54 Up to 6.75 kWh can be stored in the pack; a sizeable quantity, intended to offset times when lengthy periods of low sunlight occur across mission durations – the team having calculated expectations of average solar energy input against average power output to define battery requirements during development stages. The team is also in the process of releasing an enhanced capacity pack, which will offer 11.5 kWh to provide extra power when needed. “In our collective heads, we anticipate that missions with the SP-48 should last between six to nine months before it becomes practical to bring it back to shore, so we can clean off biofouling and perform any other required servicing,” Boeschenstein says. “We’ve run several deployments of two months at a time – the longest so far – and on each occasion the USV came back with just a few barnacles and a full battery.” Belt-driven thrust A single propeller sits under the USV near the stern, made from anodised aluminium for corrosion resistance, and it is driven by a belt connecting up to a 1 kW brushless electric motor within the hull (which typically runs no higher than 500 W, except when sudden bursts of speed might be needed). “The belt system came from Buddy and Jigger’s past work in automated cloth-cutting systems. Their gantrycontrolled cutting machines all ran extremely reliably on belt drives, with very aggressive cycles of moving back and forth, so they developed a lot of experience with those sorts of drive systems,” says Boeschenstein. Subsequently, the pair and their team determined that both alternate approaches of directly driving the propeller with the electric motor and using a gearbox instead of a belt would require the USV to have a larger form factor in the water. Hence, the goal of size-optimised packaging won out, particularly since the founders possessed a close understanding of how to make belt systems that were highly efficient and reliable amid aggressive use. “We also iterated on the propeller design, especially after running tests in and around seagrass beds when they’d tend to bloom the thickest, ending up with a geometry that minimises the tangling of weeds, fishing lines, and virtually anything else we might run into, inspired a little bit by fishermen that have to go out into marshlands and avoid getting tangled with debris,” Boeschenstein adds. “Lastly, we’ve embedded some motor behaviours into our autonomy stack that has helped successfully shed everything that’s gotten caught in our prop blades during our deployments in the Gulf of Mexico over the last year.” Distributed autonomy The autonomy computing system consists of a distributed network of microcontrollers (including the BMS, power-management system and other low-level controllers). A Windows-based computer, primarily for payload support, serves as something of a main interface, specifically for integrating, configuring and running payloads. That payload computer connects with the network of low-level controllers so they can share data. “That connection also allows the USV to be operated using a different operating system; through an API and implementation of a backseat driver, we can enable commands to be passed to the network through the payload computer,” Boeschenstein says. The founders built the base boat electronic system and software from the ground up, not only for the inherent safety of a distributed architecture, but also December/January 2025 | Uncrewed Systems Technology The six solar panels atop the deck are custom-built, with a total panel power output rating of 816 W, and solar generation of 1 kW per m2 We’ve run several deployments of two months at a time, and on each occasion the USV came back with just a few barnacles and a full battery
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