Correlation between Density of Reentry Plasma and Frequency of Attenuated Electromagnetic Signals Based on Laboratory Measurements

Abstract

Upon reentering the Earth’s atmosphere from space, a reentry vehicle becomes enshrouded in an ionization layer. This layer is known as the reentry plasma sheath and is caused by aerodynamic heating. Owing to the oscillation of charged particles in the reentry plasma sheath, the electromagnetic waves for communication between the vehicle and ground are attenuated. Analysis of the plasma density and attenuation of electromagnetic waves in a reentry plasma environment would require experimentation in an environment in which an actual aircraft reenters the atmosphere. Alternatively, an experiment in a large-scale plasma wind tunnel would be necessary. Unfortunately, these experiments would be extremely costly. Therefore, in this study, the reentry plasma was reproduced at laboratory scale using the hot refractory anode vacuum arc (HRAVA) method. In addition, the pressure in the vacuum chamber was used as a variable to probe the characteristics of the reentry plasma according to the altitude. The plasma density and attenuation of electromagnetic waves propagating through the plasma medium were measured using heterodyne interferometry and reflectometry capable of frequency analysis in the range of 10−35 GHz. The results confirmed that the plasma density and attenuation of the electromagnetic waves increased as the pressure in the vacuum chamber increased.