Browsing by Author "Tomioka, Kota"

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Evaluation of Thermal Control Mirror with Tunable Thermo-optical Properties for Radiowave Transmissive Multilayer Insulation
(46th International Conference on Environmental Systems, 2016-07-10) Tomioka, Kota; Honjo, Taisei; Tachikawa, Sumitaka; Kawahara, Kousuke; Nagasaka, Yuji
Multilayer Insulation (MLI) is the most common thermal control element on spacecraft. It is composed of multiple layers of low emittance polyester films with a vacuum-deposited aluminum finish and an aluminum coated polyimide film with low solar absorptance is often used for an outer cover. Above that, MLI does not exhibits transmissivity to radiowave for using metal coated films. For radiowave transmissivity, these materials of MLI should be metal-free. We have been developing a new thermal control mirror (COSF: Controlled Optical Surface Films). COSF consists of a polyimide film for substrate and dielectric multilayer coating on it. The solar absorptance and infra-red emissivity of COSF can be freely controlled by the interference of its dielectric multilayer. This multilayer is designed by using a Genetic Algorithm (GA) method. COSF was proposed in 2009 and 2010 as a new thermal control mirror with tunable thermo-optical properties. After that, COSF has been improved with not only thermo-optical properties but also radiowave transmittance. On the other hand, polyimide form (PI-F) has also been studied. PI-F has high heat resistance, light weight and high resistance to space environment. New multilayer insulation with polyimide form (PF-MLI) has been constructed and was evaluated in 2011 and we confirmed its insulation performance would be better than that of conventional MLI. Now we have been developing two types of COSF (COSF4 and COSF-IR). COSF4 exhibits low solar absorptance, high infra-red emissivity and high transmittance to radiowave. COSF-IR exhibits low infra-red emissivity and high transmittance to radiowave. These two materials are not composed of metal and they can be applied for multilayers of PF-MLI instead of conventional metal coated films. This new insulator exhibits a radiowave transmissivity. This paper shows the measurement results of thermo-optical properties and the radiowave transmittance of COSF4 and COSF-IR.
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.