Unmanned Systems Technology 014 | Quantum Tron | Radio links and telemetry | Unmanned Aerial Vehicles | Protonex fuel cell | Ancillary systems | AUVSI 2017 Show report

beyond that weight category sourcing them becomes trickier. “You can find motors, but you have trouble finding ones with the correct number of windings you might want to use,” Seibel says, “and it affects the number of batteries you need. You just don’t have the same choice as with smaller UAVs, and also they get more expensive, which slows a young company down.” That is because finance becomes harder to obtain. Heat dissipation also becomes more difficult at greater weights because of the higher power levels required. “With a 5 kg UAV you don’t have any problem getting rid of the heat from the ESCs or the batteries when you draw high currents, but when you go up in gross weight, you need bigger fans.” Furthermore, he says, flight testing light UAVs requires far less space than a heavier vehicle would because of the kinetic energies involved. “The deceleration coming back from fixed- wing flight into a hover with a 5 kg version would take 30-40 m. With a 25 kg version, to get rid of all the energy from 100 kph – kinetic energy being proportional to the square of the velocity – takes a much greater distance.” Human factors also come into play as engineers get frustrated if something doesn’t work out, and there is also the fear factor that comes from knowing that if a 25 kg UAV crashes it could kill someone. But if a small, light vehicle has a hard landing in a field it won’t necessarily damage anything and the team can just carry on. In normal forward flight, the Tron stops and folds its rear motors, and flies on the front pair for efficiency, but the rear motors then provide reverse thrust for rapid braking to transition speed