A thrust stand with adjustable stiffness for micro thrust measurement

Micro thrusters play a crucial role in satellite orbit correction and attitude control. Given their low thrust, reducing the stiffness of the thrust stand is often required to enhance resolution. However, since the thrust typically ranges from micronewtons to several millinewtons, a thrust stand with fixed stiffness is insufficient to meet the demands. The trade-off between high resolution and wide range remains a key challenge in ground testing of thruster. Therefore, an efficient stiffness adjustment method is proposed by introducing the negative restoring moment of extension spring. Tests show that the stiffness of the stand can be continuously adjusted from 19.71 to 1.28 N/m. The models of nonlinearity and fixed-end offset of spring are established to evaluate their impact on the results. Performance validation using electrostatic force show that the thrust stand achieves a resolution better than 0.5 μN while extending the range to 3346.4 μN. The thrust of the micro-Hall thruster was tested at various flow and discharge voltages based on this thrust stand. The uncertainty evaluation of the stand shows that the expanded uncertainty is better than 2.0% when thrust is 73.55 μN. This study is significant for optimizing the resolution and range of force sensors.