CHAPTER XII
DETECTION TEST
"Don't worry, Phyl. It may be only a blown fuse," Tom tried to assurethe fearful girl.
But Tom was worried himself. Not only might he be in danger, but itcould involve his friends!
Nevertheless, he raised his voice above the excited babble. "Please becalm, everyone! We'll have the lights on again in a jiffy!"
Taking Phyl by the hand, Tom groped his way toward the main door.
"Let's check the switch," he murmured, and ran his hand over the wallnear the door. He located the metal plate and flipped the switch.
The lights went on! Good-natured cheers arose. Bud, grinning butpuzzled, left Sandy's side long enough to come over and speak to Tom.
"What happened?"
"I guess some practical joker clicked off the switch."
Bud suddenly caught sight of a stout youth in a plaid shirt and bluejeans, who was standing in a nearby corner. He was shaking all over withhalf-stifled merriment.
"There's the wise guy! Rock Harriman!"
Rock, an all-star tackle on the Shopton High football team, was wellknown for his pranks and practical jokes. Bud rushed over.
"Okay! Confess!" the husky young flier roared in a jokingly ferocioustone.
"Don't get sore!" Rock gasped between chuckles. "I couldn't resist. Boy,did you hear everyone squeal when the lights went out?"
Tom grinned in relief. "How about another dance, Phyl?"
As the music struck up again, he squeezed Phyl's hand. "I sureappreciate your concern, even if I didn't rate it."
Phyl blushed as she returned the squeeze. "You rate with me," sheconfided shyly.
The festivities finally ended after a thoroughly enjoyable evening. BothSandy and Phyl declared to their dates that it more than made up for theforgotten beach party.
"But let's not wait too long for the next date," Sandy warned playfully.
"Okay, that's a deal," Bud promised.
The next morning at the plant Tom called on Harlan Ames. He told of thesinister hoax by the caller who had passed himself off as Lester Morris.The security chief promised to investigate.
"I'll tip off the police about Len Unger," Ames added. "If they can findhim, we may be able to crack this case wide open."
Tom telephoned Bud, Hank Sterling, and Arv Hanson to meet him at thehelijet hangar. The four took off in one of the Swifts' Whirling Ducks,which was standing by loaded and ready. Soon they landed on FearingIsland, where Tom would try out his antidetection invention.
"What'll we use for a test sub, skipper?" Hank asked as they drovetoward the docks.
"A jetmarine," Tom replied.
A truck with engineers and technicians was following the jeep. Itcarried the equipment which Tom and Bud had assembled the previous day.
When they arrived at the docks, Tom gathered the men in a loading shed.He showed them his drawings and explained how his "sonar-blinding" setupwould operate.
"Don't let the diagrams fool you. The basic idea is very simple. Weabsorb all sonar impulses that hit the ship and transmit them out theopposite side of the hull, instead of letting a ping bounce back andshow up on the sonarscope of any hostile sub on the lookout for us."
Most of the job, he went on, would be tedious detail work. It wouldconsist of attaching hundreds of mikes and speakers all over the hull topick up and transmit the sonar pulses. The mikes would be receivingtransducers and the speakers would be transmitting transducers.
"The leads from them," Tom ended, "will be centralized in a singleelectronic control unit inside the ship. I'll handle that part of it."
"Great idea, Tom!" Arv Hanson said admiringly.
"But what a job it'll be rigging those transducers," put in one of thetechnicians.
Tom nodded wryly. "You're right, Danny. If this experiment works out,though, I think I can lick that problem on future installations."
The young inventor explained that he hoped to find a way to mold thetransducers into a continuous plastic sheet. This could be applied tothe hull of a submarine in a single operation.
"But this time we'll have to do it the hard way," Tom added with anapologetic grin.
A jetmarine was hoisted into drydock and the work crew swarmed over it,rigging the transducers. Would his experiment succeed? Tom wondered.Hopefully, he set to work assembling the electronic control unit.
Bud helped the men on the hull for a while, then descended through thehatch to see how Tom was progressing.
_Would his experiment succeed? Tom wondered_]
"I'd go gaga trying to keep track of those circuits," Bud said, as hewatched Tom installing the delicate transistors and other componentswith an electric soldering gun.
The young inventor grinned. "It'll be simple enough when the controlunit's all put together," he replied. "Just a single on-off switch andone test circuit."
By noon, after working at a frenzied pace, the job was done. Tom thankedeach one of the men personally. Then everyone went to eat lunch.
After the meal, Hank Sterling asked, "How about a detection test to seehow she works?"
"Coming right up," Tom said. "Want to skipper the jetmarine, Bud?"
"Sure do!"
"Okay. Pick out a couple of men for a crew and take her down." Tomproduced a hydrographic chart of the waters around Fearing and markedout a test area. "Cruise around there for an hour and we'll try to spotyou in the _Sea Hound_."
"Hide and seek, eh?" Bud grinned and snapped a salute, then left tosupervise the relaunching of the jetmarine.
For his crew, Bud chose Mel Flagler and another man. Mel was anexperienced jetmariner who had gone on the Swift expedition to AurumCity, the underwater ruins of a lost civilization. Here Tom had used hisspectromarine selector to restore the ancient buildings.
Tom, Hank, and Arv went back to the airfield and soon took off in thediving seacopter. Landing on the water, they submerged and began theundersea detection test.
Tom manned the sonarscope personally, eager to conduct as careful asearch as possible.
"Getting any blips, skipper?" Hank called out from his post at the _SeaHound_'s controls.
"Not a ping, Hank. The system seems to be working out even better thanI'd hoped."
Tom felt a glow of satisfaction. He explained, however, that thejetmarine's transparent nose pane--which had to be left unprotected forthe pilot's visibility--offered one vulnerable spot to sonar detection.
"But a little smart maneuvering can cover up that angle," Tom added."Try the hydrophones, Arv, and see if you can hear 'em."
The chief modelmaker slipped on the earphones and listened intently. Foranother ten or fifteen minutes they probed about with no sound trace ofthe "invisible" jetmarine.
But presently Arv snapped his fingers to catch Tom's attention. "Gother, skipper!"
Tom took over the hydrophones. Sure enough, his ears could make out thefaint hum of the jetmarine's atomic turbines. Tom directed Hank towardthe sound, then ordered him to switch on the _Sea Hound_'s powerfulsearch beam.
The light cut a path of radiance through the murky dark-green waters.Dead ahead, the jetmarine could be seen gliding across their field ofview.
"Your system blinded our sonar okay, skipper," Hank commented, "but thisproves she could still be spotted by enemy listening devices."
Tom refused to be discouraged. He ordered Hank to return to base andwait for Bud. Meanwhile, the young inventor applied himself to theproblem of how to mask the sub's noise.
"How about it, pal?" Bud asked, when he reported aboard the seacopter awhile later.
Tom explained the results of the test and the need for an addedsafeguard against hydrophone detection. "Think I see a simple way out,though," he added with a pleased chuckle.
"Natch! With a brain like yours, it's a cinch," Bud quipped. "Explain,professor."
"Well, we can never do away with the noise of a sub's propulsionmachinery," Tom began. "That goes without saying. So we'll have tocamouflage it--lose it in the underwate
r jungle noises, so to speak."
Bud scratched his head. "How do we do that?"
"By amplifying the natural undersea sounds all about it," Tom explained."Fish and all forms of underwater life make a background noise over thehydrophones, you know."
As Bud nodded, Tom went on, "So we simply step up the volume till thesub's own noise gets drowned out or 'wasted' in all the racket."
This could be done, he concluded, with fairly simple amplifyingequipment. Bud, Hank, and Arv were jubilant at the idea.
"Nice going," Bud said. "How soon can we give it a try?"
"Soon as I can rig up the amplifier," Tom promised.
In less than two hours they were ready to submerge again. Zimby Coxjoined the crew. Bud suggested taking along hydrolungs in case of anyneed for tinkering with the transducers or amplifying equipment.
This time, the jetmarine scored perfectly on the test, successfullyeluding all the _Sea Hound_'s efforts to detect it. Tom returned happilyto base, feeling that the antidetection problem was now solved. Thejetmarine, however, failed to appear.
"That's funny. The test was over at four-fifteen," Tom murmured.
"Maybe Bud surfaced out at sea somewhere," Arv Hanson suggested.
Repeated radio calls brought no response. Tom, now seriously worried,took the seacopter down again for another search, hoping that Bud wouldhave switched off the antidetection gear by this time. But neithersonarscope nor listening devices revealed the slightest clue.
Tom, Hank, and Arv exchanged fearful glances. Had the jetmarinefoundered on the ocean bottom--perhaps fouled somehow by Tom's newinvention? Or had Bud and his crew fallen victim to the enemy?
Tom Swift and the Electronic Hydrolung Page 12
