Inverse venting problem for estimation of the discharge coefficient in a satellite launch vehicle

Abstract The pressure variation inside the heat shield of a satellite launch vehicle during ascent flight through the atmosphere induces structure load. If the depressurization of air is not rapid or appropriate, excessive pressure loading can cause structural failure of the heat shield or malfunctioning of the electronic devices of the satellite. The pressure inside the heat shield compartment is generally computed numerically by solving a compressible and isentropic flow equation using knowledge of the discharge coefficient as a function of Mach number. The pressure difference between the inside and outside of the compartment is then evaluated using the atmospheric pressure as a function of the altitude. In this paper, an inverse venting problem for estimation of the discharge coefficient is presented using measured internal pressure inside a compartment during the ascent flight of a satellite launch vehicle. The discharge coefficients are estimated using the Newton-Raphson method and a direct-search procedure utilizing pseudo-random numbers. It is found that the estimated discharge coefficient is dependent on the flight Mach number of the vehicle.