Updated on 2023/09/11

写真a

 
NAKAMURA Yusuke
 
Organization
Graduate School of Engineering Aerospace Engineering 1 Designated assistant professor
Title
Designated assistant professor
External link

Degree 1

  1. 博士(科学) ( 2019.3   東京大学 ) 

Education 1

  1. The University of Tokyo   Graduate School of Frontier Sciences

    2014.4 - 2019.3

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    Country: Japan

Awards 4

  1. The 26th Annual Meeting of IAPS Best Poster Award

    2019.3   Role of Photon-Carrying Excited-Neutral-Particles on Ionization Front Propagating in Millimeter-Wave with Under-Critical Intensity

    Yusuke NAKAMURA, Kimiya KOMURASAKI, Kuniyoshi TABATA, Hiroyuki KOIZUMI

  2. 新領域創成科学研究科長賞(博士)

    2019.3   東京大学  

  3. Plasma Conference 2017 若手優秀発表賞

    2017.11   プラズマ核融合学会   亜臨界強度のミリ波電界中での放電進展シミュレーション

    中村友祐, 小紫公也, 小泉宏之

  4. 日本航空宇宙学会47期年会講演会 優秀発表賞受賞

    2016.4   日本航空宇宙学会   ミリ波放電伸展時における粒状プラズマの数値解析

    中村友祐, 福成雅史, 山口敏和, 小紫公也, 小泉宏之

 

Papers 25

  1. Measurement of ablation impulse and direction with oblique laser-pulse irradiation

    Yusuke Nakamura, Daichi Moriyama, Atsushi Isomura, Akihiro Sasoh

    Acta Astronautica     2023.6

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.actaastro.2023.03.017

  2. Transition to Weak-Shock Solution Around Centerbody Using Laser Energy Deposition Reviewed

    Hiroki Asai, Yusuke Nakamura, Akihiro Sasoh

    AIAA Journal     2022.11

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.2514/1.J061785

  3. Petal formation law in a cellophane diaphragm subjected to a pressure difference Reviewed

    Gaku Fukushima, Jun Hagiwara, Yusuke Nakamura, Akihiro Sasoh

    Physical Review E   Vol. 106 ( 4 )   2022.10

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    Publishing type:Research paper (scientific journal)  

    In this study, a layer of cellophane, subjected to an air-pressure difference, was ruptured using a piercing needle. Accordingly, petal-like fragmentation was observed in the layer via high-speed imaging. Two types of crack-propagation regimes were subsequently observed experimentally. If a tensile stress lower than 20.6 MPa acted on the cellophane diaphragm, a single crack was generated, whose propagation speed was lower than that under higher-stress conditions. For tensile stresses greater than 23.7 MPa, the crack-propagation speed remained constant at approximately 0.86 km/s, even after altering the device size, pressure, and humidity on the low-pressure side. The number of cracks equidistant from the piercing point was expressed as a linear function of the tensile stress acting on the diaphragm.

    DOI: 10.1103/PhysRevE.106.L043001

    Scopus

    PubMed

  4. Geometrical matching in remote in-tube shock compression by an unsteady jet Reviewed

    D. Ichihara, D. Kuwabara, D. Moriyama, Y. Nakamura, A. Iwakawa, A. Sasoh

    Shock Waves   Vol. 32 ( 4 ) page: 373 - 381   2022.6

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1007/s00193-022-01079-1

    Other Link: https://link.springer.com/article/10.1007/s00193-022-01079-1/fulltext.html

  5. Electrostatic–magnetic hybrid ion acceleration for high-thrust-density operation Reviewed

    D. Ichihara, R. Nakano, Y. Nakamura, K. Kinefuchi, A. Sasoh

    Journal of Applied Physics   Vol. 130 ( 22 )   2021.12

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    Publishing type:Research paper (scientific journal)  

    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

    Scopus

  6. Thrust Density Enhancement in an Electrostatic–Magnetic Hybrid Thruster Reviewed

    Daisuke Ichihara, Koichiro Oka, Ayumi Higo, Yusuke Nakamura, Kiyoshi Kinefuchi, Akihiro Sasoh

    Journal of Propulsion and Power   Vol. 37 ( 6 ) page: 973 - 976   2021.11

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    Publishing type:Research paper (scientific journal)   Publisher:American Institute of Aeronautics and Astronautics (AIAA)  

    DOI: 10.2514/1.b38480

    Scopus

  7. Losing the shock wave front profile due to interaction with turbulence Reviewed

    Gaku Fukushima, Jiaxi Wei, Shingo Ogawa, Jun Hagiwara, Yusuke Nakamura, Akihiro Sasoh

    Fluid Dynamics Research   Vol. 53 ( 2 ) page: 025504 - 025504   2021.4

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    Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    In this study, losing the shock wave profiles under interactions with grid turbulence was investigated experimentally and theoretically. We demonstrated that the shock wave contrast on side-view schlieren images gradually decreased to an undetectable level in the experiment. This shock wave 'vanishment' occurred at a low shock Mach number with a high turbulent Mach number. With a relatively strong shock wave, the contrast of the shock wave remained detectable although the shock wave profile region was expanded. To understand the shock wave vanishment phenomenon during interaction with turbulence, we established a shock wave vanishment model based on the solution of a one-dimensional interaction between a shock wave and forward induced flow. The criterion of the occurrence of local vanishment of the shock wave was derived as, where Mt is the turbulent Mach number and Ms is the shock Mach number. The proposed shock vanishment model involves the effect of the interaction length and the shock wave recovery characteristics. The derived model explains the vanishment of weak shock wave profile during turbulence with an interaction length of ten times the order of the integral scale of the turbulence, as observed in the experiment.

    DOI: 10.1088/1873-7005/abeda4

    Web of Science

    Scopus

    Other Link: https://iopscience.iop.org/article/10.1088/1873-7005/abeda4/pdf

  8. Impacts of grid turbulence on the side projection of planar shock waves Reviewed

    G. Fukushima, S. Ogawa, J. Wei, Y. Nakamura, A. Sasoh

    Shock Waves   Vol. 31 ( 2 ) page: 101 - 115   2021.3

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    In this study, the characteristics of side-projected planar shock waves propagating through grid turbulence were investigated using a counter-driver shock tube. At the location of visualization of the shock–turbulence interactions, the range of the shock Mach numbers was Ms= 1.01 - 1.15 and the representative values of the turbulent Mach numbers Mt~ were 0.005 - 0.014. The interaction length between the shock wave and grid turbulence was in the range approximately from - 50 to 300 times the integral length scale of the turbulence. For the interaction involving the strongest turbulence with Mt~ = 0.014 , the weakest planar shock wave with Ms= 1.01 was largely deformed and could not be detected on the projected shadowgraph and schlieren images. The density changes on the grayscale in the projected images of the shock waves weakened and expanded multidimensionally. This undetectable profile of the shock wave could indicate that the shock wave locally lost discontinuous property change profile. The shock waves with Ms≥ 1.05 did not show the undetectable profile in the projected image. In these cases, the projected thickness of the shock wave increased with an increase in the interaction length. The increase in the projected thickness became larger as the turbulent Mach number increased, and the shock Mach number decreased.

    DOI: 10.1007/s00193-021-01000-2

    Web of Science

    Scopus

    Other Link: https://link.springer.com/article/10.1007/s00193-021-01000-2/fulltext.html

  9. Speckle beam-oriented schlieren technique Reviewed

    Yusuke Nakamura, Takumi Suzuki, Kiyoshi Kinefuchi, Akihiro Sasoh

    Experiments in Fluids   Vol. 62 ( 1 )   2021.1

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media {LLC}  

    Abstract: An advanced background-oriented schlieren (BOS) method, named as the speckle beam-oriented schlieren technique, was newly developed to measure the distribution of refraction angles in transparent media. A speckle pattern is generated by passing a coherent laser beam through a holographic diffuser, a pinhole, and a lens, generating a collimated background image that is projected directly onto the image sensors. Since the intensity of the background image is maintained at a high level, this method is, in principle, useful for diagnosing fast and/or low signal-to-noise phenomena, such as high-temperature gasses with radiation emission. Moreover, by splitting the background beam into two imaging paths with different focal lengths, the refraction angles can be measured for a schlieren object with uncertain location, and the depth position of the refraction angles can be resolved. This technique was demonstrated by measuring the refraction angle and the depth position distribution in a sonic jet with different injected locations. Graphic abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-020-03113-3

    Web of Science

    Scopus

  10. General relativistic effects on Hill stability of multibody systems: Stability of three-body systems containing a massive black hole Reviewed

    Haruka Suzuki, Yusuke Nakamura, Shoichi Yamada

    Physical Review D   Vol. 102 ( 12 )   2020.12

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/PhysRevD.102.124063

    Web of Science

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevD.102.124063/fulltext

  11. Theory and modeling of under-critical millimeter-wave discharge in atmospheric air induced by high-energy excited-neutral-particles carried via photons Reviewed

    Yusuke Nakamura, Kimiya Komurasaki

    Plasma Sources Science and Technology   Vol. 29 ( 10 )   2020.10

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1088/1361-6595/ab8e4c

    Web of Science

    Scopus

  12. Experimental investigation of ionization front propagating in a 28 GHz gyrotron beam: Observation of plasma structure and spectroscopic measurement of gas temperature Reviewed

    Kuniyoshi Tabata, Yuki Harada, Yusuke Nakamura, Kimiya Komurasaki, Hiroyuki Koizumi, Tsuyoshi Kariya, Ryutaro Minami

    Journal of Applied Physics   Vol. 127 ( 6 )   2020.2

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/1.5144157

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    Scopus

  13. Millimeter-Wave Discharge below Critical Intensity Using a 28 GHz Gyrotron Reviewed

    Kuniyoshi Tabata, Yusuke Nakamura, Kimiya Komurasaki, Tsuyoshi Kariya, Ryutaro Minami

    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz   Vol. 2018-September   2018.10

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    Publishing type:Research paper (international conference proceedings)  

    © 2018 IEEE. Microwave Rocket is one of beamed energy propulsion systems, whose energy is wirelessly supplied by using a millimeter-wave beam. Although millimeter-wave discharge plasma in under-critical conditions is necessary for its thrust generation, it has not been clarified why discharge is sustained below the critical intensity. One of the possible mechanisms is the one in which the plasma is composed of many excited molecules which can be ionized by lower-energy electrons than those in a ground state. Therefore, experiments using a 28 GHz gyrotron was conducted to confirm the physical modeling. Assuming that electron excitation temperature is higher than vibrational temperature, vibrational temperature was examined. As a result, the measured vibrational temperature of nitrogen molecules increased as peak intensity of millimeter-wave beam becomes lower. The result implies that electron excitation temperature is higher in those regions and highly excited molecules are important for ionization below critical intensity.

    DOI: 10.1109/IRMMW-THz.2018.8510094

    Scopus

  14. Modeling of Under-Critical Millimeter-Wave DiScharge Induced by High Excitation Temperature Reviewed

    Yusuke Nakamura, Kimiya Komurasaki, Hiroyuki Koizumi

    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz   Vol. 2018-September   2018.10

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    Publishing type:Research paper (international conference proceedings)  

    © 2018 IEEE. Resent results of millimeter wave discharge experiments suggest that the high excitation temperature plays an important role in the ionization frond propagation in under-critical intensity. In this research, a simple model was proposed considering this high excitation temperature, and the theoretical propagation velocity was calculated using this model. The results were compared with the experimental results using 170 GHz and 28 GHz millimeter-wave. The theoretical results gave good agreement with the experimental results in 170 GHz. However, it disagreed with the results in 28 GHz when the peak power density is larger than 0.2 GW/m2, because the ionization front doesn't keep its shape during propagation.

    DOI: 10.1109/IRMMW-THz.2018.8510141

    Scopus

  15. Numerical analysis of plasma structure observed in atmospheric millimeter-wave discharge at under-critical intensity Reviewed

    Yusuke Nakamura, Kimiya Komurasaki, Masafumi Fukunari, Hiroyuki Koizumi

    Journal of Applied Physics   Vol. 124 ( 3 ) page: 033303 - 033303   2018.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:{AIP} Publishing  

    DOI: 10.1063/1.5023269

  16. Thrust generation experiments on microwave rocket with a beam concentrator for long distance wireless power feeding Reviewed

    Masafumi Fukunari, ToshikazuYamaguchi, Yusuke Nakamura, Kimiya Komurasaki, Yasuhisa Oda, Ken Kajiwara, Koji Takahashi, Keishi Sakamotod

    Acta Astronautica     2018.4

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.actaastro.2018.01.057

  17. Numerical Calculation on Air-Inlet Design of Microwave Rocket Reviewed

    Kuniyoshi Tabata, Florian Nguyen, Yuki Harada, Masafumi Fukunari, Kaoru Kakinuma, Kimiya Komurasaki, Yusuke Nakamura, Hiroyuki Koizumi

    JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   Vol. 66 ( 5 ) page: 128 - 134   2018

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japan Society for Aeronautical and Space Sciences  

    DOI: 10.2322/jjsass.66.128

  18. Rocket Propulsion Powered Using a Gyrotron Reviewed

    Masafumi Fukunari, Kimiya Komurasaki, Yusuke Nakamura, Yasuhisa Oda, Keishi Sakamoto

    Journal of Energy and Power Engineering   Vol. 11 ( 6 )   2017.6

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    Publisher:David Publishing Company  

    DOI: 10.17265/1934-8975/2017.06.001

  19. Design of a Millimeter-Wave Concentrator for Beam Reception in High-Power Wireless Power Transfer Reviewed

    Masafumi Fukunari, Nat Wongsuryrat, Toshikazu Yamaguchi, Yusuke Nakamura, Kimiya Komurasaki, Hiroyuki Koizumi

    Journal of Infrared, Millimeter, and Terahertz Waves     2017.2

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1007/s10762-016-0327-0

  20. Structural Change of Plasma at Various Ambient Pressures in 28 GHz Millimeter-Wave Discharges Reviewed

    Yuki HARADA, Yusuke NAKAMURA, Kimiya KOMURASAKI, Ryutaro MINAMI, Tsuyoshi KARIYA, Tsuyoshi IMAI, Kohei SHIMAMURA, Masafumi FUKUNARI

    Frontier of Applied Plasma Technology   Vol. 10 ( 1 ) page: 7 - 10   2017.1

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  21. Fast-Framing Observation of Filamentary Plasma in Atmospheric Millimeter-Wave Breakdown Reviewed

    Toshikazu YAMAGUCHI, Masafumi FUKUNARI, Yusuke NAKAMURA, Yasuhisa ODA, Keishi SAKAMOTO, Kimiya KOMURASAKI

    Frontier of Applied Plasma Technology   Vol. 25 ( 1 ) page: 7 - 8   2016.3

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    Language:English  

  22. Initial Flight Operations of the Miniature Propulsion System Installed on Small Space Probe: PROCYON Reviewed

    Hiroyuki KOIZUMI, Hiroki KAWAHARA, Kazuya YAGINUMA, Jun ASAKAWA, Yuichi NAKAGAWA, Yusuke NAKAMURA, Shunichi KOJIMA, Toshihiro MATSUGUMA, Ryu FUNASE, Junichi NAKATSUKA, Kimiya KOMURASAKI

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN   Vol. 14 ( ists30 ) page: Pb_13 - Pb_22   2016

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Japan Society for Aeronautical and Space Sciences  

    DOI: 10.2322/tastj.14.pb_13

  23. Two-Stage-to-Orbit Transporting System Combining Microwave Rocket and Microwave Thermal Rocket for Small Satellite Launch Reviewed

    Kaoru KAKINUMA, Masafumi FUKUNARI, Toshikazu YAMAGUCHI, Yusuke NAKAMURA, Hiroyuki KOIZUMI, Kimiya KOMURASAKI, Kevin PARKIN

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN   Vol. 14 ( 30 ) page: Pb_99 - Pb_103   2016

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    <p>This paper proposes a two-stage-to-orbit launch system comprised of a Microwave Rocket 1st stage and a Microwave Thermal Rocket 2nd stage. The air-breathing 1st stage improves payload fraction relative to a single-stage-to-orbit system and carries the 2nd stage above the atmosphere and into range of its beam director. For the 1st stage task, a Microwave Rocket is superior to an unmanned aerial vehicle because it is simpler, faster, and reaches higher altitude at higher speed. In addition, we present a new trajectory that eliminates power beaming at low elevation angles and improves system performance. This combination of factors reduces the propellant needed in the 2nd stage, which in turn increases payload fraction by a remarkable factor of 3 times.<i><b> </b></i></p>

    DOI: 10.2322/tastj.14.pb_99

  24. Millimeter-wave Discharge Experiment in Atmosphere Using a 28 GHz Gyrotron Reviewed

    Journal of IAPS   Vol. 53 ( 1 ) page: 42 - 45   2015.6

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    Language:Japanese  

    CiNii Books

  25. Filamentary Structure of Millimeter-Wave Discharge Plasma at Low Beam Power Density Reviewed

    Yusuke NAKAMURA, Toshikazu YAMAGUCHI, Kimiya KOMURASAKI, Tony SHOENHERR, Hiroyuki KOIZUMI

    Frontier of Applied Plasma Technology   Vol. 8 ( 1 ) page: 7 - 12   2015

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    Language:English  

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MISC 4

  1. Electrostatic Ramjet Thruster for Air-Drag Compensation of Small Satellite at Super Low-Earth-Orbit

    中村友祐, 杵淵紀世志, 佐宗章弘

    宇宙科学技術連合講演会講演集(CD-ROM)   Vol. 65th   2021

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  2. Density Gradient Visualization Method Using “Speckle Beam“: Speckle Beam Oriented Schlieren (SBOS)

    中村友祐, 鈴木拓実, 杵淵紀世志, 佐宗章弘

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)   Vol. 53rd-39th   2021

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  3. Impacts of Shock and Turbulent Mach Number and Interaction Length on Planar Shock-grid Turbulence Interactions

    福嶋岳, 小川真吾, WEI Jiaxi, 中村友祐, 杵淵紀世志, 佐宗章弘

    衝撃波シンポジウム講演論文集(CD-ROM)   Vol. 2019   2020

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  4. Numerical Analysis of Plasmoid Formation in Millimeter-wave Discharge

      Vol. 47   page: 4p   2016.4

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    Language:Japanese  

    CiNii Books

KAKENHI (Grants-in-Aid for Scientific Research) 5

  1. 三次元磁場配位を持ったECR放電室と磁気ノズルによる超低軌道環境模擬風洞の開発

    Grant number:23K13494  2023.4 - 2026.3

    日本学術振興会  科学研究費助成事業  若手研究

    中村 友祐

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    Authorship:Principal investigator 

    Grant amount:\4680000 ( Direct Cost: \3600000 、 Indirect Cost:\1080000 )

    近年増加している低軌道小型衛星の処分時における軌道や,大気吸い込み式電気推進機の作動条件を探る上で,高度数百kmの超低軌道において衛星が受ける環境を知ることが重要である.しかしながら現状この環境を地上で長時間模擬する風洞は存在しない.そこで,本研究では新たに提案する風洞を設計、製作し、超低軌道環境模擬を試みる.提案する風洞では高周波を用いて発生させたプラズマを、向きが異なる磁石を組み合わせて作成した三次元磁場配位を持つ放電室中に生成し,これを磁気ノズルで加速し,テストセクションへと導く.また、完成した風洞の性能評価を行う。

  2. Shock Wave Moderation by Fore-Flow Nudge: Proof of Principle and Applications

    Grant number:21H04589  2021.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (A)

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    Authorship:Coinvestigator(s) 

  3. Small electrodeless electric propulsion system with ECR plasma and fluctuating magnetic field

    Grant number:20K14949  2020.4 - 2022.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Early-Career Scientists

    Nakamura Yusuke

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    Authorship:Principal investigator 

    Grant amount:\4290000 ( Direct Cost: \3300000 、 Indirect Cost:\990000 )

    In this research, I aim to demonstrate a newly proposed electrodeless electric propulsion system for space craft. In this propulsion system, plasma generated with electron cyclotron resonance (ECR), which is the interaction between electrons in magnetic field with specific strength and high-frequency (GHz band) electro-magnetic wave, is accelerated by controlling the magnetic field by a coil. A system capable of radiating a high frequency with a maximum output of about 15 W in the frequency range of 2 GHz to 4 GHz was completed. ECR discharge plasma was successfully created in a tube with a diameter of 10 mm within the target energy range using only permanent magnets. However, the stable generation of plasma in the magnetic field by a coil and a magnet was not successful. Therefore, farther researches are needed to demonstrate this propulsion.

  4. Demonstration of an innovative small airbreathing electric-propulsion-system using the kinetic energy of the supersonic atmosphere

    Grant number:19K23486  2019.8 - 2021.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Research Activity Start-up

    Nakamura Yusuke

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    Authorship:Principal investigator 

    Grant amount:\2860000 ( Direct Cost: \2200000 、 Indirect Cost:\660000 )

    Recent years, the increase in space debris has become a big problem. Objects on the ultra-low earth orbit at an altitude of about 200 km do not become space debris due to the resistance of the rarefied atmosphere. Despite a thruster is required to maintain this orbit, if electric-propulsion system using the breathed atmosphere as a propellant can be realized, it is possible to maintain this orbit as long as the satellite does not breakdown. In this study, we proposed a new air-breathing electric propulsion system with new features. This thruster was manufactured, and tested with a rarefied airflow. However, the airflow used here has not sufficiently simulate the environment of the ultra-low earth orbit, and further research is required to realize it.

  5. ミリ波放電を用いたマイクロ波ロケットにおける推力生成過程の解明及び性能向上

    Grant number:17J09280  2017.4 - 2019.3

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    中村 友祐

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    前年度行った数値計算を用いた構造模擬の結果、用いたモデルにおいて実験で観測された構造と進展速度を達成するには、換算電界強度に三倍以上の非物理的な補正をかけなければならないことが分かった。このことは、電離を誘起する、従来モデルでは考えられていないメカニズムが存在する可能性を示唆している。さらに前年度の分光実験においては、電離波面における励起温度が7000 K程度と比較的高い温度になっていることが観測され、このような高い励起温度領域が進展に影響を及ぼす可能性が示唆された。本年度は、これら前年度の研究の結果を踏まえて励起中性粒子が電離波面における電離を誘起する可能性に注目し、進展メカニズムの解明を目指した。高エネルギー励起中性粒子は基底状態の中性粒子に比べて低いエネルギーの電子との衝突でも電離することが出来、この励起中性粒子が十分存在すれば電離を誘起することが可能である。しかし、このような励起中性粒子は電子数密度の高いバルク領域において主に生成されるため、電離波面の進展に寄与するにはこれを駆動しているプリカーサ領域まで励起中性粒子を輸送する過程が存在しなければならない。そこで、本研究において光脱励起で生じる光子がバルクからプリカーサに励起中性粒子を輸送することで電離波面を駆動する新しい進展メカニズムを提唱した。この光子による輸送を、拡散近似を用いて定式化し、さらに中性粒子の励起状態についても簡素な仮定を導入して定式化することで、このメカニズムによる電子波面の進展を数値的に模擬した。また、各パラメータに対する進展速度の依存性も調査した。この結果、クエンチングの周波数が10^6 /s程度以下であれば、計算で得られる進展速度が入射ミリ波強度によらず実験値の50%程度となり、先行研究に比べて非常に良い一致をみせた。