研究者業績
基本情報
- 所属
- 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 准教授
- 学位
- 博士(工学)(2013年3月 東京大学)
- 研究者番号
- 70720697
- ORCID ID
https://orcid.org/0000-0002-6265-1672- J-GLOBAL ID
- 202001010789612597
- researchmap会員ID
- R000013995
経歴
7-
2021年11月 - 現在
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2013年8月 - 2021年10月
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2016年9月 - 2017年10月
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2013年4月 - 2013年7月
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2010年4月 - 2013年3月
学歴
4-
2010年4月 - 2013年3月
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2008年4月 - 2010年3月
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2004年4月 - 2008年3月
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2000年4月 - 2003年3月
委員歴
3-
2023年4月 - 現在
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2022年4月 - 2024年3月
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2019年4月 - 2020年3月
受賞
15-
2024年5月
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2021年4月
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2020年12月
論文
72-
Journal of Applied Physics 135(24) 2024年6月27日 査読有りIonic liquid electrospray thrusters represent an alternative propulsion method for spacecraft to conventional plasma propulsion because they do not require plasma generation, which significantly increases the thrust efficiency. The porous emitter thruster has the advantages of simple propellant feeding and multi-site emissions, which miniaturize the thruster size and increase thrust. However, the multi-scale nature, that is, nano- to micrometer-sized menisci on the millimeter-size porous needle tip, makes modeling multi-site emissions difficult, and direct observation is also challenging. This paper proposes a simple model for multi-site emissions, which assumes that the ionic conductivity or ion transport in the porous media determines the ion-emission current. The conductivity was evaluated by comparing the experimental and numerical data based on the model. The results suggest that the ionic conductivity of the porous emitter is suppressed by the ion–pore wall friction stress. Additionally, the model indicates that the emission area expansion on the porous emitter creates the unique curve shape of the current vs voltage characteristics for multi-site emissions.
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AIP Advances 14(6) 2024年6月1日 査読有りAn understanding of the degradation mechanism of a microwave discharge cathode is the key to extending the lifetime of microwave ion thruster systems. This study investigates the effect of nozzle contamination by sputtered Ag-polytetrafluoroethylene (PTFE) on microwave discharge cathode performance. The current–voltage characteristics were measured for nominal and contaminated (by PTFE spray with 0.2 µm thick or tape with 0.15 mm thick) cathodes. The contamination thickness and area on the nozzle were varied to investigate the characteristic differences. It was confirmed that the anode voltage increased by 20 V or more in the case of the contaminated cathode. The anode voltage was measured for the sputter-contaminated cathode to evaluate the effect of contamination under more realistic conditions. After 630 h of sputter-contamination operation, it is estimated that sputtered particles were deposited to a thickness of 77 µm at most, and the anode voltage increased by 8 V. The results show that the downstream surface of the nozzle is critical for maintaining cathode performance. The insulating coating formed by the sputtered PTFE may interfere with ion absorption and degrade electron emission capability. A theoretical model based on the extended Brophy model supports these results. This study provides important information for the use of PTFE-based materials around ion thrusters.
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Acta Astronautica 2024年5月 査読有り
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Vacuum 220 112760-112760 2024年2月 査読有り
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Acta Astronautica 212 130-138 2023年11月 査読有り
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Journal of Evolving Space Activities 1 21 2023年6月 査読有り
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Journal of Evolving Space Activities 1 2023年4月 査読有り
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Science (New York, N.Y.) 379(6634) eabn7850 2023年2月24日 査読有りCarbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples. The samples are mainly composed of materials similar to those of carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37° ± 10°C, about [Formula: see text] million (statistical) or [Formula: see text] million (systematic) years after the formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles that of the Sun's photosphere than other natural samples do.
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Science (New York, N.Y.) 379(6634) eabo0431 2023年2月24日 査読有りThe near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth's volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measured noble gas and nitrogen isotopes in Ryugu samples and found that they are dominated by presolar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have different abundances among the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating a ~5 million year exposure, and from implanted solar wind record the recent irradiation history of Ryugu after it migrated to its current orbit.
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Science (New York, N.Y.) 379(6634) eabn9057 2023年2月24日 査読有りSamples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu's parent body.
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Science (New York, N.Y.) 379(6634) eabn9033 2023年2月24日 査読有りThe Hayabusa2 spacecraft collected samples from the surface of the carbonaceous near-Earth asteroid (162173) Ryugu and brought them to Earth. The samples were expected to contain organic molecules, which record processes that occurred in the early Solar System. We analyzed organic molecules extracted from the Ryugu surface samples. We identified a variety of molecules containing the atoms CHNOS, formed by methylation, hydration, hydroxylation, and sulfurization reactions. Amino acids, aliphatic amines, carboxylic acids, polycyclic aromatic hydrocarbons, and nitrogen-heterocyclic compounds were detected, which had properties consistent with an abiotic origin. These compounds likely arose from an aqueous reaction on Ryugu's parent body and are similar to the organics in Ivuna-type meteorites. These molecules can survive on the surfaces of asteroids and be transported throughout the Solar System.
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Nature astronomy 7(2) 170-181 2023年 査読有り
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Journal of Electric Propulsion 1(1) 2022年12月 査読有り招待有りAbstract In electron cyclotron resonance (ECR) thrusters, the plasma mode transition is a critical phenomenon because it determines the maximum thrust performance. In ECR ion thrusters, ionization generally occurs in the magnetic confinement region, where electrons are continuously heated by ECR and confined by magnetic mirrors. However, as the flow rate increases, ionization is also observed outside the magnetic confinement region, and this induces the plasma mode transition. In our previous work, two-photon absorption laser-induced fluorescence (TALIF) analysis revealed that the stepwise ionization from the metastable state plays an important role in the ionization process. However, the distribution of the stepwise ionization has not yet been revealed because of the long lifetime of the metastable state. In this study, this distribution was investigated using one experimental and two numerical approaches. First, TALIF was applied to two types of gas injection with clear differences in thrust performance and ground-state neutral density distribution. In the first simulation, the metastable state particle simulation was used to estimate the excitation rate distribution. In the second study, simulations of the electric field of microwaves were used to estimate the contribution of the stepwise ionization to the plasma density. The experimental and numerical results revealed that the stepwise ionization spreads outside the magnetic confinement region because of the diffusion of metastable particles, and this spread induces the plasma mode transition, explaining the difference between the two types of gas injection.
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Science advances 8(46) eabo7239 2022年11月18日 査読有り
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NATURE ASTRONOMY 6(10) 1163-+ 2022年10月 査読有り
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Vacuum 200 110962-110962 2022年6月 査読有り
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Science 375(6584) 1011-1016 2022年3月4日 査読有り
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Nature Astronomy 6(2) 214-220 2022年2月 査読有り
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Journal of Applied Physics 131(1) 013301-013301 2022年1月7日 査読有り招待有り
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Review of Scientific Instruments 92(12) 129902-129902 2021年12月1日 査読有り
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The Review of scientific instruments 92(11) 114501-114501 2021年11月1日 査読有り
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Investigation of plasma mode transition and hysteresis in electron cyclotron resonance ion thrustersPlasma Sources Science and Technology 30(9) 095023-095023 2021年9月1日 査読有り
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Acta Astronautica 185 179-187 2021年8月 査読有り
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Acta Astronautica 181 14-27 2021年4月 査読有り
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JOURNAL OF PROPULSION AND POWER 37(2) 223-230 2021年3月 査読有り
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TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 64(3) 189-192 2021年 査読有り
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Nature Astronomy 5(3) 246-250 2021年 査読有り
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Nature Astronomy 5(1) 39-45 2021年1月 査読有り
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Astrodynamics 4(4) 349-375 2020年12月 査読有り
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ACTA ASTRONAUTICA 176 413-423 2020年11月 査読有り
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ACTA ASTRONAUTICA 176 77-88 2020年11月 査読有り
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ACTA ASTRONAUTICA 174 367-376 2020年9月 査読有り
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JOURNAL OF PROPULSION AND POWER 36(4) 586-592 2020年7月 査読有り
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Science 368(6491) 654-659 2020年5月8日 査読有り
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Science 368(6486) 2020年4月 査読有り
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NATURE 579(7800) 518-522 2020年3月 査読有り
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TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 18(3) 57-63 2020年 査読有り<p>The authors investigate the discharge chamber of the microwave ion thruster μ10 by using kinetic particle simulation. First, to investigate the plasma phenomena qualitatively, we conduct a particle-in-cell (PIC) simulation model. The simulation results indicate that the distribution of ion density is ring-shaped. To verify the simulation result with the experimental result, the simulation result is compared with the optical emission distribution. In low propellant flow rates, the distribution of ion density agrees with the optical emission distribution. However, in high propellant flow rates, the optical emission distribution is different from simulation results in the waveguide due to the excited neutral particles. In the thruster, the performance strongly depends on the location of injecting the propellant. Hence, to develop the plasma simulation for quantitative comparison with the experiment, the distribution of the neutral density is evaluated by using direct Monte Carlo simulation (DSMC). The results show the neutral density in the waveguide increases corresponding to the ratio of waveguide injection, which indicates that the density is one of the most important parameters for quantitative evaluation with the experiment.</p>
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ACTA ASTRONAUTICA 166 69-77 2020年1月 査読有り
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TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 63(6) 281-283 2020年 査読有り
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宇宙太陽発電 5 101-106 2020年 査読有り<p> 電気推進を用いた軌道間輸送機の質量と輸送コストについて調査した. まず電気推進システムの理論式において, 質量とコストそれぞれを最小化する推進機比推力を検討し, 後者の方が低い比推力になることを示した. 次に, JAXAで開発中の技術試験衛星9号機をもとに, 静止軌道までの軌道間輸送機の質量とコストモデルを構築し, 感度解析を行った. 結果として, これまであまり議論されてこなかった, 電力系・推進系の比質量[kg/kW]の影響が大きいことがわかった. また, 現状達成可能な比質量範囲では多くの場合, 低軌道ではなく静止トランスファ軌道を出発軌道として静止化を行った方が, 質量・コストメリットが得られやすいことがわかった.</p>
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ACTA ASTRONAUTICA 165 25-31 2019年12月 査読有り
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REVIEW OF SCIENTIFIC INSTRUMENTS 90(10) 2019年10月 査読有り
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ACTA ASTRONAUTICA 161 382-388 2019年8月 査読有り
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Physics of Plasmas 26(7) 2019年7月1日 査読有り
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JOURNAL OF PROPULSION AND POWER 35(3) 565-571 2019年5月 査読有り
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Acta Astronautica 157 425-434 2019年4月 査読有り
MISC
110-
令和4年度宇宙輸送シンポジウム: 講演集録 = Proceedings of Space Transportation Symposium FY2022 2023年1月令和4年度宇宙輸送シンポジウム(2023年1月12日-13日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)) , 相模原市, 神奈川県 Space Transportation Symposium FY2022 (January 12-13, 2023. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan In the 3D-printed resistojet that the authors are working on, it is necessary to provide an electrical contact point at a high temperature part considering the limitations in 3D printing. So far, we have made some prototypes of flat contact type, tapered contact type, and screw type. In addition, as a new attempt, we also describe design guidelines for banana plug type that contact with radial surface pressure. 資料番号: SA6000184068 STEP-2022-016
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日本航空宇宙学会誌 = Aeronautical and space sciences Japan 70(10) 214-217 2022年10月
書籍等出版物
3-
Elsevier 2022年 (ISBN: 9780323997317)
担当経験のある科目(授業)
4-
2022年12月 - 2023年1月推進エネルギー変換工学 (東京大学大学院 新領域創成科学研究科)
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2021年9月 - 2022年2月エネルギー推進工学特論 (東京大学大学院 新領域創成科学研究科)
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2021年9月 - 2021年11月エネルギー推進工学特論 (東京大学)
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2013年9月 - 2016年3月地球と宇宙 (駒沢女子大学)
所属学協会
3-
2011年7月 - 現在
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2009年9月 - 現在
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2008年4月 - 現在
共同研究・競争的資金等の研究課題
8-
日本学術振興会 科学研究費助成事業 2023年4月 - 2027年3月
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日本学術振興会 科学研究費助成事業 2023年4月 - 2027年3月
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日本学術振興会 科学研究費助成事業 2023年4月 - 2027年3月
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日本学術振興会 科学研究費助成事業 若手研究(A) 2017年4月 - 2021年3月
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日本学術振興会 科学研究費助成事業 若手研究(B) 2014年4月 - 2017年3月
学術貢献活動
1メディア報道
1-
J-WAVE JK Radio Tokyo United https://www.j-wave.co.jp/original/tokyounited/archives/the-hidden-story/2021/02/19-111253.html 2021年2月 テレビ・ラジオ番組