Submarine-Launched Ballistic Missiles (SLBM)

Following World War II, a new threat emerged from the Cold War rivalry between the U.S. and the nuclear-capable Soviet Union. The first U.S. response was to field bombers capable of delivering atomic and later hydrogen bombs against targets in Soviet territory, thereby deterring Soviet ambitions. Later, U.S. defense evolved to encompass the "Strategic Triad" approach, a highly-survivable trio of nuclear delivery options including bombers, inter-continental ballistic missiles (ICBM), and submarine-launched ballistic missiles.

Underwater launch of Trident II SLBM
Underwater launch of Trident II SLBM.

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The U.S. Navy Fleet Ballistic Missle Program

The Strategic Triad deterrent assured that no first strike could eliminate the U.S. retaliatory capability and created a stable world order that endured until the rise of terrorist organizations in the late 20th century. The implementation of the deterrent relied heavily on the invulnerable Fleet Ballistic Missile Program.

The Fleet Ballistic Missile Program is the formal name for the Submarine-Launched Ballistic Missile program, that is, nuclear warhead missiles launched from submerged or surfaced submarines. The U.S. Navy's FBM program started in 1956 and has been continuously deployed at sea as a survivable retaliatory force, a key element of the Strategic Triad concept.

Regulus Submarine-Launched Ballistic Missile

The first submarince launched missile program was "Regulus," the forerunner of the Tomahawk cruise missile and not a ballistic missile. The submarine-launched, turbojet-powered Regulus missiles were specifically designed to carry nuclear warheads. Regulus I was first launched at sea in March 1953 by the converted USS Tunny (SSG-282), which could house two missiles in a pressurized hangar. The missile had a range of about 500 nm. By mid-1958, USS Grayback (SSG-574) and USS Growler (SSG-577) had been commissioned as the first purpose-built Regulus submarines, each carrying two in a large bow hangar. At that time, the Navy had four SSGs and four missile-carrying cruisers at sea.

USS Halibut (SSGN-587) was the first nuclear powered submarine specifically designed to carry and launch missiles. Commissioned in January 1960, she could carry four Regulus II missiles in a hangar integral with the hull. The Regulus submarines had to prepare and fire their missiles on the surface and then to stay at periscope depth to exercise command guidance, a severe limitation.

Polaris A-3 on stand
Polaris A-3 on stand.

Polaris Submarine-Launched Ballistic Missile

Polaris was the first true submarine-launched ballistic missile (SLBM), developed under RADM William F. Raborn starting in November 1955. The Polaris missile and a new class of nuclear-powered ballistic missile submarines to carry them were developed together based on new technology for warheads, propulsion and the nuclear submarine.

USS George Washington (SSBN-598), was the first of the first five-ship class of ballistic missile submarines, on patrol November 1960, only five years after Raborn began the effort and five years after the first U.S. nuclear submarine, the Nautilus, was launched. The first successful underwater launch of a Polaris missile occurred from the Washington in July 1960.

The first SSBNs carried 16 Polaris missiles, with 41 boats deployed by 1965. Polaris went through several models in the program lifetime:

  • Polaris A-1, 1200 nm. range
  • Polaris A-2, 1600 nm. range (first sub launch, October 1961)
  • Polaris A-3, 2500 nm. range (first sub launch, October 1963)

The A-3 fit in the same launch tubes as the older Polaris models, but was revolutionary in that it had three warheads, designed to strike in a pattern (not MIRV). A total of 33 subs were equipped with A-3 missiles, including retrofit of the original five A-1 boats. The photo above, left shows a Polaris A-3 on a test stand at Pad 19A, Cape Canaveral, FL, 26 July 1962.

Poseidon Submarine-Launched Ballistic Missile

Polaris was followed by Poseidon C-3, based on Polaris technology and able to fit the same tubes. Poseidon was larger and heavier than Polaris and was equipped with multiple independently targetable reentry vehicles (MIRVs). After flight testing starting in 1968, it was first sub-launched in August 1970 from the USS James Madison and first operationally deployed on the Madison in March 1971.

The USS Lafayette (SSBN-616) was the first "FBM Lafayette" class nuclear-powered, ballistic missile submarines designed for Poseidon. Lafayette-class boats had 16 launch tubes for Poseidon nuclear missiles.

Trident I Submarine-Launched Ballistic Missile

For longer range and greater survivability, the Navy started development in 1968 on a larger SLBM to replace the aging Polaris/Poseidon inventory. This became the Trident, which required a new and larger class of ballistic missile submarines, beginning with USS Ohio (SSBN-726), commissioned in November 1981. Ultimately, the Ohio class would number 18 ships, the last of which entered service in June 1997.

The Trident I C-4 became operational in 1978, with range almost double that of the Poseidon missile it replaces:

Dimensions 74 x 408 in.
Weight 70,000 lbs.
Warhead Eight 100-kT MK 4 MIRV
Propulsion Solid-fuel rocket
Range 4,350 nm.

The first eight Ohio class submarines were originally equipped with 24 Trident I C-4 ballistic missiles. Twelve of the remaining 31 Lafayette Class fleet ballistic missile submarines in the fleet also were converted to Tridents.

Trident II Submarine-Launched Ballistic Missile

The Trident II D-5 was larger, heavier and with longer range than the Trident I:

Dimensions 83 x 528 in.
Weight 130,000 lbs.
Warhead Eight to 12 MK-5 RV or 14 150-kT MIRV or 7 300-kT MARV
Propulsion Three-stage, solid-fuel rocket
Range 6,000 nm.

The first deployment of Trident II was in 1990 on the USS Tennessee (SSBN 734), the ninth Trident submarine. Beginning with the Tennessee, all new ships are equipped with the Trident II D-5 missile system as they are built, and the earlier ships are being retrofitted to Trident II. Trident II can deliver significantly more payload than Trident I, more accurately, and over longer distance.

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