Effect of pressure on the burning surface temperature of a polymeric fuel for a solid propellant

Abstract

The relationship between the burning surface temperature and the regression rate of a polymeric fuel used in a solid rocket has been studied. The values of the surface activation energies derived from the Arrhenius pyrolysis equation for a polymeric fuel are not consistent and, from past studies, have been in the range 20 to 400 kJ/mol. Furthermore, the pressure dependence on the burning surface temperature has previously not been discussed in any detail. Hydroxyl-terminated polyester (HTPE) was chosen in this study as a typical polymeric fuel, along withprepolymer HTPE and glycerin. The burning surface temperature was determined using a thermocouple embedded in the specimen. The burning surface was simultaneously observed using a video camera to detect when the thermocouple emerged from the burning surface. Furthermore, the boiling phenomena of HTPE and glycerin were also examined, and thermogravimetric analysis (TGA) of the samples was also employed. As a result, the regression rate was found not to affect the burning surface temperature in the range of 0.04–0.12 mm/s, and the curing agent did not influence the burning surface temperature. On the other hand, the burning surface temperature was dependent on pressure, even in the polymeric fuel. For HTPE and glycerin, the pressure dependency obtained by the combustion experiment agreed well with those obtained by the boiling experiment and by the thermochemical method, TGA.