There’s a normal way to buy a military submarine, and it’s slow. A navy writes a requirement, a yard spends years building a single boat around it, and the cost climbs the whole way. BAE Systems has been building something meant to skip that routine since 2023: a 12-meter uncrewed submarine designed to be ordered as a finished product instead of commissioned as a one-off.<\/p>\n
The company calls it Herne, and the newest version was laid out to reporters at BAE’s Broad Oak site in Portsmouth in late June. The pitch is that Herne goes on sale as an operational platform by the end of 2026, to the Royal Navy or to export customers, and that it’s built to be turned out in numbers rather than hand-crafted one at a time.<\/p>\n
The big change in this version is structural, and it has more to do with how Herne gets built than how it swims. Will Doherty, BAE’s programme lead for autonomy, told Janes<\/a> the new Herne uses a bolted aluminum framework in place of the “spine” design of the earlier Herne Alpha prototype, a switch made for ease of manufacture.<\/p>\n That sounds dry until you think about what it’s for. A bolted aluminum frame is something a production line can put together quickly. A hand-built one-off is something skilled people assemble slowly. If the plan is to sell these as a product, the frame is the part that decides whether “a product” is even possible.<\/p>\n BAE is designing the vehicle and Cellula Robotics, its Canadian partner, is manufacturing it. The two signed a 10-year exclusive agreement in 2025 to keep Herne going as a military product line.<\/p>\n The pace has been the selling point from the start. The original prototype went from whiteboard to water in 11 months. The software running it, BAE’s platform-agnostic Nautomate system, had already been proven on a surface ship before it ever went underwater.<\/p>\n Herne is 12 meters long and splits into six sections: power at the back, sensors up front, and mission payloads in the middle. That central bay holds up to 5,000 liters of whatever a customer wants to send down there, whether sonar, cameras, comms gear, or something classified enough that BAE won’t say.<\/p>\n It’s also a free-flooding design. Instead of one sealed pressure hull holding back the ocean, seawater is allowed into the structure, and only the parts that can’t get wet (electronics, power) sit inside their own sealed housings.<\/p>\n That’s standard for this class of vehicle, and it’s part of why they can be built lighter and cheaper than a crewed submarine, which has to keep every liter of the ocean out to keep its crew alive. Nobody’s aboard Herne, so there’s no life support to carry and no reason to surface for a tired crew. BAE’s argument is that a machine like this can sit on station far longer than a crewed boat, doing the dull, patient work of watching a patch of seabed.<\/p>\n How long Herne can stay down depends on what’s in the power section, and this is where Cellula’s other work matters. The company builds a hydrogen fuel cell module it says is good for over 5,000 kilometers of range and more than 45 days submerged, according to Navy Lookout<\/a>. There’s also a lithium-ion option for shorter missions, which trades endurance for simplicity.<\/p>\n Cellula isn’t theorizing here. Its survey drone, the Envoy, a close relative of the Solus-XR hull Herne is built on, ran a fully submerged test of more than 2,000 kilometers<\/a> on a single hydrogen fuel cell earlier this year, staying under for over two weeks with no support ship overhead.<\/p>\n That’s the whole pitch for hydrogen in one line: nobody has to sail out and babysit the thing. And because Herne is built around Cellula’s existing survey vehicle, BAE isn’t inventing an underwater drone from a blank sheet. It’s putting military autonomy and a modular payload bay onto a hull that already works.<\/p>\n Here’s the part that makes Herne interesting, and it isn’t the hardware. Britain already operates a 12-meter uncrewed submarine of its own: XV Excalibur, built by MSubs in Plymouth under a program called Cetus. It was named in 2025 and handed to the Royal Navy that December.<\/p>\n But Excalibur was never meant to go to war. Navy Lookout describes it plainly as a trials platform<\/a>, a boat that exists so the Navy can carry candidate payloads and propulsion to sea and learn how uncrewed subs behave. It measures 12 meters, displaces 19 tonnes, and is scheduled to keep running experiments through 2028. One bespoke vehicle, years of testing, no plan to sell it to anyone.<\/p>\n Herne is the opposite bet. Same rough size, but built by a prime contractor as a product line it wants to sell to multiple navies, off the shelf, starting late 2026. It’s the difference between a research boat and a catalog item.<\/p>\n BAE is moving into a field that filled up fast. Australia is buying dozens of Anduril’s Ghost Shark<\/a> drone subs, built on a production line in Sydney and pitched for export the same way. The U.S. Navy has been testing expendable designs fired straight out of a torpedo tube. South Korea, Germany, and Canada all have hydrogen-powered uncrewed subs in the water.<\/p>\n The reason everyone’s rushing is the one BAE keeps citing: these machines are cheap next to crewed submarines, they don’t put sailors at risk, and there’s a growing list of things to guard down there.<\/p>\nTwelve meters, six sections, and a hull the sea is allowed into<\/h2>\n
Cellula’s hydrogen fuel cell is the endurance play<\/h2>\n
The Royal Navy already has a 12-meter drone sub. It isn’t for sale<\/h2>\n
Herne is one entry in a very crowded race<\/h2>\n