Abstract: To analyze the feasibility of high pressure working medium-based catapults，an interior ballistic model is constructed based on the Soave-Redlich-Kwong equation of state，and an one-dimensional isentropic nozzle model considering real gas effect is introduced．Using experimental data of nozzle mass flow rate and calculation results from relevant literature，the interior ballistic model is validated．Based on validation and simulation，a multi-objective optimization model is developed and solved by using a genetic algorithm．The results show that the missile catapult based on high pressure working medium can meet the given launch requirements．The interior ballistic model is less sensitive to time step，and the ideal gas and real gas models yield significantly different results．Compared with specific reference conditions，the optimized mass of working medium is reduced by 32. 2% ，and the energy utilization rate is increased by 49. 52%．The research results can provide theoretical reference for designing high pressure working medium-based catapults．

Key words: high pressure working medium, interior ballistics model, real gas effect, multi-objective optimization