Dual-axis thrust stand for the direct characterization of electrospray performance

Area of Science:

• Aerospace Engineering
• Space Propulsion Systems
• Experimental Measurement Techniques

Background:

• Electrospray thrusters require precise characterization for efficient space propulsion.
• Traditional methods for measuring propellant consumption, like pre- and post-testing weighing, have limitations.
• Accurate in situ mass loss measurement is crucial for direct efficiency determination.

Purpose of the Study:

• To demonstrate a novel dual-axis torsional thrust stand for simultaneous thrust and mass loss measurement.
• To compare in situ mass loss data with traditional analytical balance measurements.
• To investigate sources of error and limitations in electrospray thruster testing.

Main Methods:

• Development and demonstration of a dual-axis torsional thrust stand with high-resolution sensors.
• Simultaneous measurement of thrust (±0.2 µN) and mass loss (±0.04 mg) during electrospray thruster operation.
• Comparison of mass consumption data from the thrust stand with analytical balance measurements over several months.

Main Results:

• The dual-axis thrust stand provided direct, simultaneous measurements of thrust and mass loss.
• Mass consumption data from the stand showed significant variation (-5% to 18%) compared to analytical balance measurements.
• Thermal drift in flex-pivot bearings was identified as a major source of error, causing spurious torques.
• Testing duration was limited by facility-induced temperature variations and thrust stand drift.

Conclusions:

• The developed dual-axis thrust stand offers a more accurate method for characterizing electrospray thrusters compared to pre/post-weighing.
• Atmospheric moisture absorption significantly impacts mass measurements when thrusters are removed from vacuum.
• Further research is needed to address thermal drift and charging effects for long-duration, stable testing.