Multiple Reflection Theory for Microwave Measurement of Solid Propellant Burning Rates,
VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG
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Microwaves reflected from the regressing burning surface of solid propellants carry information which can be extracted to yield the local burning rate of the propellant. The signal is complex, with multiple reflections arising from each material interface in the path of the microwaves, including the propellant-combustion zone interface. It is shown that certain otherwise fixed microwave reflections within a slab propellant burner acquire a changing phase shift through interaction with the moving propellant combustion surface. The effect of this interaction on the burning rate measurement is studied through the use of computer simulation in several examples. Requirements are assessed for more complex models of microwave reflections for burning rate measurement in solid propellants.