Placement of broad beam beacon antennas within wing of HALE UAV

The wind speeds at the bottom of the stratosphere (≈20km altitude) are relatively low. Consequently, for several decades there has been interest in placing aircraft at those altitudes which would loiter and thus be suitable as platforms for earth observation and communications systems. This would add a layer between terrestrial and satellite systems, that had all the advantages of geostationary satellites without the disadvantages of propagation delay, high launch costs and the inability to retrieve the platform for servicing [1]. Solar powered flying wing Unmanned Aerial Vehicles (UAVs) offer the promise of “eternal flight” where the UAV would remain airborne for years without landing. NASA´s Environmental Research Aircraft and Sensor Technology (ERAST) program aimed to develop such UAVs, but this work was terminated with the loss of the 70m wingspan Helios in 2003. This accident also brought an end to the various radio communications and localisation systems for stratospheric UAVs that were under development at NICT. After a furlough of almost a decade, the promise of low operating cost airborne platforms for earth observation and communications systems has sparked a revival of interest in the US, with public funds been committed for the development of a single 140m wingspan prototype to fly in 2014 that is capable of supplying 5kW of power to a 450kg payload [1]. With a potential revival in the wind, this paper considers placement of UHF antennas within a generic solar powered UAV wing for a Direction of Arrival (DOA) system.