Piranha: Firing Point

Now scram!” “Don’t say scram,” Pacino said. “That means’shut down the reactor’ in sub talk.”

Patton watched as Colleen mimicked the words as they came out of Pacino’s mouth. Mimicking a three star admiral. Then he looked at Pacino, and realized that something was going on between the two of them, something more than just business. Patton turned to leave behind the admiral.

“Good luck, Ms. O’Shaughnessy,” he called.

“Colleen, please.” She was already lost again deep in her world.

“She’s a beauty,” Patton said, “isn’t she?”

“I hadn’t noticed,” Pacino said.

On the lower level was a machinery space aft, a middle area with a central passageway, a stores room to port, more berthing spaces to starboard, and the torpedo room forward. This room put the one on the Annapolis to shame. There were weapons crammed in everywhere on hydraulic rams, the room barely allowing him to get forward to the torpedo console.

“Two 21-inch tubes on the bottom, two 36-inchers on the top. The room holds forty-eight 21-inch weapons or thirty-four of the 36-inch large-bore missiles. Our loadout this run is mostly 36-inch Vortex Mod Charlie missiles, with two tube-loaded Mark 52 21-inch Hullcracker torpedoes and two room-stored Mark 52s.” “Vortex missiles?” Patton asked. “Why haven’t I heard of them?”

“Because they’re classified secret, of course. I’ll tell you more about them later, but they’re a small version of the solid-rocket-fueled mod bravo we employed in the Japanese blockade. The weapon does a swimout on an oxidized-fuel propulsion module, then at fifty knots the control fins pop out and the solid fuel ignites, and the missile travels to its target at three hundred knots.

It doesn’t have the range of the old mod bravo, but if we’re in close, we can get a kill.”

“For the SSNX, what’s close?”

“On your 688 the most distant sonar contact you could hear, a submerged target, came at what, twenty to forty miles?”

“Yessir.”

“For the SSNX, that’s close. We can detect a submerged contact eighty or ninety miles away.”

“How? What did you do?”

“Sonar’s completely different on this ship. We don’t have a wide-aperture array or a spherical array, not since the redesign. We use a system called ADI, for Acoustic Daylight Imaging.”

The two men climbed the aft ladder back to the middle level, and walked back to the control room.

“How does it work?”

“Easy to explain, hard to engineer it and implement it, even harder to connect it to a computer and make the readout meaningful. In the past we used broadband sonar, just listening to the ocean, all frequencies, all the white noise. Worked great on surface ships, since they’re so loud you hear them a hundred miles away. And it worked great on the first-and second-generation Soviet subs too, because they were clanking train wrecks. But once the third-generation Soviets came out, we switched to a combination of broadband sonar and narrowband, using towed hydrophones on long cables, and the hydrophone array was a couple hundred feet long, capable of hearing very selected frequencies a long way away, as long as it was connected to a damned good computer. The limiting factor was the computer.”

They were back in control, and Pacino leaned against the elevated periscope-stand handrails. Patton sat down in the command seat on the port aft part of the periscope stand.

“As the computer got better, detection range didn’t.

Then the Destiny-class Japanese subs came out, and they were too silent to pick out at a distance with our narrowband processors. The Seawolf-class ships did pick them up, because they were much quieter and had better narrowband towed arrays. But with ships out there like the Rising Sun, narrowband is proving to be old technology.

And we suspect that the next generation of enemy sub may employ an active quieting system, deliberately putting out noise that exactly matches a sub’s machinery, but phase-shifted so that it cancels out the machinery noise. John, we’re ten years away from enemy subs being so quiet that they match or beat the Seawolf or SSNX classes, and with active quieting they will actually be more silent than the ocean around them. Invisible.”

“So what next. Admiral?”

“ADI, acoustic daylight imaging. It’s a quantum leap in sonar, John. We’re changing the way we think about sonar as a sensor. In the past we tried to listen with it.

We tried to listen for very specific noises, but that’s not good enough. Now we don’t listen anymore, we see.

Sonar is no longer an ear, it’s an eyeball. It works like this. The ocean is full of background noise. Waves. Fish.

Shrimp. Whales groaning. Wind. Storms. The occasional lava from an underwater volcano. But it’s everywhere.

Up till now we’ve tried to ignore the background noise and pick the needle out of the haystack. Not anymore.