Missing Titanic sub: What is it like inside the vessel Titan, operated by OceanGate?
By Lily Ford, ITV News Multimedia Producer
The US coastguard is leading a huge search and rescue operation after a commercial submersible lost contact with those above ground during a voyage to the Titanic shipwreck.
Among those on board the vessel include British billionaire Hamish Harding and UK-based Pakistani businessman Shahzada Dawood.
Previous tourists on a trip in 2021 paid 100,000-150,000 dollars (£78,260-117,400) apiece to ride the 23,000lb craft, named Titan, operated by OceanGate Expeditions.
It is a vessel piloted by an Xbox controller, the company's CEO, who is on board the missing sub, Stockton Rush, revealed in a CBS News interview last year.
What is it like being on board the vessel?
A team of engineers at NASA’s Marshall Space Flight Center consulted with OceanGate’s engineers during Titan's development.
The sub is designed to carry five people, a pilot and four passengers, and its facilities are limited.
According to the OceanGate website, it is made of carbon fibre and titanium.
About the size of a mini-van, it measures 6.7 meters in length and is designed to reach depths of 2.5 miles (4 kilometers) - the Titanic sits on the seabed 2.4 miles down.
It's the only five-person submersible in the world, and even has a functioning toilet, though it's a tight space for one adult, let alone five, and the passengers are sealed in the cylindrical capsule from the outside.
A glimpse at the inside of the submersible
Similar to a plane or rocket, the air inside is breathable and recycled, and internal pressure remains constant.
At one end is a viewing portal 21 inches in diameter, which allows two passengers to look outside.
The onboard health analysis monitoring system is supposed to provide a early warning detection for the pilot with enough time to ascend and safely return to the surface.
How is it operated?
OceanGate describe Titan as "easy to operate".
Mr Rush has previously claimed the craft is extremely simple and has just one button.
"It should be like an elevator, it shouldn't take a lot of skill," Mr Rush told CBS News, before revealing it is designed to be piloted with just an Xbox controller.
"Everything else can fail... You're still going to be safe": CEO of OceanGate Stockton Rush discusses mission safety with CBS News last year
For its launch, it remains on a platform until it reaches about 30 feet below the water’s surface, where it starts its journey to the seabed.
To get back to the surface, it re-docks at the platform and ballast tanks are filled with air, bringing the craft and its passengers back to the surface.It can travel at a speed of three knots and descend at 55 meters per minute, with propulsion coming from four electric thrusters.
Titan's equipment includes external lights, cameras and a laser scanner.
How much air is left?
David Concannon, an adviser to OceanGate, said on Monday the submersible had a 96-hour oxygen supply, but a US Coast Guard official has now revealed it may have been reduced to just 70 hours.
The crew are more than 35 hours into their allotted oxygen supply.
Mr Concannon added officials are working to get a remotely operated vehicle that can reach a depth of six kilometers (3.7 miles) to the site as soon as possible.
What is Titan's history?
In May 2021, OceanGate said the Titan had an “unparalleled safety feature” that assesses the integrity of the hull throughout every dive.
At the time of the filing, Titan had undergone more than 50 test dives, including to the equivalent depth of the Titanic, in deep waters off the Bahamas and in a pressure chamber, the company said.
During its 2022 expedition, OceanGate reported that the submersible had a battery issue on its first dive and had to be manually attached to its lifting platform.
It is an eight-day expedition.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know...