担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Physics  

To achieve high-thrust-density operation, we propose electrostatic-magnetic hybrid ion acceleration in which the empirical thrust density limit of the electrostatic acceleration is surpassed without violent plasma oscillation by combing the collisional momentum transfer mechanism, which is the ion acceleration mechanism of the electromagnetic acceleration. To achieve hybrid ion acceleration, we experimentally obtained two design criteria: one near anode propellant injection and another at the on-axis hollow cathode location. The thrust characteristics of three thrusters composed of a slowly diverging magnetic field between an on-axis hollow cathode and a coaxially set ring anode were examined. By injecting xenon propellant along the anode inner surface, the electron impact ionization process was enhanced, and generated ions are electrostatically accelerated through the radial-inward potential gradient perpendicular to the axial magnetic lines of force. The hybrid ion acceleration characteristics were obtained only if these two criteria were satisfied and the obtained thrust was consistent with the thrust formula derived for steady-state, quasi-neutral plasma flows. In addition to the criteria, strengthening the magnetic field and enhancing the propellant mass flux were effective for improving thrust density without deteriorating thrust efficiency. Among the experimental conditions in this study, the maximum thrust density was 70 N/m2 with an anode specific impulse of 1200 s, which cannot be achieved in a purely electrostatic thruster with thrust density 6.3 times than that of a typical Hall thruster.

DOI： 10.1063/5.0066083

Web of Science

Scopus

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AIP Advances  

We evaluate the energy conversion efficiency of an electrical exploding foil accelerator that accelerates a thin dielectric foil (called the flyer) to more than 1 km/s, which is propelled by electrically exploded bridge material. The effective flyer mass ejected from the accelerator is estimated by impulse measurements obtained using a gravity pendulum as well as by time-resolving flyer velocity measurements obtained using a photonic Doppler velocimetry system. For two different bridge sizes (0.2 and 0.4 mm), the flyer velocity and impulse increase with the input energy at the bridge section. The maximum flyer velocity and impulse, that is, 4.0 km/s and 67 µN s, respectively, are obtained by supplying 0.33 J of input energy. Upon increasing the input energy, the effective flyer mass also increases and exceeds the designed-bridge mass for both bridge sizes. The energy conversion efficiency from input electrical energy to flyer kinetic energy is calculated based on the effective flyer mass, velocity, and input energy. Both bridge sizes show comparable efficiencies: 27% and 30% for 0.2 and 0.4 mm bridges, respectively. The efficiency increases with increasing specific input energy at least up to 15 MJ/kg for the 0.4 mm bridge, whereas the efficiency of the 0.2 mm bridge above 30 MJ/kg decreases. This is owing to the excessively high input energy density in the 0.2 mm bridge, which causes the effective flyer mass to increase by including surrounding materials. These results indicate that the specific input energy should be optimized for obtaining maximum efficiency.

DOI： 10.1063/5.0061699

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Scopus

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Propulsion and Power  

DOI： 10.2514/1.B38480

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Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2514/1.B37636

Web of Science

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Propulsion and Power  

In this study, an electrostatic thruster was newly developed, in which a diverging magnetic field with a cusp around a cathode was applied by using two solenoid coils. The effects of the magnetic field strength on thrust performance under a similar applied-magnetic-field configuration were investigated. Because of its light weight and lower price, argon was used as a propellant. By increasing the magnetic field strength, the thrust efficiency was improved owing to the suppression of the discharge current while an almost constant thrust was maintained. A specific impulse of 3800 s with thrust efficiency greater than 30% was obtained; the corresponding mass-averaged exhaust velocity exceeded the value by full-potential electrostatic acceleration of singly charged ions. From the thrust performance, ion beam current, and ion energy distribution function that were experimentally measured under the representative operation condition, 32% of the ion beam current and 43% of the total thrust were evaluated as the contribution of doubly charged ions.

DOI： 10.2514/1.B37675

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Scopus

担当区分：責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Transactions of the Japan Society for Aeronautical and Space Sciences  

DOI： 10.2322/tjsass.63.109

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Scopus

CiNii Research

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Propulsion and Power  

In a study, researchers present the results for a newly developed DM-EST, in which only permanent magnets and yokes are used to apply an external magnetic field, and we examine its thrust performance by using the monoatomic species argon, krypton, and xenon. A pendulum-type thrust stand with a 300-mm-long stand arm supported by a two-knife-edge fulcrum was used to measure the thrust. Each knife edge was mounted on a V-shaped groove with an opening angle of 120 degree. Each groove was formed by two blocks made of stainless steel 316 so that the bottom was not rounded. The displacement of the pendulum was measured by a laser displacement sensor at the tip of the aluminum extension arm, where the distance from the fulcrum was 128 mm. The sensitivity of the thrust stand was calibrated in the range of up to 54 mN using a pulley and weight arrangement driven by a direct-current motor at the same ambient pressure as during the thruster operations. The thrust measurement uncertainty was 2.7% of the minimum thrust value measured in this study.

DOI： 10.2514/1.B37294

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Scopus

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Acta Astronautica  

The thrust characteristics of electrostatic-magnetic hybrid acceleration have been obtained in the central–cathode electrostatic thruster (CC-EST), which has a diverging magnetic nozzle and injects propellant through an annular slit on the inner surface of a ring anode. The electrostatic and electromagnetic contributions are evaluated by fitting experimentally measured thrust characteristics to formulae derived for steady-state, quasi-neutral plasma flows. The thrust is composed of two terms: one corresponds to the electrostatic acceleration interfaced by the magnetized electrons, the other to electromagnetic acceleration yielding a kinetic energy of swirl motion that is converted to that of axial motion in the diverging magnetic nozzle. The thrust performances of three thrusters having an axisymmetric shape with a hollow cathode on the centre axis and a diverging, applied magnetic field are examined. While only an electromagnetic thrust component is obtained in the conventional applied-field magneto-plasma-dynamics thruster, the other two, CC–ESTs, exhibit comparable, electrostatic and electromagnetic thrust components, and thus improve thrust performance.

DOI： 10.1016/j.actaastro.2018.07.052

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Scopus

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.4995286

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.actaastro.2017.06.032

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Propulsion and Power  

In this paper, applied-field magnetoplasmadynamic thrusters were operated with a discharge current lower than 20 A and an argon propellant flow rate under 4.0 mg/s by using a thermionic electron emission-type hollow cathode. Both axisymmetric and rectangular channel configurations were examined. The characteristic value of the ratio of the applied-field electromagnetic thrust to the self-field electromagnetic thrust, which was a maximum of approximately 50 in previous research, increased to more than 800 in this study, whereas the specific power was in approximately the same range as in previous studies. The trends of thrust and discharge voltage were explained by referring to the "swirl acceleration" model. Such operation could be useful for near-future high-power electric propulsion applications.

DOI： 10.2514/1.B36179

Web of Science

Scopus

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.4960363

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1109/TPS.2016.2522079

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2322/jjsass.63.37

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Hyogo-Kobe, Japan   国名：日本国  

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Hyogo-Kobe   国名：日本国  

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Hyogo-Kobe,   国名：日本国  

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Hyogo-Kobe   国名：日本国  

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Georgia Institute of Technology  

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：JAXA宇宙科学研究所  

推進機上流部の陽極と下流部の陰極との間に，永久磁石により生成した発散磁場を有する静電加速機Diverging magnetic field electrostatic thruster (DM-EST)を試作した．スラストスタンドにより推力を直接計測し，それに基づき推力性能を評価したので本講演ではその結果を報告する．

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Georgia Institute of Technology