Somewhere beneath the surface of the world’s oceans, right now, an American submarine is on patrol. You cannot see it or hear it, no satellite can easily track it, and no radar can find it. That invisibility is the whole point. For more than seventy years, the Navy’s submarine fleet has been America’s quietest and most survivable source of power at sea.
Every submarine in the American fleet is nuclear powered. A nuclear reactor needs no air to run, so a submarine does not need to surface or snorkel to recharge batteries the way older diesel boats did. It can stay submerged for months, limited mainly by the food it carries and the endurance of its crew, and cross oceans at sustained speed while hidden.
This guide explains the fleet in plain language: the three kinds of submarines America operates, how they work, what each one is for, and where the fleet is heading with the new Columbia class. If you have ever wondered why the Navy calls its next ballistic-missile boat its number one acquisition priority, this is the story.
The Three Types of American Submarines
The U.S. submarine force is split into three types. Fast-attack submarines, known as SSNs, hunt other ships and submarines, gather intelligence, and launch cruise missiles at targets ashore. Ballistic-missile submarines, known as SSBNs and nicknamed boomers, carry submarine-launched ballistic missiles and form the sea-based leg of America’s nuclear deterrent. Guided-missile submarines, known as SSGNs, carry large numbers of conventional cruise missiles and support special operations forces.
The letters in those hull codes tell the story: SS means submarine, N means nuclear powered, and the final letter describes the mission, N for attack, B for ballistic missile, and G for guided missile. Every boat is built for stealth first. A submarine that can be found easily has already failed at its main job, so quieting, the science of making a boat as silent as possible, shapes almost every design decision, from the shape of the hull to the way machinery is mounted inside it.
According to the Navy’s submarine force, the fleet today includes 53 fast-attack submarines, 14 ballistic-missile submarines, and four guided-missile submarines. Those numbers shift slowly as boats retire and new ones commission, so treat any total as a snapshot. The structure stays the same: a small number of boomers carrying the deterrent, a larger force of attack boats doing the everyday work, and a handful of guided-missile boats packing an outsized punch. You can read the Navy’s own force overview on its Submarine Facts page.
Attack Submarines: The Hunters of the Fleet
Fast-attack submarines conduct the most diverse missions in the submarine force: seeking and destroying enemy submarines and surface ships, projecting power ashore with Tomahawk cruise missiles and special operations forces, gathering intelligence, supporting battle groups, and engaging in mine warfare. In practice, one deployment might mean quietly tracking another submarine, the next launching cruise missiles in support of a joint operation, and the next delivering Navy SEALs close to a hostile shore.
Three classes of attack submarines are in service. The Los Angeles class has been the backbone of the force for decades, with about 24 boats now in commission and vertical launch tubes for Tomahawk cruise missiles. The Seawolf class is a small group of just three boats, built for exceptional speed, depth, and quieting, and prized for the hardest undersea missions. The Virginia class is the modern standard, and the Navy says 24 Virginia-class boats have been commissioned so far, steadily replacing Los Angeles-class boats as they retire.
The Virginia class shows how submarine design has evolved. The lead boat, USS Virginia, was commissioned on October 3, 2004, and the class was designed for both open-ocean and coastal operations. Later boats replaced twelve individual vertical launch tubes with two large Virginia Payload Tubes, each able to launch six Tomahawk cruise missiles. The newest variant adds the Virginia Payload Module, a hull section with four more large payload tubes, each carrying seven Tomahawks, adding 28 missiles per boat, plus room for future payloads such as large unmanned underwater vehicles. The Navy’s full description is in its attack submarine fact file.
What makes an attack submarine so useful is its flexibility. A carrier strike group is powerful but visible; a submarine is powerful and invisible, so it can go places a surface ship cannot, watch without being watched, and act without warning. That is why attack boats are often the first American assets in a crisis region and the last to leave.
Ballistic-Missile Submarines: The Boomers
If attack submarines are the fleet’s hunters, ballistic-missile submarines are its insurance policy. The Navy calls SSBNs, often referred to as boomers, an undetectable launch platform for submarine-launched ballistic missiles, designed specifically for stealth and the precise delivery of nuclear warheads. Their mission is nuclear deterrence: convincing any adversary that a nuclear attack on the United States would be answered, no matter what else had been destroyed.
That logic rests on a simple idea. Land-based missiles sit in known locations and bombers on known airfields, but a boomer on patrol is hidden somewhere in millions of square miles of ocean, and no adversary can be sure of finding it before it can launch. That survivability makes the sea-based leg widely regarded as the most survivable part of America’s nuclear triad of land-based missiles, bombers, and submarines, and the Navy has noted that its ballistic submarines carry a majority share of the nation’s nuclear deterrent arsenal.
Today the only SSBN in service is the Ohio class, with fourteen boats in commission, from USS Henry M. Jackson to USS Louisiana. Each Ohio-class boat originally carried up to 24 submarine-launched ballistic missiles, but under the New Strategic Arms Reduction Treaty, four missile tubes on each boat were permanently deactivated, so each now carries a maximum of 20. The strategic weapon is the Trident II D5 missile, which replaced the earlier Trident I. An Ohio-class crew numbers 15 officers and 144 enlisted sailors, and the boats are designed for extended deterrent patrols, operating for fifteen or more years between major overhauls. The details are set out in the Navy’s ballistic-missile submarine fact file.
Life on a boomer is defined by routine and silence. Patrols last for months, with the crew working rotating watches around the clock while the boat stays submerged and out of contact for long stretches. It is demanding, isolating work. The reward for that discipline is a deterrent that has never had to be used, which is precisely the point.
Guided-Missile Submarines: The Heavy Hitters
Guided-missile submarines sit between the attack boats and the boomers. They carry no nuclear ballistic missiles; instead, they carry large numbers of conventional Tomahawk cruise missiles, able to strike targets hundreds of miles inland with precision, and provide dedicated support for special operations forces, with room aboard for SEAL teams and their equipment.
Four Ohio-class boats were converted into guided-missile submarines, each able to carry up to 154 Tomahawk missiles, making them the most heavily armed conventional strike submarines ever operated. But those converted boats are aging, and the Navy has begun retiring them, starting with USS Georgia in the summer of 2026 after more than four decades of service.
Their successors are already taking shape. In August 2026, the Navy announced that Virginia-class submarines fitted with the Virginia Payload Module will be reclassified as guided-missile submarines, reflecting their much larger strike capacity. Nineteen such boats are covered by the change, spanning the Block V and Block VI boats planned for delivery through the late 2030s. The line between an attack submarine and a guided-missile submarine is blurring, because the new attack boats carry so much firepower that they deserve the heavier designation. The U.S. Naval Institute’s Submarines of the Navy survey tracks exactly this transition.
How Nuclear Power Makes It All Possible
To understand the submarine fleet, you have to understand its engine. A nuclear-powered submarine carries a pressurized-water reactor that produces heat, which makes steam, which drives turbines and turns the propeller. The reactor needs no oxygen and no fuel deliveries at sea, so the boat’s endurance is limited mainly by food and crew stamina, not by fuel.
The revolution began with USS Nautilus. Commissioned on September 30, 1954, Nautilus was the world’s first nuclear-powered submarine, and on the morning of January 17, 1955, her commanding officer sent the famous message, underway on nuclear power, as she put to sea. In August 1958, Nautilus became the first vessel to reach the geographic North Pole while submerged, a voyage unthinkable for a diesel boat. Today she is preserved as a museum ship at the Submarine Force Library and Museum in Groton, Connecticut.
Nuclear power also brings responsibility: reactors are maintained to exacting standards, and refueling takes a boat out of service for years. The Columbia class is designed to avoid mid-life refueling entirely, with a reactor built to last the boat’s whole service life, which should keep the new boats available for patrol more often than the Ohio class they replace.
Stealth: The Submarine’s Real Weapon
Ask a submariner what a submarine’s most important weapon is, and the answer is often silence, because every other capability depends on not being found. Modern American boats are shaped to slip through the water with minimal turbulence, coated with sonar-absorbing materials, and fitted with machinery mounted on isolators so vibrations do not reach the hull. Even the propeller is designed to avoid cavitation, the bubbles that can betray a boat’s position.
Stealth is also a matter of discipline. Crews train to minimize noise, and sonar operators listen for hours, learning to distinguish the sounds of the ocean, of marine life, and of other vessels. In the undersea world, hearing matters more than seeing, and the side that hears first usually wins.
The Columbia Class: The Future of the Fleet
The biggest story in the submarine fleet today is the Columbia class, the Navy’s next ballistic-missile submarine. The Navy calls it the nation’s future sea-based strategic deterrent and its number one acquisition priority, designed to replace the Ohio class as those boats reach the end of their service lives.
Twelve Columbia-class boats are planned, each carrying 16 Trident II D5 missiles. That is fewer tubes than the Ohio class, but improved missiles and more flexible planning preserve the deterrent capability. The lead boat, USS District of Columbia, is under construction at General Dynamics Electric Boat in Groton, Connecticut, with Newport News Shipbuilding as a partner, and the second boat, Wisconsin, is also under construction. The Navy says the class must be ready for patrol no later than October 2030 to meet U.S. Strategic Command requirements, and that it will provide continuous sea-based deterrence into the 2080s, as the largest, most capable, and most advanced submarine the nation has ever produced.
The schedule is tight, and Congress has been watching it closely. The Congressional Research Service, in its report on the Columbia-class program, notes the program has been the Navy’s top priority since 2013, and that the first boat’s delivery has slipped, with the Navy now working toward delivery in 2028. The Ohio boats, their service lives extended to 42 years, are due to retire one per year as the Columbias arrive, and in the summer of 2026 the Navy awarded a major contract modification covering five more Columbia-class boats.
The Columbia is also a test of American shipbuilding. Only two shipyards in the country can build nuclear-powered submarines, and both are busy. The Navy, the shipyards, and their suppliers are working to expand the workforce, stabilize the supply chain, and deliver boats on a rhythm of one per year. Whether that rhythm holds will shape the deterrent for the next half-century.
Life Aboard: The Silent Service
Submariners call their community the Silent Service, and the nickname fits. Crews cannot talk about where they have been or call home whenever they like. They live for months in a steel tube with no windows, no sunlight, and no personal space to speak of, sharing bunks in rotating shifts in a practice sailors call hot racking, where a bunk is still warm from the last occupant when the next sailor climbs in.
Why Submarines Matter to American Power
Step back from the technical details and the strategic picture comes into focus. The United States is a maritime nation, and its trade, alliances, and ability to respond to crises all depend on free use of the seas. Submarines protect that freedom in ways no other platform can, operating in contested waters where surface ships would be at risk, gathering intelligence without revealing themselves, and holding an adversary’s most valuable targets at risk from an unknown direction.
That matters more now than it has in decades, as rival navies build larger submarine fleets of their own. The American answer is a qualitative edge: quieter boats, better sensors, better trained crews, and the industrial base to keep building.
Building nuclear submarines is slow, expensive, and dependent on a specialized workforce, and maintenance backlogs have kept boats in shipyards longer than planned. But demand from commanders around the world remains high, because no other asset does what a submarine does.
Frequently Asked Questions
How many submarines does the U.S. Navy have?
The Navy’s submarine force has described the fleet as 53 fast-attack submarines, 14 ballistic-missile submarines, and four guided-missile submarines, but the size changes as boats retire and new ones commission, so treat any total as a snapshot.
What is the difference between an SSN, an SSBN, and an SSGN?
An SSN is a nuclear-powered attack submarine that hunts ships and submarines, gathers intelligence, and launches cruise missiles. An SSBN is a nuclear-powered ballistic-missile submarine that carries submarine-launched ballistic missiles for deterrence. An SSGN is a nuclear-powered guided-missile submarine that carries large numbers of conventional cruise missiles and supports special operations forces.
Why are all U.S. submarines nuclear powered?
Nuclear power lets a submarine stay submerged for months without surfacing for air or fuel, since a reactor needs no oxygen to run. That is the core advantage over diesel-electric submarines, which must surface or snorkel to recharge their batteries.
What is the Columbia-class submarine?
The Columbia class is the Navy’s next ballistic-missile submarine, planned as twelve boats to replace the fourteen Ohio-class SSBNs. The lead boat, USS District of Columbia, is under construction now, and the Navy says the class must be ready for patrol no later than October 2030.
Can the public visit a real U.S. Navy submarine?
Yes. USS Nautilus, the world’s first nuclear-powered submarine, is preserved as a museum ship at the Submarine Force Library and Museum in Groton, Connecticut, and other decommissioned submarines are preserved as museums around the country. Active-duty submarines are not open to the public.