Faulty Intelligence Nearly "Sank" SOSUS During the Cuban Missile Crisis
By Bruce Rule - IUSSCAA Cable 2012
The first Sound Surveillance System (SOSUS) station became operational in September 1954, eight years before there was any intelligence available that accurately described the acoustic characteristics of Soviet diesel submarines as they might have been detected in a hostile (actual operational) environment such as the Western Atlantic. In other words, SOSUS personnel had no idea before the Cuban Missile Crisis what acoustic detections of Soviet submarines would look like on their time versus frequency displays (Lofargrams) or how they could be distinguished from non-threat acoustic targets.
This was the case because, before the Cuban Missile Crisis, almost all acoustic detections of Soviet diesel submarines available to SOSUS analysts for reference purposes (a signature library) involved surfaced operations. Before October 1962, no US intelligence activity had any detections of Soviet diesel submarines operating at long (detection) ranges in a snorkel mode. This was a critical shortcoming because snorkel mode acoustic signatures differed significantly from surface mode signatures.
The FOXTROT Class Soviet diesel submarines that deployed to the western Atlantic during the Cuban Missile Crisis snorkeled on only one outboard diesel-driven shaft line to conserve fuel. Use of a single outboard propeller produced off-axis thrust which had to be compensated for by an off-set rudder angle. Both conditions significantly disturbed the inflow to that propeller producing high levels of low-frequency noise (cavitation). In contrast, operation on the surface on two propellers - the operating condition of almost all Soviet diesel submarine detections made before the Cuban Missile Crisis - produced a more uniform wake inflow to those propellers which reduced the level of cavitation with the result that engine-generated low-frequency acoustic signatures were more detectable than the propeller sources.
When collateral intelligence confirmed Soviet submarines were operating in the SOSUS surveillance area west of Bermuda as the Cuban Missile Crisis developed, the question became: "Why isn't SOSUS detecting them?"
Only after the US naval blockade reduced the amount of commercial shipping (and acoustic detections thereof) in the SOSUS surveillance area did detection of unusual acoustic signatures become evident. More by a process of elimination (there were almost no other candidates) were those detections evaluated as possible Soviet submarines. A P2V ASW surveillance aircraft was sent to investigate one of these unusual SOSUS detections (1). The aircraft sighted a snorkel mast and, upon dropping an acoustic sensor (sonobuoy), detected the same unusual acoustic signature reported by SOSUS.
Even though these acoustic detections bore no similarity to then known Soviet submarine detections, it was obvious they were valid which answered the above question: "Why isn't SOSUS detecting them?"
When recordings of these SOSUS detections were subsequently sent to the activity responsible for the final evaluation (analysis) of SOSUS data, there were serious doubts about their validity, doubts that were allayed only by the aircraft sighting and the acoustic correlation between the aircraft sensor and SOSUS.
It was not until 1963-64 when the Project BRIDGE Norwegian SOSUS site provided more than 20 detections of deploying and/or returning Soviet diesel submarines (2) that the apparent anomaly of the Cuban Missile Crisis detections was explained, i.e., snorkel-mode detections were predominantly - or exclusively at long range - composed of propeller cavitation sources. During the 1963-64 period, SOSUS emerged from what should be described as "The Acoustic Dark Ages." SOSUS became its own source of acoustic (signature) intelligence and no longer had to rely on the other collection systems which had previously provided limited and non-representative detections of Soviet diesel submarines. Basically, SOSUS "boot-strapped" itself out of support intelligence oblivion during the Cuban Missile Crisis. These and subsequent SOSUS detections of Soviet diesel and nuclear submarines also became the basis for the Soviet submarine acoustic signature content and detectability assessments used by all other operational Navy acoustic sensor systems. This remains an often overlooked major contribution by SOSUS to the field of ASW Intelligence over many years following the Cuban Missile Crisis. The conclusion that snorkel-mode Soviet submarine acoustic signature bore no similarities to any Soviet signatures collected before the Cuban Missile Crisis means that any snorkel-mode signatures detected by SOSUS before October 1962 would not have been recognized. (3) Further, Navy schools responsible for training SOSUS analysts, were, at least as late as 1961, still teaching that some Soviet diesel submarines used four-stroke/cycle engines. Such engines were not used by any long-range post-WWII Soviet submarines until JULIETT Class units became operational in 1963. It is probable no Soviet diesel submarines deployed to areas for which SOSUS provided surveillance coverage until the first ZULU and FOXTROT Class units became available for long-range deployments in the mid- to-late 1950s. All of those submarines employed Kolomna 37D two-stroke/cycle engines. So, until 1962, SOSUS, was looking for the wrong acoustic signatures from submarines with the wrong engines.
Historical notes: although a NOVEMBER Class Soviet nuclear submarine deployed into the North Atlantic at least as far south as 60N in July 1962 (4), and employed speeds as high as 24 knots, the failure of the Soviets to deploy any nuclear submarines in connection with the Cuban Missile Crisis suggests they had limited confidence in the operational reliability of those platforms during operations in areas as distant as the Western Atlantic. In reality, the front-line (deployable) Soviet Submarine Force in 1962 was little better than the German Navy would have had in 1945 had they been able to deploy snorkel-equipped Type XXI submarines in significant numbers, i.e., FOXTROT Class submarines were only very marginally improved Type XXIs.
(1) NAVFAC Grand Turk, target ITEM 025, designated CHARLIE-20 by COMASWFORLANT.
(2) Chapter 8, THE NORWEGIAN INTELLIGENCE SERVICE, 1945-1970, by Olav Riste.
(3) A 1965 review of all then still available signature data on SOSUS contacts evaluated as possible Soviet diesel submarines during the years prior to October 1962 identified a single valid detection held earlier in 1962 by the ABLE and SUGAR arrays at CAPE HATTERAS. That target was a FOXTROT Class submarine detected while conducting a 14-knot surface transit on a northeasterly heading while returning to the Soviet Northern Fleet. Initial contact occurred as it became dark in the contact area and continued for several hours until it was lost as a function of increasing range from ABLE.
(4) On 6 July 1962, NAVFAC Barbados reported a Soviet nuclear submarine on bearing 027, a bearing that, at a range of about 3200 nautical miles, splits the GIUK Gap between Iceland and the Faeroes Islands.
So little was known at that time about the acoustic signatures and detectability of Soviet nuclear submarines that recognition of the contact by the involved Barbados watch section was truly impressive.
The signature was detected for several hours. The involved speeds were between 21 and 24 knots.
Upon receipt and review of the Barbados data, the SOSUS Evaluation Center (EC) in Norfolk sent it as a valid detection to the Data Processing Unit (DPU) at the New York Naval Shipyard, the activity established by Joe Kelly for the final analysis of all SOSUS contacts reported as Soviet.
DPU assessed the Barbados contact to have been twin turbines from a US Navy oiler, and there the matter rested until the chance discovery at the Office of Naval Intelligence in 1964 of an HMS OBERON patrol report. That report described detection of a Soviet nuclear submarine operating at 24 knots on 6 July 1962 near 60N, several hours after Barbados lost contact.
That correlation ended the uncertainty; the Barbados contact became the first SOSUS detection of a Soviet nuclear submarine, albeit not officially confirmed until almost two years later. Detection range was about 3000 nautical miles.
- Bruce Rule
(NAVFAC Eleuthera 1959-60, FSS Key West 1960-61, COSL 1961-63, ONI 1963-92 and 1996-2007 with total of two years TAD to Norway 1963-1999)