• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.1-7
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• 2017

The performance of a MEMS solid propellant thruster was predicted and analyzed through internal ballistics model and CFD analysis. The nozzle throat was $416{\mu}m$, and the area ratio of the nozzle was 1.85. As a result of the internal ballistics model, chamber pressure increased up to 197 bar and the maximum thrust was 3,836 mN. In CFD analysis, the chamber pressure of the internal ballistics model was applied as the operating pressure, and the CFD model was divided into an adiabatic and a heat loss model. As a result, the maximum thrust of the adiabatic model was 14.92% lower than that of the internal ballistics model, and the effect of heat loss was insignificant.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.7
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• pp.845-850
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• 2015

Love which is one of the emotional of mankind, has been studied in sociology and psychology as a matter of great concern. Through such a research, the researchers have provided the basic mathematical model for love model, we cannot find nonlinear characteristics through the basic love model. Therefore, in this paper, in order to find nonlinear behaviors in the basic love model, we apply external force to the basic love model. Then we confirm the existence of nonlinear behaviors through time series and phase portrait. We also confirm that this nonlinear behaviors have the periodic doubling, chaotic phenomena and periodic process which are very similar to typical chaotic occurrence phenomena.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.76-85
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• 2014

In this paper, the equivalent coefficient of thermal expansion (CTE) of fiber reinforced plastic composite material is investigated with various CTE prediction schemes. Although there are several methods for predicting the equivalent CTEs, most of them have some limitations of are not much accurate when comparing prediction results with test results. In the framework of computational homogenization, a representative volume element is taken from the predefined fiber-volume ratio, and modelled with finite element mesh. Finally, the equivalent CTEs are obtained by applying periodic boundary condition. To verify the performance of the proposed method, the results obtained are compared with those by the existing methods and test results. Additionally, the thermal pointing error analysis for star tracker support structure is conducted and its accuracy is estimated according to CTE prediction schemes.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.1-9
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• 2023

Recently, as Synthetic Aperture Radar (SAR), communication, and signal surveillance missions of spacecraft have become more advanced, research has been actively conducted on the deployable large mesh antenna system with excellent storage efficiency compared to the deployment area, and light weight. Deployable Mesh antennae are characterized by an increase in the number of Openings Per Inch (OPI), which is a measure of mesh weaving density as the mission frequency band increases, and this OPI change directly affects the thermal optical properties of the mesh antenna, so research on this is required. In this paper, to verify the thermal relationship between the optical properties of the mesh and antenna reflector, thermal sensitivity analysis between the mesh and the antenna reflector is performed by in-orbit thermal analysis with various optical characteristics of the mesh based on existing overseas research cases. In addition, the temperature gradient effect of the mesh reflector is analyzed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.11
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• pp.921-930
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• 2013

Satrec Initiative successfully developed and verified a high-resolution electro-optical camera system, EOS-D Ver.1.0. We designed this system to give improved spatial and radiometric resolution compared with EOS-C series systems. The thermal control subsystem (TCS) of the EOS-D Ver.1.0 uses heaters to meet the opto-mechanical requirements during in-orbit operation and uses different thermal coatings and multi-layer insulation (MLI) blankets to minimize the heater power consumption. Also, we designed and verified a refocusing mechanism to compensate the misalignment caused by moisture desorption from the metering structure. We verified the design margin and workmanship by conducting the qualification level thermal vacuum test. We also performed the verification of thermal math model (TMM) by comparing with thermal balance test results. As a result, we concluded that it faithfully represents the thermal characteristics of the EOS-D Ver.1.0.

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.153-160
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• 2006

A Protomodel Space Infrared Cryogenic System (PSICS) cooled by a stirling cry-ocooler has been designed. The PSICS has an IR sensor inside the cold box which is cooled by a stirling cryocooler with refrigeration capacity of 500mW at 80K in a vacuum vessel. It is important to minimize the heat load so that the background thermal noise can be reduced. In order to design the cryogenic system with low heat load and to reduce the remained heat load, we have performed numerical analyses. In this paper, we present the design factors and the results obtained by the thermal analysis of the PSICS.

• Korean Journal of Remote Sensing
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• v.21 no.4
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• pp.253-271
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• 2005

We have analyzed surface water temperature and seasonal stratification of lakes in the Han river system using time-series Landsat images and in situ measurement data. Using NASA equation, at-satellite temperature is derived from 29 Landsat-5 TM and Landsat-7 ETM+ images obtained from 1994 to 2004, and was compared with in situ surface temperature on river-type dam lakes such as Paro, Chuncheon, Euiam, Chongpyong, Paldang, and with 10m-depth temperature on lake-type dam lake Soyang. Although the in situ temperature at the time of satellite data acquisition was interpolated from monthly measurements, the number of images with standard deviation of temperature difference (at-satellite temperature - in situ interpolated temperature) less than $2^{\circ}C$ was 24 on which a novel statistical atmospheric correction could be applied. The correlation coefficient at Lake Soyang was 0.915 (0.950 after correction) and 0.951-0.980 (0.979-0.997 after correction) at other lakes. This high correlation implies that there exist a mixed layer in the shallow river-like dam lakes due to physical mixing from continuous influx and efflux, and the daily and hourly temperature change is not fluctuating. At Lake Soyang, an anomalous temperature difference was observed from April to July where at-satellite temperature is $3-5^{\circ}C$ higher than in situ interpolated temperature. Located in the uppermost part of the Han river system and its influx is governed only by natural precipitation, Lake Soyang develops stratification during this time with rising sun elevation and no physical mixture from influx in this relatively dry season of the year.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.9
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• pp.789-794
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• 2014

The FPGA is used to the high speed digital satellite communication on the Digital Signal Process Unit of the next generation GEO communication satellite. The high capacity FPGA has the high power dissipation and it is difficult to satisfy the derating requirement of temperature. This matter is the major factor to degrade the equipment life and reliability. The thermal control at the equipment level has been worked through thermal conduction in the space environment. The FPGA of CCGA or BGA package type was mounted on printed circuit board, but the PCB has low efficient to the thermal control. For the FPGA heat dissipation, the heat sink was applied between part lid and housing of equipment and the performance of heat sink was confirmed via thermal vacuum test under the condition of space qualification level. The FPGA of high power dissipation has been difficult to apply for space application, but FPGA with heat sink could be used to space application with the derating temperature margin.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.2
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• pp.157-164
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• 2012

The design strategy of the multi-functional structure is that the electrical components and the circuits are directly put on their supporting structural panel in which the radiation shields and the thermal control functions are integrated. Applying the multi-functional structure reduces the total mass and size of the space system and makes it possible to lower launch cost. In present study the performance of thermal radiation for six types of multi-functional structure are investigated by the numerical method. The effect of the rib configuration on heat transfer for the multi-functional-structure is not important alone but is meaningful considering with the structural stiffness, difficulty of manufacturing and mass increase. In heat spreading point of view, the thickness of the outer conductive layer is important rather than the rib configuration and the trade-off study with the mass and thickness is required for optimum design.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.55.2-55.2
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• 2010

한국천문연구원은 과학기술위성 3호의 주탑재체인 다목적 적외선영상시스템(Multipurpose Infra-Red Imaging System, MIRIS)을 개발하고 있다. 이 연구개발 사업은 2007년 교육과학기술부의 과학위성 3호 사업 주탑재체 공모를 통하여 10여개의 후보 탑재체 제안서 중에서 최종적으로 채택되었고, 2011년 발사를 목표로, 3년 동안의 연구개발 기간을 거쳐 현재 비행모델 (FM, Flight Model) 개발이 진행 중이다. MIRIS는 한국천문연구원이 개발하여 2003년 발사에 성공한 과학위성 1호 주탑재체인 원자외선 영상분광기 (FIMS, Far ultra-violet IMaging Spectroscope)에 이어 국내에서 자체 개발되는 두 번째 우주망원경이다. MIRIS는 우주공간에서 0.9~2 micron 사이 적외선 영역의 파쉔 알파 방출선 (Paschen Alpha Emiision Line)과 광대역 I, H 파장영역을 관측할 예정이다. 주요 과학임무로는 아직까지 국제 천문학계에서 잘 알려지지 않은 우리은하 내부에 분포한 고온 플라즈마 (Warm Ionized Medium, WIM)의 기원 연구와 아울러 우리은하 성간난류(Interstellar Turbulence)의 특성 및 적외선 우주배경복사의 (Cosmic Infrared Background; CIB) 거대구조 등을 관측연구할 예정이다. 특히 MIRIS는 저온상태 (절대온도 77K, 약 $-200^{\circ}C$)에서 우주공간 관측을 수행할 예정이므로, 국내에서는 연구기반이 취약한 극저온 광학계 및 기계부 설계기술, 극저온 냉각기술 및 열해석 설계기술과 적외선 센서기술 및 자료처리 기술 등 관련기술을 개발하고 있으며 이러한 기반기술을 바탕으로, 아직까지 국내에서 시도된 바 없는 적외선우주망원경 개발을 통하여, 우리나라의 관련 우주기술 분야의 기초원천 기술로서 크게 활용될 것으로 기대하고 있다.