Robots, Sensors Key To Future Anti-Mine Warfare Plans

Signal, May 2008 by Kenyon, Henry S

Autonomous systems and new types of sonar seek to detect, neutralize ship killers before they strike.

The U.S. Navy is working hard to keep humans out of mine-fields. The service is developing a host of autonomous and air-deployed capabilities to detect and neutralize mines at sea and in littoral zones. These systems, which are now entering service, will reduce and ultimately eliminate the need for divers to disarm and destroy mines in person.

The new technologies are part of an ongoing realignment of the Navy's minehunting capabilities, says Thomas Swean, a team leader with the Office of Naval Research's (ONR's) mine countermeasures program in Washington, D.C. For the past several years, the Navy has been restructuring its Mine Countermeasures (MCM) Warfare Command, which is in the process of relocating from Corpus Christi, Texas, to San Diego.

Traditionally, Navy minesweepers were assigned to Navy task forces on an as-needed basis, but the service is shifting its requirements and installing systems directly on warships such as destroyers and frigates, Swean explains. Navy acquisitions programs currently underway include an initial group of organic MCM capabilities now beginning to enter service, such as helicopter and unmanned robotic vehicle-based capabilities.

"Mine hunting is a very dangerous job," says Swean. He notes that mine disposal traditionally involved Navy divers manually disarming or attaching demolition charges to mines. The thrust of the Navy's research and development effort is to remove humans from this hazardous environment. Swean states that another goal is to accelerate the process of detecting, locating and neutralizing mines.

Unmanned systems are already beginning to assist with accelerated mine detection and clearance. The ONR oversees the Navy's autonomous underwater vehicle (AUV) research and development programs, several of which are almost ready for deployment, Swean says.

The battlespace preparation AUV (BPAUV), a 21-inch diameter AUV currently in the acquisition phase, is designed for launch from a 21-inch torpedo tube. This AUV is equipped with a fleet-class, high-definition sonar and has a 12- to 13-hour operational endurance, making it capable of surveying large areas of ocean.

Another capability entering service is the autonomous unmanned surface vehicle sweep. This robot boat is equipped with a magnetic and acoustic detection/sweeping system. Swean adds that the automated sweep will be installed on littoral combat ships beginning this November.

The Navy also is actively studying new classes of sonar to detect mines. "It's the best sensor you can put in the water," he says of sonar. The ONR has developed a synthetic aperture sonar that is being installed on a new class of 12-inch-diameter AUVs. Swean maintains that synthetic aperture sonar is groundbreaking because of its increased resolution and range, both of which are critical features for detecting mines and other undersea weapons.

According to Swean, the greatest sonar development is low frequency broadband sonar. This sensor system transmits and receives sound signals at very low bandwidths. It can provide warfighters with precise estimates of a target ship's size and shape, greatly enhancing detection and classification. This technology is what he refers to as a "game changer." For mine detection, the sonar makes it possible for Navy units to acquire, detect and classify mines in a single pass. The new sonar is scheduled to be installed on an AUV platform and ready for Navy acquisition by 2013.

The Navy's AUV technology was developed to search, classify and neutralize mines. The software and sonar systems necessary for reacquisition are now mature enough to begin entering service. Swean explains that traditionally, a search will detect an object on the first sweep and then classify it on subsequent sweeps. The ONR is now focusing on developing an autonomous capability that will return to an identified mine and destroy it. This autonomous detection and neutralization program is in its early stages. It is scheduled to move to an acquisition phase by fiscal year 2011.

ONR scientists also are developing techniques that will permit different autonomous systems such as AUVs to operate together, rather than operating sequentially. Swean shares that autonomous systems will be able to cue each other and function in unison, greatly accelerating minefield clearance.

Successful mine detection depends on the environment, water clarity and bottom clutter. Mines tethered on or near the bottom are difficult to detect in areas with coral reefs, rocks or other mine-sized debris on the bottom. Swean notes that detecting mines under such conditions can be time consuming. Although the specific durations are classified, he shares that clearance time is tied to bottom conditions, the size of the minefield and available resources. The Navy has several technologies in its research and development pipeline designed to decrease detection and clearance times by an order of magnitude, he says.