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.
The first Chinese Kilo submarines had been bought from Russia in 1993 and delivered in February 1995. The Chinese had planned to buy up to fifteen of these powerful diesel submarines and had hoped that they would be able to build five more themselves, under license from Russia.
This particular submarine had excellent equipment, with the exception of her passive sonar outfit. That was the problem with all Russian submarines, as its captain knew. The Russians could not make a decent passive submarine sonar - at least not one that his country would be allowed to buy.
And that was a problem. At any given moment, there might be an American Los Angeles class submarine sneaking up on his position, and he would never know it until it was too late.
The captain of the Chinese submarine wasn't too worried about it, though. His was the lead ship of three. Below the waves, his Kilo was working in tandem with an older Romeo class diesel submarine. Above them, Jinan, a Luda class destroyer, patrolled the surface. Their mission was to hunt down and destroy any American ships and submarines. In addition, there was another Kilo well off to the side-not part of his task force, but it could provide assistance if he needed it.
The captain of the Kilo welcomed Jinan more than he did the Romeo. For one thing, the destroyer's two turbines were loud, which would hopefully distract any enemy's sonar from any noises his Kilo might make. Even more important, however, Jinan, like all Luda type II destroyers, carried two French ASW helicopters. Those would be very useful if the Kilo needed help while engaging an American submarine.
As pleased as the Kilo's captain was with the surface ship, he was equally displeased with the Romeo. It was an old attack submarine that had been reactivated from the naval reserve, and, in his opinion, it was more of a threat to his own submarine than it was to the enemy. It was too noisy, for one thing. That could be desirable when the noise came from the surface, but down below it would only serve to alert the Americans to the presence of one or more Chinese submarines in the area.
Worse, the farther he tried to get from the Romeo, the more it tried to stay close to him. The Romeo captain was no fool. He knew he stood a better chance under the protection of the Kilo than he did on his own.
Assuming, that is, that the Kilo captain didn't sink the Romeo himself.
Back on board Cheyenne, sonar was trying to reac-quire contact. Mack had gone back to 247 feet to continue the search, while at the same time maintaining copy over the floating wire.
In the control room, Mack was looking at the BSY-1 fire-control console, which he liked to keep online for himself. 'Sonar, conn, have you regained contact on Master 24?'
'Conn, sonar, we're working on a possible contact,' the sonar supervisor said, 'but I'm not sure it's the same convergence zone one. This one may be a surface ship, Master 24 was tentatively classified as a submerged submarine,'
Several minutes later, the sonar supervisor reported that he had not one contact, but two, one Romeo submarine and one Luda destroyer, both bearing 020. They were both given new Master Numbers, designated Masters 25 and 26 respectively, since the sonar supervisor was not sure if either one was Master 24. Reconstruction would have to sort it out later. Without hesitating, the OOD ordered his section fire-control tracking party manned, Mack went to the sonar room.
'Good job,' Mack said, unaware that they had failed to detect the Kilo that was in the area of Masters 25 and 26. 'Anything else out there?'
'Not that we can tell yet, Captain,' the sonar supervisor said, 'but those two contacts are loud. We can hear them aurally, so there could be more ships operating in the area.'
Mack left the sonar room and went back to the control room. The BSY-1 operators had a rough solution on range, about 30,000 yards.
At Cheyenne's current speed of ten knots. Mack would soon be within range to launch his Mk 48 ADCAPs at the Chinese contacts. When he got closer, he would slow. No need as yet for long-range shots. Cheyenne was currently running with the TB-23 towed-array fully deployed and, with the OOD's maneuvers, the section fire-control tracking party at the BSY-1 computers was getting better and better solutions on the Chinese destroyer and submarine.
'Conn, sonar, the TB-23 just picked up a helicopter overhead,' the sonar supervisor announced. 'Probably flying from the Chinese destroyer.'
'Take her down fast, to five hundred feet!' Mack ordered the OOD. This was another helo 'Sierra' addition to his patrol report.
Throughout Cheyenne, sailors grabbed for whatever they could as the submarine headed down at standard speed with a twenty-degree down angle. The diving officer, helmsman, and planesman had all buckled their seat belts as soon as they heard 'take her down fast.'
Above them, the Chinese Z-9A helo hovered and began to tower its powerful French HS-12 dipping sonar via the hydraulic winch. The winch was touted to be 'high speed,' but it didn't seem fast enough for the helo pilot as it slowly lowered the HS-12 toward the water.
'Conn, sonar, we just received a sonar pulse from the helicopter's dipping sonar. It's a French type, HS-12- the same kind they sold to China. The transmission came from the opposite direction of the Romeo. I don't think they could have detected us, sir. Signal level of the pulse was low.' Which probably meant the helo was quite a ways off or else it hadn't dipped its sonar beneath the layer.
Mack acknowledged for the OOD. 'Very well, sonar, we have it out here on the WLR-9 as well,' he said. 'Were we able to pick up any other information from the transmission?'
'Sonar, conn, negative,' the sonar supervisor answered. 'It wasn't a very strong pulse. Let's hope she ran out of batteries.'
Mack smiled at the joke. Unlike the communicator's earlier gaffe, this comment was well timed, and helped to ease the tension slightly.
One hour and fifteen minutes later Cheyenne had closed to within 20,000 yards of her targets, Masters 25 and 26. Mack ordered battle stations manned.
A few minutes later the helo was active again. The WLR-9's acoustic intercept receiver at the conn picked that one up also, even though it was near the baffles.
'Conn, sonar, that was a loud one, sir,' the sonar supervisor said.
Mack smiled. 'She must have recharged, ne saia, in a deadpan voice. 'Designate the helo Master 27.'
'Conn, sonar, she got us on that one, sir-but that's not all she painted! Captain, we've got another submarine out there, a Kilo class, one six-bladed screw, making turns for ten knots. It's bearing 025, near the same bearing as
