Friday, November 20, 2015

THE SILENT SUB CHAPTER 17 - NOISEMAKERS

USS JAMES SMITH
Lt. Commander Denning was on the bridge of the USS James Smith, coordinating the search. USS James Smith and USS John Johnson had been using an expanding-box search pattern. Basically, they sailed on opposite sides of a square box pattern and expanded the size of the box with every rotation. At this time, however, with no sign of the u-boat, they either had to abandon the search or use a different search pattern.

After a submarine attack, surface warships usually have to consider two possibilities: the u-boat is sailing away or staying around to attack again. German submarine captains were notoriously brave and willing to take risks, which means there was a high probability this one was just biding his time, waiting for another opportunity.

Denning had lookouts all over the rails looking for a periscope, snorkel, or even the actual submarine. Denning's ship also had a centimetric radar, a type of radar that was capable of detecting the small periscope stub when it was raised above the water.


U-1215
The periscope broke the surface of the water approximately 2000 meters away from USS Buzzards Bay. The aircraft carrier was just visible in the last sunlight of the day. The two destroyer escorts that had been hit were no longer in sight. They had sunk earlier. Werner listening in to the sonar sounds of the sinking vessels. The carrier had actually made some noise earlier in their attempt to restart the boilers but it was now quiet again. They would have to fire a straight running torpedo at her.


USS JAMES SMITH
"Skipper!" A junior officer called Lt. Commander Denning. "Radar has detected a periscope bearing 284 degrees, 4200 yards, on course 248."

Denning ordered the ship turned around and a message sent to USS John Johnson and USS Buzzards Bay. He went to the plotting table and swore. The u-boat was heading for the aircraft carrier.


U-1215
"Captain!" the sonar chief shouted from the sonar room, "The two destroyer escorts are heading this way!"

"Damn!" Werner whirled toward Fischer. "Set it up, we can't wait any longer. Fire Tube 6 on the aircraft carrier using the bearings from the periscope observation and use Tubes 1 and 2 on the destroyer escorts. Set the activation distance of Units 1 and 2 to five hundred meters. Let the torpedoes find their own targets."

Werner checked the periscope again and refined the bearings. Fischer used the bearings, the speed and course of U-1215 to calculate a course and time to launch for the torpedo. The next two torpedoes were fed the same bearings from sonar's reports. Then he straightened.

"Firing solutions set, Captain. Tube 6 will have to be fired in 44 seconds. Tubes 1 and 2 can be fired anytime."

Werner didn't waste any time. "Launch Tubes 1 and 2, now. Set the timer on Tube 6 and fire when the timer runs out."

U-1215 used a hydraulic ram launch system. It was less noisy and simpler than the compressed air launch system that most submarines used. Both systems, however, produced noise when flooding the tubes in preparation for opening the outer doors. This couldn't be helped and Werner knew it. He only hoped that the silent torpedo would confuse the warships' sonar operators.


USS BUZZARDS BAY
Buzzards Bay's sonar operator's eyes widened at the familiar sound of tubes flooding. He immediately informed his superior who informed the captain. Bennet immediately got on the radio.

"Bulldog, Doberman, this is Doghouse. Torpedo launch warning!" Bulldog was USS James Smith while Doberman was USS John Johnson. Both were running at maximum speed toward U-1215's periscope and would be unable to hear the torpedo launch.

Lt. Commanders Dennning and Gonzales, skippers of James Smith and John Johnson respectively, both gave the same order to their ships.

"Launch Foxer!"

Foxer is the name for an anti-torpedo device. It was basically a noisemaker that was pulled along by a vessel to decoy acoustic torpedoes. It made a lot more noise than the vessel pulling it and was quite effective in achieving its purpose. The two destroyer escorts had to slow down to 14 knots, however, as the device tended to fall apart when running at faster speeds.

Both Admiral Brown and Captain Bennet watched as the two destroyer escorts turned so they would be running perpendicular to the approaching torpedoes and give Foxer a better chance of decoying the torpedoes. USS James Smith ran north while USS John Johnson ran south.


U-1215
Blöhme swore when he heard the noisemakers. He immediately informed his superior who informed Werner. The acoustic sensors on the torpedoes were the same as the ones used in other torpedoes. Foxer had fooled those types so there was no reason why U-1215's torpedoes would not be fooled. Still he was banking on the silence of the torpedoes to cause the destroyer escorts to make a mistake.

The torpedo (Unit 6) for the aircraft carrier was already on the way. Its seeker head was set to activate at maximum distance. This meant it was not going to activate before it hit the carrier. With all the noise the two destroyer escorts were making, the torpedo might turn around and go searching in the wrong direction.

Unknown to Werner, Unit 6 had a flaw. Its seeker head had gone out of calibration and was set to activate after only 100 meters. It had turned immediately upon activation and headed for the two destroyer escorts. Being silent was an advantage only for the torpedo. Blöhme and Schmitt never heard it make the turn.


USS JOHN JOHNSON
Lt. Commander Raul Gonzales was querying the sonarman on what he'd been hearing. Prior to launching Foxer, the operator had tried to track the approaching torpedo.

"I didn't hear anything, Skipper," the man said. "No high-speed screws, no nothing. He might have been trying to spook us, trying to get us to use Foxer."

But why? Gonzales asked himself. It was a worrying thought. Foxer was good at decoying acoustic torpedoes but there were those few times when the torpedo had locked onto the warship instead of the noisemaker. Gonzales wondered if he should stop or cut the cable that was pulling Foxer.

No, he thought. Foxer has been successful more times than failed. Our chances are better with it.


UNIT 1 AND 2
Unit 1 and 2 had activated as programmed and had detected four noise sources. Two were loud while two were fainter. Their controls selected the loud ones and steered for them. Unit 1 had turned to follow USS James Smith while Unit 2 had acquired USS John Johnson.


USS BUZZARDS BAY
"There's nothing, Skipper." Buzzards Bay's sonarman was having the same problem as USS James Smith. He had been listening for the high pitched screeee of the torpedoes screws as they spun. He could clearly hear the two noisemakers along with the almost faint sound of the destroyer escort's own screws but the sound of torpedoes running in the water was eerily absent.

"Are you sure you heard tubes flooding?" Bennet asked.

"Yes, sir," the man answered. "It was one of things they made you listen to over and over again in sonar school."

Bennet thought it over for a few seconds and came to a conclusion.

"He's flooded his tubes and caused James Smith and John Johnson to deploy Foxer. Their sonar is useless with Foxer operating (because of the noise), which means they can't find him."

"But I can't hear him either, Skipper," the operator complained, fiddling with his controls. "He's probably drifting with his motors off."

"Can't be," the sonar boss countered. "We haven't heard anything since the attack started. Do you think he's had his motors off all this time? Besides, we've detected his periscopes in two places, both too far from each other for a sub running underwater."

Bennet suddenly came to a realization. "We've got two submarines here."


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