Preliminary design and technology forecast synthesis for solar-powered high altitude aircraft

High altitude long endurance solar aircraft is a very attractive platform for applications ranging from remote sensing to telecommunication. In contrast to conventional aircraft, the operation of solar-powered one is highly dependent on available solar enengy, which imposes strong constraints on total takeoff mass, and, thus, energy balance becomes dependent on the season and latitude of planned operations. Despite tremendous success in many projects from Helios to Zephyr, energy balance at high altitudes is still not favorable in a range of latitudes and seasons. In this study, a design space for a solar-powered aircraft mission, constrained by its energy balance is explored. It is found that the tradeoff that should be made between seasonal and spatial capabilities for continuous flight of a solar-powered aircraft. The influence of key technologies on solar aircraft perpetual flight capabilities in different regions and seasons is identified. To do that, solar cell efficiency and energy storage specific energy are considered as design parameters in range of available forecasts. In the end, available technology forecasts are synthesized on the precision agriculture case to show which technological level is required to make 6 moths mission possible.