• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.106-115
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• 2010

Because of space limitations, interferences between antennas of the KSLV-I communication systems occur and their effects become worse during all sorts of tests such as the flight test using a light plane. In this paper, coupled signal magnitude is calculated using the FDTD method. The theory of the FDTD, absorbing boundary condition, source input technique, and post processing of data are explained. The calculated coupling factor between two IFAs, which have 2 GHz resonance frequency and placed 5 cm apart, is -12.7 dB. Applied coupling calculation method can be effectively used for KSLV-I performance analysis, subsystem design, antenna arrangement, and communication link budget for the next space launch vehicle.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.125-129
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• 2006

Japan has been investigating a new satellite based positioning system called Quasi-Zenith Satellite System (QZSS). Since the improvement of positioning availability in urban area is one of the most important advantages of the QZSS, multipath mitigation is a key factor for the QZSS positioning system. Therefore, Japan Aerospace Exploration Agency (JAXA) and GNSS Inc. have commenced the R&D of a pseudolite, which transmits the next-generation signal such as BOC(1,1), in order to evaluate the effect of multipath on the new signal. A prototype BOC pseudolite was developed in 2005, and ground tests showed a capability of generating proper pseudorange. Also, preliminary flight experiments using a pseudo quasi-zenith satellite, a helicopter on which the pseudolite is installed, were conducted in early 2006, and the BOC-type correlation function was monitored in real time.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.9
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• pp.707-714
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• 2016

This paper describes analysis results of vibration characteristics and modal test for a small-scale quad-rotor drone. The rotor arm has a slender body with a propeller and motor at its tip. Rotor system generates excitation for an unbalanced mass. Therefore, the drone platform is involved in the possibility of resonance. For advance identification of the possibility of resonance, confirmation of eigen-mode being closest to the propeller operation range is necessary. Material properties of CFRP tubes used for the rotor arm were acquired by finding the natural frequency based on Rayleigh method. A simplified quad-rotor FE model consisting of rotor arm assembly with tip mass was built to perform numerical analysis, and a free-free boundary condition was applied to provide flight status. Modal tests for the actual platform with impact hammer instrument were performed to verify analysis results. Separation margin from hazardous eigen-mode was checked on the propeller operation range.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.616-624
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• 2019

In order to understand flying aircraft, satellite, missile, etc, a telemetry ground system is used to receive, record, and process the transmitted radio signal from vehicles. In some cases, a line-of-sight communication is not possible along to the trajectory of vehicles, and multipath fading result in a shade area of communication. A number of telemetry ground systems are installed to overcome this limitation, and acquire the transmitted signal seamlessly. The telemetry signals received by multiple independent ground systems have independent probability of errors since they experienced their own communication channels. In other words, we can exploit the independent error characteristics of received signals by processing them in a hybrid method. The optimum hybrid post-process method is proposed in this study, and applied to process telemetry signals acquired from flight tests.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.346-357
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• 2008

Endothermic fuels are known as a probable fuel for hypersonic atmospheric flight vehicles and advanced propulsion systems, as well as cryogenic fuels. Especially, from the standpoint of the advanced regenerative cooling use, they are quite useful as a coolant fuel because of their large heat sink due to their chemical decompositions; so-called endothermic cooling effect. However, no heat transfer equations have been proposed taking into account such endothermic reactive behaviors concretely. This paper describes an analytical method for evaluation of the heat transfer rates between endothermic reacting coolant fuel and coolant-side wall in the regenerative cooling passages. Heat transfer mechanism is indicated based on a classical transport-phenomenological approach. A new relational expression of Nusselt number ratio for forcedconvective heat transfer with such endothermic reactions is also proposed by theoretical approaches using some classical hypotheses. Its applicability is assessed provisionally by comparison with confirmed results of heated tube tests for supercritical JP-7 fuel carried out at NASA Lewis Research Center, using its heat sink characteristics evaluated by United Technologies Research Center(UTRC). As a result, it has been suggested that the proposed relational equation is applicable to the evaluation of enhancement of Nusselt numbers due to such reactions in developed turbulent flows such as in the regenerative cooling passages.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.215-218
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• 2011

An air data acquisition algorithm has been developed for the supersonic flow at the preliminary design stage with pressure data acquisition device composed of major three total pressure sensors and two static pressure sensors. Through this algorithm, Mach number, angle of attack and sideslip angle can be very easily derived with simple interpolation algorithm and predefined data tables. In this preliminary design stage, to verify the developed algorithm, the data tables are constructed with data driven by Taylor Maccoll equation. Furthermore, these data are compared and modified with computational results based on CFD analysis. The present algorithm would be useful to get supersonic air data for the various aerial vehicles and their flight tests.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.776-783
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• 2018

This paper proposes an improved test and evaluation methodology to be conducted for a in-flight threat-countermeasure encounter scenario. Although the conventional test method adopted in the precedent researches allows high precision and safety, such full-scale method is practically not appropriate to apply to small-scale test rounds for evaluating the subparts of the ammunition. To address this problem, this study suggests a readily-applicable, small-scale test and evaluation method of the subpart of the ammunition in firing test. In the threat-countermeasure encounter scenario, the results of several tests demonstrate that the proposed technique does not deteriorate the precision when the engagement point should be adjusted.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.4
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• pp.12-20
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• 2020

The purpose of this study was to analyze the face validity of the revised EPTA (English Proficiency Test for Aviation) to see if the tests actually contribute to the enhancement of aviation safety and achieve the purpose of the assessment. In order to reach the above objectives, 103 pilot test takers were surveyed, and nine in-depth interviewees were selected and interviewed. In addition, detailed research results were derived by dividing the participants into the pilot's flight experience (31 captain pilots, 42 first officer pilots, and 30 general commercial pilots). As a result, pilot participants were generally aware that EPTA was more reasonable because the revised EPTA properly implemented the aviation situation and gave participants motivation to learn aviation English. It was also seen that first officer pilots had a higher face validity of EPTA than captain and general commercial pilots. The reason was that first officer pilots considered air traffic control job was more important than other pilots did.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.10
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• pp.669-676
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• 2022

In this paper, the carriage load analyses of stores installed on aircraft are conducted to validate the chimera grid method applied to an unstructured CFD solver, UMSAPv. First, the chimera grid method of UMSAPv is verified for the well-known Eglin Wing/Pylon/Finned store problem. Next, an angle of attack sweep of F/A-18C clean configuration is conducted at a subsonic speed. The computed results are compared with the results of the previous study using MSAPv, a structured CFD solver, to show the validity of Umsapv. Finally, the carriage of F/A-18C JDAM is carried out with a chimera grid as well as a single block grid. The computed results are compared with other computational, experimental and the flight tests.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.5
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• pp.476-486
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• 2022

Synthetic dynamic infrared image generation from the given virtual environment is being the primary goal to simulate the output of the infra-red(IR) camera installed on a vehicle to evaluate the control algorithm for various search & reconnaissance missions. Due to the difficulty to obtain actual IR data in complex environments, Artificial intelligence(AI) has been used recently in the field of image data generation. In this paper, CycleGAN technique is applied to obtain a more realistic synthetic IR image. We added the Structural Similarity Index Measure(SSIM) loss function to the L1 loss function to generate a more realistic synthetic IR image when the CycleGAN image is generated. From the simulation, it is applicable to the guided-missile flight simulation tests by using the synthetic infrared image generated by the proposed technique.