Design and Experimental Investigation of a Micronewton Thrust Balance

Paper number

IAC-05-C4.P.15

Author

Mr. Klaus Marhold, ARC Seibersdorf research, Austria

Year

2005

Abstract

Thrust measurements are an essential part in the characterization and qualification process to evaluate the performance of electric propulsion devices. For this purpose a direct thrust measurement system for electric thrusters operating in the micronewton thrust range has been designed. Prior to the design a review of different
systems for thrust balances has been conducted. Thrust stands in operation at ESA and NASA as well as various companies and academical institutions have been evaluated in regard to their size, accuracy, cost, maximum allowable thruster mass and scalability. After this review it was concluded to develop a thrust stand based on a torsional balance design, due to its simplicity and accuracy. Another aspect was
that this is a well known design which has been proven in a variety of thrust balances operating in the micronewton range. Additionally it can also be adapted to allow measurements of higher thrust devices like clusters of Field Emission Electric Propulsion (FEEP) or colloid emitters e.g. the new In-FEEP cluster currently under development at ARC Seibersdorf research for the LISA pathfinder mission. The balance consists of a symmetric arm able to rotate by the means of two flexural pivots. The thruster is mounted to one end of the arm, while on the other end counterweights are mounted. The linear displacement of the arm, which is a function of the applied thrust, is precisely measured using a fiber optic displacement sensor. An electrical damping system consisting of a pair of electrostatic comb actuators is
employed to reduce oscillations of the arm, while a second pair is used for the calibration of the balance. This, together with an innovative design of the electric connections to the thruster, enables measurements with low noise and high accuracy. In this paper the design of the thrust stand as well as first measurements with an Indium Field Emission Electric Propulsion (In-FEEP) thruster will be
presented.

Abstract document

IAC-05-C4.P.15.pdf

Manuscript document

IAC-05-C4.P.15.pdf (🔒 authorized access only).

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