The Royal Navy successfully launched a U.S. Navy Mk 48 Heavyweight Torpedo from a British Excalibur uncrewed underwater vehicle, or UUV, marking a significant step toward allied operational fleets of uncrewed vehicles.
The successful Sept. 13 launch at the British Underwater Test & Evaluation Centre in Scotland highlights a major operational achievement for AUKUS Pillar 2 — a multilateral agreement between the U.S., U.K. and Australia to enable Uncrewed Undersea Vehicle payload systems that can be used across each country’s UUVs, according to the May 2026 agreement.
While still just a proof of concept, the successful test, according to the Navy press release, “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 allied cooperation and testing marks “a historic first for allied undersea warfare,” said Adm. Daryl Caudle, Chief of Naval Operations. “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 latest version of the Mk 48, the MOD 7, a result of a Joint Development Program with the Royal Australian Navy, is optimized for both “traditional and emerging missions, according to the Navy, while the Excalibur, unveiled in May 2025, is the Royal Navy’s first uncrewed submarine.
From video of the event, it appears that the Mk 48 torpedo was placed under the nearly 40-foot British submersible and launched from a cradle attached to the hull of the UUV.
The Mk 48 torpedo, the U.S. Navy’s standard heavyweight torpedo, stands at 19 feet long with a 21-inch diameter.
According to the U.K.’s 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.”
With close coordination between the two navies, it is conceivable that future UUVs will deploy sophisticated weapon launch arrangements suitable for both British and American-made technologies.
The successful deployment of the heavyweight torpedo is just the first step under AUKUS Pillar 2.
This proof of concept is just the first step, however, as the U.S. and Royal Navy continue an aggressive “follow-on acceleration with Project CUTLASS” that will utilize the Anduril Dive-XL platform and tackle “advanced payload integration data, command and control architectures, and tactical employment scenarios to further mature uncrewed undersea capabilities,” per the release.
Claire Barrett is an editor and military history correspondent for Military Times. She holds a master’s degree in military history from King’s College, London, and is also a World War II researcher with an unparalleled affinity for Sir Winston Churchill and Michigan football.