Delta-class submarine
The Delta class, (Russian: Дельта) Soviet designations Project 667B "Murena", Project 667BD "Murena-M", Project 667BDR "Kalmar", Project 667BDRM "Delfin", (NATO reporting names Delta I, Delta II, Delta III, Delta IV respectively) are a series of nuclear-powered ballistic missile submarines, designed and built in the Soviet Union, which formed the backbone of the Soviet and Russian strategic submarine fleet since their introduction in 1973. They carry nuclear ballistic missiles of the R-29 Vysota family, with the Delta I, Delta II, Delta III and Delta IV classes carrying the R-29 (NATO reporting name: SS-N-8 'Sawfly'), R-29D  (SS-N-8 'Sawfly'), R-29R (SS-N-18 'Stingray') and R-29RM (SS-N-23 'Skiff') respectively. The Delta I class carried 12 missiles, while the Delta II class which are lengthened versions of the Delta I class carry 16 missiles. The Delta III and Delta IV classes carry 16 missiles with multiple warheads and have improved electronics and noise reduction. The R-27 Zyb missile carried by the s of the late 1960s had a range of , so the earlier submarines were forced to patrol close to the North American coast, whereas the Deltas could launch the over -range R-29s from the relative safety  of the Arctic Ocean. In turn the Deltas were superseded by the larger s. The early Deltas remained in service until the 1990s with treaties such as START I. High running costs and the retirement of the Typhoons R-39 missiles meant that some Delta III-class submarines were reactivated in the 2000s (decade) to replace the Typhoons. In December 2010, Pavel Podvig at Russianforces.org estimated the strength of the Russian strategic submarine fleet at one Typhoon-class submarine (used to test the RSM-56 Bulava missile), four Delta III, six Delta IV class, and one strategic missile submarines. They will ultimately  be replaced by the new Borei class, also referred to as the "Dolgorukiy" class. Development. In the 1960s the Soviet Navy wanted new submarine-launched nuclear missiles that could threaten targets in North America without their launch platforms needing to pass the SOSUS sensors in the GIUK gap to be within range. Delta I (Project 667B "Murena") 18 boats. The Delta-class submarines could deploy on alert patrols in the marginal ice-seas of the Soviet Arctic littoral, including the Norwegian and Barents Seas. Consequently, unlike their predecessors, they no longer needed to pass through Western SOSUS sonar barriers to  come within range of their targets. To improve the accuracy of the missiles, the Delta I-class submarines carry the Tobol-B navigation system and the Cyclone-B satellite navigation system. After authorization of the development of the class in 1965, the first Delta I, , was commissioned into the Soviet Northern Fleet on 22 December 1972. A total of 18 submarines of this class were built, and all served Soviet Navy, under the designation Project 667B "Murena" ("Eel"). In 1991, nine Delta I-class submarines were still in active service. Their decommissioning began in 1994, with removal of the missile  compartments scheduled by 1997. All submarines of this class were taken out of service by 1998 and were scrapped by 2005. Delta II (Project 667BD "Murena-M") 4 boats. The Delta II-class submarine was a large ballistic missile submarine designed to remedy shortcomings in the Delta I-class submarine. The design was essentially the same, but the submarine was lengthened in the fourth and fifth compartments by to allow the installation of four more missile tubes. The new type of Delta also received additional quieting measures including having the steam turbines mounted on shock absorbers, having all pipes and  hydraulics separated from the hull through rubber insulation, and a special hydroacoustic coating being applied to the hull. The NATO reporting name, Delta II indicates this submarine as a visually distinguishable new class. The Soviet designation, 667BD "Murena-M" indicates this submarine is an improved Delta I. Only four submarines of this class were built, apparently in favor of building the following class, the Delta III, and all Delta IIs were out of service by 1996. Delta III (Project 667BDR "Kalmar") 14 boats. The 667BDR "Kal'mar" ("Squid") Delta III-class submarine is a large ballistic missile submarine. Like the earlier  Delta-class submarines the Delta III class is a double-hulled design with a thin, low magnetic steel outer hull wrapped around a thicker inner pressure hull. Development began in 1972 at the Rubin Central Design Bureau for Marine Engineering. The submarine was the first that could launch any number of missiles in a single salvo, as well as the first submarine capable of carrying ballistic missiles with multiple independently targetable reentry vehicles. The submarine carried 16 of the R-29R missiles each carrying 3 to 7 MIRVs, with a range of , depending on the number of re-entry vehicles. The  Delta III class was also equipped with a new battle management system the Almaz-BDR for the fire control of torpedoes in deep-water, also a new inertial navigation system Tobol-M-1, and later the Tobol-M-2. A hydroacoustic navigational system called "Shmeľ" ("Bumblebee") allows the submarine to determine its position from hydroacoustic buoys. Finally a new sonar system called Rubikon was fitted. On 30 September 2008 a Russian Navy spokesman reported that "Ryazan" had successfully completed a 30-day transit from a base in northern Russia under the Arctic ice cap to a base on the Kamchatka Peninsula. The  Navy added that "Ryazan" will soon be assigned to regularly patrol the Pacific Ocean. In July 2008, six Delta III-class boats were active, of which two were believed to be in the process of decommissioning. K-433 "Svyatoy Georgiy Pobedonosets" was involved in a collision with a fishing vessel on 22 September 2011. The submarine did not sustain serious damage. Delta IV (Project 667BDRM "Delfin") 7 boats. Seven Delta IV-class submarines were built; all are still in service in the Russian Navy. The submarines, based at the Sayda Guba Naval Base, operate in the Northern Fleet. The Severodvinsk Shipyard  built these vessels between 1981 and 1992. The last vessel was . The design of the Delta IV class resembles that of the Delta III class and constitutes a double-hulled configuration with missile silos housed in the inner hull. The submarines have an operational diving depth of , with a maximum depth of . The propulsion system allows speeds of submerged using two VM-4 pressure water reactors rated at 180 MW. It features two turbines of type GT3A-365 rated at 27.5 MW. The propulsion system drives two shafts with fixed-pitch propellers. On 29 December 2011, a shipyard fire broke out in  the drydock where a Delta IV-class vessel named "Ekaterinburg" was being serviced. It was reported that the fire managed to spread to the submarine, that all weapons were disembarked from the submarine and the nuclear reactor was shut down beforehand. Overall design. The submarines' design is similar to that of Delta III class (Project 667 BDR). The submarines constitutes a double-hulled configuration with missile silos housed in the inner hull. The forward horizontal hydroplanes are arranged on the sail. They can rotate to the vertical for breaking through the ice cover. The propulsion system provides a speed of  surfaced and submerged. The submarines carry supplies for an endurance of 80 days. The surface of the submarines has an acoustic coating to reduce the acoustic signature. During the development of the 667BDRM SSBN, several measures were included to reduce its noise level. The gears and equipment are located on a common base isolated from the pressure hull, and the power compartments are also isolated. The efficiency of the anti-hydroacoustic coatings of the light outer hull and inner pressure hulls have been increased. Newly designed propellers with improved hydroacoustic characteristics are employed. See the Delta III class overview for  specifications. Armament. The Delta IV-class submarines employs the D-9RM launch system and carries 16 R-29RMU Sineva liquid-fueled missiles which each carry four independently targetable reentry vehicles (MIRVs). Unlike previous modifications, the Delta IV-class submarine is able to fire missiles in any direction from a constant course in a circular sector. The underwater firing of the ballistic missiles can be conducted at a depth of while cruising at a speed of . All the missiles can be fired in a single salvo. The 667BDRM "Delfin" submarines are equipped with the TRV-671 RTM missile-torpedo system that has four torpedo  tubes with a calibre of . Unlike the Delta III-class design, it is capable of using all types of torpedoes, anti-submarine torpedo-missiles and . The battle management system Omnibus-BDRM controls all combat activities, processing data and commanding the torpedo and missile-torpedo weapons. The "Shlyuz" navigation system provides for the improved accuracy of the missiles and is capable of stellar navigation at periscope depths. The navigational system also employs two floating antenna buoys to receive radio-messages, target destination data and satellite navigation signals at great depth. The submarines are also equipped with the Skat-VDRM hydroacoustic system . The Delta IV-class submarines are strategic nuclear missile submarines, designed to carry out strikes on military and industrial installations and naval bases. The submarines carry the RSM-5 Makeyev (NATO reporting name: SS-N-23 Skiff) submarine-launched ballistic missile (SLBM). The RSM-54 is a three-stage liquid-propellant ballistic missile with a range of . The warhead consists of four to ten multiple, independently targeted re-entry vehicles (MIRVs) each rated at . The missile uses stellar inertial guidance to provide a circular error probable (CEP) of . The CEP value is a measure of the accuracy of strike on the target and  is the radius of the circle within which half the strikes will impact. The submarines are also capable of launching the Novator SS-N-15 Starfish anti-ship missile or anti-ship torpedoes. Starfish is armed with a nuclear warhead and has a range of up to . The submarines have four 533 mm torpedo tubes capable of launching all types of torpedoes, including anti-submarine torpedoes and anti-hydroacoustic devices. The system is fitted with a rapid reloading torpedo system. The submarines can carry up to 12 missiles or torpedoes. All torpedoes are accommodated in the bow section of the hull . In 2011 K-84 "Ekaterinburg" successfully tested a new version of the SS-N-23 missile, reportedly designated R-29RMU2 Layner. The missile has improved survivability against anti-ballistic missiles. Later on K-114 "Tula" conducted another successful launch. Deployment. Initially all the Delta IV-class submarines were based with the Russian Northern Fleet at Olenya Bay. All the submarines of this class serve in 12th Squadron (the former 3rd flotilla) of strategic submarines of the Northern Fleet, which now located in Yagelnaya Bay.