A newly designed decoupling method for micro-Newton thrust measurement

Abstract

A decoupling method is proposed for micro-Newton thrust measurement with a torsion pendulum. The basic approach is to reduce the influences introduced by the propellant tube and wires of the thruster. A hollow aluminum tube is used to hang the torsion pendulum and is also chosen as the transport pipe for the propellant of the thruster. The electric control box of the thruster is mounted on the pendulum body, which is powered by an externally installed power supply through a liquid metal conductive unit. The control of the electric control box is performed through wireless transmission. With this design, the influences of the propellant tube and connection wires between the torsion pendulum and the outside device are reduced and the stability of the torsion spring constant of the system can be improved. The use of the liquid metal conductive unit reduces the coupling between the wires and the measurement system. The feasibility of the wireless transmission is analyzed. The error sources during the thrust measurement are analyzed, and the expected three σ uncertainty of the thrust is [Formula: see text]N for the measurement of the cold gas thruster. The scheme provides a thrust measurement with higher precision and stability.

Microgravity Decoupling in Torsion Pendulum for Enhanced Micro-Newton Thrust Measurement

“…Ground calibration of micro-thrusters often involves using a torsion pendulum to achieve stable measurements. However, achieving stability at low frequencies below 0.1 µN/Hz 1/2 (1 mHz) remains a significant challenge due to factors like ground vibrations, temperature fluctuations, and air disturbances [6,7]. Traditional ground calibration of propulsion systems involves using precision thrust stands equipped with high-precision sensors and data acquisition systems to capture and analyze thrust output [8].…”

“…To minimize this effect, it is advisable to position the center of mass near the axis of rotation and reduce external vibration. Manuel et al [6] proposed a torsional balance to characterize micro-Newton thrusters. The arm rotates around the axis defined by two aligned flexural pivots attached to both the arm and the frame, whose inclination is adjusted with two stepper motors, making it possible to test thrust noise below 0.1 µN/Hz 1/2 above 7 mHz.…”