Research on the Impact of Laboratory Testing Conditions on the Operating Parameters of the ST-25 Hall Effect Motor

The object of the study was the Hall-effect thruster ST-25, developed by Flight Control LLC (Ukraine), with a discharge power limit of up to 200 W. This research focused on examining the influence of residual gas pressure in various vacuum chambers on the operational characteristics of this thruster. The chambers had different volumes and were made of different materials. To achieve this, the main parameters of the ST-25 thruster were determined in three vacuum chambers of varying sizes with different levels of residual gas pressure. Laboratory experiments allowed obtaining volt-ampere characteristics of the thruster discharge at fixed levels of xenon gas flow rate, with thrust values recorded. The volt-ampere characteristics show that the average discharge current remains almost unchanged and is determined by the magnitude of the working gas flow rate into the thruster’s anode block. Dependencies of the thruster thrust on the mass flow rates of the working gas at fixed levels of discharge voltage were obtained from the results of experimental measurements. Based on the experimental data, dependencies of the specific impulse of the thruster’s anode block on the discharge voltage, as well as dependencies of the anode block efficiency on the discharge voltage, were calculated. The research demonstrated that reducing the residual gas pressure in the vacuum chamber by 2-3 times increases the main operational parameters of the thruster by 15-20%. Such a reduction in residual gas pressure contributes to an increase in thrust by 25-40%. The obtained results are important as they establish critical values of residual gas pressure in vacuum chambers during experiments where the operational parameters of the Hall-effect thruster are similar to those in space. These findings can be useful for conducting practical tests of electric rocket engines when it is necessary to evaluate the operational parameters of Hall-effect thrusters in real space conditions.