DEVELOPMENT OF A DUAL-FREQUENCY MICROWAVE BURN-RATE MEASUREMENT SYSTEM FOR SOLID ROCKET PROPELLANT

A DUAL-FREQUENCY microwave burn-rate measurement system for solid rock et motors has been developed. The system operates in the X-band (8.2-1 2.4 GHz) and uses two independent frequencies operating simultaneously to measure the instantaneous burn rate in a solid rocket motor. Compu ter simulation and limited laboratory testing of the system were perfo rmed to determine its ability to limit errors caused by secondary refl ections and by uncertainties in material properties, particularly the microwave wavelength in the propellant. Simulations showed that the fr equency ratio and the initial motor geometry determined the effectiven ess of the system in reducing secondary reflections. Overall, the simu lations showed that a dual frequency system can provide up to a 75% re duction in burn-rate error over that returned by a single-frequency sy stem. The hardware and software for dual-frequency measurements was de veloped and tested; however, further instrumentation work is required to increase the data acquisition rate so its full potential can be rea lized.