By The 18 Ohio-class ballistic-missile submarines are some of the most exceptional military machines in human history, packing more nuclear or conventional firepower than any other platform on air, land, or sea.
One leg of America’s nuclear triad, the subs are designed to be ultra-quiet, bristle with nuclear weapons, and survive to carry out their mission at all costs. The 14 nuclear-armed Ohio-class submarines ensure that hundreds of nukes are resting quietly in the world’s oceans, ready to enact a devastating reprisal against any surprise attack on the United States.
Here’s what makes them so incredibly badass.
Nuclear Weapons Go to Sea
In the 1950s, the United States placed much of its faith in its ability to deter war on nuclear weapons. The U.S. Navy struggled to find a reliable deployment strategy for nukes at sea, at first turning to large rockets or cruise missiles that would be launched from a surfaced submarine. Unfortunately, early efforts led to ungainly missiles that required highly modified submarines, and took considerable preparation to prepare for launch.
By 1960, the Navy had developed the Polaris A-1 submarine-launched ballistic missile (SSBN) and ballistic-missile submarine. The Polaris A-1 was a short, squat missile with a range of 1,400 miles, and whose solid rocket fuel motors were chemically stable enough to remain stored in the missile for long periods of time. It carried three warheads, each with the explosive yield of 200 kilotons of TNT. (By comparison, the Hiroshima bomb had only a 15-kiloton yield.)
The Polaris missiles were compact enough to be stored, one per silo, in two rows of eight silos each per missile submarine, for a total of 16 missiles. Although the missile’s limited range meant the submarines needed to venture close to the Soviet Union, the solution was elegant enough that submarine-launched ballistic missiles became, like bombers and intercontinental ballistic missiles, one of the three main legs of the nuclear triad.
Enter the Ohio Class
In the 1970s, the Navy began planning its fifth series of ballistic-missile submarines. At 560 feet long and 18,750 tons submerged, the Ohio class would be the largest American submarines ever built. A typical crew consists of 15 officers and 140 enlisted. The submarines are officially described as being able to dive to 800 feet, but in reality, that number is understood to be greater than 1,500 feet.
A single General Electric S8G nuclear reactor, turning two steam turbines, provides up to 60,000 horsepower to each sub. The Ohio class, streamlined to operate entirely underwater, can travel at speeds of 30+ knots, and remain submerged indefinitely, with their stay limited only by food and water for the crew.
In addition to their nuclear armament, each of the subs is equipped with four 533-millimeter torpedo tubes. As missile submarines, their primary mission was to remain undetected, but if forced into a fight with a Soviet submarine, a missile boat had to retain the ability to return fire and destroy its attacker. The primary torpedo over the Ohio class’ lifetime has been the Mk-48 guided torpedo, now upgraded to the Mk-48 ADCAP (advanced capability.)
The Nukes
As ballistic-missile submarines, the primary armament of the Ohio class are their submarine-launched ballistic missiles, stored in an elevated position behind the sail. The first eight Ohio-class submarines were built with their silos filled with Trident C-4 missiles; Trident C-4 weighed 73,000 pounds, could carry up to eight Mk-4 reentry vehicles, and had a maximum range of 4,000 nautical miles.
Trident C-4 was eventually replaced with Trident II D-5, which weighs 130,000 pounds, and can carry up to 12 Mk-4 reentry vehicles. The Navy states that the D-5 has a range of 4,000 nautical miles, but this seems unlikely given that the missile is nearly twice as heavy as its predecessor, yet carries only four more warheads. The Center for Strategic and International Studies estimates the true range at about 6,500 nautical miles—enough range to strike nearly every target in the northern hemisphere.
Each Mk-4 reentry vehicle carries a single thermonuclear warhead. Almost all of the warheads are W-76-1 warheads with a yield of 90 kilotons; that’s the equivalent of 90,000 tons of TNT. Each Trident D-5 can carry up to 12 warheads, though the number actually deployed today, in relative peacetime, is believed to be just 4–5.
In 2020, the U.S. introduced a new, low-yield variant of the W-76: the W-76-2, each of which has a yield of 4–5 kilotons. An estimated 1–2 Tridents per deployed submarine carries a single W-76-2 warhead.
Blue and Gold
The 14 Ohio-class ballistic-missile submarines run at a high tempo to keep as many as possible at sea at any given time. Between two and four submarines are in drydock at any one time; the rest of the subs are going out on patrol, returning from patrol, training, or actively on nuclear-deterrence patrol.
This tempo is achieved by doubling the number of crews assigned to any one ship. Unlike other warships, Ohio-class submarines typically operate with two separate crews, Blue and Gold, composed of 15 officers and 144 enlisted men and women each. This allows the submarines to deploy more frequently—and on shorter notice, if necessary.
During the Cold War, missile submarines spent as much as 60–70 percent of their time at sea. Due to the declining threat, the average Ohio-class submarine now conducts an average of 2.3 patrols per year, down from 4.1 per year at the height of the Cold War. Each patrol lasts an average of 70 days, much shorter than for other ships.
Arms Control and a New Course
On April 8, 2010, the United States and Russia signed the New Strategic Arms Reduction Treaty (New START), which limited the number of deployed strategic nuclear weapons to 1,550 and nuclear weapons delivery systems to 700. In the case of the Ohio class, each warhead on each Trident II D-5 missile counted as a nuclear weapon, while each missile counted as a delivery system.
Theoretically, the entire fleet of 18 Ohio-class submarines could sortie with as many as 24 missiles, each with 12 warheads each; that could amount to a total of 5,184 nuclear weapons and 432 delivery systems alone, more than the U.S. wanted to put at sea. Instead, the U.S. Navy chose to fill four silos per submarine with concrete, limiting the number each ship could carry to 20, and reducing the number of W-76-1 nuclear warheads on each missile. The real number is classified, but is believed to be 4–5 per Trident II D-5.
The Navy no longer needed all 18 Ohio-class submarines, so it converted four of the boats—Ohio, Michigan, Florida, and Georgia—into guided-missile submarines (SSGNs). The Trident missiles were removed, and 22 silos were converted to each carry seven Tomahawk land-attack cruise missiles. Each sub could carry a whopping 154 cruise missiles, giving just one SSGN more firepower than an aircraft carrier can generate over the course of an entire day. In 2011, USS Florida carried out strikes in support of Operation Odyssey Dawn, the NATO intervention in Libya.
The Takeaway
The Ohio-class submarines have proven a remarkable success—capable, reliable boats that have safeguarded nuclear weapons for decades. There has not been a single major incident involving the submarines or their deadly cargoes, a testament to their design and the skill and careful nature of their crews.
The U.S. Navy plans to replace the 14 nuclear-armed boats with 12 Columbia-class submarines, with the first ship, District of Columbia, conducting its first patrol in 2031.
Animations courtesy Md Zohaib
Kyle Mizokami is a writer on defense and security issues and has been at Popular Mechanics since 2015. If it involves explosions or projectiles, he's generally in favor of it. Kyle’s articles have appeared at The Daily Beast, U.S. Naval Institute News, The Diplomat, Foreign Policy, Combat Aircraft Monthly, VICE News, and others. He lives in San Francisco.
