Part 21 (1/2)

”Good night!” Bud sank down on a lab stool. ”You've come up with a way to make our own subs undetectable. Isn't that enough?”

Tom shook his head. ”Not if we want to keep track of those sneaks. And I think I see a way to do it.”

”How?”

”So far, I have been thinking about refining our own search sonar.” Tom explained that the new system he had in mind would send out a _complex_ pulse--that is, an underwater sound wave with many harmonics instead of a single tone, sharp-peaked sound impulse.

”This will make it less likely that their antidetection gear will absorb all of it,” Tom went on. ”What's not absorbed will return as an echo.

I'm also going to modify our receivers. But I've still not worked that out.”

Bud nodded, his forehead puckered in a look of concentration. ”So--?”

”So our sonar picks up all that hash, and by means of a computer setup filters out the sub's real echo from the shadow reflections.”

”Hey! Sounds pretty cute,” Bud said.

Tom broke into a dry chuckle. ”Right--_if_ I can do it.” After that job, Tom added, he hoped to adapt his own antidetection methods to make hydrolung wearers safe from underwater detection. ”And if the Jupiter prober hasn't been found by that time, Bud, I'm going to request the Navy to let us take over the search alone.”

Bud gave a whistle of excitement at the possibility of new undersea adventures ahead. ”Count me in, pal!”

The two boys broke off their conversation a short time later and went back to the Administration Building for lunch with Tom's father.

Mr. Swift greeted them with a smile as they entered the big double office. ”Glad you could join me, boys! Chow's laid out quite a feast for us today.”

Three places had been set at the conference table, and an appetizing repast of sizzling ham and sweet potatoes waited in covered dishes on a lunch cart nearby.

”Mmm!” Bud inhaled the aroma. ”Good chow from good old Chow!”

Tom switched on the videophone screen to a private channel to catch the noon news while they ate. The newscaster wore a look of excitement as he spoke without pausing for the usual commercial.

”The Brungarian government has just scored a propaganda bombsh.e.l.l!” he reported. ”In a news announcement released less than half an hour ago, they stated that their Navy has perfected an _undetectable submarine_!”

The Swifts and Bud froze, openmouthed, at the newscaster's words.

”No need to tell you what this could mean to American security,” he went on. ”If enemy subs slipped through our continental defenses, their missiles could devastate the United States with scarcely an instant's warning! The whole country's been rocked by the announcement. An official comment by our Defense Department is expected at any moment.”

”Sufferin' satellites!” Bud gulped.

Mr. Swift nodded. ”It's a great propaganda stroke. But I wonder why they've chosen to reveal their secret at this time.”

Tom said thoughtfully, ”Dad, do you suppose they've realized the fact that we _know_ about their antisonar gear?”

”Could be, son. They may figure that since the secret is out already, they may as well play it up for all it's worth.” The elder scientist paused and frowned. ”Or it might be intended to force our hand.”

”You mean in hopes of getting us to reveal whether or not we have an antidetection system ourselves?” As his father nodded, Tom scowled. ”If so, that sub yesterday may have been observing our tests.”

The telephone rang and Tom leaped to answer it. The caller was Dan Perkins of the _Shopton Evening Bulletin_.