64 In operation | Seasats Lightfish USV The page also showed numerous configurable graphs plotting power usage or generation over time for individual subsystems, and some for multiple subsystems against one another, such as clusters of data from the BMS, as well as time charts showing when certain devices (such as the bilge pump and the different BVLOS communication devices) were activated or deactivated. A dropdown box in the top-right enables the user to set the length of time over which averages and stats are shown (running from the prior five minutes to the past several days or weeks), and aggregates for highlevel stats such as power balance over the selected time period also display persistently on this page. Sunshine and alcohol As the USV travels, its thrust and rudder motors typically consume the most power of any subsystems. A single COTS Torqeedo motor pod propels the boat forwards. Seasats has trialled many of that company’s solutions. “Testing multiple motor pods simultaneously for six months in a fast-paced environment is hard, but very much necessary to guarantee a six-month endurance, so we have saltwater tanks at our shops, and motors, servos – essentially everything new that’s to go into the boat. They all get submersed and run in those saltwater environments at different duty cycles for their lifespan,” Kramers says. “IP ratings are self-certified and, frankly, a lot of companies stretch their stats, so it’s pretty crucial to do our own component validation before we opt to integrate and sail with them.” Through such testing, Seasats validated and installed its rudder servo, a device operating on a stainless steel gear train and brushless DC motor (built and supplied by an undisclosed company). Through that <500 g device, the USV manufacturer achieves a longlived rudder-steering capacity over multi-month operations (an impossible proposition for hobby-grade servos), as well as over 1300 n/cm of torque for harsher sea states. As mentioned, most of the USV’s in-operation energy replenishment comes from its solar panels – nominal solar generation being 415 W – with the power analytics screen enabling users to make ad hoc adjustments to vehicle speed or subsystem activations if something onboard is consuming excess energy. “We use a custom-built, flexible, monocrystalline, silicon solar panel,” Rodriguez says. Kramers adds: “We also have our supplementary methanol generator. It weighs around 9 kg, provides about 125 W continuously, and fits nicely in the Lightfish. The tank the supplier provides can carry up to 30 kWh of fuel. It is a cold combustion engine, and it essentially runs on hydrogen, but the hydrogen is suspended in methanol. “That can be used when we’re doing multibeam echosounder surveys, given that those types of sonars are very power-hungry; and there’s other payloads too that need the generator’s level of power output, whether it’s EW jamming [electronic warfare], towfish, or so forth.” April/May 2025 | Uncrewed Systems Technology The solar panel atop the USV is a flexible array, assembled from monocrystalline silicon, and it nominally generates 415 W of energy
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