Liquid Bismuth-fed Ion Propulsion Engines: Construction Methodology for a New Type of Mass-flow Sensor
The purpose of this research is to establish a design concept for construction of a new type of mass-flow sensor for the measurement of mass-flow rate for a liquid bismuth-fed, plasma (or Hall) thruster. The difficulty of handling the harsh environment of measuring liquid bismuth metal; and the necessity of high accuracy measurements of very low mass-flow rates preclude the use of current sensing technology. The high temperature environment- coupled with electrical conductivity constraints- requires the use of advanced materials (such as advanced ceramics and refractory metal alloys) for the flow chamber and sensor body components. To meet the needs of the current application, it was necessary to test materials in order to determine the feasibility of use with liquid bismuth. The original design (patented by Dr. Kurt Polzin, of NASA's Marshal Space Flight Center, et al.) was a single, solid-body, sensor made of an easily machine able type of ceramic. The solid-body method proved problematic; therefore, a new segmented-body design was developed in 3D CAD software to allow for a multi-stage method of hardware placement. The new design calls for the body to be made in two halves which allows the placement of elements to be precise and controlled.