The Royal Navy successfully launched a U.S. Navy Mk 48 Heavyweight Torpedo from a British Excalibur uncrewed underwater vehicle (UUV) on Sept. 13 at the British Underwater Test & Evaluation Centre in Scotland, according to a U.S. Navy press release reported by Defense News and Navy Times.
The test marks a significant step for AUKUS Pillar 2, the trilateral agreement between the U.S., U.K., and Australia aimed at enabling UUV payload systems that can be used across each country’s vehicles, as outlined in a May 2026 agreement.
While described as a proof of concept, the test “validated the mechanical, electrical, and software integration of a U.S. kinetic payload onto an allied autonomous vessel, proving that allied forces can rapidly achieve weapon interchangeability,” the Navy press release stated.
Adm. Daryl Caudle, Chief of Naval Operations, called the cooperation “a historic first for allied undersea warfare.” He added: “Proving that we can seamlessly launch a U.S. heavyweight torpedo from a Royal Navy autonomous underwater vehicle validates our shared vision for true interchangeability. By integrating weapons, payloads, and mission architectures across allied platforms, we are increasing the flexibility, scale, and combat power of our combined forces and ensuring they are ready to meet the strategic demands of tomorrow.”
The Mk 48 is the U.S. Navy’s standard heavyweight torpedo, measuring 19 feet long with a 21-inch diameter. The latest version, the MOD 7, was developed under a Joint Development Program with the Royal Australian Navy and is optimized for “traditional and emerging missions,” according to the Navy.
The Excalibur, unveiled in May 2025, is the Royal Navy’s first uncrewed submarine. Video of the event shows the torpedo was placed under the nearly 40-foot submersible and launched from a cradle attached to the hull.
According to the U.K. publication Navy Lookout, “Excalibur has no torpedo tubes, but a large central payload bay with doors at the top and bottom. However, the Mk 48 torpedo… is too long to fit in the standard central payload bay.”
The successful deployment is just the first step under AUKUS Pillar 2, according to the sources.
Sources: Defense News · Navy Times