Mk21A Reentry Vehicle

The Mk21A Reentry Vehicle program is a key initiative within the Air Force's Ballistic Missile procurement portfolio, designed to deliver an advanced reentry vehicle (RV) for the LGM-35A Sentinel weapon system. The primary goal of the Mk21A program is to design, develop, produce, and deploy an integrated RV capable of delivering the W87-1 warhead. This capability is essential for maintaining the effectiveness and reliability of the United States' land-based nuclear deterrent, as directed by the Air Force Global Strike Command and in alignment with requirements from the Department of Energy/National Nuclear Security Administration.

The objectives of the Mk21A program include providing significant performance and security enhancements over the legacy Mk21 RV. These improvements are necessary to meet the upgraded requirements for the W87-1 warhead, ensuring both the warhead and the reentry vehicle are delivered on schedule. The Mk21A RV is engineered to satisfy the specifications outlined in the Sentinel weapon system Capability Development Document (CDD). This document emphasizes enhanced survivability, accuracy, and security features for future strategic deterrence missions.

Key technical components of the Mk21A RV include a shape-stable nose tip, high impulse transducer, arming and fuzing subsystem (AFS), aeroshell forward section, body section, rear cover, radio frequency subsystem with antennas, RV spin subsystem, in-flight disconnect cable, and other electrical cables. These elements are designed to ensure the RV's reliability during atmospheric reentry and to support the safe and effective delivery of the W87-1 warhead. The integration of these advanced subsystems reflects the program's focus on both survivability and operational effectiveness.

One specific line item within the program is the Heatshield Life of Type Buy (LOTB), executed in FY 2025. The LOTB aims to procure and process heatshield materials in advance, thereby reducing supplier risks and addressing potential vulnerabilities in the industrial base. This proactive procurement is justified by the need to ensure uninterrupted production and sustainment of critical materials, especially given the unique requirements of the Mk21A RV's reentry environment. The heatshield technology, while similar to currently fielded materials, is subject to certification under 10 USC 4252, which requires demonstration in a relevant environment prior to Milestone B approval.

In support of certification and risk reduction, the program conducted a successful flight test in the third quarter of FY 2024. Following this, a Technology Readiness Level (TRL) update was provided to the Air Force's acquisition office (SAF/AQR) in April 2025. A final decision on readiness is anticipated in the third quarter of FY 2025. These activities are critical to validating the design and manufacturing processes, ensuring the Mk21A RV meets operational and safety standards before entering full-scale production.

Funding for the Mk21A Reentry Vehicle program is allocated under Program Element 0101328F, with FY 2025 including investment primarily for non-recurring hardware costs related to heatshield material procurement. No new procurement funding is requested for FY 2026, reflecting the program's phased approach to development and acquisition. The budget also allows for addressing Diminishing Manufacturing Sources (DMS) issues, ensuring long-term sustainability and supply chain resilience for the RV's critical components.