Navy Columbia (SSBN-826) Class Ballistic Missile Submarine Program: Background and Issues for Congress

Updated September 25, 2025 (R41129)
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Contents

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Tables

Appendixes

Summary

The Navy's Columbia (SSBN-826) class ballistic missile submarine (SSBN) aims to design and build a class of 12 new SSBNs to replace the Navy's current force of 14 aging Ohio-class SSBNs. Since 2013, the Navy has consistently identified the Columbia-class program as the Navy's top priority program. The Navy procured the first Columbia-class boat in FY2021 and the second in FY2024. The Navy wants to procure the third boat in FY2026.

The first and second Columbia-class boats were funded with incremental funding, a funding approach in which the procurement cost of each boat is divided into multiple annual increments, with the first increment occurring in the year in which the boat was procured. The first Columbia-class boat was funded with three-year incremental funding in FY2021-FY2023, and the second boat was funded with two-year incremental funding (also called split funding) in FY2024-FY2025. The Navy wants to use three-year incremental funding for procuring the third and subsequent boats in the program.

The procurement dates of the first, second and third Columbia-class boats were spaced years apart from one another to provide time for fixing any design issues that might be discovered in building the first boat before construction proceeds on subsequent boats, and to help ease the submarine construction industrial base into the situation of building Columbia-class submarines while continuing to build Virginia-class attack submarines. During the period FY2021-FY2025, the Columbia-class procurement rate was 0.4 boats per year (i.e., the first two boats were procured during that five-year period).

Starting with the third boat in FY2026, the Navy wants to shift Columbia-class procurement to a higher rate of one boat per year, so that the final 10 ships in the program (i.e., boats 3 through 12) would be procured over the 10-year period FY2026-FY2035. To reduce Columbia-class procurement costs and mitigate risks from shifting Columbia-class procurement to the higher rate of one boat per year, the Navy wants to use a block buy contract to procure the five Columbia-class boats that are scheduled to be procured in FY2026-FY2030 (i.e., boats 3 through 7).

The Navy's FY2026 budget submission requests

  • the procurement of the third boat in the class;
  • authority to use three-year incremental funding for procuring each of the remaining 10 boats in the program (i.e., boats 3 through 12); and
  • authority for using a block buy contract to procure the five Columbia-class boats that are scheduled to be procured in FY2026-FY2030 (i.e., boats 3 through 7).

Issues for Congress for the Columbia-class program include

  • the impact of an estimated 17-month delay in the delivery of the first Columbia-class boat on the Navy's plans for replacing Ohio-class SSBNs on a timely basis, and
  • the potential impact of the Columbia-class construction workload on the ability of the submarine construction industrial base to build Virginia-class submarines in desired numbers in coming years.

Decisions that Congress makes on these issues could substantially affect U.S. military capabilities and funding requirements, and the U.S. shipbuilding industrial base.

Introduction

This report provides background information and potential oversight issues for Congress on the Navy's Columbia (SSBN-826) class program, which aims to design and build a class of 12 new ballistic missile submarines (SSBNs) to replace the Navy's current force of 14 aging Ohio-class SSBNs. Since 2013, the Navy has consistently identified the Columbia-class program as the Navy's top priority program. The Navy procured the first Columbia-class boat in FY2021 and the second in FY2024. Navy plans call for procuring the remaining 10 boats in the class at a rate of one boat per year in FY2026-FY2035.

The Navy's FY2026 budget submission requests

  • the procurement of the third boat in the class;
  • authority to use three-year incremental funding for procuring each of the remaining 10 boats in the program (i.e., boats 3 through 12); and
  • authority for using a block buy contract to procure the five Columbia-class boats that are scheduled to be procured in FY2026-FY2030 (i.e., boats 3 through 7).

Issues for Congress for the Columbia-class program include

  • the impact of an estimated 17-month delay in the delivery of the first Columbia-class boat on the Navy's plans for replacing Ohio-class SSBNs on a timely basis, and
  • the potential impact of the Columbia-class construction workload on the ability of the submarine construction industrial base to build Virginia-class submarines in desired numbers in coming years.

Decisions that Congress makes on these issues could substantially affect U.S. military capabilities and funding requirements, and the U.S. shipbuilding industrial base.

This report focuses on the Columbia-class program as a Navy shipbuilding program. Another CRS product—CRS In Focus IF10519, Defense Primer: Strategic Nuclear Forces, by Anya L. Fink—discusses the Columbia class as an element of future U.S. strategic nuclear forces in the context of strategic nuclear arms modernization efforts.1 Another CRS report—CRS Report RL32418, Navy Virginia-Class Submarine Program and AUKUS Submarine (Pillar 1) Project: Background and Issues for Congress, by Ronald O'Rourke—discusses the Navy's Virginia-class attack submarine program.

Background

U.S. Navy SSBNs in General

Mission of SSBNs

The U.S. Navy operates three kinds of submarines—nuclear-powered attack submarines (SSNs), nuclear-powered cruise missile submarines (SSGNs), and nuclear-powered ballistic missile submarines (SSBNs).2 The SSNs and SSGNs are multi-mission ships that perform a variety of peacetime and wartime missions.3 Since the early 1990s, they have not carried nuclear weapons, but the United States has reserved a right to rearm SSNs with nuclear-armed cruise missiles at some point in the future should conditions warrant, and the Navy is currently developing a new nuclear weapon called the nuclear-armed sea-launched cruise missile (SLCM-N) that could be placed on Navy SSNs at some point in the future.4

In contrast to the multi-mission SSNs and SSGNs, the SSBNs perform a single mission of strategic nuclear deterrence. To perform this mission, SSBNs are armed with submarine-launched ballistic missiles (SLBMs), which are large, long-range missiles that can be armed with multiple nuclear warheads. SSBNs launch their SLBMs from large-diameter vertical launch tubes located in the middle section of the boat.5 The SSBNs' basic mission is to remain hidden at sea with their SLBMs, so as to deter a nuclear attack on the United States by another country by demonstrating to other countries that the United States has an assured second-strike capability, meaning a survivable system for carrying out a retaliatory nuclear attack.

Navy SSBNs, which are sometimes referred to informally as "boomers,"6 form one of three legs of the U.S. strategic nuclear deterrent force, or "triad," which also includes land-based intercontinental ballistic missiles (ICBMs) and land-based long-range bombers. At any given moment, some of the Navy's SSBNs are conducting nuclear deterrent patrols. The Department of Defense's (DOD's) report on the 2018 Nuclear Posture Review (NPR), released on February 2, 2018, states the following:

Ballistic missile submarines are the most survivable leg of the triad. When on patrol, SSBNs are, at present, virtually undetectable, and there are no known, near-term credible threats to the survivability of the SSBN force. Nevertheless, we will continue to hedge against the possibility that advances in anti-submarine warfare could make the SSBN force less survivable in the future.7

Current Ohio-Class SSBNs

The Navy currently operates 14 Ohio (SSBN-726) class SSBNs (see Figure 1). The boats are commonly called Trident SSBNs or simply Tridents because they carry Trident D-5 SLBMs. They were procured in FY1977-FY1991 and entered service in 1984-1997. They were designed and built by General Dynamics' Electric Boat Division (GD/EB) of Groton, CT, and Quonset Point, RI. They were originally designed for 30-year service lives but were later certified for 42-year service lives, consisting of two approximately 19-year periods of operation separated by an approximately four-year midlife nuclear refueling overhaul, called an engineered refueling overhaul (ERO). The nuclear refueling overhaul includes a nuclear refueling and additional overhaul work that is not related to the nuclear refueling.8

Figure 1. Ohio (SSBN-726) Class SSBN

With the hatches to some of its SLBM launch tubes open

Source: Cropped version of U.S. Navy photograph.

The Ohio-class boats were originally designed to each carry 24 SLBMs. As part of the U.S. plan for complying with U.S.-Russia strategic nuclear arms control limits, four SLBM launch tubes on each boat were deactivated, reducing to 20 the number of SLBMs they can each carry. Section 20008(a)(8) of the FY2025 reconciliation act (aka One Big Beautiful Bill Act, or OBBBA) (H.R. 1/P.L. 119-21 of July 4, 2025) provides $62.0 million in FY2025 funding "to convert Ohio-class submarine tubes to accept additional missiles, not to be obligated before March 1, 2026."

Eight of the 14 Ohio-class SSBNs are homeported at Bangor, WA, in Puget Sound; the other six are homeported at Kings Bay, GA, close to the Florida border. Unlike most Navy ships, which are operated by single crews, Navy SSBNs are operated by alternating crews (called the Blue and Gold crews) so as to maximize the percentage of time that they spend at sea in deployed status.

The first of the 14 Ohio-class SSBNs (SSBN-730) will reach the end of its 42-year service life in 2027. The remaining 13 will reach the ends of their service lives at a rate of roughly one ship per year thereafter, with the 14th reaching the end of its service life in 2040.

The Navy has initiated a program to refurbish and extend the service lives of D-5 SLBMs to about 2040. As Columbia-class SSBNs begin to replace Ohio-class boats, refurbished D-5s carried by retiring Ohio-class boats will be transferred to new Columbia-class boats. Columbia-class boats will continue to be armed with these refurbished D-5s until about 2040, at which time the D-5s are to be replaced by a successor SLBM.

Including the Ohio class, the Navy has operated four classes of SSBNs since 1959. For a table summarizing these four classes, see Appendix A.

U.S.-UK Cooperation on SLBMs and the New UK SSBN

As one expression of U.S.-UK cooperation on nuclear weapon matters that dates back to World War II, the UK's four Vanguard-class SSBNs, which entered service in 1993-1999, each carry 16 Trident II D-5 SLBMs, and previous classes of UK SSBNs similarly carried earlier-generation U.S. SLBMs.9 The UK plans to replace the four Vanguard-class boats with three or four Dreadnought-class next-generation SSBNs. Dreadnought-class boats are to be equipped with 12 SLBM missile launch tubes, but current UK plans call for each boat to carry eight D-5 SLBMs, with the other four tubes not being used for SLBMs. The United States is providing technical assistance to the United Kingdom for the Dreadnought-class program, as it has over the years for some other UK submarine programs; for additional discussion, see Appendix B.

Submarine Construction Industrial Base

U.S. Navy submarines are built at two shipyards—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. GD/EB and HII/NNS are the only two shipyards in the country capable of building nuclear-powered ships, and the only two capable of performing final assembly of submarines. GD/EB builds submarines only, while HII/NNS also builds nuclear-powered aircraft carriers and is capable of building other types of surface ships. The two yards currently are jointly building Virginia-class attack submarines.10

In addition to GD/EB and HII/NNS, the submarine construction industrial base includes 20 or more strategic outsources (facilities for building submarine structures), hundreds of material and component supplier firms, and laboratories and research facilities. These additional elements of the submarine construction industrial base are located in numerous U.S. states. About 70% of the critical suppliers for the construction of submarines are sole-source suppliers.11 For nuclear-propulsion component suppliers, an additional source of stabilizing work is the Navy's nuclear-powered aircraft carrier construction program.12

Much of the design and engineering portion of the submarine construction industrial base is resident at GD/EB. Additional portions are resident at HII/NNS and some of the component makers.

Columbia-Class Program

Navy's Top Priority Program

Navy officials have stated consistently since September 2013 that the Columbia-class program is the Navy's top priority program, and that this means, among other things, that from the Navy's perspective, the Columbia-class program will be funded, even if that comes at the expense of funding for other Navy programs, and that in a situation of industrial base constraints, the Columbia-class program will have first call on resources to minimize the chances of schedule delays in building the boats.13 The status of the Columbia-class program as the Navy's top priority program reflects the importance of the SSBNs' strategic nuclear deterrence mission.

Program Name, Origin, and Milestones

Until 2016, the Columbia-class program was known as the Ohio replacement program (ORP) or SSBN(X) program,14 and boats in the class were referred to as Ohio replacement boats or SSBNXs.

As discussed in the CRS report on Navy ship names, on December 14, 2016, the Navy announced that SSBN-826, the first boat (aka lead boat) in the class, would be named Columbia, in honor of the District of Columbia. Consequently, since December 2016, the 12 or more planned boats have been referred to as Columbia (SSBN-826) class boats. On June 3, 2022, the Navy announced that it was modifying SSBN-826's name from Columbia to District of Columbia, so as to avoid an overlap in names with USS Columbia (SSN-771), a Los Angeles (SSN-688) class attack submarine that was named for Columbia, SC; Columbia, IL; and Columbia, MO. The Navy states that notwithstanding the modification to SSBN-826's name, the 12 or more planned new SSBNs will continue to be referred to as Columbia (SSBN-826) class boats.15

For information on the Columbia-class program's origin and milestones, see Appendix C.

Design and Production

Design

The Columbia-class design (see Figure 2 and Figure 3) includes 16 SLBM tubes, as opposed to 24 SLBM tubes (of which 20 are currently used for SLBMs) on Ohio-class SSBNs. Although the Columbia-class design has fewer SLBM tubes than the Ohio-class design, it is larger than the Ohio-class design in terms of submerged displacement. The Columbia-class design, like the Ohio-class design before it, will be the largest submarine ever built by the United States.

Figure 2. Columbia (SSBN-826) Class SSBN

Artist's rendering

Source: Cropped version of illustration accompanying David B. Larter, "US Navy Inks $9.4B Contract for two Columbia-class Nuclear Missile Submarines," Defense News, November 5, 2020. A caption to the image credits it to the U.S. Navy.

Figure 3. Columbia (SSBN-826) Class SSBN

Notional cutaway illustration

Source: Detail of slide 2, entitled "OHIO Replacement Program System Description," in Navy briefing on Columbia-class program presented by Captain William J. Brougham, Program Manager of PMS 397 (i.e., Project Manager Shipbuilding, Office Code 397, the office for the Columbia-class program), at the Sea, Air, and Space Symposium, April 8, 2014, posted at InsideDefense.com (subscription required), April 9, 2014.

Current U.S. and UK plans call for the Columbia-class and the UK's Dreadnought-class SSBN to use a missile compartment—the middle section of the boat with the SLBM launch tubes—of the same general design called the Common Missile Compartment (CMC).16 As Dreadnought-class boats are to be equipped with 12 SLBM missile launch tubes, but current UK plans call for each boat to carry eight D-5 SLBMs, with the other four tubes not being used for SLBMs. The modular design of the CMC will accommodate the difference in the number of SLBM missile launch tubes between the Columbia-class design and the Dreadnaught-class design. The UK provided some of the funding for the design of the CMC, including a large portion of the initial funding.17

For additional background information on the Columbia-class design, see Appendix D.

Production: Integrated Enterprise Plan (IEP)

The Navy, under a plan it calls the Integrated Enterprise Plan (IEP), plans to build Columbia-class boats jointly at GD/EB and HII/NNS, with most of the work going to GD/EB. (The IEP was previously called the Submarine Unified Build Strategy, or SUBS.) As part of this plan, the Navy is adjusting the division of work on the Virginia-class attack submarine program (in which boats are jointly built at GD/EB and HII/NNS),18 so that HII/NNS will receive a larger share of the final-assembly work for that program than it has received in the past.19

Procurement Quantity

Planned Quantity of 12

Current Navy plans call for procuring 12 Columbia-class boats to replace the current force of 14 Ohio-class SSBNs. In explaining the planned procurement quantity of 12 boats, the Navy states the following:

  • Ten operational SSBNs—meaning boats not encumbered by lengthy maintenance actions such as a midlife overhaul—are needed to meet strategic nuclear deterrence requirements for having a certain number of SSBNs at sea at any given moment.
  • Fourteen Ohio-class boats were needed to meet the requirement for 10 operational boats because, during the middle years of the Ohio class life cycle, three and sometimes four of the boats were nonoperational at any given moment on account of being in the midst of lengthy midlife nuclear refueling overhauls or other extended maintenance actions.
  • Twelve (rather than 14) Columbia-class boats will be needed to meet the requirement for 10 operational boats because the midlife overhauls of Columbia-class boats, which will not include a nuclear refueling, will require less time (about two years) than the midlife refueling overhauls of Ohio-class boats (which require about four years from contract award to delivery), the result being that only two Columbia-class boats (rather than three or sometimes four) will be in the midst of midlife overhauls or other extended maintenance actions at any given moment during the middle years of the Columbia-class life cycle.20
Potential for Increase to Something More than 12

The Trump Administration's Nuclear Posture Review (NPR), released in February 2018, states the following: "The COLUMBIA-class program will deliver a minimum of 12 SSBNs to replace the current OHIO fleet and is designed to provide required capabilities for decades."21 The use of the word "minimum" in that sentence can be viewed as signaling a possibility that the required number of Columbia-class boats might at some point be increased to something more than 12 boats.22 An October 2023 report by a congressional commission on U.S. strategic posture recommended increasing the total planned number of Columbia-class boats to something more than 12.23

Procurement Schedule, Lead Boat Schedule, Lead Boat Delivery Delay

Procurement Schedule

As noted earlier, the Navy procured the first Columbia-class boat in FY2021 and the second Columbia-class boat in FY2024. The Navy wants to procure the remaining 10 boats in the program—boats 3 through 12—at a rate of one per year in FY2026-FY2035. After being delivered to the Navy, the lead boat is to undergo substantial testing prior to serving on its first deterrent patrol.

Taking into account both projected delivery dates for Columbia-class boats and projected retirement dates for Ohio-class boats, the Navy's FY2025 30-year (FY2025-FY2054) shipbuilding plan projects that the SSBN force will include 14 boats in FY2025-FY2026, 13 boats in FY2027-FY2029, and 12 boats for the remainder of the 30-year period (except for FY2040-FY2041, when it is projected to include 13 boats). (The Navy did not submit an FY2026 30-year shipbuilding plan.) The Navy is planning to extend the service lives of up to five Ohio-class SSBNs to hedge against potential delays in the deliveries of Columbia-class boats.24

Lead Boat Schedule

The schedule for designing and building the lead Columbia-class boat and having it ready for an intended scheduled first deterrent patrol in late 2030 or 2031 includes little margin for absorbing design or construction delays. The tightness in the lead boat's design and construction schedule has been a principal feature of the program (along with the program's high priority) for several years. Much of the management time and attention that the Navy devotes to the program is focused on anticipating, monitoring, and mitigating risks to the lead boat's design and construction schedule.

Lead Boat Delivery Delay

On April 2, 2024, the Navy announced that several of its shipbuilding programs were experiencing significant delays due to shipyard workforce challenges, supply chain challenges, and other issues. As part of this announcement, the Navy announced an estimated 12- to 16-month delay in the delivery of the first Columbia-class boat. An April 2, 2024, press report stated,

The vessel's new projected delay can't be attributed to one factor or a new technical issue, Navy officials told reporters Tuesday [April 2]. Instead, the delays are "related to the whole of the ship," in terms of assembling its modules correctly, "getting them all buttoned up," said Navy assistant secretary for acquisition Nickolas Guertin.

And although some components are late, the projected delays don't appear related to technology performance issue, said Naval Sea Systems Command head Vice Admiral Jim Downey.25

An April 10, 2024, press report states,

Late delivery of steam turbines for the under-construction District of Columbia (SSBN-826) is one of the main obstacles the Navy faces in delivering the nuclear ballistic missile submarine on time, Secretary of the Navy Carlos Del Toro told a House panel on Wednesday [April 10].

"One of the most significant challenges that we have with Columbia … is actually the late delivery of the turbine generator to Columbia by subcontractor Northrop Grumman," Del Toro the House Appropriations subcommittee on defense.

"That has had a major impact on the Columbia."…

In addition to the turbines, sources familiar with the slip in schedule have also pointed to the delay in completing the bow dome of District of Columbia. The dome, the same design as the Ohio-class, is getting cast at forge at HII's Newport News Shipbuilding in Virginia.26

An April 17, 2024, press report states,

A delay of as much as 16 months in delivering the first of the US's first Columbia-class nuclear-missile submarines—the Navy's top weapons priority—stems from contractor delays in delivering the vessel's bow section and power generators, according to an internal assessment by the service….

… HII was to ship the bow in May 2025 from its Newport News, Virginia, yard to the General Dynamics facility in Groton, Connecticut. That's now estimated for June 2026, or 13 months late, according to internal service figures….

In addition, Northrop Grumman Corp. was contracted by the Navy to deliver the first ship's turbine generators by November 2021, which would have provided months of margin before they'd be needed.

Instead, the turbine generators are projected to be delivered in early 2025, according to a Navy statement.27

The Navy's FY2026 budget submission updated the estimated delay in the delivery of the first Columbia-class boat to 17 months.

Program Cost and Funding

Program Acquisition Cost

Estimates of the procurement cost and acquisition cost (i.e., the research and development cost plus procurement cost) of the Columbia-class program include the following:

  • The Navy's FY2025 budget submission estimates the total procurement cost of the 12-ship class at $126.4 billion in then-year dollars, an increase of 15.2% over the figure in the FY2021 budget submission of $109.8 billion in then-year dollars. (The Navy's FY2026 budget submission does not include an updated estimate of the total procurement cost of the 12-ship class.)
  • A December 31, 2023, DOD Modernized Selected Acquisition Report (MSAR) for the Columbia-class program estimates the program's total acquisition cost at $139,716.8 million (about $139.7 billion) in then-year dollars, including $13,938.2 million (about $13.9 billion) in research and development costs, $125,320.2 million (about $125.3 billion) in procurement costs, and $458.4 million in military construction costs.28
  • A June 2025 Government Accountability Office (GAO) report assessing selected major weapon acquisition programs being pursued by the Department of Defense (DOD), which is "using a secondary Department of War designation," under Executive Order 14347, dated September 5, 2025, stated that the estimated total acquisition cost of the Columbia-class program as of August 2024 was $126,495 million (about $126.5 billion) in constant FY2025 dollars, an increase of about 6% from the cost as estimated in August 2023, including $16,651 million (about $16.7 billion) in research and development costs, $109,408 million (about $109.4 billion) in procurement costs, and $436 million for military construction and acquisition-related operation and maintenance costs.29

The above estimates do not include estimated costs for refurbishing D-5 SLBMs so as to extend their service lives to about 2040.

Unit Procurement Cost

Table 1 shows the estimated procurement costs of the first three boats in the program, as shown in the Navy's FY2026 budget submission. The lead boat's procurement cost is much higher than that of subsequent boats in the class because the lead boat includes most of the detail design/nonrecurring engineering (DD/NRE) costs for the class. (It is a long-standing Navy budgetary practice to incorporate the much or all of the DD/NRE costs for a new class of ship into the total procurement cost of the first ship in the class.) In the table, the category shown as "Plans" is similar to DD/NRE, while the category shown as "Other," which includes all other procurement costs, can be viewed as the hands-on construction cost of the boat. As can be seen in the table, the first three boats in the program have estimated hands-on construction costs of more than $9 billion each.

Table 1. Estimated Procurement Costs for First Three Boats

In millions of dollars, rounded to nearest tenth

First boat (SSBN-826)

Second boat (SSBN-827)

Third boat (SSBN-828)

Plans

6,946.3

1,443.3

969.6

Other

9,175.0

9,245.2

9,574.2

Total

16,121.3

10,688.5

10,543.7

Source: Table prepared by CRS using data from Navy's FY2026 budget submission. Totals may not add due to rounding.

Notes: "Other" category includes basic construction/conversion; change orders; electronics; propulsion equipment; hull, mechanical, and electrical (HM&E) equipment; ordnance-related equipment (but not the weapons themselves, which are procured separately); and other costs.

CBO and GAO Perspectives on Risk of Cost Growth

Regarding the risk of cost growth in the Columbia-class program, a January 2025 CBO report on the cost of the Navy's shipbuilding programs states,

The cost of the 10 Columbia class submarines included in the [Navy's FY]2025 shipbuilding plan is one of the most significant uncertainties in the Navy's and CBO's analyses of future shipbuilding costs….

The Navy currently estimates that construction of the first Columbia class ship, the District of Columbia, will be complete in 2029 at a cost of $16.1 billion (in 2024 dollars). As of November 2024, the ship was 51 percent complete (measured in terms of the number of labor hours the Navy estimates it will need to build the ship). The second ship, authorized in 2024, would cost about $9.0 billion. Subsequent ships in the class would cost $7.9 billion, on average, according to the Navy. The total procurement cost for the 12 submarines would be $106 billion (which includes appropriations totaling $27.4 billion from 2017 to 2024), or $8.8 billion per ship, on average.

According to the Navy's estimate, the cost per thousand tons of displacement for the first Columbia class ship would be 13 percent less than that of the first Virginia class attack submarine. But the costs of lead ships of new classes of submarines built in the 1970s and 1980s provide little evidence that ballistic missile submarines are cheaper to build, per ton, than attack submarines. In a February 2024 report to the Congress on the Columbia program, the Navy stated that there was a 68 percent chance that the cost of the first Columbia class submarine would exceed its estimates and a 32 percent chance that it would cost less than estimated. The likelihood that subsequent ships in the class would cost more or less than estimated was similar—67 percent and 33 percent, respectively. Those estimates of the probability of cost growth were substantially higher than the estimates that the service provided the year before. When CBO analyzed the 2024 shipbuilding plan, the Navy had stated that the likelihood that cost growth would affect the lead ship was 54 percent; the probability of subsequent ships' being affected was 49 percent.

CBO's estimate for a program of 12 ships is 16 percent higher than the Navy's. CBO estimates that the first Columbia class submarine will cost $18.1 billion—$2.0 billion more than the Navy estimates it will cost. The second submarine would cost $11.4 billion. Including appropriations from 2017 to 2024, CBO estimates that, all told, 12 Columbia class submarines would cost $123 billion ($95 billion of which would be appropriated from 2025 to 2036). The 10 submarines set to follow the first two ships would cost an average of $9.4 billion each—$1.5 billion more per submarine than the Navy estimates they would cost.

Costs for the Columbia class submarines could, however, exceed both the Navy's and CBO's estimates. The new SSBN will be the largest, most technologically complex submarine that the United States has ever built. It is expected to reuse some technology and components from the Virginia class submarine, but it would also include many new elements, such as an all-electric drive system, an X-stern ship control system (in which the rear rudders and dive planes are shaped like an "x" rather than a "+" as they are on the Ohio class submarines), a new missile compartment, and a nuclear reactor designed to last the entire 42-year service life of the submarine. Furthermore, the Navy has repeatedly stated that the Columbia is its first acquisition priority and that the program must stay on schedule to meet its strategic deterrence mission. Thus, if the program encounters problems in construction, the Navy and the shipbuilders are likely to invest more resources and assign more people to the program to meet the schedule, all of which would increase costs.

Conversely, costs for the Columbia class ships could be less than CBO estimates if the Navy and the shipbuilders are successful in their ongoing efforts to increase the speed and efficiency of construction and to improve the performance of the supplier base.30

A September 2024 GAO report on the Columbia-class program states,

According to GAO's analysis of program data from January 2022 through May 2023, cost and schedule performance for lead submarine construction has consistently fallen short of targets. Through early 2024, those trends had not improved, and future risks will likely add to current cost and schedule growth. The program has reported that the shipbuilder needs to take swift and significant actions to address the causes of poor construction performance. However, as GAO has previously reported, the program has tried to mitigate some of these causes—such as late materials and detailed design products—for years….

Based on data through May 2023, GAO estimated that lead submarine construction costs at completion could be hundreds of millions of dollars more than the Navy's planned costs. Although the shipbuilder is also expecting cost increases, its estimated overrun is smaller and assumes significant future improvement that GAO's past work suggests is unrealistic. Further, program reporting on submarine construction progress did not always include a thorough analysis of why the program missed cost and schedule goals. Without realistic cost estimates and adequate analysis, the program will struggle to address continuing and future risks that could further degrade construction performance.

The Navy has not consistently defined information needed to determine whether investments made in the supplier base have increased supplier production or generated cost savings and how those results support the program's goals. Since 2018, the Navy reported receiving more than $2.6 billion to invest in the submarine supplier base and help achieve Columbia class construction goals. Without identifying consistent information, the Navy is not well positioned to ensure that these investments will effectively spur their intended benefits for the program.31

Use of Incremental Funding

The first and second Columbia-class boats were funded with incremental funding, a funding approach in which the procurement cost of each boat is divided into multiple annual increments, with the first increment occurring in the year in which the boat was procured.32 The first Columbia-class boat was funded with three-year incremental funding in FY2021-FY2023, and the second boat was funded with two-year incremental funding (also called split funding) in FY2024-FY2025. The Navy wants to use three-year incremental funding for procuring the third and subsequent boats in the program.