Development and experimental validation of a two-axis thrust stand for the characterization of electric thruster thrust vectoring

A two-axis thrust stand is developed and validated experimentally, enabling direct and simultaneous measurements of two components of the thrust vector of an electric thruster. It is made of two piled-up single-axis stages, each having a hanging deformable parallelogram geometry. A mass deposition calibration method is used to calibrate the thrust stand, including crosstalk between axes. A new methodology is implemented to assess the gap between the theoretical angular resolution and uncertainty and the measured experimental uncertainty. From the measurement of the thrust resolution of each axis, a theoretical angular resolution of 0.1° is estimated for total thrusts above 645 μN and for thrust angles within a 10° half-angle cone. A theoretical uncertainty of 0.2° is estimated prior to thrust vectoring tests, done with a rotating cold gas thruster pointing at known operating angles between -15° and +15° and for total thrusts ranging from 235 to 7711 μN. The difference between the measured thrust angle and the operating angle evolves linearly with the operating angle. Gas tubing deformation, lower platform rotation, or incorrect crosstalk correction are potential origins of this systematic error and are responsible for the current experimental uncertainties of 0.7° at total thrusts below 630 μN and of 1.2° at higher thrusts. With further improvements, the 0.2° theoretical uncertainty could be achieved at a total thrust above 250 μN. Finally, the instrument demonstrates an efficient mitigation of the thermal and magnetic effects of an ECR thruster, paving the way for the characterization of electric thrusters.