MSubs
About
About MSubs
MSubs is a Plymouth-based builder of crewed and uncrewed underwater vehicles for defence, research and offshore work. Its engineering covers pressure hulls, propulsion, electrical and electronic systems, navigation, assembly, trials and operational support. Large uncrewed designs place major systems inside a pressure hull, drawing on the company's crewed-submersible engineering. Submergence Group LLC holds at least 75% of the shares in M Subs Limited, according to the current UK register.
The portfolio includes S201, a rapid-prototyping underwater vehicle, and XV Excalibur, built under Project CETUS for Royal Navy experimentation. Excalibur provides a battery-powered testbed for autonomy, sensors and modular payloads, with engineering support extending into sea trials and evaluation. MSubs also works on crewed specialist submersibles and publishes separate surface and underwater vehicle offerings.
Products
Operations
Output & shipments
- Deliveries
2025-12-11 - The MSubs-built XV Excalibur extra-large uncrewed underwater vehicle was handed over to the Royal Navy after acceptance trials. - XV Excalibur
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Orders & commitments
- Order / commitment
2020-03-05 - MSubs received an initial GBP 1 million DASA contract to build an extra-large autonomous test submarine for the Royal Navy. - Royal Navy XLUUV test submarine program
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Observed use
- XV Excalibur / CETUS with Mk48 Mod 4 inert recoverable torpedo
2026-09-13 - Evaluation - Tested With - XV Excalibur fired and controlled an inert, recoverable Mk48 Mod 4 torpedo during an AUKUS evaluation trial.
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Supply
Supply chain relationships
- Royal Navy
Outbound - Robot Platform - MSubs built XV Excalibur, the autonomous submarine handed over to the Royal Navy for sea trials
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Timeline
Events
- 2026-09-13 - Demonstration - MSubs XV Excalibur launches Mk 48 torpedo in AUKUS trial
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 - 2026-06-26 - Contract Award - MSubs receives UK SDA trial contract for CETUS XLUUV
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 - 2025-12-11 - Production Milestone - MSubs-built XV Excalibur handed over to Royal Navy
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 - 2025-12-03 - Partnership - Li-S Energy and MSubs launch UUV battery-testing collaboration
MSubs will provide a specialised pressure-test chamber for trials at Li-S Energy's Geelong facility. The initial programme covers submarine-depth pressure and endurance testing designed to simulate multi-day deployments. Only if the trials succeed will the parties evaluate Li-S batteries as propulsion power sources in current or future MSubs platforms.
Source - 2022-03-08 - Partnership - MSubs and Sonardyne advance autonomous naval-platform capabilities
The MoU covers integration and evaluation of Sonardyne’s navigation, communications and imaging payloads on MSubs’ 9 m extra-large uncrewed underwater vehicle. The named equipment includes SPRINT-Nav X for inertial-Doppler navigation, AvTrak 6 for long-range tracking and command and control, and Vigilant forward-looking obstacle-avoidance sonar. The partnership builds on a 2021 DASA UUV Testbed demonstration off Plymouth and targets future UK Ministry of Defence opportunities including Project CETUS.
Source - 2020-03-05 - Contract Award - MSubs wins Royal Navy XLUUV test submarine contract
The first phase would refit a crewed submersible with autonomous control systems. A further GBP1.5 million was conditional on successful initial testing. The programme explored surveillance, reconnaissance and anti-submarine warfare applications.
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Relations
Relationships
- Sonardyne
Autonomous Underwater Platform Technology Partner - Sonardyne and MSubs will integrate and evaluate Sonardyne navigation, communications and imaging payloads on MSubs AUVs.
- Submergence Group LLC
Controlling Shareholder - Submergence Group LLC holds at least 75% of the shares in M Subs Limited.
- UK Submarine Delivery Agency
The Uk Submarine Delivery Agency Contracted Msubs For Cetus/xv Excalibur Trials And Evaluation Through May 2028. - The UK Submarine Delivery Agency contracted MSubs for CETUS/XV Excalibur trials and evaluation through May 2028.
- Li-S Energy
Uuv Battery Testing Partner - Li-S Energy and MSubs are testing pressure-tolerant lithium-sulfur cells for possible use in uncrewed underwater platforms.
- Teledyne Marine
Strategic Collaboration - Teledyne and M Subs are integrating Slocum gliders and Osprey AUVs with Zero USV systems for Royal Navy work.
Context
Comparable profiles
- Cellula Robotics
comparable profile - Autonomous Underwater Vehicle Builder
- Teledyne Webb Research
comparable profile - Autonomous Underwater Vehicle Builder
- Gander Robotics
comparable profile - Autonomous Underwater Vehicle Builder
- Ray Systems
comparable profile - Autonomous Underwater Vehicle Builder
- Gongzhi Marine Equipment
comparable profile - Autonomous Underwater Vehicle Builder
- Kongsberg Discovery AS
comparable profile - Autonomous Underwater Vehicle Builder
Context tags
- Autonomous underwater vehicle builder - Peer Group - https://msubs.com/unmanned/ — Builds S201 and XV Excalibur large uncrewed underwater platforms.
- Autonomous undersea navigation - Capability - https://www.gov.uk/government/news/atlantic-bastion-plans-advancing-as-autonomous-submarine-xv-excalibur-handed-to-royal-navy — MSubs-built experimental vehicle and…
- Maritime autonomy companies - Stack Layer - https://msubs.com/unmanned/ — Company develops underwater vehicle systems and supports autonomy trials.
Commercial
- MSubs receives UK SDA trial contract for CETUS XLUUV
2026-06-26 · Order / contract · The Submarine Delivery Agency published a direct-award notice for MSubs to perform CETUS trials and evaluation.
Source - MSubs wins Royal Navy XLUUV test submarine contract
2020-03-05 · Order / contract · MSubs received an initial GBP1 million DASA award to convert an existing submersible into a Royal Navy autonomous test vehicle.
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