The cost of America’s new LGM-35A Sentinel intercontinental ballistic missile program has surged from an initial estimate of $77.7 billion to $140.9 billion. According to 19FortyFive, one of the main reasons for the dramatic increase was the mistaken assumption that the new ICBM could be integrated relatively easily into the existing Minuteman III infrastructure.
The Sentinel is being developed to replace the LGM-30G Minuteman III, the only land-based intercontinental ballistic missile currently in the US arsenal. In practice, however, the US Air Force must replace far more than the missiles themselves, with a significant portion of the infrastructure supporting the nuclear force also requiring an overhaul.
The Sentinel procurement program was originally expected to cost around $77.7 billion. The revised estimate has now reached $140.9 billion, an increase of 81%. Despite the soaring cost, the Pentagon has decided to continue the program, considering it necessary for national security.
Much of the challenge stems from the legacy of the Minuteman III. The three-stage, solid-fueled ICBM entered service in 1970. Around 400 Minuteman III missiles are currently deployed across Montana, North Dakota and Wyoming, while related infrastructure also extends into Nebraska and Colorado.
Over the decades, the Minuteman III has undergone numerous upgrades involving its propulsion systems, guidance and control equipment, electronics and warheads. Nevertheless, the system remains based on Cold War-era architecture that the US Air Force cannot maintain indefinitely.
Early planning for the Sentinel assumed that much of the existing Minuteman infrastructure could be reused for the new missile. The project eventually demonstrated that replacing one ICBM with another would not be a straightforward process.
Sentinel has different requirements for missile silo dimensions, power supplies, communications, operations and maintenance. Modern nuclear command systems also demand substantially higher levels of physical security and cybersecurity.
As a result, what began as a missile replacement program has evolved into a massive engineering and construction project. The modernization effort covers 450 launch facilities spread across five US states. A significant portion of the program’s cost is therefore tied not directly to the Sentinel missile itself, but to rebuilding silos and the infrastructure used to control and launch the weapons.
What Is the Sentinel and How Is It Different From Minuteman III?
Like its predecessor, the LGM-35A Sentinel is a three-stage, solid-fueled intercontinental ballistic missile. Its expected range is approximately 6,000 miles, or 9,656 kilometers.
Northrop Grumman is the program’s prime contractor and is responsible for the first- and second-stage propulsion systems, while Aerojet Rocketdyne is developing the third-stage motor. The missile uses modern composite motor casings designed to reduce weight while maintaining the required structural strength.
The most significant differences between Sentinel and Minuteman III, however, extend beyond their solid-fuel propulsion systems. Sentinel is expected to incorporate modern electronics, navigation, communications and command systems, as well as more advanced cybersecurity.
The program also uses a modular open-systems architecture intended to make it possible to replace individual components in the future without redesigning the entire system. This is particularly important for the US Air Force because the Sentinel is planned to remain in service until 2075.
The dramatic increase in the program’s cost therefore reflects the scale of the project facing the United States. Rather than simply replacing Minuteman III missiles with newer ICBMs, the US must rebuild a substantial part of the land-based component of its nuclear triad.
Underestimating the scale of that infrastructure work was one of the main reasons the original budget proved far removed from the current estimate. A program once expected to cost less than $80 billion is now projected to exceed $140 billion.