2.45 GHz 마이크로파 전열 추력기의 플라즈마 방전 특성에 관한 Multi-physics 해석 = Multi-physics Analysis on the Plasma Discharge Characteristics in 2.45 GHz Microwave Electro-thermal Thruster

다국어 초록 (Multilingual Abstract)

With the transition toward the ‘New Space’ era, there has been a sharp increase in demand for microsatellites performing high-value missions, such as Earth observation and communication relays. To ensure precise orbit maintenance and attitude control of these satellites, highly reliable propulsion systems are essential. Among these, the Microwave Electro-thermal Thruster (MET) has gained significant attention as a next-generation alternative; its electrodeless operation fundamentally eliminates electrode erosion, ensuring high specific impulse and extended operational life. Existing MET research has primarily focused on performance verification of simplified geometries or efficiency analysis using global models. In this study, we performed geometric optimization and electromagnetic-plasma coupled analysis to maximize the performance of a 2.45 GHz MET. First, the cavity height, dielectric slab thickness and position, and antenna insertion depth were selected as key design variables to analyze their correlations with electromagnetic resonance characteristics. In particular, to ensure the reliability of the simulation model, an empirical calibration process was introduced. Material properties were inversely estimated based on VNA measurements of a fabricated cavity and fed back into the numerical model. This approach allowed for the determination of an optimal geometry that reflects actual energy losses and material characteristics, resulting in significantly improved return loss and a substantial reduction in the input power required to achieve a target electric field strength. Furthermore, the plasma discharge characteristics under various operating conditions were investigated using the calibrated model. The analysis revealed that the self-shielding effect, occurring when electron density exceeds the cutoff critical density, is a primary mechanism determining plasma localization and discharge transition. Notably, it was found that the operating pressure is a more dominant factor than input power in determining the plasma potential barrier height and energy confinement efficiency. In addition, an analysis of heating characteristics due to the skin effect physically demonstrated that the high-temperature electron generation zone and the actual gas heating zone are spatially separated. This study clearly presents the organic correlation between MET design and operational variables by combining empirically-validated model calibration with multi-physics analysis. The elucidated shielding phenomena and spatial separation of heating zones are expected to serve as critical design guidelines for maximizing energy efficiency and ensuring device durability under diverse propellant conditions in the future.

목차 (Table of Contents)

• Ⅰ. 서 론 1
• 1. 마이크로파 전열 추력기의 개요 1
• 2. 연구 동향 및 배경 4
• Ⅱ. 이론적 배경 6
• 1. TMz011 mode 6
• 2. 플라즈마 이론 9
• 2.1. 플라즈마 정의 및 특성 9
• 2.2. 기체 방전 및 전자 증폭 10
• 2.3. 마이크로파-플라즈마 상호작용 11
• Ⅲ. 공진 캐비티의 전자기 특성 해석 및 설계 최적화 12
• 1. 전자기장 모델 12
• 2. 설계 변수 및 기준 형상 정의 14
• 3. 해석 모델 및 경계 조건 16
• 4. 공진 주파수 비교 및 분석 18
• 5. 전자기장 강도 비교 및 분석 21
• 6. 공진 캐비티 설계 방안 23
• 7. 공진 캐비티 제작 및 설계 최적화 26
• Ⅳ. 플라즈마 방전 특성 해석 33
• 1. 모델 가정 33
• 2. 전자기장 모델 36
• 3. 플라즈마 모델 37
• 4. 수치해석 기법 39
• 5. 해석 모델 및 경계 조건 40
• 6. 해석 결과 43
• 6.1. 시공간적 전자 밀도의 성장 및 전이 특성 43
• 6.2. 전위 분포 및 하전 입자 수송 특성 47
• 6.3. 전기장 차폐에 따른 전력 소산 및 전자 가열 특성 50
• Ⅴ. 결 론 55
• 참고문헌 58