This article is about the missile. For the spear, see Trident.
The Trident missile is a long-range, multiple independently targetable reentry vehicle (MIRV) submarine-launched ballistic missile (SLBM) used by the United States and the United Kingdom. They are armed with nuclear warheads and are currently carried on fourteen active United States Navy Ohio-class submarines and four Royal Navy Vanguard-class submarines.
Two varieties of the Trident were built:
Trident I (C4)
The C4 was introduced in 1979 and was fitted on the first ten Ohio-class submarines, as well as the James Madison and Benjamin Franklin classes, replacing Poseidon missiles. It was phased out by 1990 in favor of the more powerful D5.
Trident II (D5)
The Trident D5 was constructed as a strategic nuclear weapons platform to destroy Soviet land-based missiles in case of a Soviet first strike.
It can carry a heavier payload and has a greater range.
D5 life extension
In 2002, the United States announced a plan to extend the original 2027 retirement date to 2042. The D5 Life Extension Program is currently underway; it is attempting to replace key navigational and reentry systems at minimum cost.