Thrust stand based on a single point load cell for impulse measurements from plasma thrusters.

Area of Science:

• Spacecraft Propulsion
• Experimental Measurement Techniques
• Microthrust Measurement

Background:

• Accurate measurement of thrust from small electric propulsion systems is crucial for in-space applications.
• Existing methods may not be suitable for the low thrust levels (millinewton range) and environmental conditions (vacuum, plasma) of these thrusters.

Purpose of the Study:

• To introduce and validate a simple, cost-effective thrust stand for direct measurement of millinewton impulses from small in-space electric propulsion thrusters.
• To characterize the performance and calibration of the developed thrust stand.

Main Methods:

• A novel thrust stand design utilizing a strain gauge cell to measure overweight, with physical protection from vacuum and plasma.
• Calibration procedures involving control weights to verify dynamic response (0-15 mN) and determine minimum thrust sensitivity (δTs = 0.3 mN).
• Testing under low pressure and plasma conditions.

Main Results:

• The thrust stand provides ten thrust readings per second with low noise (0.10-0.18 mN peak-to-peak).
• Demonstrated accuracy in measuring steady impulses from the Alternative Low Power Hybrid Ion Engine (ALPHIE) within the 0.4-4.0 mN range, with absolute errors of ±0.3 mN.
• Confirmed that control electric voltage governs the ALPHIE thruster throttle.

Conclusions:

• The developed thrust stand offers a simple, reliable method for measuring millinewton thrust levels in relevant space conditions.
• The system allows for straightforward data reduction and analysis of steady-state and transient thrust behaviors.
• The findings validate the ALPHIE thruster's throttle control mechanism via electric voltage.