The study of ignition processes of solid propellants has given useful information to define the main parameters driving the phenomenon. The experimental work ahs been performed investigating the radiant ignition transient, by a CO_2 laser system, of composite and double-base propellants and measuring the temperature of the irradiated propellant surface by microthermocouples. From the recorded temperature history it is possible to define the igntion propellant temperature and ignition delay time for the operating pressures and incident laser fluxes. Tests were performed in a pressure range from 0.05 to 10 atm for an ammonium perchlorate composite propellant and from 0.1 to 5 atm for a double base propellant. The knowledge of the dependency of propellant igntion delay time on incident laser flux intensity allows macrokinetic characteristics of the tested propellants at different pressures to be obtained. An analytical solution of one-dimensional heat conduction equations, describing the radiant heating of semitransparent propellants, with the analytical condition of ignition, were adopted. A system of equations provided the computations, by an iterative procedure, of the ignition propellant temperature and the thickness of the reaction layer with were used to obtain the surface energy activation and preexponent factor. The results, obtained by this procedure, show that the surface energy activation is generally lower than the values derived by other methods.
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