CONTROL SYSTEM DESIGN OF A HIGH ALTITUDE PSEUDO SATELLITE IN THE STATION KEEPING PHASE

The main objective of this thesis is to perform preliminary design considerations for the operation of a High Altitude Pseudo Satellite in the station keeping phase. HAPS represents a new concept of aircraft to be operated in the stratosphere (approximately at a height of 20 km) and therefore its design must take into account specific issues related to this challenging environment. One of the most critical elements is represented by the accurate determination of wind speed and direction, the knowledge of which is essential for attitude control propulsion system preliminary design. In the thesis a statistical analysis of wind speed data made available from NOAA (National Ocenaic and Atmospheric Administration) has been performed considering four hours per day from January 1980 to December 2019 for a point located at 50 mb altitude with assigned latitude and longitude. At first, the one year mean wind speed profile has been considered for the zonal and meridional wind components to retrieve information about the main wind speed direction. In order to best interpolate the data, a comparison between some statistical distributions has been done with Matlab, showing that the Weibull distribution best fits wind speed data. The outputs of the wind statistical analyses have been used for the prelimary design of the HAPS propeller, performed employing an enginnering approach based on Renard’ curves. Special care has been given for the choice of the propeller to be operated in a low Reynolds number regime. Differences between on design and off- desgin conditions have been remarked. Finally, a mathematical model of the aircraft has been developed, assuming the body as rigid and considering the presence of added masses which become relevant for this type of application.