Vladimir Kim

Main Physical Features and Processes Determining the Performance of Stationary Plasma Thrusters

The main physical features and processes determining stationary plasma thrusters (SPTs) performance levels are considered in this paper, including ionization processes and ion dynamics in the accelerating channel, as well as the results of SPT design optimization, factors determining SPT lifetime, and the possibilities of simulating the plasma particle dynamics in the accelerating channel and in its plume.

Local Plasma Parameter Measurements by Nearwall Probes Inside the SPT Accelerating Channel Under Thruster Operation with Kr

Last years there were restarted studies of the SPT performance and operation with different gases in several Russian institutes including RIAME MAI in order to find more cheap than Xe propellant for SPT. These studies have shown that operating with Kr and Kr/Xe mixtures with low fraction of Xe it is possible to obtain thrust efficiency of SPT over 50% under increased by 1,5-2 times discharge powers (relative to Xe case) and increased specific impulses. Such level of output parameters could be acceptable for some missions. Therefore it is interesting to study the SPT operation on these gases more detaily. In particular it is interesting to realize comparative study of the local plasma parameter distributions inside the accelerating channel under thruster operation with Kr and Xe. Such measurements were made inside the accelerating channel of the SPT-100 scale thruster by nearwall probes. Obtained results show that plasma potential and ion current density distributions are similar for Xe and Kr cases under close discharge currents (that is under increased mass flow rates in the Xe case). Under close mass flow rates the accelerating layer in a Kr case is more wide and shifted inside channel. The electron temperature distribution in a Kr case is more wide and has lower maximum than in Xe case. These results could be used for the analysis of particularities of the SPT operation with different gases.

Investigation of Operation and Characteristics of Small SPT With Discharge Chamber Walls Made of Different Ceramics

Abstract : This study characterizes the SPT-25 model with discharge chamber walls made of different materials, including the Russian BN-SiO2-type (BGP) ceramics and the AIN-BN-type and BN-type ceramics produced in France and in the United States, respectively. The first ceramic is used in modern SPT-70 and SPT-100 flight designs and the others are prospective materials for SPT discharge chamber manufacturing. These materials have good thermal resistance and, according to published data, they have different secondary electron emissions. Characterization of thrusters with discharge chamber walls made of these materials could give some indication of secondary electron emission influence on thruster operation and performance. The SPT-25 model has an external accelerating channel diameter of 25 millimeters and an acceptable performance level under discharge powers (100-200)W. To characterize its operation with discharge chamber walls made of different ceramics the authors determined the voltage-current characteristics of this model under different magnetic fields inside the accelerating channel and different mass flow rates through the channel. They also determined thrust values and other output parameters such as thrust efficiency and specific impulse, accelerated ion flow divergence, plume plasma parameters measured by cylindrical electrostatic probe, discharge voltage, and current oscillation characteristics. The results confirm a high performance level by the SPT-25 model with BGP ceramics. Total thrust efficiency was ^0,25 and specific impulse ^885s under power ^100W, and total thrust efficiency was ^0,32 and specific impulse ^1300s under power ^200W. Also, there were notable differences in voltage-current characteristics and thrust values for different ceramics under low mass flow rates and magnetic fields. Moreover, thrust and thrust efficiency were different with different materials even under similar discharge voltages and currents obtained under comparable conditions.7

Investigation of the anode configuration influence on the PPS-1350 laboratory model plume divergence

Results of experimental study of Stationary Plasma Thruster (SPT) performance improvement possibility by choice of the appropriate anode design are represented in a report. In particular more attention was paid to the thruster plume divergence reduction problem. This study was fulfilled to support the Societe Europeence de Propulsion and Fakel Design Bureau joint SPT development of PPS-1350 type. In the frames of this study there was developed, manufactured and tested the PPS-1350 laboratory model with anodes of several configurations under typical for this thruster operation modes. For more full investigation there were studied the possibility to adjust magnetic field topology for the chosen anode configurations, an impact of internal accelerating channel geometry adaptation (change) at the beginning of thruster life and an impact of the accelerating chamber erosion after the thruster long time operation. As results of study it is shown that anode designs used in a modern SPTs and in a PPS-1350 design give the best results and that magnetic field topology adjustment with additional magnetization coils introduced into PPS-1350 design could be used to maintain high level of the thruster performance including its plume divergence through the thruster life.

OVERVIEW OF RUSSIAN EP ACTIVITIES

This overview prepared by the group of leading Russian experts in the research, development and application of electric propulsion represents a summary of the efforts made in Russia under the Federal space program and international projects within last 1-2 years. A new geosat Express# 4 manufactured by NPO PM has joined a family of the SPTpropelled spacecrafts and now is in operational use. The T-120 Hall thruster produced by KeRC has passed through flight verification onboard this satellite. Several Russian enterprises develop the small spacecraft to be propelled by elt-ltric thrusters of Hall or PPT typ. There is a brmd spcrtrum of new Hall thruWrs revarch and dcvelnpmcnt in Russia. The efforts were made by DB Fakel, RIAME MA1 and MEREA to evaluate the SPT operated on alternate propellants such as Xe-Kr mixture and Kr. Significant steps have been made in further investigation of working parameters of SPTs and TALs operated under increased discharge voltages directed toward the development of viable high-lsp propulsion. Preliminary study of the 3-TAL engine cluster performances has been completed at TsNIIMASH. Further characterization of the Hall thruster plumes in RIAME MAI, MA1 and TSNIIMASH enabled the adjustment of existing plume models and their comparison with experimental results obtained in ground and flirht conditions. Thr development of computer codes enabling the thruster lifetime prediction along with experimental verification of accelerated wear test methodologies is in focus of MA1 and TSNllMASH research group activity. Earlier demonstrated possibility of the Hall thruster erosion rate evaluation through analysis its optical emissions has been confirmed in the recent TAL tests and provided excellent coincidence with direct wear measurements. A few electric propulsion facilities are now under reconstruction in Russia being prepared for complex tests of different electric thrusters and plume interaction issues study.