Realization of a High Specific-Impulse Microwave Discharge Ion Engine for Deep Space Exploration

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K20421
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0301:Mechanics of materials, production engineering, design engineering, fluid engineering, thermal engineering, mechanical dynamics, robotics, aerospace engineering, marine and maritime engineering, and related fields
• Research Institution: Japan Aerospace EXploration Agency
• Principal Investigator: Tabata Kuniyoshi 国立研究開発法人宇宙航空研究開発機構, 宇宙科学研究所, 宇宙航空プロジェクト研究員 (80963959)
• Project Period (FY): 2022-08-31 – 2024-03-31
• Keywords: 電気推進 / 高比推力 / イオンエンジン / マイクロ波放電 / DESTINY+ / はやぶさ2

Outline of Final Research Achievements

The objective of this study was to realize a high specific-impulse microwave discharge ion engine for deep space exploration beyond Jupiter. A previous study identified the instability of ion extraction at an ion acceleration voltage of 7.5 kV. This study revealed that the surface conductivity of the waveguide through which microwaves propagate significantly contributes to the instability and achieved stable operation by fine-tuning the thruster design. Consequently, a thrust of 25 mN and a specific impulse of 6,600 s were achieved. Besides, this study demonstrated that the optimal design from a long-term perspective is crucial in enhancing the ion engine system’s durability, considering the wavelength shortening effect caused by grid-derived carbon deposition on the waveguide after long-time operation.

Free Research Field

宇宙推進工学

Academic Significance and Societal Importance of the Research Achievements

本研究で実現した7 kVの高い耐電圧をもつガス絶縁器は，ホールスラスタなど他の電気推進システムにも適用可能であり，学術的価値が高い．また，長時間運転によるマイクロ波放電式イオンエンジンの比推力劣化現象の原因と対策も明らかにした．本研究により，比推力を従来の2倍以上に向上させただけでなく，その比推力を長期間維持できる解決策を提示できたことで，増速量10 km/s以上を要するミッションや，小惑星のマルチフライバイ探査など，推進剤重量の削減が鍵となる深宇宙探査ミッションに大きな貢献が期待される．