Estimation of Drag Coefficient from Radar-tracked Flight Data of a Cargo Shell

Abstract

Two schemes to extract drag coefficient (C,) by processing the radar-tracked trajectories of artillery shell in motion, have been proposed. Flight trajectories of artillery shell are considered. The proposed schemes are applied on the radar-tracked trajectory data of artillery shell to estimate thc C,,. The C,, is strong function of Mach number. To capturc the functional rclationship between the C, and the Mach number, the C, of the ammunition was assumed to be a polynomial function of Mach number (separately for subsonic and supersonic). The coefficients of the assumed polynomial were estimated by minimising the error between measured and estimated trajectories. In the second scheme, whole trajectory was split into diffcrent sets containing 50 or 100 data points. Each data set was processed using the proposed schemes to estimate numerical values of C, corresponding to the average Mach number of the chosen data set. The estimated values of the C, (at different Mach numbers) have been presented along with its standard deviations. The difticulties encountered in processing the real trajectory data using the proposed schemes are also highlighted. It is observed that thc proposed schclnes could advantageously be applied to quickly estimate the numerical values of the C, at corresponding Mach numbers, by processing thc trajectory data of an artillcry shell in motion.