A submarine-launched ballistic missile (SLBM) is a ballistic missile capable of being launched from submarines. SLBMs almost exclusively carry one or multiple nuclear warheads, and play an important role in nuclear strategy as a highly reliable and non-vulnerable second strike option. Nuclear-armed SLBMs are operated by China (JL-3), France (M51), India (Sagarika), Russia (Sineva, Lajner, and Bulava), the United Kingdom and the United States (both Trident II). South Korea is the only nation developing a conventionally-armed SLBM, the Hyunmoo 4-4. SLBMs typically have similar ranges and designs to intercontinental ballistic missiles (ICBMs), which range over 5,500 kilometres (3,000 nmi). Modern variants favor solid propellant and usually deliver multiple independently targetable reentry vehicles (MIRVs), each of which carries a strategic nuclear warhead and allows a single launched missile to strike several targets. SLBMs typically use a combination of inertial and celestial navigation systems. Some SLBMs have also been used in a tactical nuclear weapon role, such as the United States W76 Mod 2 warhead mated to the UGM-133 Trident II missile. The Soviet Union tested the world's first SLBM, the R-11FM, in 1955, and became the first country to operate ballistic missile submarines with the R-11FM in 1956. The United States Navy first developed the UGM-27 Polaris, operational from 1961. The Polaris A-3 was the first missile to use multiple re-entry vehicles, a nuclear cluster munition. The US Navy remains the largest operators of SLBMs, with 280 Trident II missiles, followed by the Russian Navy with 192 total SLBMs.
History
Origins The first practical design of a submarine-based launch platform was developed by the Germans near the end of World War II involving a launch tube which contained a V-2 ballistic missile variant and was towed behind a submarine, known by the code-name Prüfstand XII. The war ended before it could be tested, but the engineers who had worked on it were taken to work for the United States (Operation Paperclip) and for the Soviet Union on their SLBM programs. These and other early SLBM systems required vessels to be surfaced when they fired missiles, but launch systems were adapted to allow underwater launching in the 1950–1960s. A converted Project 611 (Zulu-IV class) submarine launched the world's first SLBM, an R-11FM (SS-N-1 Scud-A, naval variant of the SS-1 Scud) on 16 September 1955. Five additional Project V611 and AV611 (Zulu-V class) submarines became the world's first operational ballistic missile submarines (SSBs) with two R-11FM missiles each, entering service in 1956–57. The United States Navy initially worked on a sea-based variant of the US Army Jupiter intermediate-range ballistic missile, projecting four of the large, liquid-fueled missiles per submarine. Rear Admiral W. F. "Red" Raborn headed a Special Project Office to develop Jupiter for the Navy, beginning in late 1955. However, at the Project Nobska submarine warfare conference in 1956, physicist Edward Teller stated that a physically small one-megaton warhead could be produced for the relatively small, solid-fueled Polaris missile, and this prompted the Navy to leave the Jupiter program in December of that year. Soon Chief of Naval Operations Admiral Arleigh Burke concentrated all Navy strategic research on Polaris, still under Admiral Raborn's Special Project Office. All US SLBMs have been solid-fueled while all Soviet and Russian SLBMs have been liquid-fueled except for the Russian RSM-56 Bulava, which entered service in 2014.
The world's first operational nuclear-powered ballistic missile submarine (SSBN) was USS George Washington with 16 Polaris A-1 missiles, which entered service in December 1959 and conducted the first SSBN deterrent patrol November 1960 – January 1961. George Washington also conducted the first successful submerged SLBM launch with a Polaris A-1 on 20 July 1960. Fifty-two days later, the Soviet Union made its first successful underwater launch of a submarine ballistic missile in the White Sea, on 10 September 1960 from the same converted Project 611 (NATO reporting name Zulu-IV class) submarine that first launched the R-11FM. The Soviets were only a year behind the US with their first SSBN, the ill-fated K-19 of Project 658 (Hotel class), commissioned in November 1960. However, the Hotel class carried only three R-13 missiles (NATO reporting name SS-N-4) each and had to surface and raise the missile to launch. Submerged launch was not an operational capability for the Soviets until 1963, when the R-21 missile (SS-N-5) was first backfitted to Project 658 (Hotel class) and Project 629 (Golf class) submarines. The Soviet Union was able to beat the US in launching and testing the first SLBM with a live nuclear warhead, an R-13 that detonated in the Novaya Zemlya Test Range in the Arctic Ocean, doing so on 20 October 1961, just ten days before the gigantic 50 Mt Tsar Bomba's detonation in the same general area. The United States eventually conducted a similar test in the Pacific Ocean on 6 May 1962, with a Polaris A-2 launched from USS Ethan Allen as part of the nuclear test series Operation Dominic. The first Soviet SSBN with 16 missiles was the Project 667A (Yankee class), which first entered service in 1967 with 32 boats completed by 1974. By the time the first Yankee was commissioned the US had built 41 SSBNs, nicknamed the "41 for Freedom".
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