Cutaway of RT-20P. Key to cutaway: Orange=UDMH; Green=N2O4; Brown=Solid propellant.
Credit: © Mark Wade
AKA: 8K99;Scrooge;SS-15. Status: Retired 1969. First Launch: 1967-10-20. Last Launch: 1969-08-07. Number: 12 . Payload: 545 kg (1,201 lb). Thrust: 600.00 kN (134,880 lbf). Gross mass: 30,200 kg (66,500 lb). Height: 17.80 m (58.30 ft). Diameter: 1.60 m (5.20 ft). Apogee: 1,000 km (600 mi).
The draft project for the mobile-launch system was completed in December 1966.
Yangel's experience with solid propellant motors went back to research begun in November 1960. By 1963 Yangel created a subsidiary, KB-5, at the Pavlograd Mechanical Factory. V M Shkurenko was in charge of the bureau, which began a series of tests on the premises of the factory, leading up to the first large-scale motor test firing in January 1964. In February 1966 KB-5 was reorganized to concentrate exclusively on R&D for solid motors, with the new head V I Kusushkin (who would remain at that position for thirty years). The motor for the RT-20P itself was based on a design originally developed for TsSKB-7 Arsenal's D-6 SLBM. Boris Zhukov developed the four-nozzle motor at NII-125.
The second stage used the RD-857 / 15D12 liquid engine developed at Yuzhnoye's KB-4 by Ivan Ivanov. The motor used the traditional N2O4/UDMH propellants, and was later upgraded to the 15D169 used on the MR-UR-100 ICBM. The stage itself had the unusual designation 8K94, usually used for a stand-alone missile. Perhaps it was originally designed for the same mobile IRBM requirement as Korolev's 8K79.
The mobile version used a T-10M tank chassis from the KB-3 Leningrad Kirov Factory, headed by Zhozef Kotin. A 15P699 launch unit would consist of six of these transporters; one 15N809 position determination and guidance upload vehicle; two 15N1034 marker vehicles to complete determination of launch position; two 15P694 diesel generator vehicles; and a 'Relef' communications vehicle. The launcher vehicle was shown publicly in the big Moscow parade on 7 November 1967 and given multiple designations by Western intelligence agencies - a sure sign of confusion (SS-X-15 / SS-XZ / Scrooge).
A team headed by B G Bochkov at KBEM studied the 15P096 silo-launched system. Two versions of the OS-SM-CP20 launch silo were considered in the 1966 draft project in order to ensure survival of the missile even after near misses by enemy nuclear warheads. One version used a shock attenuation system, the other use of a suspended mounting ring on which the missile rested.
In all versions a 250 kg cold gas cartridge ejected the missile to an altitude of 20 to 30 m before ignition of the first stage. This represented the first use of this technique, later adopted for all Soviet ICBM's. Navigation was by an inertial navigation system using advanced air bearing gyroscopes.
The missile could be fitted with two possible warheads. Three small rocket engines were used for warhead separation. The heavy re-entry vehicle, with a total mass of 1410 kg and a yield of 1.5 MT, was expected to provide an accuracy (CEP) of 2 km at a range of 8,000 km. The light warhead, with a mass of 545 kg and a yield of 550 KT, allowed a 4 km CEP at an 11,000 km range. However by the beginning of the test series, it seemed that these ranges would be only 5,000 and 7,000 km respectively. This made the missile only marginally 'intercontinental', since only targets in the northeast United States (e.g. New York) could be hit with the light warhead from any practical deployment locations in the northwest Soviet Union (e.g. Plesetsk).
Nevertheless development continued and flight trials started at Plesetsk in October 1967. A total of 8 or 12 launches were completed when the project was cancelled in October 1969. The stated reason for the cancellation was unease of the military leadership in having nuclear-tipped missiles rumbling around the countryside.
Stage Data - RT-20P
|8K94 stage N2O4/UDMH propellant rocket stage. Unusual designation for the upper stage of another Yangel project - possibly reflecting that the design originally was a stand-alone IRBM? Empty mass estimated.|
|RT-20P in Moscow|
RT-20P mobile launcher paraded in Moscow, 1967.