The construction of the life prediction model of 1N and 4N monopropellant thrusters

Abstract

The monopropellant hydrazine thruster is widely used in many satellites and explorers propulsion system and launch vehicle RCS due to its simplicity, high reliability, and robustness. The life of monopropellant hydrazine thruster is mainly determined by the degradation of catalyst granules. The void of the catalyst bed causes the thruster performance degradation and this trend strongly depends on the firing mode. To collect the quantitative performance degradation trend, such as thrust, specific impulse, impulse bit, and centroid time delay, the endurance firing tests were conducted with 1N and 4N thrusters. From these collected data, the life prediction models of 1N and 4N thruster were constructed. The life endurance and the performance degradation trends of thrusters can be estimated from its firing mode using this model. I. The life of monopropellant hydrazine thrustersONOPROPELLANT hydrazine thrusters are widely used in many satellites and explorers propulsion system and launch vehicle RCS due to its simplicity, high reliability, and robustness. The thrust range is mainly 1-100N and the 1N and 4N thrusters are the work horses in the monopropellant thruster family, since they are suitable for attitude control or orbit control of the satellite. As 1N and 4N thrusters are relatively small range of monopropellant hydrazine thrusters, they are useful for delicate control of spacecraft.The life of the monopropellant hydrazine thruster is mainly determined by the degradation of catalyst granules. A monopropellant thruster consists of a propellant valve which controls the propellant flow, and a jet motor which decomposes the liquid propellant to high temperature gas. The chamber in the jet motor is filled with catalyst granules which decompose propellant. As thruster are fired, the catalyst granules in the chamber are crushed into fine particles by many factors such as thermal cycle by firing, hydrazine fluid friction, and the pressure spike in the chamber[1]. The crushed fine particles are then flown downstream and some particles go out through the thruster nozzle and some are remained in the chamber and are accumulated between the catalyst granules. These are the reasons why a void of the catalyst bed is generated after firing and why the degradation of thrust increases due to the pressure drop in the catalyst bed. The void of the catalyst bed causes the thruster performance degradation and the trend of it strongly depends on its firing mode. Previously, although it was known that the long cycle period and the long ON time of the firing mode had relatively severe effect to the catalyst granules, there were not enough quantitative data of the relationship between the firing mode and the catalyst degradation and performance degradation trend.After the firing modes of thrusters are designed by a satellite system manufacturer, endurance life firing tests are often conducted to evaluate the endurance capability of the thruster life. The firing mode requirement of the thruster loaded onto the satellite is different from...