RT-20P / SS-15 SCROOGE
The RT-20P missile was the first Soviet mobile ICBM, although Western sources generally viewed the SS-X-15 as a theater-range ballistic missile rather than a true ICBM. Western intelligence correctly determined that the missile had a storable liquid-propellant second stage, but could not precisely determine whether the first stage used liquid or solid propellants. Western intelligence was also puzzled, at least initially, as to whether the RT-20P was a two or three-stage system.
The RT-20P was, in fact, a two-stage missile which was unique in that it used dissimilar solid and liquid propellants in the first and second stages. The first stage used a solid propelled engine which featured four rotating nozzles to conduct flight control. The second stage was liquid propelled sustainer using asymmetrical dimethylhydrazine and nitrogen tetraoxide in a single chamber. The flight control of the missile was attained by injecting spent turbine gas into the diverging section of the four sustainer nozzle.
The missile was designed by KB Yuzhnoye (OKB-586) completing the design in December 1964 and its developmement officially approved in August 1965. Although the missile was first displayed in the Moscow parade of November 1965, the flight test program did not begin until October 1967. The first test that was connected to the program by Western intelligence was detected in late February 1968. Nine test launches were conducted from the Plesetsk test site with a total of eight being detected .the program apparently was abandoned following a successful flight in August 1967. The development of the RT-20P missile was officially halted in October 1969, and the SS-X-15 was not deployed operationally.
According to Russian sources, the RT-20P, had a launch weight of 30.2 tons and could either carry a payload of 545 kg delivering a single warhead with a yield of 550 Kt up to 11,000 km, or a payload of 1410 kg and a 1.5 Mt warhead up to 8,000 km. Western sources believed that the missile was capable of delivering a 1000-lb reentry vehicle to a range of 5,300 nm with a CEP of 1.0 to 1.5 nm.
During the development of the RT-20P three different basing modes were considered: road-mobile, railway and silo, with road-mobile basing system being actually developed. The missile was placed in a transport-launch canister and fired from a motorized launcher derived from the heavy T-YUM tank. The missile was launched from its canister using the mortar launch technique.
A new command structure substantially increased the time the missile could be maintained in an operational mode. The missile had an inertial guidance system, and the development of new high-precision gyroscopic devices allowed for improved accuracy as well as improved capability for remote input of mission data.
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