A modular family of uncrewed surface vessels designed for sustained undersea operations is being developed by BMT, building on its MODUS concept first revealed in 2025.
Speaking at UDT 2026, Jake Rigby, Head of Innovation and Research at BMT, described MODUS as “a family of uncrewed vessels” rather than a single platform, spanning designs from around 20 metres up to 70–80 metres, with early work focused on underwater warfare applications.
The concept is rooted in structural pressures facing Western navies. “As equipment gets more and more complex, but budgets remain broadly the same… we have a limited number of hulls,” Rigby said, adding that crewing constraints are also becoming a limiting factor. Autonomy, he said, forms part of a wider “hybrid navy” approach rather than a standalone answer.
MODUS is designed from the outset as fully uncrewed, which has driven a departure from conventional naval architecture. “We’ve ripped up the rule book on how we traditionally design these vessels,” said Chloe Yarrien, Maritime Autonomous Systems Engineering Lead at BMT, noting that traditional design tools are built around crewed assumptions.
The programme builds on several years of internal research, including work on highly autonomous warships and large uncrewed surface vessels. That earlier work identified the need to define clear operational roles before addressing technical challenges in detail, leading to the current MODUS concept structured around six design principles: autonomy, modularity, availability, buildability, adaptability and affordability.
BMT has prioritised three initial use cases where uncrewed systems offer the most immediate value: persistent data gathering, seabed warfare and anti-submarine warfare. These include hydrographic and oceanographic survey, monitoring of critical undersea infrastructure and acting as part of a distributed ASW barrier. “We wanted sort of 30 to 60 day missions where this vessel could be out on station, working around the clock,” Yarrien said.
Rather than pursuing a single modular hull, the company has opted for a family of designs, concluding that a one-size-fits-all approach introduced unnecessary complexity and cost. The result is a tiered set of platforms, broadly aligned to different operating environments, from coastal to open ocean.
Removing the crew has a significant impact on design trade-offs. Rigby said that while internal volume increases by around 30 per cent, this shifts the constraint from space to weight. “You see the free space and think you can just fill that with fuel, but you still have to be hydrodynamically efficient,” he said, with weight becoming the key driver for endurance beyond 30 days. Reliability also becomes critical, given the absence of onboard personnel to carry out routine maintenance.
The larger variants, reaching up to around 75 metres, are intended to support demanding roles such as towing sonar arrays in the North Atlantic, where seakeeping remains essential. Rigby noted that size in this context is driven by performance rather than cost, adding that “steel is cheap and air is free” when compared to the expense of complex systems.
A recurring theme throughout the discussion was that autonomy requires different operating concepts. “If we just look to employ these vessels in the same way that we employ crewed vessels today, you’re not going to see the change,” Rigby said, pointing to the need for new deployment models and force structures.
During the discussion, BMT also outlined how MODUS platforms could act as motherships for smaller uncrewed systems. Medium and large variants are designed to deploy and recover additional assets, including remotely operated vehicles and other off-board systems. “By packaging them… like a sort of Russian doll piece, you enable that as a package to operate for 30 days plus,” Rigby explained, highlighting features such as moon pools and modular launch and recovery arrangements.
The integration of these vessels into wider force structures remains an area of ongoing work. Rigby said operational analysis and war gaming have already been used to explore how crewed and uncrewed systems might operate together, while Yarrien noted that thinking around hybrid fleets is still evolving alongside customer requirements.
The question of whether platform design should follow operational concepts, or vice versa, was also raised during the session. Yarrien described it as “a bit chicken and egg,” while Rigby pointed to a phased approach as the practical way forward. “That is exactly why we’re proposing that stepping stone approach,” he said, noting that the MODUS concept has already evolved over several years of development.
BMT is now looking to move into prototyping and experimentation, starting with smaller platforms before scaling up, while continuing to refine both the design and its role within future naval force mixes.
Does the UK now lead the world in Design Concepts ?
Will we ever buy any ?
I suppose it’s good there’s a booming trade in naval architecture, at least those skills are being retained. That’s as optimistic as I can possibly be