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The threat below: Tech adds new dimension to underwater warfare

Naval commanders want the same detailed picture of underwater operations their air and land counterparts have long enjoyed. New developments in acoustical processing, undersea networking and unmanned systems may soon revolutionize underwater intelligence, surveillance and reconnaissance (UW ISR).

In recent years, two incidents have shaped the perception of modern undersea warfare: the sinking of the South Korean corvette Cheonan by a North Korean torpedo last March and the 2006 surfacing of an apparently undetected Chinese Song-class submarine in the middle of a U.S. carrier group near Okinawa. Those incidents were psychologically powerful but remain shrouded in secrecy. Were the Korean and American ships even trying to detect and evade submarines and torpedoes? Could they have detected them even if they tried? The modern diesel-electric submarine is stealthy to an extreme, and in a cluttered littoral environment, virtually undetectable.

These are only the most recent unknowns in the underwater battle. From the first major surface-submarine duels of almost a century ago, through the Second World War until recent days, technology has continually redefined predator and prey. In the Second World War, sonar, radar, long-range aircraft and snorkels, among other technologies, all changed the battlespace.

“[In] the Cold War, it was cat and mouse, so every time you had development on the undersea side, the threat side, there was a counter development on their airborne ASW or surface or sub-surface ASW,” said Ken Walker, vice present of Ultra Electronics Maritime Systems. When the Cold War ended, many countries continued or began to acquire conventional submarines but airborne and surface anti-submarine warfare failed to keep pace. “I think there is a measurable gap between the two of them,” he said.

That gap has seen steady growth in the number of diesel-electric submarines in the world’s oceans. Their ability to hunt undetected is driving research to give commanders a more complete picture. In May, General Dynamics Canada announced a new Underwater Intelligence, Surveillance and Reconnaissance Centre of Excellence in Halifax, to “re-establish this critical capability in the face of new threats.” Working with Defence Research and Development Canada and sonar manufacturer Marport C-Tech, the goal is a new generation of underwater acoustic products for military ISR.

Technology duel
Sonar is being continually refined to illuminate the undersea darkness. From passive listening, sonar developed to active ‘pinging’ – transmitting a signal and analyzing the echo – sonobuoys released from ships and aircraft increased the range of sonar systems. Now, ‘multistatic’ technology uncouples transmitter and receiver, so a signal from one transmission point can be received and analyzed at other points that do not have to reveal their locations. The result weaves straight lines of sound into a net to capture undersea targets. “For antisubmarine warfare, we know that multistatics are going to have to be part of the solution against today’s quietest subs,” said Peter Giles of General Dynamics Canada.

“You want to make the sea-air interface basically seamless, so what you see in the air, you’d have a similar perception underwater,” Walker said. With data streaming in from a variety of sources, a critical piece is information processing. “Rather than rely solely on the acoustic detection capability of a sensor and its processing chain in order to pull out that contact, you’re fusing information from the radar surface picture, automatic identification systems, visual, infrared, and you’re trying to look at the total picture, get total situational awareness.”

For underwater warfare, processing would subtract things like known surface contacts. That eliminates or reduces the number of variables to focus on actual potential contacts. But that calls for a high degree of automation in the system, Walker elaborated. “In the Cold War, you had a lot of operators that had flown or worked against targets where they knew all the nuances – they had acoustic processors in their heads. More and more, you’re getting young sailors aboard a ship and, when they engage a threat, it’s the first time.” That dictates a requirement for ‘threat libraries,’ databases of vehicles’ signatures, friendly or otherwise, that systems can use to match signals. “If they don’t actually do the detection and tracking, they at least alert the operator to look at the frequency on a sonobuoy or look at the towed array in this direction. The ASW operator doesn’t get as much time on the target, so I think there is much requirement for the automation that’s brought about by the combination of acoustic processor, smart processing, data fusion and databases or threat libraries,” Walker said.

Weaving the net
The goal of underwater ISR is to give operators a three-dimensional view of the battlespace but the physical limitations of a water environment and the need for submarines and other assets to conceal their locations inhibit electronic and acoustical communication. If an underwater asset, manned or unmanned, finds a target or a threat, that information is probably only valuable if it arrives at its destination in near real-time. Otherwise, there is no point to doing the mission at all. At the same time, transmitting information means revealing location.

Networking is the key to the UW ISR domain, according to Rick Gerbrecht, Canadian business development director for ATLAS Elektronik. “The modern sensors have provided the submarine enormous volumes of both strategically and tactically important information. However, the tactical information is almost useless to the Task Group and HQ commanders in decision making if it cannot be passed back from the submarine in a timely manner.”

Submarine commanders never want to broadcast their locations, but new acoustic and wireless technologies will enable better communication of ISR data in near real-time without detection.

Building eyes with ears
Unmanned systems add an entirely new dimension to the struggle for undersea dominance. “UUVs [unmanned underwater vehicles] have the potential to provide the submarine an extension to its sensors’ reach,” Gerbrecht said. “This area presents enormous potential for increased UW ISR in the future.” The same communication technologies that will allow submarines to communicate with air and surface assets will allow them to communicate with each other, and with new generations of unmanned underwater vehicles.

Brett Johnson, formerly a frigate captain in the Canadian navy and now vice president of Alion Canada, said, “as a commander, if I wanted to investigate an area, it would be good to have a small fleet of UAVs or UUVs to go in ahead and check things out. If you are on the defensive, and you are trying to protect something, I can see unmanned underwater vehicles as helping to expand your eyes and ears outside of the area that you are trying to protect – kind of like sniffer dogs or a tripwire.” On the offensive, he said, unmanned vehicles allow advanced reconnaissance without risk to human lives.

Johnson noted that unmanned aerial vehicles are now becoming common on the battlefield, where they have enjoyed great success. Soldiers are learning how to operate them, and developing established rules and procedures, but underwater systems are still in an early stage of development. “AUVs are coming in to vogue in the next few years, I think. We are still experimenting a lot, trying to understand how to get better batteries, better propulsion systems, how we communicate with them, so there is a lot of development work going on. We are trying to push the technological edge, just to see how far we can go.”

Some unmanned vehicles are in operational use now, Johnson said. “There are some being used, I am sure, on the secret side of the house but it is not common across the board. But I can see that the future of underwater warfare is going to be lots of these little things in the ocean, doing the jobs that used to take big ships with lots of people to do.”

In relative terms, unmanned vehicles are less expensive than their crewed counterparts, and they may well deliver results beyond their purchase price, so smaller navies may see an advantage to acquiring unmanned systems, Johnson said. “Unmanned vehicles could do similar missions to multi-billion dollar nuclear powered or diesel submarines for a lot less money – less maintenance and fewer humans in the loop.”

Under the National Shipbuilding Procurement Strategy, the Royal Canadian Navy will be acquiring new generations of patrol vessels, supply ships and frigates. When they go to sea, a new underwater ISR capability will sail with them.

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