Report details US-UK ties in Dreadnought submarine program

The Royal Navy’s Dreadnought-class submarines share a missile compartment design, a nuclear propulsion technology exchange, and the same missile as the U.S. Navy’s Columbia class, according to a Congressional Research Service assessment cited by the UK Defence Journal.

Both submarine programs are now past the point of no return. All four British boats, HMS Dreadnought, Valiant, Warspite and King George VI, are under construction at BAE Systems in Barrow-in-Furness. The UK government confirmed £8.4 billion ($11.44 billion) for Delivery Phase 4 on July 30, 2026, funding meant to carry the lead boat through sea trials and into service in the early 2030s. On the American side, the lead Columbia-class boat, District of Columbia, was about 65 percent complete when the Navy’s program executive officer for strategic submarines spoke at the WEST conference in February 2026. Delivery estimates range from late 2028, according to General Dynamics, to March 2029, according to the Navy’s own budget documents.

The clearest link between the two classes runs through the Common Missile Compartment, the section of each boat that houses the launch tubes. Both navies are building to the same general design, with a modular layout that accommodates a difference in tube count: sixteen on the American boats, twelve on the British ones. Of the UK’s twelve tubes, current plans call for eight to carry missiles. Britain provided funding for the compartment’s design, including a large share of the initial money.

Naval Reactors, the joint Department of Energy and Department of the Navy organization responsible for American naval nuclear propulsion, runs a technical exchange with the UK Ministry of Defence under the 1958 Mutual Defence Agreement.

“Under this agreement, Naval Reactors is providing the UK Ministry of Defence with US naval nuclear propulsion technology to facilitate development of the naval nuclear propulsion plant for the UK’s next generation SUCCESSOR ballistic missile submarine,” the U.S. Navy said in a statement to congressional researchers.

A British-based office of around forty American personnel provides full-time engineering support under that arrangement, work that the Ministry of Defence reimburses. Reporting on the design concept has described the Dreadnought plant as based on an American design while incorporating next-generation British reactor technology in the form of the PWR3 reactor, which Rolls-Royce is building at its Derby facility.

The Dreadnought boats, like the Vanguard-class submarines they are replacing, are built to fire the Lockheed Trident II D-5, the same submarine-launched ballistic missile carried aboard the Columbia class, a shared missile system that has underpinned UK-U.S. submarine cooperation for decades, predating both current construction programs.

The Dreadnought class will displace roughly 17,200 tons and run about 153.6 m (504 feet) long, similar in scale to the Columbia-class boats being built at General Dynamics Electric Boat’s Groton, Connecticut facility. The UK’s Defence Nuclear Enterprise, which oversees the Dreadnought program alongside submarine maintenance work, currently supports around 47,000 jobs and works with more than 6,000 UK-based suppliers, according to the government’s July funding announcement.