Quiet but deadly: diesel-electric submarines, the U.S. Navy's latest annoyance.

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The Navy in recent months has had to contend with several provoking episodes at sea--Iranian small boats speeding at its cruisers, destroyers and frigates; Russian bombers flying over its carriers; and Chinese subs shadowing its warships.

Hard-to-detect submarines--such as quiet, diesel-electric boats--are particularly vexing, Navy officials say. They contend that an undersea arms race already has begun in the western Pacific.

Nations there in recent years have begun to acquire stealthy diesel-electric submarines. Some of those nations, say Navy officials, could one day threaten U.S. access to strategic coastal areas of the world or interrupt the flow of commerce around the globe.

Although the Navy has the world's most technologically advanced fleet--including state-of-the-art nuclear attack submarines--officials acknowledge that these comparatively low-tech diesel-electric boats could give an enemy an asymmetric advantage.

"The beauty about a diesel submarine is that it has the potential to be far quieter than a nuclear submarine," says Guy Stitt, president of AMI International, a Bremerton, Wash.-based company specializing in naval market analysis. Diesel boats are propelled by batteries when submerged and move through the water by diesel engines when on the surface.

Once they have powered up their batteries, the submarines can sail to the bottom of coastal waters and remain undetected for days. Though they can't travel long distances or sail very quickly, advancements in technologies, such as air-independent propulsion and fuel cells, have allowed diesel submarines to extend theft operational ranges underwater.

But perhaps their best selling point is their relatively inexpensive price tags. The Russians have sold diesel submarines for as little as $200 million and the French have exported their Scorpene submarines for $300 million.

"It is within the scope of many, many countries to be able to afford them. They don't need a lot of them. They don't need to sail them very far, and they don't have to be particularly proficient with them," says Vice Adm. Samuel Locklear, commander of the Navy's Third Fleet, which prepares strike groups to deploy to the Pacific and the Middle East.

More than 39 nations possess diesel submarines. One of the latest tallies indicates a total of 377 ships in the world, says Richard Dorn, an analyst at AMI International. And there could be an uptick in the next few years.

With China continuing to increase the size of its navy, a number of neighboring nations also have begun to develop their undersea capabilities.

"There's a push on in Asia that really seems to be driven by China," says Stitt. Singapore, Malaysia and Indonesia all have closed deals on diesel submarines, and now Thailand is following suit.

Driving the market in part is Russia, which during the past 18 months has been aggressively selling ships, including its Kilo-class diesels.

"We've seen a huge increase in the number of sales that they're booking for Kilos, primarily motivated by the need for funds to strengthen their second tier shipbuilding groups," says Stitt.

Since the end of the Cold War, Russia has lost many of its secondary shipyard suppliers--the engine, pump and valve manufacturers, piping companies and the like. But Russia is attempting to revitalize those small companies.

"They're going out and making all these deals to sell submarines and ships and using those funds to reinvigorate the industry, which in turn will also benefit them in building up the Russian fleet," says Stitt.

Russia has exported 30 Kilos around the globe and 26 are still in active service. It will deliver two more submarines to Algeria by 2010, five to Venezuela by 2020, and six to Indonesia by 2018. China received its 12th and final Kilo last year.

The number of Kilos that are being sold is particularly concerning because many of the submarines are equipped with Klub anti-ship cruise missiles.

Some nations have a desire for regional hegemony and want to strengthen their influence in an area. That's most definitely the reason for President Hugo Chavez buying subs for Venezuela, says Stitt.

But for other nations, the reasons are less clear.

"There's a wide array of military assets you can buy, so why would you buy a diesel-electric submarine? As far as I know, it's not to protect your own port," says Locldear in an interview at Third Fleet headquarters perched atop Point Loma in San Diego.

That China's submarines are surfacing boldly near U.S. warships is a telltale sign of newer advanced technologies, such as acoustic tiles and cavitation-reducing propellers, that are being employed on the submarines, says Stitt.

China's new Song-class diesel submarines have tracked U.S. Navy ships operating in the seas near Japan and Taiwan. Last November, after China denied the USS Kitty Hawk's port call in Hong Kong at the last minute, a Chinese submarine shadowed the carrier as it entered the Taiwan Straits on its return voyage to Yokosuka, Japan. In the late fall of 2006, a Song-class submarine surfaced within torpedo range of the Kitty Hawk off the coast of Okinawa, Japan.

Despite the tensions, those episodes and the topic of submarines did not come up directly in conversations with Chinese officials in January, when the commander of Pacific Command, Adm. Timothy Keating, visited the nation.

"We watch them carefully. It's an area of warfare at which they're stretching a little bit," he told reporters during a breakfast meeting in Washington, D.C. "Their numbers of submarines are increasing. The capabilities resident in those submarines are not unimpressive. They're pretty good--we're better."

China's fleet of nuclear and diesel submarines includes 10 Song class, 12 Kilo class, one Yuan class and 32 Romeo class.

"We know that they are continually expanding their reach in what they view as their own areas of interest, and that their submarine force is vital to expanding that reach," says Locklear.

The proliferation of diesel submarines in the Pacific is one of the major factors behind the Navy's decision to move six submarines from the Atlantic Fleet to the Pacific Fleet, says Rear Adm. Joseph Walsh, commander of the Pacific Submarine Force. Because more than 140 diesel subs are within reach of critical "choke points" in the area, anti-submarine warfare is Pacific Fleet's top war-fighting priority, he adds.

The Navy saw its anti-submarine warfare skills diminish after the end of the Cold War. In those days, enemy Soviet nuclear submarines were noisy, and could be detected with passive sonar.

But modern-day diesel submarines are not as easily heard, particularly in regions of the seas where biological life and merchant shipping can camouflage their acoustic signatures. It is there, in the noisy waters of the littorals, where detecting submarines can be a cat-and-mouse game, Navy officials say.

Rear Adm. John Waickwicz, who was the head of the Naval Mine and Anti-Submarine Warfare Command until he retired in January, says the Navy is looking at anti-submarine warfare in new ways.

"When you talk about countries that have 30, 40, or 50 submarines, you can't wait until they're around you, because they're going to overwhelm you," he says.

Potential enemies have figured that to defeat the U.S. Navy, they must "go out and buy submarines, and buy mines," he says.

The mine and anti-submarine warfare command is calling for the deployment of a network of sonobuoys over a wide expanse of ocean to detect enemy submarines. But the project has been marred by technological and funding problems. The most significant hitch is that the data collected by the sensors takes too long to analyze, says Waickwicz. "You need to do it in real time to take action on it."

False alarm rates on many of the fleet's current detection technologies are too high, Waickwicz adds. That forces commanders to waste resources on non-existent threats.

Officials insist that the Navy's anti-submarine warfare capabilities are the best in the business, but they acknowledge that it will take some time to hone the skills to combat stealthy diesel submarines. Waickwicz says that training has improved in recent years, but some individual units are not adequately prepared for at-sea operations.

For example, some units have demonstrated sonar operator proficiency on simulations that are not sophisticated enough to replicate the real environment, which puts the sailors at a disadvantage when they conduct operations at sea, says Rear Adm. Frank Drennan, the new commander of the Naval Mine and Anti-Submarine Warfare Command.

"The requirements are still the same--they just have to work on them in a challenging environment so that operators are truly proficient when they go to sea," he says.

Hunting for quiet diesel submarines in the shallow waters of the littorals is akin to trying to identify the sound of a single car engine in the din of a major city, he says.

There are variations in the underwater topography, with sand bars, coral reefs and channels. Different depths of water and changing salinity and temperatures alter how sounds propagate. Marine life and merchant shipping also complicate the search by generating ambient noise.

The only technology that the Navy considers suitable for detecting and tracking diesel submarines is active sonar. It disperses signals out into the water where they bounce off of objects. Those echoes are captured by hydrophones and interpreted by sonar technicians.

Contrary to popular belief, sonar is not like radar, which gives complete visibility of "hits" in the air. What sonar technicians see is a screen that is filled with vertical lines representing echoes from objects in the water Discerning which line is a submarine and which one is a coral reef is a difficult and complex task, sailors say.

The Navy spent 40 years building a training range on the coast of Southern California--one of the most extensive in the world, officials say. Underwater sensors track ships' locations and record operations during exercises.

Because the water and ocean bottom conditions are representative of many areas around the world, the range is an ideal location for training strike groups in antisubmarine warfare, says Locklear.

But the Navy's training there has been curtailed by ongoing litigation over the harmful effects of active sonar on marine mammals.

Under a federal judge's ruling, ships were forbidden from using active sonar within 12 nautical miles of shore and had to steer clear of waters between the Santa Catalina and San Clemente islands during a joint training exercise in January for the Abraham Lincoln carrier strike group. Sightings of marine mammals at certain distances also prompted ships to take protective measures, such as powering down sonar or shutting the sensors off completely.

"We're not able to employ the sonar, given those restrictions, in a realistic manner, and it just makes it real tough to assess whether the fleet is proficient at using the technology," says Capt. Pete Tomczak, deputy director for training at Third Fleet.

The use of sonar by the Navy has been linked to mass marine mammal strandings on beaches in the Bahamas and the Canary Islands. Pending necropsy results, the death of a northern right whale dolphin that washed up Jan. 29 on the Navy's San Nicolas Island could be connected to sonar use.

Locklear says the Navy tries to balance its responsibility to protect the environment with its job to prepare sailors for war. He expresses concern that the judge's ruling, if extrapolated beyond Southern California, could hamper Navy training around the world.

"If this becomes precedence setting, I think it will be very difficult for the United States Navy," he says. "If there was a new technology on the horizon that made this irrelevant, we would be all over it. We just haven't found it yet."

With prospects of at-sea training diminishing, not only because of the litigation, but also as a result of rising fuel costs and other budget constraints, the Navy is searching for alternative ways to prepare its sailors for anti-submarine warfare.

One option is to rely on simulators, says Waickwicz. But he points out that current simulations in the Navy do not replicate sonar accurately.

"It's like playing 'Pong' in today's game world," he says. While the submarine forces have higher fidelity trainers, much of the rest of the fleet--especially surface ships--have sub-par simulations.

"Computer simulations can only go so far. There is still no substitute for at-sea practice against a real submarine," says Pacific Fleet's Walsh.

Because the U.S. Navy no longer operates diesel-electric submarines, it invites allied countries that own these boats to participate in exercises at Navy ranges on the east and west coasts.

The Swedish Navy's HMS Gotland collaborated most recently with various Navy commands in San Diego.

"It was very advantageous to have a diesel submarine crew for two years, to see how they thought, how they approached the issues to go against the ships," says Waickwicz. "It really opened our eyes to diesel submarines and how active sonar is what you have to have in the strike group."

The experience led to recent changes in the Navy's anti-submarine warfare doctrine and tactics.

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Dolphin's Brain Holds Secret to More Sophisticated Sonar

* SAN DIEGO -- The Navy's submarine-hunting sonars have been accused of harming marine mammals. It now appears that in the brains of one of those mammals--the bottlenose dolphin--could reside the secret to even more powerful underwater sensors.

By studying how the marine mammals interpret the signals they emit and receive in the water, researchers believe they can eventually develop a short range, high-resolution sonar to detect man-made objects in the noisy coastal waters and on the littered sea floor.

Dolphins, like bats, have a biological sonar system called echolocation. They produce ultrasonic sounds that reflect off objects to "see" the environment around them. Whales have similar abilities, but the bottlenose dolphin resides in regions of the ocean where the Navy wants to deploy advanced sonar: in the littorals, or coastal waters of the world.

The research is part of the Navy's Marine Mammal Program, which works under the auspices of the Space and Naval Warfare Systems Center San Diego.

Dolphins emit short echolocation clicks on the order of 100 microseconds in beam patterns that shift in frequencies, source levels and bandwidth. Those impulse signals range from 35 to 135 kilohertz in frequency and 80 to 100 kilohertz of bandwidth.

Dolphins are able to "tune" their sonar for various tasks. For example, in waters where snapping shrimp generate background noise--like sizzling bacon, to human ears--dolphins echolocate at higher frequencies that are optimal against the din.

"They can do things like steer the beam and change the beam width on a click-to-click basis," says Patrick Moore, a scientist and former head of the biosonar program office.

Scientists want to build sonars that can do the same thing, it's called environmentally adaptive sonar.

By virtue of being mobile when they echolocate, dolphins are able to perceive objects from multiple points of view.

"It swims around the target and looks at it from all these different aspects and creates an image, somehow," says Moore.

The researchers have attempted to mimic the biosonar by putting a multi-beam, mechanically scanned sonar on the nose of an unmanned underwater vehicle. As it moves through the water, the beams pick up multiple perspectives of an object, says Steve W. Martin, senior project engineer. Those snippets of data are then assembled for image analysis.

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But researchers don't know how dolphins "see" their environment using the information from those echolocation signals.

"We don't know if they form images," says Martin.

That signal processing capability in their brains is something the scientists are trying to unravel.

"We're dealing with an acoustic animal, not a visual animal. So it's hard for us as visual creatures to try to get inside the head of acoustic animals," says Moore.

But that's exactly what the researchers are planning to do. The scientists have received funding from the Office of Naval Research to do brain imaging work on echolocating dolphins to discover what parts of the brain are actively engaged in processing the echoes.

There's a theory that the dolphin has two hearing systems. One is devoted to communication sounds--the whistles and other noises they make in social settings. The scientists believe the other one is a passive system that has special timing considerations in a portion of the brain that becomes engaged when they begin to echolocate. When dolphins generate a click, they somehow know when the echo will return, and they can ignore other incoming signals until they receive the echo.

The scientists plan to experiment with the dolphins by using controlled electronic targets. They will place earphones on the jaw and the dolphin's forehead. When the dolphin produces a click, the scientists can manipulate the sound and present it back to the animal when they believe it would return from a target. By conducting the brain images, the scientists will begin finding clues into the dolphin's signal processing abilities.

The team works closely with the Navy's explosive ordnance disposal community, which employs dolphins as mine hunters. The EOD units also deploy UUVs, which have met much success clearing mines in the Middle East harbors. But the sea floor there is relatively uncluttered. Such robotic technologies do not fare so well in other regions where the ocean bottom is not as pristine, researchers say. In such cases, dolphins continue to prove their mettle with their echolocation abilities.

Progress has been made in biomimetic sonar. Martin built a biosonar that could detect underwater buried objects in a previous $4.5 million project funded by the Defense Advanced Research Projects Agency. But there was insufficient funding to take the prototype to the next level, says Moore. It's a recurring problem that frustrates the research team.

The scientists are conducting small business innovative research-funded work to apply the concept to small side-scan sonars for unmanned underwater vehicles.

"We'll get our technology to the fleet, one way or another," says Moore.

Undersea Combat Simulators Needed, Navy Says

* ORLANDO -- The Navy is worried about quiet diesel-electric submarines that are proliferating around the world and particularly in the western Pacific. But officials say the bigger challenge is training sailors to find and engage those submarines.

Rising fuel prices, restrictions on the use of sonar and less availability of ships are curtailing training, officials say.

In recent years, the Navy has sought to train sailors ashore in simulators. But virtual trainers do not accurately depict the near-shore environment in which the diesel submarines are operating, they assert. Nor do they replicate the sonar capabilities of current ships, particularly in the surface fleet.

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There is a great need for anti-submarine warfare training technologies, says Vice Adm. John Harvey, Jr., deputy chief of naval operations for manpower, personnel, training and education.

Replicating the near shore undersea environment in the virtual world has been a particular challenge for simulation experts. Not only is the topography of the ocean floor varied with reefs, volcanoes, sand bars, and other elements, but also the littoral waters are often teeming with activity from marine biological life and merchant shipping. All of that generates noise and alters how sound propagates through the water. To capture those factors in a model would take time and resources, industry experts say.

Current simulation projects do not consider anti-submarine warfare a top priority. But sortie companies see a potential market. Delex Systems Inc., a training, intelligence and information technology company based in Vienna, Va., has modeled the ocean floor in several previous projects, says Edmund Driscoll II, president:.

"We know that detailed simulation is what really matters in a learning environment," he says.

The company has developed a software architecture, called BattleNet 360, that can teach sailors on an individual or group basis how to operate various Navy systems. It is designed to sit on top of existing hardware and can employ databases of realistic models into war fighting scenarios.

"It's all set up and ready to go for submarine sonar acoustic models," says Brian Burke, program manager of the company's tactics and simulation group.

Navy to Deploy Robotic Sub Hunters

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* WASHINGTON NAVY YARD -- The Navy this fall plans to test new unmanned vehicles and sensors that were specially designed to detect diesel-electric submarines in coastal waters.

The technologies are intended for deployment aboard the littoral combat ship, the Navy's new class of surface combatants.

The anti-submarine warfare package includes the unmanned Fire Scout vertical take-off aircraft, two surface vehicles and two underwater multi-mission vehicles. A manned MH-60R helicopter also will be part of the operation.

The aircraft and water vessels will tow acoustic sensors capable of discerning quiet diesel-electric submarines in the cluttered underwater environment, says Capt. Michael Good, program manager of the LCS mission modules.

The unmanned systems will allow the Navy to hunt those submarines without putting ships in range of torpedoes.

"We don't want to be in a knife fight in a phone booth," says Good.

The remote multi-mission vehicle will chug through the water like a snorkeling submarine. It will release one of two medium-frequency sonar arrays that will emit an acoustic signal or listen for returns as they are towed along.

The plan is for the two RMMVs to work in concert as a bi-static acoustic detection system. The first vehicle will deploy an active sonar array and the second will tow a hydrophone array.

Likewise, the unmanned surface vehicles will carry one of two payloads, an active low-frequency sonar, called the multi-static off-board source, or a hydrophone towed array. The USV also can deploy a modified dipping sonar typically operated from helicopters. The Navy is looking at several variants, including Raytheon's AN/AQS-22 airborne low-frequency sonar and the HELRAS DS-100 made by L3 Communications.

"We're looking at both possibilities down the road," says Good.

Armed with the MK-54 torpedo, the manned Sikorsky MH-60R helicopter will act as a "pouncer" to attack the threat submarine after detections are made by the sensor payloads on the unmanned vehicles, he says.

Outfitted with an electro-optical infrared sensor, Northrop Grumman's Fire Scout rotorcraft will perform as a communications relay platform to extend the distance that the unmanned vehicles can operate away from the LCS. In the future, it could be equipped with other anti-submarine warfare sensors, says Good.

The Navy plans to deploy two detachments of sailors aboard LCS--one for the mission modules and one for the aircraft. The mission modules will have a detachment of 15 sailors. The composite aircraft detachment will be crewed at 23 sailors.

Of the planned 64 mission packages, 24 are for mine warfare, 24 are for surface warfare and 16 are for ASW. The mine warfare packages are the first priority for the Navy, followed by the surface warfare packages to address the swarming small boat threat. Antisubmarine warfare is the third priority mainly because the Navy has a fair amount of ASW capability aboard its ships, submarines and aircraft, says Good.

"We don't need to compete with a DDG-51 destroyer or a P-3 aircraft or a submarine. What we want to do is complement them so that the Navy gets an overall holistic capability for anti-submarine warfare," he says.

The first ASW mission package, set for delivery in September, will not have the RMMV and its two towed systems. The second package, whose delivery date has not yet been determined, will include the underwater vehicle and the towed systems.

"We're very eager to get the integration work done on the unmanned surface vehicles and get them to sea," says Good. Testing will be completed this spring.

This fall, Good plans to evaluate the full mission package at the Atlantic Undersea Test and Evaluation Center, an instrumented range in the Bahamas. Because the range isn't large enough or deep enough to fully test the systems at the lower frequencies, he is also working on locations at sea where the use of active sonar will be permitted.

The requirement for the LCS anti-submarine warfare package was to be able to hunt quiet diesel submarines in the littorals. But some of these systems, particularly those employing lower frequencies, will work in deep water, says Good. His intention is to operate as many of the systems in deeper ocean to evaluate potential applications for anti-submarine warfare.

But first he has to find a way to set sail with the technologies. With LCS delayed and facing an uncertain future, he is working to identify a substitute vessel that could take the mission package to sea for testing.

"I just have to be a little more creative in how I get to sea," says Good, who is contemplating options including barges.

The ASW mission module detachment sailors are eager to get their hands on the technology, he adds. After having an opportunity to ride on one of the unmanned surface vehicles in Baltimore, the sailors expressed tremendous excitement.

"They were pretty impressed with how these boats perform," he recalls. "They are really looking forward to being able to drive them from LCS and go conduct anti-submarine warfare with them."