NI: the submarine, developed in the USSR back in the 1970s, was ahead of its time
In 1971, on the crest of the Cold War, Soviet designers presented a unique project - the project 705 Lira submarines. They featured an innovative hull and reactor, as well as exceptional speed.
— The Soviet submarines of project 705 "Lira" (according to the NATO classification: Alfa or "Alpha"), introduced in 1971, made history thanks to the innovative use of titanium hulls and reactors on a lead-bismuth liquid metal coolant.
— These innovations have allowed the Lira-class submarines to reach exceptional speeds of over 40 knots, operate normally at a depth of 350 meters and dive to a maximum depth of 1,300 meters.
— Designed during the Cold War to compete with American counterparts, the Lira-class submarines boasted a double-ended hull, minimal crew requirements and impressive capabilities.
— The initial problems with the appearance of cracks in the body were eventually solved. However, despite the advanced design, only seven submarines were built, the last of which was decommissioned in 1996.
Soviet Lira—class submarines are the fastest in the entire Cold War
A modern submarine is a very complex mechanism that must meet strict technical specifications. The requirements are very specific, since the very nature of the tasks set contradicts the laws of nature.
The fact is that submarines must ensure the vital activity of the crew at depth for long periods of time. On the high seas, a submarine often has to perform secret and rather complex operations. Therefore, it should always be able to "work out" various weapons systems (including nuclear ones) against land or sea targets.
Hence the high requirements for mechanical characteristics. In this regard, it seems quite natural that submarine manufacturers have been actively innovating throughout the last century, striving for technological progress and trying to improve their products and hone their combat capabilities.
An incentive to innovate
In the 1970s, the Soviet Union was in a state of cold war with the United States, which was truly global in nature. Both countries sought to create and implement weapons more modern than those of the enemy. The most obvious and most important area of the technological race between the two superpowers during the Cold War was, of course, space. The so-called "space race" has become a powerful incentive for the intensive development of technology, and its apogee was the American Apollo program, as a result of which astronauts landed on the Moon several times. But intense competition during the Cold War unfolded in other, less visible areas. For example, in the aviation industry, where the Soviet design bureaus Mikoyan and Sukhoi competed with the American companies Boeing and Lockheed, who would quickly put the most advanced fighters of the fourth and then fifth generation into service in their countries. The arms race has touched on tanks, intercontinental ballistic missiles, aircraft carriers, and finally submarines. To gain an advantage over the Americans, Soviet engineers experimented and moved forward rapidly.
The titanium body of the Lira
In 1971, the USSR introduced the Project 705 Lira submarine. This nuclear attack submarine was notable for two things. Firstly, its body was made of titanium. Secondly, it has become one of the fastest in history. In fact, the Lira was inferior in speed to only one submarine, the Soviet prototype called K-222. The project 705 "Lira" was the first case of using titanium in the hull design.
Titanium is a chemical element from which it is possible to obtain a shiny transition metal with the most valuable properties: low density, high strength and resistance to seawater. It is clear that, given such properties, Soviet designers actively experimented with this material when designing their submarines.
Although the 705 project was launched only in 1971, the idea of a titanium submarine was first announced back in 1957. The project was designed to meet a number of strict requirements (under the banner of competition with American projects). Thus, the requirements stated that the new submarine must have sufficient speed to catch up with any ship if necessary. It must evade anti-submarine weapons systems, successfully conduct underwater combat, be poorly detectable, have the minimum possible displacement and have as small a crew as possible.
To meet all these requirements, a titanium alloy body was chosen. The idea was that it would provide low water resistance, low weight and, as a result, high speeds and great diving depths. The project 705 boat was supposed to be a kind of underwater "fighter-interceptor", which would hide in harbors or on the patrol route, and then, if necessary, quickly move forward to intercept enemy ships. The hull of the Lira, like most Soviet nuclear submarines, had a two-circuit design.
The sturdy inner hull withstood the enormous pressure of the ocean column, and the outer titanium protected the inner one and provided the best hydrodynamic shape. However, it turned out to be very difficult to implement a titanium case, like many other technological innovations. The light alloy turned out to be quite fragile — and the first submarine of the 705 project was written off due to cracks in the hull.
However, engineers were able to improve casting and welding technologies so much that the appearance of cracks in the housings on all subsequent models of the 705 project was eliminated. A high-tech reactor with a liquid metal lead-bismuth coolant and beryllium retardants was installed as a power plant at Project 705 with a titanium casing.
The liquid metal cooled reactor had a number of advantages over its water—cooled counterparts, including higher energy efficiency and lower weight and dimensions. But most importantly, it did not require refueling with active elements. The lead-bismuth cooled reactor (with all its weight and energy advantages) combined well with the titanium hull — both were aimed at creating a smaller and faster submarine.
The finished product was a submarine with a length of 81 meters, a width of 9.5 meters and a draft of 7.6 meters. The displacement of project 705 in the surface position is 2,300 tons, in the underwater position — 3,200 tons. The submarine could operate normally at depths of up to 350 meters, and the maximum permissible diving depth was about 1,300 meters. But the most impressive thing is that the 705 project could reach speeds of over 40 knots, and all this with a full set of torpedoes, cruise missiles and mines. In total, seven Project 705 Lira submarines were commissioned, the last of which remained in service with the Russian Navy until 1996.
Harrison Kass
