Research On Safety Characteristics Of HAN-based Liquid Monopropellant

Liquid monopropellant was widely used in aviation and aerospace field, due to its high activity, high sensitivity to the shock wave, temperature and other external stimuli. There exists a high risk during its storage, transportation and usage. In order to evaluate the safety characteristics of liquid monopropellant, the basic physicochemical properties, thermal safety and sensitivity of the typical HAN-based liquid monopropellant were studied. The main contents are as follows:Flash point, ignition point and combustion energies were measured by Miniflash FLP, SYP1001B-Ⅱ ignition tester and oxygen bomb calorimeter respectively. The results showed that Flash point, ignition point and combustion heat were 62.2℃,75.5℃ and 13606J/g respectively. Liquid monopropellant was flammable liquid; its fire hazardous category was assigned in class C.In order to evaluate the thermal safety of HAN-based liquid monopropellant, its thermal decomposition characteristics were studied by DSC, ARC and slow heating test. The onset decomposition temperature of propellant were 185.73℃,227.20℃,230.37℃ and 245.19℃ in different heating rate of 2 K/min,5 K/min,10 K/min and 20 K/min respectively in DSC test and the activation energy of thermal decomposition was 181.80 kJ/mol according to Kissinger method; Whilst in ARC test, in the adiabatic environment, the onset decomposition temperature was 180.58℃, the maximum temperature rise rate was 0.6237℃/min, the adiabatic temperature rise was 227.92℃, the maximum temperature was 408.50℃ and the calculated result of activation energy and SADT were 121.77kJ/mol and 130.5℃. In addition, the results of the slowing-heating test showed that the vehement exothermal reaction and deflagration were happened when ambient temperature was up to 131.5℃.Thermal sensitivity of HAN-based liquid monopropellant was studied by 5s explosion temperature test. The experimental results indicated that 5 s explosion temperature was 284.6℃ and the activation energy of heat explosion was 115.8 kJ/mol. The United Nations gap test and larger size gap test were used to study the shock-wave sensitivity, and the results showed that the detonation of HAN-based liquid monopropellant could not happen. And, the bullet impact experiment results indicated that HAN-based liquid monopropellant was sensitive to the impact of the bullet and the longer the distance of the bullet flying in the sample, the easier the explosion of the sample.