Deep Sound Channel (40 page)

"Sounds great in theory," Jeffrey said.

"We'd have to work the wide-aperture system as a phased-array antenna," Sessions said,

"then digest all that raw data and reassemble everything for a sharply focused picture. . . . And that's just to use this telescope thing on one line of bearing." Sessions turned to Jeffrey. "I don't know, sir."

"We'll use finite elements for approximation," Jeffrey said. "The processes are chaotic but they're spatially continuous."

"That's true," Ilse said. "The functions would be differentiable, mathematically."

"We can do a narrowband search to simplify things," Jeffrey said. "Even if Voortrekker auto-hovers so their reactor pumps and the rest of the propulsion plant are quiet, they need a bunch of megawatts to run all their

computers and their listening gear, and to keep their bow sphere warmed up for active melee ranging once the engagement starts. We'll listen for five-hundred-hertz tonals from their turbogenerators, and fifty-hertz sympathetic line hum. That'll help us filter out irrelevant noise impinging on our hydrophones."

"I concur," Sessions said. "The problem isn't writing the code to do all that, Captain. The systems administrator and his staff have been on it for a while already. They're boilerplating and building from tool kits with the commercial off-the-shelf software we have on board. The problem is running everything fast enough for the lens effect to work."

"We'll have to make as much space as we can inside our processors," Jeffrey said, "dump or switch off everything we don't need on the LAN, other programs, irrelevant data, pieces of the operating system even."

"Can you do that?" Ilse said.

"We have off-line double backups," Sessions said. "It'll be a ton of work to reinstall everything later."

"If we don't do this," Jeffrey said, "or it doesn't work, there might not be a later."

"Deployable hydrophone lines are both in place," Van Gelder said. "Ship is in autohover. Tubes one through eight are loaded with deep-capable nuclear torpedoes, all warhead yields preset to one kiloton."

"I want to take us closer to the bottom," ter Horst said. "Around here sound rays trend upward, since sound speed increases with depth. That'll put us in a shadow zone against another terrain-hugging boat."

"I concur," Van Gelder said. "It's one benefit of being so deep in the isothermal layer." He eyed a depth gauge. "Recommend we drop to forty-seven hundred and fifty meters, Captain."

"Helm," ter Horst said, "on auto-hover, stationary

dive, make your depth forty-seven hundred fifty meters."

The helmsman acknowledged.

"All deployable hydrophones are nominal, Captain," Van Gelder said, watching his sonar repeaters. "Our search plan focuses on sixty hertz and four hundred hertz, the base-line and high-frequency tonals of the American's dual-source AC electrical supply."

"Excellent, Number One," ter Horst said. "Now we wait, and listen." Jeffrey and Ilse watched the live imagery from the ice-avoidance low-light-level TV

mounted on the sail. The plumes in the vent field to Challenger's front gave off faint luminescence, from the life-forms they fed and from chemical processes. The scalding water sprayed up from the chimneys, roiling black, spreading and mixing as it rose, the turbulence gradually subsiding with distance and elevation.

The sound of the large vent field came over the sonar speakers, rumbling and roaring like so many volcanoes or atomic bombs. Sessions filtered out the worst of the noise, which originated beneath the ocean floor or at the chimney mouths themselves. Commodore Morse looked on, kibitzing and offering moral support.

"My map of this field may be stale," Ilse said. "Sometimes a new smoker opens or an older vent dies off."

"From what we can see, your plot's accurate," Jeffrey said. "These two big plumes further in should give us a good objective lens."

"You'll be able to scan in azimuth by moving the whole ship," Morse said. Jeffrey nodded.

"We've set our signal processors to isolate the fifty-hertz line and its harmonics," Sessions said.

"Good," Jeffrey said.

"The Mark 88s in tubes one and five are nominal," Bell said. "Just give us a target, Captain."

Jeffrey glanced at his weapons status screen. Tubes three and seven, the other working tubes, were empty. "Load tubes three and seven with ADCAPs," Jeffrey said.

"They're useless this far down, sir," Bell said. "And they only have conventional warheads."

"I know," Jeffrey said. "Just as a last resort." Van Gelder stared at the gravimeter screens. Two huge seamounts loomed to port and starboard some 10,000 yards ahead, back toward Durban. The hydrophone lines covered the extinct volcanoes' off-side flanks, out to past the 5,000-meter curve. If Challenger came down either side, she'd have to cross a group of hydrophones at point-blank range. Voortrekker was in perfect position for an intercept. If Challenger came down the middle, she'd be ideally backlit by the noise source in the distance: the scattered hydrothermal fields, each the size of several soccer stadiums, that straddled the narrowest part of the choke point.

Van Gelder turned to look over the sonar chief's shoulder. They both watched the narrowband waterfalls for several minutes, scanning one bearing after another.

"Still nothing, Captain," Van Gelder said.

"Very well," ter Horst said. "They're out there. They're coming. I can feel it in my balls."

"Still nothing, Captain," Sessions said.

"We'll have to bring the boat up higher," Jeffrey said. "They must be further away than I expected, masked by ground shadowing."

"Either that," Bell said, "or this telescope isn't working."

"Helm," Jeffrey said, "on auto-hover, stationary rise, make your depth twelve thousand feet."

"Sir," Bell said, "we'll be awfully exposed like that, three thousand feet off the bottom. The pumps will be very noisy getting us up there, and the hull will pop."

"Those are chances we'll have to take," Jeffrey said.

"Make my depth twelve thousand feet, aye," Meltzer said.

"We also need to sneak our Mark 88s out there now," Jeffrey said, "so we can hit Voortrekker by surprise once we have a range and bearing. They'll be waiting somewhere between the hydrothermal field and those two 4,000-foot-high seamounts up ahead, staying within weapons range of the black smoker megaplumes."

"Sir," Bell said, "I don't want to seem a naysayer, but our units have limited cruising endurance even on low speed. We'd be gambling we make a contact before their fuel runs out."

"Understood," Jeffrey said. "But the ranges here are very large and sonar contact may be intermittent. If we use conventional tactics, a high-speed torpedo attack once we have a target, Voortrekker will hear and immediately get off a snap shot salvo. Once that happens, we can't count on hitting her with one 88 and stopping all incoming fire with the other."

"Understood," Bell said. "The best we could hope for then would be a double kill, both ships sunk."

"That's why we have to get our units out there now," Jeffrey said.

"At slow speed they'll orbit a couple of hours," Morse said.

"Understood," Bell said.

"Very well, Fire Control," Jeffrey said, "and keep asking the tough questions. . . . Now, make tubes one and five ready in all respects, including opening outer doors. Preset the weapons for twenty knots running speed. We'll control through the wire and circle one off each

flank of the hump. Run them in nap-of-seafloor mode, with tracks five hundred feet off the bottom for terrain-and sound-shadow masking. Disable active pinging, reenable only on my command."

"Aye aye, sir," Bell said.

"Once we launch, be real careful not to lose the wires," Jeffrey said. "Run them out with room to spare around these hot vents."

"Understood," Bell said.

"Very well," Jeffrey said, "here we go. Firing point procedures, tubes one and five. Manual control of the weapons."

"Both units ready," Bell said.

"Tube one shoot," Jeffrey said.

"Set," Bell said. "Stand by. Fire. Tube one fired electrically. Unit is swimming out."

"Unit is running normally," Sessions said.

"Tube five shoot," Jeffrey said.

"Set," Bell said. "Stand by. Fire. Tube five fired electrically. Unit is swimming out."

"Unit is running normally," Sessions said.

"Very well," Jeffrey said. "The clock is ticking, and the weapon fuel is burning."

"Still nothing, Captain," Van Gelder said. "It's taking Challenger longer to get here than we thought." "Patience, Gunther, patience," ter Horst said.

"Captain," Sessions said, "we're getting something now! Definite fifty-hertz tonals. I designate the contact Sierra 1. But we have a difficulty, sir. The indicated range is ninety thousand yards."

"Forty-five nautical miles," Jeffrey said. "The other side of the seamounts, well beyond the maximum range of our Mark 88s."

"Concur, sir," Sessions said. "This telescope works so well we're actually getting fiftyhertz bounces off both seamounts' inner flanks, letting us double-check the distance. Definitely ninety thousand yards."

"Sir," Bell said, "our units are committed. We are unable to shut down or retrieve torpedoes—they're not like our LMRS probes."

"I know," Jeffrey said. "I didn't think ter Horst would wait for us that far back. . . . Hmmm. The running ranges of our nuclear torpedoes are supposedly about the same as theirs, and at Voortrekker's current position both seamounts could block their shots. . . . less . . . I'm starting to think they must carry some kind of deployable weapon, deepcapable CAPTOR mines or some sort of expendable SOSUS gear."

"You'll just have to make them come forward, then," Morse said.

"Concur, sir," Bell said. "But how?"

"We'll move forward briefly ourselves," Jeffrey said, and give them something to shoot at—us."

Bell opened his mouth to object, but Jeffrey held up a hand. "Get ready to drop a wrench in the torpedo room, just to be sure."

"Hydrophone line contact!" Voortrekker's sonar chief shouted. "Now passive contact on the bow sphere as well! Direct path, relative bearing zero zero two."

"At last," ter Horst said.

"Contact classification?" Van Gelder said.

"Mechanical transient, sir. Some kind of machinery noise. Might have been a casualty in torpedo room equipment."

"Indeed," ter Horst said. "So they've had some battle damage, or the crew's been worked past their endurance. Or both. What's contact range?"

"Sir," Van Gelder said, "distortion from the hot vents is impairing our ability to triangulate using the deployed arrays."

"Give me your best guess of depth and distance," ter Horst snapped.

"Extreme range, sir," Van Gelder said, "about sixty-five kilometers. . . . For us to hear at all given ground masking effects, Challenger has to be above thirty-eight hundred meters. Conjecture that's her crush depth."

"Or it's as far down as they want to push their luck today," ter Horst said. "Interesting. . .

. Well, we'll just have to move in closer."

"Sir," Van Gelder said, "that's risky and we'll lose the wires to the deployable hydrophones."

"We must strike while we have the enemy localized, Number One. At nearly five thousand meters depth ourselves, if we simply wait here for much longer, the hydrophones might fail anyway."

"Understood," Van Gelder said.

"Don't worry, Gunther," ter Horst said. "As we get closer, we'll pick up Challenger on hole-in-ocean, long before they see us on their ambient sonar. Closing the range before we fire will cut the running time of our torpedoes, improve the odds of a kill even if the units get in a high-speed stern chase against the target."

"Concur, Captain," Van Gelder said.

"Zero zero two relative is three two three true," ter Horst said. "Helm, steer three two three. Slow ahead, twelve knots."

"Aye aye. . . . Turbine room answers slow ahead, making revs for twelve knots, sir."

"Warm up the weapons, tubes one through eight," ter Horst said.

"Warm up the weapons, tubes one through eight, aye aye," Van Gelder said.

"Preset all weapons for maximum yield."

"Maximum yield, aye aye."

"Flood the tubes, equalize the pressure, and open the outer doors tubes one through eight."

"Sierra 1 signal strength is increasing slightly," Sessions said.

"That might just be from reduced particulate attenuation," Ilse said, "along our line of sight."

"Or ter Horst might be coming closer," Jeffrey said. "We have to be sure. . . . We need to triangulate, try to get cross bearings from another hot vent eyepiece."

"That one eight hundred yards north of us might work," Ilse said. Jeffrey studied the vent field map. "Concur. Helm,

ahead one third, make turns for four knots." "Mechanical transients!" Sessions broke in. " Classification?" Jeffrey said.

"Many torpedo tube doors being opened."

"How many is many?" Jeffrey said.

"Eight, I think," Sessions said.

"All of them," Jeffrey said.

1 HOUR LATER

"Still no new contact on the target," Van Gelder said. "What's range to their last known position?" ter Horst said.

"Now forty-five kilometers, Captain. Query going active for a precise range and bearing."

"No," ter Horst said, "I think it's premature. They'd have a snap shot in the water before we even heard our ping come back."

"Good," Morse said. "You've picked up Sierra 1 again. I'd suggest you shuttle back and forth, to keep updating the triangulated range and start a TMA. Now you've calibrated both eyepieces, the data reduction ought to go much faster."

"I concur," Jeffrey said. "Helm, back one third, make turns for four knots. Return us to that other eyepiece vent location."

"Back one third, make turns for four knots, aye," Meltzer said. "Maneuvering acknowledges back one third, making turns for four knots, sir."

"Very well, Helm," Jeffrey said. "Now, people, listen up, we need to caucus. . . . We have a problem. Our lure to bring Voortrekker toward our weapons seems to have worked, but now that she's in motion, she'll be harder for us to track, and she's been alerted."