GAO Warns of Potential Columbia-class SSBN Delays & Overruns


A US Navy rendering of the Columbia-class ballistic missile submarine.

The Government Accountability Agency (GAO), an independent watchdog which is congressionally-mandated to audit various government programs and report on its findings, has released its evaluation of the Columbia-class nuclear ballistic missile submarine (SSBN) program. The Columbia class will replace the Ohio class in US Navy service, providing around-the-clock sea-based nuclear deterrence via its payload of 16 Trident D5 ballistic missiles.

The sea-based leg of the nuclear triad is often considered the most survivable, as ballistic missiles submarines conduct their patrols hidden in the vast expanses of the ocean. The land-based and bomber-based legs, in contrast, are based in known locations and could be targeted in a preemptive strike. As such, it is critical that the Columbia-class SSBN enter service soon enough to replace the older Ohio-class boats as they age out.

However, the road to an operational Columbia class may not be an easy one. In a report entitled “COLUMBIA CLASS SUBMARINE: Immature Technologies Present Risks to Achieving Cost, Schedule, and Performance Goals,” the GAO warns that the US Navy is under-representing the level of risk present in many of the program’s key systems, which could result in budgetary and schedule overruns.

The report identifies the “Integrated Power System, nuclear reactor, common missile compartment, and propulsor and related coordinated stern technologies” as notable risky systems. Clearly, issues with components as critical as the nuclear reactor and missile compartment would hold up the entire program and potentially require alteration of other systems, hence the GAO’s warning that the under-estimation of risk could delay delivery and introduction.


The Integrated Power System (IPS), which features a stealthy electric powertrain, has not been demonstrated with a full-size installation and is at Technological Readiness Level (TRL) 6, which is below the TRL 7 threshold used by the GAO for system maturity. While there are other US Navy ships with electric propulsion in service, the GAO notes that these applications “are somewhat different than what is planned for the Columbia class and [are not] powered by [] nuclear reactor[s].” Planning at full power in a land-based installation should commence sometime between 2018 and 2020, at which time production contracts may already have been awarded. While the GAO does not consider this ideal, they at least commend the Navy for testing a full-size prototype at all — the DDG 1000 (Zumwalt-class) program only tested at half power and experienced difficulties with the full-scale installation as a result.

With regards to the reactor, the GAO notes that the Navy has been testing a reactor similar to the Columbia class’s for several years to validate the relevant technologies. However, it does not appear that the design of the Columbia class’s reactor will be finished in time for the first contract awards, as design work will only be 65% complete in 2018.

The section concerning propulsion is notable for the GAO’s disagreement with the Navy over the degree of commonality between the Columbia class and the Virginia class. From the report:

Navy officials told us that the propulsor effort is based on prior experience
with propulsors and that it will resemble the Virginia-class propulsor
design. However, according to Navy documentation, the propulsor will be
different in form, fit, and function than prior propulsors.

The GAO reports that the Navy has yet to carry out full-scale testing on the propulsor and has not downselected to a single vendor. Furthermore, other systems which are critical to propulsor function, such as the driveshaft and bearings, have not been tested full-scale either. The dive planes, which are in an X configuration, will need to be tested with the propulsor as well.

Next, the report discusses the so-called “Stern Area System (SAS).” The SAS is classified and its function is not explained in the document — a cursory search did not find any references to a “stern area system” except in relation to the Columbia class. While the function of the SAS is unclear, the GAO says that its level of technological readiness is especially low — TRL 4 — meaning it has not even gone through a critical design review and likely poses a more serious risk than the other systems mentioned in the report. The GAO notes that, while some important SAS components do have higher-maturity analogues, using such off-the-shelf components would cause the submarine to miss unspecified performance metrics.

The Common Missile Compartment (CMC) is the last system covered. The GAO prefaces its section on the CMC by noting that “shipbuilders and the Navy have described CMC as complex to build.” Current plans call for the CMC to be installed in a Royal Navy submarine in 2020 and for extensive land-based testing as well, which will continue into the early 2020s.

Of all these systems identified by the GAO as below the desired TRL, the only system categorized by the Navy as a Critical Technology Element (CTE) was the SAS, hence the GAO’s conclusion that the Navy “underrepresent[ed] the technical risk facing the program.”

Should stakeholders be worried?

While the GAO’s report may seem damning, there is certainly room for debate as to whether its findings point to bad procurement practices or whether the GAO’s standards for technological maturity are simply too high. The Navy’s reply to the GAO said the following: “[The GAO’s] approach would require all technologies on a shipbuilding program to be prototyped at full-scale and demonstrated in at-sea environments — essentially building a full-sized prototype submarine — before authorizing the lead ship.” This statement contains both truth and spin; what the GAO recommends is full-scale testing of important systems, which would not necessarily require the production of a complete prototype (testbeds could be used instead) but would slow the program, at least notionally.

Essentially, the Navy is gambling that it can perform testing and production simultaneously and rectify any issues on the lead vessel(s) as they crop up. While this approach does offer potentially faster fielding and cheaper procurement, it can backfire spectacularly (think the F-35 and Zumwalt class) if important systems do not perform as intended, causing overruns and potentially requiring redesign(s) or performance reductions. Given the GAO’s history of accurately predicting overruns and delays in other programs, the Navy (and indeed the whole the DoD) should be concerned by the report’s findings.

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