• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.5
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• pp.36-52
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• 2021

As the application of nano-satellites constellation increases worldwide in the wake of New Space era, there is growing demand for the development of thrusters for precise attitude and orbit control of small satellites. Field Emission Electric Propulsion(FEEP) thruster uses a liquid metal as a propellant and accelerates the ionized liquid metal through a strong electric field at the tip of the metal surface. FEEP thruster technology is suitable for nano-satellites which require various missions for attitude and orbit control, because it provides thrust ranging from 1 µN to 1 mN with high specific impulse up to about 10,000 s and can be miniaturized due to its simple structure. In this paper, the basics of FEEP thrusters are introduced, then the current status of research and development of FEEP thrusters are presented.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.12
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• pp.1112-1115
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• 2016

Global Positioning System(GPS) is a useful system used in both civilian and military applications. However, the signal of GPS is susceptible to jamming attacks due to low receive sensitivity, since the signals come from the satellite located at over 20,000 km above the earth. In this paper, we have conducted a preceding research on a non-Foster matching circuit that efficiently matches an electrically ultra-small GPS antenna. Electrically Small Antennas(ESAs) are inefficient radiators and are difficult to match in wideband due to extremely high quality factor. In order to match small GPS antenna in wideband, a non-Foster matching circuit for a small GPS antenna was designed. A negative impedance converter circuit consisting of Linvill's cross-coupled pair transistors was fabricated and its stability was verified by the time-domain stability analysis. In addition, anechoic chamber measurements show that the non-Foster matching circuit for small GPS antenna can lead bore-sight gain improvement by more than 17 dB.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.4
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• pp.311-321
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• 2020

With the recent breakthrough in technology for micro-satellite, small satellite, and mega constellation missions, and the cost of accessing space from recycled space launch vehicles sharply lowered. Thus, space development is set to make a transition to a new space age that is different from before. Accordingly, the problem of worsening space environment conditions due to the increase in space debris, an inevitable adjunct to active space development, is also emerging as an international concern. In this paper, the contents and trends of international organizations for the protection of the space environment and space debris mitigation guidelines of each country were reviewed and forecast the future movement of the international community. In addition, it is suggested example of guidelines that fit the reality of Korea and how to apply them.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.106-114
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• 2005

This study addresses space simulation test results and thermal modelling verification of HAUSAT-2 nanosatellite STM (Structural-Thermal Model). The thermal modelling of the HAUSAT-2 has been modified in accordance with test results. Thermal analysis results were repeatedly compared with test results for modified thermal modelling. It is verified that the analysis results for modified thermal modelling agree well with test results. Some surface heaters were implemented to simulate solar illumination for HAUSAT-2 Thermal Vacuum/Balance Test. A low-cost and effective thermal test methodology, which is applicable to ultra-small satellite system, was proposed and verified by test results in this study.

• Journal of Space Technology and Applications
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• v.3 no.3
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• pp.213-228
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• 2023

Unmanned exploration rovers serve as tools for investigating mineral resources, mining, and carrying out various scientific on celestial bodies beyond Earth, acting on behalf of humans. Recently, not only the United States but also other countries such as Japan, India and China have been attempting to develop unmanned planetary exploration rovers for space development or have successfully operated them on other celestial bodies. This has accelerated the enthusiasm for space exploration and development. However, the development and operation of unmanned rovers for planetary exploration still entail significant costs and high risks, making it difficult for universities or companies to undertake such project independently without the guidance of financial backing from government entities. In this paper, we describe the recent development trends of micro-rovers, known as Cube Rovers, which inherit the concepts and definitions of traditional Cube Sat. We also introduce the potential and expectations of Cube Rovers through the necessity of their development and ongoing planetary exploration cases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.75-79
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• 1991

고도로 산업화가 진행됨에 따라 회전기계는 더욱 중요시되고 있으며 이의 성능 향상에 부단한 노력이 경주되고 있다. 특히 우주 시대의 개막과 더불어 우주선 및 인공위성에 사용하기 위해 초소형이며 초고속의 고성능회전모타 를 개발하기에 이르렀다. 한 예로서 미국립항공우주국(NASA)의 스페이스셔 틀에 사용되는 주엔진 터보펌프를 들 수 있는데 이 터보펌프는 접시만한 크 기로써 71000마력을 생성해 낸다. 이러한 가공할 만한 에너지 밀도와 유량을 감당해 내려면 종래의 회전기계보다는 훨씬 더 높은 회전속도를 가져야 한 다. 이러한 회전체는 큰 관성부하와 진 동 및 동안정성의 문제등을 내포하고 있다. 고성능 회전기계의 또다른 예로서 초정밀 가공용 공작기계를 들 수 있 다. 선반 혹은 밀링머신으로 초정밀가공을 행하기 위해서는 회전축의 진동이 극히 작아야 한다. 이와 같이 오늘날 갈수록 초고성능 초정밀도를 추구함에 있어서 회전축의 진동을 현장에서 모니터링하고 이 진동데이터를 분석하여 회전축을 제어하는 것이 강력히 요구되어진다. 따라서 in-situ 측정이 중요성 을 띠게 되었는데 이는 제어기술의 바탕이 되는 자료를 현장에서 제공할 수 있기 때문이다. 회전축 진동측정의 대상이 되는 것들은 모타, 발전기, 엔진 및 터빈등을 대표적으로 들 수가 있다. 여기서 소형회전기계의 축표면과 같 이 비교적 곡면을 이루고 있는 부분의 진동변위 측정에 신중한 고려가 요구 되어 진다. 이는 축의 곡면도에 따라 감도가 변화하기 때문이다. 따라서 평 판에 대한 calibration 챠트를 회전기계축진동 변위환상에 이용하면 곡률에 따라서 오차가 생기게 된다. 본 연구에서는 비접촉 축진동측정시 발생되는 오차에 대하여 검토하고자 한다. from the studies, the origin of ${\alpha}$$_1$peak was attributed to the detrapping process form trap with 2.88[eV] deep of injected space charge from the chathode in the crystaline regions. The origin of ${\alpha}$$_2$ peak was regarded as the detrapping process of ions trapped with 0.9[eV] deep originated from impurity-ion remained in the specimen during production process of the material, in the crystalline regions. The origin of ${\beta}$ peak was concluded to be due to the depolarization process of "C=0"dipole with the activation energy of 0.75[eV] in the amorphous regions. The origin of ${\gamma}$ peak was responsible to the process combined with the depolarization of "CH$_3$", chain segment, with the activation energy of carriers from the shallow trap with 0.