The Seventh Angel (49 page)

He rubbed his chin. “We’d better leave the life rafts alone too. I hope like hell we don’t need them, but things might get ugly tonight, so let’s not take a chance on that.”

“
Try to think like ghosts,” he said. “Think of anything you can to make this ship invisible and undetectable. Because if we get caught, those bastards are going to do their best to turn us into ghosts for real.”

He scanned the assembled faces. “Any questions?”

“
Yes, sir,” one of the female chiefs said. “What if we’ve got topside gear that won’t fit below decks?”

“
If it’s not something we’re going to need immediately, we may have to toss it over the side,” the XO said. “If you’re in doubt, ask your Department Head. Make sure you get the serial number off of anything that goes in the drink. We’re going to have to account for that stuff later.”

If there
is
a later
, Ann thought.

The XO looked around again. “Any more questions?”

No one spoke.

The XO clapped his hands. “Alright, people. Let’s get to it.”

MOUSE (MULTI-PURPOSE AUTONOMOUS UNDERWATER SYSTEM)

SOUTHEASTERN SEA OF OKHOTSK

THURSDAY; 07 MARCH

2139 hours (9:39 PM)

TIME ZONE +11 ‘LIMA’

It began with a single frequency. The sound was weak at first, hovering right at the detection threshold for Mouse’s passive sonar sensors, so the robot tagged the tonal, and began sending frequency and bearing information to its onboard acoustic processors for evaluation. The signal was very close to one of the frequencies listed in the robot’s library of mission data. It was one of the tonals that Mouse’s target was known to generate. But the signal strength was only fractionally higher than the ambient noise level under the ice pack. It was too weak and intermittent for tactical exploitation, and there were no corroborating frequencies to make further identification possible.

Mouse’s onboard computer labeled the lone frequency as “
Investigatory Signal #1
,” and assigned a confidence factor of 02.1%. Mouse was 2.1% certain that Investigatory Signal #1 was the target the robot had been programmed to find.

The mission was only a few hours old, and Mouse still had most of the search grid left to cover. The computer weighed this knowledge against the low confidence factor it had assigned to Investigatory Signal #1, and decided not to deviate from the search grid to pursue the weak signal. Instead, it would monitor the frequency, and reevaluate later if the circumstances changed.

The robot continued on its course, gliding slowly but quietly toward the next waypoint in the search grid. It cruised past ice keels, which it identified only as navigational hazards, and through swarming schools of under-ice krill, which it recognized only as a source of non-target noises. Mouse was neither interested in these things, nor distracted by them. Despite a high-degree of functional autonomy, it was a very single-minded machine. It had been programmed to carry out a task, and anything not directly related to that task was irrelevant.

As Mouse followed the search grid, the strength of Investigatory Signal #1 began to fade. The robot’s computer noted the waning signal strength, but decided that the priority of such a low-confidence tonal was too low to justify turning away from the search program.

Mouse reached the next programmed waypoint, and turned thirty-five degrees to starboard, to begin its transit toward the waypoint after that. Almost immediately after the robot made the turn, the strength of Investigatory Signal #1 began to increase.

It was slow at first, the signal growing stronger by tiny increments. After three minutes on the new course, the signal strength began increasing more rapidly.

The robot detected a second acoustic frequency, on the same bearing as Investigatory Signal #1. The second signal was routed to acoustic processing, and was identified as another tonal that Mouse’s target was known to generate. The computer tagged the new frequency as Investigatory Signal #2, and noted that the strength of both signals were increasing now.

To say that Mouse became excited would be both an overstatement, and a misnomer. The robot had no emotions whatsoever. It neither liked, not disliked anything. It had no preferences, or fears. Nevertheless, an examination of the machine’s electronic mission records might have easily led an unknowing person to make that mistake.

The electrical activity inside the robot increased dramatically. Mouse’s computer began loading and activating additional subroutines and library function calls as it continued to evaluate the signals that its sonar sensors were tracking. The confidence factor rose to 12.7%, and then 25.8%, and then 33.2%.

Based on signal strength and bearing drift, the computer decided to deviate from its programmed search grid. It was not a large enough deviation to affect the integrity of the search, but a small one that could be easily compensated for if the signals did not turn out to be the target of interest.

The robot turned seven more degrees to starboard, and was almost instantly rewarded with a third acoustic signal. Another search of the mission library revealed that this new frequency, Investigatory Signal #3, was also one of the tonals that the target was known to generate.

More significantly, this third tonal was one of the designated
class identifiers
. Unlike the first two frequencies—which might have originated from many underwater sources, including Delta III class submarines—this new frequency was known to come
only
from Delta III class submarines. There were no other known underwater sources for this particular frequency.

In the world of passive sonar, a class identifier is the acoustic equivalent of DNA evidence. It’s as close to positive identification as the physical limitations of the audio spectrum will permit.

The robot’s mission library included the acoustic class identifiers for the target Mouse had been programmed to find. Based on the newly-detected frequency, the computer elevated its confidence factor to 98.2%. Mouse was now 98.2% certain that it had located the assigned target.

This new confidence level was more than high enough to justify abandoning the search plan to pursue the source of the frequencies. Mouse shifted from
search
mode
to
autonomous mission
mode
, so it could carry out the next phase of the mission. And that’s when the problem occurred.

The mode shift triggered a bug in Mouse’s core operating program. If the code had functioned as its programmers intended, a subroutine would have recorded the nature of the mistake for future correction, and then bypassed the error to allow the robot to continue functioning. But the software glitch got in the way.

Instead of bypassing the error, the faulty program activated Mouse’s emergency maintenance routine, falsely informing the robot that it had suffered crippling damage, and ordering it to return to its point of launch to surface for repairs.

The robot noted the damage alert immediately, and prepared to terminate the mission and head for the launch and recovery coordinates.

But Ann Roark’s software patch was installed and at work. As with the rescue of the
Nereus
, the software workaround had four elements: one conditional statement, and three commands:

The first line of code triggered the workaround the instant that Mouse’s computer kicked into emergency maintenance mode. The second line canceled the order for emergency maintenance mode. The third line ordered the robot to ignore the error and continue operating as if no fault had been reported. The last line of the workaround inverted the logical conflict that had triggered the original error.

The Mouse unit had responded to a false report that it had sustained critical damage. Ann’s code patch inverted the logical state of the erroneous report, switching “CRITICAL DAMAGE = YES” to “CRITICAL DAMAGE = NO” in the robot’s memory.

The conflict was eliminated. The computer determined that all conditions had been met for the autonomous phase of the mission to commence. The robot made a five degree starboard turn to improve its angle of approach, and began moving toward the target.

Mouse had no idea of the nature of its quarry, or the ultimate purpose of its mission. It thought only in terms of waypoints, frequencies, obstacles, and manipulator functions.

Two hundred feet beneath the ice pack, in a body of water that most people couldn’t find on a map, a small unarmed robot glided through the darkness toward a 13,000-ton nuclear missile submarine.

USS TOWERS (DDG-103)

SOUTHEASTERN SEA OF OKHOTSK

THURSDAY; 07 MARCH

2206 hours (10:06 PM)

TIME ZONE +11 ‘LIMA’

Ann Roark was looking the other way when the icon popped up on the display of her laptop. When she looked up, the computer showed only the ship’s position indicator and a silhouette map of the Sea of Okhotsk. She glanced back down, perhaps a second later, and the triangular green symbol was burning bright on the screen.

Ann had the laptop speakers muted, so the arrival of the icon came without sound or commotion, but it startled her just the same. Something heavy clunked inside of her, as she realized that the next scene of this crazy little drama was about to play itself out.

She thumbed the trackball, scrolling the computer’s cursor over the green triangle. A small block of alphanumerical data appeared to the left of the icon. Ann read the little status report twice, to be certain that she was interpreting the situation correctly.

Then she leaned back in her seat and glanced around. None of the Navy people happened to be standing nearby at the moment, so she stood up, stretched, and walked briskly over to the Tactical Action Officer’s station.

She didn’t know the man in the TAO chair, but she recognized from the silver bars on his collar that he was a lieutenant. The Navy guys called those bars
railroad tracks
. She was starting to learn this stuff. She wasn’t sure if that was a good thing.

She tapped the TAO on the shoulder. The man recoiled at her touch, and Ann felt a tiny hint of satisfaction at having startled one of the warrior types. Obviously, she wasn’t the only person feeling the pressure.

When the man looked up, Ann pretended she hadn’t noticed his flinch. “I don’t have a headset, so I couldn’t call you on the net,” she said. “My robot has found your submarine.”

The man sat up straighter. “What? Are you sure?”

Ann looked back toward her laptop. “Yeah. That’s what Mouse is telling me, anyway.”

The man keyed his microphone, and spoke into his headset. “USWE—TAO. Can you step over to my station, Chief? I need to talk to you.”

The redheaded Sonar Technician, Chief McPherson, appeared at the TAO’s chair a few seconds later. The cord of a disconnected headset was draped around her neck. “What’s up, sir?”

The TAO inclined his head in Ann’s direction. “Ms. Roark’s robot has detected the target.”

Chief McPherson raised her eyebrows. “You’ve got high-confidence classification on the contact?”

“
Yeah,” Ann said. “Mouse detected three frequencies consistent with a Delta III submarine. One of them is flagged as a class identifier.”

The chief gave a thumbs-up gesture. “Excellent! We need to get a tactical feed to Fire Control immediately.”

Her face took on a thoughtful expression. “We can’t hook your laptop into CDRT or Fire Control, so we’ll have to do this old school. I’ll station a phone talker over your shoulder. He’ll relay the data to us, and we’ll punch it into the system manually.”

Ann held up a hand. “Whoa there, cowboy. I can get you a recent position for the sub, but I can’t give you real-time information.”

Chief McPherson’s eyebrows narrowed. “Why not?”

Ann struggled to keep the frustration out of her voice. “Because your captain told me to lock out the acoustic modems,” she said. “Remember that strategy meeting in the wardroom? You guys decided to restrict Mouse’s communications to low-power UHF, so the submarine can’t detect him. He can’t transmit or receive UHF when he’s under the ice. Every time he needs to make a report, he has to break off his track of the submarine and come out to open water, where he can drive to the surface. With transit time and everything, our first fix is already nearly twenty minutes old.”

Chief McPherson grimaced. “Damn! I forgot about that. What about the beacon? Did he attach it to the submarine’s hull?”

“
Yes,” Ann said. “Your beacon is in place, and waiting to be triggered.”

“
That’s one piece of good news,” Chief McPherson said.