掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

Abstract

In recent years, many plans have arisen for building constellations in low Earth orbit, some of which have already provided commercial services. The number of satellites that form these constellations will exceed $$10^4$$, and a number of these could become space debris due to accidental failure, leading to serious problems for human activities in space. Laser ablation-induced propulsion achieved by remote irradiation from the service spacecraft has been proposed as one effective method to remove such space debris and it involves effectively generating a propulsion impulse from a laser. Because most of the high-power lasers currently utilized in space applications are Nd:YAG lasers, in this study, we evaluate the characteristics of second harmonic generation (SHG), which can be generated using nonlinear crystals. The momentum coupling coefficient may be dependent on the irradiated laser wave length which has a significant difference in the ablation process such as plasma generation and heating. These effects have been investigated using an impulse measurement instrumental setup with a KD*P nonlinear crystal. As an efficient impulse generation method, the irradiation of the fundamental and SHG beams of the Nd:YAG laser at the same point was found to be more effective than the fundamental beam with the same total energy. SHG does not require additional power-consuming equipment such as additional exciters or amplifiers, but requite temperature-controlled nonlinear crystals, and impulses can be increased with minimal additional power. It turned out to be advantageous for space applications, which will require minimum power operation. Additionally, we found an additional nonlinear laser-induced impulses through the interaction of the beams.

DOI： 10.1007/s00339-022-05983-2

その他リンク： https://link.springer.com/article/10.1007/s00339-022-05983-2/fulltext.html

掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

DOI： 10.1007/s00193-022-01079-1

その他リンク： https://link.springer.com/article/10.1007/s00193-022-01079-1/fulltext.html

掲載種別：研究論文（学術雑誌）  

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

掲載種別：研究論文（学術雑誌）   出版者・発行元：American Institute of Aeronautics and Astronautics (AIAA)  

DOI： 10.2514/1.b38480

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Fluid Dynamics Research  

DOI： 10.1088/1873-7005/abeda4

Web of Science

Scopus

その他リンク： https://iopscience.iop.org/article/10.1088/1873-7005/abeda4/pdf

掲載種別：研究論文（学術雑誌）   出版者・発行元：Shock Waves  

DOI： 10.1007/s00193-021-01000-2

Web of Science

Scopus

その他リンク： https://link.springer.com/article/10.1007/s00193-021-01000-2/fulltext.html

掲載種別：研究論文（学術雑誌）   出版者・発行元：Experiments in Fluids  

DOI： 10.1007/s00348-020-03113-3

Web of Science

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review D  

DOI： 10.1103/PhysRevD.102.124063

Web of Science

Scopus

その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevD.102.124063/fulltext

掲載種別：研究論文（学術雑誌）   出版者・発行元：Plasma Sources Science and Technology  

DOI： 10.1088/1361-6595/ab8e4c

Web of Science

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Physics  

DOI： 10.1063/1.5144157

Web of Science

Scopus

掲載種別：研究論文（国際会議プロシーディングス）  

© 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

掲載種別：研究論文（国際会議プロシーディングス）  

© 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

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：{AIP} Publishing  

DOI： 10.1063/1.5023269

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.actaastro.2018.01.057

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2322/jjsass.66.128

出版者・発行元：David Publishing Company  

DOI： 10.17265/1934-8975/2017.06.001

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10762-016-0327-0

記述言語：英語  

記述言語：英語  

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Society for Aeronautical and Space Sciences  

DOI： 10.2322/tastj.14.pb_13

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本航空宇宙学会  

<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

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：American Institute of Aeronautics and Astronautics Inc, AIAA  

Beamed energy propulsion application has received keen research attention as a low cost launch system. In one of the ideas proposed over the years for such a system, millimeter-wave discharge plays a major role in converting beamed energy into kinetic energy through plasma-beam interaction and ejection of pressurized air. In previous discharge experiments, a characteristic formation of plasma front was observed during its propagation. Propagation of this front is referred as comb shaped plasma front propagation. This formation can affect energy-conversion efficiency. In this research, plasmoid formation was reproduced by computation, and pitch-size dependency on initial plasma-distribution, frequency and other parameters was investigated. From some numerical analysis, the causes of this formation are also discussed.

DOI： 10.2514/6.2016-4141

Scopus

記述言語：日本語   出版者・発行元：プラズマ応用科学会  

CiNii Books

記述言語：英語