Po’s secret friend. Jewel.
“Passing 340 relative and increasing engine noise.”
“Increasing speed?”
Two men in a darkened ballroom. Each can track the other only when he moves and makes a noise. Where is he? Where is he going? How fast is he moving?
Omnipresent—Is he behind me?
The sonarman, his best, watched his three screens, touching buttons and waiting for the computer to analyze tracking data. Passive sonar was an imperfect sensor that had to detect emanations from the target; only active sonar sent out its own signal and listened for the reflection. Sonarmen on passive looked for certain telltale “lines:” auxiliaries, reactors, propeller wash. They hoped for a specific signature that could be reliably assigned to the target, and not, say, a passing whale or a fishing boat on the surface. When they had a library of such noises, they became better trackers, but this endless game of follow-the-leader required constant analysis and perfect guesswork. The cream of the sonar team had been at their stations since they entered the difficult undersea terrain of the Aleutian chain—three watches. The captain hadn’t left the bridge for more than an hour in four days. Despite air-conditioning and high discipline, the bridge stank of sweat and shorted electrical power, a faint ozone smell that never left the Admiral Po. The captain thought it was the smell of leaking radiation.
“Nine knots and still increasing, turning hard to port. I think he’s diving, as well. I’m losing the track in his own wake.” The man sounded exhausted. That was not good; the excitement had kept them going through the first bad moments off Kodiak Island. Now that, too, was gone.
“Come to 270 and make revolutions for three knots.”
“270 and three knots. Aye.”
“Status?”
“He’s gone.”
The captain rolled his head slowly to the right and left, banished all thought of angry response from his mind, and settled slowly into his command chair.
“He’s drifting. He will complete the turn as a clearing turn before running the Unimak channel.” The captain didn’t feel anything like the certainty he projected, but it was a skill that came with command.
“270 and three knots, captain.”
“All engines stop.”
Two of the sonarmen played with the bow sonar, a much weaker engine than the powerful towed array behind them. The tail could be deployed only at low speeds, and certain maneuvers like rapid turns were not possible while it was deployed, but it was their only tool for following the American. The bow sonar had intermittent contact at best. He could hear the two murmuring to each other about the noise that the ocean was making, pounding on the island due north of them. Background noise, a white noise that would cross most of the spectrum, all of the “lines.” They were murmuring because sonarmen had a superstitious respect for their opposite numbers, afraid that loud conversation would be heard by the opposing specialists. No one knew how good the American sonars really were, but four days had taught the captain that they were not as good as his worst fears, and their tactics showed that they were cocky.
That still left a lot of room for them to be very, very good.
“350 relative! Range 3500 meters and closing!”
It was eerie, having his prediction fulfilled like that. He had tossed it off, based, yes, on some experience. But mostly to steady the bridge crew. The bastard was coming around toward them, and quite fast, now that his engines were driving him again.
“Take us down to 255 meters, bow up.”
“255 meters, bow up, aye.” The Admiral Po began a very slow dive, aiming to get her metal bulk through the deep isothermic layer that would reflect most sonar and greatly hamper passive detection. The captain looked down at his knuckles on the collision bar in front of his command seat and gradually willed his hands to relax.
In the darkened ballroom, there are long, velvet curtains that hide sound if you can get behind them.
“000 relative, 3000 meters and closing. Speed five knots. Vector 190.”
The boomer suddenly appeared as a digital symbol on the command screen with her course and speed displayed next to her. The distance between the Admiral Po and her quarry seemed very short, and the captain wondered if they were about to change roles.
“255 meters.”
“Try to put the bow sonar up in the layer.”
“Bow up, aye.”
This was a tricky maneuver and one that couldn’t really be accurately gauged for success. It required that the planesman adjust the pitch of the submarine so that her bow sonar was actually above the acoustic layer, allowing that sonar to listen to the enemy while the rest of the submarine’s metal hide was hidden below the temperature gradient of the layer. The problem was that you never knew for sure that you had it exactly right; the acoustic layer was simply a metaphor for the invisible line where two different layers of water with different temperatures met. It couldn’t be seen, only sensed, and only sensed as a relative gradient. The bow might be in the layer or meters above it, depending on luck and skill and local variations.
He’s bow on to us right now. The American, with his infinitely superior equipment, was in the best position he could ask to detect Admiral Po.
“Nothing on the tail.”
“Bow sonar has contact, 010 relative, 2500 meters and closing. Speed five knots. Vector 180.”
He has us. Or he will turn away.
The captain turned to the planesman.
“Well done. Very well done.” The bow sonar report indicated that the bow was, indeed, above the layer. But how far? And how reflective was the layer?
He watched the symbol on the bridge screen, the only visual input that mattered, willing it to continue its turn to port.
“020 relative, 2700 meters. Speed six knots. Vector 160.”
Deep breath, long exhalation.
“Make revolutions for three knots. Hold us at 255 meters and pitch for normal.”
“Aye, aye.” That pulled the bow back under the layer, making them blind, but he had to move or the American would get too far away. Simply avoiding detection was only half the game.
“Three knots.”
“Helmsman, three knots for the center of the channel.”
“Aye, aye.”
He cast an eye at the chart and decided he had a safe amount of water under his keel, even in these treacherous seas.
“Depthfinder off.”
“Depthfinder off, aye.”
Ahead, perhaps well ahead if he stuck to his six knots, the American would be entering the channel already. The captain calculated quickly; the American would
