• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.517-526
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• 2019

In the present study, unsteady flows around a projectile ejected from an aircraft platform have been numerically investigated by using a three dimensional compressible RANS flow solver based on unstructured meshes. The relative motion between the platform and projectile was described by six degrees of freedom(6DOF) equations of motion with Euler angles and a chimera technique. Initial behavior of the projectile for varying conditions, such as roll and pitch-yaw command on the control surface of the projectile, flight Mach number, and platform pitch angle, was investigated. The ejection stability of the projectile was degraded as Mach number increases. In the transonic condition, the initial behavior of the projectile was found to be unstable as increase of platform pitch angle. By applying the command to control surfaces of the projectile, initial stability was highly enhanced. It was concluded that the proposed simulation data are useful for estimating the ejection behavior of a projectile in design phase.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.4
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• pp.245-255
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• 2019

This paper describes on aerodynamic analysis based on the truncation rate of guided-weapon nose using computational fluid dynamics. The shape to perform the analysis is only the body of the guided weapon and the diameter to length ratio is 10.7. Three nose shapes were selected and hemisphere, 25% and 50% truncation were compared. For the accurate CFD analysis of the body, the grid method and the analytical method were selected and verified using NASA wind tunnel test data. For the three nose shapes, the drag analysis for the flight Mach number is 6~20% different. This difference was analyzed by the pressure distribution from nose to base.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.1
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• pp.63-73
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• 2021

This paper presents a algorithm for automatic target recognition robust to the influence of the flame in order to track the target by EOTS(Electro-Optical Targeting System) equipped on UAV(Unmanned Aerial Vehicle) when there is aerial target or marine target with flame at the same time. The proposed method converts infrared images of targets and flames into a gradient vector field, and applies each gradient magnitude to a polynomial curve fitting technique to extract polynomial coefficients, and learns them in a shallow neural network model to automatically recognize targets and flames. The performance of the proposed technique was confirmed by utilizing the various infrared image database of the target and flame. Using this algorithm, it can be applied to areas where collision avoidance, forest fire detection, automatic detection and recognition of targets in the air and sea during automatic flight of unmanned aircraft.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.1
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• pp.21-30
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• 2021

Mid-course trajectory of the missiles equipped with seeker should be designed to detect target within FOV of seeker and to maximize the maneuverability at the point of transition to terminal guidance phase. Because the trajectory optimization problems are generally hard to obtain the analytic solutions due to its own nonlinearity with several constraints, the various numerical methods have been presented so far. In this paper, mid-course trajectory optimization problem for boost-glide missiles is calculated by using SOCP (Second-Order Cone Programming) which is one of convex optimization methods. At first, control variable augmentation scheme with a control constraint is suggested to reduce state variables of missile dynamics. And it is reformulated using a normalized time approach to cope with a free final time problem and boost time problem. Then, partial linearization and lossless convexification are used to convexify dynamic equation and control constraint, respectively. Finally, the results of the proposed method are compared with those of state-of-the-art nonlinear optimization method for verification.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.7
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• pp.539-547
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• 2021

Helicopter rotor blade is required to be designed by considering the interacting effects among aerodynamics, flexibility, and controllability. The reverse design allows the structural components to have common characteristics by using the configuration numerics and experimental results. This paper aims to design the composite rotor blade which will feature common characteristics with that of BO-105. The present engineering design procedure is done by dividing the rotor blade into a few sections and composite laminates across the cross section. For each section, variational asymptotic beam sectional analysis (VABS) program is used to evaluate its flapwise, lagwise, and torsion stiffnesses to have discrepancy smaller than certain tolerance. Finally, CAMRAD II is used to predict the stress acting on the rotor blade during the specific flight condition and to check whether the present deign is structurally valid.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.1
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• pp.41-52
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• 2021

During atmospheric ascent of a launch vehicle, airborne acoustic loads act on the vehicle and its effect becomes pronounced at transonic speed. In the present study, acoustic loads acting on a hammerhead launch vehicle at a transonic speed have been analyzed using ��-ω SST based IDDES and the results including mean Cp, Cprms, and PSD are compared to available wind-tunnel test data. Mesh dependency of IDDES results has been investigated and it has been concluded that with an appropriate turbulence scale-resolving computational mesh, the characteristic flow features around a transonic hammerhead launch vehicle such as separated shear flow at fairing shoulder and its reattachment on rear body as well as large pressure fluctuation in the region of separated flow behind the boat-tail can be predicted with reasonable accuracy for engineering purposes.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.527-532
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• 2020

Seoul terminal maneuvering area (TMA) that includes Incheon International Airport (ICN) and Gimpo International Airport is a very congested airspace with around 1,000 daily flights and the airspace blocked at the boundary between Incheon flight information region (FIR) and Pyongyang FIR. Consequently, with frequency radar vectorings, separation assurance in this airspace is complicated thus resulting in higher controller workload. In this paper, the conflict and collision risks in Seoul TMA are analyzed using recorded ADS-B data for past three years. Using the recorded trajectories, original flight plan procesures and routes are reconstructed and the risks are quantified using detect and avoid well clear (DWC) metric that is developed for large unmanned aircraft system. The region west of ICN was found to be the highest risk area regardless of the runway directions. In addition, merge and crossing points between procedures displayed relatively high risks.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.4
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• pp.281-290
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• 2021

For successful operations of an airborne Active Electronically-Scanned Array (AESA) radar, which has various advantages over traditional radar systems, accurate and robust navigation is critical. This paper discusses a study on the performance analysis of an integrated navigation based on the Embedded GPS/INS (EGI) system for an aircraft equipped with an AESA radar. The models for generating the inputs for the GPS/IMU are developed. A navigation filter for a loosely-coupled GPS/IMU system is constructed. Overall navigation performance assessment procedure using a six degree of freedom aircraft simulator - along with the GPS/IMU models and the navigation filter - is introduced. The steps of the performance analysis procedure are explained using a comprehensive case study.

• Journal of Aerospace System Engineering
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• v.16 no.2
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• pp.13-24
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• 2022

As the scale of airborne system software increases, the use of OOT (Object-Oriented Technology) is increasing for functional expansion, efficient development, and code reuse, but the verification method for airborne object-oriented software is conducted from the perspective of the existing procedure-oriented program. The purpose of this paper was to analyze the characteristics of OOT and the vulnerabilities derived from the functional characteristics of OOT, and present a verification method applicable to each software development process (Design, Coding and Testing) to ensure the functional safety integrity of aviation software to which OOT is applied. Additionally, we analyzed the meaning of the static analysis results among the step-by-step verification measures proposed by applying LDRA, a static analysis automation tool, to PX4, an open source used to implement flight control software.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.5
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• pp.297-308
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• 2022

Most air-breathing aircraft operated in the hypersonic region are equipped with a scramjet engine. In a scramjet engine, a shock wave generated at an inlet acts as a compressor for a general gas turbine engine instead, so total pressure loss caused by the shock wave is considered very important. In this study, to minimize total pressure loss, a method of designing an external compression inlet using isentropic compression surface was proposed, and an external compression inlet with 3-deflection angles and Busemann inlet were designed under the same conditions. After that, through computational analysis, the performance characteristics at off-design conditions were compared. Each inlet shape was truncated according to the length of the 3-ramp external compression inlet, and the boundary layer correction was performed. The isentropic external compression inlet showed superior performance at the design point, but under the off-design conditions, its performance was degraded compared to the 3-ramp external compression inlet.