Voyage of the Devilfish

“Captain, range to the ice raft ahead is nineteen-hundred yards by SHARKTOOTH sonar.” Lieutenant Commander Christman, Officer of the Deck, stood at the underice sonar, the SHARKTOOTH, a console with a joystick and a vertical video readout. At the top panel was a stripchart used to record the depth of the ice overhead. The display on the center panel looked very much like a radar, was generated by a hydrophone on the forward edge of the sail that transmitted a faint high pitched tone in a pattern like a police siren. If the sound pitch was plotted against time on a graph, the waveforms looked like shark teeth. With the changing transmission frequency, it could transmit and interpret the echo simultaneously, giving continuous ranges and bearings to ice-shapes ahead, which now formed a solid bank less than a mile away. For a moment Pacino had a sense that this might be the last time he would see the surface and the sky and the sun… not an unheard of thought among submariners… and quickly censored the thought as he snapped the periscope grips up and rotated the hydraulic control ring. As the scope optic-module descended into the well the stainless steel pole felt extremely cold brushing Pacino’s arm.

“Take her deep,” he said without looking at Christman, then moved forward on the periscope stand to the pole of the number-one periscope, the World War II relic used only for surface navigation, and stared at the Conn sonar console on the port side. The TV screen was red to keep the OOD’s eyes night-adjusted. The display was a waterfall cascading downward. The horizontal axis was bearing — north on the left, south in the center and north-northwest on the right. The vertical axis was time — the top now, the older data lower. All the data fell downward on the screen like a “waterfall.” Like the moon “following” a moving car, a distant contact would show up as a vertical trace on the display, its bearing constant, but a close contact would have a slanted slope, showing it moving from one true bearing to another. At the moment the displays were only filled with static. Then a definite sloping trace appeared on the short-duration display. High-bearing rate, a close contact. Pacino reached for the microphone.

“Sonar, Captain, report the contact at zero four zero.”

“CONN, SONAR, AYE, CONTACT NOW BEARING ZERO SIX TWO IS BIOLOGICS.”

Pacino frowned. A whale or a school of fish.

“Sonar, Captain, select the narrowband beam on the trace’s bearing and integrate on narrowband time-freq.”

“CONN, SONAR, AYE.” Pacino pressed a selector-pad button below the display. The waterfalls disappeared, replaced by six graphs, each a plot of intensity on the vertical axis versus sound frequency on the horizontal axis. Fed by the towed array, the narrowband processors listened for specific frequencies known to be emitted by most Russian submarine classes, from such as their turbine-generator resonance, a 300-cycle-per-sec- and sound. One of the graphs was centered on the anticipated 300-hertz tonal. If the contact was a Russian there was a high probability it would get a narrow vertical spike centered near 300 hertz. The time-frequency data took about five minutes to come up with a meaningful display. Like the camera taking an evening-time exposure photograph, the sonar system “integrated” the sound data over a long-time period to make sure tonals weren’t just background noises. For a full five minutes Pacino stared at the 300-hertz graph, not aware of Christman staring at him. The graph was flat. No spike anywhere near 300 hertz. Pacino shook his head, pushed a button on the selector pad and the broadband waterfall display returned.

“Sonar, Captain, return to your search.” The trace had definitely been biologies.

“CONN, SONAR, AYE.” The short-duration display began to fill with traces. Noise from rafts of ice shifting and grating against each other. Soon it would be audible to the naked ear. Pacino moved through the gap between the port Conn console and the aft telephone-communications bulkhead, squeezing past the radar console, which was shut down and useless when submerged. On the other side of the radar was the SHARKTOOTH underice sonar. Pacino looked down at the forward scan screen. The ridge of ice was now astern, and ahead were some more ridges, stalactites of ice hanging down from the ice canopy overhead. Just gentle ridges now, but soon they would stab down deeply enough to smash into them if the OOD made a mistake. Dimly Pacino heard Christman giving slight rudder adjustments to avoid the ridges. For the rest of their time under ice the OOD or his assistant, the Junior Officer of the Deck, would stand here at the underice sonar steering the ship. The JOOD would also help with underice navigation or man the firecontrol computer, ensuring a weapon was programmed and ready. In case.

“Offsa’deck, clear baffles,” Pacino ordered. “And don’t go more than two hours without a baffle clear. I don’t want to be surprised out here.”