Experimental Investigation on Microwave Interference in Full-Scale Solid Rocket Exhaust

摘要

Under certain conditions during rocket flight, ionized exhaust plumes fromsolid rocketmotorsmay interfere withnRF transmission. To understand the relevant physical processes involved in this phenomenon, measurement ofnmicrowave attenuation and phase delay caused by rocket exhaust plumeswas attempted in a sea-level static firing testnfor a full-scale solid propellant rocketmotor. Themeasured data were analyzed by comparing themwith simulationnresults for an exhaust plume flowfield. The results revealed that the change in the shock structure in the plume affectsnthemicrowave attenuation level, since it significantly affects the plasma density at themeasuring location.When thenplasma density in the plume is low, the microwaves can penetrate the plume. The plume plasma properties werensuccessfully estimated for that situation in which the numerically calculated attenuation level agreed well with thenexperimental results. On the other hand, high-density plasma in the plume does not allow penetration. Therefore,nmicrowaves bypass around the plume and the diffraction effect becomes dominant.