Inside the Marginal Ice Zone, Kazan maintained her steady trek north at ten knots while Plecas monitored the ice-detection sonar, topsounder, and bottomsounder. Thus far, the topsounder had detected only sporadic chunks of sea ice floating above them, while the bottomsounder reported the smooth, shallow bottom of the Barents Sea, which averaged only 230 meters in depth.
Plecas, however, was more interested in what the American submarine was doing. He glanced at the navigation table, which displayed the tracks followed by both submarines over the last day. The American crew had detected each of Kazan’s baffle clearance maneuvers and calculated its new courses and speeds exactly. They were well trained, which was not an unexpected revelation.
What was revealing was that the American submarine was matching Kazan’s movements exactly, mimicking them. That, combined with no high-frequency pings from the American submarine, indicated they were not using their under-ice sonar; they were relying on Kazan to show them the way.
Perfect.
As Plecas prepared to implement his plan, his thoughts shifted to his submarine’s ice-detection sonar. Objects in front of them would appear as a colored blotch, with different colors representing the intensity of the sonar return, with red indicating a large, deep, or dense formation. Unfortunately, ice-detection sonars weren’t very good at determining the depth of the object, which is what ultimately mattered. The color of the ice was the key. As Kazan closed on the object, shallow ice keels would recede upward and exit the top of the ice-detection beam. As it receded, the color would change from bright red to darker, cooler colors until it faded to black.
The ice-detection sonar used the submarine’s depth and a simple geometry algorithm to determine if the obstacle was a threat. If the ice didn’t change from red to another color within a certain distance—the Minimum Allowable Fade Range—it was deep enough to present a threat, and Plecas would have to turn or go deeper. The display was currently black; there were no ice formations ahead.
As Kazan continued north, small icebergs were sporadically detected, none deep enough to cause concern, until a bright red blotch appeared on the display, twenty degrees to starboard.
The ice-detection sonar operator announced, “Hold ice keel, bearing zero-two-zero, range twelve hundred meters.”
Plecas ordered, “Steersman, right standard rudder, steady course zero-two-zero.”
As the Steersman complied, Fedorov approached. “Captain, you’ve turned directly toward the iceberg.”
“I understand, First Officer.” Plecas said nothing more until Kazan steadied on her new course. He then ordered, “Steersman, ahead full.”
The Steersman rang up the new speed order, and Kazan surged toward the iceberg.
“Possible contact zig, Master one, due to upshift in frequency.”
Lieutenant Bob Martin, on watch as the Junior Officer of the Deck and head of the Section Tracking Party, made the report to Commander Buglione. While they were trailing another submarine, Buglione had augmented the normal watch stations with the Section Tracking Party, comprising an additional fire control technician to monitor the plots, a Contact Manager, and a Junior Officer of the Deck.
Martin moved behind the Plots Operator and examined the contact’s tonal on the display. After studying the frequency change and noting a right bearing drift, Martin announced, “Confirm target zig. Master one has turned to starboard. Set anchor range at five thousand yards.”
Shortly after Kazan steadied on her new course, the Plots Operator reported, “Possible contact zig, Master one, due to downshift in frequency. Contact is either turning away or increasing speed.”
The Section Tracking Party repeated their analysis, concluding Kazan had increased speed to twenty knots.
Buglione examined the new solution on the nearest combat control screen. A twenty-degree course change was understandable—perhaps they had detected an ice formation ahead. But why increase speed to twenty knots? Had they detected Pittsburgh, and were opening range in an attempt to lose them?
Pittsburgh needed to match Kazan’s speed, or they would lose contact.
“Helm, ahead full. Make turns for twenty knots.”
One thousand meters to iceberg.
Plecas remained focused on the ice-detection sonar display as the operator called out the distance to the iceberg.
“Captain, what are you doing?” Fedorov asked. “We will smash into the iceberg in ninety seconds if we do not maneuver.”
Plecas turned to his First Officer, answering Fedorov’s question with a question of his own. “How have the American crew’s tactics changed since we entered the Marginal Ice Zone?”
Fedorov answered, “Instead of following us with an offset to starboard, they are now directly behind us.”
“Why?”
“Because they are not operating their under-ice sonar, so they don’t give their presence away. They are using us to chart a safe path through the Marginal Ice Zone.”
“Exactly,” Plecas replied.
“I do not understand your plan,” Fedorov said. “I realize the American submarine will follow us toward the iceberg, but they will turn away at the same point we turn away, avoiding the iceberg as well. What will we have accomplished?”
Eight hundred meters to iceberg.
“We have also increased speed,” Plecas said. “Why?”
Fedorov pondered Plecas’s question, unable to determine the answer. Regardless of Kazan’s course and speed, when they turned away, the Americans would detect the maneuver and also turn away at the same spot.
“I do not know,” Fedorov answered.
“You will understand once we slow.”
“When will that be?” Fedorov glanced nervously at the sonar display.
Six hundred meters to iceberg.
Plecas answered. “When we first detected the American submarine, you wanted to shift to the electric drive, reducing our sound signature so they could not follow us. I said then was not the right time. Remember?”
Fedorov nodded and Plecas continued, “Now is the right time.” He turned to Captain Lieutenant Urnovitz. “Shift to electric drive.”
Urnovitz relayed the order to the Engine Room as Plecas checked the clock. The seconds counted down as Kazan sped toward the iceberg.
Four hundred meters to impact.
Fedorov glanced again at the rapidly closing red blotch on the ice-detection sonar. “Captain—”
A report came across the Command Post speakers, interrupting Kazan’s First Officer. “Command Post, Engine Room. Propulsion has been shifted to the electric drive. All main engine machinery has been secured.”
Plecas responded, “Steersman, hard left rudder! Steady course two-nine-zero!”
“Conn, Sonar. Loss of Master one.”
“Sonar, Conn. Aye.” Buglione examined the Sonar display on the Conn. He expected to see the tonal fade, indicating Kazan had pulled too far away to be detected. Instead, Master one’s tonal had abruptly disappeared.
Lieutenant Reese, the Officer of the Deck, also noted the sudden disappearance. “They must have secured whatever was producing the tonal.”
This was bad news. Kazan had been their beacon, charting a safe course through the Marginal Ice Zone. Buglione had two choices: activate Pittsburgh’s under-ice sonar, giving away their presence, or close the gap on Kazan to regain contact. After a moment of indecision, he chose the latter.
He picked up the microphone and selected the 7-MC. “Maneuvering, Conn. Make normal full turns.”
The Throttleman in the Engine Room opened the ahead throttles and Pittsburgh surged forward.
Buglione studied the narrowband display, looking for the reappearance of Master one’s fifty Hertz tonal. After closing the gap at ahead full for several minutes, there was still no sign of Master one, and Pittsburgh was approaching the point where Kazan disappeared from the display. Pittsburgh was barreling forward, and there was no guarantee the path ahead was safe.
Buglione decided to slow as he evaluated his options. “Helm, ahead two-thirds.”
As Pittsburgh slowed, Petty Officer Alex Rambikur, seated at his console inside the Sonar shack, was listening to the audio output from the spherical array sonar.
“Sonar Sup, I’m hearing an unusual noise. Like someone dropped an Alka-Seltzer tablet into the water.”
The Sonar Supervisor replied, “Let me listen.”
Rambikur transferred the headphones to Chief Bob Bush, who pressed them against his ears. Unlike Rambikur, who had never been on a Northern Run, Bush had made several, and immediately recognized the fizzing sound created when an iceberg melts, releasing tiny, pressurized air bubbles trapped in the ice.
Bush grabbed the microphone. “Conn, Sonar. We’re picking up a bergy-seltzer on broadband. It’s close. I’ve never heard one this loud before.”
“Helm, all stop,” Buglione ordered.
He turned to the under-ice sonar operator. “Energize the High Frequency Array.”
The monitor flickered to life. A huge patch of red appeared on the display, directly ahead at a range of five hundred yards, barely four ship-lengths away.
“Helm, back emergency!” Buglione shouted. “Hard right rudder!”