Nuclear Submarines - 3rd Generation
The nuclear submarines of the third generation (projects 945, 685, 949, 971) were characterized the increased depth of dive and decrease of noise levels. The unique strategic missiles carriers of project 941, the largest submarines in the world, also belong to this generation.
The main feature of the third-generation submarines was a qualitative leap in providing acoustic stealth. The first ships of this generation were American boats of the Los Angeles type (SSN688), the main one entered service in November 1976, and the last of the 62's in 1996. After going through three modifications, it is one of the most advanced in submarine construction. This type is distinguished by powerful hydroacoustic armament, low noise, the presence of 12 outboard UVP for the Kyrgyz Republic, which in fact made the submarine multi-purpose.
With the developed delay, the third-generation Russian multi-purpose submarines of the project. 945 and 971 were commissioned in 1984 (8 years after the "Los Angeles"). Shark-type ships, designed in the Malachite SPMBM under the direction of General Designer G.N. Chernyshev. One of the main priorities in the creation of these ships was an indicator of acoustic secrecy. As a result, underwater noise levels comparable to those of Los Angeles-type submarines were reached, and the use of compact KR from TA also turned these ships into multi-purpose ones.
With the creation of the third generation, the evolutionary improvement of the hull shape and protruding parts continued. The fundamental principles of shaping, developed for the second generation, have not undergone significant changes. In practical terms, the principle of "good hydrodynamics - good acoustics" was fixed and acted.
Distinctive features of the American and Soviet nuclear submarines have become various lengthening of the hull. In the Los Angeles type, the L / B ratio increased to 10.9, while in the Leopard type, on the contrary, it decreased to almost 8 (like in Ex. 705). At the same time, the length of the cylindrical insert of the Los Angeles submarine was greater than that of the Barça (about 50% vs. 30%). The American ship was distinguished by a shorter and more complete aft profiled part of the hull.
The reason for the differences in the elongation of the hulls lies in the design features of the submarines of the two countries and, above all, in the adopted architectural-constructive type. At the single-hull “Los Angeles”, they were located in the extremities, increasing the total length of the hull, while for the two-hull Barca, they were located along the robust hull, increasing the width. A distinctive feature of the submarine type "Bars" was the increased logging fencing. Unlike pr. 671, a pop-up rescue chamber was installed on them, which led to the extension of the barrier and an increase in its width. In US submarines the form of the barrier remained virtually unchanged.
The shape of the stern tail remained unchanged - a pure cruciform with a gondola of a towed antenna on the vertical stabilizer of the Barça. On American boats, the towed antenna is located on the hull for the most part of its length and is closed by a fairing.
A special feature of the Los Angeles submarine missile silo, which entered the fleet since 1988 (San Juan), was the abandonment of rudder steering wheels and the installation of retractable nasal horizontal rudders. This was due to the adaptation of ships to navigation in the Arctic.
When choosing an architecturally-constructive type, each country went its own way. Los Angeles-class ships were the first fully single-hull submarines. Throughout their robust hull, both the light hull and the superstructure are missing. The main ballast tanks were finally divided into bow and stern groups and located in the extremities. Thus, the submarine shipbuilding of the USA completed the evolutionary line of transition to the fully single-rooted architectural and constructive type. It seems that one of the main reasons for this transition was the desire to increase the rigidity of the outer submarine hull and reduce its vibration excitation under the action of the incoming flow.
Domestic submarines of the project 971 retained the two-hull architecture under the terms of ensuring the requirements of the surface unsinkability. Changes in the architectural-constructive type and design of the Los Angeles-class submarine hull resulted in a change in the ship’s overall layout. The sturdy casing is divided by only two inter-compartment bulkheads, which distinguish the reactor compartment. Such placement facilitates the layout of the equipment, minimizes the problems associated with limiting the length of the compartments, simplifies the laying of communication lines. The design of the “Bars” type submarine became the development of technical solutions used in the ships of the second generation and the experience of creating the submarine of project 705. It is equipped with a rescue pop-up chamber.
At the same time, despite the different approach to the choice of the architectural-constructive type, general trends and directions, which are explained by the general physical laws of hydrodynamics and hydroacoustics, began to emerge regarding the choice of the shape of the contours. These trends are as follows - the hull lines are taken in the form of a body of rotation with a single-shaft cone-shaped stern with parabolic outlines and a bow tip in the form of an ellipsoid of rotation with a coefficient of completeness from 0.60 to 0.85. The length of the contours of the nasal tip to the cylindrical insert is from 0.10 to 0.15 the length of the ship (depending on the severity of the contour and the completeness of the nasal tip).
The shape of the nasal tip is due, on the one hand, to the need to ensure a smooth gradient of hydrodynamic pressure, which is also favorable from the point of view of hydrodynamic resistance, as well as the magnitude of turbulent pulsations in the boundary layer, which determine the hydrodynamic interference of the nose hydroacoustic antenna. On the other hand, the completeness of the contours is determined by the technical means located in the nasal tip - first of all by the hydroacoustic antenna and the torpedo-missile complex. This is followed by a cylindrical insert, the length of which may take up to 50% of the length of the body, and may be virtually absent (PL-lab Ave. 1710) or be small - up to 10% - value (A 705). Typically, the length of the cylindrical insert is about 35-40% of the length and is determined by the configuration of a strong body. With a single-hull architectural type, one cannot avoid an extended cylindrical insert. This somewhat increases the hydrodynamic resistance.
From the point of view of hydrodynamics and hydroacoustics, the aft limbs are very important. The length and completeness of the hull in the aft end, the vanishing angle of the hull lines to the propeller determine the flow mode and conditions of the screw, its coefficients of interaction with the submarine hull. To obtain the optimal values of the associated flow and the coefficient of suction, this angle, when fed a single shaft, is also within 10–13 degrees (from one side). The length of the aft tip is determined by this corner of the hull and ranges from 25 to 40% of the length of the ship. For two-shaft submarines, in order to increase the propulsive characteristics, in pr. 661, a split feed was implemented, as if consisting of two coupled single-shaft extremities (“pants”).
The configuration, contours and locations on the hull of the protruding parts - fencing felling, aft feathering, fairing circulation routes - are also determined by the conditions of minimum hydrodynamic resistance, minimal impact on the velocity field in the propeller disk, as well as controllability and maneuverability equipment layout. For example, the fencing of the cabin in order to reduce the effect of its flow on the work of the propeller should be located as far as possible in the nose. On the other hand, in the area of the fencing of the felling sharp drops of hydrodynamic pressure are formed, which causes the growth of hydrodynamic interference in this area. The shape and dimensions of the cabin fencing also influence the propulsive, hydroacoustic and maneuverable qualities of the ship, in many respects they are also determined by the composition of the equipment and its overall characteristics.
A common feature of the third-generation submarines in the United States and the USSR was a noticeable increase in their displacement, which was 50-100% compared with the second-generation ships. The reasons for this were the use of mechanisms with high vibroacoustic qualities, the complication and growth of the REV, the creation of more comfortable conditions for the crew accommodation.
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