Navy Next-Generation Attack Submarine (SSN[X]) Program: Background and Issues for Congress

https://crsreports.congress.gov

Updated July 23, 2024

Navy Next-Generation Attack Submarine (SSN[X]) Program: Background and Issues for Congress

Introduction

Submarines in the U.S. Navy

Virginia-Class Program

Figure 1. Virginia-Class Attack Submarine (SSN)

Source: Cropped version of photograph accompanying Dan Ward, “Opinion: How Budget Pressure Prompted the Success of Virginia- Class Submarine Program,” USNI News, November 3, 2014. The caption states that it shows USS Minnesota (SSN-783) under construction in 2012 and credits the photograph to the U.S. Navy.

Submarine Construction Industrial Base

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 The Navy’s FY2024 budget submission envisaged procuring the first SSN(X) in FY2035. The Navy’s FY2025 budget submission defers the envisaged procurement of the first SSN(X) from FY2035 to FY2040. The Navy’s FY2025 30-year (FY2035-FY2054) shipbuilding plan states: “The delay of SSN(X) construction start from the mid-2030s to the early 2040s presents a significant challenge to the submarine design industrial base associated with the extended gap between the Columbia class and SSN(X) design programs, which the Navy will manage.”

Design of the SSN(X) The Navy states that the SSN(X) “will be designed to counter the growing threat posed by near peer adversary competition for undersea supremacy. It will provide greater speed, increased horizontal [i.e., torpedo-room] payload capacity, improved acoustic superiority and non-acoustic signatures, and higher operational availability. SSN(X) will conduct full spectrum undersea warfare and be able to coordinate with a larger contingent of off-hull vehicles, sensors, and friendly forces.” (Budget-justification book for FY2025 Research, Development, Test, and Evaluation, Navy account, Vol. 3 [Budget Activity 5], p. 1299.)

Navy officials have stated that the Navy wants the SSN(X) to incorporate the speed and payload of the Navy’s fast and heavily armed Seawolf (SSN-21) class SSN design, the acoustic quietness and sensors of the Virginia-class design, and the operational availability and service life of the Columbia-class design. These requirements will likely result in an SSN(X) design that is larger than the original Virginia-class design, which has a submerged displacement of about 7,800 tons, and possibly larger than the original

Navy Next-Generation Attack Submarine (SSN[X]) Program: Background and Issues for Congress

https://crsreports.congress.gov

SSN-21 design, which has a submerged displacement of 9,138 tons. Due to technological changes over the years for improved quieting and other purposes, the designs of U.S. Navy submarines with similar payloads have generally been growing in displacement from one generation to the next.

Potential Procurement Cost An October 2023 Congressional Budget Office (CBO) report on the Navy’s FY2024 30-year shipbuilding plan states that in constant FY2023 dollars, the SSN(X)’s average unit procurement cost is estimated at $6.7 billion to $7.0 billion by the Navy and $7.7 billion to $8.0 billion by CBO. CBO’s estimate is about 14% to 15% higher than the Navy’s estimate. The CBO report states that CBO’s estimate assumes that the SSN(X) design would have a submerged displacement of about 10,100 tons, about 11% more than that of the SSN-21 design.

Issues for Congress

• whether the Navy has accurately identified the

SSN(X)’s required capabilities and accurately analyzed the impact that various required capabilities can have on the SSN(X)’s cost;

• the potential impact of the SSN(X) program on funding

that will be available for other Navy program priorities, particularly if CBO’s estimate of the SSN(X)’s procurement cost is more accurate than the Navy’s estimate;

• the potential impact of deferring procurement of the first

SSN(X) from FY2035 to FY2040 on the U.S. ability in the 2040s and beyond to maintain superiority in undersea warfare and fulfill U.S. Navy missions;

• the details and adequacy of the Navy’s plan for

managing the impact on the submarine design industrial base of deferring procurement of the first SSN(X) from FY2035 to FY2040;

• whether it would be technically feasible for the SSN(X)

to be powered by a reactor plant using low-enriched uranium (LEU), rather than the highly enriched uranium (HEU) used on other Navy nuclear-powered ships, particularly if procurement of the first SSN(X) is deferred from FY2035 to FY2040, and if so, what impact that would have on nuclear arms control and nonproliferation efforts and SSN(X) costs and capabilities; and

• whether each SSN(X) should be built jointly by GD/EB

and HII/NNS (the approach used for building Virginia- class SSNs and, in modified form, 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 fifth issue above, a May 17, 2024, Navy information paper provided to CRS states that

The shift in expected delivery of SSN(X) [due to the deferral of the lead ship procurement from FY2035 to FY2040] does not change the Navy’s position of not pursuing LEU fuel. Naval fuel system testing

and evaluation would need to be funded and performed. Prior estimates have been 10-15 years and $1B to complete enough work to determine whether a fuel system may be viable and what performance may be achieved. Success is not assured. An optimistic estimate of total time to develop and deploy a naval LEU fuel system is 20- 30 years (which includes the 10-15 years initial development program) and $25B. This does not include the cost of additional force structure to cover mission of submarines being refueled.

The U.S. Navy has developed and improved technology using highly enriched uranium (HEU) fuel over the past 75 years, providing the U.S. Navy with unmatched asymmetric advantages in naval warfare. U.S. Navy warships requirements

determine naval fuel system design features, including the use of HEU fuel. An LEU fuel system would not provide any military benefit to the performance of U.S. naval reactors. It would decrease the available energy in the propulsion plant, negatively affect reactor endurance, reactor size, ship costs, force structure, and maintenance infrastructure.

Funding Request

The House Armed Services Committee, in its report (H.Rept. 118-529 of May 31, 2024) on the FY2025 National Defense Authorization Act (H.R. 8070), recommended reducing the funding request for line 155 by $50.0 million for “Program delay” (page 467), and approving the funding request for line 47 (page 463). The Senate Armed Services Committee, in its report (S.Rept. 118-188 of July 8, 2024) on S. 4638, recommended approving the funding requests for lines 155 and 47 (pages 488 and 484). Section 3111 of S. 4638 would prohibit FY2025 funds authorized by S. 4638 to be used for research and development of an advanced naval nuclear fuel system based on LEU until certain determinations are provided. The House Appropriations Committee, in its report (H.Rept. 118-557 of June 17, 2024) on the FY2025 DOD Appropriations Act (H.R. 8774), recommended approving the funding request for line 155 (page 191) and reducing the funding request for line 47 by $41.0 million for “Project 2370 excess to need” (page 186).

Ronald O'Rourke, Specialist in Naval Affairs

IF11826