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The loss of the ARA San Juan and how a retired analyst from the US ONI could have solved the mystery

ARA San Juan. Photo: Armada argentina.

ARA San Juan. Photo: Armada argentina.

11/01/2018 | Orlando, FL

Gabriel Porfilio/Bruce Rule

On November 15th , 2017 Argentina’s Navy suffered the most devastating loss since the Falklands/Malvinas War, the ARA San Juan, a TR1700 Class submarine built by German shipyard Thyssen Nordseewerke specially for Argentina, lost contact with its base and sank to the bottom of the sea. Since then, a multinational combined effort has been searching for the lost boat without any success.

In the middle of this crisis, several theories were presented by Argentina’s Navy spokesman, Capt. Balbi, indicating a vast array of possibilities maintaining hope that there could be some chances of rescuing the sailors and recovering the boat. This line of thought was preserved for days even after the oxygen reserves on the boat, if any, would have been completely depleted. After several days of that, it was finally accepted that the boat was lost with all its sailors.

While reviewing different specialized forums where there were discussions about the different possible scenarios that could have led to the demise of the ARA San Juan, I stumbled upon a very detailed analysis, signed by Bruce Rule, with very precise information about the location of the incident, the depth at which the boat collapsed (imploded), sea pressure, frequency, energy and a vast array of data that it was very hard to ignore. Since the post was quoted and I couldn’t find its origins I started a quest to reach out to this analyst (whose name I was familiar with as he published technical assessments on the loss of the US Navy boats USS Thresher and USS Scorpion). I needed to verify if he was the author and if so, why the Argentine Navy was not mentioning his findings.

After some digging and annoying Mr. Lownie, webmaster of the IUSSCAA (Integrated Undersea Surveillance System – Ceasar Alumni Association) webpage, he agreed to provide me the direct email for Mr. Bruce Rule and I am very thankful for his support and hope one day he will forgive me for annoying him so much.

With that in hand, I proceeded to directly contact Mr. Bruce Rule, first to confirm if he was the author of the analysis and then to see if I could get more information about it. Mr. Rule responded almost immediately, and he confirmed the authorship of the analysis and offered his invaluable cooperation for this article.

After that first contact, Mr. Rule provided with an updated version of the original analysis which brings some light to the chain of events that could have caused the loss of the boat. The report, based on the analytical review of the information provided by the CTBTO regarding the signal detected on November 15th, 2017, literally says that it has been established that the event signal was originated near 46-10S, 59-42W at 13:58Z (GMT) hours and was produced by the implosion of the ARA San Juan pressure hull at a depth of 1536 feet (468m). The sea pressure at the collapse depth was 684 PSI and that the frequency of the collapse event signal (bubble-pulse) has been revised from the original analysis of 4.4 Hz to 4.68 Hz. At this point, it is important that I mention that the implosion of any pressure hull will provide a very special acoustic signature (bubble-pulse) and it can be identified precisely by trained analysts. This is the first element that deeply surprises me on the way the Navy conducted its communications. Once the report from the CTBTO was sent to them (the US Navy had provided a similar one before) if the Argentine Navy did not have the ability to process them, they should have sent it to other agencies that could have prepared a report on them. Still, Capt. Balbi, mentioned right after communicating to the press that they had received the report from the CTBTO that it was consistent with an explosion but rapidly clarified that underwater, that is an implosion. This assertion is questionable and probably it was a mind trick, he probably knew that the submarine had imploded but needed to only communicate that the report mentioned an explosion. If the implosion was confirmed, the demise of all the sailors would have been confirmed and at that stage the Navy only wanted to see if they could find the boat and provide some hope to the families.

Going back to the report prepared for Mr. Rule, it confirms that the energy released by the implosion was equal to the explosion of 11,476 pounds (5 tons) of TNT and it was produced by the nearly instantaneous conversion of potential energy (sea pressure) to kinetic energy created by the motion of the intruding water-ram at a speed of about 2000 mph (894 m/s) and clarifies: “That energy was not produced by an explosive event”  Now with this analysis, we can again compare the events described by Mr. Rule versus the different versions provided to the press by Capt. Balbi, which kept defining the event as being ‘consistent with an explosion’ and the declarations of the Executive Secretary of the CTBTO, Lassina Zerbo, that came out to the press to present a totally different version of the acoustic event saying that it was small and probably either the submarine moving or a small explosion on its engines. This created even more confusion as the head of the organization that presented a key proof of the submarine demise was now contradicting its own report diminishing its importance. Luckily for the investigation Mr. Zerbo did not ‘cooperate’ with it anymore and his comments were dismissed.

Continuing with Mr. Rule analysis, he confirms that if any of the crew members were still alive and functional at the time of collapse, their death was instantaneous, and they did not drown or suffered any pain. The event happened in about 40 milliseconds, half the minimum required for cognitive recognition of an event by any human being.The entire pressure-hull was destroyed and sank vertically at a speed between 10 and 13 knots. This secondary event (bottom impact) wouldn’t have produced any significant acoustic event detectable at long range.

Now, after reading the first part of the report, the overwhelming amount of precise data, leaves no questions to what happened the ARA San Juan except one, why?

From our email exchange with Mr. Rule and reading the second part of his analysis we can come to some probable causes that started the chain of events ending on the loss of the boat. First, the analysis brings back Mr. Rule's report on the loss of the USS Scorpion, a nuclear submarine that sank in 1968. That tragedy was caused by hydrogen out-gassed by the main battery bank that exploded inside the submarine incapacitating or killing the crew with an over-pressure in the battery well of between 7 to 10 times greater than the fatal value for human beings. The pressure-hull resisted the explosion without being breached but without power and no crew the submarine sunk slowly until it collapsed at almost the same depth than ARA San Juan, 1530 feet. Now, Mr. Rule observes that the USS Scorpion internal explosion was detected at 821 nautical miles, but if the same happened to the ARA San Juan, this event would probably not be detected by the CTBTO hydrophones located at 2300 nautical miles. The only precise way to determine if this was what caused the loss of the ARA San Juan would be finding its wreckage and perform a deep study of its remains including microscopic, spectrographic and x-ray diffraction analyses as it was done with the USS Scorpion. The second possibility is that sea water that came in to contact with the battery system did not cause an explosion but generated gases that incapacitated or killed the crew.

Both options have the same ending, the crew was incapacitated or killed by a major and extremely fast event, probably produced by sea water entering through the snorkel and coming in to contact with the submarine batteries, which left either the submarine inoperable or with nobody to operate it, thus the lack of emergency procedures to prevent the increasing depth or at least launch the emergency buoys that would have provided a distress signal. The event that incapacitated or killed the crew was of such magnitude that everybody on board had to be rendered unconscious almost instantly as the boat had emergency buoys at both ends, to provide some chance of launching them if an event happens at the bow or stern.


*Mr. Bruce Rule was the lead acoustic analyst at the Office of Naval Intelligence for 42 years and is the published author (royalties refused) of technical assessments of why the US nuclear submarines THRESHER and SCORPION were lost .

*Mr. Rule also wants to give credit, anonymously, to a Research and Engineering Consultant who provided critical inputs to the SAN JUAN assessment, especially the derivation of collapse depth and energy-release values. 

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