If you’ve ever owned a solar-powered garden light, you know how the story goes. It’s fantastic in July, it gets a little moody in October, and by January it’s a decorative stake in the ground. Solar has a winter problem, and so do wind and waves, because the first one tends to disappear for weeks at a time and the second one isn’t something you can schedule.<\/p>\n
A company in Sydney has spent more than a decade building a 24-foot drone boat on the bet that those three sources, stacked together, add up to a vessel that pretty much never needs to come home. And that bet has largely paid off. The boat is in service with three navies, including, by way of a Connecticut partner, the US Navy.<\/p>\n
So why has that same company just bolted a diesel generator into it? The short answer is that two of the new diesel-equipped boats spent October off Southern California towing American sonar arrays in a US Navy-led exercise, and the whole point of the generator was to make sure the sonar never ran out of juice. The longer answer involves high-latitude winters, towed arrays that drink power, and the slightly awkward fact that the sun doesn’t care how good your boat is.<\/p>\n
The boat is called the Bluebottle, after the stinging jellyfish Australians step on at the beach, and it’s built by Ocius Technology. It’s a single hull, a bit over 24 feet long, with a rigid sail that’s covered in solar cells on top of a deck that’s also covered in solar cells.<\/p>\n
When there’s no wind, the sail folds down into the hull. When there’s no sun either, a flipper on the front rudder uses the pitching of the waves to shove the boat forward, which is apparently patented and, from the looks of things, actually works.<\/p>\n
Ocius CEO Robert Dane told Uncrewed Systems Technology a while back that the deck brings in about 100 watts at sunrise and the sail adds roughly 400 more once it’s up. Those aren’t big numbers.<\/p>\n
A hair dryer pulls more. But the Bluebottle doesn’t need to go fast, it needs to stay out, and Ocius says one has stayed at sea for more than six months straight.<\/p>\n
This is where the sonar comes in. The keel holds a winch, which Dane put at about 330 pounds, and that winch lowers a thin cable with hydrophones strung along it.<\/p>\n
That’s a towed array, and it’s the oldest trick in submarine hunting: you drag a long string of microphones behind you, deep enough to get under the layer of water where sound bends, and you listen. The deeper and longer the string, the more you hear. The more you hear, the more electricity the processor on board needs to make sense of it.<\/p>\n
Which brings us back to the generator. Ocius calls the new variant the Bluebottle Hybrid, and the company’s October 21 announcement<\/a> gives two reasons for it. One is low light, and specifically high-latitude winters.<\/p>\n If you’ve spent a December anywhere north of, say, Boston, you know the sun shows up late, leaves early and doesn’t do much in between. A boat that lives off solar panels has the same problem you have, except it’s 10 miles offshore with nobody to plug it in.<\/p>\n The other reason is payloads that draw more power than the panels can supply. A passive sonar array with onboard processing is exactly that kind of payload. So the Hybrid keeps the sail, the solar cells and the flipper, and adds a diesel generator for when they aren’t enough.<\/p>\n Ocius says it uses the same hull and trailer as the renewable version and goes in the water the same way, off a boat ramp behind a regular 4×4 pickup. That’s a pretty big deal logistically, because it means a navy that already owns the trailer doesn’t need a crane or a pier to field the diesel one.<\/p>\n I’ll admit I find the whole thing a little funny. The company’s entire pitch for a decade has been a boat that runs on weather, and the first thing it did before sending two boats to a US Navy exercise with a serious sonar on board was add a tank of fuel.<\/p>\n But frankly that’s the honest engineering answer. A generator you run, say, 10 percent of the time still leaves you a boat that’s renewable the other 90, and it’s a boat that doesn’t go quiet in February.<\/p>\n Ocius hasn’t published how big the generator is or how many hours of fuel the Hybrid carries, and I couldn’t find it in any of the coverage either. That’s a bigger gap than it sounds like it should be, since the diesel is the entire reason this version exists.<\/p>\n The exercise is called Maritime Big Play Pacific, and it’s the first time anyone has put a Bluebottle Hybrid into a navy exercise, by Ocius’s own account. US Pacific Fleet’s announcement<\/a> puts the dates at October 5 to 25, in the Southern California operating area, with more than 40 pieces of government and industry gear from the US, Australia and the UK in the water, on the water, and over it.<\/p>\n Two things you should know about the exercise. It’s an AUKUS Pillar II event, and if you’re wondering what that means, AUKUS is the three-country defense pact that gets written up mostly for the nuclear submarines Australia is supposed to get someday.<\/p>\n Pillar II is the other half, where the three countries share drones, software and sensors right now rather than in the 2030s and beyond. Maritime Big Play is where that half goes to sea.<\/p>\n The second thing is that the Navy’s release doesn’t name the Bluebottle, or Ocius, or any individual company. The participation comes from Ocius, which says its two Hybrids carried ThayerMahan’s Outpost<\/a> acoustic payloads, with ThayerMahan’s TransparenSea software doing the processing.<\/p>\n ThayerMahan is the Connecticut company that owns and operates the Bluebottles in the US, and Outpost is its name for the towed array plus the brains that go with it. So you’ve got an Australian hull, an American array and American software in an American exercise, and the only published confirmation of that combination comes from Sydney.<\/p>\n Here’s Dane, in the company’s release: “We are proud to showcase the Bluebottle Hybrid for the first time and demonstrate the flexibility of the platform in environments where additional power is required, including northern hemisphere operations and missions involving higher-power payloads.” Which is a corporate way of saying “it works up north and it can run a bigger sonar,” and that’s really the entire news. None of this came out of nowhere.<\/p>\n ThayerMahan bought its first two Bluebottles from Ocius in May 2024, for about 2.4 million Australian dollars, and had them shipped to its headquarters in Groton, which happens to be the same Connecticut town where the Navy’s nuclear submarines get built. The two companies had already run a four-day trial of the Outpost-on-Bluebottle combination off California in April 2024, with the boat 10 miles out and the array towed deep.<\/p>\n Since then, by Ocius’s account, the renewable boats have done long transits up the East Coast from Florida to Connecticut and sat through two hurricanes. That’s the company’s claim and I can’t check it, but a 24-foot sailboat riding out a hurricane with nobody on board is at least a thing I’d pay to watch from shore.<\/p>\n Back home, Ocius has a far bigger order to fill. Australia signed up in March for 40 more Bluebottles, and we covered the first hull of that batch getting christened in late June<\/a>.<\/p>\n ThayerMahan then got the contract, in late August, to supply 40 Outpost arrays for those boats under a program the Australians call SEA1200. So the array the two Hybrids dragged around off San Diego this month is the same one that’s about to go on an entire Australian fleet, which is presumably not a coincidence.<\/p>\n You’ll notice I haven’t told you whether the Bluebottles found anything. That’s because nobody has said.<\/p>\n Exercises like this one don’t publish scores, and even when a company does claim a detection, it’s usually against a target that was more or less told where to be. The US Navy’s release talks about anti-submarine warfare, maritime strike and seabed operations as the scenarios, and it leaves it there.<\/p>\n A few other things are missing, and I’d rather say so than paper over them. Ocius doesn’t publish a weight for the current hull.<\/p>\n Naval Technology put an earlier version of the boat at around 1,760 pounds fully loaded, and the newer one is longer, so take that as a floor. The generator’s rating isn’t public, as I mentioned, and neither is how the two Hybrids split their time between weather and diesel during the three weeks.<\/p>\n If you want a sense of why any of this matters, a 16-foot solar drone boat went silent in the Gulf of Maine this fall while it sat recharging<\/a> and drifted for 11 days before it called home. Different boat, different company, same underlying problem.<\/p>\n Batteries fed by sunlight run out at the worst possible time, and a boat that’s supposed to be listening for submarines can’t afford an 11-day nap. The Navy has also been pretty open about how much it likes things that sit in the water and listen, and an American seabed drone heard submarine drones come through a channel<\/a> earlier this year to prove it.<\/p>\n So the diesel is an admission about where the renewable idea stops, and I’d guess we see more of it if ThayerMahan ends up running these boats in the North Atlantic in January. Maritime Big Play Pacific wrapped up on October 25. Nine days before that, on October 16, Ocius opened a new production and operations facility in Sydney to build the 40 Australian boats, and the company says its Bluebottles are now in service with the Royal Australian Navy, the Australian Border Force, the Royal New Zealand Navy and, through ThayerMahan, the United States.<\/p>\n","protected":false},"excerpt":{"rendered":" If you’ve ever owned a solar-powered garden light, you know how the story goes. It’s fantastic in July, it gets … <\/p>\nWhat the two boats did off California<\/h2>\n
The Americans have had these boats for a while<\/h2>\n
What nobody has told us yet<\/h2>\n