High precision micro-impulse measurements for micro-thrusters based on torsional pendulum and sympathetic resonance techniques

Abstract

A sympathetic resonance theory is analyzed and applied in a newly developed torsional pendulum to measure the micro-impulse produced by a μN s-class ablative pulsed plasma thruster. According to theoretical analysis on the dynamical behaviors of a torsional pendulum, the resonance amplification effect of micro-signals is presented. In addition, a new micro-impulse measurement method based on sympathetic resonance theory is proposed as an improvement of the original single pulse measurement method. In contrast with the single pulse measurement method, the advantages of sympathetic resonance method are significant. First, because of the magnification of vibration signals due to resonance processes, measurement precision for the sympathetic resonance method becomes higher especially in reducing reading error. With an increase in peak number, the relative errors induced by readout of voltage signals decrease to approximately ±1.9% for the sympathetic resonance mode, whereas the relative error in single pulse mode is estimated as ±13.4%. Besides, by using the resonance amplification effect the sympathetic resonance method makes it possible to measure an extremely low-impulse beyond the resolution of a thrust stand without redesigning or purchasing a new one. Moreover, because of the simple operational principle and structure the sympathetic resonance method is much more convenient and inexpensive to be implemented than other high-precision methods. Finally, the sympathetic resonance measurement method can also be applied in other thrust stands to improve further the ability to measure the low-impulse bits.

MOFs for Ultrahigh Efficiency Pulsed Laser Micropropulsion

“…The torsion pendulum method, a commonly used technique was employed to comprehensively compare and quantify the LMP performance parameters of different materials. [25,[51][52][53][54] The experimental setup and working principle of the torsion pendulum measuring system are depicted in Figure 3A. The measurements were conducted under vacuum conditions, with the vacuum box evacuated to 15 kPa.…”

Impulse Measurement Methods for Space Micro-Propulsion Systems

“…Assume that the wall thickness of the C-shaped tube is t, the length is l, the length of the cross-section centerline is m, the material shear modulus of elasticity is G, the rotational inertia of the torsion pendulum relative to the axis of the C-shaped tube is I, the impulse generated by the propulsion system is micro I s , and the instantaneous rotational angular velocity of the torsion pendulum beam is w. When the torque T is loaded on the C-shaped tube, the torsional deformation generated is [31]:…”

“…where α is the torsion angle of the C-shaped pipe under the action of torque. By integrating formula (1), the rotation angle of the C-tube torsion beam can be obtained α 0 , and its stored energy is [31]:…”

Theoretical Modeling and Parameter Analysis of Micro-Pulsed Plasma Thruster

“…This paper adopts the torsional pendulum built in [33] to measure the impulse bit. A photograph and schematic illustration of the thrust stand are shown in Figure 6.…”

“…Under the range of the torsional pendulum, the maximum deviation from the balance position of the laser spot on the PSD is proportional to the impulse value of the arm. Thus, the impulse of the thruster can be calculated as well [33]. The electronic balance was used to calculate the ablation mass.…”