The target position established, the torpedo began its final arming actions, preparing the high explosive’s fuse for detonation. The targeting program called for another data point, the sonar transmitter complying with another loud ping. The target was now at one point five kilometers. A software interlock closed a contact in a relay of the fuse’s arming circuit, preparing the system to detonate with the last signal in the circuit: the proximity magnetic sensor. The target’s wake from its large-diameter propeller began to buffet the torpedo, its signal to dive to a slightly deeper depth to avoid the screw vortex and get under the target’s hull amidships. The roar of the screw ahead and the turbulence of it became more violent. Another ping, another range. Less than a kilometer now.
The target was too close to ping a pulse and get a meaningful return. The sonar switched to a ramp transmission, a police-siren sound going slowly from a deep pitch to a high-pitched wail, then dropping down to the low pitch. The receiver was able to get the return from the target at the same time the transmitter put out the signal. The range closed to 400 meters, shrank rapidly to two shiplengths, the target screw vortex pounding the Nagasaki with turbulence.
The torpedo drove on, closing quickly, in the last seconds of its life.
Senior Chief Sanderson’s face was blotchy red as it tended to be when he was angry — which he now was — or scared— which he also was. He tried to keep his voice steady as he made the report that he considered his last.
“Conn, sonar, incoming torpedo has switched active sonar to a continuous ramp pulse. He’s inside a thousand yards and still closing.”
“Conn, aye,” Kane’s hurried voice replied.
Sanderson reached to pull off the sonar headset, thinking the torpedo explosion would deafen him, then figured it didn’t matter … he’d be dead before he heard the detonation.
Aft, in the control room. Commander Kane spoke on the phone, his voice rushed and loud, no longer showing his trademark cool.
“Eng, open your throttles wide, I don’t care if the mains fly out of the fucking casings, and do it now!”
The hull vibrations increased suddenly to a violent shaking as the screw’s thrust bearing 200 feet aft lost its oil film and made metal-to-metal contact, threatening to shear off the shaft. In maneuvering, several beads of sweat ran down Tom Schramford’s forehead as he glared at the reactor power-meter needle as it climbed to 150 percent and hit the top peg, deep into the red zone, the reactor compartment’s high radiation alarm flashing on the reactor control panel. The reactor core was coming apart, he thought, the bomb-grade uranium no longer separated from the cooling water by a sheath of zirconium cladding, the clad now rupturing as the fuel elements overheated. The main engines shook hard aft, the bearings hot, the boilers now putting out steam and water, unable to deal with the huge steam demand and still supply dry steam, the water droplets impinging on the main engine turbine blades, threatening to break off a blade. And a thrown blade would blow open the casing, blast the compartment with steam and roast the men aft.
Schramford didn’t like his orders but would have done the same himself if he’d been in command. It was too loud aft with the complaining drive train to hear the sonar from the incoming torpedo, but forward in the control room David Kane’s ears were filled with the wailing knell of the weapon.
Kane had tried everything, putting the reactor in the red, running as hard as he could. He wondered if he should emergency blow to the surface, then rejected the idea. From the sonar tapes of Augusta’s sinking, he suspected that an emergency blow had been Rocket Ron’s last action, and it had not saved him. The bubbles from the ballast tanks had probably made them an even bigger target, or the blow had slowed them down.
Kane was out of alternatives. He could only wait. Sensing the eyes of the men around him, he kept his war face on: a deep frown, narrowed eyes, jaw muscles clenched. His vision of Becky’s face was starkly real. He blinked her away and looked over at the ship-control console, abstractly wondering how fast the ship could go full out. The electromagnetic log speed indicator read 42.9 knots, the last twenty percent of reactor power barely able to push them another 1.5 feet per second faster.
The torpedo’s sonar grew louder, then stopped, just before the explosion.
The Nagasaki was fifteen seconds away from detonation when the alarm was received in its upper functions from the self-check module reporting low pressure in the port and starboard fuel cells. A half-second after the alarm sounded the drive turbine began to spool down as the last drops of fuel flowed into the combustion chamber, the chamber cooling, the drag of the water almost immediately bringing the propulsor speed to windmill velocity. With the loss of the turbine, the AC and DC power generators winked out, dropping electrical power to circuits and systems across the board with minor exceptions that were supplied by the onboard battery.
The torpedo, too long in its tail chase, had run out of fuel, but even this eventuality had been planned for. There was just enough power left to complete the final relay contacts in the fuse-arming circuit, just enough consciousness remaining in the weapon’s dying brain — in an imitation of a human reflex — to order the detonation of the high explosives. The torpedo’s computer intelligence blacked out, but not before the relay in the detonation circuit clicked home and the trickle of current found the fuse, igniting it into incandescence and detonating the high explosive.
At the time the torpedo was 125 meters astern of and twenty meters below the target submarine’s screw, tantalizingly close but too far to guarantee a kill. The fireball from the six-ton explosive blew outward, the shock wave reaching far out for the hull of its intended kill.
The disruption of the ocean region where the torpedo had once been was momentary, and within seconds the violence of the explosion was replaced by bubbles of combustion gases and a shock wave expanding outward in a forceful pressure pulse, its power smashing into the aft hull of the submarine target. Although the pressure pulse was cruel, the sub’s hull was not cut in two, not ruptured, not even cracked, the high-tensile HY-80 steel holding against the stress of the pressure wave as its hammer slammed into the vessel. Had that been the end of the explosion’s effect, the submarine would have sailed on.
But hull integrity was not sufficient by itself to allow survival in an underwater six-ton plastique explosion … the pressure pulse did three things to the sub that made her survival doubtful, perhaps impossible.
The first was to blow the horizontal stabilizer surfaces upward from the blast angle, coming as it had from below. The stern plane surfaces’ hydraulics were overcome by the force of the shock wave, the force of it rotating the surfaces up on their massive hinges, the ship lucky that the stern planes were not completely torn off.
The second was to shake the ship in such a violent acceleration that the electrical breakers all opened, from the smaller scram breakers providing power to the reactor’s control rods to the main grid turbine breakers and motor generator output breakers supplying the vital loads, even the battery output breaker. As the circuit breakers were jostled open the ship’s electricity was completely lost, the reactor one of the biggest consumers of its own electrical output, the system eating thousands of horsepower in the coolant recirc pumps and the two dozen other pumps that circulated the power plant’s various fluids. It was, in effect, the vessel’s heart failure at the same time as a central nervous system shutdown, brain death.
The third result was more a response to the first effect and an aftermath of the explosion: the force that had smashed the sternplanes upward from the tail section of the sub had compressed hydraulic oil in the cylinders that pushed the stern plane surfaces, the oil returning to the air-loaded accumulators, the pressurized oil embued now with more energy than the air pressure after the explosion. The high-pressure oil set up a hydraulic pendulum, the same sort of hydraulic pendulum observed by sloshing back and forth in a bathtub, the rising water on one end inevitably bound to rush to the other end. Now that the explosive power of the detonation was dissipating, the force pushing on the stern plane vanished.