The burning rate of AP/HTPB composite propellant increases with increasing AP content and with decreasing AP size. In addition, the burning rate can be enhanced with the addition of Fe2O3. The burning characteristics and thermal decomposition behavior of AP/HTPB composite propellant using coarse and fine AP particles with and without Fe2O3 at various AP contents were investigated to obtain an exhaustive set of data. As the AP content decreased, the burning rate decreased and the propellants containing less than a certain AP content self‐quenched or did not ignite. The self‐quenched combustion began at both lower and higher pressures. The lower limit of AP content to burn the propellant with coarse AP was lower than that with fine AP. The lower limit of AP content to burn was decreased by the addition of Fe2O3. The thermal decomposition behavior of propellants prepared with 20–80 % AP was investigated. The decrease in the peak temperature of the exothermic decomposition suggested an increased burning rate. However, a quantitative relationship between the thermochemical behavior and the burning characteristics, such as the burning rate and the lower limit of AP content to burn, could not be determined.

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Fine porous and hollow ammonium perchlorate (AP) particles were prepared by the spray‐drying method. Propellants prepared with porous or hollow AP were found to have bubble contamination. The bubble in the propellant appeared inside the porous and hollow AP particles because the voids in porous and hollow AP cannot be completely filled with HTPB. The relationship between the burning rate and the weight mean diameter, Dw, and the specific surface area, Sw, is divided into two regions. The burning rate was almost constant above the critical Dw and increased with decreasing Dw below that. The burning rate was almost constant below the critical Sw and increased with increasing Sw above that. These critical points did not depend on the voids in the AP particles. The burning rate of the propellant prepared with spherical AP was dependent on Dw and Sw. The burning rates of the propellants prepared with porous or hollow AP were not associated with Dw or Sw alone and were greater than that of the propellant prepared with spherical AP at a constant Dw or Sw. The voids in porous and hollow AP particles thus had a positive effect on the burning rate.

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Polytetrahydrofuran (PTHF) is an effective binder ingredient for improving propellant performance, even though it is not an energetic material. PTHF becomes sufficiently rubbery for use as a binder when a triol material such as glycerin is added as a crosslinking modifier. The cured PTHF/glycerin binder had unsatisfactory mechanical characteristics for use as a propellant binder, so a more appropriate crosslinking modifier than glycerin needs to be found. In this study, glycerol propoxylate (GPO), with a molecular weight of 260, was used as a crosslinking modifier, and the curing behavior, tensile properties, and thermal decomposition behaviors of the PTHF binder using GPO were investigated. The PTHF/GPO blend did not solidify when the PTHF/GPO mole ratio (ξ) was greater than a certain value. The PTHF (Mn=650)/GPO blend with ξ≤5 and the PTHF (Mn=1400)/GPO blend with ξ≤3 were used as propellant binders. From the curing behaviors and tensile properties, it was found that the PTHF/GPO binders ensured optimal mixing of the propellant ingredients and casting of the uncured propellant into the rocket motor case, and the tensile properties of the binders changed more drastically with the variation in ξ than did those of the PTHF/glycerin binders. The thermal decomposition behaviors of the PTHF/GPO binders were hardly dependent on ξ and were almost identical to those of the PTHF/glycerin binders.

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is found to be 4 %. The increasing ratio with x is virtually independent of the burning pressure and the AN content. However, the pressure exponent unfortunately increased by addition of MnO 2 . The apparent activation energy of the thermal decomposition for AN and the propellant is decreased by addition of MnO 2 . From thermal decomposition kinetics it was found that MnO 2 could accelerate the thermal decomposition reaction of AN in the condensed phase, and therefore, the burning characteristics of the AN-based propellant are improved.

Ammonium nitrate (AN)‐based composite propellants have attracted a considerable amount of attention because of the clean burning nature of AN as an oxidizer. However, such propellants have several disadvantages such as poor ignition and a low burning rate. In this study, the burning characteristics of AN‐based propellants supplemented with Fe2O3 as a burning catalyst were investigated. The addition of Fe2O3 is known to improve the ignitability at low pressure. Fe2O3 addition also increases the burning rate, while the pressure exponent generally decreases. The increasing ratio (R) of the burning rate of the AN/Fe2O3 propellant to that of the corresponding AN propellant vs. the amount of Fe2O3 added (ξ) depends on the burning pressure and AN content. R decreases at threshold value of ξ. The most effective value of ξ for increasing the burning rate was found to be 4 % for the propellant at 80 % AN, and the value generally decreased with decreasing AN content. According to thermal decomposition kinetics, Fe2O3 accelerates the reactions of AN and binder decomposition gases in the condensed‐ and/or gas‐phase reaction zones. The burning characteristics of the AN‐based propellant were improved by combining catalysts with differing catalytic mechanisms instead of supplementing the propellant with a single catalyst owing to the multiplicative effect of the former.