- A naval architect says rescuers likely have only one shot to save the missing sub if it's found.
- The submersible, which weighs 23,000 pounds, is likely on the ocean floor if it's still underwater.
It's one thing to find the missing Titanic submersible in the vast Atlantic Ocean — it's another herculean task to retrieve the vessel if it's stuck deep in the ocean.
The US and Canadian authorities are searching for a submersible that disappeared on Sunday while carrying five people to see the wreck of the Titanic, which rests at a depth of around 13,000 feet.
It's not immediately clear what happened to the submersible when it lost contact with its mother ship. It's possible the vessel later resurfaced, though its passengers would be dead-bolted inside. Or the vessel's hull may have been breached, in one of the worst-case scenarios that, at such extreme depths, would mean everyone on board has died.
But there's also the remote chance that the submersible, called the Titan, could still be somewhere deep beneath the surface level, intact, and with all five passengers alive.
Some hope exists on that front. On Tuesday evening, the US Coast Guard tweeted that a Canadian plane discovered "underwater noises" in the search area. Rolling Stone, citing internal US memos, reported that an aircraft had documented "banging" sounds at 30-minute intervals.
Experts have so far told various media outlets that if the vessel was still intact and deep underwater, the only available rescue option would be to tow it back to the surface.
Send a line down and hook it up — while 13,000 feet underwater
One way rescuers can pull this off is by using the "Flyaway Deep Ocean Salvage System," or FADOSS.
It's a lift system with a winch and cable designed to retrieve "large, bulky, and heavy sunken objects" weighing up to 60,000 pounds, according to the US Navy. The Titan weighs around 23,000 pounds, according to the company that operates the submersible.
Another US Navy remote system, the CURV-21, can reach depths of up to 20,000 feet, but with a maximum lift capacity of 4,000 pounds, it's unlikely to be able to retrieve the Titan. The US Navy said on Tuesday evening that it had sent a FADOSS to assist in the rescue effort.
Still, even with the FADOSS, rescuers would have to find a way to hook up the Titan submersible while it's thousands of feet underwater.
David Mearns, an ocean-recovery expert, told the BBC that a "world-class" remote-operated vehicle with two manipulators could potentially grab the submersible or attach a line to it.
US and Canadian authorities haven't said whether they have deployed a vehicle capable of performing such a feat on the ocean floor. Alistair Greig, a submarine expert from University College London, told the BBC that the Titan is probably either on the surface or the seabed and is "very unlikely" to be in between.
That means that if the submersible is still in the water, rescuers would likely have to send a vehicle and cable that could reach the wreck of the Titanic, which is around 2.5 miles under the surface.
A solution could come from France. The French government said on Tuesday that it's sending a ship, called the Atalante, to the search area with the Victor 6000 robot, which is capable of reaching depths of around 3.7 miles.
The robot is equipped with high-quality cameras and can "manipulate objects," according to France's Ifremer Institute.
Rescuers will "only get one chance"
Fotis Pagoulatos, a naval architect, told The Wall Street Journal that there might not be enough time to save the passengers inside even if they found the Titan deep below.
"You need a ship that can lower a cable to pull the Titan up or have some kind of a claw," Pagoulatos told the outlet. "Even if they find it, there may not be enough time for the rescue because of the oxygen issue inside."
Pagoulatos told the Journal that rescuers would essentially "only get one chance" at most.
The US Coast Guard says the Titan has enough emergency oxygen to last until Thursday afternoon ET because the submersible dives with around four days of life support.
David Marquet, a retired US Navy submarine captain, told NPR that such an elaborate deep-sea operation could be possible but said that the chances of the passengers' survival stood at "about 1%."
"I'm hopeful, but I think the families should prepare themselves for bad news," he told the outlet.