The Silent Deep

by James Jinks

  SOSUS

  Early Soviet nuclear submarines also had one other major weakness: they were noisy. Unlike diesel electric submarines, which radiated much submerged noise only when snorkelling, the first Russian nuclear submarines generated noise all the time, because machinery, such as reactor coolant pumps and generators, flow noise (the passage of the hull through the water), propeller noise (cavitation) and transient noise (noise generated by activity within a submarine), could all be distinguished from own-submarine self-noise and the ever-present ambient sea noise.6 In the early 1950s, the US Navy developed a system of underwater surveillance listening arrays designed to provide a regular check on the movements of Soviet submarines. Hydrophone arrays were installed on the ocean bed in deep water and signals were carried ashore by submerged cables into processing stations known as Regional Evaluation Centers. The US Navy realized that monitoring the different frequencies generated by Soviet submarines could not only be used for detection purposes, but also, through signal processing, could be broken down by frequency into their component parts, displaced and used for classification purposes. Just as communications transmitted can be fingerprinted, so can a maker of ship noise be recognized by the sort of sound it makes.7 High-grade machinery, for example, radiated low frequencies that could be recognized as characteristic of different classes of ship or submarine. These low frequencies could not be determined by the human ear but were exhibited on paper plots, known as LOFARGrams, which traced out lines drawn out by sensitive sonar sets. Submarines and warships had distinguishing lines that could then be interpreted and used to identify individual vessels.8

  Operationally, the US Navy intended to use a fixed underwater-listening system, the Sound Surveillance System (SOSUS) to provide early warning of hostile submarines entering the North Atlantic or Eastern Pacific, as well as generating ‘cueing’ information which could be used to direct ASW forces towards targets. The US built a number of SOSUS chains in the Western Atlantic and north of the Iceland–Faroes Gap, each terminating at regional SOSUS Evaluation Centers (later called Naval Oceanographic Processing Facilities, NOPFs) that correlated contact information with other intelligence information.9 The West Atlantic array terminated in the US and the Iceland–Faroes Gap array (the Norwegian array) in Iceland. By 1968, ‘improved cable technology and processing methods had enhanced the capability for cross fixing of contacts’ and the US decided to extend SOSUS. It approached the British government about the possibility of participating in a joint Anglo-American project.10 Initially, the US Government proposed a single new Eastern Atlantic array known as SDC2 to cover the greater part of the Eastern Atlantic and terminating in the UK at a specially built SOSUS evaluation facility. The Americans also proposed a third North Atlantic system (SDC3), which would terminate at the same facility. When combined, the two systems would provide coverage of the entire North Atlantic.11

  The British had also experimented with fixed passive sonar arrays. In May 1958, the Director of Naval Intelligence had emphasized ‘the vital importance it is to this country that we should know, in advance of a war, the movements of enemy submarines’.12 The Admiralty Board ‘strongly endorsed’ involvement in the SOSUS project, seeing the hosting of facilities as ‘an economical means of obtaining an entry to a costly USN system’.13 Due to the mid-Atlantic ridge, sonar coverage in the Eastern Atlantic was very poor and as a result:

  Intelligence is unable to track submarines on patrol in the eastern Atlantic, particularly SSBNs in holding areas east of the Azores, and submarines in transit to the Mediterranean and West Indies. This information is of the utmost importance for the long term study of deployment patterns which would provide a warning of any significant change in Soviet posture, and for the day to day tracking of individual submarines for marking [within weapon range with a Fire Control Solution of sufficient accuracy to support weapon discharge] in times of tension and prosecution in the event of hostilities.14

  The British Government recognized that ‘Active British participation in the provision of sites in the UK should ensure that we derive serious benefit from the system’ and that ‘refusal to provide what the Americans may regard as a modest contribution to a joint effort may well result in our being declined valuable information’.15 Access to SOSUS intelligence was seen as ‘invaluable to the RN/RAF ASW capabilities’ as well as the MOD’s Defence Intelligence Staff, which required ‘the best obtainable information on the type and disposition of the Soviet nuclear strike forces … The SLBM force is increasing and the proposed extension to SOSUS, with a terminal in the UK, should add considerably to the total knowledge on the dispositions of the Soviet Navy.’16 The RAF also supported British involvement as its new Nimrod Maritime Patrol Aircraft were equipped with ‘underwater acoustic detection and location capability which could be used if required to enable it to exploit the SOSUS information’.17 These sophisticated new aircraft would put the UK ‘on the same footing as the US and Canadian LRMP [Long-Range Maritime Patrol Aircraft] force’.18

  UK participation in SOSUS was first considered in the spring of 1968 and a Joint US/UK SOSUS Project Team was established later that year to oversee the proposals. Tortuous negotiations continued well into the 1970s over the location of the Regional Evaluation Centre.19 The US eventually settled on an airbase in Pembrokeshire, West Wales, RAF Brawdy. Construction of the new facility began in 1970 under a deep veil of secrecy, with the UK providing considerable assistance in the form of a cable ship and RAF Shackleton Long-Range Maritime Patrol Aircraft to conduct an acoustic propagation survey of the northeastern Atlantic, codenamed Project Neat, to determine the most suitable location for the SOSUS arrays. The US began surveying the UK continental shelf for the location of the undersea cables in May 1971.20 As far as the public was concerned, the new facilities were part of an oceanographic research programme designed to provide the US with detailed information on oceanographic and acoustic conditions off the continental coasts.21 Throughout much of the Cold War the true purpose of the facilities was kept on a strict ‘need to know’ basis and the secrecy surrounding the base sparked off a number of conspiracy theories, ranging from a secret nuclear-weapons storage facility to a UFO tracking station.

  When the first US SOSUS arrays were activated in 1961, the USS George Washington was tracked across the North Atlantic on her first transit from the United States to the United Kingdom. In June 1962, SOSUS achieved contact with its first Soviet diesel submarine, followed a month later by the first detection of a Soviet SSN in waters north of Norway. SOSUS also played a significant role during the Cuban Missile Crisis, detecting the small number of Soviet nuclear-armed ‘Foxtrot’ class diesel electric submarines that escorted Soviet merchant vessels to Cuba. In 1968, SOSUS successfully detected Soviet ‘Charlie’ and ‘Victor’ class submarines. It also played a key role in locating the wreckage of the USS Scorpion, a ‘Skipjack’ class nuclear submarine which sank 400 nautical miles southwest of the Azores on 22 May 1968 with the loss of ninety-nine crewmen, as well as the discovery and retrieval years later of a Soviet ‘Golf’ class submarine that sank in 1968 north of Hawaii.22 When the SOSUS facilities at RAF Brawdy opened in 1974, an emblem was adopted with an appropriate Welsh motto: ‘Dim lloches yn y dyfnder’: ‘No Refuge in the Depths’.

  SOSUS did not provide the exact position of a contact, nor its identity, or its range. Passive sonar was unable to produce the sort of instant picture generated by radar. What it did provide was bearing information, which over time could be used to determine the bearing movement, thus giving a rough idea of where a contact was.23 These areas, known as SOSUS Probability Areas (SPA) could vary in size from between 750 sq. nm to over 3000 sq. nm. At the very least SOSUS would tell the Navy the areas where something was not. As one submariner later wrote, ‘At best it [SOSUS] can only be taken as a good guide and at worst it can be totally misleading.’24

  SOSUS was of unique value in maintaining a plot of the general deployment status of Soviet nuclear submarines. Once SOSUS had
detected a contact, the SPAs would be relayed to Maritime Patrol Aircraft such as RAF Shackletons and later Nimrods, which would then fly out to the area and attempt to narrow in on the contact using sonobuoys. This information was then used to guide submarines and surface ships into intercept positions, where they would attempt to maintain contact with and track Soviet submarines. Once Brawdy was operational, the Royal Navy developed SOSUS-aided intercept procedures which it used to aid its detection and tracking efforts. In order for these to work properly, when good SOSUS information was available it had to be passed to the RAF and the Submarine Service in a timely manner. When this was in the order of 2–3 hours the information was of great value and often resulted in detection. When it exceeded four hours its use was minimal, particularly if the intelligence didn’t contain a track update to confirm where the submarine should have been. While SOSUS provided a good steer, it was also geographically limited to the Iceland–Faroes Gap. It could not, in large areas of the Norwegian Sea, give positions accurately enough for submarines to effectively plan a search. Apart from gaps in coverage, SOSUS suffered from periodic unserviceability caused by trawling damage to seabed cables; in war, the shore stations would be vulnerable to attack and the system would become liable to acoustic interference. For all of these reasons there was a need to supplement SOSUS with other detection systems.25

  Overusing SOSUS also caused problems. While the Soviets knew of the existence and location of the SOSUS chain on the US eastern seaboard, where US and Canadian LRMP aircraft regularly prosecuted contacts, the Soviets did not, in the early 1970s, know about the new Eastern Atlantic SOSUS chains.26 In order to keep the existence of the arrays secret the US prosecuted SOSUS contacts covertly, via passive means. It avoided overtly prosecuting contacts via active means and the same restrictions applied to the RAF.27

  Soviet submariners also eventually developed several methods to escape detection and reduce the effectiveness of SOSUS and Western ASW systems. Soviet submarines would sometimes stay in direct proximity to merchant or naval ships with noise levels that were high enough to obscure the noise signature of the submarine; they would also move at slow, quiet speeds when in areas known to have a SOSUS system. But the Soviets had to strike a balance when transiting to their patrol areas, travelling at speeds that were covert, but quick. We now know that Project 667A ‘Yankee’ class submarines were regularly deployed in the Atlantic from the end of the 1960s onwards and that these missions normally lasted for sixty days, with each submarine spending four and a half weeks in their patrol areas. As the average speed of a ‘Yankee’ class submarine crossing into the Atlantic from Soviet Northern Fleet bases was 12–14 knots, for the 11–13 days it spent transiting to its patrol area, it was vulnerable to detection.

  During Exercise ‘Okean’ in 1970, six ‘Yankees’ were on patrol in the Atlantic, representing all but one of the worked-up hulls available at the time. Outside of exercises, two ‘Yankee’ class submarines could normally be found on station at any one time in the early 1970s, but the UK’s Defence Intelligence Staff expected the number to increase as more of the class entered service.28 Early ‘Yankee’ patrols did not operate in areas that were within missile range of North American targets, and by 1970 only one Yankee had ventured into range of North America, during a brief foray on its homeward transit from a patrol.29 Fortunately for the West, the ‘Yankee’ class stuck to a strict patrol schedule, which was one of the reasons why US/UK anti-submarine systems were so effective at tracking them in the 1970s.

  By 1971, the JIC assessed:

  that the Soviet leaders are probably well satisfied with the measures available to them to protect the Soviet Union from strategic strikes mounted from aircraft carriers. Their reconnaissance aircraft and submarine and surface shadowing ships, supplemented by sophisticated intelligence gathering facilities, make them confident that they will know the location of all aircraft carriers within or approaching strike range of the Soviet Union. Their attack capability, again by aircraft as well as by submarine and surface units, also gives them the capability of mounting rapid strikes with nuclear or conventional weapons against the carrier. Their ship-borne SAM also give [sic] them some capability against any aircraft which manage to take off.30

  But, largely due to the existence of the US Navy and Royal Navy’s Polaris/Poseidon force, the JIC did ‘not believe that the same confidence exists in respect of the Western SSBN threat to the Soviet Union’. The JIC assessment concluded that the Soviet Union had ‘no direct counter to the Polaris or Poseidon submarine force within her grasp’ and predicted that the Soviet Navy would attempt ‘to provide one using every element of anti-submarine warfare available to her’.31

  In the late 1960s, the Soviets started to focus considerable effort on detecting US Navy and Royal Navy SSBNs in strategically important Western chokepoints, such as the Gibraltar and Sicilian Straits, the Iceland–Faroes Gap, and off Western SSBN operating bases such as Faslane and Holy Loch. They also developed a new class of nuclear submarine designed primarily for anti-submarine operations, to hunt down US Navy and Royal Navy SSBNs. Known as the Project 671, or ‘Victor I’ to use its NATO nomenclature, the ‘Victor’ was one of the Soviet Navy’s first second-generation nuclear submarines and its bow sonar – thanks to the Portland spies – appeared to be loosely based on that used in the first-generation Royal Navy SSNs. Although the Soviets made a major effort to reduce the self-generated noise of the ‘Victor’ class, to lower the possibility of detection, the first variant, the ‘Victor I’, of which a class of fifteen were built until 1974, were still relatively noisy compared to their US Navy and Royal Navy counterparts.32

  By the 1970s, the Royal Navy and US Navy’s anti-submarine warfare advantage over the Soviets afforded by intelligence measures such as satellite reconnaissance, ELINT and SOSUS also forced the Soviet Union to divert resources towards protecting their own missile-firing submarines and away from hunting Western SSBNs. The ‘Victor Is’ were used to escort the ‘Yankee’ class SSBNs while on patrol in order to protect them from attack by US and Royal Navy submarines. Although this was clearly intended to complicate Western ASW efforts, in reality the practice unintentionally contributed to the success of US/UK ASW techniques as the ‘Victor I’ was so noisy that it often revealed the location of the ‘Yankee’ it was escorting.33

  Despite the increased ability to detect Soviet ballistic-missile submarines afforded by SOSUS, there was little complacency. The ‘Yankee’ class was still seen as a serious threat that needed countering. A 1971 JIC assessment concluded that the ‘Soviet submarine-launched ballistic missile force [was] already a highly credible component of their strategic nuclear armoury’ and that:

  ‘Y’ class submarines are now regularly deployed in the Atlantic and, to a lesser extent, on the Pacific seaboard to the North American continent. The building of this class appears to be top priority in a generally highly active submarine construction programme. The Russians could numerically match the number of Western SSBNs with ‘Y’ class submarines by 1975, and are likely to do so, although there is nothing to suggest that they will stop there. Soviet ballistic missile submarines are at a disadvantage compared to their Western counterparts in that they mount shorter-range missiles and lack foreign operating bases. Thus their time in transit is longer and time on station relatively shorter. This may well make it more difficult for them to pose a threat to the United States than vice versa and may well affect the eventual size of their force (assuming no ceiling has to be placed on it as a result of the current United States/Soviet strategic arms limitations talks). The introduction into service of a 3,000 nautical-mile range missile, which we believe to be under development, but for which no submarine launch vehicle has yet been identified would increase the flexibility and credibility of the Soviet seaborne nuclear strategic force.34

  What the JIC did not know was that in 1965 the Soviets had started work on a new class of ballistic-missile submarine, the Project 667B ‘Delta I’, which was de
signed to carry the single-warhead R-29 (SS-N-8) missile, with a range of up to 7800 kilometres. From 1972 onwards, the increased missile range of the new ‘Delta’ class SSBNs significantly increased the survivability of the Soviet SSBN force. The first ‘Delta I’ submarine entered service in 1972 and by 1977 eighteen were in service. In addition four 667BD ‘Delta II’ class submarines, each carrying sixteen R-29D (SS-N-8 Mod 2) missiles also entered service in 1975. With the increased range afforded by these new long-range missiles, the ‘Deltas’ would in theory be able to patrol in seas closer to the Soviet Union and, unlike their ‘Yankee’ predecessors, they would not have to cross the Greenland–Iceland–UK Gap in order to fire their missiles at targets in the US.35 As a result, the new Delta SSBNs would be far less vulnerable to Western ASW operations.

  Far more worrying was the possibility that the Soviets would develop a missile with such increased range that it could station its strategic-missile submarines in waters close to the Soviet Union and, more specifically, in the Arctic Ocean, over half of whose shores were Soviet. The world’s fourth largest ocean, nearly landlocked with land-free central waters, depths of roughly 1500–2000 fathoms, permanent ice cap with seasonal growth and diminution, as well as a complex pattern of water flows determined by the combined effects of the great currents of the Pacific and Atlantic Oceans, and by the rotation of the earth, the Arctic was to become an area that neither side could permit the other to dominate.36 Soviet submarines deploying in the Arctic from their bases in Murmansk had no chokepoints to transit and were operating in areas with which they were considerably more familiar than was the West. Conversely, Western submarines seeking to track Soviet SSBNs had themselves to transit the chokepoints of the Davis and Denmark Straits and to operate in areas that were great distances from the US and UK bases, out of the range of other Western air and surface assets. If the Soviets deployed their submarines in the Arctic, they could potentially erode the ASW advantage enjoyed by the West.37