VectorNav UNPRECIDENTED PERFORMANCE AT YOUR FINGERTIPS Introducing the all new Tactical Embedded line. The best just got smaller. Tactical-Grade IMU Heading: 0.05°C-01° Pitch/Roll: 0.015° GNSS: L1/L2/E1/E5 with RTK/PPK VECTORNAV vectornav.com +1.512.772.3615 50 issues of Uncrewed Systems Technology | Special review in gravimetric energy density can be bucked. Certainly, battery technologies are emerging with higher and higher specific energy to aid their use in UAVs, but too often that comes with drawbacks to do with discharge rates and other performance factors. As fuels provide far higher specific energy than batteries, hybrid powertrains are vital to unlocking flight times longer than an hour for small, professional multi-rotors, and upwards of say 4 or 5 hours for small and otherwise all-electric fixed-wing systems. There are a few trends in existing hybrid power units, such as that integrated into Xer Technologies’ X12 hybrid multi-rotor (issue 44). Xer’s proprietary solution for instance took considerable focus on cooling, vibration damping and stable power management for it to work safely on its flagship UAV. Managing qualities such as these has been similarly important among hybrid powertrains of all sizes throughout the UAV world, such as Pegasus Aeronautics’ 4 kWGE70 (issue 20, June/July 2018), or Sky Power’s 22 kW SP-180 hybridised Wankel (issue 25, April/May 2019) and the larger variations of this solution the company has unveiled since. Further innovations can be seen outside these trends that still form part of the overall push to make UAVs more fuel-efficient. For instance, our 31st issue (April/May 2020) included a detailed investigation of Turbotech’s microturbine engines – one a turboprop, the other a hybrid turbo-generator, but both using similar engineering. Although microturbines typically achieve a fuel efficiency of around 10%, Turbotech devised a system to recuperate otherwise-wasted exhaust heat. That greatly reduces the amount of fuel needed to heat and pressurise its charge air to drive its turbine at 80,000 rpm, and raises its fuel efficiency to a more respectable 30% – a rare achievement among microturbines. Such technology is being validated throughout the industry. For instance, Aergility has chosen Turbotech’s engine for its Atlis UAV (covered in issue 47), one of the largest aircraft we have investigated in detail. And Turbotech’s engineering philosophy is echoed by others – UAV Turbines (issue 11, December 2016/ January 2017) for instance also continues to produce recuperated microturbines, while newcomer Aant Farm briefly told us at AUVSI Xponential 2023 about its two original recuperated microturbine powertrains. Readers can of course expect us to delve into Aant’s approach in a future issue. Alternative fuels Notably, Turbotech also plans to continue developing its engine for running on alternative, more environmentally friendly fuels such as biofuels and hydrogen; Tactical-Grade IMU Heading: 0.05°-0.1° Pitch/Roll: 0.015° GNSS: L1/L2/E1/E5 withRTK/PPK UST 1-2 pg_10-08-20.indd 1 10/8/2020 8:23:26 AM
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