Thrust measurement and thrust balance development at DLR’s electric propulsion test facility

• Published in: EPJ techniques and instrumentation Vol. 8; no. 1; pp. 1 - 19
• Main Authors: Neumann, Andreas, Simon, Jens, Schmidt, Jens
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 23.11.2021; Springer Nature B.V; SpringerOpen
• Subjects: Atomic; Biological and Medical Physics; Biomaterials; Biophysics; Characterization and Evaluation of Materials; Diagnostic systems; Diagnostics for electric propulsion systems; Electric propulsion; Electric space propulsion; Gases; Ground tests; Heat; High vacuum; Low thrust; Measurement Science and Instrumentation; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Propulsion systems; Pumping; Rare gases; Research Article; Space missions; Spectroscopy and Microscopy; Test facilities; Test facility; Testing time; Thrust; Thrust balance; Thrust measurement; Thrusters; Vacuum chamber; Vacuum chambers; Thrust balance; Test facility; Electric space propulsion; Vacuum chamber
• ISSN: 2195-7045; 2195-7045
• DOI: 10.1140/epjti/s40485-021-00074-7

Electric space propulsion thrusters only produce low thrust forces. For the fulfillment of a space mission this implies long thruster runtimes, and this entails long qualification times on ground. For such long testing times, a ground facility requires a vacuum chamber and a powerful pumping system which can guarantee high vacuum over extended times and under thruster gas load. DLR’s STG-ET is such a ground test facility. It has a high pumping capability for the noble gases typically used as propellants. One basic diagnostic tool is a thrust measurement device, among various other diagnostic systems required for electric propulsion testing, e.g. beam diagnostics. At DLR we operate a thrust balance developed by the company AST with a thrust measurement range of 250 mN and capable of thruster weights up to 40 kg. Adversely, it is a bulky and heavy device and all upgrades and qualification work needs to be done in a large vacuum chamber. In order to have a smaller device at hand a second thrust stand is under development at DLR. The idea is to have a light and compact balance that could also be placed in one of the smaller DLR vacuum chambers. Furthermore, the calibration is more robust and the whole device is equipped with a watercooled housing. First tests are promising and showed a resolution well below 1 mN. In this paper we give background information about the chamber, describe the basics of thrust measurement and the development of a new balance.