Mapping of temperature impacts for the RQ-20 PUMA AE military unmanned aerial vehicle - Kartlegging av temperaturpåvirkninger for det militære ubemannede luftfartøyet RQ-20 PUMA AE
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Abstract Thermal management of military electronics is a considerable engineering and operational challenge as technological development leads to higher heat generation and the use of electronics increases in all types of military equipment. In addition, military technology must perform reliably while exposed to external stress such as shocks, temperature and dust. Battery driven Small Unmanned Aerial Systems (SUAS), such as the AeroVironment RQ-20 PUMA AE, are no exception, the information it gathers may be of critical value to troops on the ground. Insufficient thermal management performance of the Air Vehicle (AV) may restrict the system operators ability to execute missions in extreme temperatures, thus limiting their combat effectiveness. In extreme cases, this may inhibit gathering of potentially lifesaving information. The thesis addresses this thermal management issue by performing a detailed performance mapping of the avionics thermal management system. Relevant results are also converted into thermal management aids and guidelines for system operators that may increase their operational reliability and flexibility. Analysis of AV thermal management and overheating mechanisms shows potential consequences of insufficient cooling and effects on mission execution. Overheating of the avionics poses the biggest threat. The vertically finned, direct air thermal management system of the avionics is investigated by laboratory experiments and simulations, and evaluation of avionics thermal status in various scenarios is performed. Impacts of ambient properties such as temperature, pressure and incoming solar radiation are evaluated as well. By applying laboratory and simulation results, thermal management performance maps for the entire operating range (the span of ambient properties that the RQ-20 PUMA AE AV may operate within, including temperature and altitude) are produced. Results reveal that avionics thermal management performance is insufficient for natural convection scenarios when ambient temperatures exceed 40 °C, noticeably lower than the upper limit of 50 °C given by the manufacturer. In extreme cases, overheating may occur between 20 and 30 °C. Similar mappings are not publicly available, though several military technologies use similar thermal management technologies. The results may increase knowledge and understanding about thermal management performance, mechanisms and challenges. Military technology manufacturers may use this to improve future SUAS AVs and other defense technologies. Thus, the thesis may contribute to solving parts of the military technology thermal management issue.