Unmanned Systems Technology 042 | Mayflower Autonomous Ship | Embedded Computing | ElevonX Sierra VTOL | UUVs insight | Flygas Engineering GAS418S | Ocean Business 2021 report | Electric motors | Priva Kompano

32 number of animals and species by litre to inform their models of ocean biodiversity. “The water can then flow through the Hypertaste and on to other sensors for salinity, temperature, fluorometry, chlorophyll analysis and many other metrics on the water and the micro- organisms in it.” The USV’s study of life is not limited to ingested water samples though. External hydrophones on the MAS will listen for miles through the ocean to identify, count and track large marine mammals such as whales, dolphins and seals. This data can then of course be cross-referenced with real-time meteorological, climatological and water measurements to learn more about these creatures’ migration and breeding behaviours, and in general gain a deeper understanding of how the balance of the ocean’s ecosystems can be supported and sustained. Hull design and materials The Mayflower’s trimaran shape was identified as ideal for internal subsystem volumes as well as streamlined hydrodynamics, in the absence of the myriad requirements for human life on the vessel. “When you strip out all the beds, food, kitchen stuff, waste management, life support systems, safety systems and so on, you end up with a huge amount of empty volume,” Phaneuf points out. “Rather than fill it with ballast, which wouldn’t be very efficient, we opted to reduce the displacement and hence the bill of hull materials. That meant we ended up with a long, thin, drag-efficient shape, which was accordingly wired with long, nicely organised straight lengths of cable to make maintenance easier. “The only problem was the vessel became very ‘tippy’. So we put a pair of outriggers on it to keep it from falling or rolling over, and that turned it into a trimaran. “That’s sort of the reason why so many USVs are catamarans or occasionally trimarans. Unless you’re making a high-speed planing hull, you tend to converge around these float-based hull forms very quickly, simply because of the physics of how you help a boat to stay upright automatically.” As mentioned, the hull design is also a compromise between operational effectiveness and affordability, and the latter of these in particular drove the selection of aluminium as the Mayflower’s primary construction material. “Aluminium’s ease of fabrication, particularly when using laser-cut panels and similar pieces and processes, allowed not only for reduced expense and complication in building the boat but also for a very quick transfer of the architecture from design to construction,” Scott says. “And like Brett said before, the design changed as the engineers were building it. Thankfully, aluminium’s quite easy to work with: you can drill holes in it, attach things; it’s quite flexible and bendable. You don’t get any of that as easily with composites, so aluminium really helped us minimise costs and waste while evolving the design.” Phaneuf adds, “When we started, we didn’t really think we were going to build more than one, so it didn’t make sense from a cost perspective to make moulds for fibreglass or other composites. If we’d gone in expecting a production line of them we might have gone that way, but it would’ve cost more, taken longer and given us less flexibility in optimising the shape of the craft. “It’s important to bear in mind that the Mayflower is in essence a proof-of-concept vehicle, which we’ll take into full commercial service once it’s ready, and we very much plan to build more once the concept is proven. But for all the reasons given, that concept will probably remain aluminium when the time comes.” As the USV might be at sea for an extremely long time (especially since consistently catching good weather would theoretically keep its batteries charged forever), some basic anti-fouling paints have also been applied below the waterline, but not heavily so. After all, the team’s scientific clientele do not want to discourage lifeforms from congregating near the water sampling inlets. Phaneuf adds though that he and his colleagues are investigating some novel hydrophobic coatings from companies such as Protectology, in order to reduce biofouling and friction without affecting the biological content of water samples or inducing galvanic corrosion, as some paints do. Ocean navigation The problem that the Mayflower’s team is looking to solve should be clear: the longer the voyage, the greater the time and distance in which something mechanical, electronic or otherwise could fail. The aforementioned Microtransat Challenge has been littered with USVs running aground, suffering motor failures, losing radio contact, getting caught in fishing nets, and much of the time simply vanishing without a trace. Furthermore, the ocean itself poses hazards that could lead to disaster. Seawater can corrode hulls and subsystems, waves slamming on the vessel can break them, constant February/March 2022 | Unmanned Systems Technology When you strip out all the beds, food, kitchen stuff, life support and safety systems and so on, you end up with a huge amount of empty volume

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