LIFE ASSESSMENT OF A MINIATURE MICROWAVE-FREQUENCY ION THRUSTER
Open Access
- Author:
- Hsieh, Sang Chieh
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 20, 2018
- Committee Members:
- Michael Matthew Micci, Thesis Advisor/Co-Advisor
- Keywords:
- Space Propulsion
Electric Propulsion
Rocket Propulsion
Plasma Propulsion
Ion Thruster
Microwave Thruster
CubeSats
Life Assessment
Grid Erosion - Abstract:
- This thesis presents an assessment of grid life for the Miniature Microwave-Frequency Ion Thruster (MMIT), which is being developed at The Pennsylvania State University. The MMIT is proposed mainly for use in station keeping, modest delta-V maneuvers, and attitude control on small satellites. Previous research on the MMIT developed a working prototype that demonstrated plasma generation, plasma sustainment, and ion beam extraction. The iterative development process has incrementally improved the MMIT. Findings from previous research on the arcing and sputtering of the grids drove us to establish a new design criterion for grid life. The main failure criterion for the grids depends on the mass loss of the grid. Research on the thruster life can be divided into three parts: predicting the life of the grids, determination of the variables in the life equation, and proposing new design criteria based on the life assessment. We focus on studying the effective variables in the life prediction. Experimental data show the deformation of the grid caused by arcing and sputtering. The voltage difference between the grids serves to throttle the thruster and is the driver for sputtering. The influence of hole diameter and voltage on the life equation helps us understand how the arcing and sputtering affect life. Based on other research in the literature, we define a new parameter for the MMIT. The correlation between hole diameter, acceleration voltage, and thrust gives us a new perspective on the grid design. Previous research designed the grid based on the thrust requirement alone. However, the grid life is also one of many aspects to consider. The findings on the hole diameter and grid material with propellant lead to new design criteria. The fully functional flight version of the thruster should combine the previous design standard and new design guidelines.