• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.16-23
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• 2006

A study on the boundary layer behavior of an NACA 0012 airfoil at low Reynolds numbers was investigated in order to gain knowledge of a boundary layer that might be employed in a turbine blade and MAVs. A hot-wire anemometer was used to measure the boundary layer of an NACA 0012 airfoil at static angles of attack ${\alpha}$=$0^{\circ}$, $3^{\circ}$, and $6^{\circ}$, and Reynolds Numbers Re=$2.3{\times}10^4$, $3.3{\times}10^4$, and $4.8{\times}10^4$. The results of this study show that the laminar boundary layer on the airfoil surface is attached to the surface at ${\alpha}$=$0^{\circ}$, and the laminar separation of the boundary layer on the airfoil surface occurs at ${\alpha}$=$3^{\circ}$. Furthermore, the reattachment of the boundary layer in the present study occurs for the cases of Re=$3.3{\times}10^4$ and Re=$4.8{\times}10^4$at ${\alpha}$=$6^{\circ}$.

• Transactions of the KSME C: Technology and Education
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• v.2 no.1
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• pp.29-37
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• 2014

In this study, analyzed the aerodynamic characteristics of Kline-Fogleman airfoils and wings with those more efficiency at low Reynolds number. It was found that lift to drag ratio is enhanced in the range of Reynolds number below $2.4{\times}10^5$, especially, can be improved up to 26% at Reynolds number is $1{\times}10^4$. It was confirmed that the most advantage case in terms of lift-to-drag ratio is Middle case and lift-to-drag ratio is improved to 20% at 80% of the wing area is Kline-Folgeman airfoil. At this time, endurance time increase to 12%. Also taking the structural stability of the wing and lift-to-drag improvement into account, designed to be from 50% to 80% the size of the Kline-Fogleman Airfoil would be advantageous.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.6
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• pp.438-445
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• 2019

In this paper, we present a new approach to extract the g-sensitivity scale-factor error for a MEMS gyroscope. MEMS gyroscopes, based on the use of both angular momentum and the Coriolis effect, have a g-sensitivity error due to mass unbalance. Generally, the g-sensitivity error is not considered in general use of gyroscopes, but it deserves our attention if we are to develop for tactical class performance and reliability. The g-sensitivity error during vehicle flight increases navigation error; so it must be analyzed and compensated for the use of MEMS IMU for high dynamics vehicle systems. Therefore, we analyzed how to extract the g-sensitivity scale-factor error from the inertial sensor error model. Furthermore we propose a new method to extract the g-sensitivity error using flight motion simulator. We verified our proposed method with experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.3
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• pp.274-280
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• 2016

Hinge driving type holding and release mechanism based on the burn wire release for application of cubesat is main payload of STEP Cube Lab. (Cube Laboratory for Space Technology Experimental Project) to be launched at 2015. It has high constraint force, low shock level as well as surmounting drawbacks of conventional nichrome burn wire release method that has relatively low constraint force and system complexity for application of multi-deployable systems. In this paper, we have proposed a flight model of holding and release mechanism for the verification of the constraint force and deployment status signal acquisition. To validate the effectiveness of the flight model, launch and on-orbit environment verification test have been performed.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.47.4-47.4
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• 2009

초소형전기기계시스템(MEMS: Micro-Electro-Mechanical Systems) 기술로 제작된 마이크로미러 어레이를 장착한 MEMS 우주망원경은 특유의 광시야각 감시, 목표 확인, 확대 및 고속 추적 기능을 가지며 고층대기에서의 초대형 방전현상과 같이 넓은 영역에서 드물게 임의로 일어나는 섬광현상을 관측하기에 최적이다. 러시아 과학위성 Tatiana-2의 주 탑재체로 선정된 극소형 MEMS 우주망원경 MTEL(MEMS Telescope for Extreme Lightning)은 광시야각 감시와 목표 확인을 위한 트리거망원경, 목표 확대와 고속추적을 위한 확대망원경 및 섬광현상의 분광측정을 위한 분광계로 구성되어 있다. 1년간의 개발 및 성능 검증 후 MTEL은 위성탑재를 위한 모든 우주인증 시험을 성공적으로 마쳤다. 현재 MTEL은 Tatiana-2 위성에 탑재되어 있으며, 9월 18일에 우주로 발사되어 1-3년간 800km 궤도를 비행하며 지구 대기에서 발생하는 섬광현상을 관측할 예정이다. 이 발표에서는 MTEL 탑재체의 설계, 제작, 성능 측정 및 calibration 결과를 보고하고, 위성탑재를 위한 진동 및 충격, 열, 진공 및 전자기파 적합성 등의 우주인증 시험 결과 또한 보고한다. 또한 발사 후 과학위성 및 MTEL의 이 발표 때까지의 우주에서의 상황을 보고한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.103-113
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• 2004

The satellite is exposed to the severe vibration environments such as random vibration environments such as random vibration, acceleration, shock, and acoustics during launch ascent and transportation. It is also faced with various space environments such as thermal vacuum, radiation and microgravity during the mission life. The satellite should be designed, manufactured, assembled and tested to be able to endure in these harsh environments. This paper addresses the results of the structural and thermal design and analyses for the HAUSAT-1 picosatellite which is scheduled to launch in the first quarter of 2005 by Russian launch vehicle "Dnepr". The qualification vibration and thermal vacuum tests have been conducted and passed at the satellite level to ensure that the HAUSAT-1 mechanical system was designed to be stable with enough margin.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.9
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• pp.854-864
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• 2016

The use of small drone platform has become a popular topic in these days but its application for SAR operation has been little known due to the burden of the payload implementation. Drone platforms are distinguished from the conventional UAV system by the increased vulnerability to the turbulences, control-errors and poor motion stability. Consequently, sophisticated motion compensation may be required to guarantee the successful acquisition of high quality SAR imagery. Extremely limited power and mass budgets may prevent the use of additional hardwares for motion compensation and the difficulty of SAR focusing is further aggravated. In this paper, we have carried out a feasibility study of mico-SAR drone operation. We present the image acquisition results from the preliminary flight tests and a quality assessment is followed on the experimental SAR images. The in-flight motion errors derived from the unique drone movements are investigated and attempts have been made to compensate for the geometrical and phase errors caused by motions against the nominal trajectory. Finally, the successful operation of drone SAR system is validated through the focussed SAR images taken over test sites.