The original pad-launched versions of the R-12 and R-14 IRBM's had serious operational drawbacks. They couldn't be launched in winds of over 30 m/sec, and they were soft targets. Each truck had to drive several dozen kilometres from the technical point storage area to the hard stand pads, then several hours were needed to erect, fuel, and launch the rocket. During this time they were completely unable to withstand attack by enemy aircraft or missiles. Emplacing the missiles in hardened silos, able to withstand 0.02 Mpc (0.2 kgf/cm2) of overpressure, would allow them to survive a 1-megaton nuclear blast 5 km away.
Khrushchev took pride in the idea that he had originated the launch silo concept in the summer of 1958, but in fact it had been earlier considered for the enormous R-7 ICBM (and rejected for obvious economic reasons). However by 1958 it became apparent that such a concept was well suited to the new, smaller, storable-propellant missiles being developed by Yangel and Chelomei. The plan was for a single hardened launch control centre to control launch of the missiles from several silos. This would also allow salvo launch of missiles simultaneously (as opposed to reloading only one silo). In the case of the R-12, this required development of an R-12U 'universal' version of the missile (for either pad or silo launch), and the launch and command silos. Stand tests with the 'Dvina' silo complex began in March 1959 and construction of the Mayak 'lighthouse' silo at Kapustin Yar began in June 1959. The first launch of a missile from the Mayak complex was made on 31 August 1959, proving the silo-launch concept. The original Mayak design had a 7 m high 'kurgan' embankment formed from the earth of the excavation. This was visible for 10 to 15 km away in the flat steppes of Kapustin Yar, hence the term 'lighthouse'.
Based on results of these tests, a 14 June 1960 a decree authorised work to proceed on development of a silo-based version of the R-12 and its associated facilities. The R-12's 8P763 complex was code-named Dvina and designed by Spetsmash. It consisted of four silos grouped in a 70 x 80 m perimeter. At the centre was the hardened technological block, which housed the command point, the propellants and gases necessary for the missile, an electrical generator and necessary consumables for 30 days of autonomous operation at full launch readiness.
Aside from modifications to make the missile suitable for launch from either a silo or surface pad, the R-12U also had a more sophisticated guidance and control system. This allowed it to be equipped with only a single oxidiser tank, instead of the dual-tank system used for centre-of-gravity reasons on the original R-12.
Flight tests of the R-12U from launch pads were conducted between December 1961 and December 1962. The rocket design was accepted for military service on 12 July 1963. The first test of the R-12U from the Mayak silo was in October 1963. Following a successful test series the Dvina silo design was accepted by the military on 5 January 1964.
The first mobile R-12U regiment became operational at Plunge in Lithuania at the beginning of 1963. Each regiment consisted of 2-3 divisions, each division consisting of an emplacement with four launchers. Therefore a regiment had 8-12 launchers. Maximum deployment of all types of R-12 amounted to 608 launchers, but replacement of the R-12 by the Pioner solid propellant missile began in 1978. The last R-12U was destroyed under the INF Treaty that eliminated intermediate range nuclear weapons in Europe on 21 May 1990.
Standard warhead: 1,600 kg (3,500 lb). Maximum range: 2,150 km (1,330 mi). Number Standard Warheads: 1. Warhead yield: 2,300 KT. CEP: 2.40 km (1.40 mi). Boost Propulsion: Storable liquid rocket, IRFNA/Kerosene+UDMH. Initial Operational Capability: 1963.
AKA: SS-4 Mod 2; 8K63U; Sandal; Dvina.
Gross mass: 41,750 kg (92,040 lb).
Payload: 1,600 kg (3,500 lb).
Height: 22.00 m (72.00 ft).
Diameter: 1.65 m (5.41 ft).
Span: 1.83 m (6.00 ft).
Thrust: 637.00 kN (143,203 lbf).
Apogee: 402 km (249 mi).