In vacuum dynamic and static tests of a thrust balance for electric propulsion with hysteresis analysis and behaviour prediction with transfer function

Abstract

This work describes the advances on the development of a thrust-stand for electric propulsion application with a focus on the constraints of the two-stage pulsed plasma thruster (TS-PPT) being developed at INPE at the Electric Propulsion Laboratory (LPEL) of the Laboratory of Combustion and Propulsion (LABCP). While previous work on this instrument focused on basic development in atmospheric pressure the present effort presents the development undertaken to elevate the TRL of the device to allow it to operate in vacuum—the environment where actual electric thrusters operate and are tested. To cater for INPE’s TS-PPT specification, standard masses summing 1.2 kg were used while the electrostatic calibration device (ECD) was set to produce 31 μNs. A detailed hysteresis analysis was carried out at the target TS-PPT specification together with a transfer function that aimed at extrapolating and predicting the behaviour of the instrument. In addition, this work shows the development of a new magnetic damper for the instrument that reduces the waiting time between tests. A new calibration at the TS-PPT specification points were undertaken in vacuum since previous calibration were made for atmospheric pressure and did not include the specific points of interest for the TS-PPT. Furthermore, previous calibration procedures were verified to ensure they would apply to the vacuum conditions and to account for the substitution of some thrust stand previously incompatible vacuum parts and also to account for the addition of the new magnetic damper and other unforeseen conditions caused by the vacuum environment.

Thrust Measurements of the Rit-10 Thruster With a New Type of Thrust Balance

“…It can be seen, that for the middle weight, the value for increasing weights is higher than for decreasing weights. This is likely a hysteresis effect (Junge, 1964;Soares and Marques, 2021) of the balance and has to be studied more detailed in the future. Still, the deviation is within 3% of the calibration force.…”

“…Using this set of equations, the response of the thrust balance due to impulsive or permanent loads can be solved analytically, neglecting non-linear effects such as hysteresis, which is commonly reported for pendulum type thrust balance (Junge, 1964;Soares and Marques, 2021). The steady state solution is found by Eq.…”