• International Journal of Aeronautical and Space Sciences
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• 제17권4호
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• pp.535-550
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• 2016

Securing the safety and the reliability of liquid-propellant rocket engines (LREs) for space vehicles is indispensable as engines consist of many complex components and operate under extremely high energy-dense conditions. Thus, health monitoring has become a mandatory requirement, especially for the reusable LREs that are currently being developed. In this context, a dynamic simulation program based on MATLAB/Simulink was developed in the current research on the Space Shuttle Main Engine (SSME), a partly reusable engine. Then, a series of fault simulations using this program was conducted: at a steady state operating condition (104% Rated Propulsion Level), various simulated fault conditions were artificially injected into the simulation models for the five major valves, the pumps, and the turbines of the SSME. The consequent effects due to each fault were analyzed based on the time responses of the major parameters of the engine. It is believed that this research topic is an essential pre-step for the development of fault detection and diagnosis algorithms for reusable engines in the future.

• 항공우주시스템공학회지
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• 제10권1호
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• pp.66-73
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• 2016

Space propulsion system produces required thrust for satellites and space launch vehicles by using chemical reactions of a liquid fuel and a liquid oxidizer typically. For example, monomethylhydrazine-dinitrogen tetroxide, liquid hydrogen-liquid oxygen and RP-1-liquid oxygen are conventional combinations of liquid propellants used for the liquid propulsion system. Among several liquid propellants, the monomethylhydrazine is expecially preferred for a satellite fuel due to its better storability in liquid phase during a relatively long mission period under a space environment. Thus, a development importance of a bipropellant system using the monomethylhydrazine fuel is recognized recently as the national space program proceeds on a large scale. The objective of the present study is to review a foreign research trend of a thermal decomposition reaction of monomethyhydrazine to understand a fundamental basis of its chemical reaction to prepare for domestic development in future.

• Journal of Astronomy and Space Sciences
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• 제22권4호
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• pp.513-526
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• 2005

본 연구의 목적은 회전안정화 우주비행체 내부에 탑재된 유동질량의 운동을 보다 광범위한 파라미터 영역에 대해 해석하고, 관련 분야에서 활용할 수 있는 적정한 설계 기준을 제공하기 위한 것이다. 문제의 해석을 위해 perturbation 기법을 이용하였고, 그 결과로 파라미터 공간에서의 안정-불안정 영역을 결정할 수 있는 Ince-Strutt 선도를 구하였다. 해석 방법 및 확보된 결과의 적정성을 입증하기 위하여 선도에서 취한 여러 파라미터 값에 대한 수치적 시뮬레이션을 수행하였다. 유동체 운동의 위상평면 분석을 통하여 수행된 해석 과정 및 결과가 적정한 것으로 입증되었으며, 회전 비행체에 탑재된 유동질량의 운동은 파라미터 값의 선택에 따라 여러 가지 형태의 안정-불안정 현상을 유발함을 알 수 있었다.

• KIEAE Journal
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• 제9권1호
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• pp.31-38
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• 2009

The purpose of this study is to present direction in outdoors space planning and design after direction through user characteristic analysis through spectacle component establishment of culture art center outdoors space through on-the-site analysis and literature investigation to culture art center of Seoul city and capital region 17 places in this research. The data was collected from classification and bisection kind, subdivision kind, and great classification composed to 17 items. User satisfaction side and Variable that is looked below satisfaction than average appeared to bench, pergola, sculpture facilities, pavement facilities, border facilities. And these facilities were analyzed dissatisfaction. When see satisfaction model, when make up culture art center or similar facilities in local government hereafter because parking facilities and rest area cause big effect in satisfaction, is judged that is item to consider most preferentially. In most case, parking lot security from outdoors space, resting place security, security of field performance facilities etc. taking a serious view because tendency that users see performance or use most vehicles except neighborhood walking area for a rest, a walk etc.. is trend. But, is judged that physical side so that can feel satisfaction as space security of quantitative side is important but users utilize substantially and side that is the program are more important in hereafter.

• 한국항공우주학회지
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• 제48권4호
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• pp.311-321
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• 2020

최근 초소형위성, 소형위성에 대한 혁신적인 기술 발전으로 인해 거대 군집임무(Mega Constellation)가 활발하게 이루어지고, 재활용 우주발사체로 인한 우주 접근 비용이 급격하게 낮아지면서, 우주 개발은 지금까지와는 다른 'New Space Age' 시대로의 전환을 앞두고 있다. 이에 따라, 활발한 우주 개발의 필연적인 부수물인 '우주쓰레기'들의 증가로 인한 우주환경 악화 문제 역시 국제적인 관심사로 떠오르고 있다. 본 논문에서는 국가 우주정책의 변화를 앞두고 우주환경 보호를 위한 국제기구들과 각 국가들의 '우주쓰레기 경감 가이드라인' 제정 내용과 동향들을 살펴보고, 국제 사회의 향후 움직임에 대해 전망하였다. 또한, 우리나라의 현실에 맞는 가이드라인 예시 및 적용 방안에 대해서도 제안하였다.

• 항공우주산업기술동향
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• 제9권1호
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• pp.3-14
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• 2011

인류의 최초 우주 비행으로부터 50년, 최초의 인공위성 발사로부터 54년이 지난 현재 인류의 우주 활동은 어느 때 보다 활발하다. 2000년대 들어 연평균 66회 발사된 우주발사체는 2010년 74회 발사되었으며, 2010년 지구 궤도에서 운행되고 있는 인공위성은 900개에 이르렀다. 우주자산은 국가의 국방 및 안보에 기여할 뿐만 아니라 사회의 경제, 기술 개발에 없어서는 안 되는 필수요소로 자리잡음에 따라 국가가 투자할 가치가 있는 중요 부분이 되었다. 2010년 세계 각국의 우주개발 예산은 715억 달러로 역사상 최대치에 도달하였다. 2002년 이후 세계 우주개발 예산은 연간 8%의 증가율을 보였으나, 2010년 2%로 낮아져 투자 증가율은 다소 둔화되었다. 반면 우리나라의 2011년 정부의 우주개발 예산은 1,825억원으로 2008년 이후 연평균 16%로 감소하였다. 천리안 위성 및 나로호 개발이 완료됨에 따라 개발주기에 따른 예산감소의 영향으로 분석된다. 본 논문에서는 세계 각국 및 우리나라의 우주분야 투자와 우주시장 현황을 정리하였고, 우리나라 예산정책에 관한 시사점을 제고해보았다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.257-261
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• 2005

Over the past 30 years, numerical methods and simulation tools for fluid dynamic problems have advanced as a new discipline, namely, computational fluid dynamics (CFD). Although a wide spectrum of flow regimes are encountered in many areas of science and engineering, simulation of compressible flow has been the major driver for developing computational algorithms and tools. This Is probably due to a large demand for predicting the aerodynamic performance characteristics of flight vehicles, such as commercial, military, and space vehicles. As flow analysis is required to be more accurate and computationally efficient for both commercial and mission-oriented applications (such as those encountered in meteorology, aerospace vehicle development, general fluid engineering and biofluid analysis) CFD tools for engineering become increasingly important for predicting safety, performance and cost. This paper presents the author's perspective on the maturity of CFD, especially from an aerospace engineering point of view.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.59-64
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• 2003

Recently, as people pay attention to the environmental pollution, the emissions of diesel engine have been a serious problem. We carried out the performance evaluation test of Diesel Oxidation Catalysts (DOC) for HSDI diesel engine equipped vehicles. The DOC, basically coated with Pt catalyst, was manufactured with various washcoat materials. It was found that CO conversion efficiency depends on temperature, but THC conversion efficiency is dominated by temperature and space velocity. The THC and CO conversion efficiencies of aged catalysts were increased with additions of $ZrO_2$ and zeolite B in the washcoat. We found that DOC performance changes with coating techniques, even through it has same washcoat materials. The DOC coated by high temperature washcoat coating technology showed good conversion efficiency than low temperature washcoat coated DOC.

• 대한산업공학회지
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• 제24권1호
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• pp.77-93
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• 1998

It is discussed how to locate idle vehicles of AGVS on unidirectional guide paths. The problem is modeled as a median location problem on a cyclic network. The characteristics of the optimal location are analyzed and some useful properties are suggested to reduce the solution space. Based on the properties found, several special types of networks - a pure single-loop type, the loop type with a single branching intersection and the loop type with local branching node - are also analyzed as well as the general cyclic network. In each case of the networks, a solution procedure is suggested. Some numerical examples are provided to illustrate the algorithms developed.

• 한국경영과학회지
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• 제23권1호
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• pp.17-28
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• 1998

This study suggests a procedure for designing cellular manufacturing systems (CMS) which are combined with automated guided vehicles (AGVs) using a tandem configuration. So far most of the previous studies have dealt with conventional design problems not considering the layout and the characteristics of transporters used in CMS. A mathematical model is developed using the service time to perform material transfers as a suitable meassure. The service capacity of AGVs and space limitations are also reflected in this model. As the model can be shown strongly NP-hard, a heuristic algorithm is presented, in which each cell is temporarily formed using both the set covering model and similarity coefficients, and then locations of the cells are determined by means of tabu search and finally machine perturbations are carried out. An example problem is solved to demonstrate the algorithm developed.