Sentinel Storage Framework Prototype
Northrop Grumman is building a silo for the US Air Force to house its next-generation LGM-35A Sentinel nuclear missile – which will replace the Cold War-era Minuteman III.
The US nuclear deterrence strategy is based on three pillars: a bomber force, a submarine missile force, and a land-based missile force.
As , since 1970, land-based deterrence has consisted primarily of a fleet of 550 LGM-30 Minuteman III missiles, 400 of which – each carrying a single warhead – remain in active service in 450 silos spread across Wyoming, North Dakota and Montana. However, they are all old enough to the point where reliability and maintenance are becoming serious issues.
The current plan is to replace the Minuteman with the new missile Sentinel from Northrop Grumman, which is an 18-meter-tall, three-stage solid-fuel rocket with a liquid-fuel propulsion module for precision targeting of the 475-kiloton warhead. The current plan is to build 400 of these missiles for deployment, plus an additional 234 missiles for spare parts and flight testing – says the same magazine.
However, this raises the question of where to place the Sentinel.
The old silos are all custom made using cast-in-place reinforced concrete. Its electronics rely on analogue systems with hardwired connections, meaning any upgrades require major structural changes. Communications are based on copper cables and voice-quality telephone lines, HVAC systems make facilities prone to moisture, and layouts are often cramped, making repairs difficult.
That would be bad enough, but many of the silos are also deteriorating, and the Sentinel is larger than the Minuteman, making the fit a bit tight.
New structure under construction
All of this means that upgrading old silos would have been more problematic than building new ones. Therefore, Northrop Grumman and Bechtel were contracted to develop a , for which the U.S. Air Force broke ground on March 27, 2026 in Promontory, Utah.
Unlike previous silos, the new Sentinel silo is standardized, modular, faster to build and easier to upgrade.
Modularity is found throughout the installation, allowing for faster repairs and easier modifications. Electronics are now software-defined, with a digital framework to support modular electronics.
Communications are ensured by a fiber optic network reinforced with high bandwidth connections, the environmental control system reflects half a century of improvements and the general layout is much more ergonomic, allowing faster access to equipment.
On top of all this, the silo uses plug-and-play mechanical and electrical systems and the entire design is a physical version of its digital twin that allows engineers to track each component from manufacturing to installation, ensuring accurate configuration management for all silos.
According to the Air Force, the 450 new silos will be built on the same land as the existing ones.
According to New Atlas, the incredible Sentinel will have completed firing tests of all phases and the flight tests are scheduled for 2027followed by the capacity initial operational in the early 2030s.
