Estimation of drag coefficient from radar-tracked flight data of a cargo shell

Two schemes to extract drag coefficient (C_D) 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 the C_D. The C_D is strong function of Mach number. To capture the functional relationship between the C_D and the Mach number, the C_D 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 different sets containing 50 or 100 data points. Each data set was processed using the proposed schemes to estimate numerical values of C_D corresponding to the average Mach number of the chosen data set. The estimated values of the C_D (at different Mach numbers) have been presented along with its standard deviations. The difficulties encountered in processing the real trajectory data using the proposed schemes are also highlighted. It is observed that the proposed schemes could advantageously be applied to quickly estimate the numerical values of the C_D at corresponding Mach numbers, by processing the trajectory data of an artillery shell in motion.