An impulsive thrust balance for applications of micro-pulsed plasma thrusters

Abstract

This paper describes the design and testing of a direct torsional impulsive thrust balance. The design philosophy allows the balance to measure impulse bits (Ibit) in the range of 20–120 µN s typical of pulsed plasma thrusters (PPTs) for pico- and nano-satellites. The uncertainty in the Ibit measurement is quantified to be about 8.8%, smaller than the typical values of this kind of balance (between 12% and 15%). This has been possible due to an in-depth analysis of all the possible sources of disturbance, which allows the choice of the most suitable measurement and estimation methods to minimize the errors. The balance has successfully been used for testing two PPTs with different propellant feeding system, nominal energy, mass and delivered impulse bits.

Torsional thrust balance for electric propulsion application with electrostatic calibration device

“…To measure it, an optical displacement sensor was used, model D63 from Philtec. It has a very good resolution, two linear regions of operation, called near side, with higher resolution, and far side, and has been used in other thrust balance successfully [2]. Figure 5 shows the calibration curve of the optical sensor in the near side region provided by the manufacturer.…”

“…The impulse bit measurement, I bit , is a key parameter to aid calculations of thrust (T) for a given PPT operating at a certain frequency. For μPPTs (PPTs that operate with 10 W or less), the impulse bit value is approximately in the range of 20-150 μN • s. Typical torsional pendulum thrust balances can measure the impulse bit of PPTs in this range of impulse with an uncertainty in the 12%-15% range [2].…”

PPT Development for Nanosatellite Applications: Experimental Results

“…It has six CF flanges where the electrical F/Ts are installed and a 0.5-m diameter circular main port on the side surface. The vacuum chamber is evacuated by a pumping system comprised of an Edwards roughing pump and by a Pfeiffer Balzers TPH 450-H turbo molecular pump with a pumping speed of 450 l/s backed The thruster impulse bit was measured with a direct impulsive thrust balance developed in-house; a more detailed description of the balance can be found in [15]. The thruster mass consumption has been measured using a Mettler Toledo balance with an accuracy of ±5 μg and performing a minimum of 300 shots per energy level (1000 shots at energy levels below 3.5 J) achieving a measurement error of <3%.…”

Development of a Direct Thrust Balance for Low Power Hollow Cathode Thruster

“…where fs is the signal sampling frequency and P is the power of 2 closest to the number of acquired samples [10,11]. An oscilloscope with a sampling frequency of 25 kHz was used to acquire the sensor trace at every set-point for a 7 time of at least 1 minute, hence more than 2 million samples per set-point are acquired (P = 2 21 = 2,097,152).…”