SS-4 Sandal

R-12
CIA reference photograph of the Soviet R-12 (NATO designation SS-4) in Red Square, Moscow
Type	Medium-range ballistic missile
Service history
In service	4 March 1959-1993
Production history
Manufacturer	Yuzhmash
Unit cost	unknown
Specifications
Weight	41.7 t
Length	22.1 m
Diameter	1.65 m
Warhead	Thermonuclear
Blast yield	2.3 Mt
Engine	RD-214 635.2 kilonewtons (142,800 lbf)
Wingspan	9.65 ft
Propellant	liquid (AK-27I / TM-185)
Operational range	2,080 km
Speed	3,530 m/s
Guidance system	autonomous inertial
Launch platform	open-launch and silo-based

The R-12 was a theatre ballistic missile developed and deployed by the Soviet Union during the Cold War. Its GRAU designation was 8K63 (8K63U or 8K63У in Cyrillic for silo-launched version), and it was given the NATO reporting name of SS-4 Sandal. The R-12 rocket provided the capability to attack targets at medium ranges with a megaton-class thermonuclear warhead and constituted the bulk of the Soviet offensive missile threat to Western Europe. Deployments of the R-12 missile in Cuba caused the Cuban Missile Crisis in 1962. A total of 2335 missiles were produced; all were destroyed in 1993 under the Soviet and US Arms Control Treaty.

OKB-586 formed from a spin-off of portions of Sergei Korolev's OKB-1 production infrastructure under the direction of Mikhail Yangel in the early 1950s. Soon after, he started the development of an improved strategic missile that would outperform the R-5, SS-3 Shyster, that Korolev was in the process of bringing into production. Yangel's design was based on combining the basic airframe from the R-5 with an engine developed from the R-11. The R-11 was a short-range missile that used nitric acid as an oxidizer and kerosene as a fuel and could be stored for extended periods of time.

Valentin Glushko had long advocated using storable propellants, and proposed developing a new engine for the project. Earlier designs like the R-5 and R-7 used liquid oxygen as the oxidizer, and therefore had to be fueled immediately before launch, as the oxygen would "boil off" over time. He developed the RD-214 for the R-12, which consisted of four combustion chambers sharing a common turbopump assembly. The pumps were powered by decomposing the hydrogen peroxide, like earlier designs, to generate an exhaust. The new engine was too large to fit in the existing R-5 airframe, so a conical tail section was added to hold the engine.