FOBS (Fractional Orbital Bombardment System) was an orbital variant of the Soviet R-36 intercontinental ballistic missile, known in Russia as the R-36O (see "R" series of Russian missiles) and intended to deliver nuclear warheads from space. The Western designation "FOBS" refers to the fact that although the payloads reached orbit, they were intended to reenter over their targets prior to completing a full circuit of the Earth. Four suborbital FOBS tests were carried out between December 1965 and May 1966. These were followed by more tests through 1971, delivering 5-ton payloads into low Earth orbit. FOBS is a direct ancestor of the modern-day commercial Tsyklon launch vehicle.