KORTHOS / ECOSYSTEM / PRODUCT

XV Excalibur / CETUS

About

About XV Excalibur / CETUS

XV Excalibur is a 12 m extra-large uncrewed underwater vehicle built by MSubs for the Royal Navy under Project CETUS. The battery-powered submarine is an experimental platform for autonomous operations, advanced sensors and modular payloads. It supports investigation of anti-submarine warfare, intelligence and surveillance, seabed operations and integration with crewed vessels.

The Royal Navy uses Excalibur to evaluate large underwater systems through an experimentation programme, with MSubs providing the vehicle and engineering support. Internal volume and external interfaces allow different payloads and autonomy systems to be trialled. The vessel was handed over after acceptance trials in December 2025. Its development and trials programme is intended to establish the military utility of larger autonomous underwater vehicles and inform future naval use of uncrewed systems.

Capabilities

Source-backed capabilities

  • Capability areas: Autonomous navigation
  • Workflows: Marine autonomy workflow
  • Remote and shared control

    Pilot - 2025-12-11 - Control the submerged vessel in UK waters from an operating centre in Australia. - environment: UK waters, with remote operators in Australia

    Source
  • Autonomous undersea missions

    Claimed - Provide an underwater testbed for autonomous operation and modular experimental payloads. - environment: Royal Navy underwater experimentation

    Source

Operations

  • Deliveries

    1 XV Excalibur XLUUV delivered - 2025-12-11 - Royal Navy - uncrewed underwater vehicle test and evaluation - The MSubs-built XV Excalibur extra-large uncrewed underwater vehicle was handed over to the Royal Navy after acceptance trials.

    Source

Observed use

Exact-product configurations are shown without inferring supply, purchase, customer status, standard fit, deployment or partnership.

  • Mk48 Mod 4 inert recoverable torpedo

    2026-09-13 - Evaluation - Tested With - Physical - XV Excalibur fired and controlled an inert, recoverable Mk48 Mod 4 torpedo during an AUKUS evaluation trial.

    Source

Resources

Curated durable documents and official technical references.

Timeline

  • MSubs XV Excalibur launches Mk 48 torpedo in AUKUS trial

    2026-09-13 - Demonstration - Project Broadsword and Trial Iron tested integration of a US kinetic payload on a UK uncrewed vessel. The trial validated mechanical, electrical and software integration, rather than autonomous target selection. Follow-on Project Cutlass work will use Anduril Dive-XL for payload and command-and-control development.

    Source
  • MSubs receives UK SDA trial contract for CETUS XLUUV

    2026-06-26 - Contract Award - The work covers underwater-autonomy risk reduction and payload testing. MSubs' proprietary knowledge of the vehicle was the stated basis for direct award. The notice estimates a contract period ending on May 1, 2028.

    Source
  • MSubs-built XV Excalibur handed over to Royal Navy

    2025-12-11 - Production Milestone - The 12 m vessel was developed under Project CETUS with the Submarine Delivery Agency. Earlier trials included remote control from Australia while the vessel remained in UK waters. A quantum optical atomic clock from Infleqtion had also been trialled aboard the vehicle.

    Source

Context

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