Report to U.S. Congress on Navy Next-Generation Attack Submarine (SSN[X]) Program

USS North Dakota (SSN-784)
USS North Dakota (SSN-784)

The Congressional Research Service report for “Navy Next-Generation Attack Submarine (SSN[X]) Program:Background and Issues for Congress” published on May 10, 2021.

Introduction and Issue for Congress

The U.S. Navy wants to begin procuring a new class of nuclear-powered attack submarine (SSN), called the Next-Generation Attack Submarine or SSN(X), in FY2031. The SSN(X) would be the successor to the Virginia-class SSN design, which the U.S. Navy has been procuring since FY1998.

Congress approved $1 million in initial research and development funding for the SSN(X) program in FY2021. An issue for Congress for FY2022 and subsequent years is whether to approve, reject, or modify the U.S. Navy’s funding requests and acquisition strategy for the SSN(X) program.

Congress’s decisions on this issue could affect U.S. Navy capabilities and funding requirements and the U.S. shipbuilding industrial base.

Submarines in the U.S. Navy

The U.S. Navy operates three types of submarines—nuclear-powered ballistic missile submarines (SSBNs), nuclear-powered cruise missile and special operations forces (SOF) submarines (SSGNs), and nuclear-powered attack submarines (SSNs). The SSNs are general-purpose submarines that can perform a variety of peacetime and wartime missions.

Virginia-Class Program

Since FY2011, Virginia-class SSNs have been procured at a rate of two boats per year, and a total of 34 have been procured through FY2021. Most Virginia-class boats procured in FY2019 and subsequent years are to be built with the Virginia Payload Module (VPM), an additional, 84-foot-long, mid-body section equipped with four large-diameter, vertical launch tubes for storing and launching Tomahawk cruise missiles or other payloads. When procured at a rate of two boats per year, VPM equipped Virginia-class SSNs have an estimated procurement cost of about $3.4 billion per boat.

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Submarine With Virginia Payload Module (Vpm)

Submarine Construction Industrial Base

U.S. Navy submarines are built by General Dynamics’ Electric Boat Division (GD/EB) of Groton, CT, and Quonset Point, RI, and Huntington Ingalls Industries’ Newport News Shipbuilding (HII/NNS), of Newport News, VA. These are the only two shipyards in the country capable of building nuclear-powered ships. GD/EB builds submarines only, while HII/NNS also builds nuclear-powered aircraft carriers and is capable of building other types of surface ships.

In addition to GD/EB and HII/NNS, the submarine construction industrial base includes hundreds of supplier firms, as well as laboratories and research facilities, in numerous states. Much of the material procured from supplier firms for the construction of submarines comes from sole-source suppliers. For nuclear-propulsion component suppliers, an additional source of work is the
Navy’s nuclear-powered aircraft carrier construction program.

SSN(X) Program Program Designation

In the designation SSN(X), the “X” means that the exact design of the boat has not yet been determined.

Procurement Schedule

Under the Navy’s FY2020 30-year (FY2020-FY2049) shipbuilding plan, the first SSN(X) would be procured in FY2031, along with a single Virginia-class boat. In FY2032 and FY2033, the final four Virginia-class boats would be procured, at a rate of two per year. Procurement of follow-on SSN(X)s, at a rate of two per year, would then begin in FY2034. The 30-year plan’s sustained procurement rate of two SSNs per year would achieve a force of 66 SSNs—the Navy’s current SSN force-level goal—in FY2048.

A subsequent 30-year Navy shipbuilding document that the Trump Administration released on December 9, 2020—a document that can be viewed as the Trump Administration’s final published vision for future Navy force structure and/or a draft version of the FY2022 30-year shipbuilding plan—proposed a new SSN force-level goal of 72 to 78 boats. To meet this goal by the latter 2040s, it
projected an SSN procurement rate of three boats per year during the period FY2035-FY2041, and two and two-thirds
boats per year (in annual quantities of 2-3-3) during the period FY2042-FY2050.

Design of the SSN(X)

The U.S. Navy states that the SSN(X) will be designed to counter the emerging threat posed by near peer adversary competition for undersea supremacy. Unlike the VIRGINIA Class Submarine, which was designed for multi-mission dominance in the littoral, SSN(X) will be designed for greater transit speed under increased stealth conditions in all ocean environments, and carry a
larger inventory of weapons and diverse payloads.

While SSN(X) will be designed to retain multi-mission capability and sustained combat presence in denied waters, renewed priority of the anti-submarine warfare (ASW) mission against sophisticated threats in greater numbers will influence the design trade space. SSN(X) will be required to defend against threat UUVs [unmanned underwater vehicles], and coordinate with a larger contingent of off-hull vehicles, sensors, and friendly forces.

The Navy is examining three broad design options for the SSN(X)—a design based on the Virginia-class SSN design, a design based on the Columbia-class SSBN design, and a brand new design. An industry official stated that the SSN(X) might have a beam (i.e., hull diameter) greater than that of the Virginia-class design (34 feet), and closer to that of the Navy’s Seawolf-class SSN design and Columbia-class SSBN design (40 and 43 feet, respectively).

Potential Procurement Cost

Based on the Navy’s desired capabilities for the SSN(X), the Navy and the Congressional Budget Office (CBO) expect the SSN(X) to be substantially more expensive to procure than the Virginia-class design. An April 2021 CBO report on the December 9, 2020, 30-year Navy shipbuilding document states that in constant FY2021 dollars, the SSN(X)’s average unit procurement cost is estimated at $5.8 billion by the Navy and $6.2 billion by CBO.


Funding for the SSN(X) program is currently provided in the Navy’s research and development account, and specifically in Project 2368 (SSN[X] Class Submarine Development), which is the only project within Program Element (PE) 0604850N (SSN[X]). In the Navy’s FY2021 budget, PE 0604850N was line 150 in the Navy’s research and development account. For FY2021, the Navy requested $1 million for PE 0604850N. Congress, as part of its action on the Navy’s proposed FY2021 budget, approved this

Navy research and development funding in FY2020 and prior years has supported studies and technology development efforts that can be applied to future submarines, including the SSN(X). If the SSN(X) program follows the pattern of previous Navy submarine acquisition programs, the SSN(X) program’s annual research and development funding requests in coming years would increase to tens of millions of dollars per year, and eventually to hundreds ofmillions of dollars per year. In addition to funding in PE 0604850N, funding for developing the SSN(X)’s reactor plant might be provided through PE 0603570N (Advanced Nuclear Power Systems), the PE that has been used in the past for funding the development of reactor plants for other Navy nuclear-powered ships.

Issues for Congress

Issues for Congress include the following:

  • whether the Navy has accurately identified the SSN(X)’s required capabilities and accurately analyzed and incorporated the impact that various required capabilities can have on the SSN(X)’s procurement cost and life-cycle operation and support (O&S) cost;
  • the potential impact of the SSN(X) program—given the design’s currently estimated unit procurement cost and potential future Navy funding levels—on funding that will be available for other Navy program priorities; and
  • whether each SSN(X) should be built jointly by GD/EB and HII/NNS (the approach that has been used for building Virginia-class SSNs and,in modified form, is to be used for building Columbia-class SSBNs), or whether individual SSN(X)s should instead be
    completely built within a given shipyard (the separate yard approach used for building earlier Navy SSNs and SSBNs).

Regarding the final issue above, the Navy and Congress chose the joint-production strategy for the Virginia-class program as a means of preserving two U.S. submarine construction shipyards during an expected period of relatively low annual submarine procurement rates. For the SSN(X) program, factors to consider include the expected future submarine procurement rate; the impact that shifting back to separate-yard production might have on the Navy’s ability to use competition in awarding SSN(X) construction contracts; and the feasibility and cost of shifting back to separate-yard production after more than 20 years of joint

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