Why is finding a missing submarine in the ocean like 'looking for a needle in a haystack'?

On June 19, OceanGate Expeditions announced that their submarine had suddenly disappeared at sea with 5 members of the expedition. It is known that this ship was planning to dive to a depth of 3,700 meters underwater, about 600 meters off the coast of Newfoundland.

On June 18, 2023, Titan, a tourist submarine, suddenly went missing and searchers have been frantically hunting for the submarine in the North Atlantic Ocean ever since, according to CBS News.

In this submarine were the captain and 4 passengers who paid 250,000 dollars each to see the wreck of the Titanic . Immediately after the incident broke out, the Coast Guard led this special rescue mission, but in reality this was an extremely difficult job.

OceanGate calls Titan the world's only manned submarine that can carry five people 4,000 meters below the ocean's surface . The 22-foot-long carbon fiber and titanium vessel, called Titan, was deployed by a Canadian expedition ship, the MV Polar Prince, to travel nearly 13,000 feet to the shipwreck site, on the ocean floor off the coast of Newfoundland.

Aside from the typical problems of a rescue at sea — things like frigid water temperatures, rapidly changing weather conditions, and pitch-black water at night — there are other issues at play, such as radar being unable to penetrate the ocean's saltwater, according to The New York Times and Forbes.

Even using sonar (acoustic navigation and ranging) , which can penetrate water using sound waves, is not an easy fix because it requires a "specialized" technique using a "very narrow beam" to find the small submarine at a depth of 13,000 feet (nearly 4km), which can take too long, forensic geologist Jamie Pringle told Forbes.

Five people were on board the submarine : Stockton Rush, founder and CEO of OceanGate Expeditions, the company that operates the ship; Hamish Harding, a British businessman and explorer; another British businessman, Shahzada Dawood, and his son, Suleman, who come from one of Pakistan's wealthiest families; and Paul-Henri Nargeolet, a French marine expert who has made more than 35 dives to the Titanic wreck.

Sonar may not be an effective solution

While radar works well for tracking a ship on the ocean, it's nearly useless beneath the waves . According to the Carnegie Museum of Natural History, radar uses electromagnetic waves, and the ocean—due to its massive size—quickly absorbs the waves, which can only penetrate a few meters deep. Additionally, salt water is 'virtually opaque to electromagnetic radiation ,' according to JHU Engineering.

Rescuers are currently using sonar buoys that can detect sounds at depths of up to 13,000 feet (nearly 4km) in the hunt for Titan, according to CBS News, but even this technology cannot guarantee successful detection of the submarine.

Acoustic navigation and ranging, or sonar, is a way to find your way in the ocean because sound waves travel farther than light waves underwater. Active sonar equipment sends signals into the water. If it encounters an object, the waves bounce back from that object as an echo that is received by a sonar transducer. It measures the time between sending out the sound wave and receiving the echo to determine exactly what object returned the wave.

The Coastguard reported hearing underwater noises using sonar, but retired Rear Admiral Chris Parry of the Royal Navy told Sky News there was "a lot of banging in the ocean".

Difficult rescue

Chris Parry told Sky News that the remains of the Titanic itself could be the source of the noise due to its "deteriorated structure ." Coast Guard Rear Admiral John Mauger appeared to admit that the noise did not necessarily come from the submarine, calling the site "extremely complex" and filled with metal objects, according to CBS News. At this point, naval experts are still trying to determine the exact source of the noise.

Even if rescuers can locate Titan, getting it back to the surface will be another major challenge. If the sub is at the bottom of the ocean, the amount of pressure exerted on it is equivalent to 'a solid lead tower as tall as the Empire State Building,' according to The New York Times. They will need to use remotely operated vehicles called ROVS to pinpoint its exact location before attempting to attach cables to pull it to the surface while avoiding any obstacles in their path, according to The Guardian.

Means to find the Titan submarine

In addition to the use of sonar (sound navigation and ranging) technology mentioned above, the search for the missing Titan ship also required the use of many different types of vehicles, especially aircraft and ships, such as:

C-130: An aircraft operated by the US Coast Guard that launches sonar probes to detect sounds coming from deep in the ocean.

P8 Poseidon: Canada's multi-mission aircraft is known for its speed, which helps narrow down search area size and probability when searching for ships like Titan.

Odysseus 6K Submersible : The Odysseus 6k is an ultra-high-tech remotely operated vehicle (ROV) that can dive to depths of 6,000m. It is operated by the California-based Pelagic Research Service (PRS). It is equipped with two hydraulic arms, although it is not designed to lift anything weighing 9.5 tons like the Titan.

Victor 6000 Submersible : The second super high-tech submersible is the French Victor 6000, deployed by the Atalante and capable of reaching depths of 6,000 meters. It has a similar shape and design to the Odysseus 6K.

Deep Energy: One of the largest ships ever built, with a speed of 19.5 knots. The ship is capable of laying rigid pipes, flexible pipes. at depths of up to 3,000 m using the reel-lay method. In this mission, it can help in scanning the water for submarines.

The Atalante: This French research vessel carries the Victor 6000 autonomous robot, which can dive to depths of up to 6,000 meters, deeper than the Titanic's 3,800 meters, according to Reuters. The Victor has been in service since 1999. It weighs more than 4 tons, has a high-definition 4K camera, and is connected to the Atalante by an 8.5-kilometer cable that transmits 20 kilowatts of power. The Victor may go to the Titanic wreck to search.

Skandi Vinland: This Canadian multi-purpose offshore support vessel, built in Norway, has two remotely operated vessels built on board to search for the submarine.

Canadian CGS John Cabot: This offshore fishing vessel is capable of using sonar technology.

His Majesty's Canadian Ship Glace Bay: This Canadian warship conducts search and rescue missions, provides mobile decompression chambers for those resurfacing, and can carry medical professionals to treat diving-related injuries.