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
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