The following essay is reprinted with permission from The conversationan online publication about the latest research.
An extensive one search and rescue operation is on his way to locate a commercial submarine that went missing during a dive to the Titanic shipwreck.
According to the U.S. Coast Guard, contact with the submarine was lost about an hour and 45 minutes after the dive, with five people on board. The ship was reported too late at 9:13 p.m. local time on Sunday (12:13 p.m. AEST, Monday).
The expedition was led by US company OceanGate as part of an eight-day trip where guests paid $250,000 per head to visit the wreck site. From Monday afternoon (Tuesday morning in Australia) U.S. Coast Guard Rear Admiral John Mauger said the vessel likely had anywhere from 70 to the full 96 hours of oxygen available to the passengers.
The wreck of the Titanic lies some 3,800 meters deep in the Atlantic Ocean, about 700 km south of St John’s, Newfoundland. Finding an underwater vehicle the size of a small bus in this vast and remote expanse of ocean will be no small feat. This is what the search and rescue teams run into.
OceanGate’s submarine Titan is missing
Submarines are manned watercraft that move similarly to submarines, but within a much more limited range. They are often used for research and exploration purposes, including searching for shipwrecks and documenting underwater environments. Unlike submarines, they usually have a viewing window so passengers can see out, and external cameras that provide a wider view around the submarine.
The missing sub in question is an OceanGate Titan water scooter, which can take five people to a depth of 4,000 meters. The Titan is about 22 feet long, with speeds of about 3 knots, or 5.5 miles per hour. While submersibles are often tethered to a surface ship, videos and photos suggest that the Titan likely operated independently of the surface ship.
According to OceanGate’s website, the Titan is used “for on-site survey and inspection, research and data collection, film and media production, and deep-sea testing of hardware and software.”
It also has a “real-time hull health monitoring (RTM) system”. This likely includes strain gauges to check the health of the Titan’s carbon fiber hull. A strain gauge is a type of sensor that can measure applied force and small deformations in material due to changes in pressure, strain and weight.
The Titan’s carbon fiber hull connects two domes made of composite titanium – a material that can withstand deep-sea pressures. At 3,800 meters below sea level (the depth of the Titanic), you can expect a pressure that is about 380 times greater than the atmospheric pressure we are used to on the Earth’s surface.
![The OceanGate submarine](https://static.scientificamerican.com/sciam/assets/Image/2023/2R8760P.jpg)
Communications and rescue efforts
The Titan would have had an acoustic connection to its surface craft, set up via a transponder (a device for receiving a sonar signal) on the far end, and a transceiver (a device that can both send and receive communications) on the surface craft.
This link allows underwater acoustic positioning, as well as sending short text messages back and forth to the surface vessel – but the amount of data that can be shared is limited and usually includes basic telemetry and status information.
The Titan is a battery powered watercraft. Since it lost all contact with its surface craft, it may have suffered a power failure. Ideally, there would be an emergency power source (such as an independent battery) to maintain emergency and life support equipment – but it’s unclear if the missing ship had a power backup on hand.
According to reports, at least two aircraft, a submarine and sonar buoys were used to search for the ship. The sonar buoys listen for underwater noise, including any distress beacons that may have gone off.
One of the biggest challenges in the rescue effort will be related to weather conditions, which will further reduce the already narrow search window.
What could have happened?
At best, the Titan may run out of power and have a built-in safety system that will help it return to the surface. For example, it can be equipped with additional weights that can be lowered to instantly increase buoyancy and bring it back to the surface.
Alternatively, the ship may have lost power and ended up at the bottom of the ocean. This would be a more problematic outcome.
The worst case scenario is that it suffered a catastrophic failure in its pressurized housing. While the Titan’s composite hull is built to withstand intense deep sea pressure, any defect in its shape or construction could compromise its integrity – in which case there is a risk of implosion.
Another possibility is that there has been a fire on board, for example due to an electrical short circuit. This could compromise the vehicle’s electronic systems used for navigation and control of the vessel. Fires are a catastrophic occurrence in enclosed underwater environments and can potentially incapacitate crew and passengers.
Time is of the essence. The search and rescue teams will have to find the ship before it limited stocks run out of oxygen and water.
There is an ongoing debate in scientific circles about the relative merits of manned submersibles, with any deployment involving a safety risk – and the safety of the crew and passengers is paramount.
Currently, most underwater research and offshore industrial work is performed using unmanned and robotic vehicles. A loss to one of these vehicles could jeopardize work, but at least no lives are on the line. In light of these events, intense debate is likely to arise about the risks associated with using these systems to support deep-sea tourism.
This article was originally published on The conversation. Read the original article.