Growing affordable mass in the underwater battlespace
Richard Scott
BAE Systems’ Herne extra-large autonomous underwater vehicle (XLAUV) completed initial in-water trials in late 2024, barely a year after commencing development. What was behind this fast-track effort, and how was it achieved?
A number of testbed systems have been funded for at-sea testing, including the UK’s Project CETUS technology demonstrator (being delivered to the Royal Navy [RN] by MSubs) and Anduril’s Ghost Shark (co-developed in conjunction with the Royal Australian Navy and the Defence Science and Technology Group).
The US Navy is a step ahead with its Orca Extra Large Unmanned Undersea Vehicle. Boeing was in 2019 contracted to deliver six Orca vehicles to meet a Joint Emergent Operational Need in the Indo-Pacific region. Delivery of the first vehicle (XLE-1) to the US Navy is imminent, with follow-on Developmental and Operational Testing (DT/OT) running through the third quarter of Fiscal Year 2025. After completion of DT/OT, Unmanned Undersea Vehicles Squadron 3 will complete crew certification, and XLE-1 will be ready for deployment.
Seeing a market opening up in the short-to-medium term, the Maritime Services business of BAE Systems has latterly entered the fray with a self-funded XLAUV development and demonstration effort known as Herne (the name commemorating a mythical phantom huntsman). Initially taking the form of a technology testbed based on an existing commercial vehicle, the company’s capability roadmap envisages an ‘operationalised’ system being ready for market in mid-2026.
Accelerated schedule
Herne was announced to the world at the DSEI 2023 exhibition in London in September 2023. At that time, BAE Systems set out its ambitious plan to get a technology demonstrator into the water and under test by the end of 2024.
That accelerated schedule demanded that the company think carefully about how it could deliver at pace. Key to this was partnering with Cellula Robotics, a marine technology group based in British Columbia specialising in long-range AUVs for subsea survey, science and security. Cellula’s 12 m, 8 tonne Solus-XR modular free-flooding AUV provided an off-the-shelf platform that could be customised to deliver military capability.
“What we saw [with Cellula] was a really agile and flexible company that was very quick in moving to market,” said Nick Martin, BAE Systems’ Herne project manager. “It brought all the advantages of a commercial business which we could marry with our military knowledge.”
The Herne demonstrator is configured with self-contained payload modules located fore and aft, each of which can be lifted out as a single unit, added Martin, “Herne is intended to host a wide range of mission-specific payloads. Swap-out takes about 90 minutes, and requires the removal of just four bolts and detachment of two data connectors.”
The vehicle design offers the option to relocate or consolidate the payloads. “There is no reason in the future why the payloads couldn’t be at the front, or both at the back,” said Martin.
Solus-XR is neutrally buoyant, being filled with synthetic foam, and so uses two large forward planes to give control authority to dive underwater. Alongside twin three-bladed propellers aft – used for long distance transit – the vehicle also features horizontal and vertical thrusters, plus X-form control surfaces aft, to allow for high levels of slow-speed manoeuvrability and/or precise station-keeping in the water column. A hard ballast system is incorporated in the AUV design. This compensates for the increased buoyancy arising from the reduced mass should a payload be deployed from Herne.
BAE Systems and Cellula Robotics began engineering work to develop the Herne demonstrator in September 2023, the same month as the teaming was announced at the DSEI 2023 exhibition. “The vehicle did not exist up until that point,” said Martin. “The first dive [of the vehicle] was at the end of July 2024 [in British Columbia]. So that was ‘whiteboard to water’ in just 11 months.”
Meeting this timeline demanded a high degree of concurrency in development. In practice, this was relatively straightforward: Cellula Robotics simply shared information on the payload space and interface specifications, allowing BAE Systems to move ahead with its payload development activity in the UK without any need to ‘touch’ the platform in Vancouver.
What transforms the basic Solus-XR AUV into Herne is the implementation of military-specific autonomy, integration and assurance. In big handfuls, this can be broken down into BAE Systems’ own Nautomate autonomous control software; a flexible ‘sense, decide and effect’ payload integration engineered through mission-specific plug-ins; and system-level assurance – for example IT security and military communications – to enable use in military applications and environments.
“We’re trying to embrace COTS, not gold-plate it. said Tim O’Neill, BAE Systems Maritime Services’ business development manager. “If we want to enable combat mass, then we understand that this needs to be affordable.” He amplified: “Cellula is providing us our baseline platform. What we are then doing is taking our Nautomate ‘brain in a box’ and putting it into the underwater domain. Nautomate is the core control architecture that drives into the platform…it manages what the platform is doing based on sensing and charting.”
Cellula Robotics’ Solus-XR vehicle provides the baseline platform for Herne. [Richard Scott/NAVYPIX]Nautomate has been developed as a scalable autonomy architecture for both surface and sub-surface vessels. Its key functionalities include situational awareness (fusing inputs from multiple sensors to improve the accuracy and integrity of its world model); smart collision avoidance (mimicking the way a human considers potential collision risks and identifying safe avoidance manoeuvres); and command and control (C2). Mission-based plug-ins are used to facilitate advanced autonomy behaviours, support payload integrations, and/or quickly update software with new algorithms.
“We want to be flexible, and able to perform multiple missions,” O’Neill explained: “The key for us is how to adapt a commercial off-the-shelf vehicle, adapt it for military purpose, and then package and deliver that for a navy to use and support.” He expounded: “That’s where we add value, through our deep knowledge of naval platform design. It’s the trust in the autonomy, with no human-in-the-loop. The integrity and reconfigurability of the software. The security of data and communications. The payload integration. And the accuracy of the navigation solution.”
As an example, the persistence and range afforded by the Solus-XR vehicle led BAE Systems to specify an upgraded inertial navigation system (INS) sourced through Sonardyne. “The navigation system sits within Nautomate, which serves as the core architecture that drives into the platform,” said O’Neill. “It manages what the platform is doing based on sensing and charting.” He added, “At the same time, [Nautomate] it is also managing the payload through the mission plug-ins. Those sit ‘on top’ of the Nautomate core to run the mission.”
Another feature of Solus-XR is its portability. Designed to fit inside a 12 m (40 ft) ISO container on a bespoke skid, it can be transported inside an A400M airlifter or stowed inside a warship mission bay. Deployment is via a standard two-point lift (compatible with a dockside crane, a commercial davit or a standard RN davit). BAE Systems has also looked at submarine hosting and air-drop deployment.
“That launch and recovery piece is key when you are talking about integration into the fleet,” O’Neill observed. “This has to be deployable, whether that’s in an expeditionary setting from a ship, or sailing out from a port. It’s about providing that flexibility for the user.”
The Herne demonstrator vehicle is currently configured with standard Lithium-ion batteries. Located in the mid-section of the vehicle, these offer 2-3 days’ endurance at low speed. Li-ion technology already offers scope to push endurance out to 8-9 days, but BAE Systems is already looking at alternative energy solutions, said Martin. “One of the reasons we picked Cellula is because they are working to bring a hydrogen fuel cell to market. This would provide for a submerged range of up to 5,000 km, and that is hitting a sweet spot with a lot of the use cases we have studied.”
ISR demonstrations
True to its word, BAE Systems performed first in-water demonstrations towards the end of 2024. Undertaken in waters around a commercial port in south England over a two-week period in November, this activity showcased Herne in an operational ‘vignette’ designed to demonstrate an ISR mission. Representatives from 10 nations – including both NATO and Five Eyes partners – were invited to observe.
The Herne XLAUV demonstrator pictured on the surface with its ISR mast extended. [Richard Scott/NAVYPIX]The ISR vignette required the Herne vehicle to conduct a covert sub-surface harbour entry; navigate autonomously; collect video using an ISR mast and identify a hostile target; and then share ISR data when safe. To enable the ISR mission, BAE Systems has developed a low-profile ISR mast – hosting cameras and communications – which is stowed in a fairing on top of the Herne vehicle. “This actuates upwards above the waterline,” Martin explained. “So what the vehicle can do is hover just beneath the surface, raise the mast and come to what is essentially periscope depth, and just sit there for hours collecting information.”
Three different software plug-ins were demonstrated in the ISR vignette: goal-based mission autonomy (enabling the Herne vehicle to autonomously re-route so as to avoid a series of drag net hazards); machine vision (processing 4K camera imagery to classify ships by type); and track-and-follow (exploiting the camera feed to shadow a rigid inflatable boat ‘target’).
“These demonstrations have sought to showcase where the company has invested, and focused effort,” said O’Neill. “They have also served as a check that we’re going in the same direction as our customers.”
Next steps
Building on this initial demonstration, BAE Systems now looking at how it further matures Herne. “We’re sitting down with Cellula to explore a number of threads going forward,” O’Neil said. “That will include iterations to the platform, looking at any changes or improvements with regard to power, propulsion, speed, efficiency and signature.” He added, “That said, what Cellula have got – their strongback design, the modularity and the flexibility – is still going to be the core. What we will be doing is layering on top of that.”
BAE Systems is aiming to have an initial production-standard Herne variant ready for market by mid-2026. “In 18 months’ time we want to be able to offer this as an operational battle-ready configuration,” O’Neill said. “That will include the option for hydrogen fuel cells.”
“That’s a tight timeline,” he added, “and so we’re clearly not going to be build three, four or five vehicles in that period. So we will go through some changes, and make those physical instantiations. But a second vehicle is something we are certainly looking at from the platform development side.”
Alongside this, O’Neill noted, “We’re trying to be proactive so that when navies are more confident of their needs, and their concepts of operation, we are ready to respond. And by adapting an existing off-the-shelf [vehicle] platform we can significantly reduce the time and cost to market.”
Further development of Nautomate is continuing in parallel: for example, building additional mission-based plug-ins, and evolving the ‘intelligence’ in the system. BAE Systems will also evaluate overall ‘useability’ aspects such as launch and recovery, in-service maintenance, and through-life support. “If these things aren’t easy to use, and easy to look after, and easy to live with, they are not going to deliver what navies want” said O’Neill, “So there is a delivery of capability to think about in the first instance. But we have to remember that it’s got to be there for an extended period of time. So it’s got to be useable, and we need to look at this a whole system. That includes the whole ‘ecosystem’ around communications, networks, and combat systems.”
As regards future payloads, definition work has already started for an ASW package. Maturing this particular use case reflects growing interest in the role that XLAUVs could play as part of a wider ASW barrier comprising a heterogenous mix of uncrewed assets.
XLAUVs will allow large and expensive crewed assets to be freed up for priority tasks, while at the same time removing personnel from ‘dull, dirty and dangerous’ missions. [Richard Scott/NAVYPIX]“We want to have thin-line passive towed array that is reelable within the platform,” O’Neill said, “That makes it covert – you don’t want to have a mother ship attaching a clip-on array and then streaming it. So you would want to have a reeling machine and array integrated into the payload bay”. O’Neill added, “The other ASW piece I’d like to try out, and see if it is feasible, is setting up Herne within a multistatic ASW environment. That is a bigger challenge because of the need to time-stamp data and get that transmitted back to the hub is key.”
Multistatics delivers an enhanced ASW capability by processing the multiple returns from a combined field comprising an active source and several passive receivers. This creates multiple acoustic pathways within the water space, thereby greatly increasing the probability of gaining a detection of an evading submarine.
“It comes back to freeing up crewed platforms to do what they do best,” said O’Neill, “If you’ve got a Type 26 frigate, with a Sonar 2087 active tow, why not use that as your active source and then deploy multiple passive receivers in consort.
“This means that the submariner has no idea in which direction returns from the ‘pings’ are being detected. Yes, he knows where the ‘ping’ is coming from, but there is no way of knowing where his target echo is being picked up. That’s a gamechanger” O’Neill emphasised, “So there are a number of different ASW scenarios we want to look at. And the only way we are going to learn is by getting [Herne] in the water.”
Electronic warfare is an additional use case under study. The thinking here, said O’Neil, is to employ Herne as a covert, forward deployed capability. “Whether that’s interception, deception, disruption or jamming, there are various payloads that we and the scientific community want to try on the masts.”
Networking with other assets is another agenda item for 2025. So too is work on the deployment of a remotely-operated vehicle (ROV). O’Neill explained, “Cellula have already done some work deploying an ROV from Herne. We’d like to revisit that to understand how that could support CNI investigation and protection at depth.”
Richard Scott
Author: Richard Scott is a UK-based analyst and commentator who has specialised in coverage of naval operations and technology for over 25 years, with particular interests in the fields of naval aviation, guided weapons, electronic warfare and autonomous systems.
