The captain paused to allow his orders to be carried out, feeling a vibration in the deck as the Hood’s single screw began thrusting the vessel through the water at its maximum speed.
As the submarines speed increased the sonar reception deteriorated and with nothing to listen for in real time a leading sonarman took the opportunity to rewind the recent recording of the Xia and analyse it with a practiced ear. He knew the intelligence assessment on its speed and as that was clearly in error he sought for some clue to the secret of its true performance. A discovery came swiftly, but not to the question he had set.
Filtering out the sound of the pounding screws he listened keenly to the sound of the vessels reactor pump and then to an earlier recording.
“Captain, sonar!”
The captain approached the leading sonarman’s station where a set of headphones was offered.
“Yes, Kentleigh?” the captain placed one headphone against his right ear and enquired. “Exactly what am I listening to?”
“That’s a recording taken four days ago of the Xia with all but the sound of her reactors high pressure pump filtered out.”
The captain listened to a slow and faint noise that sounded rather like asthmatic wheezing. He nodded to the sonarman who pressed a key on the workstation in front of him. He heard a metallic click in the earpiece as the soundtracks were switched and then the same rhythmic wheeze; he listened hard and concluded that it was the same.
“Okay I’ll bite, what’s your point?”
“Sir, the second recording is only five minutes old.”
The self-discipline that the captain exercised at all times in front of the crew almost, almost, snapped. The sound of the high-pressure pump operating on a vessel travelling at only three knots could never ever sound the same as one working flat out.
“Come left to zero degrees and make your speed three knots.” He ordered before patting Kentleigh on the shoulder. “It seems that the Peoples Republic have themselves quite an effective submarine decoy which we knew nothing of before, well done.”
As Hood’s speed dropped off the sonar department sought to re-establish contact, the operators listening for some give-away noise amid the natural hubbub of the Pacific that could only be man-made.
Of the Tucson there was no trace, the US attack submarine had defeated the weapons sent against it and gone quiet, shrouding itself in silence as it began a stalk of the killer of its sister ships but she was now miles away and of no immediate assistance to HMS Hood.
They knew the Xia could not be far away, and in fact she had stopped running and launched a torpedo shaped Ghost Lamp, a pre-programmed decoy that was designed to emit sound waves that exactly mimicked its parent. The Xia had as a sensible precaution a Ghost Lamp programmed to run at their own top speed and loaded at all times in a torpedo tube where it required only the tube to be flooded and the bows doors opened. This Ghost Lamp had promptly failed, leaving a trail of bubbles behind as it sank into the stygian darkness below the boomer.
A second Ghost Lamp had been hurriedly prepared and launched, emitting an almost identical acoustic signature to that of the Xia. The Chinese weapons officer, working furiously at his console, had only moments to load the necessary sound files into the decoys memory, and he had patched and pasted quite literally the first available ‘pump noise’ file in the Xia’s sonar history library.
Xia herself had gone deep behind the cover of her noisy countermeasures and reduced her speed to a slow walk, listening with satisfaction to the western attack submarine thundering past in pursuit.
HMS Hood’s sonar department listened to the mournful pinging from west, northwest of two of their torpedoes as they swam zigzag courses in an effort to reacquire the Chuntian. They noted grimly an explosion to the north, northeast as a Spearfish silenced the Ghost Lamp that had suckered them in for a while, and they recognised the Chuntian as she headed their way at ten knots, too slow to be waking the neighbourhood but not slow enough to avoid detection by a western sonar suite. Chuntian’s solid fix on Hood’s position had faded as the British submarine lost way and her captain was desperate to re-establish contact. Coming in at ten knots would allow his own sonar operators to work whilst hopefully prompting a reaction from the Hood.
The British captain ordered another course change once three knots had been achieved, bringing the vessel right around to a heading of Two Seven Zero because he was certain that they had overshot the Chinese missile boat, but that was the only factor he was certain of.
“If you were the boomer then where would you be, Kentleigh?”
The operator took a moment to answer, consulting the details he brought up on the screen before responding.
“There’s a thermal layer another two hundred feet below us, I’d be under that by a good margin, sir.”
The captain considered it.
“Okay, and on what heading?”
“In the opposite direction to the one we were on.” Kentleigh replied.
“I’d want to get as much distance as possible between us.”
The Leading Sonarman had answered with a calm confidence and the captain decided to run with it.
“Come left again to One Nine Eight…make your depth seven hundred feet and take us there slowly.”
The Hood turned onto the ordered heading even as she sank away from the light of the surface above her. She had not reached the required depth when the sonar department reported again.
“Captain, sonar…aspect change on the Chuntian, now making turns for twenty eight knots.”
“Range, bearing, course and depth?” he asked.
“Sorry sir we are in the layer now so there’s nothing consistent on the panel.” The captain understood, the thermal layer made accurate sonar readings impossible on anything on the opposite side.
His Number One stepped close, speaking in a low voice so as not to distract the crewmen’s concentration.
“What do you think sir, she can’t have heard us?”
“No I don’t think so, although I think her sonar suite is an awful lot better than intelligence gave it credit for I reckon she is dangling herself as bait to try and tempt us into launching on her, thereby giving away a position that she and the Xia can both launch on.”
“And if we don’t fire on her…” his Number One mused. “….they get to close the engagement range, considerably.”
The captain nodded in agreement and spent a second longer in thought before reaching a decision and clapping his second in command on the back.
“There is another course of action we can take that they don’t seem to have considered though.”
“Sir?”
“We are resigning from the Silent Service, forthwith.” He laughed at his Number Ones expression and then turned to address the control room.
“In a few seconds we will be below the thermal layer, I want the Spearfish in tubes one and two readied for shots at the Chuntian and three for a snap shot at the Xia…the Spearfish in tube four will also be for the Xia once a proper solution is worked out…so let us take advantage of the layer while we have it and open bow doors.”
Behind him the Weapons Officer instructed the Torpedo Room to flood tubes one, two and three and open the outer doors. All eyes were on the captain, whose own were directed at the sonar operator he was stood beside.