Browsing by Author "Kajiyama, Satoshi"

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Ammonia Loop Heat Pipe with Thin Evaporator Fabricated by Additive Manufacturing
(2023 International Conference on Environmental Systems, 2023-07-16) Nagano, Hosei; Kajiyama, Satoshi; Nakazawa, Kazuhiro; Tsuru, Takeshi; Akizuki, Yuki
The next-generation X-ray observation satellite "FORCE" is being developed for launch in the early 2030s. To achieve low-noise and high-sensitivity X-ray observations with the CMOS detector on this satellite, the operating temperature must be kept low. FOr the thermal design, following conditions are required: (1) a heat source temperature is -25°C or lower, (2) a maximum heat transport capability is 10 W, (3) a temperature difference between the heat source to the heat sink is 5°C or lower, and (4) the thickness of the LHP is 3mm or less. In this study, we proposed an ammonia loop heat pipe with flat evaporator that can operate in low-temperature environments which is fabricated in 3D printer. In the full paper, design, fabrication, and test results at room temperature and low temperature will be presented.
On-orbit demonstration of Advanced Thermal Control Devices using JAXA Rapid Innovative payload demonstration SatellitE-2 (RAISE-2)
(50th International Conference on Environmental Systems, 2021-07-12) Nagai, Hiroki; Tanaka, Hiroto; Kajiyama, Satoshi; Mizutani, Takuji; Nagano, Hosei; Sawada, Kenichiro; Matsumoto, Kan
In recent years, advances in thermal control technology have become essential for deep space exploration to achieve exploration goals. For missions that explore an outer planet, the limited power resources available from solar panels must be used to maintain the temperature of the spacecraft. Therefore, there is an urgent need to develop lightweight thermal control technology that does not use power resources. ?We have conducted research and development of original thermal control devices such as flexible deployable radiators, thermal straps, self-excited oscillating heat pipes, and heat storage devices, and their effectiveness has been confirmed in ground tests, but there has been no opportunity for on-orbit technical demonstrations, and there has been no path to practical application. However, we were selected in 2018 to participate in the Innovative Satellite Technology Demonstration Program proposed by JAXA, and we have the opportunity to conduct on-orbit experiments with the RApid Innovative payload demonstration SatellitE-2 (RAISE-2) in 2021. However, we were selected in 2018 to participate in the Innovative Satellite Technology Demonstration Program proposed by JAXA, and we have the opportunity to conduct on-orbit experiments with the Innovative Satellite Technology Demonstration Satellite 2 in 2021. This program provides opportunities for private companies and universities to acquire and accumulate new knowledge using nano-satellites, to create future mission projects, and to conduct on-orbit demonstrations of key components and new element technologies for space systems.
Testing and Evaluation of Ultra-Thin Loop Heat Pipe as Lightweight Flexible Thermal Strap for Spacecraft
(51st International Conference on Environmental Systems, 2022-07-10) Nagano, Hosei; Mizutani, Takuji; Kajiyama, Satoshi; Akizuki, Yuki; Machida, Yoshihiro
Thermal strap with high thermal conductance are required. Usually, thermal strap is made of high thermal conductive materials such as copper, aluminum, and graphite sheet. In order to obtain high thermal conductance, the thickness of the materials is increasing, and, as a result, the weight of the strap is increasing. To avoid this problem, this work proposes to apply an ultrathin loop heat pipe (UTLHP) as a thermal strap because the LHP has characteristics of high effective thermal conductivity more than several thousand W/mK even the thickness of the LHP is below 1mm. The thickness of the UTLHP in this work is only 0.6mm, and can operate even bending condition. The UTLHP is made of six layers of pure copper foils. The wick of the UTLHP is made by etching process. Pure water with the freezing point of 0 ? is used as a working fluid. In order to apply the UTLHP to the spacecraft, following factors should be guaranteed. -The UTLHP can operate with no degradation even after the working fluid has melted. -The UTLHP can operate with no degradation even in a vibrating environment. -The UTLHP can operate without leakage under a vacuum condition. In this paper, following evaluations were conducted for the UTLHP to evaluate a potential of this UTLHP as a thermal strap for spacecraft; -Thermal performance of the UTLHP before and after freezing. -Thermal performance of the UTLHP begore and after vibration testing. -Thermal performance of the UTLHP under the vacuum condition. The details of the experimental results will be presented in the full paper.
Thermal Vacuum Testing of Advanced Thermal Control Devices for Flight Demonstration
(51st International Conference on Environmental Systems, 2022-07-10) Kajiyama, Satoshi; Mizutani, Takuji; Ishizaki, Takuya; Tomioka, Kota; Tanaka, Hiroto; Nagai, Hiroki; Matsumoto, Kan; Sawada, Kenichiro; Machida, Yoshihiro; Matsumoto, Kazuaki; Nagano, Hosei
In Japan, several unique thermal control technologies have been developed. However, there are no opportunity to demonstrate in orbit. Therefore, we have proposed to apply our thermal control devices named advanced thermal control devices (ATCD) to the Innovative Satellite Technology Demonstration Program conducted by JAXA, and accepted to apply to the Rapid Innovative payload demonstration SatellitE-2. In this paper, the test results of the thermal vacuum testing of ATCD are presented. ATCD consists of two types of flexible thermal straps: one is made of high-thermal-conductive material, and the other is made of a fluid-loop, and a re-deployable radiator. The conductive-type thermal-strap (CTS) is made of high-thermal-conductive graphite-sheets and aluminum blocks. The fluid-type thermal-strap (FTS) is made of a ultrathin loop-heat-pipe. The re-deployable radiator named reversible-thermal-panel (RTP) is made of high-thermal-conductive graphite-sheets as a flexible fin, and a shape-memory-alloy as a passive re-deployable actuator. As a result, it was confirmed that the thermal conductance between the two ends of CTS was 0.50-0.55 W/K. As for FTS, it was confirmed that it could operate even after recovering from the freezing condition of the working fluid, and that there was no leakage of the working fluid and no performance degradation under vacuum environment. As the heat load increased, the thermal conductance between the evaporator and condenser increased, and finally a thermal conductance value of 4.1 W/K (at 5 W heat load) was confirmed. For RTP, it was confirmed that the radiator fins were fully expanded to 130 when the SMA actuator reached 30 ? during heating. On the other hand, during cooling, the temperature of the SMA actuator dropped only to -15?, and the fins retracted only to 40 . Furthermore, the temperature hysteresis of the SMA actuator was estimated to be about 40? based on the experimental results.