1. The ability to accurately predict, reconstruct and extrapolate internal ballistics and performance, in terms of specific and total impulse, of a solid rocket motor prior to static firing and test flight of the motor itself is of paramount importance due to the effect that analysis results can have on motor design and development.1-7In this work, the internal ballistics and performance reconstruction analysis of high performance solid rocket motors (SRMs) is carried out with a 0D quasi-steady model that is based upon an inverse and a direct approach. The inverse approach, on the one hand, relies on the static firing test measurements in order to evaluate the behavior of the motor, through the reconstruction of the non-ideal parameters: combustion efficiency, thrust efficiency, hump curve, scale factor and nozzle throat area evolution. The direct approach, on the other hand, uses the non-ideal parameters reconstructed by the inverse approach to extrapolate the motor performance in flight. The final goal is to increase the understanding of solid rocket motors behavior in terms of non-ideal parameters in order to assess the overall motor performance, to enrich the knowledge of the motor behavior, to characterize motor dispersion and scattering, and to consolidate the methodology used for the performance reconstruction and extrapolation to flight unit (FU).
2. The post-firing reconstruction model is able to assess, in the SRM quasi-steady state and tail-off phase, the actual behavior of the SRM during the firing through the evaluation of the non-ideal parameters and the nozzle throat area evolution in time based on a functional dependence of nozzle throat erosion from motor operating conditions.6,7,11-14The non-ideal parameters take into account the SRM actual behavior with respect to: i) the propellant burning rate, typically coming from small-scale single grain batch tests for propellant characterization (BARIA), and the uncertainties on the full-scale propellant grain burning surface evolution, which are taken into account through the product of the hump and scale factor;15ii) the shift of the propellant combustion products thermochemical characterization with respect to the ideal equilibrium adiabatic conditions,16considered in the combustion efficiency; iii) the thrust efficiency to characterize all the thrust losses in the nozzle expansion process, i.e. divergence, two-phase flow, boundary-layer losses and frozen flow effects. These parameters are evaluated exploiting the experimental measures occurring before, during and after the static firing test, and the reconstruction technique, along with its main assumptions and modeling parameters. The data measured before and during the static firing test regarding the motor internal ballistics are typically the following: the loaded propellant mass (from the experimental measures); the initial and final nozzle throat area value and the nozzle expansion ratio (from quality and post-firing measurements); the propellant density (from the experimental measures); the head-end pressure (from the experimental measures); the measured or reconstructed SRM thrust (from the test bench data); the propellant burning rate characterization in terms of a and n parameters of the de Saint-Robert-Vieille law (evaluated by smallscale BARIA propellant grain batch analyses). Finally, the nominal evolution of the combustion surface in the web is theoretically evaluated by grain burn-back analysis.