ICBM Payload System Features
The payload is the front end of an intercontinental ballistic missile. It consists of the re-entry vehicle, which protects the warhead during its flight through space, and the fuze, which is a critical device for weapon safety and control. To ensure the nation's nuclear deterrent remains credible, these components must be continuously modernized. The Sentinel will initially be deployed with the existing Mk21 re-entry vehicle before being upgraded with the next-generation Mk21A.

The Air Force Nuclear Weapons Center manages the following modernization programs to ensure these systems remain safe and effective:

ICBM Fuze Modernization
The Air Force is currently replacing older fuzes in the Minuteman III Mk21 re-entry vehicle with modern, more reliable components. This new, proven system is a direct replacement for the legacy fuze and is designed to be used on both the Minuteman III and the new Sentinel, ensuring a safe and reliable capability for decades to come.

Mark21A Re-entry Vehicle
The Mark21A is the next-generation re-entry vehicle being developed by Lockheed Martin for the new LGM-35A Sentinel ICBM. This technically advanced system will house the warhead, protecting it as it travels through space and re-enters the atmosphere. The program is making significant progress and is on schedule. To ensure the successful and timely delivery of the Mk21A, the Air Force has focused its resources on this program.