Design of a high-altitude long-endurance solar-powered unmanned air vehicle for multi-payload and operations G Romeo  , G Frulla, and E Cestino Department of Aerospace Engineering, Turin Polytechnic University, Corso Duca Abruzzi, Turin, Italy The manuscript was received on 1 June 2006 and was accepted after revision for publication on 22 September 2006. DOI: 10.1243/09544100JAERO119 Abstract: Several researches are being carried out at the Politecnico di Torino with the aim of designing a high altitude very-long endurance/unmanned air vehicle (HAVE/UAV). Being able to fly in the stratosphere (15 – 20 km) and with an endurance of about 4 months offers an advan- tage and possibility that is presently not available with conventional aircraft or satellites. A computer program has been developed to design the platform. The change in solar radiation over a period of a year, the altitude, masses, and efficiencies of the solar and fuel cells, as well as the aerodynamic, structural, flight mechanics, and aeroelastic performances have all been taken into account. Extensive use has been made of high modulus graphite/epoxy when designing the structure in order to minimize the airframe weight, but also to guarantee the required stiffness and aeroelastic performance. A blended wing body (BWB) configuration has been selected for solar HAVE aircraft multi payload and operation (SHAMPO) with eight brushless electric motors, as the result of a prelimi- nary design. The BWB solution has been designed according to the conventional procedures and airworthiness regulations. It seems to be the best compromise between performance, available surfaces for solar cells and volume for multi-payload purposes, compared to conventional design. Several profiles and wing plans have been analysed and optimized to achieve the best effi- ciency using the Xfoil and Vsaero computational fluid dynamics (CFD) software. A finite- element method and a classical theoretical analysis was carried out using the Msc/Patran/ Nastran code to predict the static and aeroelastic behaviour of the SHAMPO. Aeroelastic analysis has been performed starting with a classical linear flutter analysis and considering an undeformed equilibrium condition. Classical linear flutter speed show as the airworthiness requirements has been achieved in the case of SHAMPO configuration. A preliminary non-linear aeroelastic model is introduced in the design process in order to deal with specific phenomena correlated with high static structural deflections occurring during standard flight conditions. Important flutter speed reduction (i.e. up to 42 per cent in special cases) are possible including such kind of phenomena. Keywords: aircraft design, high altitude very-long endurance, unmanned air vehicle, aerodynamic, stability, structure, aeroelastic, flexible wing 1 INTRODUCTION Stratospheric platforms, geostationary located at altitudes of 17 – 25 km, offer the possibility of becoming a new generation of infrastructural elements for future Earth observation and telecom- munication systems. They can act as pseudo- satellites, but with the advantage of being much cheaper and closer to the ground and they can per- form missions that offer greater flexibility. They could be self-launched, easily recovered for mainten- ance, whenever necessary, and moved to cover different regions, if desired. They allow a more  Correspondence author: Department of Aerospace Engineering, Turin Polytechnic University, Corso Duca Abruzzi 24, Turin, 10129, Italy. email: giulio.romeo@polito.it SPECIAL ISSUE PAPER 199 JAERO119 # IMechE 2007 Proc. IMechE Vol. 221 Part G: J. Aerospace Engineering