My inside sources have informed me that the ARA San Juan last made contact with the Argentinian Navy at 0730 on November 15. At that time, they reported a failure in the battery system due to an injection of water through the snorkel mast, which caused a short and a small fire. The problem was reported as resolved and the sub intended to dive and return to port at Mar del Plata, but they never arrived.
The Comprehensive Nuclear Test Ban Treaty Organization (CNTBTO) was established in 1996 to monitor nuclear tests to keep nuclear nations honest. They created a network of 337 monitoring systems around the globe, consisting of sensitive hydrophones that can hear a variety of underwater sounds. Only eleven hydrophones are needed to pick up marine life, earthquakes, and non-nuclear explosions.
On November 15, at 1358 GMT, CNTBTO hydrophones recorded an explosion that was later analyzed by Bruce Rule, an acoustic analyst who worked for the Office of Naval Intelligence (ONI) for 42 years. He analyzed acoustic detectors after the loss of the USS Thresher (SSN 593) in April 1963. With assistance from other experts, the determination was made that the explosion recorded on November 15 was made by the collapse (implosion) of the ARA San Juan’s pressure hull when it reached its crush depth of 1275 feet.
The energy released by the collapse was equal to an explosion produced by 12,500 pounds of TNT. This produced a “water ram” that rushed into the submarine at 1800 mph, destroying the sub in a fraction of a second. Although the crew may have known that a catastrophic event was imminent, it is reasonable to assume that death was painless and instantaneous.
This tragic event is similar to what experts believe happened to the USS Scorpion (SSN 589), which was lost on May 22, 1968. Acoustic analysis revealed that hydrogen out-gassed by the main battery may have caused an explosion that sent the sub to the bottom, over 11,000 feet down. It took 22 minutes for the submarine to reach its crush depth of 1530 feet.
The San Juan was more than 6,000 kilometers from the nearest CTBTO hydrophone located on Ascension Island, however, that sensor detected a small spike in sound waves indicative of an explosion. “In the case of the Argentinian submarine,” said Lassina Zerbo, Executive Secretary of CTBTO, “looking for an explosion signal this small was like looking for a needle in a haystack.”
Zerbo and his team were also involved in the search for the missing MH370 Malaysian airplane that crashed in 2014. Said Zerbo, “For months we were working, at points, we would think we had a signal, we would send people to check, and it would just be an old ship.”
With the ARA San Juan, the International Monitoring System detected the explosion, and based on subsequent analysis, experts have confirmed what happened. The Argentine Navy, assisted by the U.S. Navy and other nations, are now searching for the remains of the submarine.
I know that all of us in the submarine community have been hit hard by this. Many of us came within a breath of suffering this same fate. Our hearts and prayers go out to the families and friends of the San Juan’s crew, who are now on eternal patrol.