Thrust stand for high-power electric propulsion devices

Abstract

A thrust stand for use with magnetoplasmadynamic (MPD) thrusters operated at powers up to 250 kW steady state has been built and tested. The stand was based on an inverted pendulum configuration which resulted in large displacements and high resolution. Up to 50 mm of deflection was observed under a force of 5 N. This large range of displacement significantly reduced the effects of facility induced vibrations on thrust measurements. A remotely operated system was provided for in situ calibration of the thrust stand prior to and immediately after data were obtained. Calibrations showed that thrust measurements were linear and repeatable to within a fraction of 1%. Structural distortions of the vacuum facility due to pumpdown were detected with an inclinometer located in the thrust stand base. Slope deviations as small as 10 arcsec could be compensated using a remotely controlled leveling motor. Early problems with magnetically induced tares caused by the thruster discharge current were reduced by rerouting high-current cables to decrease stray fields. Tares due to discharge current were on the order of 26 mN at 3000 A, and those due to an applied field current were 63 mN at 1400 A. The thrust stand was used with a water-cooled, applied field, steady-state MPD device at power levels up to 125 kW. Hot thruster firings as long as 1 h were performed. By precisely maintaining a level thrust stand base, thermal drift was held to about 2% of the full scale reading over this period. The remaining thermal drift could be subtracted from the thrust measurement to further reduce systematic error. Tares caused by the applied magnetic field were similarly removed. By subtracting tabulated discharge current magnetic tares, thrust measurement uncertainty was reduced to approximately 2% of the measured value.

Dynamic Measurements of Impulses Generated by the Separation of Adhered Bodies under Near-Zero Gravity Conditions

“…Precise measurement of small impulses performed by other authors [8][9][10][11] resulted critical, mainly for two reasons. Firstly, the force impulse needs to be entirely converted into momentum; therefore, any other force acting in the same direction on the body subjected to the impulse must be minimized.…”

Gaseous plume flows in space propulsion

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One Micro-thrust Measurement Method Based on the Acoustoelastic Theory

“…Meanwhile, by providing a train of small, discrete impulse bits, micro-thrusters are ideal for such diverse applications as orbit raising, drag makeup, attitude control, constellation station keeping and deep-space missions. Micro-thrusters are especially well-suited for low-thrust, on-board propulsion because they use a non-toxic propellant and are highly reliable, solid-state, low power, and lightweight, as they require no propellant storage system [1].…”