The Air Force is to start construction this month of a prototype silo for the Sentinel LGM-35A future intercontinental ballistic missile (ICBM) by Northrop Grumman, the service said on Tuesday.
The construction is in advance of a planned Pentagon engineering and manufacturing development (EMD) recertification decision on the ballistic missile this year and a first pad-launched flight test next year, the Air Force said in a press release.
In February, “teams will break ground on a prototype launch silo at Northrop Grumman’s Promontory, Utah, site,” the service said. “This crucial effort will allow engineers to test and refine modern construction techniques, validating the new silo design before work begins in the missile fields.”
The release also said the restructuring of the Sentinel, which began after the program breached a law known as Nunn-McCurdy in January 2024 by exceeding cost projections by well over the 25% threshold, is expected to be complete by the end of 2026.
The Sentinel silos are to be new rather than refurbished Minuteman silos as the Air Force had planned, in part because of the larger Sentinel missile, but also because of environmental conditions in the silos for the current Minuteman III, including asbestos, lead paint, and tilting in a small number of silos due to variations in their concrete thickness.
The plan to build new silos “avoids the unpredictable costs and safety hazards of excavating and retrofitting 450 unique structures built over 50 years ago, and is a prime example of choosing a path that delivers capability with greater speed and less risk,” the Air Force said.
Last year, the Air Force used a former ICBM silo, Launch Facility 04, at Vandenberg Space Force Base, Calif., and a mock Minuteman III silo built in 2021 by Northrop Grumman in Promontory to inform the service’s decision to build new silos.
Rather than an ICBM test silo, the Air Force is to use a launch pad at Vandenberg for the first flight test of an unarmed LGM-35A, the service said last fall. The Air Force said on Tuesday that it plans to conduct that first flight test next year.