The UGM-73 Poseidon missile was the second

US Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

submarine-launched ballistic missile A submarine-launched ballistic missile (SLBM) is a ballistic missile capable of being launched from submarines. Modern variants usually deliver multiple independently targetable reentry vehicles (MIRVs), each of which carries a nuclear warhead ...

(SLBM) system, powered by a two-stage

solid-fuel rocket A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Arabs, Chinese, Persia ...

. It succeeded the

UGM-27 Polaris The UGM-27 Polaris missile was a two-stage solid-fueled nuclear-armed submarine-launched ballistic missile (SLBM). As the United States Navy's first SLBM, it served from 1961 to 1980. In the mid-1950s the Navy was involved in the Jupiter missi ...

beginning in 1972, bringing major advances in warheads and accuracy. It was followed by

Trident I The UGM-96 Trident I, or Trident C4, was an American submarine-launched ballistic missile (SLBM), built by Lockheed Martin Space Systems in Sunnyvale, California. First deployed in 1979, the Trident I replaced the Poseidon missile. It was retire ...

in 1979, and

Trident II A trident is a three- pronged spear. It is used for spear fishing and historically as a polearm. The trident is the weapon of Poseidon, or Neptune, the God of the Sea in classical mythology. The trident may occasionally be held by other marine ...

in 1990.

Development

A development study for a longer range version of the Polaris missile—achieved by enlarging it to the maximum possible size allowed by existing launch tubes—started in 1963. Tests had already shown that Polaris missiles could be operated without problems in launch tubes that had their

fiberglass Fiberglass ( American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cl ...

liners and locating rings removed. The project was given the title Polaris B3 in November, but the missile was eventually named Poseidon C3 to emphasize the technical advances over its predecessor. The C3 was the only version of the missile produced, and it was also given the designation UGM-73A. Slightly longer and considerably wider and heavier than Polaris A3, Poseidon had the same range, greater payload capacity, improved accuracy, and

multiple independently targetable reentry vehicle A multiple independently targetable reentry vehicle (MIRV) is an exoatmospheric ballistic missile payload containing several warheads, each capable of being aimed to hit a different target. The concept is almost invariably associated with i ...

(MIRV) capability. MIRV capacity has been given as up to either ten or fourteen

W68 The W68 warhead was the warhead used on the UGM-73 Poseidon SLBM missile. It was developed in the late 1960s at Lawrence Livermore National Laboratory. Specifications The W68 weighed and had an official design yield of . The design was revol ...

thermonuclear warheadsPoseidon C3 at MissileThreat.com
contained in Mark 3 reentry vehicles to multiple targets. As with Polaris, starting a rocket motor when the missile was still in the submarine was considered very dangerous. Therefore, the missile was ejected from its launch tube using high pressure steam produced by a solid-fueled boiler. The main rocket motor ignited automatically when the missile had risen approximately above the submarine. The first test launch took place on 16 August 1968, the first successful at-sea launch was from a surface ship, the (from July 1 to December 16, 1969), earning the ship the

Meritorious Unit Commendation The Meritorious Unit Commendation (MUC; pronounced ''muck'') is a mid-level unit award of the United States Armed Forces. The U.S. Army awards units the Army MUC for exceptionally meritorious conduct in performance of outstanding achievement or ...

, and the first test launch from a submarine took place on the on 3 August 1970. The weapon officially entered service on 31 March 1971. It eventually equipped 31 -, -, and -class submarines. The Royal Navy also considered adopting Poseidon in the 1970s as an upgrade to its Polaris A3T boats, and like the US this would have kept the existing hulls. Although the Navy's favoured option, the British government instead adopted

Chevaline Chevaline () was a system to improve the penetrability of the warheads used by the UK Polaris programme, British Polaris nuclear weapons system. Devised as an answer to the improved Soviet Union, Soviet A-35 anti-ballistic missile system, anti- ...

, a two warhead MRV system with decoys, on the existing Polaris airframes and later moved to the Trident D5 in new boats. Beginning in 1979, 12 Poseidon-equipped SSBNs were refitted with

. By 1992, the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...

had collapsed, 12

Ohio-class submarine The ''Ohio'' class of nuclear-powered submarines includes the United States Navy's 14 ballistic missile submarines (SSBNs) and its four cruise missile submarines (SSGNs). Each displacing 18,750 tons submerged, the ''Ohio''-class boats are the ...

s had been commissioned, and the

START I START I (Strategic Arms Reduction Treaty) was a bilateral treaty between the United States and the Soviet Union on the reduction and the limitation of strategic offensive arms. The treaty was signed on 31 July 1991 and entered into force on 5 De ...

treaty had gone into effect, so the 31 older Poseidon- and Trident I-armed SSBNs were disarmed, withdrawing Poseidon from service.

Operators

* **

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

Gallery

References

{{Authority control Cold War weapons of the United States Nuclear weapons of the United States Cold War submarine-launched ballistic missiles of the United States Lockheed Corporation UGM-073 Military equipment introduced in the 1970s

Development

Operators

Gallery

See also

References