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Updated July 10, 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 FY2040 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 (Pillar 1) Project: Background and
delay of SSN(X) construction start from the mid-2030s to
Issues for Congress, by Ronald O'Rourke, and CRS Report
the early 2040s presents a significant challenge to the
R41129, Navy Columbia (SSBN-826) Class Ballistic
submarine design industrial base associated with the
Missile Submarine Program: Background and Issues for
extended gap between the Columbia class and SSN(X)
Congress, 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
to FY2040] does not change the Navy’s position of
9,138 tons. Due to technological changes over the years for
not pursuing LEU fuel. Naval fuel system testing
improved quieting and other purposes, the designs of U.S.
and evaluation would need to be funded and
Navy submarines with similar payloads have generally been
performed. Prior estimates have been 10-15 years
growing in displacement from one generation to the next.
and $1B to complete enough work to determine
whether a fuel system may be viable and what
Potential Procurement Cost
performance may be achieved. Success is not
An October 2023 Congressional Budget Office (CBO)
assured. An optimistic estimate of total time to
report on the Navy’s FY2024 30-year shipbuilding plan
develop and deploy a naval LEU fuel system is 20-
states that in constant FY2023 dollars, the SSN(X)’s
30 years (which includes the 10-15 years initial
average unit procurement cost is estimated at $6.7 billion to
development program) and $25B. This does not
$7.0 billion by the Navy and $7.7 billion to $8.0 billion by
include the cost of additional force structure to
CBO. CBO’s estimate is about 14% to 15% higher than the
Navy’s estimate. The CBO report states that CBO’s
cover mission of submarines being refueled.
estimate assumes that the SSN(X) design would have a
The U.S. Navy has developed and improved
submerged displacement of about 10,100 tons, about 11%
technology using highly enriched uranium (HEU)
more than that of the SSN-21 design.
fuel over the past 75 years, providing the U.S. Navy
Issues for Congress
with unmatched asymmetric advantages in naval
warfare. U.S. Navy warships requirements
Issues for Congress include the following:
determine naval fuel system design features,
• whether the Navy has accurately identified the
including the use of HEU fuel. An LEU fuel system
SSN(X)’s required capabilities and accurately analyzed
would not provide any military benefit to the
the impact that various required capabilities can have on
performance of U.S. naval reactors. It would
the SSN(X)’s cost;
decrease the available energy in the propulsion
•
plant, negatively affect reactor endurance, reactor
the potential impact of the SSN(X) program on funding
that will be available for other Navy program priorities,
size, ship costs, force structure, and maintenance
particularly if CBO’s estimate of the SSN(X)’s
infrastructure.
procurement cost is more accurate than the Navy’s
Funding Request
estimate;
The Navy’s proposed FY2025 budget requests $586.9
• the potential impact of deferring procurement of the first million in research and development funding for the
SSN(X) from FY2035 to FY2040 on the U.S. ability in
SSN(X) program, which is $208.0 million less than the
the 2040s and beyond to maintain superiority in
$794.9 million in research and development funding that
undersea warfare and fulfill U.S. Navy missions;
was programmed for FY2025 under the Navy’s FY2024
• the details and adequacy of the Navy’s plan for
budget submission. The request for $586.9 million includes
$348.8 million in Project 2368 (SSN[X] Class Submarine
managing the impact on the submarine design industrial
Development) within Program Element (PE) 0604850N
base of deferring procurement of the first SSN(X) from
(SSN[X]), which is line 155 in the Navy’s FY2025 research
FY2035 to FY2040;
and development account, and $238.1 million in Project
• whether it would be technically feasible for the SSN(X)
2370 (Next Generation Fast Attack Nuclear Propulsion
to be powered by a reactor plant using low-enriched
Development) within PE 0603570N (Advanced Nuclear
uranium (LEU), rather than the highly enriched uranium
Power Systems), which is line 47.
(HEU) used on other Navy nuclear-powered ships,
particularly if procurement of the first SSN(X) is
The House Armed Services Committee, in its report
deferred from FY2035 to FY2040, and if so, what
(H.Rept. 118-529 of May 31, 2024) on the FY2025
impact that would have on nuclear arms control and
National Defense Authorization Act (H.R. 8070),
nonproliferation efforts and SSN(X) costs and
recommends reducing the funding request for line 155 by
capabilities; and
$50.0 million for “Program delay” (page 467), and
•
approving the funding request for line 47 (page 463).
whether each SSN(X) should be built jointly by GD/EB
and HII/NNS (the approach used for building Virginia-
The House Appropriations Committee, in its report
class SSNs and, in modified form, for building
(H.Rept. 118-557 of June 17, 2024) on the FY2025 DOD
Columbia-class SSBNs), or whether individual SSN(X)s
Appropriations Act (H.R. 8774), recommends approving
should instead be completely built within a given
the funding request for line 155 (page 191) and reducing the
shipyard (the separate-yard approach used for building
funding request for line 47 by $41.0 million for “Project
earlier Navy SSNs and SSBNs).
2370 excess to need” (page 186).
Regarding the fifth issue above, a May 17, 2024, Navy
information paper provided to CRS states that
Ronald O'Rourke, Specialist in Naval Affairs
The shift in expected delivery of SSN(X) [due to the
IF11826
deferral of the lead ship procurement from FY2035
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Navy Next-Generation Attack Submarine (SSN[X]) Program: Background and Issues for Congress
Disclaimer
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https://crsreports.congress.gov | IF11826 · VERSION 30 · UPDATED