2.45 GHz 마이크로파 전열 추력기의 플라즈마 방전 안정화를 위한 최적설계 및 성능평가

다국어 초록 (Multilingual Abstract)

Recently, the demand for satellites has been steadily increasing as the scope of satellite missions has expanded. This trend has led to a growing need for electric thrusters that combine a simple structure with high reliability for satellite applications. Among various electric thrusters, the MET (Microwave Electro-thermal Thruster) offers a simple structure, long mission life span, and outstanding operational flexibility. In this study, an experimental apparatus for plasma discharge experiments was constructed and a MET was designed and fabricated as part of the development of a 2.45 GHz MET. Plasma discharge experiments were conducted using this MET by varying the design variables, and optimal operating conditions were derived by evaluating the performance based on the measured data. The experimental apparatus consisted of a microwave source and a waveguide system, which was configured to minimize microwave losses and reflected waves with consideration of electromagnetic performance parameters. The MET was preliminarily designed to resonate at 2.45 GHz in TMz 011 mode. However, the resonant frequency of the fabricated cavity deviated from the output frequency band of the microwave source. This resulted in unstable plasma discharge, low pressure gain, and low coupling efficiency during preliminary experiments. From these results, the actual material properties of the design variables were back-calculated, and the cavity was redesigned. The MET was then successfully fabricated with its resonant frequency matched to the output frequency band of microwave source. The plasma discharge experiments were conducted on the MET using argon as the propellant, while varying input power and propellant mass flow rate for different nozzle throat diameters. The results showed that, for all nozzles, the plasma discharge mode tended to transition from glow discharge to filamentary discharge as the mass flow rate increased, and this transition caused an increase in the pressure gain. In particular, a strong and stable plume related to the plasma discharge characteristics was observed under certain experimental conditions in filamentary discharge mode. Based on these experimental results, the performance of the MET was evaluated to derive the optimal operating conditions.

목차 (Table of Contents)

• Ⅰ. 서 론 1
• 1. 연구배경 1
• 2. 연구현황 및 목적 5
• Ⅱ. 이론적 배경 8
• 1. 마이크로파 개념 및 전송선로 8
• 2. 마이크로파 전열 추력기의 구조 및 작동 원리 12
• 3. 플라즈마 정의 및 방전 원리 16
• 4. 마이크로파 전열 추력기의 성능 지표 21
• Ⅲ. 실험 장치 및 방법 23
• 1. 실험 장치 23
• 1.1 마이크로파 공급 및 전송 23
• 1.2 데이터 획득 28
• 2. 실험 방법 30
• 2.1 Cold-flow test 30
• 2.2 플라즈마 방전 실험 31
• Ⅳ. 2.45 GHz 마이크로파 전열 추력기 예비 설계 및 실험 33
• 1. 마이크로파 전열 추력기 예비 설계 및 검증 33
• 2. 실험 조건 36
• 3. 실험 결과 및 고찰 37
• Ⅴ. 노즐 목 직경 변화에 따른 플라즈마 방전 특성 40
• 1. 마이크로파 전열 추력기 재설계 및 검증 40
• 2. 실험 조건 42
• 3. 실험 결과 및 고찰 43
• Ⅵ. 결 론 54