Artist rendering of the LGM-35A intercontinental ballistic missile designed to carry nuclear warheads and launch from 450 new underground hardened silos. (U.S. Air Force)
The Air Force has broken ground in Utah on the prototype for 450 launch silos to be built for its next-generation intercontinental ballistic missile.
The LGM-35A Sentinel will replace the Cold War-era LGM-30G Minuteman III. The nearly $141 billion program is expected to stretch into the second half of the 21st century.
The silo prototype near Promontory, Utah, will be built using digital designs in partnership with missile maker Northrop Grumman and construction company Bechtel Corp., the Air Force said.
The Sentinel project calls for building a network of new silos rather than placing the new missiles inside the hundreds of existing Minuteman III silos.
“The shift to building new silos — rather than refurbishing legacy Minuteman III infrastructure — preserves uninterrupted alert coverage while enabling a modern, adaptable architecture,” the Air Force said in a March 27 statement.
The Sentinel is planned to serve as the land-based leg of the United States’ nuclear triad, which also includes manned bombers and submarine-launched Trident missiles.
The U.S. is in the early stages of modernizing all three legs of the triad, which is designed for nuclear war.
The Navy is developing the Columbia-class nuclear-powered submarine to replace Cold War-era Ohio-class “boomer” missile boats. Both the Columbia and Ohio classes are currently designed to fire the nuclear-tipped Trident II D5 missile.
Leadership from the U.S. Air Force, Northrop Grumman and Bechtel break ground for the LGM-35A Sentinel intercontinental ballistic missile launch silo prototype in Promontory, Utah. The Air Force plans to create 450 new silos to replace the legacy Minuteman III system. (U.S. Air Force)
The Air Force plans for the new B-21 Raider manned bomber to replace the B-1 Lancer and B-2 Spirit bombers. The Air Force has said it will retain some B-52H Stratofortress bombers as nuclear weapon launch platforms.
The Air Force said the prototype silo would help validate plans for “a modular, repeatable” construction of the new silos, which would potentially shorten the timeline of fielding the Sentinel and reduce costs, which have ballooned since the replacement program for the Minuteman III was announced in 2016.
“We are accelerating delivery while ensuring the system is sustainable and ready for airmen to operate for decades,” said U.S. Air Force Gen. Dale R. White, director for critical major weapons systems at the Defense Department, in the Air Force statement.
Construction is also underway on a new 90th Missile Wing Command Center at F.E. Warren Air Force Base, Wyo., a key ICBM control installation.
The Pentagon says the Sentinel has passed key test-firing benchmarks. The service plans a 2027 flight test of the Sentinel, with the first operational missiles ready by the early 2030s. The Minuteman III would be phased out over several decades.
“We are executing a disciplined acquisition strategy to deliver a fully integrated, operational weapon system on schedule,” said Brig. Gen. William S. Rogers, Air Force program executive officer for intercontinental ballistic missiles.
The Sentinel program took a step backward in 2024 when the Air Force told Congress the projected cost of the new missile had grown 81% from its original estimate of $78 billion. The increase triggered a congressionally mandated “Nunn-McCurdy” breach that required the Pentagon to justify continuing the program and restructure its costs.
