Burning characteristics of Dihydroxyglyoxime based composite propellant

Abstract

An optimized engine start procedure is critical to the successful operation of a liquid rocket engine in launch vehicles. A solid propellant gas generator (SPGG) is widely adopted for the turbine starter during engine startup, and ammonium nitrate (AN) and ammonium perchlorate (AP)-based propellants are conventionally used for this purpose. However, these propellants have shortcomings such as high flame temperature, corrosive combustion residues, and low ignitability. In this study, a dihydroxyglyoxime (DHG)-based composite propellant was applied to overcome these limitations of conventional SPGG propellants. In particular, DHG, known as a coolant, was used in significant quantities as the main oxidizer for turbine starter. The burning rate, characteristic velocity, and combustion temperature of the DHG propellant were evaluated using motor tests. DHG-based propellant burns 3 – 11% slower in motor firing test than that in the strand burner due to endothermic decomposition reaction. Increasing the finer particles in the DHG propellant lead to an increased the burning rate and burning rate factor (ratio between the measured burn rate in the motor and the predicted rate by strand burner) was decreased. The temperature sensitivity of the burning rate factor was in the range of 0.23 – 0.24 % per °C. The pressure sensitivity of characteristic velocity was in the range of 0.48 – 0.50 % per MPa, and the value was approximately 4 times larger than that obtained by the CEA analysis. The performance of the actual turbine starter was accurately determined using the strand burner test results by exploiting the actual evaluation curves and correction factors. The results related to the combustion characteristics of the DHG-based propellant enabled the accurate prediction of the motor using internal ballistic analysis.