NEWPORT, R.I. – U.S. military researchers are asking two U.S. defense contractors to develop bistatic sonar for anti-submarine warfare (ASW) that teams manned and unmanned submarines and capitalizes on the benefits of active sonar without compromising the stealth of U.S. attack submarines.
Officials of the U.S. Naval Undersea Warfare Center (NUWC) in Newport, R.I., has announced a $4.6 million contract to the BAE Systems Electronic Systems segment in Merrimack, N.H.; and a $4.7 million contract to Applied Physical Sciences Corp. in Groton, Conn., for the Mobile Offboard Command and Control and Approach (MOCCA) program.
NUWC awarded the contracts in February on behalf of the U.S. Defense Advanced Research Projects Agency (DARPA) in Arlington, Va. MOCCA seeks to enable manned Navy submarines to use active sonar pings from nearby unmanned underwater vehicles (UUVs) to detect and track enemy submarines at long ranges without giving away their presence to potentially hostile vessels.
The project seeks to use UUVs as pingers and manned fast attack submarines as listeners to conceal the presence of the manned attack sub. Using this technology the manned submarine could detect and target enemy submarines based on sonar returns from the UUV active sonar pingers.
Traditional active sonar bounces sound waves off of submarines, surface warships, and other objects for detection and tracking. The problem with active sonar, however, is it’s like shining a flashlight in a darkened room: it can find objects effectively, but gives away its presence and forfeits any pretense of stealth.
Passive sonar, on the other hand, simply listens for sounds from enemy submarines or surface ships. It’s not as effective or as efficient as active sonar, but it preserves stealth and can keep the submarine’s presence secret from the enemy.
As long as attack submarine crews have precise knowledge of the position of the pinging UUV, then they can detect the presence of enemy submarines based on sonar sound returns, and track its movements with accuracy. Moreover, attack submarines can keep their locations secret.
The DARPA MOCCA program seeks active sonar solutions that will mitigate the limits of passive submarine sonar sensors, researchers say. The objective is to achieve significant standoff detection and tracking range by using an active sonar projector deployed offboard a submarine and onboard a UUV.
The submarine will need the ability to coordinate the operational functions of the supporting UUV. Thus, the program also must demonstrate reliable clandestine communications between the host submarine and supporting UUV without sacrificing submarine stealth.
The first phase will last for 15 months and will involve preliminary designs for innovative sonar and communications concepts, as well as subsystem prototype demonstrations to validate design approaches.
The MOCCA program has two key technical challenges: an active sonar pinger small enough for UUVs, as well as signal processing; and a secure communications link to enable the host submarine to control the UUV at significant distances.
DARPA researchers are asking the two companies to build an active sonar with an active sonar projector small enough for UUV operations; and bistatic active sonar processing. This will involve developing high-output transducer materials, and a sonar projector that is as energy-efficient as possible.
In addition to a small power-efficient sonar projector, or pinger, researchers are asking the two companies to develop bistatic sonar processing advancements in reverberation and clutter rejection as well as precision localization capability. The host UUV will is expected to be no larger than 21 inches in diameter.