A SUBMARINE missing for five days with 44 crew members on board had reported a mechanical breakdown in its final communication, Argentina’s Navy have revealed.

However the organisation said final satellite calls did not come from the submarine itself, dimming hopes that those on board had survived.

“The vessel surfaced and it reported a breakdown. It was therefore asked to change course and go to Mar del Plata,” said Gabriel Galeazzi, the head of the naval base in the northeastern city, located 400 kilometres south of Buenos Aires.

Meanwhile Navy spokesman Enrique Balbi said seven signals received by naval bases over the weekend were not attempted distress calls from the submarine, as previously hoped.

“We’ve received the report from the company that analysed the signals — the seven attempted calls did not come from the submarine’s satellite phone,” he said, adding: “We have still been unable to contact them.”

The ARA San Juan has been missing for five days in rough seas after disappearing 430 kilometres off Patagonia on the country’s southeast coast.

Rescue aircraft and vessels are ramping up the search for the sub after a series of apparent attempted distress calls yesterday raised hopes they may be alive, with an electrical problem affecting communications.

But naval analyst James Goldrick, a former senior officer and leader of the Australian Defence Force Academy, told news.com.au that it was highly unlikely they had survived after so long.

“Every hour, the likelihood of their being found alive diminishes,” said the rear admiral, who commanded two ships and led Australia’s Border Protection Command during his career on the sea.

“I don’t hold up much hope of their being found.

“It would be fantastic if it turns out it was just communications, but after this amount of time, I don’t believe it will.

“You’d be fearing the worst by now.”

‘YOU COULD HAVE SURVIVORS TRAPPED AT BOTH ENDS’

The Argentinian navy was unable to confirm that the seven attempted calls originated from the submarine, after losing contact with the German-built, diesel-electric sub early Wednesday local time. “The communications are so short and the signal so low,” spokesman Enrique Balbi said.

Naval expert Fernando Morales told C5N TV there was a feeling of “cautious enthusiasm”, since to use a satellite phone, “the submarine had to emerge to a depth that allowed the call.”

The navy said there was enough food and air supply on board for the crew to survive for up up to a month if it is on the surface, but possibly only days if it is submerged — and if some disaster has happened, that may not count for anything.

But as time wears on, it seems increasingly doubtful the crew is alive.

The ARA San Juan is an old submarine, built in 1983, just after the Falklands War. Argentina’s navy has very little money and a fleet of just three submarines, but it has “been hanging on to its subs by its fingernails”, says before becoming an Australian National University researcher Goldrick.

Arrived on task in the search area in the early hours of this morning and have commenced sonar and visual search for #ARASanJuan as part of the ongoing multinational operation. Conditions remain challenging given current weather. pic.twitter.com/Sxgi9MZGo5 — HMS_Protector (@protector_hms) November 19, 2017

With the sub hidden deep in the ocean, it is impossible to know what has happened, but the retired officer speculates that something more than a communications failure has happened to prevent it from surfacing.

Submarines usually have indicator buoys that appear at the surface if a sub goes down, but with the vessel being so old, we don’t know what its capabilities were. The fleet was modernised between 2007 and 2014 to extend its use by about 30 years, but Argentina has been plagued by economic problems since the Falklands War.

If a compartment of the submarine has caught fire or flooded, “it gets very tricky to survive”, Goldrick added.

“If, let’s say, a pipe broke in a major compartment, you have to close that off,” he explained. “If there’s flooding in the centre of the ship or a fire in the control room, you could have survivors trapped at both ends of the boat.”

‘BELOW A CERTAIN LEVEL, THE HULL CRUSHES IN’

The impact depends on not only how bad the accident was, but also how deep the sub was at the time it happened. “If you’re relatively shallow, you’re OK, but if it’s deep, they’re all dead,” said Goldrick. “Below a certain level, the hull crushes in.”

It would also then be too deep for the crew to use any means of escape such as diving apparatuses because the human body cannot endure the pressure at such depths. If it was below crush depth, the sub would most likely have sunk, hitting the sea bed at any angle.

Even if the crew managed to escape the sub at a level shallow enough for them to reach the surface, it’s unlikely they would last very long in the cold waters off the San Jorge Gulf.

“It’s a rough part of the world,” added Goldrick, whoretired in 2012 after years of sea service. “How long could they survive in the water, even in protective clothing? There’s a whole range of things that could have happened.”

Relatives of crew members have unfurled a flag at the naval base in Mar del Plata — the sub’s intended destination — that reads: “Be strong Argentina, We trust in God, We wait for you.”

Claudio Rodriguez, whose brother Hernan is aboard the submarine, said he was hopeful the satellite signals indicated the vessel was still afloat. “They’ve got to be afloat,” he said. “Thank God.”

Argentinian President Mauricio Macri said the authorities were doing everything to find the sub as soon as possible. Argentina-born Pope Francis offered a “fervent prayer” for the submarine sailors’ safety.

The exact position of the ARA San Juan is still unclear. The TR-1700 class submarine had been returning from a routine mission to Ushuaia, near the southernmost tip of South America, to its base at Mar del Plata, about 400km south of Buenos Aires.

It appears to have taken a detour to gather information on illegal fishing. It is common in the region for foreign boats to exceed their quotas, transferring their haul to other boats so they can continue overfishing the South Atlantic Ocean.

Ten aircraft from countries including Brazil, Britain, Chile, Uruguay and the United States are conducting the search for the lost sub, focusing on an area about 300km in diameter, radiating from the last point of contact.

Rescuers are likely to be equipped with inflatable boats, life rafts, specialist communication equipment, rations, water and medical supplies, all of which can be dropped from parachutes.

California-based Undersea Rescue Command was deploying two underwater craft designed to rescue trapped submarine sailors. A NASA P-3 research aircraft has joined the search and Britain’s Royal Navy has just sent Antarctic patrol ship HMS Protector to assist.

A powerful storm has whipped up seven-metre waves, which has made geolocation difficult, officials said. Weather conditions are not expected to improve before Tuesday.