Jul 10 2020

Hunting what you cannot see

HIGH NORTH, Iceland. The needle in the haystack would be easy. A submarine hundreds of metres underwater, in an area the size of Denmark is something else.

The operations room, the room you never get to see pictures from, is the frigate's brain. It's almost like in the movies, with walls covered in monitors, and dozens of computer consoles. At the screens, there are radars spinning, sonars scrolling and messages flashing. Gus sits in one of the corners, hunting for submarines. Gus, who is actually named Terje Gustavsen, is 33 years old, a sonar specialist who has been hunting submarines since 2006.

- “All we really do is send loud noises into the water, and listen to its echo”.

He makes it sound simple. It’s not a new concept either, it’s been used since World War II. But actually finding a modern submarine is anything but easy.

There is a seemingly random array of hundreds of dots on his monitor. Even when he explains it, it still just looks like chaos. With his noise-cancelling headset, to exclude all room noise, he listens to the ocean. The noise is visualised in front of him at the same time. The ocean sounds a bit like a 20-year-old TV with no signal.

And how does a submarine sound? A bit like the same TV, with a slightly different pitch. All vessels in the world, no matter how similar they were built, have their own distinct sound, or signature, as the professionals call it. That means they can identify a vessel only based on the noise they project into the water.

- “It takes a bit of experience to get good at it”, Gus explains.

- “A lot of experience”, says his companion, smiling – “I want that in the article".

Images: The active sonar, being towed behind the ship, is their most effective sensor for submarine hunting.

An untrained ear would not be able to hear any difference in the noise, if you weren’t warned that it was coming.

And then there’s the active sonar, the best way to find a submarine. The noise would scare any submarine crew. It sounds a bit like the first seconds of a fire fighter siren, but varying in pitch every time it comes around. It’s loud, and the water carries the sound far. This is the sound from which they hear the echo, if there is anything lurking under the surface.

Grandpa survives

ASW. Anti-Submarine Warfare, also known as Awfully Slow Warfare is a test of patience and focus. Submarines were a big threat in World War II, and still are today. Gus' grandfather was a sailor in the Norwegian civilian shipping fleet during the war. He was a steward, but had a second job as a gunner on the anti-aircraft guns on deck. No less than three times was he torpedoed, and survived all. Twice by a submarine, and once by a plane. If he was inside the Galley and not on deck, he would have died.

Today’s naval wars are a little different. Missiles flying three times the speed of sound are effective, but the torpedoes are still the biggest threat.

- “You may have the vessel still floating after a missile strike, but if a torpedo hits you, no chance”.

And since everything is about noise, it effects the crew as well. When in a threat area, you have to walk quietly, and close every door as quietly as possible. Anything rattling or vibrating needs to be taken care of. Gus calls them noise shorts.

- “A wrench hitting the deck can be enough to be spotted, with fatal consequences. That means that there may be less comfortable times on board, but this is what we are built for”.

Images: The torpedoes are specially designed for anti submarine warfare, and are shot out from the side of the ship with air pressure.

Working together

Effective submarine hunting rarely happens alone. Multiple frigates working together with planes and helicopters, give the best range and endurance. A plane can drop a sonar buoy from the air, and listen to the signals far out of range of a submarine, and a helicopter will “dip” it's sonar from a wire hanging underneath the helicopter.

- “We back each other up. A plane can cover huge areas in short amounts of time, and surface ships have the endurance to stay put for weeks”.

Exercise Dynamic Mongoose, where we are now, is an opportunity to train all this synchronised in a realistic scenario. It is one of the biggest anti-submarine warfare exercises NATO has, with five surface vessels, five submarines and five maritime patrol aircrafts.

- “Anti-submarine warfare has really increased in the last 5-6 years, with a lot of focus and commitment to the field. It's also very important for Norway, with large maritime areas”.

The Norwegian Nansen-class frigate Gus works at is especially designed for submarine hunting. It’s very quiet, with competent crew and advanced sonars.

Story by Standing NATO Maritime Group 1 Public Affairs

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