by Larry Bond
LaVerne skimmed over the seabed at a height of one hundred feet and at a speed of five knots. She had to be high enough off the ocean floor to get the desired swath width. The idea now was to cover as much ground as possible, sweeping an area over a thousand yards wide and fifteen miles long. Each survey zone was a fifteen-by-fifteen-nautical-mile box, and LaVerne would diligently scan almost eighty-five percent of it before returning to Seawolf.
The UUV’s mission was to find places on the seabed suitable for automated acoustic sensors. She had to do it covertly, of course, to avoid alerting the Russians. The Russians, however, had long ago mapped this part of the Barents and more. It had been a simple matter to choose where their buoys would be emplaced.
The Amga autonomous submarine detection system was a heavily modified version of an earlier acoustic warning buoy. The cylindrical body was three feet in diameter and five feet long. The buoy was moored to the bottom, floating about sixteen feet off the seabed. Its only distinctive features were twenty-four three-foot metallic tubes running around the circumference of the cylinder. These were the passive hydrophones, the parts that actually received the sounds. The rest of the cylinder, top and bottom, and even the anchor that held it to the bottom, was coated with rubberized foam that hid it from any active sonar searching the area.
Inside the Amga buoy, a sophisticated computer listened to the ocean around it. Because the Russians were familiar with the area, they knew what sounds were typical: the sounds of ice, the sounds of sea life, even wave slap were stored in the computer’s memory. They also stored the sounds made by a submarine, both Russian subs and other countries’.
The designers had worked hard on the automated signal processing. They didn’t want the buoy sounding the alarm every time it heard something it didn’t understand. In engineering terms, it had to have a “low false-alarm rate.” So it used an intricate series of algorithms to assess the sounds it was hearing. For a contact to be valid, its noise pattern had to meet a majority of the preset conditions.
When LaVerne passed by one of the Russian buoys, it was two thousand yards away. That was close enough for the Russian buoy to hear the noise made by the UUV’s motor, but it wasn’t enough noise to trigger a response. According to the buoy’s electronic brain, this contact didn’t sound right. A submarine would make many different kinds of noises, from the many pumps, motors, and other equipment inside the sub’s hull to the flow of water around the hull, and they would be louder.
On the next pass, LaVerne was on the other side of the buoy, and even closer, but the Russian computer still ignored the UUV. Her mapping sonar swept across the buoy, but LaVerne was programmed to search the bottom. It noted the location of an anomalous fuzzy echo, but took no other action. That wasn’t part of its assigned task.
The two robots, both designed to search, studiously ignored each other as LaVerne worked its way past and away from her stationary Russian cousin.
* * *
Jerry wasn’t the only one watching the fathometer. In these waters, with the charts they had, the OOD, the quartermaster of the watch, even the sonar supervisor kept one eye on the display.
They’d had a bad scare earlier when they watched a seamount appear from out of the depths. In a little over three minutes, the bottom went from 128 fathoms beneath the keel to 47 fathoms. Fortunately, the seamount was right where it was supposed to be. Seawolf came up to 150 feet, 25 fathoms, to clear the obstacle.
Everyone on board remembered the vivid photos of USS San Francisco in the drydock after her high-speed interaction with an undersea mountain. Jerry was pleased that they weren’t taken by surprise. And then it happened.
The depth under the keel changed from twenty-two fathoms to ten in less than a minute, and that was with Seawolf creeping at five knots. There was nothing on the chart to indicate a rapid change in the bottom contour. In fact, there was no depth marking near their position at all—mare incognita.
“Yellow sounding!” shouted QM2 Dunn.
The warning call, “yellow sounding,” alerted the OOD that the ship was entering potentially dangerous depths and required immediate action. A red sounding meant you were at the limit of the captain’s comfort zone and the OOD needed to call him immediately, in addition to any other actions. The actual warning depths themselves were chosen by the commanding officer. Given the uncertainty in their charts, Rudel had chosen a healthy ten fathoms for the yellow sounding and eight fathoms for the red sounding.
Jerry’s “Recommend we slow to three knots” was matched by the OOD’s order. They spoke at the same moment, then looked at each other and smiled, but only briefly. The OOD also changed Seawolf’s depth to 125 feet, just to be safe.
In another time, another place, Jerry had used UUVs to scout the bottom in front of an advancing sub, but there were none to spare here. Patty and LaVerne were both out, and Seawolf was headed for Patty’s recovery point. Maxine was in the torpedo room being prepped for her next run.
“Recommend turn to port, new course zero five zero.” That was at right angles to their old course. There was little on the chart to recommend port over starboard, but the coast lay some distance to starboard.
“Left standard rudder, steady on course zero five zero.” Greg Wolfe was OOD again, and followed Jerry’s recommendation almost before he finished. As Seawolf’swung onto her new heading, Wolfe asked simply, “Depth?”
“I dunno, Greg. You’ve pretty much run out of our allowed depth band. We’ve only got twenty-five more feet left to play with. We’ve still got twelve fathoms under our keel. We can afford to wait a beat.”
At speed, Seawolf could turn almost like an aircraft, but creeping at three knots, her bow took almost a minute to swing ninety degrees. Jerry watched as the fathometer showed twelve fathoms as they finished the turn; then suddenly it read sixteen, then twenty-two fathoms.
“Steep slope, especially considering our speed,” remarked Wolfe. Jerry nodded agreement. “If it’s that steep, we’ll only need a few minutes on this course. ”
Jerry lost his thought as the numbers on the fathometer changed again. They dropped to thirty fathoms, but then spiked upward, to twenty, fifteen, ten, then eight almost too fast to read.
“Red sounding!” exclaimed Dunn.
“Helm, back one-third! Captain to control! Diving officer prepare to hover.” Wolfe’s order cut their speed quickly to zero. A slight shudder could be felt on the deck.
The chief of the watch had passed the OOD’s call back to Rudel’s stateroom almost as soon as he had said it. The captain appeared dressed in gray sweatpants and a dark sweatshirt as Wolfe and Jerry considered their options over the navigation plot. Surprised by the captain’s dress, Jerry remembered it was past three in the morning.
Rudel joined Wolf and Jerry at the chart table.
“Sudden shallowing on two sides, sir,” explained Wolfe, and Jerry showed their course changes and the depths. Aside from Seawolf’s annotated track, there were only the barest hydrographic data.
Rudel ratified Wolfe’s actions. “Nice job, mister.” He paused. “To both of you”—including Jerry. “The bow sonar cannot double as a bumper.” It was just an offhand remark, but all three knew exactly what would happen if Seawolf’struck a submerged obstruction, even at three knots.
They all studied the chart for a few moments, then Wolfe sighed. “Same drill as last time, sir?”
Rudel nodded, frowning. “Yes. Backtrack five miles, and then make a ten-mile detour to port, then a new course to the retrieval point. What will that do to our arrival at rendezvous?”
Jerry did the math in his head while Dunn laid in the new course. “It adds an hour and a half to the transit at five knots. It eats into our margin, but we’ll still be waiting when Patty arrives.”
“That’s fine, Mr. Mitchell. Now use the rest of the transit, including that extra hour, to get some sleep. You don’t look so good, and I want you alert when we recover Patty.”
Reluctantly, Jerry headed for h
is stateroom. He knew Dunn was up to navigating for Wolfe, but if they hit something, it wouldn’t matter who was on watch, and what Jerry thought of their abilities. It was always the navigator’s responsibility, whoever was in control. Jerry still had to force himself to delegate.
* * *
It seemed only seconds later when Chief Hudson was shaking his shoulder. “Mr. Mitchell, can you hear me?”
Jerry’s initial response was a cross between “I’m awake” and “What time is it?”
Hudson ignored his confused mumble. “We’ve been buzzing your phone, but you didn’t pick up. Patty’s being recovered.”
Jerry’s head cleared a little. Good news, but he needed to be there. Should have been there half an hour ago. How long had they been buzzing him?
* * *
He was in the torpedo room moments later. They’d already brought the UUV into the torpedo room. Only after she was secured did TM1 Yarborough and the chief begin their work. Unfastening access panels, they opened up the vehicle from just aft of the nose to where the motor compartment filled the last quarter of its length.
Once the all-important disk drive had been removed, the rest of the torpedo gang started servicing Patty. They wiped her down with a little fresh water, started a long inspection checklist, and began replacing her battery packs. The UUV’s high-power lithium-thionyl-chloride batteries filled half her length. They could not be recharged. They had to be replaced by a fresh energy section for each run. This was the main limit on how many surveys Seawolf’s UUVs could make.
* * *
It was Will Hayes’s OOD watch when they retrieved Patty, and then Jeff Chandler’s. Near the end of Jeff Chandler’s watch, the XO came into control.
Lieutenant Chandler almost snapped to attention, “Afternoon, sir. Current course two two five at five knots at one hundred fifty feet. En route to retrieve La Verne at. ”
Shimko waved him off. “Very well, Mr. Chandler.” The XO headed for the chart table. Jerry and most of his quartermasters clustered around several charts of the Barents Sea. One petty officer sifted through a stack of computer printouts while two others annotated a chart. Another was compiling a table of distances under Jerry’s direction, while one petty officer plotted Seawolf’s position and watched the fathometer.
“What do you have for me?” asked the XO.
Jerry stepped away from the chart table, picking up a small map of the area. “Patty found four spots that match the criteria we were given — bottom type and contours, depth, and the rest. We can take a closer look at them after the two-day midpatrol break. I’ve roughed out a plan to cover them all.”
He showed Shimko the small map. “I’m still working the numbers to make sure we can still reach the remaining UUV launch and recovery points as planned. Until we actually start the second set of surveys, all I can do is estimate how long each one will take.”
Shimko agreed, reluctantly. “Just give me your best guesstimate. I’ll brief the Skipper, but I need your recommendations ASAP”
Jerry glanced at the chart table behind him. “Twenty minutes, sir?”
“All right. Did Patty find anything unusual?”
Jerry gestured to the chart table behind him. “A gold mine of hydro-graphic data. I’ve got my guys working through it for obstructions, shoals, anything not on the charts.” He paused. “She also marked over thirty man-made objects. I’ve compared their locations with ones we knew about on the charts. Only a handful match. Most are new or uncharted.”
“Good. The same vessel that plants the sensors can examine those items.”
“Should we use the UUVs to classify some of the bigger ones? We can tell the vehicle to take photos and sonar images when it detects one.”
“No. A lot of that stuff is going to be old — leftovers from World War II or maybe just junk dumped out here. Besides, we have over two hundred new bottom contacts right now. We’d lose way too much time finding out which ones were worth exploiting.” Shimko smiled. “Wise man says, ‘Man who looks for noodle in haystack will be very hungry.’”
Jerry looked disappointed. Shimko reminded him, “We’ve got our own mission to finish, and I’d prefer not to poke around up here any more than we absolutely have to.”
“Yessir, I understand. I’ll have my course recommendations to you in a few minutes.”
* * *
Seawolf glided confidently over the seabed at a stately five knots. As they doubled back to the rendezvous location to pick up LaVerne, the bottom crested within five fathoms of her keel, but they were following in Patty’s path now. Jerry was confident of the data from the UUV, and his quartermasters were already adding Patty’s bottom topography data to their charts. They would leave the Barents with better charts than the Russians, at least where the UUVs had been.
The first of eight detail surveys had gone as planned. Lieutenant (j.g.) McClelland, the sonar officer, and Jerry had worked out a procedure to gather additional hydroacoustic information that they needed, while Jerry plotted their precise position. He now had almost every quartermaster aboard working in control. Either they were updating charts or plotting the detailed survey data. Jerry had to fight the urge to use the quartermaster assigned to the control room watch. Their activities took over the fire-control plotting table as well as the chart table in control. And the extra bodies made the space both crowded and stuffy.
Jerry noted and reported the proximity of several newly plotted man-made objects along their course. Patty’s navigational accuracy was precise enough to reassure the entire ship control team that they were well clear of any of them. According to his plot, the nearest object approached no closer than two thousand yards on Seawolf’s port side.
* * *
The Russian sensor buoy listened carefully as the sound from Seawolf grew louder. Its sound receivers covered a wide range of frequencies, and now it isolated tones, pulses, rhythmic sounds that were not only man-made, but fit its detection criteria. It still waited, though. It detected and classified the sounds from the intruder within minutes, but would they persist? Would they change?
They didn’t change, but grew steadily louder at a constant rate. The sounds made by Seawolf were no louder than a household appliance, but the buoy had more than enough to work with.
The buoy’s computer was smart enough to recognize this as an approaching vessel, so waited, gathering and recording sounds. Finally, the intensity began to fade, at the same rate it had increased, and the bearing rate changed dramatically. The buoy realized that the submarine was moving away. It had gotten all the information that it was going to get, and it was time to report to its masters.
It uploaded its recordings and all target data, along with a message, into a small float, one of three located at the top of the buoy. The computer verified that the surface was clear of large ice chunks, and then released a catch. The float silently shot up toward the surface.
Seawolf was several miles away when the Russian sensor buoy broke the surface and broadcasted her presence.
7. INCIDENT
4 October 2008
Severodvinsk
Barents Sea, five nm south of the Amga Buoy Line
Petrov was in the aft auxiliary machinery compartment when the summons came over the intercom: “CAPTAIN TO CENTRAL POST.” There was an urgency in the speaker’s tone, and Petrov wondered what new disaster had befallen them. There was no sign of anything amiss in the engineering plant. Chief Engineer Lyachin had just been showing him the improvised repairs to one of the motor generators, and Petrov had praised his resourcefulness.
Heading forward from the sixth compartment, Petrov used the process of elimination to try and bound the problem. The reactor and propulsion plant were both functioning within safe limits. If not engineering, then weapons? Unlikely, since they weren’t exercising those systems. Sailors saw him coming and flattened themselves against the passageway bulkheads, or ducked into doorways. The captain was in a hurry.
Sensors? Possible, he thought.
Communications? Also a possibility. Each new suggestion made him increase his pace. As he leapt through the watertight doors, Petrov clutched the red case containing his IDA-59M close to his chest. The self-contained breathing apparatus was issued to everyone on board a Russian submarine and was designed to provide fifteen minutes of breathable air. That was long enough for a person to evacuate a compartment filled with thick, choking smoke.
In the central post, Kalinin started his report as soon as Petrov came into “It’s an alert, sir-an Urgent message from Northern Fleet Headquarters. I’ve ordered the boat to communications depth. Sonar reports no contacts.”
Petrov’s anxiety quickly changed to curiosity, mixed with impatience. He thought, “I hope it’s something other than a drill this time.”
There were several levels of importance or precedence used in fleet messages. “Routine” messages were the administrative trash that he and the rest of his officers plowed through every day. “Priority” messages concerned fleet operations, and were handled quickly, if the communications commander wanted to keep his job. “Urgent” messages had to be passed instantly. If America attacked, the fleet would be warned by an Urgent alert message.
The cautious Kalinin, like any good starpom, would not usually have maneuvered the boat without permission from his captain, but this was an exception. With an alert message, there could be no delay. Minutes might count. Petrov nodded his approval of Kalinin’s actions and asked, “Is Mitrov ready?”
“Yes, comrade Captain. He’s in the communications post and will keep us appraised.”
Petrov watched the depth gauge rise. They’d been loitering near the edge of the sea ice, a hundred meters down. At that depth, Severodvinsk had to trail a long wire antenna to receive any signals at all, and they were limited to simple one-word codes — like “Alert!” That was the tradeoff with extremely-low-frequency communications. A submarine could receive messages at deeper depths, but they were incredibly short owing to the low bandwidth — little more than a “bell ringer” telling a boat to make contact. They’d received just such a message, calling them toward the surface where they could receive a more detailed message using a faster system.