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Drag-free technology functions as the keystone for space-based gravitational wave detection satellites moving along a geodesic path, like the Laser Interferometer Space Antenna (LISA) Pathfinder, to achieve ultra-high microgravity level. Several prerequisites for micro-thrusters operated under the drag-free technique include constantly adjustable thrust, high resolution, low noise and fast response time. Accordingly, a torsional thrust measurement system was methodically devised to measure the thrust response time of such micro-thrusters on the ground. The characteristics of the dynamic thrust change with time are inverted by the angular displacement of the torsional pendulum, established by the dynamic equation of the same, thus, measuring the rise/fall time of the thrust applied to the torsional pendulum. Calibration of the torsional pendulum thrust measurement system is carried out by the standard electrostatic force generated by the electrostatic comb-drive or microelectromechanical actuator, facilitating the suitable identification of the pendulum parameters. Afterwards, the electrostatic and electromagnetic forces generated by the actuator are applied to validate the measurable thrust response time of the torsional thrust stand. The experimental results show that the above-mentioned thrust stand can effectively measure the thrust response time up to 10 ms for a thrust step in 10 s of micronewtons, which qualifies as the thrust response time required by micro-thrusters for space-based gravitational wave detection. [ABSTRACT FROM AUTHOR]

Abstract: A miniature thrust stand in man-made vacuum environment, based on the principle of leaf spring bending deformation, capable of supporting testing of thrusters having a total mass of up to 300 g and producing thrust levels between 1 μN and 760 μN has been developed and tested. A case-study measurement was conducted for a Colloid Micro-Newton Thruster (CMNT) to investigate the feasibility of the proposed system under vacuum conditions. Displacement of the leaf spring deforming was measured using a linear capacitive displacement sensor (LCDS). An in situ calibration rig allows for steady-state calibration before, during and after thruster operation. To validate this method, extensive thrust measurements were carried out on a colloid thruster that produces μN magnitude level thrust under vacuum conditions. Results show that the measurements were very repeatable, producing results that compare favorably with measured data with an uncertainty of approximately 10%. [Copyright &y& Elsevier]