ARA San Juan: what happened to missing Argentine submarine?

News emerged today that the Argentine navy has called off its attempts to rescue 44 crew members on board a submarine that went missing two weeks ago.

“Despite the magnitude of the efforts made, it has not been possible to locate the submarine,” navy spokesman Enrique Balbi said yesterday.

The ARA San Juan’s oxygen reserves were estimated to have run out over a week ago, extinguishing almost all hope of finding the crew alive.

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However, reports of a “suspected explosion” near the craft’s last-known location have sparked numerous theories about what could have happened to the submarine.

Battery failure

Before going missing, the ARA San Juan had experienced issues relating to its battery, reports Sky News.

Navy spokesman Enrique Balbi told reporters that the captain of the submarine said water had entered the battery compartment through the vessel’s snorkel while its batteries were being changed.

State television in Argentina reported that the last communication from the crew revealed a leak of sea water had caused a short circuit and “the beginnings of a fire” in the batteries, the Daily Telegraph writes, but adds that the Argentine navy refused to comment on this theory.

The Washington Post theorises that the battery may have exploded, “inflicting critical damage”.

Torpedo explosion

Another theory revolves around the ARA San Juan’s arsenal of torpedos, which the San Francisco Gate hypothesises might have exploded while still attached to the sub.

This would be a similar fate to Russia’s K-141 Kursk submarine, which sank in the Barents Sea in 2000 after a fire caused by a faulty weld detonated eight of its torpedos simultaneously. The explosion killed all 118 crewmen and was registered on Richter scales as far away as Alaska.

Hydroacoustic engineer Mario Zampolli, who is conducting a search of the marine area for clues, told Nature.com that this may have occurred on the ARA San Juan, but adds that it is hard to prove that the sound recorded shortly after the craft disappeared was an explosion of that nature.

“The fact that it was detected with a good signal-to-noise ratio at Ascension [Island] — 6,000 to 8,000 kilometres away from the source — means it must have been fairly loud. Some aspects of the signal are consistent with what has been seen in explosions before. But it is really very difficult to say that this was an explosion.”

Crush depth

Another possible cause is that the ARA San Juan may have sunk below its “crush depth”, or “collapse depth”, at which point “its structure (would) not be able to withstand the water pressure”, writes the Straits Times.

The “crush depth” of most submarines is classified, but CNN reports that a modern submarine may begin to struggle at depths of around 500-600m below sea level. The ARA San Juan search location lies on the edge of the continental shelf, where ocean depths vary, but reach as deep as 3,000m.

“If a submarine goes below its crush-depth, it would implode, it would just collapse,” James H Patton Jr, a retired navy captain, told the Straits Times.

“It would sound like a very, very big explosion to any listening device.”

Attack from other craft

The most unlikely of the scenarios theorised, there was quiet speculation that the ARA San Juan may have sunk after being attacked by a foreign submarine.

In a new meeting with the press last week, Argentinean navy spokesman Enrique Balbi stated that he had no reason to believe the ARA San Juan was attacked, writes the Guardian, but with limited evidence, Balbi did not entirely rule it out.