A numerical analysis of electromagnetic waves around the atmospheric reentry demonstrator (ARD) of the European Space Agency (ESA) in an atmospheric reentry mission was conducted. During the ARD mission, which involves a 70% scaled-down configuration capsule of the Apollo command module, radio frequency blackout and strong plasma attenuation of radio waves in communications with data relay satellites and air planes were observed. The electromagnetic interference was caused by highly dense plasma derived from a strong shock wave generated in front of the capsule because of orbital speed during reentry. In this study, the physical properties of the plasma flow in the shock layer and wake region of the ESA ARD were obtained using a computational fluid dynamics technique. Then, electromagnetic waves were expressed using a frequency-dependent finite-difference time-domain method using the plasma properties. The analysis model was validated based on experimental flight data. A comparison of the measured and predicted results showed good agreement. The distribution of charged particles around the ESA ARD and the complicated behavior of electromagnetic waves, with attenuation and reflection, are clarified in detail. It is suggested that the analysis model could be an effective tool for investigating radio frequency blackout and plasma attenuation in radio wave communication.

When a reentry vehicle enters the planetary atmosphere, a strong shock wave is generated and the strong aerodynamic heating appears. Gas temperature in front of the vehicle exceeds 10,000K and chemical reactions (ionizations and dissociations) occur behind the shock wave. Because the reentry vehicle is damaged by the aerodynamic heating, accurate evaluation of the aerodynamic heating in the high-enthalpy flow is necessary for the design and the development of the vehicle. The communication blackout phenomenon which prevents the propagation of the electromagnetic waves can occur by the characteristics of electrons in the shock layer to absorb and reflect the electromagnetic waves. To estimate the communicationable time and understand the behavior of the electromagnetic waves around the vehicle, the accurate evaluation of the plasma flow around the vehicle is also necessary. In this study, the three-dimensional numerical analysis was conducted to consider an angle of attack by using the analysis software for compressible fluid, RG-FaSTAR which has been developed by JAXA. Moreover, unstructured grids were used to make it easier to generate computational grid around the vehicle with complicated shape. Note that RG-FaSTAR is a version of FaSTAR (FaST Aerodynamic Routine) installing the real gas effect. We reproduced the actual flow field around the Atmospheric Reentry Demonstrator (ARD) which was launched by the European Space Agency (ESA) in 1998 and revealed the aerodynamic heating and plasma flow properties during atmospheric reentry. The computational result showed good agreement with measured pressure coefficient at the stagnation point. In addition, the features of the shock layer and the rear region around ARD were revealed.

Abstract. Numerical simulations of electromagnetic waves around the atmospheric reentry demonstrator (ARD) of the European