Trident ballistic missile

The Trident missile is a submarine-launched ballistic missile (SLBM) equipped with multiple independently targetable reentry vehicles (MIRV). Originally developed by Lockheed Missiles and Space Corporation, the missile is armed with thermonuclear warheads and is launched from nuclear-powered ballistic missile submarines (SSBNs). Trident missiles are carried by fourteen US Navy Ohio-class submarines, with US warheads, and four Royal Navy Vanguard-class submarines, with British warheads. The missile is named after the mythological trident of Neptune.

In 1971, The US Navy began studies of an advanced Undersea Long-range Missile System (ULMS). A Decision Coordinating Paper (DCP) for the ULMS was approved on 14 September 1971. ULMS program outlined a long-term modernization plan, which proposed the development of a longer-range missile termed ULMS II, which was to achieve twice the range of the existing Poseidon (ULMS I) missile. In addition to a longer-range missile, a larger submarine (Ohio-class) was proposed to replace the James Madison and Ben Franklin class SSBNs in 1978. The ULMS II missile system was designed to be retrofitted to the existing SSBNs, while also being fitted to the proposed Ohio-class submarine.

In May 1972, the term ULMS II was replaced with Trident. The Trident was to be a larger, higher-performance missile with a range capacity greater than 6000 mi.

Trident I (designated as C4) was deployed in 1979 and retired in 2005. Its objective was to achieve performance similar to Poseidon (C3) but at extended range. Trident II (designated D5) had the objective of improved circular error probable, and was first deployed in 1990, and was planned to be in service for the thirty-year life of the submarines, until 2027.

...
Wikipedia