There is unrest in the U.S. Navy over what the next class of SSBNs (nuclear subs armed with ballistic missiles) will be, the ones that will replace the current 15,000 ton Ohios. Based on 1980s technology, the Ohios have been upgraded over the years, but are showing their age. The replacement SSBN design will be quite different. But there is some debate in the navy over how the huge cost ($80 billion) of designing ($20 billion) and building ($5 billion each for 12 subs) the new boats will be handled. Including development costs, each new SSBN will cost $6.7 billion. The SSBNs are part of the nuclear deterrent, a capability that is more persuasion than actual application. Meanwhile, the navy needs new carriers, amphibious and surface warships, plus aircraft and munitions for regular use dealing with actual, not theoretical, problems. Thus the case for building fewer, cheaper and less capable SSBNs, and cutting the program cost in half.
The SSBN admirals point out that cheap isn't always cheap in the end. One of the major new technologies is a nuclear reactor that will last the full life (40 years) of the new boats. In the past, nuclear powered warships had to have their depleted nuclear fuel replaced after 20-30 years. That's expensive, and time consuming. For example, the U.S. Nimitz class carrier USS Carl Vinson (CVN 70) entered service in 1982, but 25 years later, had to undergo a three year refurbishment that included the refueling, and a long list of upgrades. This cost $3.1 billion. The nuclear refueling accounts for 16 percent of that. All this will keep the Vinson in service until 2032. Submarines, because they are smaller, have required refueling every 5-20 years. The latest SSN subs (Seawolf and Virginia) uses a new reactor design that eliminates the need for the elaborate (taking apart the reactors, and part of the ship) refueling process. The next American carrier, CVN 21, will use this new technology. But SSNs have a life of only 30 years, so a new reactor design will be required for the SSBNs, which serve 40 years. It costs a billion dollars to refuel a nuclear sub.
The new class of SSBNs also need to be quieter, to keep up with advances in submarine detection technology. That costs a lot, although much can be borrowed from the latest SSN class (the Virginias). Go cheap on this, and the SSBNs are less valuable as a deterrent (as they are easier to find and destroy just when they are needed.) Finally, there is the need to incorporate labor saving gear in the new SSBNs, so the crew size can be sharply (up to 50 percent) cut. It's getting harder and harder to recruit sailors for SSBN duty, and the only other way to solve that problem is with bonuses, on top of the $100,000 in annual pay and benefits, and several times that just to train SSBN sailors. Whichever way this goes (half a dozen cheap boats, or a dozen state-of-the art ones), there will be another class of American SSBNs.
The first American SSBNs were the five, 6,000 ton boats of the George Washington class. This was basically a SSN design that was enlarged to add the missile compartment (for 16 Polaris missiles.) The first of these entered service in 1960 and was soon joined by five of the 6,900 ton Ethan Allen class, which was designed from the start as an SSBN. These entered service in the early 1960s. Basically, this was an improved George Washington class. Next came nine, 7,200 ton Lafayette class boats, with the first entering service in 1963, and the last one decommissioned in 1994. The next two classes (James Madison and Benjamin Franklin) were similar, with incremental improvements. The last of these was decommissioned in 2002, after over 30 years of service, leaving just the Ohios. The incremental improvements were not trivial. The Benjamin Franklins had much quieter machinery, better electronics and enough room to handle the Trident 1 missile.
In the last half century years, U.S. SSBNs (nuclear powered ballistic missile submarine) have made nearly 4,000 deployments (gone to sea for 11-12 weeks at a time). Last year, the current class of U.S. SSBNs, the Ohios, completed their 1,000th deployment.
Each SSBN (or "boomer") has two crews, who alternate in taking the boat to sea. Thus the subs spend most of their time at sea, where they are nearly impossible to find and destroy. Thus the SSBNs provide the ultimate retaliatory weapon to dissuade any enemy from trying to launch a surprise nuclear attack, with the idea of wiping out land based missiles before they can be launched. Given what we know now of the effects, on the planetary environment, of a large scale use of nuclear weapons, such a "first strike" is highly unlikely. But the world has changed, and the threat of such an attack is much diminished since the end of the Cold War in 1991.
The U.S. now uses Trident II (D-5), three stage ballistic missiles, costing $47 million each. The nuclear warheads cost extra. The 58.5 ton Trident II equips the 18 Ohio class SSBNs. The missile has a range of 7,400 kilometers and is more accurate than the Trident I replaced. The Trident II can deliver up to five warheads. The missile entered service in 1990, while Ohio SSBN boats were still being built (the first one entered service in 1982, while the last one entered service in 1997). Each Ohio SSBN carries 24 missiles (120 warheads.) Eighteen Ohio class SSBNs were built, and fourteen are still in service, carrying half the United States' nuclear warheads. Another four were converted to carry cruise missiles and commandos.