Abstract
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.
Highlights
One of the most important issues in the entry, descent and landing approach of spacecraft is radio frequency (RF) blackout; that is, the cutoff of communication between the reentry vehicle and ground stations and/or data-relay satellites
Because the plasma flow is rapidly cooled and rarefied by expansion when compressed gas in the shock layer flows toward the rear of the vehicle, propagation of electromagnetic waves is possible at the rear of the vehicle where the electron density is lower
The pressure obtained in the flight experiment is reconstructed based on the flight information on velocity and density deduced by the on-board acceleration measurement technique
Summary
One of the most important issues in the entry, descent and landing approach of spacecraft is radio frequency (RF) blackout; that is, the cutoff of communication between the reentry vehicle and ground stations and/or data-relay satellites. Because the plasma flow is rapidly cooled and rarefied by expansion when compressed gas in the shock layer flows toward the rear of the vehicle, propagation of electromagnetic waves is possible at the rear of the vehicle where the electron density is lower It was suggested by Takahashi et al [6] that an inflatable vehicle could passively reduce RF blackouts with data relay satellites during atmospheric reentry because of its low ballistic coefficient flight and distinctive vehicle configuration. Numerical prediction using high-performance computers has become a powerful tool for investigating the details of phenomena, such as flow fields or electromagnetic waves, and for the design and development of reentry vehicles. Because the ARD had a typical reentry capsule configuration and reentry trajectory, it is worth investigating further and providing the distributions of plasma and electromagnetic waves for the design and development of new reentry vehicles and for research and development concerning RF blackout mitigation techniques
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