• Title/Summary/Keyword: National Defense and Aerospace

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Ultra Precision Machining of Injection Mold Core for Asymmetric Aspheric Lens using 6:4 Brass (비대칭비구면 렌즈 사출 코어용 6:4 황동 초정밀 형상 가공)

  • Lee, Dong-Kil;Gu, Hal-Bon;Kim, Jeong-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.427-427
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    • 2007
  • The global applications of aspherics surfaces will expand rapidly on the electronics, optical components, communications, aerospace, defense, and medical optics devices etc. Especially, Asymmetric aspheric prism lens is one of the important parts in HMD(Head Mounted Display) because it affects dominantly on the optical performance of HMD. The mold core is the most important device to produce the plastic lenses by injection molding method. In this study, the mold cores for asymmetric aspheric prism lens were processed using fly-cutting method which is kind of the ultra precision processing and form accuracy and surface roughness of the cores were measured.

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A Systems Engineering Process Refinement : Focused on Technical Process (시스템 엔지니어링 공통 프로세스 개선 연구 : 기술 프로세스를 중심으로)

  • Lee, Taekyong;Lee, Joong-Yoon
    • Journal of the Korean Society of Systems Engineering
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    • v.13 no.1
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    • pp.41-50
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    • 2017
  • Systems engineering is being applied to various fields of industry such as national defense, aerospace, transportation, railway, and information technology industries. But in Korea, systems engineering has been selectively applied to government-driven projects such as space rocket development projects and unmanned flight development projects. And systems engineering processes introduced from international systems engineering standards has been directly applied to those projects. Unfortunately, this application method is not recommended as it requires highly experienced systems engineers. From our previous paper, we have proposed that domain specific engineering standards should be developed to be used as references for development of organizational engineering guide, so that more successful engineering performances can be achieved. And in this paper we have proposed a refinement of systems engineering processes from international systems engineering standards as they are bases of domain specific engineering standards.

Design of CCV adaptive flight control system under microburst type disturbances

  • Uchikado, Shigeru;Kanai, Kimio;Osa, Yasuhiro;Tanaka, Kanya
    • 제어로봇시스템학회:학술대회논문집
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    • 1994.10a
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    • pp.271-276
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    • 1994
  • In this paper we deal with a design of CCV adaptive flight control system having adaptive observer under the mircroburst circumstances. First, based on the observerbility indices of the controlled system, which is a general multi-variable one, the adaptive observer is constructed, and the unknown interactor matrix can be estimated by using the identified parameters. Next, CCV adaptive flight control law is calculated based upon the estimated ones. Finally, the proposed CCV adaptive flight controller is applied to STOL flying boat and numerical simulations under the microburst circumstances can be show to justify the proposed scheme.

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Trend of Space Development and Issue (우주개발동향과 주요 이슈)

  • Cho, Hong-Je;Shin, Yong-Do
    • The Korean Journal of Air & Space Law and Policy
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    • v.29 no.1
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    • pp.97-126
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    • 2014
  • October 4, 1957 the Soviet Sputnik 1 was launched into space the first time in the history of mankind. After launching, the realm of humankind was expanded to space. Today all countries of the world wage a fierce competition in order to utilize space for various purposes. World powers of space such as United States, Russia, China, and Japan, put reconnaissance satellites and ocean surveillance satellites into orbit, being able to easily see equipment and troops movement on earth. Each country makes efforts to occupy space assets through the militarization of space and expand national interests. Recently private companies or individuals involved in commercial space activities are becoming more prevalent. Thus, in addition to space activities for military purposes, commercial space activities become widespread. Individuals and private companies as well as nations are also involved in space activities. Outer space is not the monopoly of space powers such as the United States and Russia. The whole human race can benefit from free access to space, being the common heritage of mankind. In particular, outer space becomes an indispensable element of military activities and human life. Many countries are now entering space development, putting a lot of budget into new development programs. Republic of Korea also built the Narodo Space Center, starting its space development with budget and manpower. We have to find out ways to use space not only for military purposes but also for commercial space activities that can contribute to the national economy. In addition, through the joint efforts of the international community, we have to make efforts for preservation and peaceful use of space. Various issues relating to space activities and research should be studies in order to contribute to the progress of humanity. Those issues include the definition of outer space, space debris reduction and environmental conservation issues, non-bind measure cooperation - European International Code of Conduct, space law and national legislation related empowerment issues, arms control measures in space, and restrictions on the use of nuclear fuel. We also need to be involved in the discussion of those issues as one of responsible space countries. In addition, we try to find out regional cooperation schemes such as the ESA in the Europe actively. Currently in the Northeast Asia, cooperation bodies led by Japan and China respectively, are operated in the confrontational way. To avoid such confrontation, a new cooperative body needs to be established for cooperation on space exploration and information. The system to allow the exchange of satellite information for early warning of natural disasters needs to be built as well. In addition, efforts to enhance the effectiveness of the relevant international treaties on space, and fill in the blanks in international space laws should be made at the same time. To this end, we have to do a leading role in the establishment of standards such as non-binding measures (resolution) - Code of Conduct, being discussed in the UN and other organizations, and compliance with those standards. Courses in aerospace should be requires in law schools and educational institutes, and professional manpower need to be nurtured. In addition, the space-related technology and policy needs to be jointly studied among the private, public, and military groups, and the cross exchange among them should be encouraged.

Computational and Experimental Investigation of Thermal Flow Field of Micro Turbojet Engine with Various Nozzle Configurations (노즐 형상 변경에 따른 마이크로 터보제트 엔진의 열유동장에 관한 전산해석 및 실험적 연구)

  • Lee, Hyun-Jin;Lee, Ji-Hyun;Myong, Rho-Shin;Kim, Sun-Mi;Choi, Sung-Man;Kim, Won-Cheol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.2
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    • pp.150-158
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    • 2018
  • Numerical simulation and experimental study on the thermal flow field of the micro turbojet engine have been carried out for the purpose of developing infrared reduction technology for aircraft. A circular basic nozzle and five rectangular nozzles with different aspect ratio were considered. The conditions for CFD analysis were derived from the analysis of the engine performance. The temperature distribution of the nozzle plume was measured using a temperature sensing system. The thrust of the rectangular nozzle with the aspect ratio 5 was reduced about 1.8% compared to the circular nozzle, and the thrust decreased with increasing the aspect ratio of the nozzle. In the case of thermal flow field, it was observed that, as the aspect ratio increases, the exhaust plume in the experiment was formed wider than in the CFD analysis.

Kinematic Optimization and Experiment on Power Train for Flapping Wing Micro Air Vehicle (날갯짓 초소형 비행체의 끈을 이용한 동력 전달 장치에 대한 기구학적 최적화 및 실험)

  • Gong, Du-Hyun;Shin, Sang-Joon;Kim, Sang-Yong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.4
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    • pp.289-296
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    • 2017
  • In this paper, geometrical optimization for newly designed flapping mechanism for insect-like micro air vehicle is presented. The mechanism uses strings to convert rotation of motor to reciprocating wing motion to reduce the total weight and inertial force. The governing algorithm of movement of the mechanism is established considering the characteristic of string that only tensile force can be acted by string, to optimize the kinematics. Modified pattern search method which is complemented to avoid converging into local optimum is adopted to the geometrical optimization of the mechanism. Then, prototype of the optimized geometry is produced and experimented to check the feasibility of the mechanism and the optimization method. The results from optimization and experiment shows good agreement in flapping amplitude and other wing kinematics. Further research will be conducted on dynamic analysis of the mechanism and detailed specification of the prototype.

Statuses of World Governments' Space Activities and Space Markets in 2011 (2011년 세계 각국의 우주분야 투자 및 우주산업 현황)

  • Choe, Nam-Mi
    • Current Industrial and Technological Trends in Aerospace
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    • v.9 no.1
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    • pp.3-14
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    • 2011
  • The current space activities are soaring ever since the first human flight to outer space 50 years ago and the first satellite launch 54 years ago. 74 space launch vehicles were launched in 2010, up from average 66 yearly in 2000s, and 900 operational satellites are currently in orbit around Earth. Space has become a worthwhile investment for governments as space assets become vital to national social, economic, and technological development as well as contributing their national defense and security program. The world governments' investments on space programs have reached a historical peak of $71.5 billion in 2010. However, the growth of government funding for space has slowed down posting only a 2% growth rate since 2009 while 9 % compound annual growth rate experienced by world's space expenditures between 2004 and 2009. Korea invested $158 million in 2011, experienced strong decrease with a 16% compound annual growth rate since 2008. In this paper the current statuses of world governments' funding for space program and space market were presented and the current issues on the Korean space budget policy were reviewed.

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An Experimental Study on Performance of a Miniaturized Exploding Foil Initiator using VISAR (VISAR를 활용한 초소형 EFI 기폭 장치의 성능 특성 연구)

  • Yu, Hyeonju;Jang, Seung-gyo;Kim, Kyu-Hyoung;Yoh, Jai-ick
    • Journal of the Korean Society of Propulsion Engineers
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    • v.21 no.5
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    • pp.80-87
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    • 2017
  • The performance of a pyrotechnic device that consists of donor/acceptor pair separated by a bulkhead relies on shock attenuation characteristics of the gap material and shock sensitivity of the donor and acceptor explosives. In this research, a micro Kapton flyer was accelerated by an exploding foil initiator (EFI) to figure out shock sensitivity of hexanitrostilbene (HNS) to impact. The averaged shock pressure and duration imparted to the explosive by flyer impact are measured by using a velocity interferometer for any reflector (VISAR) and impedance matching technique. Consequently, this research shows the possibility to determine the critical flyer velocity for initiating the miniaturized pyrotechnic unit by determining the relations between the impact velocity, the amplitude and width of impact loading.

Prediction and Validation of Design Loads of Satellite Components Using Modal Mass Acceleration Curve (모달 질량 가속도 곡선을 이용한 인공위성 탑재품의 설계하중 예측 및 검증)

  • Go, Myeong-Seok;Lim, Jae Hyuk;Kim, Kyung-Won;Hwang, Do-Soon;Oh, Hyunung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.9
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    • pp.739-748
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    • 2021
  • This paper discusses the prediction and validation of design loads of satellite components using modal mass acceleration curve (Modal MAC). To calculate the acceleration upper bound of the satellite components subjected to the launch environment by the Modal MAC, the parameters of SpaceX Falcon 9 launch vehicle were used, and the acceleration upper bound curve in the modal domain was derived. After that, the maximum acceleration loads applied to the satellite components were predicted by combining Modal MAC with the spacecraft interface loads of the satellite/launch vehicle and modal information of the satellite. In addition, the accuracy of the Modal MAC was validated through comparison with the results of the coupled loads analysis using a simple satellite and launch vehicle model.

Hydrodynamic Analysis on Shock-induced Detonation in Pyrotechnic Initiator (파이로테크닉 착화기의 충격파 전달에 의한 폭굉 반응 해석)

  • Kim, Bohoon;Kang, Wonkyu;Jang, Seung-gyo;Yoh, Jai-ick
    • Journal of the Korean Society of Propulsion Engineers
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    • v.20 no.5
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    • pp.19-30
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    • 2016
  • We presented a hydrodynamic modeling necessary to accurately reproduce shock-induced detonation of pyrotechnic initiator. The methodology for such numerical prediction of shock propagation is quite straight forward if the models are properly implemented and solved in a well-formulated shock physics code. A series of SSGT(Small Scale Gap Test) and detailed hydrodynamic simulation are conducted to quantify the shock sensitivity of an acceptor that contains 97.5% RDX. A TBI(Through Bulkhead Initiator) system, consisting of a train configuration of Donor(HNS+HMX) - Bulkhead(STS) - Acceptor(RDX), were investigated to further validate the interaction between energetic and non-reactive materials for predicting the detonating response for successful operation of such small pyro device.