Proposal of specific impulse prediction method for bipropellant thrusters

For attitude control and orbital transfer of satellites, bipropellant thrusters are crucial components in space propulsion systems. The overall performance of the thruster is evaluated by the specific impulse (I_SP), which directly determines the lifetime and propellant mass of satellites. Therefore, in the present study, a new theoretical framework is firstly proposed to predict I_SP directly from injection conditions and nozzle configurations by considering the distribution of mixture and mass flow rates in the thrust chamber. As the performance index of the combustion chamber, the characteristic velocity is formulated. The frozen flow assumption is applied to the nozzle internal flow to calculate the thrust coefficient. The analytical results of I_SP are compared to the corresponding combustion test of a 10 N bipropellant thruster using a propellant combination of mixed nitrogen oxides with 3% nitric oxide and monomethyl hydrazine, which validates the prediction model proposed.