• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.218-225
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• 2013

Vertically-launched missiles are supported as erected vertically in the vertical launching system of warship, and they should be mounted in the same way when vibration-tested. However, mounting missiles vertically makes a fixture, which is a supporting structure, bulky and heavy so requiring a high-performance exciter. Mounting missiles as laid down horizontally in a vibration test is economical regarding fixture manufacturing and exciter performance, but it makes test results incorrect because the different mounting direction has effects on the test results. A bending moment due to missiles' weight happens to missiles, and resilient mounts, which support missiles in the vertical launch system, deflect differently from the real situation because of the static deflection of these mounts due to missiles' weight. If the resilient mounts supporting missiles have nonlinear force-deflection characteristics, vibration test results become more different from the true results. This paper proposes to support missiles with an additional resilient mount such as a bunge code in order to solve those problems coming from mounting vertically-launched missiles as laid down horizontally in vibration tests. The proposed approach enables to obtain the same test results as in their actual mounting condition even though vertically-launched missiles are mounted in a different direction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.1000-1005
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• 2003

The shock separation test simulates the environmental effects of the spacecraft separation from launch vehicle. The shock separation test for a structural model of KOMPSAT-Ⅱ(Korea Multi-Purpose SATellite Ⅱ) was performed in SITC(Satellite Integration ＆ Test Center) launch environmental test hall at KARI(Korea Aerospace Research Institute) to verify the shock test requirement of the spacecraft, to predict the induced acceleration responses on the primary structures and payloads by the explosion of pyre-lock and to perform mechanical fit check. The spacecraft with S/A was mated vertically to LV(Launch Vehicle) adapter simulator via a clamp band, then hoisted and suspended above a foam test bed by four isolation springs secured to the spacecraft hoist fittings to isolate the payload platform shock wave from the sling elements. For separation process, real pyre-devices were used and the time response signals from 60 accelerometers installed on the interested points was acquired and recorded. The SRS responses for each response channels were calculated and the achieved SRS's on the separation plane was reviewed and evaluated in comparison to the ICD(Interface Control Document) value.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.358-362
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• 2006

Pyro-shock generally refers to the severe mechanical transients caused by the detonation of an ordnance device on a structure. Such device on a structure, including linear explosive, and point explosive are widely used to accomplish in-flight separation of structural elements on aerospace vehicle. And they are a significant cause of launch vehicle failures. The launch vehicle being developed in Korea also uses the explosive for separation events. In this paper, the isolator equipped to small satellite launch vehicle made of PTFE(Teflon) is developed to reduce the separation shock. The test to measure dynamic stiffness of PTFE isolator is performed. This test enables us to find the frequency range of PTFE isolator. And,, pyre-shock test using explosive to evaluate the performance of PTFE isolator is executed. from this study, the isolator conformed to frequency range and load requirement is developed using PTFE instead of rubber.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.8
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• pp.539-545
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• 2015

Intense acoustic load is generated when a launch vehicle lifts off, causing the damaging vibrations at the launch vehicle or satellite within the fairing. This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. As a test example, the lift-off acoustic load on the Korean launch vehicle, NARO, is predicted by the existing calculation tool, the modified Eldred's second method. Although the acoustic sources, assumed as point sources, are to be located along the center line of the exhaust plume when using the Eldred's prediction method, the exact location of the deflected center line of exhaust gas flow is not usually known. To search for the most appropriate source positions, six models of source line distribution are suggested and the acoustic load prediction results from these models are compared with the actual measurements. It is found that the predicted sound pressure spectrum of the Naro is the most similar to the measured data when the centerline of the turbulent kinetic energy contour is used as the source line.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1146-1151
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• 2011

Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.153-173
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• 1993

폭약은 탄광에서 석탄이나 각종 광물을 캐거나, 건설토목현장에서 암반 제거를 위해서 주로 사용되었다. 전쟁에서 군사용으로 파괴를 위한 목적으로 사용되기도 하였으나, 최근의 동서화해 분위기와 남북통일이 무르익는 시대적 조류로 볼때 더이상 파괴용으로의 사용은 제어될 것이고 이제는 평화를 위하여, 건설을 위하여, 산업발전을 위하여 더 많이 사용되어지고 응용되어질 것이다. 작금의 첨단산업의 발달과 산업의 고도화로 우리 화약 업계에도 첨단발파기술의 개발에 많은 관심과 연구.개발을 진행중이다. 첨단발파기술의 응용사례를 소개하면, 건축토목 분야에서 노후 고층빌딩 및 굴뚝의 철거, 노후 교량 및 공장시설의 철거등에 활용되고 있으며, 위락서비스 분야에서 응용으로는 불꽃놀이를 들 수 있다. 최근에는 첨단 과학 장비를 이용하여 각종 꽃불의 모양이 음악과 미술등 예술적인 기능을 기억시킨 컴퓨터를 활용하여 보다 고차원의 공예술품(공학-예술)을 만들어낸다. 아울러 각종 기공식 발파시에도 예술적 기능과 웅장함을 가미하여 그 화려함을 극치에 다다르게 한다. 그외에도 로켓트 발사추진제등의 우주 개발에의 응용, 석유시추등 해양개발에의 응용, 각종 공학 실험연구에의 응용, 폭발 가공에의 응용, 의학에의 응용, 철강산업에의 응용 등으로 그 숫자를 이제는 일일이 나열하기 힘들 정도로 광범위해졌다.

• Journal of KSNVE
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• v.3 no.4
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• pp.300-312
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• 1993

폭약은 탄광에서 석탄이나 각종 광물을 캐거나, 건축토목 현장에서 암반제거 를 위해서 주로 사용되었다. 전쟁에서 군사용으로 파괴를 위한 목적으로 사용되기도 하였으나 최근의 동서화해 분위기와 남북통일이 무르익는 시대적 추세를 볼때 더 이상 파괴용으로의 사용은 억제될 것이고 이제는 평화를 위하여 건설을 위하여 산업 발전을 위하여 더많이 사용되어지고 응용될 것이다. 작금의 첨단산업의 발달과 산업 의 고도화로 우리 화약업계에도 최근에는 첨단발파기술의 개발에 많은 관심과 연구 개발을 진행 중이다. 첨단발파기술의 응용사례를 소개하면, 건축토목분야에서 노후 고층 빌딩 및 굴뚝의 철거, 노후교량 및 공장시설의 철거 등에 활용되고 있으며, 위락 서비스분야에서 응용으로는 불꽃놀이를 들 수 있다. 최근에는 첨단과학장비를 이용하여 각종 꽃불의 모양이 음악과 미술등 예술적인 기능을 기억시킨 케비테이션 를 활용하여 보다 고차원의 고예술품을 만들어낸다. 아울러 각종 기공식 발파시에도 예술적 기능과 웅장함을 가미하여 그 화려함을 극치에 다다르게한다. 그외에도 로켓 발사추진제등의 우주개발에의 응용, 석유시추등 해양개발에의 응용, 각종 공학실험 연구에의 응용, 폭발가공에의 응용, 의학에의 응용, 철강산업에의 응용 등으로 그 숫자를 이제는 일일이 나열하기가 힘들 정도로 광범위 해졌다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.756-762
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• 2012

A method of the low-frequency noise reduction in an enclosure by using an array of Helmholtz resonator is presented. An integral form of equation, which represents the acoustical coupling between the internal sound field and the resonator array, is formulated so that the boundary element method can be applied to solve the coupling problem. It is shown that the resonator array on the surface of the enclosure can be regarded as impedance patches on the boundary element. Experiments on a simple enclosure acoustically coupled with an array of resonators are conducted to verify the method. The predicted noise reduction by the boundary element method shows good agreement with the measured one. The effects of the resistance of resonators as well as the number of resonators on the noise reduction are demonstrated. As a practical example, the presented method is applied to the payload fairing of a space launcher with resonator arrays. It is demonstrated that the resistance of resonators affects significantly the required number of resonators to achieve a desired noise reduction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.185-188
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• 2008

This paper introduces the Bootstrap method for statistical analysis of noise and vibration spectrum in aeronautic and space fields. Generally, all components of a launch vehicle and its payloads are subjected to high intensive noise and vibration environment during the lift-off phase and the ascent phase through Mach =1 and Max Q. In order to verify their survivabilities against these severe vibroacoustic environments during qualification tests and acceptance tests, it is most important to estimate the proper upper limits of the environmental condition. Although NASA has typically utilized the Normal Tolerance Limit method in deriving these levels, the reference[1] says that the Bootstrap can be also an alternative method to estimate the maximum expected environments. In this paper, a general procedure of the Bootstrap method is summarized, and it is applied to analyze acceleration power spectral density functions, which were measured during acoustic test on the upper stage of KSLV-I.

• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.91-104
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• 2002

Jet noise of propulsion systems is major source of acoustic loads of launch vehicles and sounding rockets. The investigation of characteristics of jet noise is inevitable for successful missions. In this paper, the mechanism of generation of acoustic loads due to jet noise was investigated. The major parameters that change the characteristics of acoustic loads were also suggested so that effects of the parameters could be investigated. The temporal and spatial characteristics of acoustic loads of KSR-III was demonstrated. The results show that the maximum value of the acoustic loads is found in the octave bands whose center frequencies are 250 Hz and 500 Hz. Finally, the methods and the facilities for the further investigation of acoustic loads were proposed.