SSN - Tom Clancy [24]
His lighthearted joke helped to ease the tension slightly. The assembled officers had a few questions. They discussed their options, and then Mack dismissed them to return to their duties. When he had returned to the conn, he used the 1MC to inform the crew of their new mission. From there on out, Cheyenne would use sound-powered phones instead of general announcing systems.
Forty-five minutes later Cheyenne once again went to periscope depth. The seas had abated somewhat, but copying SSIXS required the use of the long, multi-purpose communications mast to preclude the loss of synch caused by waves slapping over the Type 18 periscope communications antenna.
Mack stayed at that depth just long enough to receive preliminary Tomahawk targeting data. This information, which they would confirm when they got closer to their launch position, would be fed to their cruise missiles prior to launching the Tomahawks. Mack hoped the weather would be better north of the Spratlys.
When the data transfer was complete, Cheyenne detached from the Independence Battle Group without report and proceeded on her own. Mack had enjoyed having the carrier nearby for backup and air defense, but now Cheyenne was going back to doing what she did best: operating on her own, sneaking up on the enemy, and blowing them to hell.
Three hundred fifty miles southwest of Cuarteron Reef, running at four hundred twenty-five feet, Cheyenne picked up her first contact. Mack was in the sonar room.
"Captain," the sonar supervisor reported, "we have a sonar contact bearing 020 on the spherical array. The contact's intermittent, so I think we're receiving the sound source via a convergence zone. We pick her up loud and clear, then we lose her and don't hear anything for a while."
While normal sound traveled through water in waves that gave at least some predictability, there were some areas in which sound waves were turned up toward the surface and then often bounced back into the sea. These were called convergence zones, and they could allow sonar to detect these sound waves at far greater ranges than would otherwise be possible. If the water was deep enough and the sound velocity excess was present at depth, these zones commonly occurred about every thirty miles. In a way, the ray paths of the acoustic energy were much like AM radio transmissions, which could travel in a straight line, then bounce off the ground and up into the atmosphere, and then come back to earth. This allowed man rm, AM rrequencies 10 oroaucasi muuii though beyond their immediate range they could be picked up only in pockets and were more affected by weather.
"My guess," the sonar supervisor added, "is that it's in the second convergence zone from us." That would put the signal's source at a range of more than sixty nautical miles, or 120,000 yards.
"Keep an eye on that contact," Mack said. If the sonar supervisor was right and Cheyenne's operators had indeed heard their sonar contact through a convergence zone, then the signal's source was far out of Cheyenne's weapons range. It also meant that the thermal gradients in the deeper waters of the South China Sea had not been eroded by the storms. But if the sonar supervisor was wrong, Cheyenne could be in for some very dangerous close combat.
Sixty-three miles away, 200 feet below the surface of the South China Sea, crept one of the newest additions to the Chinese fleet, and one of China's best submarine captains. The Chinese Kilo submarine had been in service for less than two years and had made its crew very proud.
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