He twisted the right grip on the scope toward him, tilting the optics as far up as he could, looking into the sky.
“No visible drones,” he said.
He heard Moody from the console. “ESM shows the nearest drone about two miles away on a relative bearing of zero-nine-zero, heading this way.”
“Seeking?” he asked.
Moody turned some knobs on the command console. “Negative, not seeking, standard random search pattern but on our vector. Should be visible in five minutes.”
She stepped up to the conn. “And it’ll see us right after we see him.” She was concerned, but willing to let Pete execute his plan.
“Understood.”
Hamlin swung the scope around to the starboard beam and looked, and waited.
He saw it three minutes later, a tiny black dot on the horizon, barely visible even with the scope in high power. It looked almost like a big seabird, a cormorant, but Pete knew they were too far from land for it to be anything natural. And soon enough, he saw the sun glint on its metallic head. “I have a visual on contact Delta-One,” he said, pushing the red button on the scope to register the bearing in their fire-control systems.
The drone was flying near the surface, in a leisurely serpentine pattern that betrayed no urgency. It was hunting, Hamlin somehow knew, but it hadn’t seen them yet, as it swooped gracefully back and forth. While it was hunting, it was also conserving energy, flying slowly, its wings turned efficiently upward to soak up energy in its solar cells, its computer steering it to take advantage of the winds, gliding when it could. In good weather, it could stay airborne for weeks.
He also knew that the drone wouldn’t see their periscope visually — its cross section, about three inches, would be invisible among even the light waves at this distance. The only effective sensor the drone had for shallow submarines was its magnetic anomaly detection, or MAD.
As long as men had made ships out of metal, people had attempted to use magnets to detect and kill them. Everything made out of steel distorts the earth’s magnetic field as it passes through, and relatively simple sensors take advantage of this. It was a time-tested method — the Germans developed very effective magnetic mines in World War II. In short order, navies began using those same magnetic effects to detect submarines. A submarine could become invisible to radar by submerging, and invisible to sonar by silencing, but the way its steel distorted the earth’s magnetic field was a physical constant, seemingly impossible to mask. MAD was a big enough threat to submarines that the Soviet Union, during the cold war, had built an entire fleet of subs out of nonferrous metals, materials that were scarce and difficult to use but produced no magnetic signature.
MAD was also a very effective method for the drones — it worked well because the drones could sweep large areas of ocean as they flew, and with large numbers of drones they could cover vast swaths of the world. Submarines could avoid detection by staying deep, but this was tactically fine with the drone strategy — a submarine forced deep was a compromised asset, limited in what it could do.
To counter this, the Polaris would try to erase her own magnetic signature, or “degauss.” This was named for the “gaus,” a scientific unit of magnetism, and was accomplished by steering the ship between two giant electromagnets. The electromagnetics would temporarily erase the field of the Polaris, making her, for a time, invisible to MAD detection. This was the first step of Hamlin’s mission, getting the Polaris through the range. But first he had to see the drones.
Looking through the scope, Hamlin could tell the instant the drone had sniffed them out. It was close enough by then that Hamlin could see the glint of the sun on its solar cells, its power-giving wings. Suddenly its graceful, lazy swooping changed. Its wings tightened up from the ninety-degree angle to its body into an attack posture, pointed and fast. It dived until it was just above the surface of the water, corrected its course slightly, and flew directly overhead. He swung the scope to watch it pass by as ESM alarms shrieked in the control room.
“Flyby!” Hana shouted, cutting out the alarms.
“Confirmed,” said Pete calmly.
“Want me to go deep?!” said Holmes.
“Not yet,” said Hamlin.
“Why didn’t it bomb us?”
“A sub at periscope depth, with just a single drone in the area — it doesn’t like its odds. Every algorithm is designed to optimize its chances for a kill, and a single shot at a periscope isn’t good odds. They’re designed to work best in swarms.”
“So now it’s going to get its friends?”
“Exactly,” he said. But still he waited, and watched.
The drone flew high into the sky, almost straight up, twisting as it soared, a motion designed to attract its comrades. An upward-looking sensor on the head of the drones was designed to look for exactly this behavior. Pete found himself curiously pleased at how well the system functioned.
“Drones approaching from all bearings,” said Hana.
Pete had no intention of allowing a swarm to get on top of the Polaris in attack formation, but at the same time he couldn’t help but stare at their deadly, beautiful efficiency. The lead drone, the one that had spotted them, banked sharply away from them, and came down to just a few feet above ocean level. The others soon aligned behind it, in a delta formation, pointed right at the Polaris. It had all taken just minutes.
“Emergency deep!” he ordered.
Ready for the order, Frank immediately pushed forward on his control yoke, and the ship took a steep downward angle. Pete lowered the scope and braced himself against the angle as they dived. Within seconds, they were at two hundred feet.
“Make your depth six hundred thirty-two feet,” he said.
Frank acknowledged the order and drove them deeper, to a point just a few feet above the ocean floor.
“Will they drop their bombs?” asked Moody.
“No,” said Pete. “We’re too deep and they know it. They won’t waste their bombs, won’t drop unless they register a ninety percent chance or better of a hit. Like bees with stingers: they only get one shot, and they want to make it count.”
“So what’s the point?”
Pete shrugged. “They know we’re here, that’s now stored in their memory; they’ll increase their concentration around us, in this whole sector, ready to pounce if we surface again. They’ll shift the priority of this area, intensify the search patterns. There are thousands of them, and only one of us. They know that time is on their side if we show our heads.”
“Which we won’t,” said Moody.
“We will,” said Pete. “In just a few minutes. But if everything goes according to plan, we’ll be invisible.”
He sat back down at the command console, switching it back from ESM to sonar. Just as planned, they were pointing right at the two bright, parallel lines of the degaussing range. “Right five degrees rudder,” he said.
Frank repeated the order and eased the ship right.
“Steady as she goes,” said Hamlin, reaching down to change the scale of the display as they approached.
While the sonar display just showed two bright green lines, vivid visual images of what lay in front of them came to Pete. First, he saw the degaussing range like an engineering diagram, the spirals of electrical coil, the parallel lines of switches, the banked symbols of the massive batteries that powered it. A remotely activated magnetic switch and a sensor at the entrance, the ship’s magnetic signature activating the range even as the range would soon erase it. This textbook diagram in his mind then gave way to a photographic image, a memory of an underwater survey, stark white lights trained on coral-covered walls, the coils of wire protected by heavy conduit, impermeable to the sea but completely transparent to electricity and magnetism. In this mental movie, a recovered memory from somewhere in his training: a lonely crab skittered across a horizontal beam encrusted in coral.