It's the height of the Cold War, and three hundred meters beneath the surface of the
stormy North Atlantic a Soviet submarine steams past the Icelandic coast.
The Soviet Captain looks to his crew- everyone is holding their breath waiting to find out
if they've slipped past the formidable NATO anti-submarine picket line that stretches
from Iceland to mainland Europe.
After several tense minutes of silence, the crew relaxes- sonar can hear NATO patrol ships
far away, but not a single one of them has changed course: they haven't been detected.
Ordering his men to hold bearing, the Captain plots a course a few hundred miles from the
American coastline where his nuclear ballistic missile submarine will loiter undetected,
ready to deliver a devastating surprise nuclear attack in the case of war.
This is how the balance of power between the two great superpowers is kept, neither side
able to completely eliminate the other's nuclear arsenal completely without being destroyed
in kind.
Settling in for a long, three month patrol, the Soviet crew breathes a sigh of relief,
knowing they've successfully fooled NATO's anti-submarine patrols.
Yet unknown to the Soviet sub, a predator stalks the deep cold of the Atlantic just
a few hundred meters behind them- a 370 foot (115 meter) beast made of high tech steel
and aluminum, manned by the US Navy's finest sailors.
The Russians are good submariners, but their subs lack sophistication, and unbeknownst
to them a powerful American underwater weapon can detect them from clear across the Atlantic,
zeroing in the US Navy's hunter-killer subs onto their location.
For decades Soviet nuclear attack submarines believe that they are prowling the oceans
of the world undetected, completely unaware of the hidden killers always following their
every move.
If nuclear war ever broke out, the Soviet ballistic missile submarine fleet would never
get a chance to join the war, eliminated in minutes by the hidden assassins keyed on to
their locations by an incredible piece of American technology: the Sound Surveillance
System, or SOSUS.
Very rudimentary passive and active sonar systems existed as far back as World War I,
but these early systems could only manage detection at distances of a few thousand yards
and even then, only under the most favorable conditions.
During World War II sonar technology barely moved past these rudimentary systems, and
much anti-submarine surveillance was based on visually identifying the vessels by air
as they loitered near the surface to recharge their batteries or bring up their periscopes
to target ships.
During the 1920s though the development of the sonic depth finder was an important first
step in developing more advanced and capable sonar systems, although the various elements
of a modern sonar system would not achieve technological maturity, or be truly understood,
until halfway through the Second World War.
In 1937 Leigh University scientist Maurice Ewing made a critical discovery which would
catapult American sonar technology far ahead of its competitors- while doing seismic refraction
experiments in water three miles dept in the North Atlantic, Ewing used explosive charges
placed at different depths to generate sound waves.
As Ewing listened to the echoes of the explosions he discovered that sound signals at very low
frequencies could travel great distances with minimal loss, and he postulated that in certain
conditions so-called “deep sound channels” could exist which would propagate an acoustic
signal for hundreds or even thousands of miles.
At the same time the invention and refinement of the bathythermograph by scientists at the
Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution made
possible for the first time the continuous measurement of ocean temperature at various
depths, and more importantly how fast the speed of sound varies at different distances
below the waves.
A growing understanding of how underwater sounds are refracted- or bent- by variations
in the sound's velocity caused by different temperatures and depths helped support Ewing's
hypothesis that underwater channels could indeed propagate acoustic signals for as much
as thousands of miles.
Wasting no time, the Navy immediately authorized a slew of tests for developing these deep
sound channels for military use, although at first they would only be used for communications.
During the spring of 1944 Erwing supervised a test using the USS Buckley, which steamed
away from a receiving ship, dropping explosive charges set to blow at various depths.
By determining the pattern of explosions and the depths they occurred at, the Navy hoped
to build a system of communication that was impossible to jam, and only required a receiving
ship to have nothing more than a basic hydrophone.
The explosions from the Buckley were clearly discernible until at last the Buckley had
to call off the test after reaching a distance of 900 miles and still being clearly heard
by the receiving ship.
The test was a huge success, and a system for helping locate and rescue downed pilots
was immediately developed.
Named SOFAR, for Sound Fixing and Ranging, the rescue system consisted of nothing more
than a downed pilot dropping small explosive charges down to the depths of the deep sound
channel, where an underwater system of hydrophones would pick up the explosions and triangulate
the pilot's exact location.
Too late in the war to be of great effect, the rescue signaling system was nevertheless
a huge success- but some minds in the US military slowly began to see an altogether different
potential to this quirk of underwater acoustics.
After World War II's end the US Navy continued to establish major SOFAR networks in both
the Atlantic and Pacific oceans, investing in the future security of its downed pilots
in case of another major war.
Yet as the first chills of the Cold War began to grip the world, the growing threat of a
Soviet submarine fleet based on captured German designs urged Navy leadership to develop more
formidable anti-submarine warfare capabilities based on the detection of underwater sound.
By the early 1950s the US government believed that Soviet submarines posed the greatest
threat to American security over any other Soviet weapon, and thus established Project
Hartwell.
For six months the best and brightest minds of the American Navy and civilian scientists
alike drew together to discuss how to counter the Soviet submarine threat.
Long-range submarine detection was premier in the list of topics discussed during Project
Hartwell, and a focus of its efforts.
Then physicist Frederic Hunt electrified the project heads with a stunning, and very convincing
idea: why not use SOFAR to detect Soviet subs?
He showed Project Hartwell's leadership that higher frequency sounds made by Soviet subs
could be easily detected at ranges of a few hundred miles, but frequencies below 500 Hz
would easily penetrate through the various layers of the oceans to reach the deep sound
channel from virtually any depth, and thus make detection of noisy Soviet subs possible
at ranges of thousands of miles!
The US Navy immediately started several highly secret research programs to better understand
long-range sound transmission through the ocean, and even partnered with AT&T to begin
building underwater listening stations.
This budding secret surveillance network was classified with the acronym SOSUS, standing
for Sound Surveillance System, and received a Top Secret classification.
In January 1952 the first prototype SOSUS installation was deployed by a British cable
layer, and after a series of successful detection trials with a US submarine, the Navy approved
the installation of more arrays along the entire American East Coast.
Two years later the system would extend to the West Coast and to Hawaii as well, ensuring
that no hostile sub could approach the US mainland without being detected.
The early SOSUS arrays were fixed directly to the sea floor at specific locations that
could access the deep sound channel, and oriented at right angles to the expected approach axis
of a hostile submarine.
The outputs of each hydrophone was transmitted to shore processing stations through multi-conductor
armored cables.
At these shore-based processing stations the incoming data was analyzed, and observers
would look for the distinct frequencies given off by rotating machinery.
Hundreds of printers at these facilities would output infographs 24 hours a day, constantly
monitoring the entire ocean for Soviet signals.
Observers would look for distinctive submarine signatures printed on the graphs, and then
if simultaneous contacts were made with multiple arrays then a target could be verified and
its position triangulated.
Moments later, a US sub or surface boat would be dispatched.
SOSUS had originally been designed to detect air-breathing soviet diesel submarines, which
would have to surface to snorkel depths to run their diesel engines and recharge their
batteries.
However the system's ability to cover a wide range of frequencies at nearly any depth would
prove even more effective at tracking deep-diving Soviet nuclear powered submarines, with the
first SOSUS contact on a Soviet nuclear boat west of Norway established in 1962.
SOSUS would go on to play a major role during the Cuban missile crisis, when it detected
three Soviet submarines leaving Russian waters and heading for Cuba.
In 1968 SOSUS made its first detections of Soviet Charlie and Victor class submarines,
proving its worth even against upgraded Soviet designs- it even allowed for the discovery
and secret retrieval years later of a Soviet Golf class submarine that had sunk north of
Hawaii.
The US Navy had a silver bullet in its arsenal, and with it the ability to completely shut
down the threat of Soviet submarines.
Yet the secret of SOSUS wouldn't last, and late in 1967 US Navy Chief Warrant Officer
John Anthony Walker strolled into the Soviet Embassy in Washington and sold a top secret
radio cipher card for a few thousand dollars.
His treachery directly led to the North Korean attack on the USS Pueblo while in international
waters- an act which was later revealed to have been coordinated by the Soviets who wanted
access to the encryption devices stored aboard so that they could make full use of John Walker's
leaked intelligence.
Aboard the Pueblo though the Soviets discovered some details about SOSUS, and through subsequent
spying soon discovered the fact that their submarines had been tracked almost effortlessly
for two decades.
Immediately after the John Walker betrayal, Soviet submarine designs became much quieter
and thus harder to detect.
SOSUS continued to operate however until the end of the Cold War, and in 1993 with the
threat of Soviet submarines nothing more than a memory, the system was turned over to civilian
researchers who adopted it for studying whale migrations and communication.
In 1996, SOSUS' big brother, the advanced deployable System, became operational, as
the need to monitor the world's oceans for new threats once more became vitally important.
If you found this video interesting, may I suggest you check out our other video, And
as always if you enjoyed this video Why Living On A Submarine Sucks!
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