Problem Plagued Sentinel ICBM Program Will Press Ahead Despite Nearly Doubling In Cost

The U.S. Air Force is pushing ahead with its struggling Sentinel intercontinental ballistic missile (ICBM) program despite a new projected price tag of nearly $141 billion, close to twice the original estimate, and now years of expected delays. The Pentagon says it has assessed that there are no lower-cost, but similarly capable alternatives to Sentinel, which is expected to replace the existing Minuteman III ICBM as one of the three legs of America’s nuclear deterrent triad.

The Office of the Secretary of Defense announced the results of an official review of the Sentinel program today. By law, per what is commonly referred to as the Nunn-McCurdy Amendment, defense programs that see certain levels of extreme cost growth must be canceled unless various criteria are met. Sentinel’s rising price point triggered a breach of the Nunn-McCurdy statute in January. The Air Force also sacked the top officer in charge of the program last month, but said this was “not directly related to the Nunn-McCurdy review,” according to Defense One.

The Air Force currently has some 400 LGM-30G Minuteman IIIs deployed in silos spread across five states.

“Total program acquisition costs for a reasonably modified Sentinel program are estimated by CAPE [the Office of Cost Assessment and Program Evaluation] to be $140.9 billion, an increase of 81 percent compared to estimates at the program’s previous Milestone B decision in September 2020,” according to a press release the Pentagon put out today. “The Nunn-McCurdy review determined that the majority of the cost growth is in Sentinel’s command and launch segment, which includes the launch facilities, launch centers, and the process, duration, staffing, and facilities to execute the conversion from Minuteman III to Sentinel.”

Per the Pentagon, the review arrived at the following key determinations to continue the Sentinel program despite the cost breach:

• “Continuation of the Sentinel program is essential to national security.”

• “There are no alternatives to the program which will provide acceptable capability to meet the joint requirements at less cost.”

• “The new estimates of the program acquisition unit cost or procurement unit cost have been determined by the Director of Cost Assessment and Program Evaluation (CAPE) to be reasonable.”

• “The program is a higher priority than programs whose funding must be reduced to accommodate the growth in cost of the program.”

• “The management structure for the program is adequate to manage and control program acquisition unit cost or procurement unit cost.”

The Pentagon and the Air Force have both previously said that Sentinel cost growth is primarily associated with required upgrades to existing missile silos and other launch and command and control infrastructure rather than the missile itself, which is designated the LGM-35A. The average expected unit cost of the LGM-35As, which Northrop Grumman is developing, has still grown now, to approximately $214 million from the original projected $118 million, due to the overall increase in program cost. The estimated unit prices presented here notably factor in costs unrelated to the missiles themselves.

It is also important to note that the Air Force is now in the process of restructuring the Sentinel program, which will lead to a further revised cost baseline, which could be greater (or less) than the $140.9 billion figure CAPE produced as part of the Nunn-McCurdy review. Reworking the Sentinel program is expected to take between 18 and 24 months.

“This certification does not indicate business as usual,” Dr. William LaPlante, Under Secretary of Defense for Acquisition and Sustainment, insisted in a call with reporters, including from The War Zone, earlier today. “The program will be restructured to address the root causes of the breach and ensure an appropriate management structure is in place to control costs.”

“The reason why we now know about those [sic] projected cost growth is because we’ve dramatically accelerated the maturity of the design of the ground segment – that’s where the vast majority of this cost growth… resides and is being driven by,” Andrew Hunter, Assistant Secretary of the Air Force for Acquisition, Technology and Logistics, also noted while speaking alongside Under Secretary LaPlante on today’s press call. “That increase in maturity happened because Dr. LaPlante approved change an acquisition strategy so that we would get after the construction design and testing of those ground segments earlier in the program compared to the previous plan. So as he identified there were some gaps in maturity… we moved to accelerate those elements of the program [and] we uncovered the growth in the size of the ground segment and that’s really the driver of the cost growth.”

No clear explanation was given today as to how the Sentinel program had been able to proceed initially without this fuller understanding of the expected costs of the non-missile elements. It is also unclear what would’ve happened had all of this only emerged later in the process as originally planned.

Details about the now-expected modifications to the Sentinel program are limited and could change as the Air Force makes its way through the restructuring process.

However, it is set to include “basically a scaling back of the size and some of the details of the complexity of the launch facility,” according to Under Secretary LaPlante. “The other piece that happens when you scale it back is it also reduces the timeline of doing the transition between the existing system Minuteman III and the new system.”

The Air Force has already made major changes to its nuclear enterprise in part in response to problems with Sentinel, including the creation of a new Nuclear Oversight Committee and the establishment of a dedicated Program Executive Office for ICBMs.

In addition, no new date is available yet for when the first LGM-35As might begin to enter service, which is now expected to be years behind schedule. The publicly stated goal has previously been for the transition from Minuteman III to Sentinel to occur sometime in the 2030s. The existing aging ICBMs will have to be sustained in the interim.

The Pentagon and the Air Force say they continue to assess that keeping Minuteman III in service indefinitely is not a viable alternative to Sentinel. Under Secretary LaPlante said today that “hybrid options of different ground facilities” and “mobile [ICBMs] versus fixed [silo-based]” types were evaluated as part of the Nunn-McCurdy review.

As part of the process of settling on Sentinel in the first place, the Air Force previously explored keeping Minuteman III, loading existing silos with a derivative of the U.S. Navy’s Trident II nuclear-armed submarine-launched ballistic missile, and firing new ICBMs from launchers at the bottom of lakes or hidden inside tunnels, as you can read more about here. U.S. officials continue to rebuff broader questions and criticisms about the overall utility of the ICBM leg of the nuclear triad have been raised on multiple occasions in the past, as The War Zone has explored in detail in the past. Some members of Congress have also more recently called for reexamining the possibility of acquiring new road-mobile ICBMs, a capability the U.S. military currently does not possess.

“Each leg [of the triad] brings unique complementary attributes, which are mutually supporting and key to signaling and establishing deterrence amidst an increasingly complex and dynamic security environment, which for the first time includes the People’s Republic of China as a major nuclear armed power and strategic competitor,” Vice Chief of Staff of the U.S. Air Force Gen. Jim Slife, who was also on today’s press call, said. “The land leg’s geographic dispersal creates targeting problems for our adversaries and our missileers, sitting in an alert posture 24/7, ensures responsiveness.”

News about the Air Force persisting with Sentinel despite major cost growth also follows the service’s top leadership warning about the potential for serious budget cuts starting in the 2026 Fiscal Year. Elements of the service’s flagship Next Generation Air Dominance (NGAD) initiative, especially plans for a new crewed sixth-generation stealth combat jet, could be at risk.

How the need to pay for Sentinel’s nearly doubled price tag will factor into all this and how non-nuclear programs in particular might be affected remains to be seen.

“So our current cost profile does not suggest that any of the cost growth in the Sentinel program will be realized over the course of the next five years,” according to Vice Chief of Staff Slife. “So, really, it is a decision for down the road to decide what trade-offs we’re going to need to make in order to be able to continue to pursue the Sentinel program.”

Whether budgets beyond the Air Force’s could be impacted is also unclear. Sentinel is part of a larger effort to modernize the entire U.S. nuclear arsenal that includes other high-priced programs like the B-21 Raider stealth bomber, Columbia class nuclear ballistic missile submarine, and B61-12 nuclear bomb. The Columbia submarine program is notably facing its own cost and schedule concerns.

“We believe we are on the right path moving together and forward, and despite the historic scale and complexity, we can do this,” Under Secretary LaPlante concluded in his comments today. “We know we have to get this right and we will.”

At the same time, with much about the Sentinel program’s expected costs and future budgets very much up in the air, as well as renewed calls from Congress to reconsider alternatives, there seems to significant uncertainty now in the path forward for America’s next ICBM.

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