Posted on February 17, 2009 - by Venik

When subs collide

As we now know, a British and a French nuclear-powered, nuclear-armed submarines collided in the Atlantic earlier this month. Amazingly, the first newspaper to report the incident and to prompt the official admission of the accident was The Sun tabloid. The Royal Navy said that the subs “came into contact at very low speeds”, calling the incident a “fender bender”.

The reality is that the 138-meter Le Triomphant-class (specs) sideswiped the 150-meter Vanguard-class (specs) moving in the opposite direction. Both subs were built in 1990s, had nuclear reactors onboard and carried 16 nuclear SLBMs. They avoided a direct head-on collision by just a few meters. In other words, they got very lucky.

Royal Navy's Vanguard-class sub

Let’s imagine, for argument’s sake, that each sub was moving at 5 knots, which would qualify as “a very low speed”, considering that either sub is capable of doing around 30 knots fully submerged. The combined kinetic energy of the two subs would have been around 400MJ, which is equivalent to about 100kg of high explosives. Incidentally, a 100-kg warhead is what you would find on a typical anti-submarine torpedo. So there definitely was a good potential for some excitement.

“The accident probably happened because the two submarines were not aware of each other. NATO operates a traffic control system that alerts allied nations to the deployment zones of friendly submarines. The system is designed to avoid collisions. But because France is not part of NATO’s military command structure, it does not provide information on the location of its mobile nuclear arms to that system…”

(Did France’s Secrecy Cause a Nuclear Submarine Collision?, Time, Feb. 16, 2009)

And another idiot’s opinion:

“Both the Vanguard and Le Triomphant are among the most silent submarines ever developed,” Bruno Tertrais, a senior researcher at the Paris-based Foundation for Strategic Research, said today in a telephone interview. “The Atlantic is a big place, but coincidences can happen.”

(French, U.K. Nuclear Submarines Collide in Atlantic, Bloomberg, Feb. 16, 2009)

I don’t know who this Bruno character is, but he obviously knows little about submarines. The two subs in questions are designed to be quiet, that much is true. To be more precise, these subs are designed to be as quiet as very large nuclear-powered submarines can be, which is far from silent. Coincidences do happen but this is definitely not the case.

Launch of the "Terrible" nuclear sub

The sheer improbability of two submarines ending up at the same place at the same time in the vastness of the ocean is mindboggling. On the other hand, if we were to imagine that, for whatever reason, the two subs were playing games with each other (which is what submarines do when not at war), then the chance of a collision leaves the realm of astronomical probabilities.

And the British might have had a very good reason to be close to the French sub. There is a strong possibility that the sub involved in the accident from the La Royale’s side was the S619 Terrible, the latest of the Le Triomphant class inaugurated in early 2008 and equipped with all the latest bells and whistles that obviously piqued Royal Navy’s curiosity.

Interestingly enough, the French reported the accident a couple days after it occured, but said that their sub collided with an unidentified object. Of course the French knew their €1.6-billion toy didn’t run into a buoy or a whale – they were just being polite. On the other hand, it took an exposé in a tabloid for the Royal Navy to come clean about the accident.

Update: According to a report by daily Ouest France, the French submarine involved in the accident sustained heavy damage to the hull, including the sonar housing and the superstructure. The submarine is currently at the Brest port undergoing repairs. As I suspected, the collision might have been quite a bit more violent than the “fender bender” British military officials admitted a few days ago. While the French sub was able to make to port under its own power, the British Vanguard-class has to be towed to its Faslane base for repairs. In a statement, the First Sea Lord Admiral Sir Jonathan Band said:

“Both submarines remained safe and no injuries occurred. We can confirm that the capability remained unaffected and there has been no compromise to nuclear safety.”

(British, French nuclear submarines collide, CNN, Feb. 16, 2009)

I find it interesting how a sub’s capability can remain “unaffected” when it has to be towed to base and undergo weeks if not months of repair works. Russian media reports that each submarine was carrying up to 48 nuclear warheads.

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