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UK Uncrewed Submarine Fires Heavyweight Torpedo in Historic AUKUS Trial
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First Torpedo Launch from an Uncrewed Undersea Vessel
The Royal Navy conducted a live-fire test in the week of 16 September 2026, launching a Mk 48 Mod 7 CBASS heavyweight torpedo from the experimental XLUUV XV Excalibur. The launch took place in UK waters, likely from the British Underwater Test and Evaluation Centre (BUTEC) near Kyle of Lochalsh. The torpedo, a US-Australia joint development, was fired from the 12-metre, 19-tonne autonomous submarine built by MSubs in Plymouth and remotely operated from an Australian control centre over 16,000 km away.
Background & Context
The test is part of the AUKUS partnership’s heavyweight torpedo programme. Project CETUS produced Excalibur as a demonstrator for underwater autonomy and crew-uncrewed integration. During Exercise Talisman Sabre in July 2025, an Australian centre successfully controlled Excalibur in UK waters, establishing the “Maritime Big Play” interoperability framework used in the current trial.
Key Figures & Groups
- XV Excalibur – 12-metre XLUUV, 19 tonnes, built by MSubs.
- Mk 48 Mod 7 CBASS torpedo – US-Australia joint heavyweight torpedo with acoustic homing and optional wire guidance.
- UK Ministry of Defence – announced the test.
- Sidharth Kaushal – senior research fellow at RUSI, commentator on the test’s implications.
Timeline
- May 2025 – Excalibur named at Devonport.
- July 2025 – Remote operation from Australia during Exercise Talisman Sabre.
- 16 September 2026 – Excalibur photographed at Kyle of Lochalsh quay.
- Week of 16 September 2026 – Live-fire torpedo test conducted.
Data & Statistics
- Torpedo length: 5.8 m, exceeding Excalibur’s standard payload bay; launch likely used a temporary cradle attached to the hull’s underside.
- Excalibur dimensions: 12 m length, 2 m beam, 19 tonnes displacement.
- Mk 48 family: engages submarines and surface ships, combining acoustic homing with optional wire guidance.
Official Statements & Responses
The Royal Navy framed the firing as a demonstration of a weapon-carrying role for an uncrewed platform, noting that it does not yet establish an operational capability or autonomous decision-making.
Why It Matters
Integrating a heavyweight torpedo with an XLUUV expands the Royal Navy’s strike options beyond traditional submarine launch platforms, enhancing flexibility in contested maritime environments. The remote-control element showcases interoperability between UK and Australian command structures, reinforcing AUKUS’s goal of shared undersea capabilities.
On-the-Ground Reports
Photographs taken on 16 September 2026 show XV Excalibur moored at the Kyle of Lochalsh quay, indicating the trial likely occurred at the adjacent British Underwater Test and Evaluation Centre. The facility, operated by QinetiQ for the Ministry of Defence, provides real-time three-dimensional tracking of vessels, weapons and targets.
Conflicting Reports & Gaps
Public sources have not disclosed the precise launch location within UK waters or the exact mechanism used to accommodate the 5.8 m torpedo on Excalibur’s hull. Analysts infer a temporary cradle was employed, but official confirmation is absent.