THE former commander of the Faslane naval base has said that the crew of an Argentinean submarine lost in the south Atlantic would have had little chance to survive the disaster.

Speaking as it was announced that the rescue element of the search had ended, retired Commodore Eric Thompson said that the 44 submariners would have faced an agonising choice of suffocating or abandoning the ship and drowning in rough seas. 

The ARA San Juan submarine went missing on November 15, and hopes for survivors had already dimmed because experts said the crew only had enough oxygen to last up to 10 days if the submarine remained intact under the sea.

However, Mr Thompson said that it was unlikely the submarine stayed intact that long.

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The navy has said the vessel's captain reported that water entered the snorkel and caused one of the submarine's batteries to short circuit. The captain later communicated by satellite phone that the problem had been contained, but this was the last that was heard from the vessel.

Some hours later, an explosion was detected near the time and place of the San Juan's last position.

Former Commodore Thompson, 74, said: "In diesel-electric submarines, the battery is crucial. It is the only source of power when below periscope depth.

"Without electrical power, a diesel-electric submarine can neither propel nor pump out excess water which may be causing her to sink.

"As San Juan sent no further signals after reporting a battery problem, it may be concluded either that she had lost electrical power, at least to her radios; was below periscope depth and unable to transmit; or her crew had been incapacitated; or all three."

Saltwater reaching the battery would have produced toxic gas, incapacitating the crew, and surfacing would have proven futile.

The San Juan was sailing in rough seas and would have been swamped by waves, and submarines do not carry lifeboats allowing the crew to abandon ship.

Worse, if it sank away from the continental shelf, the depth would eventually force the vessel to implode.

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Commodore Thompson said: "Above a certain depth, the crew could have blown her buoyancy tanks – that does not require electrical power – and surfaced, but in heavy seas she would still require power to retain buoyancy.

"If the atmosphere on-board was toxic following an explosion, the crew, if still alive, would then have faced the option of death by gas poisoning or by drowning – there is no upper deck on a submarine and life rafts are not carried. Submarines do not fail safe."

A navy spokesman said this week that the blast could have been triggered by a "concentration of hydrogen" caused by the battery problem reported by the captain.

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The San Juan, a German-built diesel-electric TR-1700 class submarine, was commissioned in the 1980s and was most recently refitted in 2014.

Some family members have denounced the navy's response to the sub's disappearance as well as the age and condition of the vessel, while President Mauricio Macri has promised a full investigation.

Relatives of the crew broke into tears after they received the news that the search had been called off.

"I don't understand this arbitrary and unjustified decision," Luis Tagliapietra, the father of 27-year-old crew member Alejandro Tagliapietra, told local TV.

"It's unusually cruel. Every day, it's a new blow. I'm destroyed."