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A fractional orbital bombardment system (FOBS) is an orbital nuclear weapons delivery system that inserts a payload into an orbital trajectory from which a reentry vehicle (RV) is deorbited. The Soviet Union attempted twenty-four FOBS test launches between 1965 and 1971 and deployed the system operationally from 1969 to 1983. FOBS are now prohibited under the Strategic Arms Reduction Treaty (START I) of 1991.

The earliest concrete proposal for this type of system originated from Soviet Chief Designer Sergey P. Korolev, who began preliminary work on the so-called Global Missile 1 (GR-1) in 1960. For Korolev, the GR-1 was part of the plan to develop a booster for the Soviet manned lunar effort. By 1962–1963, the U.S.S.R. had at least three major orbital weapons projects: the GR-1, a second FOBS project headed by General Designer Vladimir N. Chelomey, and a third by Mikhail K.Yangel’s design bureau. In early 1965, prior to full testing of any system, the Strategic Rocket Forces conducted a comparative analysis and selected the Yangel option. After the twentieth test launch attempt, in August 1969 the first battalion of FOBS (R-36-O missiles) was put on combat duty at Tyuratam, located in Kazakhstan. In 1982, the U.S.S.R. began to dismantle the R-36-O, and the last missile was removed from duty in February 1983. Estimates on the yield of the FOBS warhead vary from between 2 and 20 megatons, and it was assessed to be able to hit within 3 to 5 kilometers of its intended target.

The apparent purpose of the FOBS was to provide the U.S.S.R. with more attack planning flexibility and options. The system could, for example, be used to strike the United States from the south, the direction with the fewest strategic early warning sensors. Secretary of Defense Robert S. McNamara publicly announced the existence of the system in November 1967 but attempted to downplay its significance, denying that it posed a major new strategic threat to the United States or violated the 1967 Outer Space Treaty, since the nuclear payloads were not in sustained orbit.

References Siddiqi, Asif A., “The Soviet Fractional Orbital Bombardment System: A Short History,” available at html. Stares, Paul B., The Militarization of Space: U.S. Policy, 1945–1984 (Ithaca, NY: Cornell University Press, 1985).



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