The United States is developing the LGM‑35A Sentinel intercontinental ballistic missile (ICBM) to replace the ageing Minuteman III system that has formed a core element of the country’s nuclear deterrent for more than five decades. Designed with a new solid‑fuel propulsion system, modern digital architecture and upgraded launch infrastructure, the programme aims to sustain the credibility of the US land‑based nuclear force into the 2030s. However, rising programme costs, software delays and schedule pressures continue to present significant management challenges.
According to information published by the original report, the Sentinel missile is expected to fully replace the Minuteman III fleet in the early 2030s. The programme involves not only a new missile but also a large‑scale overhaul of launch infrastructure, command systems and associated support facilities.
New missile architecture and extended range
Sentinel is a three‑stage intercontinental ballistic missile powered by solid rocket motors. Each stage has undergone large‑scale testing, with the first stage completing qualification testing in March 2025 and the second stage in July 2025. The missile also incorporates a post‑boost propulsion system designed to improve targeting precision by adjusting the trajectory of re‑entry vehicles after boost phase.
The missile is larger than its predecessor, enabling a longer operational reach and improved accuracy. Current projections suggest a range exceeding 13,000 kilometres. Sentinel will carry the updated W87‑1 nuclear warhead paired with the Mk21A re‑entry vehicle developed by Lockheed Martin.
The system is also expected to retain the capability to deploy multiple independently targetable re‑entry vehicles (MIRV), although the precise number of warheads has not been publicly disclosed.
Digital command architecture and new silo infrastructure
Beyond the missile itself, the Sentinel programme includes a comprehensive modernisation of the supporting command and control framework. The system will integrate with the United States’ nuclear command, control and communications (NC3) network through a flexible digital architecture designed to adapt to evolving operational environments.
A significant component of the programme involves replacing existing launch facilities. Rather than refurbishing the approximately 450 Minuteman III silos currently in operation, the US Air Force plans to construct new modular silos designed for repeatable construction and improved security.
A full‑scale prototype silo began construction in March 2026 at Promontory, Utah. The project uses a utility‑corridor construction approach intended to streamline installation of infrastructure and reduce overall costs and construction time. The design also allows greater use of federally owned land to minimise the need for acquiring private property.
Programme restructuring and development milestones
Programme leaders have emphasised the goal of delivering enhanced capability more quickly through a combination of digital engineering techniques and an incremental testing approach described as “crawl‑walk‑run”. This method is intended to reduce technical risk before the system enters full production.
Following a restructuring triggered by a breach of the US Nunn‑McCurdy cost threshold, decision‑making authority has been streamlined through the Direct Reporting Program Manager structure. Officials expect the programme to reach the Milestone B acquisition decision by the end of 2026, with the first test flight targeted for 2027.
Rising costs and software development concerns
Despite technical progress, the Sentinel programme faces notable financial and schedule pressures. After restructuring, total programme costs are estimated at approximately US$141 billion, significantly higher than the earlier estimate of US$77.7 billion. The US Government Accountability Office has warned that costs could continue to rise if oversight and programme controls are not strengthened.
Software development has also progressed more slowly than expected. Some design metrics and delivery timelines remain incomplete, raising concerns about the ability of the prime contractor, Northrop Grumman, to deliver critical software systems on schedule.
The first flight test has already been delayed by several years. Updated projections referenced by oversight bodies place the test closer to 2028, while the missile’s initial operational capability is now expected in the early 2030s.
Balancing modernisation with programme risk
The Sentinel system represents a major technological update for the United States’ land‑based nuclear deterrent, combining modern propulsion, improved targeting precision and a redesigned launch infrastructure intended to increase survivability and operational flexibility.
However, the scale of the programme introduces complex risks. Construction of hundreds of new silos requires additional environmental assessments, while integrating the missile, warhead, re‑entry vehicle and NC3 network presents significant technical challenges. Analysts warn that careful programme management will be essential to avoid capability gaps during the transition from Minuteman III to Sentinel.
