In September 2017, the ship builder Electric Boat was awarded $5 billion to proceed with the design phase of the next-generation of U.S. nuclear-powered ballistic-missile submarines, also known as SSBNs or “boomers.” A dozen Columbia-class submarines will start replacing the fourteen enormous but stealthy Ohio-class boats that constitute the scariest weapon system in the United States’ arsenal.
Ballistic-missile subs are basically a vengeful kind of life-insurance policy for the nation—one that hopefully will never be called due. If the United States were confronted by an existential threat—i.e., a nuclear attack—then just a few boomers could rain nuclear warheads on every major city or military base in a hostile nation. This is because each SSBN carries over a dozen Submarine-Launched Ballistic Missiles (SLBMs) that can be fired from underwater to hit targets far across the planet. While in flight, these Trident missiles split into multiple independent nuclear warheads (MIRVs) that each can land on a separate target.

The intent in producing such apocalyptic death machines is not so much to use them, but to deter other nations from using their own nuclear weapons (which may also be launched by SSBNs). In this role, submarines stand as the most reliable leg of the nuclear triad; while an opponent might imagine that they can knock out nuclear-armed bombers and land-based missile silos with a surprise first strike, there is no chance that they could locate all of an adversary’s patrolling SSBNs dispersed across the globe, running quietly in the depths of the ocean for months at a time without surfacing. The Navy even maintains a fleet of aircraft specifically assigned to transmit nuclear launch codes to submarines via low-frequency radios in the event of an emergency.

The current Ohio-class submarines serve very well as highly stealthy, mobile nuclear missile silos. Built with the capacity to launch twenty-four SLBMs, the type happens to be the most heavily armed SSBN class ever made. Because the basic formula for a ballistic missile submarine is well established by now, the Columbia class will seek to perform that same mission more efficiently, and even more quietly to keep pace with advances in antisubmarine warfare.

source: nationalinterest.org