The 250mN Thrust Balance for the DLR Goettingen EP Test Facility

Abstract

The German Aerospace Center DLR brought into operation a test facility for electric space propulsion in Goettingen, Germany, called STG-ET. This facility has been especially designed for electric propulsion with a vacuum chamber that measures more than 12m in length and 5m in diameter. Besides thruster performance tests the focus is on plume interaction with spacecraft components and on long-term testing. Thrust measurement is a fundamental measurement method for propulsion engine qualification. Ion and Hall effect space thrusters usually produce thrust levels in the milli-Newton range, and thrust balances have to deal with these low values. For the thrust balance of the STG-ET we adopted a thrust balance design based on a counter-balanced, electromagnetic force compensated device. The measurable thrust range is 250mN, but the design can easily accommodate an upgrade to 1N. The maximum allowed thruster assembly mass is 40kg. Several innovative features are implemented in its design.