Truth About the USS Vermont: Why North Korea Should Be Worried About This U.S. Submarine

Kim Yo Jong, Deputy Director of the Workers’ Party of Korea, recently referred to the U.S. Navy’s USS Vermont (SSN-792), docked in Busan, as a “nuclear strike asset.” Speaking through the Korean Central News Agency, she claimed that the submarine’s arrival at the Busan Operations Base was more than a routine deployment, calling it a provocative display of military power. She further asserted that the U.S. had revealed its “three major nuclear strategic assets,” referring to intercontinental ballistic missiles (ICBMs), strategic bombers, and Vermont’s appearance.

Kim accused the U.S. of exacerbating tensions on the Korean Peninsula, portraying the submarine’s visit as an act of escalation.

However, these claims reflect a fundamental misunderstanding of the USS Vermont and the broader role of U.S. submarines. The USS Vermont is a Virginia-class nuclear-powered attack submarine (SSN) designed for conventional missions such as anti-submarine and surface combat operations. It operates with a nuclear propulsion system but does not carry nuclear weapons, contrary to Kim’s assertions.

In this context, “nuclear” refers to its propulsion, not its payload. As such, the U.S. Navy does not classify the Vermont as a “strategic asset.” Its weaponry includes conventional torpedoes and cruise missiles, emphasizing versatility and precision in combat scenarios.

Understanding U.S. Submarine Types

Submarines are divided into nuclear and conventional types based on their propulsion systems. Conventional submarines use diesel engines and batteries and are used by countries including South Korea. Only six countries— the United States, the United Kingdom, France, Russia, China, and India—operate nuclear-powered submarines.

Currently, the U.S. Navy operates three types of submarines: SSN, SSGN, and SSBN. All share a standard nuclear propulsion system. SSN is a nuclear-powered attack submarine (Los Angeles-class, Virginia-class, Seawolf-class) primarily for anti-ship and anti-submarine warfare. SSGN is a nuclear-powered guided-missile submarine (Ohio-class) used for Tomahawk cruise missiles. For strike missions, SSBN is a nuclear-powered ballistic missile submarine (Ohio-class) used for strategic missions carrying SLBMs.

Among existing submarines, the SSBN is the largest and most heavily armed. The U.S. Navy first named it as a nuclear-powered submarine operating ballistic missiles. SS stands for Ship Submersible, B for Ballistic, and N for Nuclear. Next is the cruise missile nuclear submarine, SSGN, and the attack nuclear-powered submarine without ballistic missiles, SSN.

Nuclear-powered submarines are classified into several types based on their grade. There are three grades of attack submarines: Los Angeles-class, Seawolf-class, and Virginia-class. They are deployed for search-and-destroy missions, surveillance and reconnaissance, covert troop insertion, and mine placement and removal operations.

Los Angeles-Class: The Workhorse

The first submarine of this kind was the Los Angeles-class fast attack submarine. The first of its kind was commissioned in 1976, with 62 built. The last was the USS Cheyenne, commissioned in September 1996. The Los Angeles class is the most numerous nuclear submarine class globally. Except for one, all are named after U.S. cities like Albany, New York; Los Angeles, California; and Tucson, Arizona.

Notably, 23 Los Angeles-class submarines are designed to operate under ice. The hydroplane is located on the sail (the protruding part above the hull) rather than on the sides, allowing this capability. Currently, the U.S. operates 34 Los Angeles-class submarines. As of 2019, the manufacturing cost is $1.59 billion.

The displacement is 6,082 tons surfaced and 6,927 tons submerged. The length is 110 meters (361 feet) and uses a single S6G reactor (150–165 MW) for propulsion. The speed is 20 knots (23 mph) on the surface and submerged, and the submarine can dive to 90 meters (951 feet). The nuclear reactor has a lifespan of 30 years, allowing it to remain submerged for up to three months without surfacing.

Seawolf-Class: Silent and Lethal

Seawolf-class, equipped with 50 Tomahawk missiles

The Seawolf class was designed to succeed the Los Angeles class. Design work began in 1983, and 29 submarines were planned to be built over ten years. However, due to the end of the Cold War and budget constraints, this was reduced to 12. The fleet addition was canceled in 1995. Each Seawolf-class submarine costs about $3 billion.

The displacement is 8,600 tons surfaced and 9,138 tons submerged (USS Jimmy Carter is 12,139 tons). A single S6W reactor provides 57,000 horsepower (43 MW) of propulsion. The speed is 20 silently knots (37 km/h) with a maximum of 35 knots (65 km/h). It has unlimited range and can dive to a test depth of 490 meters (1,608 feet). It carries 50 Tomahawk land-attack missiles, Harpoon anti-ship missiles, and Mk 48 guided torpedoes. It is more significant, faster, and quieter than previous Los Angeles-class submarines. It also carries more weapons and has twice as many torpedo tubes.

Virginia-Class: The Future

Commissioned in 2004 and known as the SSN-774 class, the Virginia-class submarine is a nuclear-powered cruise missile fast attack submarine designed by General Dynamics Electric Boat (EB) and Huntington Ingalls Industries. It integrates stealth, intelligence gathering, and weapons systems technology, making it the latest submarine model for the U.S. Navy. The Navy plans to replace the Los Angeles-class submarines with Virginia-class submarines.

Equipped with electronic systems that enhance control capabilities, it has a fly-by-wire ship control system for precise maneuvering. The torpedo room can support special operation forces. The Virginia-class submarine replaces traditional periscopes with two photonics masts with visible and infrared digital cameras. The Virginia class has more space in the control room without needing a barrel periscope used in previous submarines.

As of 2023, the manufacturing cost is $3.5 billion. The length is 115 meters (377 feet) or 140 meters (459 feet). It uses an S9G reactor, generating 280,000 horsepower (210 MW). Two steam turbines provide 40,000 horsepower (30 MW). With unlimited range, the speed exceeds 25 knots (46 km/h). The test dive depth is 240 meters (787 feet). Designed for a broad range of open-ocean and littoral missions, it will be delivered to the Navy until 2043 and in service until at least 2060.

Ohio-Class: The Backbone of Strategic Deterrence

The Ohio-class submarine, in operation since 1981, is synonymous with strategic nuclear submarines in the U.S. Navy due to its performance upgrades. Known as “Boomers,” they are part of the U.S. strategic nuclear deterrence, capable of conducting underwater operations for several months. The Ohio-class submarines are the largest designed by the U.S. Navy. They include 14 ballistic missile submarines (SSBN) and four cruise missile submarines (SSGN), each with a displacement of 18,750 tons.

It ranks as the third-largest submarine globally, following the Soviet-designed 48,000-ton Typhoon and 24,000-ton Borei classes. The Ohio-class submarines carry 24 Trident II missiles, more than the 16 missiles on Russia’s Borei class and the 20 on the Typhoon class, making them significantly more powerful.

The Ohio-class SSBN is one of the three major nuclear deterrence assets, alongside the U.S. Air Force’s strategic bombers and the Army’s intercontinental ballistic missiles (ICBMs). The 14 SSBNs collectively carry about half of the U.S.’s active strategic thermonuclear warheads. They receive target attack orders from the United States Strategic Command in Nebraska.

The lead submarine of the Ohio class is the USS Ohio. It has a displacement of 16,764 tons surfaced and 18,750 tons submerged. Powered by an S8G reactor and equipped with two geared turbines, it has a propulsion of 35,000 horsepower (26 MW). The length is 170 meters (558 feet), with a surface speed of 12 knots (22 km/h) and a submerged speed of 25 knots (46 km/h). The test dive depth is 240 meters (787 feet), equipped with 22 launch tubes, each carrying seven Tomahawk cruise missiles, totaling 154.

Most notably, the Ohio class, often called a “monster,” will be replaced by the Columbia class starting in 2031. The upcoming next-generation U.S. nuclear submarine is drawing global attention.