After more than a decade of uncertainly the United States has apparently decided on what will replace the fourteen Cold War vintage Ohio class SSBNs (nuclear subs armed with ballistic missiles). The new Columbia class SSBNs will be about the same length of the 15,500 ton Ohios but about 5 percent larger in diameter and displace 18,500 tons (on the surface). The Ohios were based on 1980s technology and, although upgraded over the years are showing their age. The Ohios entered service between 1981 and 1997. Originally there were to be 24 Ohios but only 18 were built. With the end of the Cold War in 1991 even fewer were needed and four were converted to SSGNs (carrying cruise missiles instead of SLBMs), a process that was completed in 2008. Originally built to last 30 years it was later realized that this service life could be extended to at least 42 years. That means the Ohios will begin reaching retirement age in 2023 and the entire class will be gone by the late 2030s. If no replacement class of SSBNs in built the SSBNs will be gone.
The SSBNs (or "boomers") are part of the nuclear deterrent, a capability that is more persuasion than actual application. Each SSBN 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. 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. As expensive as they are, the SSBNs are still the least vulnerable to getting destroyed before they can be used and every nation that has them during the Cold War has built or is planning to build replacements.
Meanwhile, the U.S. Navy, the largest in the world since the early 1940s, 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 keeping the development costs as low as possible. This is made more difficult by the cost and quality control problems with shipbuilding the navy has been having for the last few decades. The navy leadership has been trying to deal with these problems but given all the political complications (that protects inefficiency and complicates ship design and construction) that has been difficult.
Nevertheless on paper the Columbias should be less expensive to operate and offer more comfortable accommodations for the crews. This will be done by incorporating much of the technology found in the new Virginia class SSNs and the cost of developing and building the twelve Columbias will be about $128 billion. About half of that is for development and the rest (about $6 billion each) for building the new SSBN. Construction is supposed to start in the early 2020s.
There are some major differences. While the Ohios carried 24 Trident SLBMs (Submarine Launched Ballistic Missiles, the new Columbias will each carry 16 Tridents with room available to accommodate a larger missile in the future. Both SSBNS have accommodations for 155 personnel but while all of those on the Ohios were crew the operating crew for the Columbias will be smaller with the empty bunks available for specialists (technical, special operations or whatever).
The SSBN admirals point out that cheap isn't always cheap in the end. Thus one of the major new technologies for Colombia is a nuclear reactor that will last the full life (40 years) of boat. 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 plus a long list of upgrades. All this cost $3.1 billion. The nuclear refueling accounts for 16 percent of that.
Submarines, because they are smaller, have required refueling every 5-20 years. The latest SSNs (Seawolf and Virginia) use 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 also 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 Columbia will 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. These were 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 their first fifty years U.S. SSBNs have made nearly 4,000 deployments (gone to sea for 11-12 weeks at a time). By 2009 the Ohios completed their 1,000th deployment. After the late 1990s the number of deployments each year declined by about half in large part because the need (potential for nuclear war) greatly decreased.
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 14 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.) The fourteen Ohio SSBNs carry half the United States' nuclear warheads.