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The Direct Simulation Monte Carlo method (DSMC) is utilized in this study to investigate the flowfield surrounding the spike-aerodisk without and with an opposing jet under rarefied hypersonic conditions within near space (altitudes of 60∼90 km and Mach numbers 7∼20). As the flight altitude increases, the incoming flow gradually becomes rarefied, weakening the drag reduction effect of the spike-aerodisk model. At altitudes reaching 90 km, the spike-aerodisk loses its drag reduction effect due to the increasing proportion of the viscous drag coefficient. At a flight altitude of 70 km, as flight Mach numbers increase, the drag reduction and thermal protection performance of the spike-aerodisk remains unchanged, mainly demonstrating the excellent performance of the spike-aerodisk model at high Mach numbers. However, the peak wall heat flux coefficient on the aerodisk can be 4.8 times higher than on the blunt body. Therefore, an opposing jet is introduced to protect the spike-aerodisk from overheating and further improve the spike-aerodisk's drag and heat reduction efficiency. Within the investigated parameter range, when the opposing-jet pressure ratio is 0.02, the peak wall heat flux coefficient of the aerodisk can decrease from 0.58 to a level similar to that of the blunt body, approximately 0.12. To make the aerodisk more certain from overheating, choosing the opposing-jet pressure ratio of 0.08 can improve drag reduction and heat prevention on the blunt body by 60.9 % and 59.7 %, respectively, compared to the spike-aerodisk model without an opposing jet. [ABSTRACT FROM AUTHOR]

The foldable unmanned aerial vehicle can reduce the storage space and improve the platform adaptability. However, the conventional foldable wing aircraft is configured with a low aspect ratio, which leads to a high aerodynamic drag and limited flight endurance. In this study, a foldable wing unmanned aircraft that can increase its wingspan to improve aerodynamic performance and flight endurance is proposed. The aerodynamic characteristics and flight performance of the aircraft is evaluated using the computational fluid dynamic method. The numerical results show that the increased wingspan can effectively decrease the wingtip vorticity and aerodynamic drag. The fully-extended wing configuration achieves a lift-to-drag ratio of 16.72, which results in an increase of 36.94% than that of the non-extended wing. The flight endurance and range of the fully-extended wing configuration are 3.81 hour and 249.89 km, respectively, which creates 86.22% more endurance and 36.88% more range than the non-extended wing. To validate the feasibility of the proposed concept, a flight test was carried out and the flight performance was obtained from flight control system. The flight data corrects well with the numerical results, which proves the effectiveness and feasibility of the variable span-morphing wing in improving flight performance for unmanned aircraft. [ABSTRACT FROM AUTHOR]