• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.11
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• pp.1056-1062
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• 2008

The interaction between thrust plume and satellite base region was investigated by using direct simulate Monte-Carlo calculations. For the accurate simulation of N2 and H2 collisions and rotation-translation transition, a variable soft-sphere model and a recent rotational relaxation model of N2 and H2 were used. For the investigation of the interaction between thrust plume and base region, the number density distribution for each species, translational and rotational temperature distributions, heat flux, and pressure were examined by direct simulation of Monte-Carlo calculations. It was found that most of the surface properties are affected by H2 collisions and a strong non-equilibrium state is observed at the base region. It was demonstrated that an accurate model is needed to simulate H2 collisions and the rotation-translation transition. The results by the present calculation are more accurate than previous direct simulation Monte-Carlo calculations because more accurate rotational relaxation models were used in simulating the inelastic collisions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.7
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• pp.137-143
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• 2002

This paper concerns the spin-stabilization for the second stage of KSR-III(Korea Sounding Rocket-III). The error sources in the second stage are defined, and then the effect on attitude error of KSR-III is analyzed quantitatively and qualitatively. Based on the analysis, some conditions for optimal spinning frequency and optimal steady-spinning duration are suggested. Among several solutions, an optimal value can be determined in the point of minimum impact-point error. An approach to a sub-optimal solution is also suggested. Application to the KSR-III shows that a proper spinning frequency and a steady-spin duration to give the smallest impact-point error can be effectively determined.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.27-34
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• 2004

A computational study on the supersonic flow around the lateral jet controlled missile has been performed. For this purpose a three dimensional Navier-Stokes computer code(AADL3D) has been developed and case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body for several parameters such as angles of attack, circumferential jet positions, and spouting jet angles. Missile surface is divided into four regions with respect to the center of gravity, and the normal force and moment distribution at each region are compared. The results show different behavior of the normal force and moment variation according to each parameter. Furthermore, it is shown that the pitching moment can be minimized through proper combination of each parameter.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.333-342
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• 2016

Liquid rocket propulsion is a system that produces required thrust for satellites and space launch vehicles by using chemical reactions of a liquid fuel and a liquid oxidizer. Monomethylhydrazine/dinitrogen tetroxide, liquid hydrogen/liquid oxygen and RP-1/liquid oxygen are typical combinations of liquid propellants commonly used for the liquid rocket propulsion system. The objective of the present study is to investigate useful design and performance data of liquid rocket engine by conducting a numerical analysis of thermochemical reactions of liquid rocket propellants. For this, final products and chemical compositions of three liquid propellant combinations are calculated using equilibrium constants of major elementary equilibrium reactions when reactants remain in chemical equilibrium state after combustion process. In addition, flame temperature and specific impulse are estimated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.585-589
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• 2010

It is important for the liquid rocket engine to meet the exact performance requirements in order to guarantee the successful mission of the launch vehicle. Usually, a ground combustion test for the engine is conducted to reduce the performance error and for the tuning. For the gas-generator (GG) cycle engine, this adjustment process can be easily tuned by means of the control valves. A linearized correlation between the process parameters of the control - the combustion chamber pressure and the mixture ratio of engine - and the independent parameter of the control- rotational angle of the control valve - could be suitable to reduce the tuning errors. Also this linearity can reduce the effort for the tuning and make the process more explicit by ensuring a more intuitive control. In this point, we proposed an algorithm in the frame of the in-house-developed program to obtain the control valves' inherent characteristics which satisfy the linearity.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.67-75
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• 2004

It is essential to develop a transient analysis model for the turbopump-fed type liquid rocket engine development, especially for deriving the number of test and its parameters. In this study we proposed a mathematical model of turbopump-fed type liquid rocket engine, and inspected transient mode changes of a rocket engine according to variations of thrust control valve opening ratio. To verify the results, we solved the same problem with AnaSyn software from Russia, and concluded that the results of transient code we developed deviated within 2% from AnaSyn results. Also, using the transient engine analysis code we showed the possibility to find out the system level design Parameters of the components. For example, we modeled a pressure stabilizer which is used to control the consistency of mixture ratio in the gas generator as forced damping system, and found the stability range of the natural frequency and the damping ratio with the transient engine system analysis code.

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.83-83
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• 2004

상용프로그램인 AMESim을 이용하여 제어밸브 성능시험설비에 대한 Transient 구간에서 문제점 발생 확인과 동시에 시스템에 최적화를 통한 비용 절감효과를 위해 본 Simulation을 수행하였다. 가압 자동 조절 시스템은 직렬식과 병렬식 두 가지에 대해 고려했을 경우 직렬식이 더 타당함을 확인하였고, 특히 Tank Ullage의 압력 분포를 보면 직렬식에서 Fluctuation이 약 $\pm$0.2%이고, 병렬식에서 약 $\pm$0.7%가 됨을 보았다. (중략)

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.74-74
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• 2004

액체추진제를 사용하는 위성 발사체의 경우 추진제탱크에 저장된 추진제를 추력을 발생하는 연소실에 공급하기 위하여 헬륨 등의 가압제를 사용한다. 본 연구에서는 액체추진제 로켓엔진의 산화제인 극저온의 액체산소를 저장하고 있는 탱크 내부에 설치된 별도의 탱크에 저장된 극저온/고압의 헬륨을 고온으로 열팽창 시켜 추진제 탱크로 재유입하여 추진제를 가압하는 시스템에 사용되는 가압제 열팽창용 열교환기의 개발을 위한 기초 설계를 수행하였다. (중략)

• Aerospace Industry
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• s.108
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• pp.66-67
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• 2010

수직이착륙, 영어로는 VTOL(Vertical Take-Off and Landing)이라 불리는 기술은 공기역학을 거부한 첨단 항공우주기술이다. 일반적으로 고정익 항공기는 날개에서 발생하는 양력으로 하늘을 날지만 VTOL 항공기는 순수한 엔진 추력만으로 수직으로 이착륙하거나 단거리에서 이륙할 수 있다. 다만 높은 기술적 완성도를 요구하는 만큼 현재까지 실전 배치된 군용기 중 이 기술이 적용된 군용기는 해리어(Harrier)와 V-22 오스프리(Osprey), Yak-38 정도가 고작이다. 수직이착륙 기술에 대해 소개한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.35-35
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• 1999

최근 미사일 및 차세대 비행체에는 초기 고기동이나 무수한 제어력의 특성을 지닌 TVC 시스템이 많이 사용되고 있다. 기존의 공력 조타에 의한 비행 자세 제어방법은 속도의 2승에 비례하는 제어력을 발생하지만, TVC(Thrust Vector Control)를 이용하면 추력 방향을 변경하여 제어력을 얻음으로써 방향 제어에 보다 월등한 성능을 발휘할 수 있기 때문이다. TVC를 이용한 방향제어는 저속도 경우와 공기가 희박한 고 고도에서도 충분한 제어력을 얻을 수 있다. 그러나 그 우수성에 비추어 국내에서는 아직 그 성능에 대해 충분한 자료가 없는 실정이다.