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U.S. and U.K. navies fire a Mk 48 torpedo from an uncrewed submarine for the first time

A British Excalibur drone submarine launched a U.S. heavyweight torpedo in a Sept. 13 test in Scotland that the Navy said went from approval to execution in under seven months.

Motion Media News Staff

Sep 22, 2026

2 minutes

Sailors in cold-weather gear guide a long Mk 48 torpedo suspended from a crane beside a submarine during snowfall.

Photo: U.S. Navy / John Narewski (Public domain), via Wikimedia Commons (source)

The American and British navies have launched a U.S. Mk 48 heavyweight torpedo from a British uncrewed underwater vehicle, a first for both services, the U.S. Navy announced on Tuesday, Sept. 22, according to Defense News and The War Zone.

The proof-of-concept launch took place on Sept. 13 at the British Underwater Test and Evaluation Centre, a range in Scotland. The torpedo, an exercise round, was carried beneath the Royal Navy's Excalibur, a submersible drone of nearly 40 feet that the U.K. unveiled in 2025 as its first uncrewed submarine.

Excalibur has an internal payload bay, but the Mk 48 is about 19 feet long and 21 inches in diameter and does not fit inside it, both outlets reported. For the test, the weapon was slung under the hull and released from a cradle.

The Navy said the launch "validated the mechanical, electrical, and software integration of a U.S. kinetic payload onto an allied autonomous vessel." According to The War Zone, the service said the Navy's Rapid Capabilities Office signed off on the project in February 2026 and it was completed in less than seven months. Staff from the Pentagon's Defense Innovation Unit and the Keyport, Wash., division of the Naval Undersea Warfare Center also took part.

Chief of Naval Operations Adm. Daryl Caudle called the test "a historic first for allied undersea warfare." He said it showed the two navies could achieve "true interchangeability" of weapons across allied platforms.

Vice Adm. Robert Gaucher, the Navy's director of submarine programs, described the launch as "an important early step in developing lethality in our undersea autonomous systems."

AUKUS Pillar 2

The work falls under Pillar 2 of the AUKUS partnership among Australia, the United Kingdom and the United States, which covers advanced technology such as autonomy and uncrewed platforms. Pillar 1 centers on helping Australia field nuclear-powered submarines.

The Navy has not said how Excalibur was controlled during the launch or whether the torpedo was fired at a target. The War Zone said it had asked the service for those details.

What's next

According to Defense News, the Navy's release describes a follow-on effort called Project CUTLASS. It will use Anduril's Dive-XL uncrewed submarine to work on payload integration, command-and-control designs and tactics for drone submarines. The Navy has not published a timeline for that work.