UK and US Test-Fire Torpedo from Uncrewed Submarine in AUKUS Trial

The UK and US have successfully test-fired a US torpedo from an uncrewed underwater vessel, marking a significant milestone in maritime security as part of the AUKUS security partnership. This event took place last week off the coast of Scotland, with the uncrewed submarine Excalibur launching a Mk 48 heavyweight torpedo.

New Uncrewed Submarine Technology

Excalibur is an experimental vessel built by Plymouth-based MSubs under the three-year-long Project Cetus. This extra-large uncrewed underwater vehicle (XLUUV) is 12 meters long and displaces 19 tonnes, making it capable of carrying advanced payloads for various military operations. The firing took place from the British Underwater Test & Evaluation Centre in Scotland.

Operational Achievements

The live test was conducted under Project Broadsword and Trial Iron as part of AUKUS Pillar 2, which focuses on developing advanced undersea capabilities. According to the UK government, this trial validated the mechanical, electrical, and software integration of a US kinetic payload onto an allied autonomous vessel. The Mk 48 heavyweight torpedo was jointly developed by the US and Australia, designed for engaging surface ships and deep-diving submarines.

Partnership and Global Security

This test firing is part of the broader AUKUS security partnership between the UK, the US, and Australia. The agreement includes cooperation on nuclear-powered submarines and advanced undersea capabilities, such as autonomous vehicles like Excalibur. The Royal Navy has described Excalibur as a test platform for developing experience with underwater autonomy and modular payloads, while informing future operations involving crewed and uncrewed systems.

Technical Details of the Test

The torpedo was launched from XV Excalibur during Exercise Talisman Sabre in July 2025. In that earlier trial, a remote operations center in Australia controlled the vessel while it operated in UK waters, over 10,000 miles away. The latest test moved the program from remote control and interoperability work into testing a weapons payload. The Royal Navy has stated that weapon release from future uncrewed systems will retain human authorisation.

What This Means for Operators

The successful firing of the Mk 48 heavyweight torpedo from an uncrewed submarine demonstrates significant advancements in autonomous naval technology. For operators, this could mean enhanced capabilities in anti-submarine warfare and surface ship engagement. The integration of such systems into operational fleets may lead to more flexible and responsive maritime security operations, reducing dependency on human crews for certain tasks.