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Updated March 21, 2024
Navy Next-Generation Attack Submarine (SSN[X]) Program:
Background and Issues for Congress
Introduction
Submarine Construction Industrial Base
The Navy has been procuring Virginia-class nuclear
U.S. Navy submarines are built by General Dynamics’
powered attack submarines (SSNs) since FY1998. The
Electric Boat Division (GD/EB) of Groton, CT, and
Navy’s envisaged successor to the Virginia-class design is
Quonset Point, RI, and Huntington Ingalls Industries’
the Next-Generation Attack Submarine, or SSN(X). The
Newport News Shipbuilding (HII/NNS), of Newport News,
Navy’s FY2024 budget submission envisaged procuring the
VA. These are the only two shipyards in the country
first SSN(X) in FY2035. The Navy’s FY2025 budget
capable of building nuclear-powered ships. GD/EB builds
submission defers the envisaged procurement of the first
submarines only, while HII/NNS also builds nuclear-
SSN(X) from FY2035 to 2040 due, the Navy states, to
powered aircraft carriers. The submarine construction
limitations on the Navy’s total budget.
industrial base also includes hundreds of supplier firms, as
well as laboratories and research facilities, in numerous
Submarines in the U.S. Navy
states. Much of the material procured from supplier firms
The U.S. Navy operates nuclear-powered ballistic missile
for building submarines comes from sole-source suppliers.
submarines (SSBNs), nuclear-powered cruise missile and
special operations forces (SOF) submarines (SSGNs), and
SSN(X) Program
nuclear-powered attack submarines (SSNs). The SSNs are
general-purpose submarines that can perform a variety of
Program Designation
peacetime and wartime missions.
In the designation SSN(X), the “X” means that the exact
design of the boat has not yet been determined.
Virginia-Class Program
When procured at a rate of two boats per year, Virginia-
Procurement Schedule
class SSNs (Figure 1) equipped with the Virginia Payload
The Navy’s FY2024 budget submission envisaged
Module (VPM) have a current estimated procurement cost
procuring the first SSN(X) in FY2035. The Navy’s FY2025
of more than $4.5 billion per boat. For additional
budget submission defers the envisaged procurement of the
information on Navy submarine programs, see CRS Report
first SSN(X) from FY2035 to FY2040. The Navy’s FY2025
RL32418, Navy Virginia-Class Submarine Program and
30-year (FY2035-FY2054) shipbuilding plan states: “The
AUKUS Submarine Proposal: Background and Issues for
delay of SSN(X) construction start from the mid-2030s to
Congress, by Ronald O'Rourke, and CRS Report R41129,
the early 2040s presents a significant challenge to the
Navy Columbia (SSBN-826) Class Ballistic Missile
submarine design industrial base associated with the
Submarine Program: Background and Issues for Congress,
extended gap between the Columbia class and SSN(X)
by Ronald O'Rourke.
design programs, which the Navy will manage.”
Figure 1. Virginia-Class Attack Submarine (SSN)
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)
Source: Cropped version of photograph accompanying Dan Ward,
to incorporate the speed and payload of the Navy’s fast and
“Opinion: How Budget Pressure Prompted the Success of Virginia-
heavily armed Seawolf (SSN-21) class SSN design, the
Class Submarine Program,” USNI News, November 3, 2014. The
acoustic quietness and sensors of the Virginia-class design,
caption states that it shows USS Minnesota (SSN-783) under
and the operational availability and service life of the
construction in 2012 and credits the photograph to the U.S. Navy.
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
https://crsreports.congress.gov
Navy Next-Generation Attack Submarine (SSN[X]) Program: Background and Issues for Congress
SSN-21 design, which has a submerged displacement of
for the SSN(X) that was provided by the Navy to CRS in
9,138 tons. Due to technological changes over the years for
unclassified form stated
improved quieting and other purposes, the designs of U.S.
It is not practical to substitute LEU into existing
Navy submarines with similar payloads have generally been
growing in displacement from one generation to the next.
naval fuel systems or to design a VIRGINIA Class
Submarine (VCS) replacement [i.e., the SSN(X)]
Potential Procurement Cost
around an unproven advanced LEU fuel concept.
An October 2023 Congressional Budget Office (CBO)
Developing a newly designed submarine capable of
report on the Navy’s FY2024 30-year shipbuilding plan
later acceptance of an LEU reactor core would also
states that in constant FY2023 dollars, the SSN(X)’s
involve insertion of substantial margin (e.g.,
average unit procurement cost is estimated at $6.7 billion to
increased hull size) that would be difficult to
$7.0 billion by the Navy and $7.7 billion to $8.0 billion by
estimate accurately at present and costly to
CBO. CBO’s estimate is about 14% to 15% higher than the
implement. If future United States policy requires a
Navy’s estimate. The CBO report states that CBO’s
shift to LEU, at least 15 years of advanced fuel
estimate assumes that the SSN(X) design would have a
development and significant investment would be
submerged displacement of about 10,100 tons, about 11%
required. This development timeline makes it
more than that of the SSN-21 design.
impractical to design a lead ship VCS replacement
with an LEU reactor while meeting the Navy’s
Issues for Congress
schedule.
Issues for Congress include the following:
•
Funding Request
whether the Navy has accurately identified the
SSN(X)’s required capabilities and accurately analyzed
the impact that various required capabilities can have on
FY2024
the SSN(X)’s cost;
The Navy’s proposed FY2024 budget requested $544.7
million in research and development funding for the
• the potential impact of the SSN(X) program on funding
SSN(X) program, including $361.6 million in Project 2368
that will be available for other Navy program priorities,
(SSN[X] Class Submarine Development) within Program
particularly if CBO’s estimate of the SSN(X)’s
Element (PE) 0604850N (SSN[X]), which is line 154 in the
procurement cost is more accurate than the Navy’s
Navy’s FY2024 research and development account, and
estimate;
$183.1 million in Project 2370 (Next Generation Fast
• the potential impact of deferring procurement of the first Attack Nuclear Propulsion Development) within PE
SSN(X) from FY2035 to FY2040 on the U.S. ability in
0603570N (Advanced Nuclear Power Systems), which is
the 2040s and beyond to maintain superiority in
line 47. The House Appropriations Committee, in its report
undersea warfare and fulfill U.S. Navy missions;
on the FY2024 DOD Appropriations Act (H.R. 4365),
recommended approving the request for line 47 and
• the details and adequacy of the Navy’s plan for
reducing the request for line 154 by $82.35 million. The
managing the impact on the submarine design industrial
Senate Appropriations Committee, in its report on the
base of deferring procurement of the first SSN(X) from
FY2024 DOD Appropriations Act (S. 2587), recommended
FY2035 to FY2040;
reducing the request for line 47 by $27.0 million and
•
reducing the request for line 154 by $39.754 million.
whether it would be technically feasible for the SSN(X)
to be powered by a reactor plant using low-enriched
FY2025
uranium (LEU), rather than the highly enriched uranium
The Navy’s proposed FY2025 budget requests $586.9
(HEU) used on other Navy nuclear-powered ships,
million in research and development funding for the
particularly if procurement of the first SSN(X) is
SSN(X) program, which is $208.0 million less than the
deferred from FY2035 to FY2040, and if so, what
$794.9 million in research and development funding that
impact that would have on nuclear arms control and
was programmed for FY2025 under the Navy’s FY2024
nonproliferation efforts and SSN(X) costs and
budget submission. The request for $586.9 million includes
capabilities; and
$348.8 million in Project 2368 (SSN[X] Class Submarine
• whether each SSN(X) should be built jointly by GD/EB
Development) within Program Element (PE) 0604850N
and HII/NNS (the approach used for building Virginia-
(SSN[X]), which is line 155 in the Navy’s FY2025 research
class SSNs and, in modified form, for building
and development account, and $238.1 million in Project
Columbia-class SSBNs), or whether individual SSN(X)s
2370 (Next Generation Fast Attack Nuclear Propulsion
should instead be completely built within a given
Development) within PE 0603570N (Advanced Nuclear
shipyard (the separate-yard approach used for building
Power Systems), which is line 47.
earlier Navy SSNs and SSBNs).
Regarding the fifth issue above, a January 2020 Department
Ronald O'Rourke, Specialist in Naval Affairs
of Energy (DOE) National Nuclear Security Administration
IF11826
(NNSA) report to Congress on the potential for using LEU
https://crsreports.congress.gov
Navy Next-Generation Attack Submarine (SSN[X]) Program: Background and Issues for Congress
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
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https://crsreports.congress.gov | IF11826 · VERSION 27 · UPDATED