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The Soviet Union/Russian Navy Project 705 (Lira) was a submarine class of hunter/killer nuclear powered vessels (Podvodnaya Lodka Atomnaya). The class is also known by the NATO reporting name of Alfa. They were the fastest and one of the deepest diving military submarines built, with only the K-278 Komsomolets competing in crush depth.

Preproduction

The initial design work began in 1957 and was highly innovative. A special titanium alloy hull would be used to create a small, low drag, 1,500 ton, three compartment vessel capable of very high speeds (in excess of 40 knots) and deep diving. The submarine would operate as an interceptor, staying in harbour or on patrol route and then racing out to reach an approaching fleet. A high-power liquid-metal-cooled nuclear plant and extensive automation would also greatly reduce the needed crew numbers to just 16. The practical problems with the design quickly became apparent and in 1963 the design team was replaced and a less radical design was proposed, increasing all main dimensions and the vessel weight by 800 tons and doubling the crew.

A prototype, Project 661 or K-162 (since 1978 K-222) (referred to by NATO as the Papa class), was built at the Sudomekh yards in Leningrad and completed in 1972. The long build-time was caused by numerous design flaws and difficulties in manufacture. Extensively tested and reconfigured it was scrapped in 1974 following a reactor accident. It reportedly had a top speed of 44.7 knots and a claimed dive depth of 800 m. This combined with other reports created some alarm in the U.S. Navy and prompted the rapid development of the ADCAP torpedo program and the Sea Lance and W-class submarine projects (the latter two were cancelled when more definitive information about the Soviet project was known). The creation of the high-speed Spearfish torpedo by the Royal Navy was also a response to the threat posed by the reported capabilities of the Alfa.

Production

Production started in 1974 as Project 705 with construction at both the Admiralty yard, Leningrad and at Sevmashpredpriyatiye (Northern Machinery Factory), Severodvinsk. The first vessel was commissioned in 1977. In 1983, with the completion of the seventh vessel, production ended. All vessels were assigned to the Northern Fleet.

In 1961 the design bureau was given a special permission to violate rules and standards of military shipbuilding when it could improve the vessel capabilities. The goal was to produce a submarine with:

  • Sufficient speed to successfully pursue any ship;
  • Ability to avoid anti-submarine weapons and to ensure success in underwater combat;
  • Low detectability, especially to active sonars;
  • Minimal displacement and minimal crew complement, similar to strategic bombers, to ensure everything above.
The use of a very small crew was viewed as one of the distinctive features of new-generation submarines, adopting the aircraft's concept of a fully automated vessel with minimal, but highly trained crew. The concept of an underwater fighter went to tactics as well. Lira was viewed as an underwater implementation of interceptor, capable of destroying detected enemy ship groups. The emphasis was put on ensuring success in underwater combat, due to expectations of a symmetric response.

Project 705 boats were intended to be an experimental platform themselves, to test all innovations and rectify their faults, that would afterwards found a new generation of submarines. They consisted almost entirely of the newest, custom-developed - and therefore untested - solutions. This highly experimental nature mostly predetermined their future and with the end of the Cold War the experiment never progressed to a new class of submarines.

Propulsion

The power plant for the boat was to be the new concept, a Lead cooled fast reactor. Such reactors have a number of advantages over older types:
  • Liquid metal cooled reactor can almost instantly adjust its power output, while typical water-cooled reactors require 20 to 30 minutes to reach full output.
  • Due to higher coolant temperature, their energy efficiency is up to 1.5 times higher.
  • Lifetime without refuelling can be increased more easily, in part due to higher efficiency.
  • Liquid metal can't cause an explosion and quickly solidifies in case of a leakage, greatly improving safety.
  • LCFRs are much lighter and smaller than water-cooled reactors, which was the primary factor when considering power plant choice for Lira.
Even though 1960s technology was barely sufficient to produce reliable LCFRs, which are even today considered challenging, their advantages were considered compelling. Two power plants were developed independently, BM-40A by Hydropress in Leningrad and OK-550 by the OKBM design bureau in Nizhny Novgorod, both using an eutectic lead-bismuth solution for the primary cooling stage, and both producing 155 megawatts of power.

Burst speed in tests was between 43 and 45 knots for all vessels, and speeds of 41-42 knots could be sustained. Acceleration to the top speed took one minute and reversing 180 degrees at full speed 40 seconds. This degree of maneuverability exceeds all other submarines and most torpedoes that were in service at the time. Indeed, during training the boats proved to successfully evade torpedoes launched by other submarines, which required introduction of faster torpedoes such as the American ADCAP or British Spearfish. However, the price for this was a very high noise level at burst speed, as for any body moving through water at high speed. The tactical speed, where the noise would be similar to other submarines, is about 20-25 knots.

Propulsion was provided by the main screw with 30 MW steam turbines, and two 100 kW electric-powered screws served as an additional propulsion for maneuvering and a backup. Backup power systems included a 500 kW diesel generator and a set of zinc-silver batteries.

The OK-550 plant was used on Project 705, but later, on 705K, the BM-40A plant was installed due to the low reliability of the OK-550. While more reliable, BM-40A still turned out to be much more demanding in maintenance than older pressurized water reactors. The issue is that lead/bismuth eutectic solution solidifies at 125 degrees C. If it ever hardens it would be impossible to restart the reactor since the fuel assemblies would be frozen in the solidified coolant, so whenever the reactor is shut down it must be heated externally with superheated steam. Near the piers where the submarines were moored, a special facility was constructed to deliver superheated steam to the vessels' reactors when the reactors were shut down. A smaller ship was also stationed at the pier to deliver steam from its steam plant to the Alfa submarines.

Coastal facilities were treated with much less attention than the submarines and often turned out unable to heat the submarines reactors. Consequently the plants had to be kept running even while the subs were in harbour. The facilities completely broke down early in the 1980s and since then the reactors of all operational Alfa submarines were kept constantly running. While the BM-40A reactors are able to work for many years without stopping, they were not specifically designed for such treatment and any serious reactor maintenance became impossible. This led to a number of failures, including coolant leaks and one reactor broken down and frozen while at sea. However, constantly running the reactors proved better than relying on the coastal facilities. Four vessels were decommissioned due to freezing of the coolant.

Both the OK-550 and the BM-40A designs were single-use reactors and could not be refuelled as the coolant would inevitably freeze in the process. This was compensated for by a much longer lifetime on their only load (up to 15 years), after which the reactors would be completely replaced. While such a solution could potentially decrease service times and increase reliability, it is still more expensive, and the idea of single-use reactors was unpopular in 1970s. Furthermore, Project 705 does not have a modular design that would allow quick replacement of reactors, so such maintenance would take at least as long as refuelling a normal submarine.

Hull

Like all Soviet nuclear submarines, Project 705 used a double hull, where the internal hull withstands the pressure and the outer one protects it and provides an optimal hydrodynamic shape. However, unlike almost all other submarines, the hulls of the Lira had variable diameters. The shape is optimized for minimal active sonar signature and minimal water resistance and, although it complicated the design, it was essential for providing required maneuverability.

Apart from the prototypes, Project 705 and 705K submarines were built with titanium hulls, which was revolutionary in terms of submarine design at the time due to the cost of titanium and the technologies and equipment needed to work with it. The difficulties in the engineering became apparent in the first submarine that was quickly decommissioned after cracks developed in the hull. Later metallurgy and welding technology were improved and no hull problems were experienced on subsequent vessels.

The internal pressure hull was separated into 6 watertight compartments, of which only the third (center) compartment was manned and others were accessible only for maintenance. The third compartment had reinforced spherical bulkheads that could withstand the pressure at the test depth and offered additional protection to the crew in case of attack. To further enhance survivability, the ship was equipped with a protected rescue capsule for the crew that could be ejected.

The hull was designed for extreme depths, below the deep sound layer (at 1 km), but complete redesign of the pipelines and other inter-hull systems was delayed. According to some information , one of the submarines was tested on depths up to 1300 meters but submerging to such depths and returning caused permanent damage to equipment, which in a few cycles would make the vessel very unreliable; possibly this test was conducted just before decomissioning.

Control System

A suite of new systems was developed for these submarines, including:

  • Accord combat information and control system, which received and processed hydroacoustic, television, radar and navigation data from other systems, determining other ships, submarines and torpedoes location and speed and predicted trajectory. Information was displayed on control terminals, along with recommendations for operating a single submarine, both for attack and torpedo evasion, or commanding a group of submarines.
  • Sargan weapon control system controlling attack, torpedo homing and use of countermeasures, both by human command and automatically if required
  • Ocean automated hydroacoustic system that provided target data to other systems and eliminated the need for crew members working with detection equipment
  • Sogh navigation system and Boxite course control system, which integrated course, depth, trim and speed control, for manual, automated and programmed maneuvering
  • Rhythm system controlling operation of all machinery aboard, eliminating the need for any personnel servicing reactor and other machinery, which was the main factor in reducing crew complement
  • Alfa radiation control system
  • TV-1 television system for outside observation
All the systems of the submarine were fully automated and all operations requiring human decision were performed from the control room. While such automation is common on aircraft, other military ships and submarines have multiple, separate teams performing these tasks. Crew interference was required only for course changes or combat and no maintenance was performed at sea. Due to these systems, the combat shift of Lira submarines consisted only of 8 officers stationed in the control room. While nuclear submarines typically have 120 to 160 crew members, the initially proposed crew number was 14 - all officers except the cook. Later it was considered more practical to have additional crew aboard that could be trained to operate the new generation of submarines and the number was increased to 27 officers and 4 under-officers. Also, given that most of the electronics were newly developed and failures were expected, additional crew was stationed to monitor their performance. Some reliability problems have been connected with electronics, and it is possible that some accidents could have been foreseen with more mature and better developed monitoring systems. Overall performance was considered good for an experimental system.

The main reason behind the small crew complement and high automation was not just to allow a reduction in the size of the submarine, but rather to provide an advantage in reaction speed by replacing long chains of command with instant electronics, speeding up any action.

Application

The Alfa class submarines were designed for anti-surface warfare and their primary mode of operation was slowly waiting for enemy ships or information on enemy location and, once detected, rushing at full speed towards the target. While Lira's size, speed and electronics provided enough advantages in combat to defeat a group of enemy ships or a few submarines, their detection equipment suffered because of their small size and they mostly had to rely on directions from coastal facilities to find their targets. This made Lira submarines a strong defensive weapon, but not a capable hunter-killer, as they could be detected more easily than they can detect.

Despite the vessels' constant reliability problems, no crew members were lost on these submarines. This was due to extensive crew protection measures and automation that isolated the crew from most of the machinery.

Influence

Alfas, as with almost all other nuclear submarines, were never actually used in combat and didn't perform any important tasks except power demonstration. However, the Soviet government still made good use of them, by exaggerating the planned number of vessels, which were assumed to allow naval superiority to be gained by shadowing major ship groups and destroying them in case of war. The US replied by starting the Seawolf program to create similar submarines and ADCAP program to create torpedoes maneuverable enough to prosecute successfully Alfa class submarines.

SSN-21 Seawolf, created 12 years later, did not replicate Lira but rather was built around the concept of anti-submarine warfare to respond to the dual threats of the Soviet ballistic missile submarine fleet and the Alfas. It has a burst speed of 35 knots, three times higher displacement, much less maneuverability and does not have the Alfa's characteristic automation. The Seawolf class was not designed as a 'dogfighter' in the manner of the Alfa, but, with its lower noise level and very extensive surveillance equipment, to detect and prosecute at much longer distances. The Seawolf could detect attacking submarines at a long range, particularly the high noise levels produced by Alfas at full speed, both allowing the fleet to avoid an attack and for fleet anti-submarine forces to be concentrated against the attacking submarines. However, Seawolf class submarines cost over 2 billion dollars each and were a very costly response to an initiative that proceeded no further than experiments. With the end of the Cold War and the ending of the threat of the Soviet ballistic missile fleet and Alfa submarines their construction was halted.

The Lira submarines were intended to be only the first experiments for a new generation of submarines and before their decommissioning there was already a family of derivative designs, including Project 705D, armed with long-range 650 mm torpedoes, and the Project 705A ballisitic missile variant that would be able to defend itself successfully against attack submarines, therefore not needing patrolled bastions. Due to the end of the Cold war none of them was actually implemented.

The suite of submarine control systems was later used in Schuka (NATO designation Akula) attack submarines that have a crew of 50, which is more than Lira but still less than half as many as other attack submarines.

Decommissioning

The first vessel was decommissioned in 1987 and four more before the end of 1992. The final vessel underwent a refit and was loaded with a VM-4 pressurised water reactor as Project 671. After being used for training she was decommissioned in 1995.

General characteristics

Alfa class submarines in fiction

Alfa class submarines (especially the fictional V. K. Konovalov) feature in Tom Clancy’s novels, The Hunt For Red October and Red Storm Rising. It also appears in Bruce Sterling’s novel Islands In The Net.

The re-building of Project Alfa class submarines features predominately in Michael DiMercurio's book Emergency Deep.

External links

Russian and Soviet navy submarine classes

Alfa-Klasse | Classe Alfa | アルファ級原子力潜水艦 | Подводные лодки проекта 705, 705К «Лира»

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Alfa class submarine".

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