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

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."