The most important weapon system in the U.S. arsenal isn’t an aircraft carrier or a long-range bomber. It is the Trident ballistic-missile submarine, designated SSBN in naval nomenclature (“SS” for submarine, “B” for ballistic missile, “N” for nuclear propulsion). The Trident, also called the Ohio-class after the lead ship in the program, is the biggest submarine ever built for the U.S. Navy because it was designed to have 24 launch tubes containing long-range ballistic missiles — with each missile carrying up to eight independently-targetable nuclear warheads. A single Trident submarine thus is capable of destroying a medium-size country. What makes Tridents so important, though, isn’t just their fearsome firepower but the fact that once they are submerged and on station somewhere in the Atlantic or Pacific Ocean, they are impossible for enemies to find. They thus provide the backbone of the secure retaliatory force that is at the heart of nuclear deterrence.
It is a measure of how successful the Trident program has been that most Americans are barely aware the subs exist. There have been no major mishaps in the three decades the vessels have been at sea, and no adversary currently seems capable of targeting them when they are on station. But the 14 Tridents still executing the ballistic-missile mission (four were converted to non-nuclear roles during the Bush years) are getting old. The first boat in the class was commissioned in 1981, and the last in 1997. Preservation of a secure deterrent force requires that construction of new ballistic-missile subs commence not later than 2020, so that next-generation vessels can enter the fleet as the nuclear cores of existing boats are wearing out. The Navy plans to begin a six-year design cycle for the next-generation SSBN in 2012, leading to construction of a lead ship starting in 2019. But why develop a new sub if the existing submarines are so good? Why not just build more Tridents? Basically, there are three reasons for starting from scratch.
The first reason is that the next-generation SSBN must be even quieter than today’s Tridents, because it is likely to carry most of the U.S. nuclear force and therefore must have an assured capacity to withstand surprise attack. Advances in sensors, processors, software and networks since Trident first put to sea raise the possibility that a future adversary may find some way of tracking Tridents. With only a handful of ships in the class and some of those not at sea on any given day, it is essential that any “signatures” potentially usable by enemies for targeting be minimized. At the very least, the future boats must be as quiet as today’s Virginia-class attack subs, which are only half the size of a Trident. Virginias themselves lack the internal volume to host highly-capable ballistic missiles, and any effort to modify them for that purpose would increase acoustic and other signatures in a self-defeating manner, so a new boat must be designed to guarantee the survivability of the future deterrent.
A second reason why the new sub must be developed is so that it can have a “life-of-ship” nuclear core. The Tridents require costly and time-consuming mid-life replacements of nuclear fuel in the reactors that drive their propulsion systems. These refuelings remove the vessels from service for two years, and thus reduce the readiness of the fleet. Virginia-class attack subs have a nuclear core designed to last the full 30 years they are expected to be in service, but the planned lifetime of the next-generation SSBN is 40 years, so a different kind of reactor core must be developed. By developing a life-of-ship core for the Trident replacement, the Navy can reduce the number of boats in the deterrent force from the current 14 to 12, since it will not have to factor mid-life refuelings into the nuclear readiness posture. That should result in substantial savings across the lifetime of the program, because each new SSBN will cost at least $5 billion to build and mid-life refuelings have cost the Trident program about $250 million per boat.
The third reason a new SSBN is needed is because virtually every facet of on-board technology has changed since the U.S.S. Ohio was commissioned in 1981. Back then there were no fiber networks, no laptop computers, and no flat-panel displays. Processing power was expensive and people were relatively cheap. Today, processing power is dirt cheap and each nuclear sailor costs the Navy over $100,000 per year. Tridents have been continuously upgraded since their inception, but by completely redesigning the next generation of subs, crew-reducing automation features and vastly improved functionality can be introduced into every aspect of shipboard operations. Navy planners haven’t yet figured out how a program that costs $20 billion to design and develop and $60 billion to construct will fit into the service’s chronically tight shipbuilding budget, but they already are convinced that pursuing a new ballistic-missile sub makes more fiscal and operational sense than trying to modify a Cold War design.