Design of solar powered unmanned biplanes for HALE missions

Some of the results of a research about the design of solar powered Unmanned Aerial Vehicles (UAVs) to be used in High Altitude Long Endurance (HALE) missions are given. The proposed airframe architecture has a biplane layout, conceived to face the most significant challenge for this kind of aircraft: to fly at high altitude, under wintertime conditions and for a wide range of latitude angles. The Solar Powered Biplane (SPB) concept is presented as well as the related design procedure, which can be used to define UAVs for different purposes and mission conditions, such as loiter altitude, latitude and year’s day. A presentation of the design method is given, providing details about models for Aerodynamics, Flight Mechanics, energy balance evaluation, structural analysis and propulsion system sizing. As a particular result of this research, an SPB configuration capable to meet some of the requirements indicated by the US Defense Advanced Research Projects Agency (DARPA) as goals of the HALE flight, is illustrated. Such aircraft, which can operate in each year’s day, at latitudes up to 45° and altitudes up to 18 000 m, is described in details, and a flexibility analysis for different mission conditions is carried out.