SLBM

SLBM, acronym for submarine-launched ballistic missile, type of long-range guided missile that carries nuclear warheads to their targets. An SLBM is very similar to an ICBM (intercontinental ballistic missile), but instead of being fired from an underground silo or mobile missile launcher, it is fired from below the surface of the ocean from a ballistic missile submarine.

SLBMs were originally developed because submarines are ideal for missile launches. Most ICBMs are kept in fixed underground silos and therefore can be attacked. Submarines can better avoid detection and the threat of attack because they hide in the depths of the ocean and constantly move about. SLBM technology has improved steadily since the introduction of SLBMs in the late 1950s. With increased range, improved accuracy, and the introduction of MIRV (multiple independently targeted reentry vehicle) warheads, SLBMs are now as accurate as their land-based counterparts.

The latest United States SLBM is the Trident D-5 (sometimes called the Trident II), first deployed in March 1990. It has a range of over 7,400 km (4,600 mi) and is powered by a three-stage solid-fueled rocket engine. It is launched by the pressure of expanding gas within the launch tube of a submarine and can carry up to 15 MIRV warheads, each of which can be aimed at a different target. The Trident D-5 weighs 59,000 kg (130,000 lb), stands 13 m (44 ft) tall and is 2.1 m (6.9 ft) in diameter. Trident missiles are carried aboard Ohio-class submarines, and each boat can carry 24 missiles at a time.

The Soviet Union produced the first SLBM in the 1950s by modifying an existing liquid-fueled ICBM to fit within a submarine. The design was unwieldy, and the submarine had to surface in order to launch the missile. SLBM design and operation continued to improve, and in 1960 the United States tested the first underwater launch of a SLBM, the solid-fueled Polaris missile. Modern SLBMs are much larger and have greater accuracy and range than the early missiles. Russia, the United States, Great Britain, France, and China maintain formidable SLBM fleets.

See also Defense Systems; Cold War; Arms Control; Deterrence.