Design and Development of a High Precision Thrust Measurement System

One of the fundamental steps in the applications of science and technology is the measurement of physical quantities involved in those applications. The measurement of these physical quantities is, however, not always trivial. In the applications such as the calibration of femto-satellites, and micro-plasma thrusters for future space exploration missions of NASA and other technological giants, where very precise attitude and position control is required, the measurement is a key issue to be addressed. One of such applications is a low-cost thrust measurement system. This paper presents the design and development of such a system, capable of successfully measuring the thrust of magnitude less than 20 μN by utilizing the principles of optical interference. The micro newtons pulse of a short duration is applied using an electromagnetic thruster setup on the tip of a pendulum. The pendulum subsequently performs the oscillations, and then an optical interferometer is used to precisely measure the deflection of the pendulum. The maximum deflection is then calibrated to obtain the applied thrust. The pendulum is designed based on optimal geometric parameters for maximum deflection of the pendulum tip for a response of thrust lasting for 100 milliseconds. For experimental validation, the interference signal is obtained in high resolution oscilloscope, which is subsequently processed to find the precise deflection of the pendulum and thus the precise thrust. The device successfully measures a minimum thrust of 18.44 μN. The precision is restricted due to environmental conditions and is not the limitation of the device itself.