Prediction of Communication Blackout and Degradation for a Re-Entry Hypersonic Capsule Through High-Fidelity Numerical Simulations

The communication degradation and blackout phenomena are well known problems that affect Apollo-style atmospheric re-entry capsules. The phenomena is caused by the formation of a plasma sheath around the re-entry vehicle, that acts as a barrier to the electromagnetic energy across certain frequency bands typically used for communications. The ionization of the atmosphere is caused by the extremely high temperatures generated by the compression of the gases in front of the re-entry vehicle traveling at extremely high Mach number. Over the past six decades several design and operational methods have been proposed to minimize the time duration of the communication blackout period, with mixed outcomes. Key to the development of these engineering solutions is the understanding of the complex physical interactions between the flow and electromagnetic fields as well as the understanding of the effects that capsule geometry, antenna placement and trajectory profiles have on the transmission of electromagnetic energy. The present work presents a solution to this problem that enables the computation and prediction of communication blackout by tool-chaining commercially available computer simulation software. The aerothermodynamic environment, including the ionization of the air around the vehicle, is predicted using off-the-shelf CFD tools. The ionized flow field computed by the CFD solution is then passed to the electromagnetic simulation for the prediction of the antenna performance. The antenna behavior is analyzed as the vehicle moves along its re-entry trajectory, transitioning from having full radio communication capabilities to full communication blackout. JAXA’s OREX test case was chosen because of the availability of the tests results and because of the overall better quality of the flight test data as compared to other, similar flight tests. Numerical results show a close matching of the ionization trends measured in the OREX flight tests as well as the correct prediction of the onset of communication blackout. The validated tool-chaining offers a powerful numerical tool for the design and analysis of re-entry vehicles.