Modernising Delivery: A Low-Energy Tethered Package System Using Fixed-Wing Drones

Fixed-wing Uncrewed Aerial Vehicles (UAVs) can be used for remote package delivery missions by connecting a package to a UAV via a long tether. With a circular flight path at a calculated loiter radius, tether length and orbiting velocity, a package can be lowered to the ground in a quasi-stationary manner. This method achieves this with significantly less energy than hybrid hovering aircraft, which are currently used. UAV operating limitations pose a challenge for this method as ensuring the package stabilises such that it can be safely deployed without damage or posing a risk to people or property is challenging in most environmental conditions. To improve tether and package stabilisation, we introduce a novel Mid-Tether Drag Device (MTDD) which enables compliant delivery missions within regulatory frameworks. We present a mathematical model of the delivery with a UAV and MTDD. We verify the accuracy of our model with real-world flight tests in low wind conditions without the MTDD, which have not been previously conducted at this scale in literature. Further validation is presented with flight tests at a flight range using a UAV instrumented with a package deployment system with both UAV and package tracking data acquisition. Our work enhances the abilities of UAVs to conduct aerial package delivery.