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Stealth Tech Blamed for International Sub Crash, French Crew Unaware They'd Hit Anyone for Days

How could two submarines end up colliding in the middle of the ocean? British military types are blaming excessive stealthiness, and the French claim they didn't realize what had happened for days.

A Royal Navy source told the Times:

It is remarkably difficult to detect a modern submarine with sonar and we work very hard with our own submarines, as do our allies, in making them as quiet as possible so they are not detectable.

And he's serious about that—even after realizing they'd hit something, the French crew couldn't tell what it was. They wrote the object off as a shipping container, only to find out that they had actually collided with another submarine upon docking three days later, after the government had deduced the collision from routine information exchanges with the British.

The problem was that both submarines use passive sonar to map out their surroundings, which doesn't give away their location with the 'pings' of active sonar, and is somewhat less sensitive. Without these 'pings', it was nearly impossible for either sub's passive sonar to detect the other's, leading to the collision and subsequent confusion.

In reality, the whole thing was a bit more subdued than initial reports (or our imaginations) led us to believe. The subs, which were traveling very slowly, just sort of bonked into on another, and the only critical damage to either vessel was to the French sub's sonar system.

How Nuclear Subs Could Go Bump in the Night

Great Britain and France have always had their cultural differences, but the latest military miscommunication between the two hardly has them shouting vive la difference! This one literally could have gone nuclear.

A couple of elite nuclear submarines, the British HMS Vanguard and the French Navy's Le Triomphant, collided in the Northern Atlantic on Feb. 4 while "conducting routine patrols," both countries acknowledged on Sunday. Both subs are armed with multiple-warhead nuclear missiles.

But the Vanguard and Le Triomphant are also equipped with some of the most sophisticated military sonar devices available, complete with various antennas and sensors that collect information that is analyzed by high-powered computers.

So how is it possible that two nuclear subs of allied countries, both carrying state-of-the-art sonar equipment, could bump into each other?

"Sonars come in two flavors," John Pike, director of the Globalsecurity.org, told Foxnews.com.

"There's passive sonar and there's active sonar. These ballistic subs spend most of their time hiding with a nuclear arsenal. They use passive sonar to remain as silent as possible."

Passive sonar, which listens without transmitting, is particularly helpful in stealth situations, but what happens when two ballistic submarines designed to hide and remain silent are within close range?

"Active sonar is like a flashlight in the dark. I can use that flashlight to see, but everyone can see where I am," said Pike. "Passive sonar accuracy becomes much more ambiguous at close range."

Submarine collisions are rare, but they do happen. In 2001, the USS Greeneville surfaced and collided with a Japanese ship, the Ehime Maru, off the coast of Hawaii. The Navy determined the commanding officer of the Greeneville to be in "dereliction of duty."

During the Cold War, Soviet and American submarines often played cat-and-mouse, and near-collisions took on a dimension of international crisis.

Times have changed, but the danger is still enormous.

The HMS Vanguard is one of the Royal Navy's V-Class subs. It is armed with 16 ballistic nuclear missiles and forms a "Trident nuclear deterrent." Le Triomphant carries 16 M-45 class Sea-ground-Strategic ballistic missiles, also armed with thermonuclear warheads. An accident, even an unintentional one, could have had serious consequences.

The French and British navies said the collision was unavoidable, because the vessels were "running silently" to avoid sonar detection.

Le Triomphant has the British built DMUX 80, which provides passive target ranging and interception capability. The Vanguard carries the Thales Underwater Systems Type 2054 composite sonar — a multi-mode, multi-frequency multi-million-dollar detection system that failed to detect the 453-foot-long French sub until they butted.

The Vanguard has two periscopes, a CK51 search model and a CH91 attack model, both of which have a TV camera and thermal imager as well as conventional optics.

"But the periscopes are useless at that depth," Pike said.

"It's pitch black after a couple of hundred feet. In the movies like 'Hunt for Red October,' you can see the subs in the water, but in reality it's blindman's bluff down there."

"The crash could have been a coincidence — some people win the lottery — but it's much more possible that one vessel was chasing the other, trying to figure out what it was."