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In a new age of ultra-quiet undersea acoustics, it's high time for the U.S. Navy to revitalize a signature Cold War capability.
In early 1981, a ready-alert P-3C Orion launched from Naval Air Station Bermuda with a crew of 12 officers and enlisted men. An hour earlier the crew had been comfortably asleep as their 24-hour-alert shift was winding down. Now they pulled themselves together as their Orion clawed for altitude, arcing northeast toward the vastness of the North Atlantic Ocean. During the scramble to get airborne there had only been time for a hasty briefing, but they understood the sudden urgency: A Soviet submarine was nearby.
The mission commander, Lieutenant Frederick "Buzz" Lineburg, faced a challenging task. He knew the submarine was transiting from the north, and he knew its last estimated position. As Buzz studied his chart, he realized that his quarry could be hiding anywhere within several thousand square miles of ocean. An area of that size was too large for "direct-path" search tactics, which exploit one of several acoustic-ray paths that sound can follow through water. Instead, by capitalizing on the target's relatively loud acoustic signature, Buzz elected to employ search tactics optimized for "convergence-zone" (CZ) ray paths, which can propagate much farther through water. Thus, with only 1 aircraft and 16 passive sonobuoys, Buzz and his crew were able to search several thousand square miles of ocean with an acceptable probability of detection-a capability known in the air antisubmarine warfare (ASW) community as wide-area ASW search.
Wide-area ASW search is a critical warfighting capability.1 During the Cold War, NATO forces leveraged their technological edge to develop sensors, operators, and tactics, techniques, and procedures (TTPs) capable of detecting and tracking Soviet submarines. Many of these sensors, contained in towed arrays and sonobuoys, were passive systems that listened for the telltale sounds of a submarine without betraying the presence of their host platforms. NATO's ASW forces effectively parlayed these sensors and TTPs into an ability to find Soviet submarines at sea, providing their commanders with important situational knowledge during the heightened military tensions between East and West.
For over a quarter century, however, the sharp decline in submarine acoustic-source levels has been well documented (see Figure 1). When combined with a...