A momentum flux measuring instrument with the variable-range for exhaust plume

A momentum flux measuring instrument (MFMI), which ranges from 1 mN∼300 N, is designed to measure the parameters related to the momentum flux of exhaust plume of attitude and orbit control thrusters covered electric and chemical thrusters. A MFMI with the variable-range provides an efficient and economy way to study the exhaust plume of both electric and chemical thrusters. The flexural pivots, replaceable strain gauge, replaceable target plate, and force arm with the variable length make it possible. The designed MFMI with the non-displacement measurement can reduce the influence of pipelines and test lines, especially the elastic force and friction due to displacement. The designed MFMI system with the range of 0∼100 mN and 0∼15 N was calibrated separately. The target indirect measurement method is a simple and economical option for measuring the thrust of electric thrusters, and is employed to measure the thrust of the LIPS-200 ion thruster using the designed MFMI. Research indicates that the sputtering contributes to the momentum transfer of plasma-surface interactions. In addition, the high-speed charged ions from the thruster will experience a charge-exchange (CEX) collision with the slow neutral background. Therefore, the influence of the sputtering and CEX on target indirect measurement method is derived in detail, and then the measured thrust is corrected. The measured average thrust, which is 40.1 mN, demonstrates that the designed MFMI is effective. The designed MFMI can also be employed as a thrust stand by directly mounting the thrusters on torsional arm, and a maximum of three thrusters can be installed on the MFMI at the same time.