by David Poyer
Underwater sound, such as machinery noise from a submarine, traveled, or “propagated,” by three pathways: direct path, convergence zones, and deep sound channels.
“Direct path” meant sound coming straight from the source to the receiving hydrophone. Point to where you heard it from, and you were pointing at the sub. The trouble was, sound tended to curve upward over long ranges. It was a refraction effect, since water at depth, under pressure, conducted sound faster. Direct-path sound formed a curved funnel shape, seen from the side. If you were outside that funnel, you wouldn’t hear the sub at all.
Complicating it even more were the “layers,” surfaces at which the sea’s temperature and salinity suddenly changed. They reflected sound, meaning you couldn’t hear someone on the other side. The main layer, between the warmer, mixed water near the surface and the cold stillness of the depths, moved up and down between about 90 and 250 feet. Dan had felt the change on his skin during his dive on the Sang-o: an instantaneous transition between warmth and chill. If a sub hid under a layer, a ship could pass right over it and never know it was there. Like a child pulling a blanket over himself to hide from the monsters.
The tendency of sound to bend upward over long distances formed “convergence zones.” After about thirty miles, it hit the surface and bounced. If you had sensitive equipment, and positioned yourself right, that meant you could hear your quarry thirty, or sixty, even ninety miles away.
The “deep channel” was just that—deep. So deep he wasn’t even going to worry about it here.
A playground this shallow—a wading pool, in ASW terms—meant they couldn’t depend on the deep channels and convergence zone paths that were the bread and meat of open-ocean surveillance. Here, they’d use either direct path or active sonar. But “going active,” pinging and listening for the echo, gave away your own location. And the quieter a submerged sub could run, the shorter direct-path detection range became. Not only that, Op Area 25 was right on the highway for shipping transiting the Strait, adding to the ambient noise.
Everything out here loaded the dice in favor of their submerged adversaries. Unfortunately this was where, and how, the naval wars of the future would probably be fought.
“So,” Jung said, “You know what ASW really stands for?”
Dan said no. “Awfully slow warfare,” the commodore explained. It was worth a chuckle. “So we are going to do some of that in the next few days,” Jung went on, touching his mole lightly, maybe unconsciously, with the tip of his little finger. “Our passive ranges will be between one point five and perhaps four thousand yards, active direct path. There will be high biologics and fishing activity. We can also expect reverberation. So, let us turn to event 27003.”
That afternoon’s exercises were “structured,” meaning both sides knew exactly what maneuvers the other would be making and when. USS San Francisco, an attack nuke, would meet the slowly steaming Korean line on a gradually converging course. Starting at a distance of twenty thousand yards, depth one hundred feet, she’d run past them at a range, at the closest point, of three thousand yards from each ship in turn. Her first run would be a fast pass with all machinery engaged. Subsequent runs would cycle various combinations of pumps, sonars, and other equipment at varying speeds and depths. The purpose was twofold: to accustom the sonar operators to the visual and auditory return from a submerged submarine, and to tune the equipment itself to maximum sharpness.
Dan looked at his watch. Time to start. Jung was back in his chair, flipping through messages. Should he do anything? Or let the squadron staff handle it? The frigate didn’t have a separate flag bridge. The skipper and the commodore had to share the pilothouse, and he had to keep all these different Kims straight. At last he went up to the commodore and saluted.
“Yes, Dan?”
“Comex, sir. Time to begin.”
“Commander Hwang, start the exercise.”
Dan hadn’t seen the chief of staff come on the bridge. Hwang said a few words to the lieutenant. “This is Sierra Two Lima,” Kim said carefully into a microphone. “Startex. Startex. Startex. Event 27003. Sierra Two Lima. Out.”
Dan paced the bridge, then found a place to park by the chart table. Chung Nam should be on 270 at ten knots for this event. The other Korean ships would follow astern of her. But he didn’t see it happening yet. In fact, he didn’t see anything happening.
He was clearing his throat when Hwang saluted Yu. He spoke apologetically. The captain frowned, and shot angry Korean at the officer of the deck. Who in his turn wheeled and spat abuse at the helmsman. The gyro spun slowly and settled on 270.
The exercise proceeded. He went out onto the bridge wing and checked the 19. Henrickson had lashed the black box to the deck gratings. A cable ran up to a stubby whip clamped above them. The 19 computed and recorded ship location five times a minute, accurate to within twenty feet. When the mainframe back at TAG digested its recordings, those from the other ships, and those from the submarine, they’d be able to watch the tactical picture develop in twenty-second increments. When the decisions in the logs and the reports of the ship riders were factored in, analysis would yield who’d sunk whom, who’d missed chances and made wrong decisions, which tactics worked and which didn’t.
He went down to CIC and poked his head through the black curtains into the little corner sonar room. It always seemed hushed back there. A survival of the days when sonarmen had actually listened. Now they depended more on sight, interpreting the visual displays on their screens, than on their ears. Monty Henrickson and the three Korean techs were so intent they didn’t notice him for a few minutes. When they did, the eldest smiled and bobbed his head. Dan nodded back. The supervisor reached up and turned a dial.
A distant throb filled the compartment, the muffled but still audible signature of a U.S. nuclear submarine. Mixed with it were subtexts, the clicks, whines, and buzzes of biologics, pulsing throbs he guessed were the other ships and maybe Chung Nam’s own self-noise.
They were in passive mode: listening only, not pinging. The chief pointed to a shimmering display of what Dan guessed were the screw tonals. Everything that went to sea had its fingerprint, from rotating machinery, screws, cavitation, hull noise. Even dead in the water a ship chanted a narrow-frequency counterpoint composed of discrete tones from air-conditioning, generators, cooling pumps. With practice a sonar team could identify class, nationality, often individual ships. He gave them an encouraging wink. Henrickson waved back with his clipboard, and Dan backed out.
In the far corner the plotting team huddled in busy absorption. The DRT, dead reckoning tracer, was the heart of antisubmarine operations. A lit circle showing own-ship position projected from beneath the glass-topped table onto a large sheet of paper. He perched for some time on a wobbly stool, nursing what he finally realized was a caffeine-deprivation headache. The plotters, headphones clamped to their ears, had no time to talk or even look up. They jotted down ranges and bearings from sonar, radar, and the lookouts, a complete round every fifteen seconds. Own ship was in black pencil; the submarine, red; coordinating ships, blue. The wandering snarled snail-traces recorded the intricate minuet that was antisubmarine maneuvering, the remorseless long-drawn-out struggle that in wartime would end with sudden detonations and violent death.
Leaning over their shoulders, Dan saw San Francisco was drawing aft. It had passed its closest point of approach to the flagship and was now abreast of Kim Chon, the next ship astern. Dae Jon brought up the end of the line.
He refreshed his memory from his PDA. He’d have to know this cold once the pace picked up. Kim Chon was a patrol corvette, Korean-built. Corvettes were smaller than frigates, but the ASW-heavy ones, like her, carried sonar, Mark 46 Honeywell acoustic homing torpedoes, and depth charges. The depth-charge suite was interesting; he wondered if they’d be more effective against a bottomed, waiting sub than torpedoes. Dae Jon, or Taejon, was an old ex–USS Gearing class, formerly USS New, DD-818. Her sonar suite wouldn’t be up to c
urrent standards. The last ship in line, Mok Po, was another corvette, heavily gunned, but one of the non-antisubmarine-capable variants. She didn’t even have a sonar; he didn’t know why she was in this exercise at all.
The plotters’ hands whispered across the paper, etching in the new positions. Dan noted that the third in line—that would be Dae Jon—was tracking north. It had swung out of line four minutes before; now it was diverging markedly. He tapped its track, catching the evaluator’s attention. “She’s leaving the line. Closing the range. Do you know why?”
The chief smiled with an expression Dan was beginning to recognize: eager to please, but uncomprehending. He tried a few more words, then gave up and waited for the next round of bearings. When they showed Dae Jon even farther off course he pulled himself up the ladder to the bridge again.
On the wing, glancing astern—just to make sure, before he kicked up a fuss—he saw that indeed the old Gearing was pulling out of line. He checked the wing gyro, borrowed the lookout’s binoculars, and searched out along the sub’s bearing. He was looking for a periscope feather, or the gulls that often followed one, but didn’t see anything.
Jung wasn’t in the pilothouse, but Hwang was. “Uh, see what’s happening with Dae Jon?” Dan murmured. “He’s pulling out of line. Closing the range to the sub.”
“They report problems acquiring.” The chief of staff shrugged as if it were no big deal. “Once they pick up the target, they’ll resume station.”
Dan glanced astern again. The old destroyer was far out of line by now. He noticed Mok Po was hauling out now too, following the ship ahead of her. “Uh, how close are they going to go?”
“As I said: till they pick up the contact.”
Dan was about to ask what if they didn’t, but at that moment the bow of the distant destroyer swung back, her starboard-side hull numbers coming back into view. A speaker above their heads sputtered Korean. “She has contact now,” Hwang announced. “She is rejoining.”
Dan said that was good. He was turning to go below again when a white-jacketed steward bowed. He offered a tray covered with a spotless embroidered warming-cloth. Lifting it, Dan found a silver serving pot, a cruet of white fluid, and a dish of pure white crystalline cubes, stacked into what he realized after a bemused moment was a small replica Chung Nam. The smell of fresh hot coffee was overpowering. When he looked up every man on the bridge was staring at him.
HE stayed in CIC all afternoon, keeping an eye on things. Events 27005 through 27007 went off without incident, though he noted the Koreans still didn’t pay overmuch attention to the assigned course. In almost every case, they closed the range to the sub more than the event called for. They crept in gradually, as if drawn by a magnet. He thought about asking Jung to caution them, but dismissed it. That was what the intro phase was for: so Jung, or Hwang, or the individual COs would correct shortcomings themselves. There was a limit to how much he could, or should, hold their hands.
When dark fell the events were still going, though Chung Nam was off line for the time being and had withdrawn to the west to practice antitorpedo maneuvering. At last he got up and stretched. His feet hurt and his neck didn’t feel so great either. He hadn’t gotten all that much sleep over the last few days, what with jet lag and being roused early for the Sang-o. When he went back up to the pilothouse Jung was a shadow in the dark.
“Commodore? Evening, sir. I’m going to turn in for a couple hours, if you don’t need me.”
“Mr. Lenson. I understand you had some problems with our stationkeeping. That you mentioned it to one of the ship’s company.”
The sonar evaluator. “Uh, yes sir, but Commander Hwang explained what was going on. With Dae Jon.” He thought about mentioning the range issue, but decided again to let them fix it themselves.
“All right, Dan. But any other comment you may have, I’d appreciate your bringing it directly to me or Commander Hwang. Not to the ship’s company.”
That was fair; he was here to support Jung as officer in tactical command. “Aye aye, Commodore.”
“Get some sleep. I’ll keep an eye on things.”
“Aye aye, sir,” he said again, already looking forward to the narrow bunk with its knit comforter. He looked back once more, to see Jung’s shadow still resting motionless against the black, the radio speaker frying quietly above, the only sign of life the hot red dot of a cigarette like a faraway flare in the dark. It brightened, faded, and then winked out.
6
THE helicopter sketched a charcoal line across a rough gray paper overcast, aimed directly at him. Lenson slouched with thumbs in this belt loops, steel-toes braced wide, briefcase slung off his back. Chung Nam rolled with a slow nodding lean. Around him the crew shouted and rushed about. Looking flushed, Kim #3—there were so many he’d resorted to numbering them—swung his landing-signal paddles on the fantail like a jayvee cheerleader warming up her pompons. The helo banked and rapidly grew larger. Its clatter echoed across the choppy sea.
Two days had passed. Phase I was complete. Every sonar team had at least five hours’ practice tracking San Francisco and four hours tracking the smaller, and therefore harder to acquire, Chang Bo Go. The Korean 209 had joined up the day before.
The helo landing team froze in their tracks, saluting him. Or rather—Dan turned his head—saluting Jung, who’d just stepped out on the frigate’s tennis-court-sized helo deck. Dan didn’t salute, since he was uncovered, but he bowed. The commodore nodded back, then turned his attention to the approaching aircraft.
Five minutes later they sat squashed together with five other passengers, gripping their briefcases as the quivering fuselage banked hard. The deck rolled up and hovered nearly above them. They grew suddenly heavy. The sea scrolled past. He looked across the fuse-lage to meet Jung’s eyes. They stared at each other until Dan dropped his gaze.
. . .
USS John S. McCain was the Destroyer Squadron 15 flagship. Since Jung was OTC, he’d wanted to hold the pre-Phase II meeting aboard Chung Nam. But Leakham had argued McCain had better comms, a full flight deck, and spaces for a large meeting. As Dan followed Jung and the others through her centerline passageway he felt like Woody Allen unfrozen in the far future. The air was chill with air-conditioning, which Chung Nam didn’t have. The wide passageways were lined with advanced equipment. The crew, of which there seemed to be very few, wore spotless dark blue coveralls and ball caps instead of denims and greasy tees. The cold air smelled strange. It took a while before he realized the “smell” was the absence of stale smoke.
“Good morning, good to see ya. Commodore Jung, what a pleasure.” Leakham, bulky and blond and hearty, was working the arriving COs in the spacious immaculate wardroom. He pumped Jung’s hand. “Bring any PowerPoint matter? We can upload and project it here. No? Well, come on in. Decaf, muffins, hot fresh tarts on the sideboard.” Dan got only a nod. “Lenson. How you doing over there?”
“All right,” he said, but Leakham was already greeting the next officer in line, gaunt, bronzed, and glorious in white shorts and gold-encrusted cap; one of the Australians, from Darwin or Torrens.
Dan got a blueberry pastry and coffee, marveling at how strange human beings of European descent looked now. At first all Koreans had seemed identical. All dark haired, and almost all (except Jung) fairly small. But with his eye meeting no one else for days on end, they’d become individuals, each unique.
Now, back among Americans, he saw their differences not as within the norm of accustomed variability but as grotesqueries. The varied hues of face and hair and shape seemed no longer commonplace, but shocking and freakish.
He finished the muffin, ravenous, and was tearing into a flaky still-warm raspberry tart when a balding captain, probably Leakham’s chief of staff, called for seats.
The meeting went fast. He made only a few notes. Two events on the third were being switched, to avoid carrying one, which depended on visibility, into darkness if it went late. The weather didn’t look good, though. A
tropical storm near Indonesia would bear watching, the met briefer said. They’d see increased overcast, rain activity, and wind speeds between fifteen and twenty knots. But unless it actually came their way, the landmasses of Japan would mask any marked long-period swell activity.
Jung called on Dan for remarks. He reminded the assembled COs to make sure the TAG reps riding their ships had full access to tactical decision making. They should discuss with those riders their rationale for any departure from standard operating procedures. “I want to emphasize again, we’re not here to grade you,” he said, looking each in the eye in turn. “We don’t expect or require you to hew to existing tactical guidelines. We put those out as suggestions, based on what’s worked in the past, or what theoretically should give you better detection ranges, higher detection rates, better probabilities of reacquisition on a lost contact. And in the end, a better probability of kill during the attack phase. But it’s ultimately up to you which tactics you implement. SATYREs can be a fruitful source of future tactical improvements, but only if we understand what’s going through your head. Your intent is just as important as the maneuver itself. We’ll then evaluate that maneuver against its objective success. Eventually the result will show up in your publications. So keep a close eye on those data-keeping requirements, and assign people you know are on the ball.” He asked for questions, got none, and sat down.
Jung made a few remarks. He finished, “As the British learned in the Falklands—the last time submarines were faced in a wartime re-supply operation—ASW is a force-intensive activity. Even when it’s successful, it usually results, not in a kill, but just in keeping the enemy at bay.
“Given that—and we do understand that, I assure you—Korean Navy doctrine is still somewhat different from standard NATO doctrine. We believe the most effective means of keeping the threat at bay is the kill. A dead submarine will not reattack. We emphasize overwhelming force, and offensive action at all costs. I understand this is at variance with U.S. procedures. But the difference is only one of emphasis. I expect to work very closely together during the remainder of this exercise, and I hope it is as productive as Commander Lenson”—he reached out suddenly, and Dan flinched as he was patted on the shoulder, no, almost caressed—”seems to think it will be.”