Realization of Long-Term Operation of Ion Engines Using Adamantane through Alternating Operation with Water or Carbon Dioxide

Abstract

The ion engine using adamantane as a propellant is hindered in its long-term operation by the generation of flakes and deposits within the discharge chamber. Although experiments with mixed gases of water or carbon dioxide were conducted to suppress flake and deposit formation, the inhibitory effect was limited. Conversely, it was discovered that alternating operation with water or carbon dioxide suppresses flake and deposit formation, enabling extended operation. To quantify the thruster performance during the alternating operation, the individual thruster performance of adamantane, water, and carbon dioxide was obtained experimentally. The performance degradation incurred in exchange for extended operation is as follows: During the alternating operation with water, the specific impulse was estimated to decrease from 3500 to 340 s, and the thrust was estimated to decrease from 930 to 200 mN. When alternating with carbon dioxide, the specific impulse and the thrust were estimated to decrease to 560 s and 170 mN, respectively. Reducing the usage of water or carbon dioxide is key to improving thruster performance.