The SSBN(X): The US Navy’s Next-Generation Ballistic Missile Submarine

The U.S. Navy currently operates a fleet of 14 Ohio-class nuclear-powered ballistic missile submarines (SSBN) as part of the United States’ nuclear triad. Each Ohio-class SSBN is armed with up to 24 Trident II D-5 submarine-launched ballistic missiles equipped with multiple independently targetable reentry vehicles.

Built by General Dynamics’ Electric Boat Division, the first Ohio-class submarine entered service in 1981 with the last boat commissioned in 1997. Beginning in 2027, roughly one submarine per year will be decommissioned – the U.S. Navy’s sole SSBN class will finally reach the end of its service life in 2040 when the last boat will be retired.

As a result, the U.S. Navy has initiated an Ohio-class SSBN replacement program to guarantee the existence of an adequate sea-based strategic nuclear force in the future. Starting in 2007, the Pentagon began to look for its next generation of submarines.

In 2010, the Defense Acquisition Board – the U.S. Department of Defense’s senior advisory board for defense procurements – endorsed “replacing the current 14 Ohio-class Ballistic Missile Submarines (SSBNs) as they reach the end of their service life with 12 Ohio Replacement Submarines, each comprising 16, 87-inch diameter missile tubes utilizing TRIDENT II D5 Life Extended missiles.”

With initial design and prototyping phases complete, the first Ohio Replacement Submarine (aka SSBN(X)) is slated to begin construction in 2021 and enter service in 2031. Overall, the U.S. Navy plans to acquire a total fleet of 12 SSBN(X)s with the last boat entering service sometime between 2040 and 2042.

However, given repeated delays in starting the program (including a two year-delay caused by the Budget Control Act of 2011) it seems much more likely that just ten new SSBNs will be constructed during the 2029-2042 period. There is also the question of financing the new fleet of boomers, which is estimated to cost between $4.9 and $5.36 billion per boat and around $110 million to operate per year.

According to the United States Naval Institute, the new submarine will displace 20,810 tons when submerged – the largest submarine the U.S. Navy has ever constructed – measure 561 feet (171 meters) in length, and have a beam of 43 feet (13 meters). This will make it only marginally larger than the Ohio-class at a displacement of 18,750 tons submerged, 560 feet (170 meters) in length, and a beam of 42 feet (13 meters). With a complement of 155, the crew size will also be roughly the same on both ships.

The new boat will be designed for a 42-year service life and is expected to serve through 2085. As a result, the new submarine will have to be equipped with sensors upgradeable at low cost, given the expected rapid technological advances that will occur during that timeframe.

In comparison to the Ohio-class, maintenance of the new vessel will be easier in at least one aspect, largely due to a new-design reactor using 90 percent enriched uranium.

“Unlike the Ohio-class design, which requires a mid-life nuclear refueling, the SSBN(X) is to be equipped with a life-of-the-ship nuclear fuel core (a nuclear fuel core that is sufficient to power the ship for its entire expected service life). Although the SSBN(X) will not need a mid-life nuclear refueling, it will still need a mid-life non-refueling overhaul (i.e., an overhaul that does not include a nuclear refueling) to operate over its full 40-year life,” according to a report by the Congressional Research Service.

Furthermore, the ship will be equipped with a much quieter electric-drive system rather than the mechanical-drive propulsion train used on other U.S. submarines, “which decouples the drive train from the turbines, and the pump-jet propulsor will use shrouded technology,” according to Defense Industry Daily. The ship will also use existing technology already in use on the Virginia-class nuclear-powered fast attack submarines, including special echo-reducing coatings and many other innovations.

The submarine-launched ballistic missile (SLBM) launch tubes will be the same size as those on the current Ohio-class, but the number of tubes will be reduced from 20 to 16. Both the SSBN(X) as well as the future Successor-class SSBNs of the United Kingdom’s Royal Navy will use the same missile compartment – the middle section of the submarine with the submarine-launched ballistic missile launch tubes. The SSBN(X) will initially be armed with the upgraded three-stage Trident D5LE (life-extension) submarine-launched ballistic missile, one of the most reliable long-range ballistic missiles in service today.

It is still unclear whether the new submarine will be equipped with torpedo tubes or not. It is also not yet certain whether the SSBN(X) will be capable of carrying non-nuclear payloads in its missile tubes. For example, should the submarine be capable of launching Unmanned Aerial Vehicles (UAVs), Unmanned Underwater Vehicles (UUVs), or even Special Forces units?

Indeed, as a report by the Center for Strategic and Budgetary Assessments (CSBA) notes,  “Manned submarines will likely need to shift from being frontline tactical platforms like aircraft to being host and coordination platforms like aircraft carriers.” Whether this will apply to SSBNs or just multi-purpose submarines remains to be seen.