Interlaboratory validation of a hanging pendulum thrust balance for electric propulsion testing

Area of Science:

• Aerospace Engineering
• Space Propulsion Systems
• Experimental Measurement Techniques

Background:

• Accurate thrust measurement is critical for the development and validation of electric and chemical micro-propulsion systems.
• Existing methods may lack the sensitivity or range required for characterizing low-thrust devices.
• The European Space Agency (ESA) and Imperial College London collaborated to address this need.

Purpose of the Study:

• To develop and validate a novel hanging pendulum thrust balance.
• To characterize a wide range of static fire electric propulsion and chemical micro-propulsion devices.
• To ensure high accuracy and stability in thrust measurements, particularly for low-thrust applications.

Main Methods:

• A pendulum platform suspended by stainless steel flexures was utilized.
• Optical laser triangulation sensors measured platform displacement.
• Closed-loop heating systems ensured thermal stability, while voice coil actuators and servomotor pulley systems provided calibration traceability.

Main Results:

• Two identical thrust balances were constructed and tested at Imperial College London and ESA.
• Both balances demonstrated high linearity (0.5 mN-100 mN) and stable calibration over several days.
• Standard deviation on thrust measurements was better than 0.27 mN for low thrust levels.

Conclusions:

• The developed thrust balance is a reliable instrument for characterizing micro-propulsion devices.
• The system offers high precision and stability, suitable for demanding space propulsion research.
• Testing with a Quad Confinement Thruster (QCT) Phoenix variant validated the balance's performance, measuring thrust up to 2.21 ± 0.22 mN.