Mk7 reentry body

History

The Mk7 reentry body is a United States conical reentry vehicle being developed with the W93 nuclear warhead for future submarine-launched ballistic missile service. Its function is to carry the W93 warhead through atmospheric reentry toward its target.

The Mk7 forms part of the combined W93/Mk7 program managed through cooperation between the U.S. Navy's Strategic Systems Programs organization and the National Nuclear Security Administration. The combined effort is the first new U.S. nuclear warhead and reentry system program initiated in nearly four decades.

The system remains under development. It is expected to support the sea-based strategic deterrent and is planned for eventual deployment aboard ballistic-missile submarines, while the United Kingdom is also expected to use the Mk7 reentry body.

Development

Development of the W93 began in 2020, with the Mk7 being developed alongside the new warhead as its associated reentry body. The program combines U.S. Navy responsibility for the reentry system with nuclear-warhead development conducted through the National Nuclear Security Administration and its national laboratory network.

In March 2025, the W93/Mk7 weapon system completed Phase 2 of the nuclear weapons development process. This phase evaluated feasibility and refined design options. Work included an analysis of alternatives, draft military characteristics, and a draft stockpile-to-target sequence defining the physical conditions the weapon system must withstand from storage through detonation.

The program subsequently moved through Phase 2A, which further defined the design and established development and qualification planning, production requirements, and life-cycle cost estimates. In 2026, the W93/Mk7 program achieved Milestone B and entered the Engineering and Manufacturing Development phase of the Defense Acquisition System.

During Engineering and Manufacturing Development, the program is focused on completing the production design and demonstrating that the system can be manufactured in a form suitable for Navy requirements. Development is being conducted through an interagency nuclear weapons life-cycle process involving Strategic Systems Programs, the National Nuclear Security Administration, associated national laboratories, and the U.S. industrial base.

Design

The Mk7 is a cone-shaped reentry body assembly designed to contain and transport the W93 warhead during the final atmospheric portion of a submarine-launched ballistic missile trajectory. The reentry body functions as the flight vehicle that protects and carries the warhead as it returns through the atmosphere toward the target.

The Mk7 and W93 are being developed as a combined weapon and reentry system rather than as unrelated components. Publicly available program information does not provide dimensions, mass, materials, aerodynamic details, or other detailed physical specifications for the Mk7.

The Mk7 is intended for integration with the future sea-based strategic nuclear force. The same reentry body is also planned for use by the United Kingdom, continuing cooperation between the two countries in submarine-based nuclear systems.

Program status

As of September 2026, the W93/Mk7 program is in Engineering and Manufacturing Development following achievement of Milestone B. The current phase is intended to mature the production design and demonstrate producibility before later qualification and production activities.

The W93 and Mk7 are expected to begin supporting U.S. submarine-launched ballistic missile operations in the mid-2030s. Initial deployment is expected aboard Ohio-class ballistic-missile submarines, followed later by deployment as the U.S. Navy transitions to the Columbia class.

The Mk7 is not yet an operational reentry body. Its planned deployment depends on completion of development, qualification, production, and integration work.

Specifications (Mk7 reentry body)

General characteristics

• Type: Nuclear-warhead reentry body.
• Configuration: Conical reentry flight vehicle.
• Associated warhead: W93.
• Role: Carries the W93 warhead through atmospheric reentry toward its target.
• Intended weapon class: Submarine-launched ballistic missile system.
• Development country: United States.
• Program status: Engineering and Manufacturing Development as of 2026.
• Planned U.S. deployment: Ohio-class ballistic-missile submarines from the mid-2030s, followed later by Columbia-class submarines.
• Additional planned user: United Kingdom.