The U.S. Navy planned to retire its four SSGNs (cruise missile firing nuclear submarine) by 2028. In March 2011 one of these SSGNs was used in combat for the first time, firing 93 of its 160 cruise missiles at Libyan targets. At the time those four SSGNs were designated for retirement by 2026, a date that as eventually extended. The navy had a plan for replacements, even though there was very little money for new ship types. To deal with that the navy sought to build some modified Virginia SSNs (nuclear attack subs) by adding a 30-meter (94 foot) section to the hull, which would contain 26 cruise missiles. Virginias already carry 16 of these, but the SSGN models would have a more respectable 40-42. Fifteen stretched Virginias would carry the same number of cruise missiles but spread among more ships. A Virginia SSGN would cost about 25 percent ($500 million) more than a Virginia SSN.
The older SSGNs made an impressive combat debut in 2011 when most of the a hundred or more Tomahawk cruise missiles launched in one day came from the SSGN Florida. These missiles hit targets in the North African nation of Libya. While this was the first time an SSGN saw combat, it was not the first-time nuclear subs fired missiles in a combat situation. American SSNs have fired Tomahawks several times.
The USS Florida was one of four Ohio class ballistic missile submarines (SSBN) converted to cruise missile submarines (SSGN). The USS Florida and the other three SSGNs entered service over the last five years. Each of these Ohio class SSGNs carry 154 Tomahawk cruise missiles, along with space for 66 commandos, usually Navy SEALs, and their equipment.
The idea of converting ballistic missile subs to SSGNs, rather than scraping them to fulfill disarmament agreements, has been bouncing around since the 1990s. After September 11, 2001, the idea got some traction. The navy submariners backed this proposal, because all American nuclear subs they lost a lot of their reason for being with the end of the Cold War. The United States had built a powerful nuclear submarine force during the Cold War, but with the rapid disappearance of the Soviet navy in the 1990s, there was little reason to keep over a hundred nuclear subs in commission. These boats are expensive, costing over a billion each to build and over a million dollars a week to operate. The four Ohio class SSBN being converted each had at least twenty years of useful life left in them.
The idea of a sub, armed with 154 highly accurate cruise missiles, and capable of rapidly traveling under water, ignoring weather, and avoiding observation at a speed of over 1,200 kilometers a day, to a far-off hot spot, had great appeal in the post-Cold War world. The ability to carry a large force of commandos as well was also attractive. In one sub you have your choice of hammer or scalpel. More capable cruise missiles are in the works as well. Whether or not this multi-billion-dollar investment will pay off remains to be seen, but it certainly worked off Libya in 2011
And then there’s the new Tomahawk. The RGM-109E Block IV Surface Ship Vertical Launched Tomahawk Land Attack Missile weighs 1.2 ton, is six meters (18 feet) long, has a range of 1,600 kilometers, getting there at a speed of 600-900 kilometers an hour, flying at an altitude of 17-32 meters (50-100 feet) and propelled by a jet engine generating only 600 pounds of thrust. Accuracy is on a par with JDAM (10 meters/ 31 feet). The Block IV Tomahawk can be reprogrammed in flight to hit another target and carries a vidcam to allow a missile to check on prospective targets.