• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.648-653
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• 2014

Fly-wheel, gimbal antenna, mechanical gyro and cryocooler with moving parts generate a micro-vibration during their on-orbit operation. For the acquisition of high quality image of observation satellite, additional technical efforts are required to reduce the micro-vibration level from the vibration sources. In this study, we proposed a passive isolation system combined with a tuned mass damper-type energy harvester to generate electrical energy from the micro-vibration which has always been subjected to useless isolation objectives. The feasibility of the system has been investigated through the numerical simulation.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.75-76
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• 2008

전력거래소는 전격계통 안정된 운영과 공정한 전력시장 운영을 주요 임무로 하며, 이를 위하여 전국의 80여개의 발전소와 600여개 변전소로부터 발전량, 전압, 조류, 자단기 상태정보 등 다양한 전력계통 자료를 취득하고 있다 전력거래소의 중앙급전소에는 이와 같은 계통자료 취득은 물론 발전량 제어기능을 수행하기 위한 에너지관리시스템(이하 EMS 라 한다)을 운영하고 있으며, 발,변전소에는 현장의 전력설비와 연결되어 계통자료를 취득하여 EMS로 전송하는 원격소장치 (이하 RTU 라한다)를 운영하고 있다. 자료취득 경로는 모든 발전소와 34skv급 이상의 변전소의 경우 EMS와 RTU가 직접 연결되어 자료를 취득하며 154Kv급 이하 변전소는 12개 지역급전소의 자료취득제어시스템(이하 SCADA라 한다)를 경유하여 자료를 취득하고 있다. 전력계통의 대형화와 복잡화에 따라 계통해석기능 자동발전제어기능에 의한 계류운영으로 정보기술에 대한 의존도가 증가하고 있으며, 변동비 반영시장의 개선운영에 따라 공정한 전력시장 운영과 안정된 전력계통 운영을 위해 전력계통 취득자료의 신뢰도가 요구되고 있다. 따라서 EMS를 비롯한 RTU, 통신망 등 전력계통 자료취득 설비의 운영실적을 분석하여 각 시스템별 고장 고장원인 고장유형 등을 고찰하므로써 시스템 성능개선을 위한 설비투자와 운영개선에 반영하고자 한다.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.1
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• pp.50-60
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• 2015

A propulsion system of a satellite provides a necessary thrust to reach to the final orbit after a separation from a launch vehicle. Also, it supplies pulse moments to maintain the satellite in a mission orbit and for its attitude controls during a mission life time. The present study investigates the development trend of bipropellant rocket engines for an orbit transfer and an attitude control of a satellite using monomethylhydrazine and hydrazine for fuel and dinitrogen tetroxide for oxidizer to derive fundamental specifications which are necessary for domestic development researches. Also, their major performance characteristics are summarized.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.87-95
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• 2012

This technical paper describes the analysis results of telemetry data for the initial activation of star trackers for an agile high accuracy low earth orbit satellite. The satellite was recently launched and is in the Launch and Early Operation Phases. It uses two SED36 star trackers manufactured by SODERN. The star tracker is separated by three parts, an optical head, an electronics box, and a baffle with maintaining optical head base plate temperature 20 degC in order to achieve the better performance in low frequency error. This paper presents the initial activation status, requirements and performance, anomaly occurrence, and noise equivalent angle performance analysis during the mission mode by processing the telemetry data.

• Journal of the Korea Society for Simulation
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• v.23 no.4
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• pp.151-161
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• 2014

It is very important to evaluate proper acquisition of military aircraft against future threats in our military defense field. In previous studies, the evaluation has been determined in terms of tasking order or weapon power index. These methods compare the combat-effectiveness index and the number of aircraft. However, this study provides simulation analysis of proper quantity decision based on actual operational senarios of military aircraft using System Dynamics. The method reflects the properties of military aircraft operation concepts and considers the rate of failure of main systems on subsystems, as well as repair and crash rates caused by differentials in peacetime and wartime frame.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.87.1-87.1
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• 2010

국립고흥청소년우주체험센터는, 우리나라 청소년들에게 우주에서 벌어지는 제반 현상과 천체의 실상을 접하게 하고 또 그 현상과 천체 이면에 자리한 기본 원리를 체험과 실험을 통하여 스스로 터득하게 함으로써 저들을 우주시대를 이끌어갈 창조적 인재로 양성함을 목적으로, 2010년 7월 9일에 개원한 특성화 체험 국립 시설입니다. 우리나라 청소년들이 센터에 설치된 주요 우주체험장비 7종을 활용하여 우주왕복선과 우주정거장에서의 임무수행을 경험하며, 우주왕복선 지상통제센터 요원의 역할 및 우주선이나 항공기의 직접 조종도 체험 할수 있다. 또한 달의 저중력 상황을 체험해 볼 수 있다. 지름 15미터의 천체투영관이 12월 말에 완공될 예정이다. 하늘전망대에는 구경 14인치 광학망원경과 다수의 중소형 망원경들이 설치된다. 또한 우주인 기초체력단련훈련을 할 수 있는 야외 활동 공간을 확보하고 있다. 센터의 우주체험시설과 천문학 관련 시설들은 앞으로 청소년의 우주에 대한 관심을 유발하고 국민들의 과학에 대한 이해를 돕는데 크게 기여할 것으로 기대된다. 현재 4개의 과정으로 우주체험캠프 프로그램을 구성하여 운영하고 있다. 또한, 2009년 개정 지구과학 교육과정과 연계한 우주체험프로그램을 개발 중이다. 여기서는 본 센터의 우주체험시설물 소개와 이들을 활용한 체험활동과 교육 현황 및 계획을 소개하고자 한다.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.27-41
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• 2012

In this paper, there is analyzed the disturbances to impact on COMS attitude and the attitude error using the received telemetries in KARI ground station during normal mode of COMS. COMS was launched successfully at Kourou, French Guiana on the 26th of June, 2010. Up to now after IOT(in-orbit test), COMS is performing well the main mission to measure meteorology and ocean during about half and one year. The disturbances to impact on COMS attitude are mostly by the Sun, by the motion of payload mirror and by the spike happened during operation of earth sensor mirror and wheel. The analysis result on the other cases happened rarely during the nominal operation, is summarized.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.722-730
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• 2015

Drive mechanism of multi-axis pintle thrusters for DCS(Divert Control System) was designed to meet the needs of minimizing the number of driving motors. In this study, preliminary model was designed in order to implement appropriate pressure control and thrust distribution. Based on the preliminary model study, the drive mechanism for DCS multi-axis pintle thrusters using piston was designed and evaluated by using AMESim software. Results show that three driving motors are enough to actuate four pintle thrusters.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.97-102
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• 2004

Propulsion System provides the required velocity change impulse for orbit transfer from parking orbit to mission orbit and three-axis vehicle attitude control impulse. KOMPSAT-2 propulsion system(PS) is an all-welded, monopropellant hydrazine system. The PS consists of the subassemblies and components such as Thrusters, Propellant Tank, Pressure Transducer, Propellant Filter, Latching Isolation Valves, Fill/Drain Valves, interconnecting propellant line assembly, and thermal hardwares for operation-environment control of the PS. This paper summarizes a development process of the liquid propulsion system from the design engineering up to the test and evaluation.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.109-116
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• 2004

In a satellite time management system, the GPS-based clock synchronization technique[1] has the merits of precision time management by knowing the time difference or the error between the OBT(On Board Time) of the internal processors and GPS time every second. It can be realized employing the DPLL(Digital Phase Loop Lock) and FEP(Front End Processor) circuitry for the clock synchronization[2]. In this paper, a refined DPLL & FEP scheme is proposed to provide the precision, stability and robustness of the operation, which is to compensate the errors and noise of the GPS signal, and also to cope with the case when the GPS signal is lost due to several reasons. The simulation and HIL (Hardware In the Loop) test results using the FM(Flight Model) in the course of KOMPSAT-2(Korea Multi Purpose Satellite-2) design and development are illustrated to demonstrate the salient features of this methodology.