"Do you want to stream the towed array?" Gordon asked. Right now, Rodriguez was the most important man on the boat, and he didn't mind deferring to his expertise at all.
"Not necessary, sir. I think this is going to give us what we need."
Los Angeles class boats were also equipped with a BQR-15 towed array sonar, essentially a microphone which could be streamed aft at the end of a long cable… as far aft as five hundred feet. When fully deployed, the BQR-15 was also omnidirectional, providing coverage all the way around except for dead ahead, and to a greater range and a greater sensitivity than the boat's other arrays. It would have been perfect for providing the high-resolution scan Rodriguez needed.
Gordon had not deployed the towed array, however, for several reasons. It made a noise when streaming aft, and all noise was to be avoided right now if possible. More importantly, the Pittsburgh might have to accelerate and maneuver swiftly and without warning. It took time to reel in the TA, and a sudden sharp turn could lose it astern when the cable snapped.
There were other dangers as well. There was at least one case on record, just seven months ago, where a Russian PLARB, possibly a Typhoon, had become fouled on the towed array of a British submarine, the HMS Splendid, when the two got a little too close in the Barents Sea. The Typhoon, reportedly, had limped back to port with the Splendids TA still fouling one of her screws.
So Gordon had not deployed the TA, which might have given them a bit of a tactical edge in this encounter. But if Rodriguez thought he could hear what he needed to hear without it…
"Got it!" Rodriguez said, a grin spreading across his face. "It's our old friend, Sierra One!"
"What, the Sierra class boat we picked up off San Francisco?"
"The one and the same, yes, sir." He pointed to the screen, showing two clear sets of sound traces at slightly different bearings. "The Sierra II is running submerged, speed matched to the Kresta, and about a thousand yards ahead of her. A Sierra's sonar suite is a lot better than a Kresta's, especially her towed array. The sub may be hunting for the cruiser. The seeing-eye dog routine."
"Makes sense." He reached for the 1MC switch. "Conn, this is the captain."
"Conn, aye," Latham's voice replied.
"Bring us back to one-four-five degrees, ahead dead slow. I want to let these bad boys get past us before we get too close."
"Change course to one-four-five degrees, ahead dead slow, aye, sir."
Turning so her bow was again pointed at the other vessels would reduce Pittsburgh's aspect, and possibly help hide her. Sound radiated from her hull in all directions, of course, but sound traveling up her length, from her screw and engineering compartment, might be absorbed by her length a bit as it was transmitted forward through the hull, reducing her signature slightly. Dropping her speed to a two- or three-knot crawl would help maintain her audio invisibility as well.
"Sierra Five-zero is slowing, sir. Range ten thousand… and almost directly ahead. Looks like she's just stopping dead in the water. Sierra One is pulling ahead of Sierra Five-zero, maintaining ten knots."
"Okay. I don't like the looks of this. I'm going back to the combat center. You keep an ear on both of them, and tell me the moment there's a change."
"Aye aye, sir."
Back in the control room, at the chart tables, he checked the transparent overlay, where the QM of the Watch had marked the new contacts in red.
"Conn, Sonar," sounded over the 1MC. "Aspect change on Sierra One. Looks like he might be pulling a Crazy Ivan."
Which made no sense if he was deliberately leading a
Kresta ASW cruiser. Crazy Ivan turns were performed to make sure they weren't being followed by Americans, not members of their own Fleet.
"Sonar, Conn. Which way is he turning?"
"Sierra One is turning to port, sir."
Turning toward the silently lurking Pittsburgh, rather than away. The range would be closing. Not good.
He looked up at Latham as the Exec joined him at the table. "Start thinking like a hole in the water, Number One."
"Hell, I'm not even here, Skipper."
"Good man."
"Conn, Sonar. Sierra One has changed course. New heading is two-seven-zero."
Gordon checked it on the chart. The Sierra II was now heading due west, and if he stayed on the new heading, would pass a mile or so south of Pittsburgh's position.
"Maneuvering, ahead slow. Make turns for five knots."
"Ahead slow. Make turns for five knots, aye." He looked at Latham. We'll pass behind the cruiser's stern, quietly. That will put the Kresta between us and the Sierra, and give us a clear shot at slipping away and out through the Kuril passages."
Latham nodded. "Sounds like a plan, sir. We can't stay put, that's for damned sure."
Pittsburgh edged ahead, ever so gently. Gordon had complete confidence in her quieting; Los Angeles Flight II boats were almost embarrassingly silent. The Sierra was quiet as well — not as silent as an LA-class, but at least as good as a Sturgeon. The only reason Pittsburgh was able to track the Sierra at all was the level of her technology and, even more, the quality of her sonar crew. He doubted very much that the Sierra's sonar crew could track the 'Burgh.
But that was no reason to get careless. At five knots, the Pittsburgh was effectively silent.
Minutes passed… and passed. After half an hour, Pittsburgh had closed the range to the Kresta to about five thousand yards. The Sierra II sub, meanwhile, had quietly slipped south of the 'Burgh, as predicted, and was now about two miles to the southwest, astern and behind the American boat. The other sub had also just slowed sharply, to about four knots.
"Conn, Sonar! I've got new sounds from Sierra One. Sounds like wake noises. I think they've raised their periscope."
Odd. They wouldn't be searching for the Pittsburgh on the surface, certainly.
But there might be another reason to raise something… like a radio mast.
"They may be communicating with the Kresta," Gordon said. "They might want to—"
A single sharp ping echoed through the American boat's hull, an initial chirp followed by a wavering, falling tone.
"Conn, Sonar! Sierra Five-zero has gone active! We're lit!"
"Shit!"
There was no way either the Kresta or the Sierra could fail to see the Pittsburgh now. That single sonar pulse had illuminated everything in the water for four nautical miles in every direction.
"It's roach on the plate time," Latham observed. A second ping echoed through the control room.
"Maneuvering! Ahead full!"
"Maneuvering, ahead full, aye, aye!"
"Conn, Sonar! Sierra One is turning to starboard. Looks like she's coming about to put herself on our tail."
"We've got a lead," Gordon said. "Let's use it. Diving Officer! Set depth to two-one-zero feet."
"Set depth to two-one-zero feet, aye, Captain," Carver replied.
The deck tilted sharply forward as Pittsburgh nosed downward.
"Conn, Maneuvering. Making turns for three-five knots."
"Leveling off at two-one-zero feet."
"Very good. Steady as she goes."
"Steady as she goes, aye, sir!"
At thirty-five knots, Pittsburgh closed the range to the Kresta class cruiser in a bit over three minutes. He could only imagine the consternation that must be spreading through her decks as her crews realized they were being charged by an American submarine.