For an expedition as hazardous as the Titan’s descent to the Titanic, there is a long list of onboard systems that need to be checked and a host of environmental hazards that must be identified and assessed before the voyage begins.
“When you are putting people in a potentially dangerous position like this you want to be absolutely sure everything’s checked through before getting under way,” said Stefan Williams, a professor of marine robotics at the University of Sydney. “We have an extensive checklist before we put anything in the water.”
What checks were performed before the submersible and its five occupants slipped beneath the waves are unclear, but standard checks and procedures were followed, the Guardian understands. These would have been absolutely crucial given the crushing pressure generated at 3,800 metres below sea level – the depth of water the Titanic came to rest in – and the real potential of getting lost: the site is nearly 400 miles off the coast of Newfoundland.
Industry insiders said pre-dive preparations would, or should, have included checks on the submersible’s structure and all of the vessel’s mechanical and electrical systems. These aim to ensure all is fine before the descent begins: that the hull is sound, the batteries are charged, there are no short circuits or electrical faults, that the thrusters work, that radio and acoustic communications are functioning, and that the submersible can drop the weights it carries when the time comes to resurface.
Further checks are needed to reduce risks at the dive site. The Titanic itself is a hazardous structure that a submersible could become caught in, but lost trawler fishing nets and other drifting materials either at or near the site can also present a danger of entanglement. An expedition would typically plan to keep a safe distance from the wreckage, though strong undersea currents can make this a challenge. The problem with getting entangled is there is often little that can be done from inside a submersible to work the vessel free.
The Titan was expected to spend two hours descending to the Titanic, a few hours exploring the site, and two more resurfacing. As the vessel plunged deeper, a real-time hull health monitoring system would have reported the strain on the hull, a carbon fibre structure that connects two titanium composite domes.
Contact was lost with the Titan one hour and 45 minutes into the expedition. By that time, experts believe it reached a depth of about 3,500 metres, where each square inch of the structure would have been subjected to a force equivalent to more than two tonnes. While the vessel was designed to operate down to 4,000 metres, and would have had a safety margin to go deeper, industry experts said other deep-sea vessels used steel or titanium alone to ensure their hulls could take the pressure. Carbon fibre is widely regarded as an untested material: when it fails, it can fail catastrophically.
When the Titan is submerged, communications with the support ship on the surface are conducted over an acoustic link. Crewed submersibles sometimes have two separate systems with independent power supplies: one an acoustic beacon that regularly pings the ship to reveal its location, and another that can carry short text-like messages. This ensures that if the main power supply fails, the beacon keeps working, allowing the surface ship to track the vessel. According to some reports, the Titan did not have an acoustic beacon and had become lost before.
In the event of a major power failure, the Titan should have dropped its weights, resurfaced, and made immediate radio contact with the support vessel – provided the radio communications had a separate power supply. If an incident onboard the vessel knocked out all the electrics, the submersible could be adrift on the surface and awaiting rescue.
US and Canadian ships and aircraft have been scrambled, but the bus-sized Titan will be hard to spot in such a vast area of ocean. If the Titan has surfaced, the danger for the crew is not over: the hatch appears to be bolted from the outside, meaning those inside will still need to rely on emergency oxygen to breathe.
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One grim possibility is a fire in the cabin. The air in a submersible tends to be enriched with oxygen, making fires more risky. For this reason, petroleum-based skin creams and makeup are typically banned in deep dives, but fires can still take hold and swiftly produce smoke that intoxicates those on board. An emergency ascent should still be possible, however.
If the vessel has become stricken on the seafloor, only specialised deep-sea submersibles and sonar equipment have a good chance of finding it. The Titan embarked with enough oxygen to sustain the pilot and crew for four days, but limited air is not the only issue. If the vessel had lost power, temperatures inside the cabin would have quickly fallen to a frigid 4C, Williams said.
The scenario most feared is that the vessel suffered a catastrophic failure. At such depth, a hull breach would be devastating. “If something’s gone wrong, there’s a good chance it’s gone very wrong,” said Williams. “If the pressure vessel has failed catastrophically, it’s like a small bomb going off. The potential is that all the safety devices might be destroyed in the process.”
Such a fate would probably trigger signals in military hydrophones that are deployed throughout the world’s oceans. When an Argentine submarine was lost in 2017, hydrophones off Ascension Island and the Crozet Islands detected an acoustic signal consistent with a catastrophic failure of the submarine. “Just knowing where the vessel is is a big consideration,” said Williams. “The best case scenario is that the vessel has popped up and can be found visually or with radar.”
