US and UK navies test Mk 48 torpedo launch from uncrewed submarine

The US Navy and Royal Navy launched an American Mk 48 heavyweight torpedo from the British XV Excalibur uncrewed submarine during a test in Scotland on September 13, 2026. The trial took place at the British Underwater Test & Evaluation Centre as part of Project Broadsword, approved in February 2026.

The test examined whether the American weapon could work with a British autonomous underwater vessel through compatible mechanical, electrical and software systems. Because XV Excalibur lacks conventional internal torpedo tubes, engineers mounted the approximately 3,700-pound torpedo externally beneath its hull.

Project Broadsword brought together the Department of the Navy Rapid Capabilities Office, OPNAV N97, the Royal Navy, the Defense Innovation Unit, Naval Undersea Warfare Center Keyport and industry partners. It is part of AUKUS Pillar II, which supports cooperation on advanced capabilities, including autonomy and undersea systems.

Adm. Daryl Caudle, Chief of Naval Operations, called the test “a historic first for allied undersea warfare” and said it validated a shared vision for interchangeability. Vice Adm. Robert Gaucher described it as an early step toward greater interoperability for autonomous undersea systems.

The US Navy plans to continue the work through Project CUTLASS, using Anduril’s Dive-XL platform. The follow-on effort will examine payload integration, command and control systems, and operational scenarios. Further trials will assess whether the approach can support other weapons, platforms and mission configurations.