UGM-73 Poseidon

The UGM-73 Poseidon was the second nuclear-armed submarine-launched ballistic missile fielded by the United States Navy, a two-stage solid-fuel weapon that succeeded the UGM-27 Polaris and was followed by Trident I in 1979 and Trident II in 1990. Its main advance was the multiple independently targetable reentry vehicle: one missile could carry up to ten or fourteen W68 warheads against separate targets while keeping the 4,600 kilometre range of the Polaris A3. High-pressure steam from a solid-fuelled boiler ejected it from the launch tube, and the main motor ignited about ten metres above the surface. After its first test launch in 1968 it entered service on 31 March 1971, eventually equipped 31 Lafayette-, James Madison- and Benjamin Franklin-class submarines, and was withdrawn once the START I treaty took effect.