Thermal Management of Electrical Systems in a Solar-Electric Stratosphere HALE

Abstract

Innovations in the various disciplines of aeronautics such as battery technology and composite structures have opened the door to completely unprecedented aerial vehicle designs. The High Altitude Long Endurance (HALE) aircraft is a case in point. Jumping on the trend, the German Aerospace Center (DLR) is betting on the "High-Altitude Platform (HAP)", a solar-powered HALE Unmanned Aerial Vehicle (UAV) intended for satellite-like operations. Throughout the mission the HAP will have to cope with extreme environmental conditions characterized by low air temperatures and densities and high amounts of radiation. Consequently, the correct operation of the electronic devices will be jeopardized. This contribution covers the thermal management of the avionics devices on board the HAP. For this purpose, a mathematical thermal model based on first principles has been constructed. Firstly, the model represents the current HAP design. From the estimations, it has been predicted that the avionics will have to face overheating and overcooling challenges, with temperatures between -60°C and 190°C being reached. In a subsequent step, temperature control techniques have been applied. Selecting passive techniques as preferable, preliminary results show that the introduction of conductive plates, paints and heat sinks ensures that the temperatures of the avionics devices are maintained within their specific operating temperature range.