BAE Systems has pushed an audacious bet into the maritime domain with its Herne extra large autonomous underwater vehicle demonstrator. The project pairs BAE’s Nautomate autonomy and systems integration work with Cellula Robotics’ Solus-XR commercial hull to produce an XLAUV testbed intended to explore persistent, long‑range undersea missions.
The engineering choice is worth pausing on. Rather than build a bespoke pressure‑hardened hull from scratch, BAE elected to adapt a free‑flooding Solus-XR airframe and then focus its effort on the autonomy, payload integration and assurance layers that define military utility. That approach delivered pace. According to reporting, the collaboration moved from teaming to first dives in a little over a year, an impressive whiteboard‑to‑water timeline that underpins the demonstrator’s raison d’etre.
What sits inside the hull is the feature set that matters. Nautomate functions as a platform‑agnostic autonomy architecture offering fused situational awareness, collision avoidance and mission plug‑ins for behaviours such as goal‑based routing, machine vision and track‑and‑follow. The demonstrator also showcased a low‑profile ISR mast for near‑surface imagery and communications, and an upgraded inertial navigation package integrated to support long range navigation tasks. Those are the elements that convert a commercial vehicle into a militarisable node.
BAE staged in‑water ISR vignettes in late 2024 to show those capabilities in practice. The scenarios were designed to exercise autonomous harbour entry, periscope‑depth mast usage, on‑board classification and selective data exfiltration. The demonstrator was shown to invited observers from multiple nations, the obvious audience being navies that want to buy persistent undersea presence without the cost and risk of crewed vessels.
There is a strategic logic to Herne. The utility of XLAUVs is simple to state. They extend reach, buy persistence, and offload repetitive or hazardous ISR and area denial tasks from expensive crewed platforms. If the autonomy and assurance primitives are trustworthy, a fleet of attritable XLAUVs could complicate an adversary’s calculus while freeing higher value assets for other tasks.
But the demonstrator also exposes the tradeoffs that will determine whether that logic becomes doctrine. First, using a commercial free‑flooding hull lowers acquisition cost and accelerates schedule, but it also shifts many design constraints onto the payloads and pressure cans. Survivability in contested, high‑energy anti‑access environments remains an open question. Second, endurance is currently dominated by battery technology on the demonstrator configuration, yielding days not months of submerged operations; alternative energy solutions such as hydrogen fuel cells are being explored, but those introduce logistics, safety and refuelling considerations of their own.
Third, autonomy is necessary but insufficient. Nautomate and similar stacks will be judged less by clever behaviours in controlled trials and more by how they degrade safely, how they respond to adversary electronic attack, and how their decision chains can be audited after an incident. Assured autonomy demands rigorous engineering for integrity, secure communications, explainability and human‑machine interfaces that allow meaningful oversight without overwhelming operators. The Herne demonstrator shows attention to those layers, but demonstration is not yet operational validation.
Finally, there are normative and doctrinal implications. XLAUVs that can loiter for long distances, collect classified imagery, and, in principle, host effectors, challenge existing notions of escalation, attribution and rules of engagement at sea. Navies will have to agree not only how to employ these tools, but also how to certify them as compliant with the laws and norms that govern naval operations. The technology will not stay purely technical for long. It will force legal and political choices.
In short, Herne is not a product so much as a focused experiment. It demonstrates that a pragmatic, modular path to militarisable XLAUVs exists. It also reminds us that speed to water is only the first metric. What counts next is rigorous assurance, survivability analysis, logistics of endurance, and an honest public and professional debate about the operational and ethical boundaries that should govern autonomous undersea systems. The demonstrator is a conversation starter. The real work comes after the applause for an elegant proof of concept.