Development of zirconium and potassium perchlorate igniter for AP/HTPB composite propellant base bleed grain

For effective and reliable ignition of ammonium perchlorate and hydroxyl-terminated polybutadiene (AP/HTPB) solid composite propellant base bleed (BB) grain a simple, reproducible and high-energy igniter composition were studied. Zirconium and potassium perchlorate (ZPP)-based compositions were developed with and without nitrocellulose (NC) lacquer as binder. The effects of different ratios of Zr/KClO4 were investigated by using fuse wire technique for burning rates, bomb calorimeter for calorific value and high-pressure closed vessel (CV) for pressure–time (P–t) curve, pressure maximum (Pmax), time to reach Pmax (tPmax), and rate of change of pressure change (dP/dt). It was observed that composition K-8 with fuel, oxidizer, and binder ratio of 1:1:0.02 gave reliable burning rate, calorific value, Pmax, and dP/dt. After careful analysis of combustion performance, composition K-8 was further investigated for burning rate and P–t data after 10 h of temperature conditioning at − 40 °C, + 21 °C and + 50 °C, respectively. Selected composition was then press-filled in specially designed steel igniter cups which were press-fitted in base bleed kit igniter bodies. Several static firings were performed by initiating igniter with electric squib for recording the burning time, igniter mass burning behavior, and reproducibility of successful ignition results. ZPP igniter was finally fitted in base bleed kit equipped with AP/HTPB composite propellant BB grain and tested on static as well as dynamic level by firing with 155-mm artillery projectile. Dynamic testing after temperature conditioning of complete projectile equipped with BB kit at + 21 °C, + 50 °C and − 40 °C for 24 h. Igniter provided successful ignition to base bleed grain until it achieved stable burning. All fired rounds achieved enhanced range of 30% approximately, with controlled uniform muzzle velocity and chamber pressure. ZPP igniter is recommended to be used for AP/HTPB solid composite propellant base bleed grain.