The U.S. Navy and Royal Navy have completed a historic first: launching a 3,700-pound Mk 48 heavyweight torpedo from an uncrewed, autonomous submarine. The proof-of-concept test occurred on September 13 at the British Underwater Test & Evaluation Center in Scotland, as part of the AUKUS Pillar 2 partnership focused on advanced defense technologies. The trial validated the mechanical, electrical, and software integration needed to put an American kinetic payload on a British autonomous platform, demonstrating weapon interchangeability between allied forces.
The launch vehicle was XV Excalibur, the Royal Navy's Extra-Large Uncrewed Underwater Vessel, which normally operates without any crew aboard. Because Excalibur has no traditional torpedo tubes, engineers attached the two-ton weapon externally using a specialized cradle beneath the hull. The program, designated Project Broadsword, received approval in February 2026 from the Department of the Navy Rapid Capabilities Office and was executed with partners including the Defense Innovation Unit and Naval Undersea Warfare Center Keyport, reaching trials in just seven months.
Following the success, the U.S. Navy says it will continue with Project CUTLASS, which will use the Anduril Dive-XL platform to focus on advanced payload integration, command-and-control architectures, and tactical employment scenarios. The test adds to a broader push in autonomous warfare, where militaries are increasingly fielding systems that can execute tasks with minimal human intervention. The single source reports no dissenting views or competing accounts of the event. (Note: The original article appeared on Tom's Hardware, not a defense-specific outlet.)