Comparison of Electrostatic Fins with Piezoelectric Impact Hammer Techniques to Extend Impulse Calibration Range of a Torsional Thrust Stand (Preprint)

With growing interest and development of large pulsed plasma electric propulsion devices, it has become necessary to accurately measure their thruster performance. Direct thrust measurements are the best way to measure the impulse of a propulsion device which requires it to be mounted entirely on the thrust stand. In many cases this means the thrust stand must support 10 to 100's of kilograms and still be able to resolve mNs worth of impulse. With the development of this new class of thrust stand, an accurate and repeatable method of calibration is needed. Two such calibration methods have been examined and compared. Electrostatic fin (ESF) and piezoelectric impact hammer (PIH) calibration systems were simultaneously tested on a large scale torsional thrust stand system. The use of these two methods allowed the stand to be calibrated over four orders of magnitude, from 0.01mNs to 750mNs. The ESF system produced linear results within 0.52% from 0.01mNs to 12mNs, while the PIH system extended this calibration range from 1mNs to 750mNs with an error of 0.99%. These two calibration methods also agreed within 4.51% over their overlapping range of 10 to 20 mNs.
Prepared in collaboration with Univ. of Southern California. For publication in American Institute of Physics: Review of Scientific Instruments: Apr 2011