SSN - Страница 4

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At 1100 on 12 August, just ten hours after leaving San Diego, the OOD ordered Cheyenne to slow to one-third. Exactly eleven minutes later the sonar room came alive as Cheyenne slowed and her course was changed toward the north.

"Tonal contact, center bearing 187 on the end-fire beam," called one of the young sonar operators. The consoles, which looked like computer screens with green lines running through them, were often the sonar operator's most important ally.

An instant later the sonar supervisor, who had been paying close attention to the goings-on in this important center of the submarine, called to the captain, "Conn, sonar, we have a possible submarine contact bearing 187. We're only receiving blade rate information so far."

Mack entered the sonar room, joining the five other men already there-including the sonar supervisor and the sonar officer. Everyone in the room knew that there was the possibility of encountering a Chinese submarine, but also knew it was highly unlikely. Chinese naval vessels rarely ventured this far away from home waters. This was especially true of the Chinese submarine fleet, which consisted largely of older-model diesel boats with just a few very noisy nuclear-powered attack submarines of the Han class.

If there was a Chinese submarine patrolling off the West Coast of the United States, however, Mack was fairly sure that it would have to be a Han class. Naval intelligence reports had repeatedly explained that only one type of submarine was capable of travelling this far from Chinese home waters and operating-without surfacing-for an extended period of time. That type was a nuclear submarine, and the only Chinese SSN currently in service was the Han class.

Captain Mackey was, as were all experienced submariners, at least slightly familiar with the Han class of submarine. In addition, when word was passed of a possible war with China, the intelligence officer assigned to SubRon 11 from SubGroup 5 had quickly prepared a brief report of what was known of the Han class in the U.S. intelligence community. According to that report, construction of the Han class had stopped after only five submarines due to extremely high internal radiation levels, and all of those were currently in service with the Chinese navy. They carried the pennant numbers 401, 402, 403, 404, and 405 painted on their sail. One of the class had, of course, been destroyed earlier that month by a U.S. SSN. Naval intelligence was still unsure which number it was, but they reported that it was probably number 402, the second of the class. They were assuming this because it had been tracked since leaving Ningbo Naval Base in China's East Sea Fleet four days prior to the actions involving Nimitz.

The torpedo complement fitted to the Han class was reported to be a mix of the older straight-running types as well as some of the newer Russian homing varieties. According to the reports, numbers 401 and 402 carried only torpedoes, but the last three submarines of the class, numbers 403 to 405, carried the Ying Ji. Also known as the Eagle Strike, this antishipping missile was a sea skimmer and caused great concern in the eyes of naval commanders. The most recent intelligence reports stated that while these missiles could be a significant threat to warships, the submarine needed to surface in order to launch them. And submarine commanders knew all too well that a surfaced submarine was an easy target.

Unlike the USS Seawolf, Cheyenne did not have a wide aperture array, or WAA, so she would have to triangulate the position of her passive sonar contacts in order to determine their exact bearing, speed, and range. The ship maneuvers to accomplish this would have to be done very quietly, especially if the contact, TKVW designated Master 1, was a direct-path contact. But it was a painfully slow process.

"Captain," the sonar supervisor said, "it's possible the submarine was tracking us but lost us when we slowed. With these convergence zones out here in deep water, it could be in excess of 75,000 yards away. My guess is that he thinks we passed him, and based on its blade rate, is running full speed in an attempt to catch up with us and regain contact."

That was a good guess, Mack thought, but it was still just a guess. He wanted something more than that. Proceeding to the conn, he ordered the OOD to station the section fire-control tracking party so the BSY-1 computers could be used to determine the solution on the target. The OOD would maneuver the submarine in order to change the bearings received by the towed arrays.

Mack also ordered the OOD to house the TB-16 towed array and deploy the TB-23 towed-array. Unlike the 240 feet of TB-16 hydrophones, the TB-23 towed-array sonar measured over 900 feet in length, mounted nearly 100 hydrophones, and was towed at the end of a 2,600-foot cable. Then he returned to the sonar room.

"Captain, blade rate indicates Master 1's speed is steady at eighteen knots," reported the sonar supervisor. "We're getting more tonals now, including one from the conformal array. She's definitely not American. The tonals compare to those listed in the sonar intelligence manuals as unique to Chinese Han class, number 402."

That stopped Mack. "I thought 402 was sunk by the submarine escorting Nimitz" he said.

"So did naval intelligence," the sonar supervisor replied. "I guess they got their numbers mixed up. Wouldn't be the first time."

The captain called to the OOD, "Begin retrieving the TB-23.1 don't want to get tangled up in case we have a fight on our hands." The towed-array sonar was valuable for quietly listening to passive sonar contacts, but Mack, like many submarine captains, preferred to retrieve it before engaging in close combat with an enemy submarine.

Mack left the sonar room and went back to the conn to see how the fire-control solution was coming.

"Conn, sonar, our contact, Master 1, just stopped his shaft."

Seven more minutes passed, Cheyenne''s sonar operators carefully monitoring the tonals from the Chinese submarine's reactor coolant pumps. These had to be run constantly in order to avoid destroying the reactor, one of the few drawbacks of a nuclear-powered submarine. A conventional, or non-nuclear, submarine could stop dead in the water, running entirely on her battery power, and be completely silent. A nuclear submarine, however, such as Cheyenne or Han number 402, had to constantly pump reactor coolant in order to keep the reactor critical and prevent its overheating. That difference meant that it sometimes could be easier to hunt an SSN than a regular diesel boat-especially when the SSN was an old, 1970s-vintage Han with reactor plant problems.

The silence ended when the sonar supervisor called, "Conn, sonar, single active pulse from Master 1." Moments later there was a second sonar pulse.

Mack ordered the chief of the watch to "Man battle stations torpedo," then took the conn from the officer of the deck.

With battle stations manned, the executive officer, in his role as the fire control coordinator, reported to the captain, "Master 1 is now bearing 169, BSY-1 range is 22,000 yards. He was not in a convergence zone."

Aboard Han 402, the Chinese commander felt as if he had little choice but to give his position away. His sonar had acquired only intermittent contact on the American submarine maneuvering in this area, and he needed to locate it in order to accomplish his mission: sink the submarine and then continue on against American merchant ships. He knew an American submarine was out there, but didn't know where, and didn't know it was Cheyenne. Unfortunately for him and his crew, however, he had thought that he was much closer to the Americans than his active sonar told him he was, 22,000 yards was out of torpedo range for his submarine, but not for Cheyenne's Mk 48s.

Those two active "pings" were a calculated risk on the Chinese captain's part. He knew his submarine was as noisy as a bull in a china shop and he suspected the Americans had been tracking him. Once he'd figured out that the American submarine had passed him he knew they could not be far off. If he waited too long, he would miss his chance to attack.

Aboard Cheyenne, Mack was trying to outguess the Chinese captain. He knew that Chinese submarines were notorious for having very poor sonar outfits, but he didn't think they were bad enough that the captain of number 402 would have no choice but to use his active sonar, giving away his own exact location. No, Mack thought. This does make sense. If the Chinese captain knew we were tracking him, he probably had figured that we knew his location, so all he was really doing was leveling the playing field-giving away information we already had in order to learn our location as well.

What this amounted to was that the Chinese submarine had gone active on the American submarine and both submarines now had an accurate firing solution. Mack didn't expect the Chinese captain to let this opportunity slip away. The Han was currently outside its own torpedo range, but that could change rapidly.

"Conn, sonar, the Han just started up again. It's making turns for twenty-five knots, sounds like she's really straining. They are closing quickly."

Captain Mackey reversed course to minimize the range closure white he ordered tubes one and two made ready in all respects.