IMPROVED PROPELLANT LOADING STRATEGY AND LAUNCH OPERATION OF HYDRAZINE PROPULSION SUBSYSTEM TO ENHANCE SAFETY OF SOLAR SYNCHRONOUS ORBIT SATELLITE

摘要

Hydrazine, a widely used monopropellant in spacecraft propulsion system, has the inherent disadvantage in application for its flammability, toxic and explosive characteristics. To enhance the ground and launch safety of SSO satellite with monopropellant propulsion subsystem, an improved propellant loading strategy and launch operation procedure of propulsion subsystem was designed and validated by hot firing both in atmosphere and vacuum vessel. The propellant hydrazine are loaded upstream of latch valves of propulsion subsystem and fill the pipelines downstream of latch valve with helium of appropriate pressure. After propellant filling, the operation of latch valves and thruster valves were prohibited by electrical protection until satellite separation with launch vehicle, then the latch valve were opened according to schedule and propulsion subsystem was activated. Another advantage of this method is the propellant pressure growth phenomenon with temperature rise downstream of latch valve before separation could be eliminated.The simulated propellant prime tests and hot firing had indicated that the risk of rapid compression detonation of hydrazine and water hammer pressure peak during propellant prime process were eliminated, the delay time of thruster impulse response for attitude control is too short to be a problem.