R-21 / SS-N-5 SERB
The R-21 / SS-N-5 submarine-launched ballistic missile is a single-stage, storable liquid-propelled missile. The D-4 launch system used the "wet launch" technique, under which the missile tube had to be filled with water before launch. The missiles could be fired underwater and were intended to replace the D-2 launch system on board Golf class submarines. According to Western intelligence estimates, the missile could deliver a 2800-lb reentry vehicle having a 2.0-3.5 MT warhead a maximum operational range of 700 nm. It had an inertial guidance system, and a CEP estimated by western intelligence of 1 to 2 nautical miles.
The SS-N-5 was carried aboard both the Golf-II Class diesel-electric submarine, which was believed to be assigned a peripheral mission, and the Hotel-II Class nuclear submarine, which were assigned a strategic mission. Both submarines can launch missiles while fully submerged and underway at about five knots. The normal reaction time is 15 to 20 minutes, and their action time under conditions of peak alert is one to two minutes. The allowable hold time under peak alert conditions is about one hour. Initial operational capability was reached in 1963.
The project to construct an underwater launched missile started as early as 1955 and concentrated on the R-11FM missile. On 03 February 1955, E.V. Charnko, the chief designer of OKB-10 NII-88, was assigned responsibility of developing the missile, and the chief designer of SKB-626, N.A. Ryemihatov, was responsible for developing the submarine infrastructure.
The development program conducted in three phases. First, R-11FM dummies were fired from a fixed underwater tube, followed by dummy launches from tubes located on the outside of the submarine, and finally full scale test firing from a sailing submarine. For pop-up tests, two R-11FM dummies were designed: the ?4.1 and the C4.5. The first missile launch from an underwater platform was conducted on 23 December 1956. The specially modified "S-229" Whiskey submarine, re-designated B-613, conducted tests with a dummy missile while the submarine was submerged at a depth of 15-20 meters and sailing at a speed of 3-4 knots. Three ?4.1. dummy launches were conducted in the Black sea in June 1957.
The development of the new D-4 launch system with R-21 missiles was authorized in March 1958. Originally, OKB-586 and its chief designer M.K. Yangel was charged with the project but in March 1959 the program was transferred to SKB-385.
After the development of the R-21 missile was authorized in 1958, the R-11FM missile continued in use for further tests. The modified R-11FM, designated C4.7, was used in the third series tests, of launches from submerged submarines that began in July 1959. Prior to the conclusion of the second phase of tests, the Ministerial Council had directed that converted "B-67" V-611 submarines carry out the third test phase. The first ?4.7 missile firing in August 1959 from the "B-67" submarine was a failure, delaying further tests by a year. The second test flight in August 1960 also ended in failure when the tube filled with water and the missile fell from the launch pad and crushed its nose cone. The third submarine launch on 10 September 1960 was successful.
The K1.1 missile, a less powerful experimental version of the R-21 SS-N-5 SERB missile, was tested in parallel to the C4.7 test program. Pop-up tests of the K1.1 missile were conducted in the Black Sea from a 40-50 m deep fixed floating platform and the "S-229" submarine. Six launches from a platform and three from a submarine were carried out between May 1960 and October 1961. The K1.1 missile was publicly displayed in parades in Red Square, and incorrectly identified in the West as the SS-N-5 SERB. In fact, it was a prototype missile tested in association with the development of the operational SS-N-5.
The 629B Golf II submarine was built for testing the D-4 launch system, Joint testing began in February 1962 and the first underwater launch took place on 24 February 1962. A total of 27 missile launches were conducted during these tests.
On 15 May 1963 deployment of the D-4 launch system on Golf and Hotel submarines began. The R-21 remained in operational service from 1963 to 1989, during which time 193 out of a total of 228 launches were successful. Over this period the service life of the fueled missile was increased from six months to two years.