Phoenix Sub Zero

The Mark 52 torpedo was still, in effect, groggy, half-asleep as it hit the water, but the sudden deceleration jolted it into full electronic consciousness. It immediately began listening to its seeker sonar as it dived to 300 feet and turned two complete circles. Its computer had been loaded with the bearing to the hostile submarine, but targets had a nasty habit of evading once they heard the heavy splash of a Mark 52 hitting the water. The unit turned, on its first circle hearing something to the west, ignoring it to make sure there wasn’t another target closer, its electronics trained to discriminate between cheap decoys and real submarines. Now at 300 feet, the unit turned again past west and heard the target again, somewhat fainter this time. The torpedo abandoned its second circle and spun the propulsor to maximum speed while pinging with active sonar.

The return came back, solid, hard. The target was directly ahead, the range minimal. The weapon sped up to fifty-three knots and bore down on the sub, diving slightly to a depth of 450 feet, the depth of the target. As the target grew closer, the torpedo shortened the pulse-repetition frequency. It would be a short run. In anticipation, the unit armed its warhead and continued speeding toward the target.

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“Loud splash, bearing of the aircraft at one one two, sir,” Tawkidi reported, his voice level but unnaturally loud in the hushed room. “We’ve got a propulsor, definite torpedo in the water … and the unit is active and closing.”

“Reactor control, emergency ahead, maximum power to the point of nucleate boiling in the exit plenum, transfer loads to the battery and disable the overload protection in the propulsion motor breakers. Ship control, steer two six five, depth 200 meters, report speed.”

Sharef had ordered reactor control to put out maximum power short of melting down the fuel assemblies, the calculations for emergency-ahead speed predicting a speed of eighty-eight clicks. Sharef did not smile as the display wound out to ninety-three clicks, since the American airborne-launched torpedoes could do well over ninety-five clicks, perhaps even 100. Sharef continued heading west, out of the Mediterranean with its flocks of aircraft launching torpedoes and their damned sonobuoys toward open ocean and the Atlantic. The torpedo was still driving up on them but it was small. Sharef hoped that it would not harm them too badly. Still, no commander took a hit without evading. At that moment he devoutly wished for another Dash-Five evasion device.

“Commander, report status of the SCM.”

SCM was sonar countermeasures, a torpedo-deception system designed by the Japanese shipbuilders, a sort of ventriloquist sonar pulse generator built to fool an incoming torpedo and make it explode too early, the transmitters mounted in the two lower X-fins aft. The sea-trials test results on it had been inconclusive, but in a torpedo tail chase the SCM sonar received the pulse of a torpedo sonar, listened for how often the pulse came in, then on the next ping-listen cycle the SCM would transmit an identical pulse back to the torpedo.

The SCM transmission was designed to be heard by the torpedo before it heard the echo return of its own original transmission bouncing off the sub. It was simple in concept but close to impossible to make it succeed at sea. The problem that came up first was making the ship able to transmit a ping that exactly matched the torpedo’s ping, then changing it so it would sound like an echo return, adjusting the timing and frequency of the bogus echo so that the torpedo would be fooled into thinking the target was nearer, farther, slower or faster than it actually was. The system required the most sensitive receivers, the most perfect transmitters and the dedication of an entire supercomputer.

All these requirements had been worried over for years, the final hurdle for the computer. Computing resources were most at a premium during a torpedo evasion. Sensors were straining to hear another threat or locate another target, weapons systems were programming the counterfire, reactor systems were controlling the potentially dangerous core as it approached its design limits, and ship-control systems were preparing to maneuver to evade — there simply was not time or machinery to do the intense calculations needed to put out the ventriloquist sonar pulses. The Japanese, as usual, had relished the chance to solve a seemingly impossible technical problem and had installed a separate compact supercomputer tied into a new hydrophone array on the X-tails. The system was expensive and not guaranteed to work, but about half of the tests had shown impressive results.

As they ran from the torpedo, Tawkidi and Sharef had been too involved with the incoming torpedo and activating the SCM system to notice what lay ahead: the minefield of two dozen Mark 50 weapons circling and quietly waiting for the Destiny submarine.

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