Tidal Rip

submarine find the best place to hide from enemy detection platforms. In addition, this information can be applied in interpreting noises detected coming through the water from an enemy submarine in order to help determine the hostile sound source’s likely bearing, range, depth, and even its course and speed.

Sound short: a failure of a submarine’s quieting (see above), in which noise from within the sub is transmitted into the surrounding sea. Sound shorts are very serious matters, since they can ruin stealth and lead to detection and attack by an enemy. A submarine’s sonars are able to check it for sound shorts, and if any are found the crew will give a priority to correcting them. Often this can be done by repairing or replacing faulty quieting gear, or if necessary by switching off the machinery that is causing the unwanted noise — although the latter may put the submarine at a grave tactical disadvantage, if the errant machinery is needed for full war-fighting readiness.

SSGN: a type of nuclear submarine designed or adapted for the primary purpose of launching cruise missiles, which tend to follow a level flight path through the air to their target. An SSGN is distinct from an SSBN, which launches strategic (hydrogen-bomb) ballistic missiles, following a very high “lobbing” trajectory that leaves and then reenters earth’s atmosphere. Because cruise missiles tend to be smaller than ballistic missiles, an SSGN is able to carry a larger number of separate missiles than an SSBN of the same overall size. Note, however, that since ballistic missiles are typically “MIRVed” — i.e., equipped with multiple independently targeted reentry vehicles — the total number of warheads on an SSBN and SSGN may be comparable; also, an SSBN’s ballistic missiles can be equipped with high-explosive warheads instead of nuclear warheads. (A fast-attack submarine, or SSN, can be thought of as serving as a part-time SSGN, to the extent that some SSN classes have vertical launching systems for cruise missiles and/or are able to fire cruise missiles through their torpedo tubes.)

Subtropical convergence: the area in the South Atlantic Ocean where currents of warmer water from near the equator meet and clash with other currents of colder water from near the Antarctic. The result is a zone of unpredictable and confusing sonar conditions. The subtropical convergence does not extend across the South Atlantic as a well-defined straight line, but rather is a broad area that snakes across different latitudes in different places and varies over time.

Thermocline: the region of the sea in which temperature gradually declines with depth. Typically the thermocline begins at a few hundred feet and extends down to a few thousand feet, where the bottom isothermal zone is reached (see above).

TMA: Target Motion Analysis. The use of data on an enemy vessel’s position over time relative to one’s own ship in order to derive a complete firing solution (see above). TMA by passive sonar alone, using only relative bearings to the target over time — and instant ranging data where available (see above) — is very important in undersea warfare.

Tonal: sound given off at a single frequency, similar to a pure musical “tone” or note. Tonals are important in detecting and identifying passive sonar contacts. This is because different equipment — and thus different classes of friendly and enemy submarines carrying that equipment — have unique sets of frequencies at which they emit tonals. One example of the source of a tonal might be an item of equipment that rotates at a particular rate per second, such as a turbogenerator, a reactor cooling-water circulation pump, or even a food blender in the ship’s galley (kitchen).

Towed array: a long cable equipped with hydrophones (see above) trailed behind a submarine. Towed arrays can also be used by surface warships. The towed array has two advantages: Because it lies behind the submarine’s stern, aft of self-noise from the propulsion plant, it is able to listen in directions where the submarine’s on-hull sonars are “blind.” Also, because the towed array is very long (as much as a mile), it is able to detect very long-wavelength (very low-frequency) sounds — which smaller, on-hull, hydrophone arrays may miss completely. Recently, active towed arrays are being introduced. These are able to “ping” as well as listen at very low frequencies, which has significant tactical advantages in some sonar and terrain conditions. The next planned advance is a towed array with three or more separate parallel lines in which the individual hydrophones use fiber-optic coils and lasers. Tiny changes in the behavior of the laser light will result when the coils are influenced by sound waves in the surrounding ocean. Analysis of such data promises to greatly increase the sensitivity of the array to the presence of enemy submarines and other targets. (When not in use, the towed array is retracted by winches in the submarine’s hull. Towed arrays often need to be retracted if the submarine is in close proximity to bottom terrain or surface shipping, or if the submarine intends to move at high speed.)

Virginia class: the latest class of nuclear-propelled fast-attack submarines (SSNs) being constructed for the United States Navy, to follow the Seawolf class. The first, the USS Virginia, is due to be commissioned in 2004. (Post — Cold War, some SSNs have been named for states, since construction of Ohio-class Trident missile “boomers” has been halted.)

Wide-aperture array: a sonar system introduced with the USS Seawolf in the mid-1990s, distinct from and in addition to the bow sphere, towed arrays, and forward hull array of the Cold War’s Los Angeles—class SSNs. Each submarine so equipped actually has two wide-aperture arrays, one along each side of the hull. Each array consists of three separate rectangular hydrophone complexes. Powerful signal-processing algorithms allow sophisticated analysis of incoming passive sonar data. This includes instant ranging (see above).

ACKNOWLEDGMENTS

The research and professional assistance that form the nonfiction technical underpinnings of Tidal Rip are a direct outgrowth and continuation of those for Crush Depth, Thunder in the Deep, and Deep Sound Channel. First I want to thank my formal manuscript readers: Captain Melville Lyman, U.S. Navy (ret.), commanding officer of several SSBN strategic missile submarines, and now director for special weapons safety and surety at the Johns Hopkins Applied Physics Laboratory; Commander Jonathan Powis, Royal Navy, who was navigator on the fast-attack submarine HMS Conqueror during the Falklands crisis, and who subsequently commanded three different British submarines; Lieutenant Commander Jules Verne Steinhauer, USNR (ret.), diesel-boat veteran, and naval aviation submarine liaison in the early Cold War; retired Senior Chief Bill Begin, veteran of many “boomer” strategic deterrent patrols; and Peter Petersen, who served in the German Navy’s U-518 in World War II. I also want to thank two Navy SEALs, Warrant Officer Bill Pozzi and Commander Jim Ostach, for their feedback, support, and friendship.

A number of other navy people gave valuable guidance: George Graveson, Jim Hay, and Ray Woolrich, all retired U.S. Navy captains, former submarine skippers, and active in the Naval Submarine League; Ralph Slane, vice-president of the New York Council of the Navy League of the United States, and docent of the Intrepid Museum; Ann Hassinger, research librarian at the U.S. Naval Institute; Richard Rosenblatt, M.D., formerly a medical consultant to the U.S. Navy; and Commander Rick Dau, USN (ret.), operations director of the Naval Submarine League.

Additional submariners and military contractors deserve acknowledgment. They are too many to name here, but standing out in my mind are pivotal conversations with Commander (now Captain) Mike Connor, at the time CO of USS Seawolf, and with the late Captain Ned Beach, USN (ret.), brilliant writer and one