where the two men were rescued unharmed.