Development of a Thrust Stand Micro-Balance to Assess Micropropulsion Performance

As proposed spacecraft and their associated thrusters have become smaller, technology has been developed to meet the demand for performance measurements for the extremely low force levels produced. For such thrusters, it is also desirable to measure the mass changes resulting from the utilization of propellant associated with either the steady state thrust or transient impulses. A thrust stand and novel data analysis method is presented to make both thrust (or impulse) and mass change measurements concurrently. It is shown that very accurate and repeatable measurements of mass can me made using an existing thrust stand system. Furthermore, it is shown that impulse and mass measurements can be resolved at the same time from a single thrust stand trace. INTRODUCTION A Thrust Stand micro-Mass Balance (TSMB) has been developed to accurately measure the thrust (or impulse) and change in thruster mass as a diagnostic tool for aiding in the development of new and innovative micropropulsion systems. When looking at a thruster’s performance, the two most common parameters are thrust (T) and specific impulse (Isp). Numerous thrust stands [1-3] have been designed to obtain thrust measurements for relatively low steady-state forces or transient impulses. However Isp measurements can be more involved, and require knowledge of the mass flow rate, as given by the relation,