The U.S. Navy and Britain's Royal Navy have test-fired an exercise Mk 48 heavyweight torpedo from the uncrewed submarine XV Excalibur, demonstrating that an American weapon can operate from a British autonomous platform.
The proof-of-concept launch took place September 13 at the British Underwater Test and Evaluation Center in Scotland, according to Tom's Hardware and a linked U.S. Navy release. The test was conducted under AUKUS Pillar 2, the technology partnership among the United States, United Kingdom and Australia.
An external weapon on an uncrewed vessel
XV Excalibur is the Royal Navy's Extra-Large Uncrewed Underwater Vessel. It can operate autonomously or by remote control, with no crew aboard. Because it lacks conventional internal torpedo tubes, engineers mounted the roughly 3,700-pound weapon to a specialized cradle under the hull.
The Mk 48 is designed for attacks on deep-diving submarines and high-performance surface ships. It is normally launched from crewed submarines. The trial validated the mechanical, electrical and software connections needed to carry and fire it from the British drone.
Project Broadsword received approval from the Department of the Navy Rapid Capabilities Office in February 2026 and reached the trial in seven months. The work included the U.S. Navy, Royal Navy, Defense Innovation Unit, Naval Undersea Warfare Center Keyport and industry partners.
The next phase shifts to integration
The Navy says the follow-on effort, Project CUTLASS, will use Anduril's Dive-XL platform to test more advanced payload integration, command-and-control systems and tactical scenarios.
A successful launch proves compatibility in a controlled trial, not a fully fielded autonomous weapons program. The next work will determine how the system is commanded, how payload data moves between allied platforms and how an uncrewed submarine would be used operationally.
