U.S. and UK navies successfully launch 3,700-pound submarine-sinking torpedo from robotic drone submarine in historic first

The U.S. Navy and the British Royal Navy have jointly launched an exercise U.S. Mk 48 heavyweight torpedo from the Royal Navy’s uncrewed drone submarine, XV Excalibur, marking a historic milestone in autonomous warfare. According to an official press release, the proof-of-concept launch took place on September 13 at the British Underwater Test & Evaluation Center (BUTEC) in Scotland.

“This successful test marks a historic first for allied undersea warfare,” said Chief of Naval Operations Adm. Daryl Caudle. “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 launch was conducted under AUKUS Pillar 2, a military partnership between the United States, the United Kingdom, and Australia aimed at developing and accelerating the deployment of cutting-edge, advanced defense technologies, such as artificial intelligence, quantum computing, and autonomous underwater systems, to maintain a strategic technological edge in the Indo-Pacific region. According to the U.S. Navy, the trial validated the mechanical, electrical, and software integration of an American kinetic payload onto a British autonomous platform, proving weapon interchangeability between allied forces.

The project — designated Project Broadsword — received approval in February 2026 from the Department of the Navy Rapid Capabilities Office (DONRCO) and was executed in collaboration with OPNAV N97, the Royal Navy, the Defense Innovation Unit (DIU), Naval Undersea Warfare Center (NUWC) Keyport, and several industry partners. From approval to trials took just seven months. In a similar project, the U.S. Navy launched missiles from its first drone sailboat in August.

The Mk 48 is a heavyweight anti-submarine and anti-surface torpedo used by the U.S. Navy and several allied submarine forces. Typically launched from fully manned submarines with crews of 100 to 140 actively involved sailors, the 3,700-pound (1,680 kg) weapon is designed to sink deep-diving submarines and high-performance surface ships. Project Broadsword marks the first time the torpedo has been successfully launched from an uncrewed, autonomous robotic submarine.

The launch machine, XV Excalibur, is the British Royal Navy’s Extra-Large Uncrewed Underwater Vessel (XLUUV), designed to operate autonomously or via remote control without any crew on board. The Royal Navy successfully demonstrated the drone's capability in 2025 by controlling Excalibur in UK waters from a command center 10,000 miles away in Australia. Before the torpedo test, the vessel served as a mobile underwater laboratory for testing cutting-edge technology and future payloads. Because Excalibur lacks traditional internal torpedo tubes, engineers attached the 2-ton torpedo externally using a specialized cradle beneath its hull.

The U.S. Navy confirmed that following the success of Project Broadsword, it will “continue aggressive follow-on acceleration with Project CUTLASS,” in collaboration with its partners. “Utilizing the Anduril Dive-XL platform, the next phase will tackle advanced payload integration data, command and control architectures, and tactical employment scenarios to further mature uncrewed undersea capabilities,” the press release read.

The launch is the latest development in fast-rising autonomous warfare, where militaries deploy systems that can capture and process data and execute tasks — including the use of lethal force — with little to no human intervention. These systems include unmanned aerial, ground, and sea vehicles; weapons; robots; and AI-driven command-and-control systems. Earlier this month, an autonomous NATO strike drone used Nvidia Jetson Orin Nano to independently pick and bomb targets.

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