1) According to press reports, the Russian submarine had the number 689 on her sail

¹⁾According to press reports, the Russian submarine had the number 689 on her sail. Numbers on the hulls of Russian submarines and warships are typically drawn in order to misinform a potential enemy and have nothing to do with the real designations, which are classified. In the following text we will call the Russian submarine 'Sierra' for the sake of brevity.

²⁾"Novosti" TV report (Moscow, February 24, 1992).

³⁾The US and Russia recognize a 12-nautical mile territorial limit, but the two countries have different methods of applying this limit. According to the Russian method, points are marked 12 nautical miles beyond the line between two pieces of land that extends farthest into the sea on either side of a bay or a gulf: in this case, Tsypnavolok Cape, on the Rybachii Peninsula; and the northern shore of Kildin Island. The U.S. method draws a line 12 nautical miles offshore that follows the general contour of the coastline. The U.S. and former Soviet governments have held bilateral discussions, most recently in 1990, aimed at resolving this and other nautical boundary disputes. These talks have so far not met with success.

⁴⁾Bill Gertz, "Russian Sub's Sail Damaged in Collision," Washington Times, Feb. 27, 1992, p.4.

⁵⁾Bill Gertz, ibid.

⁶⁾Artur Blinov and Nikolay Burbyga, "Underwater Incident in the Kola Gulf," Izvestia, Feb. 20, 1992 p.1; Nikolay Burbyga and Viktor Litovkin "Americans Not Only Helping Us, But Spying on Us. Details of Submarine Collision in Barents Sea," Izvestia, Feb. 21, 1992, p.2.

⁷⁾Bill Gertz, op.cit.

⁸⁾Melissa Healy, "Russian, US Subs Collide off Murmansk," Boston Globe, Feb. 19, 1992.

⁹⁾John H. Gushman Jr. "Two Subs Collide off Russian Port," The New York Times, Feb. 19, 1992.

¹⁰⁾If an unexpected political reversal results in future military conflict between the US and Russia, the US Navy might well prefer to fight, at least some of the time close to Russian Naval bases. Such concerns may well lead US Navy planners to conclude that submarine missions near the Soviet coast should be a high priority military activity.

¹¹⁾Barry R. Posen, Inadvertent Escalation: Conventional War and Nuclear Risks, Cornell University Press, 1991, p. 142.

¹²⁾According to the same source, foreign submarines typically operate in the area north of the entrances to Kola and Motovsky Bays.

¹³⁾Desmond Ball "Nuclear War at Sea," International Security, Winter 1985-86, v.10, No 3, pp.3-31.

¹⁴⁾John H. Gushman, Jr., op.cit.

¹⁵⁾ The Russian Navy presumably keeps substantial ASW forces on alert at Murmansk, since it is known that foreign submarines routinely attempt to operate in the waters near their naval bases.In the ocean waters near Murmansk an American submarine might have to contend with airborne, shipborne and shore-based radars capable of detecting the presence of a periscope deployed above the ocean surface. For example, a deployed submarine periscope can typically be detected at dozens of kilometers by modern airborne radars on maritime patrol planes. In addition, if a submarine is detected in highly confined coastal waters, it may have few tactical options available to evade further detection. As it seeks to escape, there is always the potential that it could be trapped, or later be reacquired, by ships and helicopters that are executing a coordinated search of the confined area with active sonar systems. The American submarine would therefore have to operate with extreme caution, as nearby Russian ASW forces could be quickly launched in pursuit of the submarine if it is detected.

¹⁶⁾ Nikolay Burbyga and Viktor Litovkin, op. cit.

¹⁷⁾ This question is very important for survivability of the CIS strategic forces at sea. If quieter American attack submarines could covertly trail them, this could cause an unstable situation in a conflict between these two countries.

¹⁸⁾ Several different sources all agree that the depth is 100-200 m there.

¹⁹⁾ For detailed quantitative estimations of the detection range see: Future of Russia's Strategic Nuclear Forces: Discussions and Arguments, (by Eugene Miasnikov, Center for Arms Control, Energy and Environmental Studies at MIPT, Dolgoprudny, 1995) and Can Russian Submarines Survive at Sea? The Fundamental Limits of Passive Acoustics, (by Eugene Miasnikov, Science and Global Security, 1994, v. 4, pp. 213-251).

²⁰⁾ Wind generated noise is created by the action of breaking waves at the ocean's surface. Since sound waves in the ocean are also strongly reflected by the ocean bottom, sound waves generated in shallow water are confined to very small volumes of water relative to sound waves generated in deep water. This mechanism results in markedly higher wind-generated sound power densities relative to those in deep water.

²¹⁾ In technical terms, the coherence of sound in shallow water is considerably lower than that in deep water. This means that it is not possible to achieve shallow water array gains as high as those in deep water.

²²⁾ This deep ocean phenomenon is known as "convergence zone" formation. In relatively narrow (less than 4-6 km) convergence zones, submarine generated sound level may be 100 times larger than in between them. As a rule, in these convergence zones the correlation length of the signal is also larger.

²³⁾ Sierra class submarines were first commissioned in 1984 (Norman Polmar, The Naval Institute Guide to the Soviet Navy, 5th ed., 1991) when the quieting technology of the Soviets was substantially improved. The Russian submarine probably moved at a low speed of 4-7 knots, since motion with a higher speed would increase the flow noise in the hydrophones and decrease her detection capabilities, which might be dangerous in a shipping area. We assume in our calculations that the source noise level of the "Sierra" is 120 (dB) decibel with respect to 1 microPa at a distance of 1 m. For World War II submarines, the noisiness at low speeds is 140-160 dB ( R. J. Urick, Principles of Underwater Sound, McGraw-Hill Book Company, 1983), which is 100-10000 times higher. We assumed also that the source noise level of the "Los Angeles" class submarine is 110 dB, since the U.S. has more advanced submarine quieting technology.

²⁴⁾ The wind speed exceeds 15 m/s 25 percent of the time in this area. See Tom Stefanick, Strategic Antisubmarine Warfare and Naval Strategy, Lexington Books, 1987, p.332.

²⁵⁾ In an active mode, a fixed sonar of a submarine operates at a frequency of 3-10 kHz which allows it to get much more precise information on the bearing of a target. The lower the frequency, the less accurate the target bearing estimation. However, the source noise level of a target submarine at such high frequencies is small and therefore difficult to detect passively. For this reason, when passive acoustic data obtained with a fixed sonar, a narrowband processing technique is typically applied at lower frequencies.

²⁶⁾ It is also interesting to note, that even if the Sierra approached Baton Rouge from behind and for some reason the American submarine did not hear Sierra's active sonar, the target strength of the American sub would be 10-100 times less than if it were seen from the side. The Sierra would not have detected the target in this case even at relatively close distance.

²⁷⁾ Valery Alexin, "The Hunt for "Red February"? Once More about the Collision of Two Nuclear Powered Vessels," Krasnaya Zvezda, February 27, 1992.

²⁸⁾ It should be noted that an active system could be much more expensive to deploy and maintain than a passive one. Given the area to be surveyed and the detection range of the individual array of receivers it can be easily found that a large number of receivers would be necessary to detect submarines within 12 mile zone at Murmansk area either by passive or active means.

²⁹⁾ The Navy of the CIS said also that a foreign submarine was chased out of Russia northern waters on March 26, 1992 just six weeks after the collision approximately at the same location. According to Krasnaya Zvezda, a 100 km long antisubmarine barrier of sonoboys was deployed from the air (A. Pilipchuk "Antisubmariners Were Ready to Use Weapons," Krasnaya Zvezda, March 28, 1992, p.2). Given the detection range of sonoboys, this operation must have been very expensive.

³⁰⁾ These means of detection could only be used to locate more precisely an already detected submarine because of they have a very small detection range (200-500 m) and, therefore, the aircraft that carry them have a low search rate.

³¹⁾ The vulnerability of Russian ballistic missile submarines to detection by passive acoustic means (at present, by far the most important means for detection) in different types of ocean areas will be discussed in our separate paper which is in preparation now.