Soviet`s Alfa class, Project 705, world fastest and deepest boat ever built   The Project 705 Alfa class/Soviet`s Lira constituted the world`s fastest and deepest diving submarines of their time. The submarine featured a high power to weight reactor to increase the power to weight and volume ratios of her propulsion plant, the first use of titanium for the hull, extensive automation, and advanced drag-reduction configuration. Project 705 originated in a 1957 requirement for a 1,500ton `interceptor` submarine capable of a speed of 40 knots that would sortie to attack American aircraft carriers. Using a titanium alloy allowed the thickness and weight of the hull to be reduced, producing a remarkably small, very fast submarine. Around 1963 the design was substantially revised, with the displacement was increased to 2,300tons, the number of internal compartments increased from three to six and the size of the crew was doubled. Construction of the first Project 661 prototype unit began around 1965, which was completed at the Sudomekh shipyard, Leningrad in 1972. The prototype was rebuilt after trials, and subsequently broken up around 1974. Made from titanium alloys, it could accelerate to a speed of 44.7knots, a record which will hardly be beaten in the near future. Although a much-feared design in the West, these concerns were prompted by grossly exaggerated accounts of the boat`s capabilities and an assumption that they represented the main thrust of Soviet submarine development. The fast, deep diving nuclear submarine threat proved a false alarm, but they provoked massive investments in ASW-Anti Submarine Warfare weapons by the US Navy, and resulting in dramatic improvements in the Mk. 46 and Mk. 48 torpedoes that apparently culminated in the 63knot ADCAP torpedo. Extremely noisy at high speeds, the noise levels of the Alfa at lower speeds were generally similar to that of other Soviet SSNs-nuclear powered submarines. Though extremely fast, the boats were unreliable, poorly armed and with sensors that were unique, hard to maintain and frequently defective. Two different models of liquid metal (probably lead-bismuth) reactors were used. The four boats built at the Admiralty shipyard used the BM-40A reactor with two separate steam loops and circulating pumps. The boats built at Severodvinsk, Project 705K, used the OK-550 with branched first-loop lines and triple circulating loops and pumps. The reactors required a heater to prevent the liquid metal coolant from solidifying. In 1972 the reactor on K-377 suffered a casualty during sea trials and the metal coolant "froze" destroying the reactor. In 1982 the reactor on K-316 was destroyed when the heating system was accidentally turned off. A special facility was constructed the submarines were moored to supply superheated steam to heat the liquid metal when the reactors were shut down. External heating proved unsatisfactory, and the reactors had to be kept running even while the submarines were in port. Series production of the Project 705 boats began in the mid-1970s, and the program ended in 1983 with the sixth production unit. Eventually four of the seven Project 705s were lost due to reactor failures. One boat was retired by the end of 1987, and four others were decommissioned in 1990-1992. Two Alfas were modified with VM-4 pressurized water reactors from Project 671B and used for test activities prior to being decommissioned in 1995. Specifications, Alfa class, Project 705: The lead boat was probably launched on April 22, 1969-birth date of V.I. Lenin. Double-hull configuration with a titanium pressure hull, the world first submarine built of that material. The submarine`s ultra- high-speed hull design (note the length-to-beam ratio) includes a streamlined sail that is `blended` into the hull. Displacement (srf/sub tons): 2,950/3,680 Dimensions (L*B*D feet): 267`0*31`2*23`0 Propulsion: 1*155MWt OK-550 or BM-40A Liquid-Metal nuclear Reactor (LMR), 2*geared steam turbines 45,000hp, one shaft 5 bladed propeller Speed (sub knots): 43+ Range (srf/sub miles@knots): not relevant Diving depth (feet): 1,970-2,500 (600-760m) Complement: 30-45 officers and crew Missile: SSM sub-launched anti-ship missiles, 21*81R ( SS-N-15) or 12*Vodopad (SS-N-16) Torpedo: 6*21" (533mm) bow torpedo tubes, torpedo type 53-65K or SET 65,total mixture of 18 missiles or torpedoes Armament: none Mines: 24 mines in lieu of torpedoes Back to History Index     Image Country Year Description Guinea-Bissau 2001 Alpha class (type 705), SSN