A听massive search and rescue operation is underway off the coast of Argentina. Last Wednesday, the ARA San Juan, an Argentinian military submarine, went missing with 44 crewmembers on board. There鈥檚 a good chance the crew are still alive and trapped inside. Now the tricky part is finding them. Teams from Argentina, Brazil, the US, the UK and France, among others,听have now united to find the submarine, but there isn鈥檛听much time left.
The search hasn鈥檛 been helped by misleading signs. On Saturday, seven weak satellite signals potentially from the stricken sub were detected but the Argentinian navy later concluded these were . The same is true of noises heard by sonar in the water on Monday. It was initially thought that the sounds might have been made by submariners banging on the hull in Morse code to attract attention, but they too have .
Where is it?
The San Juan disappeared roughly halfway between a naval base at Ushuaia on the southern-most tip of South America and the base at Mar del Plata, just south of Buenos Aires. The search area could be听.
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And the sub is unlikely to be floating on the ocean surface 鈥� planes have been surveying the area with highly sensitive radar, and they probably would have found the vessel by now says Jonty Powis, former programme manager of the . Instead, the submarine is most likely resting on the ocean floor in an upright position. Submarines are carefully ballasted with heavy equipment in their lower halves, he explains, which should prevent it from rolling over.
With luck, the San Juan has been able to release an emergency buoy to the surface that will be transmitting its location. But finding that could be tricky 鈥� shows rough seas.
How will we find it?
Rescue teams will be turning to side-scan sonar to actually detect the San Juan, says David Shea, VP of engineering at surveying firm Kraken Robotics. Side-scan sonar can produce incredibly detailed images of the seabed and what鈥檚 on it. It鈥檚 what was used in 1999 in听the successful search for the, an Israeli-operated submarine that sank in 1968.
鈥淭he advantage you have in that case is the submarine is a very large thing in comparison with other things on the seabed,鈥� he explains. 鈥淎nd the chances are high that it is intact as oppose to an airplane which would most likely be in many pieces.鈥� 听This is because aircraft hitting water during a crash are impacted with such force that they usually break up.
Given that the San Juan was diesel-powered, Shea also thinks there鈥檚 a chance that it could be leaking fuel. This might be picked up on the surface by aerial surveys or by underwater vehicles with chemical detectors.
What do we do when we find it?
Steve St Amour 鈥� a veteran of ocean search operations 鈥� was involved in听the effort to locate the INS Dakar. One听ship was dragging a sonar device in its wake to locate potential targets for closer inspection. 鈥淢y ship had the remotely operated vehicle, and we were diving the targets as they were found,鈥� recalls St Armour. 鈥淚t was like target number nine that we found her.鈥�
If it is found, it鈥檚 possible to escape from a submarine, says Powis. Crew members may have special inflatable suits which they could don before entering a chamber at the top of the sub, which is subsequently flooded. A hatch is opened and they can rise to the surface. But there鈥檚 a catch.
鈥淚t鈥檚 been done at 183 metres in a trial but beyond that, people adversely effected by the hyperbaric burden,鈥� says Powis, referring to the dissolved gases that begin to form bubbles in divers鈥� bodies if they come up too quickly. Unfortunately, because of the geography of the ocean in this area, the San Juan is likely to be at a depth of 200m or greater.
The other option is to use a submarine rescue chamber, a kind of capsule that can be lowered to the vessel and carry several crew members steadily to the surface.
Can we get there in time?
鈥淭here are emergency rations which deliver a certain amount of calories per day 鈥� particularly in order to keep kidneys functioning,鈥� he says. There will also be supplies of water and oxygen, but these will begin to run out after one week. However, by minimising their activity and movements, they could stretch these rations to ten days.
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