Experimental Investigation on Electromagnetic Waves Transmitting Through Exhaust Plume: From Propagation to Channel Characteristics

Exhaust-plume-induced plasma from solid rocket engines absorbs electromagnetic (EM) waves and may cause communication interruptions. Previous articles have proposed both physical phenomena and propagation models for this problem, but few articles have analyzed random fluctuations of EM waves propagating through plumes from a communications perspective. This article attempts to attach these fluctuations, which are caused by the plume-induced turbulent plasma spread medium, to the communications channel characteristics. A multi-parameter stochastic model is established to characterize the exhaust plume channel in which the first-order and the second-order statistical properties are presented. Accordingly, a ground firing test was conducted to validate the EM wave propagation characteristics and the channel characteristics. The experimental results are in good consistence with the theoretical results. The results indicated that the time-varying envelope of the transmitted EM waves obeys a log-normal distribution, whereas the time-varying phase shift obeys a normal distribution. Moreover, the time-frequency analysis method was applied to evaluate the EM-plume interactions in the time-frequency domain. These results are critical for designing the rocket communication systems and evaluating the systems performance.