Development of a Nano-Impulse Balance for Micropropulsion Systems

Abstract : Several versions of a torsional impulse balance have been developed as a new diagnostic tool to study fundamental physical processes in micropropulsion systems. With respect to the transfer of momentum, direct measurements of the transient forces or total impulse delivered can lead to a better understanding and characterization of the efficiency of the thrust that is possible under different configurations. The impulse balance has been designed and tested with a robust calibration system to measure steady state and impulsive forces. The behavior of the impulse balance was thoroughly studied and characterized. An analytical model of the balance's motion was developed from the general equation of motion of an underdamped, harmonically oscillating system. A simple technique has been developed to accurately back out the force as a function of time from the experimental data. The latest version of the impulse balance also manages to resolve changes in mass, which is another key parameter of propulsion efficiency. These impulse balances have been used in different configurations to study many forms of micropropulsion, including the impulses caused by laser-surface interactions and the combustion of Tanner Research, Inc. MEMS-based solid propellant motors.