Sea of Shadows eBook - Navy Thriller.com

136 JEFF EDWARDS
130 feet, the temperature began dropping rapidly. The transducer had
passed from the surface duct, a zone of nearly constant water temperature
near the surface of the ocean, into the thermocline, a zone of rapidly
decreasing water temperature that extended down to about two thousand
feet. Below that, the temperature would become nearly constant again at
just above the freezing temperature of water.
The drastic temperature differential between the surface duct and the
thermocline formed a barrier to sound energy. Submarine hunters called it
the sonic layer, or sometimes just the layer. A well-trained submarine
captain would know the depth of the layer at any given time—as well as
his boat’s position in relation to it. Properly exploited, the layer could
make submarines—which were difficult to detect under the best of
circumstances—even harder to locate.
The Sensor Operator looked at the readout. “Layer depth looks like
about a hundred and thirty feet, sir.”
“Let’s start below the layer this time,” the copilot said. “Take her
down to about four hundred.”
“Four hundred aye, sir.” The Sensor Operator watched the descent of
the transducer on his screen for another minute and then pressed a
highlighted soft-key. The depth readout froze at four hundred. “Dome is
at four hundred feet. Request permission to go active.”
The copilot nodded. “Go active.”
The Sensor Operator pressed a soft-key on his screen and was rewarded
with a high-pitched ping in his headphones as the sonar transducer fired a
pulse of sound energy into the water four hundred feet below the surface.
He began scanning his screen for the telltale echo that a submarine would
produce. “We are active, sir.”
The copilot keyed his radio circuit and waited a half-second for the
crypto burst, a short string of garbled tones that the UHF transmitter used
to synchronize its encrypted signal with the secure communications
satellite. “Strike Group Command, this is Wolfhound Eight-Seven. My
dome is wet. I am active at this time, over.”
The voice that answered a few seconds later had a strange warble to it.
“Wolfhound Eight-Seven, this is Strike Group Command. Roger. Good
hunting, out.”
The cartoonish voice modulation and the short delay caused by the
crypto burst were unavoidable by-products of the encryption-decryption
algorithm that scrambled the signal at the transmitting end and decoded it
on the receiving end. Ensign Dillon liked to pretend that his voice came
out of the speakers on the other end as a masculine baritone, but deep
down he knew that he probably sounded just as silly over the secure