Alfa-class submarine

Alfa-class SSN profile
An Alfa-class submarine underway
Class overview
Name	Alfa class
Operators	Soviet Navy  Russian Navy
Preceded by	Victor class
Succeeded by	Sierra class, Akula class
Built	1968–1981
In commission	1971–1996
Planned	8[1]
Completed	7
Cancelled	1
Retired	7
General characteristics
Type	Nuclear attack submarine
Displacement	2,300 tons surfaced 3,200 tons submerged
Length	81.4 m (267 ft)
Beam	9.5 m (31 ft)
Draught	7.6 m (25 ft)
Propulsion	OK-550 or BM-40A, 155-MWt Lead-bismuth cooled, beryllium-moderated reactor 40,000 shp (30,000 kW) steam turbine, one shaft[2]
Speed	12 kn (14 mph; 22 km/h) surfaced 41 knots (47 mph; 76 km/h) submerged[1][2]
Test depth	350 m (1,148 ft) test[2]
Complement	31 (all officers)[1][2]
Armament	6 × 533 mm (21 in) torpedo tubes (bow): 18 SET-65 or 53-65K torpedoes 20 VA-111 Shkval torpedoes 24 mines

The Alfa class, Soviet designation Project 705 Lira (Russian: Лира, meaning "Lyre", NATO reporting name Alfa), was a class of nuclear-powered attack submarines in service with the Soviet Navy from 1971 into the early 1990s, with one serving later with the Russian Navy until 1996. They were among the fastest military submarines ever built, with only the prototype submarine K-222 (NATO reporting name Papa-class) exceeding them in submerged speed.^[3]

The Project 705 submarines had a unique design among other submarines. In addition to the revolutionary use of titanium for its hull, it used a powerful lead-bismuth cooled reactor as a power source, which greatly reduced the size of the reactor compared to conventional designs, thus reducing the overall size of the submarine, and allowing for very high speeds. However, it also meant that the reactor had a short lifetime and had to be kept warm when it was not being used. As a result, the submarines were used as interceptors, mostly kept in port ready for a high-speed dash into the North Atlantic.