US Army Secures Future of Its Intercontinental Strike Force with LGM-35A Sentinel Missile Test.

As part of the modernization of the land-based leg of the U.S. nuclear deterrent, the U.S. Air Force and Northrop Grumman have reached a key milestone with the successful full-scale qualification test of the second-stage solid rocket motor of the LGM-35A Sentinel intercontinental ballistic missile. Conducted on July 20, 2025, by the 717th Test Squadron at the Arnold Engineering Development Complex (AEDC), located at Arnold Air Force Base in Tennessee, the test marks an important step in the program to replace the Minuteman III system, which has been in service for over fifty years.
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Northrop Grumman and the U.S. Air Force tested a stage-two rocket motor for the Sentinel missile. (Rendered photo of the stage two rocket motor (Picture source: Northrop Grumman)

The LGM-35A Sentinel, initially known as the Ground-Based Strategic Deterrent (GBSD) during its early development phases, represents the technological renewal of the most responsive component of the U.S. nuclear triad. It is intended to replace the 400 Minuteman III missiles currently operational in silos at F.E. Warren (Wyoming), Malmstrom (Montana), and Minot (North Dakota) Air Force Bases. Although some subsystems of the Minuteman have undergone updates, much of the system's core infrastructure still dates back to the 1970s. The Sentinel program aims to modernize the U.S. strategic capabilities without altering the number of nuclear missiles maintained on alert.

The July 20 test, conducted in a vacuum chamber simulating high-altitude conditions, provided essential data on thrust, burn profile, and the performance of the thrust vector control system. These parameters are necessary to validate the accuracy and reliability of the digital models developed for the Sentinel program, which is based on a digital engineering approach. According to Brigadier General William S. Rogers, Director of the ICBM Systems Directorate within the Air Force Nuclear Weapons Center (AFNWC), the test is not limited to hardware validation but is also intended to confirm the integrity of the program's digital architecture, including the development timeline and operational readiness.

The tested motor corresponds to the second of the Sentinel missile's three stages. It is part of a series of tests designed to validate the motor’s design and confirm predicted performance through digital simulation. Data collected during the test will help optimize design parameters and reduce technical risk as the program moves closer to production. This test follows the first-stage motor test conducted in March 2025 at Northrop Grumman’s Promontory site in Utah, which had confirmed alignment between physical performance and digital predictions.

In parallel with missile development, existing Minuteman III facilities will undergo modernization or replacement, including launch silos, alert facilities, communication systems, and support infrastructure. Maintenance, training, storage, and testing activities will also take place at other key locations such as Hill Air Force Base (Utah), the Utah Test and Training Range, Camp Guernsey (Wyoming), and Camp Navajo (Arizona). The Sentinel program does not involve the production or disposal of nuclear materials.

The Sentinel’s development strategy relies on model-based systems engineering, enabling engineers to simulate system behavior, improve performance prediction accuracy, and reduce reliance on costly hardware prototypes. The U.S. Air Force and Northrop Grumman will continue qualification testing of the second stage throughout the year, with additional tests planned under various environmental conditions to verify the system’s resilience.

The successful test of July 20 confirms the steady progress of the Sentinel program, a central component in the ongoing renewal of the United States’ land-based nuclear deterrent. This next-generation missile, supported by a modernized infrastructure, is intended to ensure strategic reliability for the decades ahead while maintaining a deployment configuration consistent with current national defense commitments.