(9 of 10)
As they pass through the ocean depths, submarines invariably give off "scars"—traces of heat and turbulence caused by the ship's passage through the waters. The U.S. employs ultrasensitive infra-red devices in satellites and planes to look down into the oceans and detect the scars. Submarines also give off what Navymen call "an electronic signature" that, like a human fingerprint, is unique. The signature is the sum total of the sub's sounds—the beat of its screw, thump of its pumps, rustle of its wake. To detect those signatures, the U.S. uses a variety of acute listening devices, including two networks of sonar cables, called Caesar and Sosus, that are placed in the ocean depths in areas frequented by Soviet subs. U.S. planes, destroyers and hunter-killer subs also use sonar devices to trace Soviet subs. Through such systems, the U.S. Navy is able to track
Soviet subs with uncanny accuracy throughout most of the world's waters.
Sub Hunting. A sonar operator needs a highly trained ear to sort out the sounds of the sea. Apart from a sub's noises, the sea is full of other sounds, a syncopated symphony of crackling shrimp, clucking sea robins and grunting whales; there is even the engine-like throb of an unknown sea animal that Navymen call the "130-r.p.h. fish." Once the various sounds have been sorted out, the American sub hunters flash the details of the sub's signature to a Navy base in the U.S., where a computer has memorized the signatures of the vast majority of the Soviet submarines. Within seconds, the computer flashes back the name and description of the sub.
On some occasions, the U.S. hunters pounce on the Soviet sub in what the Navy euphemistically calls "informal exercises." The object of the chase is to give the Soviet submarines a healthy respect for the capabilities of the U.S. Navy's ASW (Antisubmarine Warfare) forces. In a duel reminiscent of the fictional shoot-out in The Bedford Incident, a U.S. destroyer locks on the enemy boat and tracks his every move. Sometimes, to impress on the Soviets the futility of their plight, an American skipper will play The Volga Boatmen over and over again on his destroyer's underwater sound system until the ears of the Russian sonar operator are numbed by the noise and the Soviet sub is finally forced to surface.
The Russians lag well behind the U.S. in submarine warfare. One reason is that their ships are slower (about 25 knots submerged), make more noise and cannot dive so deeply as U.S. subs, and are thus easier to detect. But the Soviets are continually trying to improve. They are using their big hydrographic fleet to learn more about the sea environment and to find hiding places in the canyons of the ocean for future gen erations of deep-diving submarines. The U.S. Navy tries to keep up with even the most minor changes in the development and deployment of Soviet subs. One reason that Pueblo was cruising off Wonsan was to check on a report that, because of ice in Vladivostok, the Soviets had temporarily switched their Pacific sub base to Wonsan and the nearby island of Mayang-Do. The U.S. is also equipping its nuclear submarines with silent pumps and heat-dispersal systems so that the Soviets will not be able to use infra-red detection systems to locate the scars of American subs.