The missing Titan submersible is unlikely to have suffered a catastrophic failure of its pressure hull, according to a deep-sea engineer who designed the vessel that film-maker James Cameron used to reach Earth’s deepest point.
Ron Allum, an Australian deep-sea engineer and explorer, co-designed the Deepsea Challenger submersible that Cameron used in 2012 to reach the deepest-known point of Earth’s seabed in the Mariana Trench.
Allum also worked with Cameron on his Last Mysteries of the Titanic documentary in 2005.
“Sound travels particularly well underwater,” Allum said. “A catastrophic implosion could be heard for thousands of miles and could be recorded.”
An implosion would likely trigger signals in military hydrophones, devices used for recording or listening to underwater sounds.
“To me, it sounds like the sub’s pressure hull is intact, but it’s demobilised from power,” Allum said. In such an event, the Titan was likely to have automatically dropped weights to resurface.
The tourist sub lost communications in the north Atlantic on Sunday while on a dive to the wreck of the Titanic. How long it would take to retrieve it if found depends on where and what state the vessel is in.
“If the pressure hull is flooded, you’re now talking about the dry mass of a vessel. You could be lifting a very heavy weight,” Allum said.
“If it were intact, an ROV [remotely operated vehicle] could attach to it and it could at least bring it up to shallower water where they could get a stronger lift cable to it to lift it out of the water … that ascent may take an hour or two.
“The ROV may have to work around the wreckage … it may take a few hours to release the sub from the seafloor.”
The submersible should have released its drop weights in an emergency but partial flooding of the pressure hull could be preventing the vessel from resurfacing, Allum said.
“If you have water in the pressure hull, it’s quite a large volume. The drop weights usually aren’t that big, and that could be what’s keeping it on the bottom.
“It also means that if the occupants are sitting in a half-flooded pressure hull, that could also be catastrophic. They could become hypothermic. I don’t know how well the CO2 scrubber systems would work if they’re wet.”
Dr Glenn Singleman, an Australian extreme medicine expert who has visited the Titanic shipwreck, said a lack of oxygen and carbon dioxide buildup were worrying concerns for the people onboard the missing submersible.
“You’ve got to control your oxygen flow and you’ve got to remove carbon dioxide and you’ve got to remove water vapour. They’re the three things about the environment internally that you’ve got to control. The fourth thing is temperature … the water temperature down there is 0 to 1C,” he said.
Singleman has been the expedition physician on several deep-sea exploration projects, including for Cameron’s Titanic documentary, the Deepsea Challenger expedition, and Victor Vescovo’s Five Deeps expedition.
To prevent carbon dioxide buildup, submersibles are equipped with “scrubbers”, usually made of soda lime, which remove CO2 from the air.
“The problem is that you get to a saturation point after a while, and you’ve got to change out the soda lime,” Singleman said. “CO2 content in air is about 400 parts per million. As it goes up, over 1,000[ppm], most people start to get symptomatic, and over 5,000, you’re very symptomatic – you get hyperventilation, you get a headache, you just feel awful.”
Singleman added that the oxygen being supplied inside the vessel was likely being delivered to maintain the regular atmospheric concentration of 21% oxygen.
A drop in oxygen levels in the air can result in hypoxia, in which bodily tissues become deprived of adequate supply. Oxygen concentrations of 10% and lower can result in loss of consciousness and death.
Singleman said the Titan’s initial 96-hour supply of oxygen would be a figure based on an average person’s oxygen consumption at an average metabolic rate.
“You’ve got no idea how people respond to the stress of a difficult situation – some people can increase their metabolic rate with stress, some people can relax and try to sleep and decrease it.”
Singleman described Paul-Henri Nargeolet, one of the five people on board, as a “legend” in the submersible community and “one of the leading experts” on the Titanic wreck.
“His passion is the Titanic, and he’s visited that wreck more than 100 times in submersibles … Everybody says: why would you go on such a risky venture? The reason is because it’s his passion. This is who he is. He’s spent a lifetime in submersibles going to these extreme environments, exploring unknown places and bringing back these incredible photographs and incredible stories of what’s possible.
“I’ve talked to PH many times about it. That’s worth the risk.”
