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Updated December 20, 2023
Navy Next-Generation Attack Submarine (SSN[X]) Program:
Background and Issues for Congress
Introduction
SSN(X) Program
The Navy wants to begin procuring a new class of nuclear-
powered attack submarine (SSN), called the Next-
Program Designation
Generation Attack Submarine or SSN(X), in FY2035. The
In the designation SSN(X), the “X” means that the exact
SSN(X) would be the successor to the Virginia-class SSN
design of the boat has not yet been determined.
design, which the Navy has been procuring since FY1998.
The Navy’s proposed FY2024 budget requests $544.7
Procurement Schedule
million in research and development funding for the
The Navy wants to procure the first SSN(X) in FY2035 and
SSN(X) program.
have it be delivered to the Navy in FY2042.
Submarines in the U.S. Navy
Figure 1. Virginia-Class Attack Submarine (SSN)
The U.S. Navy operates 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
As mentioned above, the Navy has been procuring
Virginia-class SSNs (Figure 1) since FY1998. Since
FY2011, the Navy has been procuring them at a rate of two
boats per year. When procured at a rate of two boats per
year, Virginia-class SSNs equipped with the Virginia
Payload Module (VPM) have a current estimated
Source: Cropped version of photograph accompanying Dan Ward,
procurement cost of about $4.3 billion per boat. (Most
“Opinion: How Budget Pressure Prompted the Success of Virginia-
Virginia-class boats procured in FY2019 and subsequent
Class Submarine Program,” USNI News, November 3, 2014. The
years are to be built with the VPM, an additional mid-body
caption states that it shows USS Minnesota (SSN-783) under
section equipped with four large-diameter, vertical launch
construction in 2012, and credits the photograph to the U.S. Navy.
tubes.) For additional information on Navy submarine
programs, see CRS Report RL32418, Navy Virginia (SSN-
Design of the SSN(X)
774) Class Attack Submarine Procurement: Background
The Navy states that the SSN(X)
and Issues for Congress, by Ronald O'Rourke, and CRS
will be designed to counter the growing threat posed
Report R41129, Navy Columbia (SSBN-826) Class Ballistic
by near peer adversary competition for undersea
Missile Submarine Program: Background and Issues for
supremacy. It will provide greater speed, increased
Congress, by Ronald O'Rourke.
horizontal payload capacity, improved acoustic
Submarine Construction Industrial Base
superiority and non-acoustic signatures, and higher
U.S. Navy submarines are built by General Dynamics’
operational availability. SSN(X) will conduct full
Electric Boat Division (GD/EB) of Groton, CT, and
spectrum undersea warfare and be able to
Quonset Point, RI, and Huntington Ingalls Industries’
coordinate with a larger contingent of off-hull
Newport News Shipbuilding (HII/NNS), of Newport News,
vehicles, sensors, and friendly forces. It will retain
VA. These are the only two shipyards in the country
and
improve
multi-mission
(Anti-submarine
capable of building nuclear-powered ships. GD/EB builds
warfare (ASW), Anti-surface warfare (ASuW),
submarines only, while HII/NNS also builds nuclear-
Strike, Special Operating Forces (SOF), Mine,
powered aircraft carriers. The submarine construction
Subsea Seabed Warfare (SSW), Intelligence,
industrial base also includes hundreds of supplier firms, as
Surveillance and Reconnaissance (ISR)) capability
well as laboratories and research facilities, in numerous
and sustained combat presence in denied waters.
states. Much of the material procured from supplier firms
for building submarines comes from sole-source suppliers.
(Budget-justification book for FY2024 Research,
Development, Test, and Evaluation, Navy account,
Vol. 3 [Budget Activity 5], p. 1293.)
https://crsreports.congress.gov
Navy Next-Generation Attack Submarine (SSN[X]) Program: Background and Issues for Congress
Navy officials have stated that the Navy wants the SSN(X)
for using LEU for the SSN(X) that was provided by the
to incorporate the speed and payload of the Navy’s fast and
Navy to CRS in unclassified form stated
heavily armed Seawolf (SSN-21) class SSN design, the
It is not practical to substitute LEU into existing
acoustic quietness and sensors of the Virginia-class design,
and the operational availability and service life of the
naval fuel systems or to design a VIRGINIA Class
Columbia-class design. These requirements will likely
Submarine (VCS) replacement [i.e., the SSN(X)]
result in an SSN(X) design that is larger than the original
around an unproven advanced LEU fuel concept.
Virginia-class design, which has a submerged displacement
Developing a newly designed submarine capable of
of about 7,800 tons, and possibly larger than the original
later acceptance of an LEU reactor core would also
SSN-21 design, which has a submerged displacement of
involve insertion of substantial margin (e.g.,
9,138 tons. Due to technological changes over the years for
increased hull size) that would be difficult to
improved quieting and other purposes, the designs of U.S.
estimate accurately at present and costly to
Navy submarines with similar payloads have generally been
implement. If future United States policy requires a
growing in displacement from one generation to the next.
shift to LEU, at least 15 years of advanced fuel
development and significant investment would be
Potential Procurement Cost
required. This development timeline makes it
An October 2023 Congressional Budget Office (CBO)
impractical to design a lead ship VCS replacement
report on the Navy’s FY2024 30-year shipbuilding plan
with an LEU reactor while meeting the Navy’s
states that in constant FY2023 dollars, the SSN(X)’s
schedule.
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
FY2024 Funding Request and
CBO. CBO’s estimate is about 14% to 15% higher than the
Congressional Action
Navy’s estimate. The CBO report states that CBO’s
The Navy’s proposed FY2024 budget requests $544.7
estimate assumes that the SSN(X) design would have a
million in research and development funding for the
submerged displacement of about 10,100 tons, about 11%
SSN(X) program, including $361.6 million in Project 2368
more than that of the SSN-21 design.
(SSN[X] Class Submarine Development) within Program
Issues for Congress
Element (PE) 0604850N (SSN[X]), which is line 154 in the
Navy’s FY2024 research and development account, and
Issues for Congress include the following:
$183.1 million in Project 2370 (Next Generation Fast
• whether the Navy has accurately identified the
Attack Nuclear Propulsion Development) within PE
SSN(X)’s required capabilities and accurately analyzed
0603570N (Advanced Nuclear Power Systems), which is
the impact that various required capabilities can have on
line 47.
the SSN(X)’s cost;
The conference report (H.Rept. 118-301 of December 6,
• the potential impact of the SSN(X) program on funding
2023) on the FY2024 National Defense Authorization Act
that will be available for other Navy program priorities,
(NDAA) (H.R. 2670), recommended approving the Navy’s
particularly if CBO’s estimate of the SSN(X)’s
funding request for line 47 and reducing by $39.754 million
procurement cost is more accurate than the Navy’s
the Navy’s funding request for line 154 for “Unjustified
estimate;
growth—management and support costs” ($7.95 million),
•
“
whether it would be technically feasible for the SSN(X)
Unjustified growth—NSWC [Naval Surface Warfare
to be powered by a reactor plant using low-enriched
Center] studies” ($13.804 million), and “Unjustified
uranium (LEU), rather than the highly enriched uranium
growth—shipbuilder studies” ($18.0 million). Section 3124
(HEU) used on other Navy nuclear-powered ships, and
of H.R. 2670 prohibits funds from being used for research
if so, what impact that would have on nuclear arms
or development relating to an advanced naval nuclear fuel
control and nonproliferation efforts and SSN(X) costs
system based on LEU.
and capabilities; and
The House Appropriations Committee, in its report on the
• whether each SSN(X) should be built jointly by GD/EB
FY2024 DOD Appropriations Act (H.R. 4365),
and HII/NNS (the approach used for building Virginia-
recommended approving the request for line 47 and
class SSNs and, in modified form, for building
reducing the request for line 154 by $82.35 million. The
Columbia-class SSBNs), or whether individual SSN(X)s
Senate Appropriations Committee, in its report on the
should instead be completely built within a given
FY2024 DOD Appropriations Act (S. 2587), recommended
shipyard (the separate-yard approach used for building
reducing the request for line 47 by $27.0 million and
earlier Navy SSNs and SSBNs).
reducing the request for line 154 by $39.754 million.
Regarding the third issue above, a January 2020
Department of Energy (DOE) National Nuclear Security
Ronald O'Rourke, Specialist in Naval Affairs
Administration (NNSA) report to Congress on the potential
IF11826
https://crsreports.congress.gov
Navy Next-Generation Attack Submarine (SSN[X]) Program: Background and Issues for Congress
Disclaimer
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congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
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