Last Wednesday, a German-built submarine disappeared off the southern-most tip of South America. The submarine was returning from a routine mission to Ushuaia, when it vanished from the radar.

As the search intensified over the weekend, there was a brief moment of hope. A few satellite ‘blips' were intercepted, but unfortunately turned out to be a false alarm. No contact was made.

"It's not entirely clear that communications have been lost, but if they have been I don't think the prognosis is particularly good at the moment," said Andrew Davies, director of Defence and Strategy at the Australian Strategic Policy Institute in Canberra.

Dr Davies has assisted the Australian Defence Department with technology to detect submarines for over ten years. He highlighted that although a submarine's ability to hide at the bottom of the ocean is the vessel's major strategic advantage, in times like this it is a downfall.

The last known location of the San Juan was 430km off the Argentinian coast. The search is taking place around the San Jorge Gulf, but stormy weather and rough seas are complicating the search.

According to Dr Davies, submarines are designed to rescue themselves. However, other variables often affect their ability to do so, like water depth and a variety of complications that can occur on-board.

"There are escape suits. You can basically pop out of the submarine in an inflatable suit and bob to the surface," he said.

"That's always a possibility, although you would think that if that was the case, that might have already happened by now."

Reports are saying there is enough oxygen on the submarine to keep the crew alive for two weeks. That is assuming a fire or other emergency has not occurred on board.

Five other countries have now joined the search for the missing submarine. And the US has sent advanced undersea equipment to assist with the search.

Antarctic patrol ship HNS Protector is currently scanning the depths below the South American tip, although hope is dwindling as each hour passes.

Relatives of the missing crew have gathered at the Mar del Plata base and are praying for a successful rescue mission.

Argentinian born Pope Francis included the 44 crew and their families in his Sunday prayers at the Vatican.