As the Air Force and Department of Defense restructure the Sentinel program, the Government Accountability Office notes there is a shift to starting to convert to new silos at the 90th Missile Wing at F.E. Warren Air Force Base (AFB), Wyo.
“Despite the delays stemming from the Sentinel restructuring, [Air Force] Global Strike Command has already taken some actions to prepare for the transition,” according to a Government Accountability Office (GAO) report, ICBM Modernization: Air Force Actions Needed to Expeditiously Address Critical Risks to Sentinel Transition (GAO-25-108466). “The Air Force has shifted the locations of non-deployed launch facilities from an equal distribution across all three missile wings, to a majority distribution at the 90th Missile Wing at F.E. Warren Air Force Base.”
This requires a significant increase in personnel requirements for LGM-35A Sentinel intercontinental ballistic missile (ICBM) by Northrop Grumman and a possible need for the service to equip the missile with multiple warheads, as the service reduces its stock of Boeing Minuteman IIIs after 2030.
On Jan. 18 last year, the Air Force said that it notified Congress that Sentinel had breached Nunn-McCurdy guidelines, primarily due to construction design changes, and then DoD acquisition chief William LaPlante ordered a root-cause analysis. The latter led to the DoD decision to continue the program, due to its stated importance to strategic deterrence, but also to the rescinding in July last year of the Sentinel Milestone B engineering and manufacturing development go-ahead from 2020. Pentagon officials said at the time that it could take 18 months to approve Sentinel again for the critical phase Engineering and Manufacturing Development (EMD) – a timeline that would mean an EMD decision by January next year.
The report, published Wednesday, is a public version of an April GAO classified report and thus “omits some information on plans and capabilities, the Sentinel test facility, and strategic deterrent requirements DOD deemed to be sensitive or classified,” according to GAO.
The Air Force fielded 450 Minuteman silos between 1962 and 1967 and decommissioned 50 between 2014 and July 2017 to comply with the 2010 New Strategic Arms Reduction Treaty (New START) with Russia.
This year, the Air Force decommissioned another Minuteman III silo, Launch Facility (LF) 5E10, at F.E. Warren–a decommissioning first reported by Breaking Defense on Sept. 3. The Air Force Global Strike Command (AFGSC) said that on April 3 it transferred LF 5E10 to Site Activation Task Force Detachment 10, which is responsible for new silos, maintenance, and communications for Sentinel at F.E. Warren. “Upon completion of an implementation plan within 30 days [of Apr. 3], LF 5E10 would be considered administratively transferred and decertified from Minuteman III generation requirements and transferred into caretaker status,” AFGSC said.
The mammoth, decade-long Sentinel project is to kick off with the building of fiber optic communications lines in the spring of 2027.
The New Start Treaty between Russia and the U.S. expires next February, and that may lead to a rethinking of minimum deterrence levels for the U.S. and whether multiple independent re-entry vehicles (MIRVs) will be a way forward for the ICBM force. AFGSC has operated under the minimum deterrence rubric of 400 Minuteman III operational missiles with 50 in reserve.
Air Force officials with the Sentinel program first began telling community leaders of the new silo plans at town hall meetings this spring, including two on April 1 and April 2 in Kimball, Neb., and Pine Bluffs, Wyo., respectively.
In April, the Air Force determined new Sentinel silos were necessary after tests of a mock Minuteman III silo at Vandenberg Space Force Base, Calif., showed that conversion of such silos to accommodate Sentinel would be much more complex than anticipated.
A decade ago up until the Nunn-McCurdy breach, Pentagon leaders thought that they could re-use the old Minuteman III silos–and their steel and concrete–to build the then called Ground Based Strategic Deterrent more quickly and cheaply. Yet, because of the Sentinel design’s provision for multiple warheads, countermeasures, and increased range to hit China, the missile is significantly larger than Minuteman III. The 1980s Boeing LGM-118 Peacekeeper, or MX missile, was significantly larger than Minuteman III as well–a size that led the Air Force to using canisters for Peacekeeper and a “cold launch,” compressed gas concept for the use of the missile from Minuteman III silos. The Air Force retired Peacekeeper in 2005.
“I would be quite curious to know what data supported the Air Force’s initial determination that Minuteman III silos could be reused for Sentinel, and how did they get it so wrong?” Mackenzie Knight-Boyle, a research associate with the Federation of American Scientists’ nuclear information project, wrote Wednesday in an email response to questions. “How are they just now being made aware of the challenges of refurbishing existing silos? It seems to me that these challenges – ‘asbestos, lead paint and other conditions,’ as the Air Force program executive officer for ICBMs explained” should have been foreseen, Knight-Boyle said.
AFGSC completed the Sentinel concept of operations in March.
Wednesday’s GAO report said that AFGSC has estimated that the command will need 19 percent more Sentinel missile launch officers by fiscal 2028, 10 percent more maintenance personnel by fiscal 2029 to deactivate Minuteman III silos and prepare for Sentinel activation, and five percent more security personnel by 2030. This is due, in part, to the split in the ICBM force between the two systems, Sentinel and Minuteman III.
“According to Global Strike Command officials, the transition [to Sentinel] will require an increase in personnel, to include operators, maintainers, and security forces, due to concurrent operations, deactivation, and sustainment of Minuteman III, and the deployment and sustainment of Sentinel,” GAO said in the new report. “This increase will require years of lead time to prepare these personnel,” GAO said.
To maintain nuclear deterrence, as AFGSC decommissions Minuteman III silos, DoD should consider using MIRVs for Minuteman III, GAO said.
“Global Strike Command’s 2020 Transition and Deployment Strategy presented the option to re-MIRV all or some Minuteman III ICBMs during the transition to Sentinel as desirable but acknowledged it would require a U.S. policy change,” the report said. “Global Strike Command officials emphasized they would prefer as much lead time as possible to implement any potential re-MIRV decision due to the complexity of operations and additional logistical workload required to accomplish such a requested change.”
The Air Force has said that it could sustain Minuteman III until 2050.
Exchange Monitor affiliate Defense Daily first published this article.