Aerodynamic design assessment of Strato 2C and its potential for unmanned high altitude airborne platforms

Abstract Currently, there is a large interest worldwide in the development of High Altitude Long Endurance (HALE) Unmanned Aerial Vehicles (UAVs) for a number of civil and military missions, such as routine weather reconnaissance, surface reconnaissance (forest fires, etc.), earth observation, border patrol and monitoring, fisheries and wildlife refuge management, chemical and biological agent detection, law enforcement, disaster assistance and monitoring, telecommunications relay, movie production, agricultural surveying and control, and provision of targeting information. Passenger and transport airplanes operate at cruising altitudes of maximum 12 000 m where the density is about 25% compared to sea level. HALE-UVAs are foreseen to operate in the stratosphere at altitudes of 24 000 m, twice as high, where the density drops to about 3.6% of the sea level value influencing the lift of the aircraft strongly. The environmental conditions in such altitudes pose strong requirements for the aerodynamic layout and the power plant of an aircraft. In Europe Strato 2C – a manned civil research aircraft – was until nowadays the only aircraft which reached altitudes above 18 000 m. In this paper Strato 2C's aerodynamic design and propulsion layout will be presented and critically reviewed for its suitability for these high altitudes.