Missile R-12 Dvina (SS-4 Sandal)

The R-12 Dvina was a Soviet medium-range ballistic missile, designated 8K63 under the GRAU system (8K63U for the silo-launched variant) and assigned the NATO reporting name SS-4 Sandal. Design work began in the early 1950s, combining the airframe of the R-5 with an engine derived from that of the R-11 Zemlya, which used storable propellants rather than liquid oxygen and thus removed the need to fuel the missile immediately before launch. The design was approved by the Council of Ministers of the USSR, with sources citing either 13 February 1953 or 13 August 1955. The first test launch took place at Kapustin Yar on 22 June 1957. A launch witnessed there by the Soviet leadership in September 1958 was successful, and serial production began at Yuzhmash in Dnipropetrovsk the following month. Test launches through December 1958 showed a maximum error of 2.3 km. A total of 2,335 missiles were produced.

The R-12 is a single-stage rocket with a separable single reentry vehicle. Propulsion is provided by the RD-214, a liquid-propellant engine with four combustion chambers fed by a common turbopump assembly driven by decomposing hydrogen peroxide; propellants are AK-27I nitric acid oxidizer and TM-185 kerosene. The tanks are integrated, with the oxidizer forward of the fuel and separated by an intermediate plate so that oxidizer from the lower section is consumed first, improving in-flight stabilization. Thrust vector control is by four carbon jet vanes in the motor nozzles. Guidance is fully autonomous inertial, dispensing with the ground radio correction stations used on earlier Soviet missiles; the system incorporates normal and lateral centre-of-mass stabilization devices, velocity control, and computer-assisted automatic range control. The warhead is thermonuclear with a yield of 1.0–2.3 Mt, the standard fit being 2.3 Mt; conventional high-explosive and chemical warheads could also be carried. The missile was fielded at both soft launch pads and in silos.

Four readiness states were defined. At constant readiness the missile was held in a hangar without gyroscopes, warhead or propellant for up to seven years, requiring 3 hours 25 minutes to launch. At elevated readiness, with gyroscopes and warhead installed, it could be held three years and launched in 2 hours 20 minutes. At first-step elevated readiness the missile was moved to the launch site with gyroscopes started and initial data entered, held three months and launched in one hour. At total readiness it was fuelled and targeted but without starting gas loaded, held one month and launched in 30 minutes.

The R-12 entered service on 4 March 1959, though Western intelligence assessed initial operational capability in late 1958. It was operated solely by the Strategic Rocket Forces of the Soviet Union. The first five surface-launched regiments went on alert in May 1960, the first silo regiment in January 1963. The system was first publicly displayed in November 1960. Deployment of R-12 missiles to Cuba in October 1962 precipitated the Cuban Missile Crisis. Launcher inventory peaked at 608 in 1964–66; soft-site withdrawal began in 1968 and silo withdrawal in 1972, with replacement by the RSD-10 Pioneer starting in 1978. R-12s also served as targets during development of the V-1000 anti-ballistic missile, including two upper-atmosphere warhead detonations to test radar systems. Under the INF Treaty, the last of 149 remaining Soviet R-12s was eliminated at the Lesnaya Missile Elimination Facility in May 1990.