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Experimental analysis on the measurement of ballistic properties of solid propellants

Cuerdaneli, S.
Ak, M. A.
Ulaş, Abdullah
Ballistic properties of solid propellants play an important role in the performance of the solid propellant rocket motors. Therefore, ballistic properties of a likely propellant should be known and provided to the design engineers. In this study, a specific AP/HTPB composite solid propellant (SCP) was examined to obtain steady-state linear burning rates as a function of pressure and propellant initial temperature, temperature sensitivity, and pressure deflagration limit (PDL). In some tests micro-thermocouples were embedded into the propellant samples to measure the temperature profiles in the solid, condensed, and gas-phase flame regions. From the measured profiles, burning surface temperatures were obtained and the activation energies were extracted from these data. A high-pressure strand burner was developed to perform ballistic property measurements of the SCP. Propellant samples were ignited by Ignition Wires. Experiments were performed at different pressures and temperatures to determine the ballistic properties of the propellant at different environmental conditions. Auxiliary systems such as Cryogenic Cooling System and Electrical Heating System were built to provide different environmental conditions in the strand burner. An inert gas (N 2 ) was selected for both conditioning and pressurizing the test chamber. Experiments revealed that the PDL limit for the SCP is 1 atm, which means it can burn even at atmospheric pressure. Results showed that temperature sensitivity of the SCP decreased with the increase of chamber pressure. Experiments aimed to measure burning surface temperature of the SCP did not represent reliable results due to the fact that the exact location of the burning surface could not be obtained even with fine-wire (25 mum) thermocouples.