Mitigation of Detrimental Electric Thruster Force Measurement Effects

DLR (German Aerospace Center) operates the test facility STG-ET for electric space propulsion in Goettingen, Germany. The STG-ET has been especially designed for electric space thruster testing with a vacuum chamber that measures 12.2 m in length and 5 m in diameter. Thrust measurement is a basic requirement for propulsion engine qualification. Ion and Hall effect space thrusters usually produce thrust levels in the milli newton range. A thrust measurement system used on these engines has to carry the weight of the thrusters which are of the order of several kg and measure these low force values. Within this paper, we analyze issues when using a thrust measurement device, and give some hints on how to mitigate these. Stability of the balance carrying structure, decent cable and fluid pipe routing, and good thermal conditioning are the most important points to take care of for minimizing issues