Phoenix Sub Zero

Soon the target was within two kilometers, the range determined by driving a slight wiggling course to see how the bearing to the target reacted. The short range caused the targeting functions to activate the unit’s sonar set—passive listen-only sonar was fine for pursuit of a loud contact but not good enough for the exact placement and detonation of the six metric tons of shaped-charge plastic explosive in the warhead. If the torpedo attempted to hit the target with passive search sonar, with this high closing speed, it could experience a bearing error that would cause the unit to go sailing past the target and have to turn around and continue the chase. The active echo-ranging came on, illuminating the sea around it with a powerful medium-pitched sonar pulse, transmitting the pulse at power high enough to generate steam vapor bubbles at the nose cone. After the pulse the torpedo went silent and listened for the return, which came back a fraction of a second later, the sound distorted by the target submarine’s rotating screw, the frequency downshifted to a deeper pitch by the target’s motion away from the sonar pulse. The target position in the computer’s mind needed to be adjusted slightly, the range a bit farther than the torpedo had originally thought.

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.

USS PHOENIX

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 earsr were filled with the wailing knell of the weapon.