“Critical” Overrun of Sentinel ICBM Program Demands Government Transparency

On January 18th, the Air Force notified Congress that its program for the new Sentinel intercontinental ballistic missile (ICBM) being developed by Northrop Grumman will cost 37 percent more than projected and take at least two years longer than estimated–an overrun in ‘critical’ breach of Congress’s Nunn-McCurdy Act. Transparency from the Department of Defense and Congress over the following months will be crucial to understand the causes and consequences and ensure proper public oversight of one of the largest nuclear weapons programs in U.S. history. 

What caused the overrun?

While Air Force officials have cited inflation and unexpected infrastructure costs related to command and launch as the primary causes of the overrun, skewed cost estimates since the program’s inception and consequences of unhealthy practices related to industry competition are likely to blame as well.  

Infrastructure costs 

According to Andrew Hunter, Assistant Secretary of the Air Force for Acquisition, Technology, and Logistics, there has been a slight increase in cost of the missile itself, but the cost and schedule growth for the project is largely due to supporting infrastructure costs. The Sentinel program includes not only an entirely new long-range missile but replacement or enhancement of silos, launch command centers, and command and control facilities for the ICBM force. For example, the silos and launch facilities for Sentinel will be significantly larger than for the Minuteman missiles. Additionally, the Air Force had planned to reuse the communications infrastructure from Minuteman III for Sentinel but determined that the system was too old to fully function with the new ICBM, requiring completely new cabling. Kristyn Jones, acting Under Secretary of the Air Force, similarly cited the “massive ‘civil works’ project” as the primary overrun cause. 

The Government Accountability Office (GAO)’s annual evaluation of Pentagon weapons programs in June 2023 additionally revealed that the Sentinel program was delayed because Northrop Grumman is experiencing staffing shortfalls, clearance delays, IT infrastructure challenges, and supply chain disruptions. Northrop Grumman was issued a sole-source, $13.3 billion contract for the program in September 2020.

Skewed cost estimates

A 2016 Air Force cost analysis for the Sentinel program (previously known as the Ground Based Strategic Deterrent or GBSD) concluded that replacing the existing force of Minuteman III ICBMs would be cheaper than a life-extension program. The assumptions that led to this assessment, however, were flawed and potentially skewed to favor a full replacement of the ICBM program.

The primary factor leading to the Air Force’s determination that a life-extension of Minuteman ICBMs would be more expensive was the requirement from their Analysis of Alternatives that the ICBM force level be maintained until 2075. This arbitrary requirement for force levels and timeline meant that a life-extension program for Minuteman III ICBMs would have to include the cost of building a follow-on missile to reach the 2075 requirement, ensuring a favorable look for Sentinel. Projections for a program lifespan before or after 2075–like 2050 or 2100–result in cheaper cost estimates for life-extension of Minuteman than development of Sentinel. 

As recently as 2021, Air Force Global Strike Command claimed the Sentinel program would be $38 billion cheaper than attempting to upgrade and extend the life of the Minuteman III. After the “critical” cost projection increase was made public, the Air Force insisted that “There is not a viable service life extension program that we can foresee for Minuteman III. It was fielded in the 70s as a 10-year weapon,” even though the Air Force put the Minuteman III through a complete life-extension a decade ago.

The Air Force’s first cost estimate for the Sentinel program in February 2015 was $62.3 billion (in then-year dollars). Just nine months later, the Pentagon’s cost estimation team put the number between $85 billion and $100 billion, already over one-third higher than the original estimate. After setting the estimate at $85 billion in 2016, the Air Force again increased the estimated program cost in 2020 to $95.8 billion. With the recently reported cost overrun of 37 percent, the latest cost estimate for the program––scheduled for release this year––could jump to more than $130 billion. 

The Air Force knew that the low cost projection that was used to secure Congressional approval and lock the program in was made with incomplete data. After the newest cost increase was disclosed, the Air Force acknowledged: “Some of the assumptions that were made at the beginning of the program when the initial cost estimates were made were just not particularly valid, and now we have a lot more information that should allow us to stay much closer to the cost estimates that will be developed as part of the Nunn-McCurdy process.”

Industry and competition

One persistent justification for Sentinel voiced by the Air Force is that a new missile program would help protect the large solid rocket motor (LSRM) industrial base that has suffered from consolidation in recent years. In 2018, Northrop Grumman–one of just two competitors for the Sentinel program alongside Boeing–purchased Orbital ATK, one of the two remaining LSRM manufacturers. This acquisition gave Northrop Grumman a significant advantage over Boeing, who ultimately withdrew from the Sentinel competition in 2019, citing “inherently unfair cost, resource and integration advantages.” 

With Boeing declining to bid, Northrop Grumman became the sole contract winner for the Sentinel program. Ultimately, the Air Force’s failure to mitigate anti-competitive behavior by Northrop Grumman and its awarding of an unprecedented high-value sole-source contract likely contributed to higher costs for the Sentinel program and a more unhealthy industrial base. 

The Nunn-McCurdy process

The Air Force is required to provide the overrun notification to Congress due to the Nunn-McCurdy Act, which mandates that the Pentagon disclose to Congress if a program faces cost or schedule overruns exceeding 15 percent. With a cost overrun of 37 percent, the Sentinel program is in “critical” breach of the Nunn-McCurdy Act, requiring the Secretary of Defense to conduct a root-cause analysis and renewed cost assessment. Following completion of these requirements, the program will be terminated unless the Secretary of Defense certifies the program no later than 60 days after a required Selected Acquisition Report is submitted to Congress.

Secretary of Defense Lloyd Austin will engage in these processes over the next several months to uncover the cause of the cost overrun and assess, alongside the Pentagon’s Director of Cost Assessment and Program Evaluation. Together, they will determine:

  1. the estimated cost of the program if no changes are made to the current requirements, 
  2. the estimated cost of the program if requirements are modified, 
  3. the estimated cost of reasonable alternatives to the program, and  
  4. the extent to which funding from other programs will need to be cut to cover the cost growth of this program.

The certification required to keep the program alive must then certify, in the exact words of the legislation, that: [author context and commentary added below]

  1. the program is essential to national security, [How will Secretary Austin certify this? Expert analysis has identified cheaper and more efficient alternatives to the Sentinel program and challenged the necessity of ICBMs in the U.S. arsenal.]
  2. the new cost estimates have been determined by the Director of Cost Assessment and Program Evaluation to be reasonable, [What is the standard for ‘reasonable’? Will this determination consider cheaper alternatives to the Sentinel program, such as a life-extension program of the Minuteman III ICBM? The details of this determination should be made public to ensure proper oversight, given that a Pentagon official will be making the determination for a defense program.] 
  3. the program is a higher priority than programs whose funding will be reduced to cover the increased cost of this program, and [What programs will be cut to pay for the Sentinel program? Will only other defense programs be at risk? That information and the method of determining priority should be available to the public.]
  4. the management structure is sufficient to control additional cost growth. [The continuous delays and cost growth of the Sentinel program reveal a persistent failure in program management. Any certification presented by Secretary Austin must address this failure and explain how the management structure will be altered to address it.]

If the program avoids termination, the Nunn-McCurdy Act requires that it be restructured to rectify the root cause of the overrun and receive new milestone approval. Even before the review has been completed, the Air Force argues the Sentinel program will not be canceled: “Sentinel will be funded. We’ll make the trades that it takes to make that happen.” Those “trades” may include reduction or even cancellation of other programs or asking Congress to further increase the defense budget.

Implications for force structure

Although the news and forthcoming processes related to the Sentinel overrun are largely focused on cost, the two-year schedule overrun could have critical implications for U.S. nuclear force structure as well. 

Pentagon documents have previously indicated that a two-year programmatic slippage could result in up to 35 ICBMs being removed from alert status. While several analysts have questioned the continued U.S. requirement for 400 deployed ICBMs, a provision included in each National Defense Authorization Act (NDAA) since FY 2017 legally prohibits the number of deployed ICBMS from dropping below 400. The 2023 Congressional Strategic Posture Commission appeared to acknowledge a possible dip in the ICBM number by recommending the Air Force plan to deploy the Sentinel in a MIRVed configuration.

In order to prevent this slippage, according to senior Air Force and Northrop officials, the two-year delay in achieving initial operational capability (IOC) means the Air Force will have to life-extend some Minuteman III ICBMs, something senior officials have previously argued was not possible. In defense of the Sentinel program in 2021, then-Commander of USSTRATCOM Adm. Charles Richard said, “you cannot life extend the Minuteman 3,” and argued the system is “so old that in some cases the drawings don’t exist any more.” While Sentinel is meant to replace the Minuteman missiles, the two programs will have to operate simultaneously for some time due to the delay, which will add additional cost. This delay also puts Sentinel’s IOC beyond the no-fail IOC date of September 2030 set by Air Force Global Strike Command. 

Incomplete data, rosy cost projections, and excessive secrecy appear to have combined to push the Sentinel program deep into the red. Institutional preference of getting a new weapon system rather than operating an existing missile for another decade or two has probably been another factor; the technical-cost assessment of a Minuteman III life-extension has never been made public.

The Pentagon and/or Congress should make all steps and results of this Sentinel review process open to the public to ensure maximum transparency, scrutiny, and oversight. Secretary Austin’s likely certification of the Sentinel program should be open to public interrogation, and Congress must thoroughly examine whether every certification requirement is met. Congress should ask the Government Accountability Office and Congressional Budget Office to make independent reviews. The Sentinel program has been plagued with cost increases, flawed assumptions, and misleading arguments from the beginning; this most recent overrun demands a reassessment of the Pentagon’s justification for Sentinel and hawk-eyed scrutiny of the program’s next steps.

This research was carried out with generous contributions from the New-Land Foundation, Ploughshares Fund, the Prospect Hill Foundation, Longview Philanthropy, and individual donors.