Unmanned Systems Technology 020 | Alpha 800 I Additive Manufacturing focus I USVs insight I Pegasus GE70 I GuardBot I AUVSI Xponential 2018 show report I Solar Power focus I CUAV Expo Europe 2018 show report

The GE70 alongside the batteries it replaces, the latter providing only 12 minutes’ flight duration 62 Dossier | Pegasus GE70 same concept for our system. It has the ability to generate the necessary power with an infinite combination of torque and rpm, and automatically select the most efficient combination. “That is of course a very simplified explanation, but it gives an idea as to why we don’t have to compromise between efficiency and power. Our system literally gives the best of both worlds. “Also, do you want a perfectly tuned vibration damping rig optimised for a specific rpm? The system can do that. Do you want to put the frequency of the engine into a zone that is easily filtered out by other hardware? The system can do that. It gives UAV users many new capabilities.” GE70 performance For Pegasus’ DA70-based ICE, the time between overhauls is currently more than 200 hours, but with development the target is 1000 hours. Its maximum output depends on the exhaust configuration but is in the region of 7 bhp/5200 W. The efficiency of the generator/GCU in terms of converting crankshaft power into DC for the UAV depends on power level and operating circumstances, but on average it is around 90%. To be on the safe side, Pegasus rates the GE70 as a 4000 W system, with an optimum power output range of 2000-3500 W. “If you are looking at a UAV that can carry a 7 kg payload, you would be looking at a total of between 15 and 20 kg base weight and you would be looking at between 2500 and 3500 W,” notes McRoberts. “Some potential GE70 customers are using $20,000 worth of batteries per platform per year. With our system you need just one, much smaller, battery. And you carry much more airtime in a jerry can of gas than you do in a whole bunch of batteries.” The base weight of the GE70, including all four components plus the CD box, is 3.5 kg. The installed weight, dry, is 4.3 kg in the case of Aerial Alchemy’s Dragonfly UAV, in which it is initially flight testing. “The batteries it replaces are convenient insofar as they are rectangular, but you need four of them to attain 12 minutes of flying time,” notes McRoberts. “Our system might require a little more figuring out to install, but that is a one-time task, and relative to the batteries it replaces its overall volume is much less. “The four batteries sufficient to carry a 7 kg payload for 12 minutes’ flying time that it replaces weigh 8 kg. Fuelled, our system might come back up to the same take-off weight, but with that 3.7 kg of fuel the airtime would be extended from 12 minutes to at least 90. We are hesitant about quoting figures for fuel consumption, as we keep making gains during our development process. “Remember too that, as the fuel load diminishes over the course of a flight, the power requirement diminishes at an exponential rate, to the extent that you end up just sipping fuel. A lot depends on your fuelling strategy. “Also, there might be an application in which someone is very particular about vibration characteristics, so they might have the approach of running the engine at minimum-vibration rpm, even at the expense of fuel consumption. Our system can cope with that.” It is worth noting that the Pegasus system avoids the mission disruption from having to switch batteries every 12 minutes. Not only is that a great help logistically, it ensures a continuous data stream that is unaffected by, for example, the changing lighting conditions that are more likely to characterise a ‘stop and go’ battery-electric mission. McRoberts concludes, “In that example of using 3.7 kg of fuel, I expect to see far more than 90 minutes’ duration as we carry out further testing of the GE70 and continue to develop the system. A ten times extension of flying time is a creditable target.” June/July 2018 | Unmanned Systems Technology