Torsional thrust balance for electric propulsion application with electrostatic calibration device

Abstract

A direct measurement torsional thrust balance for electric thrusters has been developed to test pulsed plasma thrusters (PPTs) and other electric thrusters. The current configuration is able to measure impulse bits between 14 and 79 μN · s with a resolution of 0.05 to 0.10 μN · s. The direct measurement technique, in which the thruster is mounted on the thrust balance, is considered the most suitable and accurate for applications with PPTs. The use of flexural pivots with low stiffness makes the balance compact, with a smaller torsional arm. An electrostatic calibration device (ECD) was designed and built to calibrate the thrust balance, simulate the thrust of PPTs, and to allow forthcoming tests of the double discharge pulsed plasma thrusters developed at the Associated Laboratory of Combustion and Propulsion of the Brazilian National Institute for Space Research at the Electric Space Propulsion Laboratory. The maximum impulse bit measurement error achieved was as low as 10%, lower than the average of 12%–15%, typical for this type of thrust balance. The ECD was calibrated using a previously calibrated precision analytic scale. The ECD then can carry this calibration traceability to the thrust balance, providing a higher level of accuracy.