US Navy Submarines: What Does 'SLBM' Stand For?

SLBMs, short for Submarine Launched Ballistic Missile, have been a cornerstone of America's strategic deterrence since the 1960s. They serve as part of America's nuclear triad, ensuring the country always has defensive measures against nuclear weapons.

The U.S. Navy currently arms its SSBNs (ship, submersible, ballistic, nuclear) with Lockheed Martin's Trident II D5 LE missiles. The weapons manufacturer first delivered the Trident II in 1990 to the U.S. Navy for its Ohio-class submarines as well as the British Royal Navy's Vanguard-class sub. It's a particularly intimidating missile that's 44 feet long, 83 inches in diameter, weighs 130,000 lbs., and has a 4,000 nautical mile  range. Moreover, each missile can house multiple W76-0/1/2 and W88 nuclear warheads. They sit aboard as the best unused weapon in the U.S. arsenal that silently stalks the world's oceans.

The first ballistic missile used by the U.S. Navy was the Polaris (A1) missile. It could only carry one nuclear warhead and had a fraction of the range that the Trident II has; 1,200 nautical miles. The second generation Polaris (A2) also only carried a single nuclear warhead, but it had an improved range of 1,700 nautical miles. The third generation Polaris missile (A3) had the biggest upgrade with the ability to carry three W-58 nuclear warheads and travel up to 2,500 nautical miles. Lockheed developed the Polaris's successor — the Poseidon missile — improving its capability. This missile weighed nearly twice the amount of Polaris (A3), could travel roughly 3,300 nautical miles, and was armed with 14 nuclear warheads.

The first American sub armed with an SLBM was the USS George Washington (SSBN-598). Today, a whole different class of submarine in America's surprisingly large fleet is armed with SLBMs. As one of the most advanced nuclear submarines in the world, the Ohio-class sub is armed with a maximum of 20 Trident II D5 missiles. It used to hold 24, but the New Strategic Arms Reduction Treaty between the U.S. and Russia required limits on the number of SLBMs subs could carry. The Ohio-class submarine is an SSBN, an acronym that' means "Ship, Submersible, Ballistic, Nuclear," but they're generally called ballistic missile submarines or fleet ballistic missile submarine. Navy personnel, however, tend to refer to them as boomers.

Boomers are designed for stealth, to lurk beneath the waterline and provide a global launch capability. There's a total of 18 Ohio-class subs, but only 14 of them are boomers. The first four of the class were converted into guided missile submarines (SSGN), which don't carry nuclear weapons anymore. The U.S. Navy is currently in the process of replacing the Ohio-class with the more advanced and larger Columbia-class SSBN.

The first Columbia-class submarine to be delivered to the navy will be the USS District of Columbia (SSBN-826) and should be ready to replace the first retired Ohio-class boomer in 2027. Lockheed Martin is ensuring that the Trident II D5 missile is modernized and ready to operate on this new submarine class.