“Can we get the bearing and range of the wreck from our present position?”
“Yes, Sir, I think so. Surface Supervisor, give me a lat-lon!”
A young operations specialist read the dials on the dead-reckoning tracer table, and called out the current latitude and longitude. The CIC Officer keyed in the geographic coordinates, and then rolled the cursor over to the charted position of the tanker.
“Sir, it’s 130, eight miles from our current position.”
The Weapons officer turned around in his chair to look at Mike in his Captain’s chair.
“Right where this contact is headed, Captain,” he said.
“If it is a submarine,” mused Mike aloud. The squawk box erupted again.
“Sonar has no echoes, last bearing was 122, last range was 8500 yards. Attack director is in PK.”
Mike acknowledged this report with a sigh. It figured; they had been lucky to hold on to this contact for as long as they had, given the water conditions. He had not had much faith in it to begin with, and now the contact had disappeared just like all the others. Linc had put the underwater weapons fire control computer in the Position Keeping mode, which assumed that the contact would keep going on the last computed course and speed. The computer kept the sonar’s display cursor pointed at the predicted position of the contact, in case the echoes emerged again. Mike leaned forward.
“OK, guys, I think we’ve locked on to another hydrospook. Weps, ask Linc if he wants to keep playing with this anymore.”
The Weapons Officer picked up a handset and held a brief conversation with the ASW Officer, nodding as he listened. Mike heard the words “wreck” and ranges and bearings being exchanged.
“OK, Linc. I’ll tell him.”
He hung up the phone and turned to the Captain.
“Sir, Linc wants to go silent on the sonar and continue down this last bearing at twelve knots, below cavitation speed. He wants to drive in for about four miles, and then light off again, see what we turn up. He really thinks this was a valid contact.”
Mike thought for a minute. The ASW Officer always thought that the last contact was a good contact, a possible submarine. This was normal; the ASW officer was supposed to be aggressive. But Mike thought he knew what would happen next: they would pursue the matter for another twenty minutes or so, light off the sonar again, and gain contact on the wreck on the bottom. The whole 1AS team was waiting for his decision.
“And what do you recommend, Weps?”
Mike had learned this ploy at the Navy’s surface command school: if you can’t make up your mind on what to do, ask your subordinates for a recommendation. One of them might know or illuminate the right answer, and it gave you time to think some more.
“We’re out here, and this is the strongest contact we’ve had,” said the Weapons Officer. “It doesn’t cost us anything to keep screwing around with it. Linc thinks this guy is headed for the wreck, either to hide or to throw us off the scent. He wants to go ping around the wreck.”
“OK, OK, you guys do what you want to. I’ll sit here and watch.”
The Weapons officer grinned. “Yes, Sir!”
Mike watched as the Weapons and Operations officers used the PC to refine a course that would allow the ship to pass over the wreck, some 500 feet below the surface. The Exec came back into Combat to see what was going on, and Mike brought him up to speed.
“Gonna let the guys screw around with it for a while; there’s nobody else out here, they like to do it, and it builds up their self confidence,” he explained in a low voice, as the officers crowded back around the plotting table, and the Weapons officer sent new course and speed orders out to the bridge.
“They thought about how they’ll distinguish between a wreck on the bottom and a submarine hiding nearby?”
“Presumably with Linc’s PC magic, but they haven’t thought that far ahead, XO. One thing at a time,” smiled the Captain.
Mike knew that it was going to be hard enough to pass over or even near the wreck, given the vagaries of navigation when beyond radar range of land. If there were a submarine here, it would probably drive by the wreck, presuming the sub knew it was there, and then slip down into one of the canyons and disappear over the shelf into the deep ocean abyss while the destroyer went around in circles. He called for coffee, and settled back into his chair to watch his young ASW team work. It was one of the few remaining joys of being in a destroyer as opposed to a larger ship—the junior officers could be allowed to run an ASW search by themselves, or almost so, and he could observe without having to direct every detail. The Exec would go out to the bridge to make sure they didn’t run over a fishing boat in their enthusiasm. And then hopefully they could go back into port for the weekend.
TWENTY-SIX
The Al Akrab, submerged, Jacksonville Operating Areas, Friday, 25 April; 1240
“Eight knots,” ordered the Captain. His forehead was damp with perspiration, and his uniform was getting sticky.
The depth gauge continued to hold steady; the whine of the pumps beneath the deckplates of the control room competed with the creaking and crackling noises coming from the pressure hull. The needle backed off to 129, and then 128.
“Get her level. Now. We need to turn.”
The Musaid continued to coach the planesman as he adjusted bow and stern planes to bring the boat level. As the water was forced out of the negative tank, the boat became more responsive.
“Come port to 040, small rudder angles,” ordered the Captain.
He knew that if he could bring the submarine’s heading around to a course perpendicular to the oncoming destroyer’s search axis, the net effect would be to nullify the doppler on any returning echoes, regardless of his speed. The tradeoff was that he would now present the whole length of the submarine to the probing sound rays, but he counted on depth and the swirling acoustic layers of the Stream to mask the larger target he presented.
“Depth unstable,” called the Musaid urgently, putting his hand on the helmsman’s shoulder to stay the turn order.
Turning without depth control could spell disaster because the planes would induce rolling moments. The Captain looked at the depth gauge needle; as it cycled between 128 and 130. The submarine was porpoising, creating a shallow roller coaster ride as her buoyancy changed. The pumps continued to mill and grind.
“Commence the turn! Now! I need to show him null doppler,” shouted the Captain.
The Musaid removed his hand, his face stiff.
“Helm, Aye. Commencing the turn,” responded the helmsman, his voice cracking. The other men in the control room were frozen in position, afraid to look at one another.
“Sonar, what is the destroyer doing?” demanded the Captain, his voice more under control.
“Sir, he continues to ping in omnidirectional mode; the bearing is beginning to draw right; I don’t think he—”
The sonar operator suddenly opened his headset away from his ears, and then reached forward to the console to make an adjustment on the audio volume. He did not have to tell the Captain or anyone else in the control room why: the drawn out, ringing sound of a powerful directional sound pulse was reverberating in the control room. The men looked nervously at one another, and swallowed. A second long ping. The men had to hold on as the submarine rolled to one side, and then the other, as the rudder took effect. The Captain’s face tightened.
“Prepare to release a decoy. Quickly.”
The Deputy jumped from his station at the plotting table, and opened an air valve to arm the starboard decoy tube. There was a small hiss of air as the firing chamber filled to 3000 psi.
“Decoy tube is armed, Sir.”
“Very well.”
Now, thought the Captain, they would have to wait. It all depended on how determined this enemy was. He did not know how long this destroyer had been out looking around the operating areas. They had returned from the mothership in the early hours of Thursday morning and detected the pinging as they clos
ed in submerged from the Gulf Stream. He had to know if this destroyer was actually conducting a search or just out testing his sonar. When his sonar officer had run back through his tapes and determined that this was a sonar they had encountered before, the Captain became suspicious. This destroyer’s presence was no accident. He had determined to shadow it, staying outside the predicted sonar range but near enough to record the enemy destroyer’s search patterns on the passive plot, to learn his tactics, and to appraise his vigilance.
The Captain’s mind raced. Somehow this destroyer may have detected the Al Akrab. And he was sure enough that he had something other than a school of fish to switch to directional keying. The turn would nullify the doppler, but now the Al Akrab would present her full beam to the enemy sonar. Going deep and the swirling layers above them should take care of that. Should.
“Passing 070.”
“Depth is stable; we can slow,” declared the Musaid, straightening up.
“Slow to five knots; continue the turn to 040.”
“040, Aye. Passing 060.”
The Captain considered the timing of the decoy launch. The decoy was a miniature transponder. It was shaped like a tiny torpedo, three feet long and about four inches in diameter. It had an air driven propeller that would run for about three minutes. In the body of the decoy was a sonar receiver and an amplifier. At its nose was a miniature sonar transmitter. The decoy could detect the incoming sonar pulse from the destroyer’s sonar, match its frequency, introduce some slight doppler shift, and ping back at the destroyer. The destroyer’s sonar would see a solid echo since the decoy’s response, however muted, was always stronger than the faint, real echo from the submarine. The destroyer’s sonar tracking circuits would then lock on to the decoy, while the submarine stole away into the depths.
The key to success was the timing of the decoy launch: if the enemy was in firm contact, the decoy would show up as a second contact and be exposed as a decoy, thereby confirming the presence of a submarine. If the enemy sonar had lost contact, the decoy could trick the enemy operator into thinking he had regained contact. The Captain listened carefully to the directional ping.
“Passing 045; steadying on 040.”
His new course was almost seventy degrees off the original course, enough to strip off most of the doppler effect, but not so far north that he would emerge back out of the protective thermal layers of the Gulf Stream. The long pings were not so loud now. The Captain made his decision.
“Release the decoy!”
There was a relatively loud thump as the decoy was expelled into the depths, pointed behind and below them. They could not know precisely which way the decoy would go, only that it would begin to transpond after thirty seconds. The Captain stared at his watch.
“Speed ten knots,” he ordered when the thirty seconds was up.
He would make a dash to the northeast, while hopefully the destroyer would lock onto the decoy as it careened along to the southwest at random depths.
“Ten knots, aye.”
The boat surged forward perceptibly. The long pinging was still audible, but its frequency had changed. Everyone in the control room listened and waited. Then the pinging suddenly stopped.
TWENTY-SEVEN
USS Goldsborough, Jacksonville Operating Areas, Friday, 25 April; 1245
“Sonar is still passive,” announced the Evaluator.
Mike sat forward in his chair. They had driven along at twelve knots down the last bearing of the contact, theoretically closing the range, for the last four minutes.
“How close are we to the wreck?” he asked.
“Sir, the wreck should be 075, at about 16,000 yards,” answered the surface supervisor.
Mike leaned back in the chair, and stared up at the darkened ceiling. Now they would get contact again, this time on the wreck. It was entirely predictable. But, what the hell.
“Tell Sonar to go active,” he ordered.
“Sonar is going active,” announced the Evaluator.
“Sonar Contact!” announced the squawk box, twenty seconds later. “Contact bearing 090, range 10,450 yards. Echo quality sharp, doppler is up doppler, echoes are intermittent due to layering.”
Mike sat up when he heard the report of up doppler. This was not the wreck; doppler meant motion—this contact was coming at them.
“Classification?”
The Evaluator consulted with Linc in the sonar room below.
“Bearing is clear,” reported the Bridge.
“Linc says sonar thinks it’s a decoy, Sir.”
Mike closed his eyes for a moment. A decoy? Oh, come on, he thought. Then Linc’s voice came on the box.
“Captain, this new contact is too good. It’s coming in and out of the layers with a consistent echo quality, and it’s headed in our general direction. The last contact was going away like a bandit. That doesn’t compute. I need to change pulse back to omni and mess around with him, but I think this is a decoy.”
Mike considered this data. The officers around the plotting table were looking at him. He got out of the chair and reached for the squawk box key.
“OK, Linc, do what you want to with the sonar. I think we’re stretching things a little here, but I’ll go along with it. Check your contact out and advise.”
“Aye, aye, Cap’n.”
Mike thought for a moment. If this was a decoy, which he doubted, it implied two things. First, a decoy meant there had to be a submarine. And second, if this was a decoy, where was the sub? He stepped back over to the plotting table, and the officers made a space for him around the plot.
“What was the original contact doing when we lost him —where was he?” he asked.
The plotter pointed to the red trace with his pencil.
“He was going away from us, to the east by southeast, speed around eight, maybe ten knots. We lost him right here, Cap’n, and the new contact came up over here.”
Mike could see that the new contact had appeared north of the original track. Which implied that the sub—there I go again, he thought, the sub—had turned left before putting out the decoy. Linc was back on the box again, his voice excited.
“Cap’n, Sonar Control: the echoes remain the same no matter what keying mode or frequency we lay on this thing: the Chief says that’s the sign of repeater—this thing is pinging back at us with a constant doppler shift, and matching our freq so that we get consistent echoes. By our bearings plot it’s going south now, across our track, but the contact’s quality is constant. It’s too good to be anything but a transponder.”
“OK, Linc, how do we let this guy know we’re onto his trick?”
“We go silent again, wait a coupla minutes, and then come up again—let the decoy run outa gas. Then we go back into search.”
“Where do we look, Ops?” Mike asked.
Mike knew that this was the magic question. They had lost the original contact probably because he had gone deep enough to get beneath several acoustic layers. After that, the sub could have gone in any direction. Their chances of regaining him were slim to none, but the appearance of a possible decoy changed the whole game.
“Cap’n, I don’t have a clue. He could be anywhere.”
The Weapons Officer spoke up.
“Sir, the decoy came from north of the original track. He probably turned north, dropped the decoy, and then turned again. My guess he’s gone out into the Stream because that’s the best water to hide in. I recommend we go silent, turn northeast or east, wait fifteen minutes or so, and then resume omni pinging. That’ll tell this guy we weren’t fooled.”
Mike thought about that. Tell this guy? What guy? If there was a sub out here, and that now looked to be at least possible, what did they want to reveal to the sub’s skipper? That the U.S. Navy was now alerted to the presence of an unidentified submarine? Wouldn’t it be better to break off, go somewhere else while they reviewed what they had, looked and listened to their tapes, and maybe asked for some more assets?
“Son
ar reports no echoes; last bearing 094, last range 9400 yards.”
No echoes. So now, whatever it was, it was gone. He stared down at the rubber matting on the CIC deckplates. Should he call in help from the specialized ASW forces? Maybe get a helo out here, or one of the ASW destroyers? If you find a fire, first call the fire department, then and only then you grab a bucket of water. He was aware that his officers were waiting for a decision. He felt a sudden need to consult with the Exec.
“Evaluator, turn off track to the south, resume omni pinging, resume the original search pattern. Wait one half-hour, then secure from 1AS. Tell Linc to bring his tapes up here to Combat and bring the Chief. I’m going to go talk to the XO.”
The Evaluator raised his eyebrows and then acknowledged and passed the orders down to sonar over the sound-powered phones. Mike knew that Linc would be protesting that they would lose any chance of regaining contact. The Evaluator gave him a verbal shrug and told him to come up to Combat with his tapes. The CIC crew also looked visibly disappointed, but Mike ignored them. He headed for the bridge.
Stepping out onto the bridge, he had to squint in the bright sunlight. He saw the XO leaning on the Captain’s chair, and smiled inwardly as the Exec stood upright suddenly when the bridge watch announced that the Captain was on the bridge.
“XO, step out here with me for a minute.”
They walked out onto the port bridge wing, and the watch team made themselves inconspicuous on the other side of the bridge so that the two could speak in privacy.
“XO,” said Mike. “Linc thinks that last contact was a decoy. If he’s right, that changes everything.”
“Yes, Sir, I overheard that report on the phone circuit. I’m having a little trouble with it, myself.”
“Yeah,” said Mike, looking out over the calm, entirely peaceful sea. Staring at the vivid red lines on the plotting table made it seem real. The placid seas of the Jacksonville operating areas, dotted with fishing boats and afternoon pleasure craft, framed the whole idea of a submarine in unreality. He shook his head.
Scorpion in the Sea Page 25