“Firing-point procedures,” he said, voice low and tight.
“Tube one. Target One, passive circler, ten thousand yards…”
The Kaliningrad had had no accurate range at the time of launch so the Magnum swam out the bearing line toward the aimpoint — the point that the target, hull number 666, was expected to be at expected detonation time, ten minutes after launch. The Magnum was using its active sonar to ping and “listen,” attempting to pick up the enemy. Its program codes had been modified by the underice subroutine. Normally the sonar would ping and pay attention to any solid return ping, but since this action was happening under the icecap, the ice rafts and pressure ridges and stalactites would return a ping as well as an enemy submarine. The subroutine instructed the Magnum to use the doppler filter, the device that rejected stationary objects and only examined moving ones. When a ping went out from the torpedo, return pings at the same frequency were disregarded. Only pings with an upshift or downshift in frequency passed through the filter since a moving object physically changed sound waves. If it moved toward the listening ear, the object’s speed compressed the sound waves — and the frequency went up. Motion away rarefacted the waves, shifting their frequency down. Like a moving train’s whistle would be shrill and high-pitched when the train approached, low-pitched and fading when the train went away. So the torpedo “listened” not for return sonar pings, which would be ice dumbly reflecting the sound, but for pings higher or lower pitched than emitted by the nosecone transceiver. But oddly, none of the return pings passed the doppler filter. None were upshifted or downshifted. Nothing but false returns from the ice.
The torpedo was stumped. It was now 17 kilometers from the Kaliningrad, and the range to the enemy, the 666, had probably been much less at time of launch. The next line of coded instructions told the Magnum to continue to a range of 20 kilometers from its launch point, and if there were no hints of the target, to execute the default-turn-back and run until it either found the target on the return vector or reached a point 10 kilometers from the launch point.
Twenty kilometers from the launch point the Magnum torpedo gave up. It had been unable to find the target and it was time to turn back and execute its nuisance-explosion. In response to its program, the Magnum ordered its rudder over five degrees, made the 180-degree turn in less than a minute and headed back and east toward the launch point. After 14.5 kilometers of backtracking without a sniff of the target, the Magnum initiated the arming of the nuclear warhead. It was, so to speak, resigned if disappointed. It would have been much more fulfilling to have detonated mere meters away from the 666. But at least its detonation 10 kilometers from its launch point would do some harm to the target. With the arming sequence begun, the Magnum had no thoughts about what would happen to it in the moments following the nuclear detonation. Like a human driving toward orgasm, the torpedo was a highly goal-oriented being. The only thing in its “mind” was getting to its detonation position and exploding. Never mind the aftermath.
The Mark 50 Hullcrusher torpedo in Devilfish”s tube had been waiting a long time. For over two hours its gyroscope had been spinning, its central processor had been awake and the fuel lines had been pressurized. It had been programmed with the solution to Target One ever since the target was acquired fifteen minutes earlier. Every few minutes the solution to Target One had been updated, making the Hullcrusher hypersensitive to Target One’s every move. The outer door of the tube was open. The small clearance between the tube and the torpedo was filled with water at outside pressure. The water had heated up, from the the nosecone, home to the flat sonar transducer, was cold, feeling the water temperature outside the ship. When a slight electrical signal came down the guidance wire at the torpedo’s stem section, the weapon “tensed.” The signal was the final target solution update, now locked in, as the control room fire-control console’s SET key was pressed. A locked-in solution meant that launch was less than a minute away. The torpedo was ready.
“Ship ready!” Stokes called out.
“Solution ready,” from Scott Brayton.
“Weapon ready,” from Bahnhoff. Pacino paused. This was unprecedented, firing on a target without having sonar contact on it. Yes, this was a recipe for a miss, particularly under ice. But better to try and miss than sink with a full load of torpedoes. Pacino made up an order.
“Shoot on last sonar bearing.”
“Set!” from Brayton on Pos Two.
“Stand by!” from Bahnhoff on the firing panel, taking the trigger to STANDBY.
“Shoot.” Pacino felt a shot of adrenaline.
“Fire.” Bahnhoff pulled the trigger to FIRE position. Without the usual underway noises of ventilation and SINS navigation system, the torpedolaunch sounded more violent than usual. The pressure-pulse hurt twice as much. Pacino forced a yawn to clear his abused eardrums from the pressure. Something about a warshot that made the launch sound different — this time the noise meant business.
“Tube one fired electrically. Captain,” Rapier reported.
“Conn, Sonar,” the sonar chief reported on the headphone circuit, “ownship unit, normal launch.”
On the Hullcrusher’s port flank a relay opened as tube external power turned off. The torpedo was now on internal power, no longer dependent on the tube or the mother ship.
As the connector separated, the prongs of the “in-water” sensor shorted out, and the sensor completed the first of several arming safety interlocks. The torpedo “heard” the sound of water flowing, just for a moment… it was the pressurized water from the torpedo-tube tank pouring into vents at the aft end of the tube to push it out of the ship. The torpedo underwent a powerful acceleration, like falling through a dark tunnel at supersonic velocity. The noise of the sudden flow was deafening.
Would the torpedo “hear” its target? Behind the torpedo the guidance wire streamed out of one of the fixed vanes of its propulsor, and also out of the ship’s torpedo tube. The wire would remain stationary… the ship had a length of wire that allowed it to maneuver… and the torpedo let out its own wire to allow it to move. The wire allowed the weapon to be steered if the mother ship had a better fire-control solution. It also carried transmissions from the weapon to the firing ship when the torpedo had a valid detect on the target. The firing ship could tell when the wire became disconnected from the torpedo — which was usually an indication that the weapon had hit the target and exploded. As the torpedo tube and the Devilfish faded away astern of the weapon, a second safety-interlock contact shut the three-g accelerometer, confirming the launch. The three-g contacts completed a circuit to a grain-fuel canister next to the combustion chamber. The grain fuel then ignited, pressurized the chamber and brought it up to the fuel’s ignition temperature. As the temperature rose, the self-oxidizing fuel was injected and ignited, the turbine of the engine began to spin, already windmilling at 20 RPM — and the engine-rotor accelerated to transit velocity…
“Firing-point procedures,” Pacino said, “tube two. Target One. Set for passive circler, range 15,000 yards. ASH disabled.”
“Ship ready,” from Stokes.
“Solution ready,” from Brayton.
“Weapon ready,” from Bahnhoff.
“Shoot on last sonar bearing!” Pacino ordered.
“Set!” Stokes said.