Study Of Iodine Cusped Filed Thruster

Rapid advancements of micro satellites put higher demands for propellants.Compared with traditional xenon stored in high pressure,iodine can be stored in solid,which can decrease mass of storage system.Furthermore,iodine is cheaper than xenon,which can decrease launch cost.Therefore,study of iodine cusped field thruster is of great importance.To obtain the distribution of plasma parameters,a one dimensional fluid model suitable for iodine is built.The model can be simplified to one dimension along the two typical electron paths and considers seven reactions including ionization process of I and I₂ and charge exchange process.The plasma parameters distribution can be obtained by this model.Besides,simulation results show that reaction strength of ionization process of I and I₂ and dissociation process of I₂ is higher and have dominant influence on physical process in iodine cusped field thruster.Simulation results show that acceleration region of iodine cusped field thruster is located at the exit which is similar with that of xenon.However,main ionization region moves downwards of channel,which may be related with dissociation process of I₂.It can be analyzed from simulation results that there are obvious difference of ionization process between xenon and iodine cusped field thruster.Therefore,a one dimensional fluid model is used to study influence of magnetic configuration?magnetic mirror effect and magnetic strength?,structural parameters?channel length?,work conditions and leak electron proportions on ionization strength and ionization region position in iodine cusped field thruster.It can be concluded that the main difference between xenon and iodine iodine cusped field thruster is due to dissociation process of iodine.These studies are helpful to understand ionization mechanism,design of magnetic configuration and structural parameters selection of iodine cusped field thruster.After obtaining plasma parameters distribution of iodine cusped field thruster,the compatibility test is done between iodine gas and usual spacecraft materials.Then based on the compatibility test results the storage system and vacuum system are built to do experiments of iodine cusped field thruster.Preliminary experimental results validate the reliability of experimental system.However,there are also many problems including low vacuum degree,inconvenience of dismantling of iodine tank and difficulty of seal.Therefore,a new vacuum system including 24L/S high power mechanical pump as front pump and oil diffusion pump as main pump is built to replace previous 2L/S mechanical pump vacuum system.Furthermore,the stainless steel iodine tank with jacket seal is used to replace the original silica glass tank,which solves the problem that the silica glass is easy to break and the system of iodine tank is difficult to disassemble every time.Finally,a larger silica tank adopting flange seal method is redesigned.It not only increases the space of the experiments but also solves the problem of concentric bolt penetration difficulty before.Iodine is solid at ordinary temperature.It can enter into channel to discharge after sublimation.Therefore,the whole pipeline needs to do temperature design and adopts PID temperature controller to realize temperature control.Besides,iodine gas is hot and corrosive,which prevent use of conventional flowmeter.Therefore,iodine flux is controlled by heat throttling tube and calibrated by Ar.After solving these two problems,previous experimental platform is used to do iodine cusped field thruster ignition test.Therefore volt-ampere characteristic curve of iodine cusped field thruster can be further obtained.