US Air Force Tests Mk21A Reentry Vehicle for Future Sentinel ICBM Modernization

The US Air Force and Lockheed Martin tested the Mk21A reentry vehicle for the future Sentinel ICBM, advancing the design for enhanced nuclear deterrence.

The US Air Force and Lockheed Martin successfully conducted a flight test for the Mk21A reentry vehicle, which is being developed for the future LGM-35A Sentinel intercontinental ballistic missile (ICBM). The test aimed to evaluate the design components and technologies of the Mk21A, with data collected to inform future designs and flight tests.

Lockheed Martin, awarded a $1 billion contract for this project in October 2023, is focused on maturing the vehicle's design, including the arming and fuzing subsystems. This effort builds on Lockheed Martin's extensive experience in reentry technologies and a pioneering digital engineering approach. The company has been involved in reentry system development for over 65 years, making significant progress in modernizing strategic capabilities for the US military .

The Mk21A reentry vehicle will carry the W87-1 nuclear warhead, an upgrade from the W87 used in the current Minuteman III ICBMs. The Sentinel ICBM is set to replace the aging Minuteman III missiles starting in 2029, ensuring the US maintains a robust and modernized land-based nuclear deterrent. The contract work is expected to be completed by October 2039, with initial operational capability planned for 2030 .

In addition to this, the Air Force's broader modernization efforts include updates to air-based platforms, such as the B-52 bomber and the new B-21 Raider stealth bomber, to maintain a strong and effective nuclear triad .