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Safeguard the U.S. and UK relationship through the PSA and MDA

Fundamental to U.S. strategic and extended deterrence policies is the special relationship between the U.S. and the UK through the Polaris Sales Agreement (PSA) and the Mutual Defense Agreement (MDA). The PSA provides the legal mechanism through which the two countries’ defense agencies cooperate on weapon systems capabilities while reducing combined defense costs and protecting the sovereign independent responsibilities of each state for their own nuclear materials and explosive packages.

The Common Missile Compartment (CMC) represents the newest example of this partnership, designing, developing, and producing common shipboard infrastructure which improves the ease of comingling the D5 missile inventory and sets the stage to improve maintenance system consistency across the two fleets. SSP will support PEO SSBN throughout the 2020s as they oversee U.S. industry delivery of CMC components to both Navy’s for installation into their new SSBNs. While shipboard systems are improved on both COLUMBIA and DREADNOUGHT under the PSA and MDA, the UK will continue to work closely on the requirements and funding of the Trident II D5LE2 missile system as well as the Mk7 reentry system. As with COLUMBIA, the DREADNOUGHT Class SSBNs will initially carry the D5LE missile and be back fitted with D5LE2 once approved for fleet introduction. The development of the Mk7 reentry system to support the U.S. W93 warhead program is also critical to the development of a next generation nuclear warhead and reentry system for the UK.



While the UK is solely responsible for development of their sovereign nuclear package for their next generation warhead, they are critically dependent upon U.S. development of the reentry system under the PSA and MDA.

SSP will continue to nurture and safeguard this special and foundational relationship with the UK under the PSA and MDA to sustain the SBSD and CASD of today while modernizing and building flexibility, adaptability, and resiliency into SBSD 2084 and the UK’s future Continuous At Sea Deterrence.


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