Study of the spike-aerodisk-opposing jet on heat protection to both the spike-aerodisk and the blunt body and overall drag reduction in rarefied hypersonic flow in near space

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.