SSN - Tom Clancy [8]
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.