“Helm, ahead flank! Hard right rudder, steady course one-eight-zero. Launch countermeasures.”
Michigan was still at high speed and it didn’t take long to turn to the evasion course. Wilson listened for the reports of torpedo decoy and jammer launches, then focused on the enemy submarine. Unfortunately, they didn’t hold it on sonar and had no idea where it was or where it was headed, except that it had launched its torpedo from the east.
“Quick Reaction Firing, tube Two, bearing zero-nine-zero!”
Lieutenant Commander Patzke tapped one of the fire control technicians on the shoulder, who entered the ordered bearing.
Patzke announced, “Solution ready.”
The Weapons Officer followed. “Weapon ready.”
“Ship ready,” Lieutenant Cody reported.
“Shoot on generated bearings,” Wilson ordered.
The torpedo was impulsed from the tube, then turned east. It was a shot in the dark, aimed at where the enemy submarine had fired from as opposed to where it was headed, but it would have to do. Wilson focused again on the incoming torpedo. The red bearing lines were stacking on top of each other. The torpedo was on an intercept course.
“Helm, hard right rudder, steady course three-zero-zero.”
Wilson turned away from the incoming torpedo, reversing course to the northwest. As long as the torpedo hadn’t acquired Michigan or it wasn’t steered toward them, they’d escape. After Michigan steadied on its new course, the torpedo bearings drew steadily aft on the submarine’s starboard stern. Then the bearing drift halted.
“Damn it,” Wilson muttered. The torpedo had been steered back toward them. It was unclear how far away the torpedo was, but the rate at which it drew aft before it steadied indicated it was close and would acquire Michigan soon. Drastic action was required, beyond another course change.
Wilson glanced at the sound velocity profile recording by the Ship Control Panel, which reported the speed of sound as it varied by depth. During Michigan’s last trip to periscope depth to retrieve the SEAL RHIB, they had passed through a strong thermal layer, with its lower boundary at two hundred feet.
The thermocline was a thin layer of water where the temperature transitioned rapidly between the warm surface heated by the sun and the cold water beneath. Submarines used thermoclines to their advantage because the rapid temperature change bent sound waves as they traveled through the layer, reflecting the sound back toward its source like light reflecting off a window. Depending on the frequency and angle of the sound wave, some tonals wouldn’t make it through. If Michigan could pass through the layer before the torpedo acquired, they’d have a chance.
“Dive, make your depth nine-zero feet. Use thirty up.”
Wilson ordered Michigan shallow, placing the sail only fifteen feet from the surface. The massive stern planes rotated, tilting the submarine until a thirty-degree up-angle was achieved. With Michigan at ahead flank, the submarine shot toward the surface.
The Dive called out the depth change in one-hundred-foot increments, ordering a zero bubble as they passed through two hundred feet, hoping to arrest Michigan’s ascent at the ordered depth. The deck leveled off as the submarine passed one hundred feet, with the keel settling out at ninety feet as ordered.
Wilson monitored the water temperature as his submarine came shallow. There was a strong thermal layer, but there was no way to know if the gradient was sufficient without running sound-velocity profiles on the submarine’s computers. There wasn’t enough time.
“Helm, all stop.”
The Throttleman in the Engine Room shut the ahead throttles, and the screw coasted down. Now that they were shallow and at a lower sea pressure, the submarine’s screw would cavitate when spinning at ahead flank, serving as a beacon to enemy sonars. Wilson had traded speed for silence, hoping the torpedo passed beneath the layer without detecting them.
The first indication was positive; Sonar lost the torpedo after Michigan passed through the layer, which meant the torpedo engine sound waves were bending back down. Whether the torpedo’s sonar would penetrate the layer and detect Michigan was unknown, however.
As Michigan’s speed bled down, Wilson calculated how long before the torpedo passed beneath them, using a worst-case range for the Russian torpedo shot. He checked the clock and when it approached the predicted time, he listened for Sonar’s report that they had regained the torpedo, which would’ve been bad news; it’d mean the torpedo had followed Michigan through the layer.
The time passed and there was no Sonar report. Wilson waited another minute, then another. Michigan coasted to a halt, hovering at nine-zero feet.
Wilson was confident the torpedo had passed beneath them, so he stepped from the Conn and examined the geographic display on the nearest console. Wilson’s best guess, based on the torpedo launch transient and subsequent maneuvering, was that the Russian submarine was still to the east. That meant it would head west to regain Michigan. If the layer was strong enough, Wilson would have a nice surprise for the Russian captain.
“Helm, ahead two-thirds. Hard right rudder, steady course zero-nine-zero. Sonar, Conn. Prepare to deploy the thin-line array.”
As Michigan turned toward the Russian submarine, Wilson briefed his crew.
“Attention in Control.” When all eyes were on him, he continued. “We’ve got a strong layer beneath us, which we’ll use to our advantage. The Russian captain will likely head west in an attempt to regain contact, but we won’t be where he expects us. We’re heading east, and if things work out, we’ll pass over him, then shoot from behind.
“We’re going to deploy the thin-line array, letting it drop through the layer so we can get a look at what’s going on below us. Hopefully, the Russian won’t poke his head above the layer looking for us. But if he does, we’ll shoot him in the face. Any questions?”
There were none, so Wilson announced, “Carry on.” He then addressed the Weps. “Weapons Officer. Reload and make tubes One and Two ready in all respects.”
Sonar reported they were ready to deploy the thin-line array, and it was soon trailing a thousand yards behind Michigan. Wilson checked the array scope — its trailing distance — against ship’s speed, verifying it would droop through the thermal layer, but not drag on the sea floor.
“Conn, Sonar. Hold a new towed array contact, designated Sierra two-nine, bearing one-zero-five, classified submerged. Analyzing.”
Wilson announced, “Designate Sierra two-nine as Master two. Track Master two.”
The Fire Control Tracking Party went to work, focused on generating a firing solution. While they worked on the target’s course, speed, and range, Sonar provided additional information:
“Conn, Sonar. Master two is classified Improved Kilo class, traveling at high speed.”
“Sonar, Conn. Aye,” Wilson replied.
The Russian captain had increased speed, most likely using a sprint and drift tactic to rapidly close on Michigan, slowing on occasion for a detailed sonar search. During the high-speed sprint legs, the Russian sonar would be impaired and the submarine would remain deep so its screw didn’t cavitate. Both of these factors played into Wilson’s plan.
The XO announced, “I have a firing solution.”
The Kilo was traveling at twenty knots, due west. The Russian submarine wouldn’t pass directly beneath Michigan, but close enough. The contact’s rapid closure, then opening, would result in an even more accurate solution.