Journal of Evolving Space Activities
Online ISSN : 2758-1802
Current issue
Displaying 1-27 of 27 articles from this issue
  • Yuki TAKEDA, Shinji TAKEDA, Shuhei KOIKE, Kenichiro SAWADA, Masahiro F ...
    2024 Volume 2 Article ID: 114
    Published: 2024
    Released on J-STAGE: April 17, 2024
    JOURNAL OPEN ACCESS

    Fifth-generation mobile communication system (5G) array-antenna transmitters attached to space deployable membrane structures were developed by the authors. The array-antenna mission’s main objectives are measuring the transmitters’ communication power and demonstrating the antenna’s non-flatness compensation function by beam-forming technology in Low Earth Orbit. Thermal design of the transmitters is critical for the mission’s success. Thus, this study demonstrates the process of designing Multi-Layer Insulation (MLI) to protect the 5G array-antenna transmitters from the harsh space environment. The design process includes thermal analysis, in-house fabrication of the MLI, and the thermal equilibrium test for correlation. The analysis reveals that the temperature of the radio-frequency integrated circuit in the transmitters can remain within the allowable temperature range by appropriately selecting the beaming period and satellite attitudes.

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  • Kaname KAWATSU, Tadashi MASUOKA, Kenta NAGAHAMA, Yuki TOMITA, Takashi ...
    2024 Volume 2 Article ID: 115
    Published: 2024
    Released on J-STAGE: April 17, 2024
    JOURNAL OPEN ACCESS

    Rendezvous docking is a key technique for space activities and missions, including in-orbit service and planetary exploration missions. One of the planned missions of the HTV-X, successor to the H-II Transfer Vehicle (HTV), is a demonstration of an automatic docking system. These docking systems need a high level of reliability and safety. However, it is difficult to comprehensively evaluate and verify the systems using only ground tests due to the inability to reproduce the actual operating conditions. Therefore, an efficient and reasonable model-based development method has been constructed to evaluate feasibility and safety in this study.

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  • Kikuko MIYATA, Takashi MATSUMOTO, Shinichi NAKASUKA
    2024 Volume 2 Article ID: 116
    Published: 2024
    Released on J-STAGE: April 17, 2024
    JOURNAL OPEN ACCESS

    In case of a disaster happening, one of the critical problems is the lack of robust communication systems capabilities for the people under the disaster. This paper proposes the portable or reconfigurable wide area network with specified low-power radio station equipment via multiple small flying objects constellations to achieve the data relay communication system. The unmanned small flying vehicles, such as drones or multicopters with specified low-power radio transmitters provide responsiveness. The small satellite with high sensitivity receiver and high-speed transmitter achieves wide-area communication, and robustness for on-ground disasters. The system concept and design policies are evaluated by rough numerical studies with realistic hardware constraints. The results show the feasibility of the proposed concept with the specific case study.

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  • Yusuke SHIMODA, Tetsuhito FUJITA, Manabu OKUI, Rie NISHIHAMA, Daisuke ...
    2024 Volume 2 Article ID: 117
    Published: 2024
    Released on J-STAGE: March 16, 2024
    JOURNAL OPEN ACCESS

    In this study, we proposed a training method and developed a training apparatus that can maintain antigravity muscles under microgravity conditions, aiming at the application to long-duration stays in space, including exploration of other planets. The training method was focused on the action of antigravity muscles. The device was designed to reproduce an unstable posture, and to make the subject use his/her muscles to stabilize the posture. In this paper, we propose an antigravity muscle training method, develop a prototype machine to realize the proposed method, and conduct posture maintenance experiments on the whole body using the prototype machine. The target movements were the maintenance of forward and backward leaning postures using the device, and the EMG potentials of each muscle were measured during the experimental movements. As a comparison, we measured the EMG potentials of each muscle during the experimental movement while the subject was standing and maintaining a posture tilted at a similar angle. The results showed that the trends of EMG changes in each muscle were similar between the experimental and comparison movements. The results showed that the prototype was able to provide the same load to the antigravity muscles as that of gravity.

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  • Tomoe YAYAMA, Fumiya ANDO, Fumiko AKAGI
    2024 Volume 2 Article ID: 118
    Published: 2024
    Released on J-STAGE: May 30, 2024
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    In this study, we developed an atomistic interface model for a composite of processed diglycidyl ether of bisphenol A (DGEBA) molecule and carbon nanotubes (CNTs) with point defects. We investigated the interfacial, mechanical, and electronic properties of the model. We found that strong covalent bonds are formed at the interface between CNT and DGEBA without decreasing the stiffness of the CNT. The Young's modulus of CNT with a point defect (without DGEBA) is 845.49 GPa, which is 5.46% lower than that of defect-free CNT (894.32 GPa). On the other hand, the Young's modulus of the CNT/DGEBA composites is 895.20 GPa, which is close to that of defect-free CNTs, indicating that Young's modulus is reduced by defects but recovered by the termination of the defects. These results suggest that the interfacial and mechanical properties of nanocomposites can be effectively improved by controlling the microscopic structures, such as defects.

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  • Yuki AKIYAMA, Takehiro MATSUMOTO, Hideaki HINAGAWA
    2024 Volume 2 Article ID: 119
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    In a previous study, we proposed a method for attitude motion estimation from SLR data using a genetic algorithm (GA). While it is a very effective method in that it requires no prior information, it has the disadvantage of inefficient local solution search. Therefore, we propose a new estimation method using another global optimization method, particle swarm optimization (PSO). In this paper, we performed numerical simulations with both the PSO and the GA for the same cases as in the previous study, and compared the obtained results. As a result, followings are revealed: (1) Good solutions were obtained by the PSO as well as the GA even if observations are polluted by noise and bias and the rotational speed is slow. (2) The PSO tends to find solutions closer to the true value than the GA if there is no bias in the observation times. (3) It is preferable to use the PSO in the problem setting assumed in the paper. We also describe a preprocessing to perform the analysis using actual SLR data.

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  • Nozomu KOGISO, Ryo KONAGAMITSU, Koichi YOKOTA, Yuki SUZUKI
    2024 Volume 2 Article ID: 120
    Published: 2024
    Released on J-STAGE: April 24, 2024
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    We have studied an antenna system using a smart reconfigurable sub-reflector for a high-resolution radio astronomy mission for a balloon-borne Very Long Baseline Interferometry (VLBI) mission. The antenna system consists of the camera image sensor system to capture the surface shape degradation of the primary reflector, the smart sub-reflector system to install the actuators and the displacement magnifying mechanisms to compensate for the optical path length error to recover the required antenna gain. The original strategy to achieve the stringent requirements was to adopt a high-precision image measurement method, which requires much more computation time. However, the strategy sacrifices the antenna operation time as the most important task. In order to deal with the contradictory situation, this study considers a resilient operation planning of the smart antenna system under multiple uncertainties. The system-theoretic process analysis (STPA) is adopted to re-model the smart antenna system from the resilient operation point of view. Then, the resilient operation model considering several uncertain factors as hazards is investigated.

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  • Shogo UZAWA, Hiroya KUMAMOTO, Chiaki YAMAZAKI, Manabu OKUI, Taro NAKAM ...
    2024 Volume 2 Article ID: 121
    Published: 2024
    Released on J-STAGE: March 16, 2024
    JOURNAL OPEN ACCESS

    Currently, human feces on the International Space Station is incinerated in the atmosphere. Because feces contain a large amount of organic matter in addition to water, the reuse of feces would require an increased amount of renewable resources. However, conventional space toilets are not designed for reusing feces. One of the reasons for this is that it is difficult to transport an intermittent supply like feces. Therefore, in this study, influenced by the peristaltic movement of the intestinal tract of living organisms, we developed a device that can transport feces at low energy consumption. The device consists of multiple pump units driven by low air pressure. By applying air pressure to each unit in turn, the pumps are controlled to close and release, which reproduces the peristaltic motion for transfer. Furthermore, the transfer rate is improved by combining the air inflow with the transfer channel and water addition.

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  • Ikkoh FUNAKI, Tadahiko SANO, Tsutomu FUKATSU, Yasuyoshi HISAMOTO, Daik ...
    Article type: Research Note
    2024 Volume 2 Article ID: 122
    Published: 2024
    Released on J-STAGE: April 24, 2024
    JOURNAL OPEN ACCESS

    Hall thruster is considered the key propulsion technology for a variety of spacecraft including Earth-orbiting satellites, space transportation systems, and space exploration. To acquire medium-power Hall thruster technology, a 6-kW-class Hall thruster system is under development at Japan Aerospace Exploration Agency (JAXA), which is the first Japanese Hall thruster to be tested onboard the Engineering Test Satellite-9 (ETS-9). Onboard ETS-9, a limited flight experiment of the Japanese Hall thruster subsystem will be conducted along with four main flight-proven foreign Hall thrusters as the bus system. Prototype model thrusters as well as an engineering model power processing unit are devoted to qualification tests. The qualification tests are in progress including an endurance test and system compatibility tests. In 2024, an end-to-end verification of the flight model thruster subsystem with the whole satellite system is planned for preparing the flight that is currently scheduled in FY2025.

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  • Makoto ITO, Yosuke TANABE, Hisatoshi KIMURA, Tsukasa FUNANE, Koichi WA ...
    2024 Volume 2 Article ID: 123
    Published: 2024
    Released on J-STAGE: April 24, 2024
    JOURNAL OPEN ACCESS

    Space Solar Power Systems (SSPSs) are renewable-energy systems that provide a continuous power supply. However, the efficiency of electric-power generation of SSPSs in the research phase needs to be improved. We investigated waste-heat recovery for a ground site of SSPSs to improve this efficiency. One type of SSPSs collects solar energy and converts it into electromagnetic wave in space then transmits it to a ground site on Earth. Most proposed ground sites for SSPSs are spread over several kilometers and receive 1–2 GW. The transmission frequency from space has been considered to be 2.45, 5.8, and 10 GHz, and the size of the ground site differs for each. The conversion efficiency of receiving power at the ground site is assumed to be approximately 70–90%. Therefore, the rest of the energy becomes waste heat. We investigated the wasteheat recovery for a ground site in terms of the frequencies and size of the transmitting antenna and ground site. The cooling system for the ground site is an air-cooling system, and the usable energy of waste heat as a heat source was estimated to be up to 48%.

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  • Ryosuke MOCHIDA, Kosei ISHIMURA, Sho IKUTA, Kohei MIYAMOTO, Nobuyuki O ...
    2024 Volume 2 Article ID: 124
    Published: 2024
    Released on J-STAGE: May 09, 2024
    JOURNAL OPEN ACCESS

    We proposed a pointing control technology for large support structures to meet demands for higher precision and larger size in the development of space observation equipment. A Stewart platform was adopted for the structure. As the linear actuator, we used a highly reliable artificial thermal expansion. To reduce heat transfer to structural members other than the actuator, we adopted an elastic hinge using an invar alloy called LEX-ZERO. The Stewart platform used in this study consists of six linear actuators and top/bottom plates which are connected by the elastic hinges. As a basic experiment, we conducted an experiment on the thermal insulation performance of elastic hinges. As a result of the experiment, about 97% of the heat flow from the artificial thermal expansion actuator could be cut off by elastic hinges. Then, 6 degrees of freedom control experiments were performed using the Stewart platform. As a result, it was possible to perform pointing control with excellent accuracy of within 1 μm in translational displacement and 2 arcseconds in rotational displacement.

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  • Takeshi MATSUMOTO, Tomotaka YAMAMOTO, Naoto USAMI, Kota KAKIHARA, Yosu ...
    2024 Volume 2 Article ID: 126
    Published: 2024
    Released on J-STAGE: May 09, 2024
    JOURNAL OPEN ACCESS

    The University of Tokyo and Arkedge Space Inc. are now developing 6U CubeSat named ONGLAISAT in collaboration with TASA (ex-NSPO), whose main mission is Earth remote sensing. This satellite uses S-band for telemetry and command communication by 10-100 kbps and 4 kbps for each link, and X-band for mission data transfer at high speed by 36 Mbps at maximum. Moreover, it has a Store & Forward (S&F) system for one of the missions. In this paper, we summarize the communication system of ONGLAISAT which consists of the S-band, X-band, and S&F components. In particular, we discuss the benefit of installing the S&F devices as a (compact) back-up TT&C system for a CubeSat.

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  • Maximilien BERTHET, Jorge Alberto GARCIA PEREZ, Kentaro ENOKIDA, Lucia ...
    Article type: Educational Program Report
    2024 Volume 2 Article ID: 127
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    Satellite projects bring together people from around the world. Cultural diversity can act as a catalyst for new technologies, yet multicultural teams are also vulnerable to cultural misunderstandings. These may negatively impact outcomes in a “Tower of Babel”-type scenario, especially in small and short-duration satellite projects. Members have limited time and resources to get to know each other before engaging in highly interdependent collaboration. The Culture Map, an analytical framework developed by Erin Meyer, is widely used to facilitate global teamwork in the corporate sphere. To the authors' knowledge, it has not yet been applied to small space-related projects. This paper presents one case study. The Culture Map is applied to a six-month university satellite design project, SEIMEI, comprising members from several countries. It is used in an interactive workshop among the team, after project completion. The workshop provides an accessible interface with relevant concepts in cross-cultural communication, for members of a small space project with a skillset concentrated in STEM. The objective of the analysis is to assess whether instances of smooth and non-smooth collaboration can be traced to cultural mechanisms, and whether outcomes can be enhanced via an understanding of such effects. The workshop focuses on building awareness of other cultures and individual perceptions, as a starting point for increasing the competence to deal with cultural differences. Lessons learnt are summarized, on the usefulness of The Culture Map for effective teamworking in small, culturally diverse space projects.

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  • Ikuko KURIYAMA, Toshio NISHIZAWA, Akira NISHIMOTO
    Article type: Research Note
    2024 Volume 2 Article ID: 128
    Published: 2024
    Released on J-STAGE: May 10, 2024
    JOURNAL OPEN ACCESS

    Since the adoption of the Sustainable Development Goals (SDGs) at the United Nations in 2015, JAXA has been contributing to the Goals through various activities. In March 2022, JAXA established the basic policy on SDGs in order to make its contribution in an even more organizational and strategic manner. This paper outlines JAXA’s major activities contributing to the SDGs and introduces the main contents of the basic policy on SDGs, including vision, mission statement, and prioritized areas for contribution. It also touches upon the background of the establishment of the basic policy and the way forward.

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  • Takahiro EBIHARA, Tetsushi IKEGAMI
    2024 Volume 2 Article ID: 129
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    We studied the effect of using Adaptive Coding and Modulation (ACM) on the data rate of a system that communicates between a high throughput satellite in geostationary orbit and the ground. We assumed two cases: OFDMA (Orthogonal Frequency Division Multiple Access) communication system and the environment under the resource control for frequency bandwidth and transmission power between beams. Rain attenuation was calculated from AMeDAS rainfall data to show the effect of ACM on actual rainfall changes. The modulation scheme and coding rate used those of DVB-S2 and DVB-S2X. The proposed method determines the allocation ratio of communication resources (transmission power and bandwidth) using the user's traffic demand information acquired from another channel and shows the effect of this method on the data rate when combined with ACM by comparing it with the case where communication resources are equally allocated to users.

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  • Johannes W OSWALD, Adam S. PAGAN, Alexander BEHNKE, Georg HERDRICH
    2024 Volume 2 Article ID: 130
    Published: 2024
    Released on J-STAGE: May 09, 2024
    JOURNAL OPEN ACCESS

    In the present study a dedicated plasma probe was designed to enhance the understanding of the physical separation of objects during re-entry and their radiative response. The plasma probe was exposed to an air plasma inside the plasma wind tunnel facility PWK4 of the Institute of Space Systems (IRS) of the University of Stuttgart. The chosen plasma condition corresponds to the thermochemical environment of a typical break-up altitude of a low earth orbit entry trajectory. The radiative response during the exposure of the plasma probe to the air plasma flow was observed via spatially and temporally resolved optical emissions spectroscopy. The spatially resolved emissions of the atomic oxygen triplet at 777.34 nm prove to be an excellent indicator for the study of shock layer thickness and location. Additionally, a significant increase in the spectral radiance of N2+ bands of the first negative system was observed at the merging point of two shock layers in between the opened plasma probe. Thus, it was concluded that a significant change in radiative markers related to a low-level break-up or break-off event could be the increased radiation of ionized molecular species of the surrounding air plasma.

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  • Clemens F. KAISER, Adam S. PAGAN, Hendrik BURGHAUS, Georg HERDRICH
    2024 Volume 2 Article ID: 131
    Published: 2024
    Released on J-STAGE: April 24, 2024
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    To investigate material behavior during Venusian aerobraking, a ground test facility is required that provides relatively low convective heat fluxes in combination with significant atomic oxygen fluxes. This study investigates the application of a PHLUX-type catalytic plasma probe to characterize such an environment in an inductively driven plasma wind tunnel. Using material specific properties regarding heterogeneous catalysis of oxygen recombination, the atomic oxygen flux in a highly dissociated plasma flow can be determined. For this study, copper and silicon carbide samples are utilized in the plasma probe. To determine the incident heat flux in the fringe of the plasma plume, the sample temperature is measured with both thermocouples and a thermal imaging camera. In the plasma wind tunnel PWK3 at the Institute of Space Systems (IRS) of the University of Stuttgart, atomic oxygen fluxes ranging from 1.0 × 1018 cm−2 s−1 to 1.5 × 1018 cm−2 s−1 are determined under convective heat fluxes up to 6.0kWm−2. A brief overview of the application of PHLUX sensors as flight instrumentation for atmospheric entry studies is given with an outlook to future in-situmeasurements during the early re-entry stage of the SOURCE CubeSat.

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  • Masahiro NONAKA, Takumi SAKAMOTO, Toramu MORITA, Arisa MORI, Naoki TAK ...
    2024 Volume 2 Article ID: 132
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    Rotating spoke, an example of azimuthal plasma instability, has been pointed out as one of the causes of anomalous electron transport in hall thruster plasmas. The high-speed camera images showed only ionization oscillations at an applied magnetic field of 15 mT, which is the dominant region for anomalous electron transport. Therefore, an axial-azimuthal 2D3V Full-PIC-DSMC analysis was performed. The analysis shows that during ionization, rotating spoke with mode number 32 occurs in the entire thruster circumference, while it does not occur during non-ionization. The axial transport of electrons under ionization oscillation was found to be dominated by mobility and Eθ×Br drift near the anode during ionization. In addition, the electron transport with Eθ×Br drift exist up to the axial wake.

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  • John E. SINKO, Jordan D. GRAUPMANN, Brian C. DAVIS, Travis J. MATHWIG
    2024 Volume 2 Article ID: 133
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    This experimental research study tested the effect of varying ambient air pressure on the normal incidence laser propulsive performance of various flat target element samples (Al, Bi, C, Cu, In, Mg, Mo, Ni, Si, Sn, grade 2 Ti, and V) as well as several metal alloys (mild steel, 316 stainless steel, grade 5 Ti, and 93% WHA). A spherical vacuum chamber was pumped to <0.1 Pa, then an Nd:YAG laser was operated at a fixed fluence at the focus position to vaporize fresh areas of the target with single shots of laser energy. The ambient pressure was incremented between shots by partial venting of the chamber with ambient air from ~10-2 to ~105 Pa. Momentum coupling and thermal absorptance were evaluated as a function of pressure for each material at a calculated beam fluence at ~104 J/cm2. The results were interpreted with the assistance of open shutter DSLR photography of the ablation events at each pressure. The data are generally consistent with literature predictions and should be helpful for design of a wide range of future laser propulsion missions involving metal ablatants.

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  • Tomoshige KAN, Byeongpyo JEONG, Takashi TAKAHASHI, Hiroyuki TSUJI
    2024 Volume 2 Article ID: 135
    Published: 2024
    Released on J-STAGE: May 10, 2024
    JOURNAL OPEN ACCESS

    NICT of Japan has been conducting communications research using a high-speed Ka-band internet satellite. The project includes the development and operation of a mobile earth station mounted on a van, hereafter called the vehicle earth station. The vehicle earth station is equipped with an antenna system that can automatically detect and track the satellite at a longitude of 110 degrees east. Understanding the propagation environment is key for the construction of a communications system because shadowing between satellites and earth stations affects mobile satellite communications. In this study, we conducted propagation measurements to compare the effects of shadowing due to differences in urban structures (i.e., urban, suburban, and rural areas). Furthermore, a simulation based on GIS was conducted to evaluate shadows on buildings. The results of propagation measurements and GIS simulations were compared to evaluate the effects of shadowing due to buildings and other factors (vegetation, etc.).

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  • Yoshinori NAKAYAMA, Tsubasa ITO, Junki WAKAI
    2024 Volume 2 Article ID: 136
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    To evaluate the phenomena occurring in cylindrical Hall thrusters and to improve their performance, a visualized CHT with a glass discharge chamber and eight bar-shaped magnets were designed and fabricated. Through experimental evaluation, it was confirmed that the plasma produced in the discharge chamber and the plume downstream of the thruster are visible in proximity and that the estimated thruster performance is almost the same as that of the conventional CHTs, despite the visualization (thrust of 2.3 mN, specific impulse of 820 s). Further improvement of the CHT will be useful as a method for evaluating the Test Facility Effect and as a device for promoting understanding of electric propulsion systems.

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  • Ippei Takahashi, Kyohei Akiyama, Takafumi Katsuyama, Kazunori Someya, ...
    2024 Volume 2 Article ID: 140
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    This paper presents an autonomous navigation system that uses optical inter-satellite communication technology. Autonomous navigation systems improve robustness by predicting global navigation satellite system (GNSS) orbits and clock offsets on board and providing navigation messages to enable a satellite positioning service to continue operating even when ground stations are unavailable. This paper reports the results of our feasibility study on a suitable target value of signal-in-space user-range-error (SIS-URE), an index that indicates errors in satellite positioning systems caused by unforeseen circumstances.

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  • Tatsushi ISONO, Masatoshi KODERA, Taro KAWANO, Osamu HARADA, Shinji TO ...
    2024 Volume 2 Article ID: 141
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    The S-520 Japanese sounding rocket has recently begun to be utilized as a Flying Test Bed (FTB) for investigating Flight Test Models (FTMs). The FTM contains fuel and avionics and thus requires a Ground Air-Conditioning System (GACS). The GACS has two roles. One is to maintain the inert gas atmosphere inside the FTM, which prevents combustion in case of fuel leak. The other is to keep the inside of the FTM at a temperature suitable for its avionics by supplying cold gas. The GACS was developed for the S-520-RD1 sounding rocket, which is used in supersonic combustion flight testing. The GACS consists of five sections: a gas source, heat exchanger, flow path switching system, rotation arm, and vacuum connector. The GACS was successfully operated throughout S-520-RD1 launch schedule. FTM Internal atmosphere kept perfectly inert and met avionics cooling requirement. The vacuum connector was correctly separated from the FTM by remote vacuum breaking and the motion of the rotation arm during the vacuum connector separation phase just before launch. In short, the operation was completed successfully.

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  • Shujun GUO, Masayoshi NAGAO, Katsuhisa MURAKAMI, Hiromasa MURATA, Yosh ...
    Article type: Research Note
    2024 Volume 2 Article ID: 142
    Published: 2024
    Released on J-STAGE: June 03, 2024
    JOURNAL OPEN ACCESS

    In this study, we have fabricated ionic liquid electrospray thrusters to prevent ionic liquid leakage and provide high current density. A double-emitter structure with a needle protruding from the capillary emitter, where the ionic liquid was intended to be held by the needle, was proposed. The fabrication process employs a fabrication technique of a field emitter array, and a newly designed process to reduce the distance between emitters was used to improve emitter density. As a result of the fabrication, the needle was successfully formed in the emitter electrode, and it was found that emitter density could be improved by changing the deposition conditions of multiple SiO2 layers.

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  • Takahisa KANEDA, Masato FUNATSU, Kosuke UOYA, Soshi SHIRAISHI
    2024 Volume 2 Article ID: 144
    Published: 2024
    Released on J-STAGE: May 30, 2024
    JOURNAL OPEN ACCESS

    When a sample return capsule re-enters the Earth's atmosphere, a strong shock wave is generated in front of the capsule and it receives severe aerodynamic heating. An ablation method is one of the thermal protection methods to protect the capsule from this heating. In the future, capsules are expected to become larger and re-entry speeds are expected to increase. Therefore, the capsule will be exposed to more significant aerodynamic heating. In this experiment, lightweight porouscarbon materials with controllable density and porosity and resin-impregnated porous-carbon materials were fabricated, and heating experiments using air plasma freejets were conducted. Spectroscopic measurements were made at the tip of test piece and around the tip of that emitted light during the experiments. The change in the apparent temperature value of the test-piece surface due to pyrolysis gas generation and the chemical species of the pyrolysis gases generated were investigated. Based on the spectroscopic results, the apparent temperatures of the test-piece surface of porous-carbon materials and resinimpregnated porous-carbon materials were estimated to be about 2,500 K and 1,600 K, respectively. The chemical species of the pyrolysis gases generated by heating were C2 Swan band systems.

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  • Momoko NAEMURA, Yoshinori TAKAO
    Article type: Research Note
    2024 Volume 2 Article ID: 146
    Published: 2024
    Released on J-STAGE: June 03, 2024
    JOURNAL OPEN ACCESS

    Time-of-flight (ToF) mass spectroscopy for electrospray thrusters was constructed to investigate the species and fraction of ions in the beam and the presence of fragmentation, where a cylindrical shield was placed just in front of the collector. The shield was expected to prevent the detection of secondary species, which were recently found to be one of the vacuum facility effects. However, the shield seemed to have almost no effects on the ToF signals because the signal did not decrease to zero, and some particles were always detected as they had been detected without the shield. To examine the cause of this signal detection, the collector current was measured under the condition that the gate electrode completely blocked the ion beam. The results implied that the electrospray ion source also emitted some neutrals. The measurement system was reconstructed to detect ions using a high-speed amplifier to avoid neutral particle detection. Then, the results showed that the electrospray thruster was operating in the pure ion mode.

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  • Koki MATSUKAWA, Yoshinori TAKAO
    Article type: Research Note
    2024 Volume 2 Article ID: 149
    Published: 2024
    Released on J-STAGE: June 03, 2024
    JOURNAL OPEN ACCESS

    We have fabricated an externally wetted emitter array with a deep-grooved structure using grayscale lithography for ionic liquid electrospray thrusters to improve the ionic liquid transport to the emitter tips and to reduce the percentage of the current intercepted by the extractor electrode, which was more than 30% with our conventional deep-grooved emitter. The experimental results of the ion emission have shown that a stable ion emission characteristic and the percentage of the current intercepted by the extractor electrode decreases by approximately one-third compared with our previous one. This decrease indicates that the emitter fabrication process using grayscale lithography optimized the deep-grooved emitter shape.

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