Journal of Aeronautics and Space Technologies http://www.jast.hho.edu.tr/JAST/index.php/JAST <p>Main objective of the Hezârfen Aeronautics and Space Technologies Institute is to contribute bringing up human power that is appropriate for the needs of developing science and technology, developing international knowledge, sophisticated, using scientific knowledge creatively and having secular and democratic values in addition to respecting nation benefit.</p> <p>The Journal of Aeronautics and Space Technologies is published as an international refereed journal that consists of scientific and academic knowledge in January and July biannually by Hezârfen Aeronautics and Space Technologies Institute.</p> <p>The authors cannot make any payment for the papers published in the journal. Papers published in the journal are open access without being a member of the journal.</p> en-US <p>The manuscript with title and authors is being submitted for publication in Journal of Aeronautics and Space Technologies. This article or a major portion of it was not published, not accepted and not submitted for publication elsewhere. If accepted for publication, I hereby grant the unlimited and all copyright privileges to Journal of Aeronautics and Space Technologies.<br><br>I declare that I am the responsible writer on behalf of all authors.&nbsp;</p> <p>&nbsp;</p> ocetin@hho.edu.tr (Asst.Prof. Ömer ÇETİN) oalparslan@hho.edu.tr (Önder ALPARSLAN) Wed, 23 Jan 2019 08:46:48 +0000 OJS 3.1.1.4 http://blogs.law.harvard.edu/tech/rss 60 STRATEGY FORMULATION USING A HYBRID MCDM APPROACH FOR STRATEGIC POSITION AND ACTION EVALUATION (SPACE) MATRIX METHOD http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/340 <p><em>As the competition gets more and more fierce in today’s markets, companies have to have an effectively chosen strategy in order to acquire better place in the market in which they are active. The SPACE Matrix method was once a useful method to analyze the competitive position of an organization using internal and external dimensions. However within its basic idea it is pointed out that it has some drawbacks. Therefore it has become obsolete nowadays because of those drawbacks and in order to resuscitate it, in this study, some of those drawbacks are pointed out and a way of coping with it using well known Analytic Hierarchy Process (AHP) and Analytic Network Process (ANP) methods is presented. Thus a hybrid strategy determination tool has been presented.</em></p> Tuncay Gürbüz ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/340 Wed, 23 Jan 2019 07:03:34 +0000 Flexure Analysis of Functionally Graded Plates Using {2,2}-Refined Zigzag Theory http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/344 <p><em>This study investigates the flexure analysis of functionally graded (FG) plates using {2,2}-refined zigzag plate theory which considers transverse normal deformation along the thickness of plates. The element is free of geometric locking and does not require shear correction factors. The FG plate is composed of silicon carbide (SiC) and aluminum (Al) varying through the thickness of the plate. The volume fractions of the material constituents in the FG plate were functionally tailored according to a power-law. The effective material properties of the plate were evaluated by using the Mori-Tanaka homogenization scheme. The accuracy of the present approach was demonstrated by considering a simply supported FG plate under distributed sinusoidal load. The influence of the compositional gradient exponent on the stress and displacement distributions of the FG plate was investigated. It was observed that the compositional gradient component played a major role on the stress and displacement levels whereas the influence of the compositional gradient exponent was minor on the stress and displacement profiles. </em></p> Mehmet Dorduncu ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/344 Wed, 23 Jan 2019 07:06:49 +0000 A WIDEBAND SQUARE SPIRAL ANTENNA FOR MULTIPLE AIRBORNE APPLICATIONS http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/342 <p>In this article, we designed a wideband square spiral antenna with an impedance matching part that operated between<br>1500 – 5500 MHz (covering L, S, and C bands) for airborne uses such as Aeronautical Mobile Satellite Service, radar<br>altimeters, Microwave Landing System, and airborne weather radars. The impedance matching part was a designed<br>wideband balun. We obtained simulation results for scattering parameters, radiation patterns, antenna and system<br>input impedances and gain values. The results confirmed that the antenna showed good matching and radiation<br>characteristics within the mentioned frequency range.</p> Cihan Döğüşgen Erbaş, Ali Okatan ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/342 Wed, 23 Jan 2019 07:08:29 +0000 AN OPTIMIZATION APPROACH FOR THE DAILY PHOTOGRAPH SELECTION PROBLEM OF EARTH OBSERVATION SATELLITES http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/341 <p><em>The mission of an earth observation satellite (EOS) is to acquire images of specified areas of the Earth surface related to observation requests from customers. This paper proposes an optimization approach for the daily photograph selection problem (DPSP) of EOSs. DPSP is related to operational management of EOSs and about the scheduling of observations for an EOS. Each photograph related to a customer order generates a profit but not all of the requests can be satisfied due to some physical and technological constraints. Then the problem is to select a subset of requests of maximal profit. The proposed algorithm inherits the hyper-cube framework of ant colony optimization (ACO) metaheuristic. Realistic instances are used as benchmark problems. Computational results demonstrate that the proposed algorithm is capable of generating competitive and promising solutions.</em></p> Sezgin KILIÇ ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/341 Wed, 23 Jan 2019 07:10:40 +0000 INVESTIGATION OF THE EFFECT OF TAPER STACKING LOCATION ON AERODYNAMIC LOADS FOR ONERA M6 WING AT A FIXED ANGLE OF ATTACK http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/330 <p><em>The effect of taper stacking location for ONERA M6 wing is analyzed in terms of the lift, drag and lift-to-drag ratio. The stacking location is defined as the non-dimensional distance from the sectional leading edge to the taper axis. The non-dimensionalization is based on the sectional chord length. Different wing shapes are generated by linearly or parabolically varying the stacking location along the span. Various wing cases are investigated under the same angle of attack. The steady-state turbulent flowfields are computed by solving the Reynolds Averaged Navier-Stokes equations. The Spalart-Allmaras turbulence model with the extended wall function is used to calculate the eddy viscosity. It is observed that there exist some cases in which the values of lift, drag and lift-to-drag ratio change significantly. Moreover, the spanwise variation of the stacking location has a pronounced effect on the formation and the characteristics of the shock wave.</em></p> Mustafa Kaya, Munir Elfarra ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/330 Wed, 23 Jan 2019 07:12:56 +0000 A Visual-Inertial attitude propagation for resource constrained small satellites http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/351 <p>An accurate and efficient attitude determination system is a key component for Earth-observation small satellites. However, most of the small satellites operate without redundant attitude sensors due to the satellite’s small form factor and are therefore at a significant risk of mission failure. In this research, we propose a visual-inertial attitude propagation approach for Earth-observation small satellites. The proposed approach integrates vision-based and inertial attitude estimation methods in an unscented Kalman filter (UKF) framework. The vision-based method propagates attitude in three degrees of freedom from sequentially captured images based on Earth-observation geometrical constraints and total shift correction method. For validation of the vision-based method’s performance, we used raw imagery data of High Definition Earth Viewing (HDEV) payload of the International Space Station (ISS). The performance of the visual-inertial approach is assessed through the realistic Earth-surface scene simulations and results are compared with ground truth data.</p> Amartuvshin Dagvasumberel, Kenichi Asami ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/351 Wed, 23 Jan 2019 07:16:06 +0000 Large Eddy Simulation of a Stagnation Point Reverse Flow Combustor http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/347 <p>The complex unsteady behavior of a stagnation point reverse flow combustor (SPRF) is investigated numerically with large eddy simulation (LES) approach using an open source flow solver OpenFOAM. The SPRF combustor has a unique design where inflow and outflow ports are located in the same plane. This feature promotes stable and efficient combustion through internal gas recirculation, and also reveals a complex flow field inside the combustor. Instantaneous flow features, statistical behavior of the turbulent flow, the effect of grid resolution and energy spectrum are evaluated to study the capability of the LES approach for this combustor. The non-reacting cold flow results show overall very good agreement with experimental data, giving confidence that LES with k-equation subgrid model could be a very powerful tool for resolving such complex flow dynamics. Further analyses are extended for reacting cases to examine turbulence combustion interaction. The interaction of the flame with turbulent structures clarified the intense internal gas recirculation mechanism.</p> Mehmet ÖZGÜNOĞLU, Ayşe Gül GÜNGÖR ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/347 Wed, 23 Jan 2019 08:27:09 +0000 Synthesis and Characterization of Epoxy/Boron Nitride Composite for Aerospace Applications http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/353 <p><em>Beside extensive successful use of epoxy resins in many applications such as electronic packaging, insulation, adhesives and laminate technologies with various advantages; their low thermal conductivity and high CTE (thermal expansion coefficient) limit their performance. However, the addition of the particles into this material can significantly improve the constitutive and thermal properties. In this context, this study aims to develop an adhesive material where the epoxy resin is considered as the matrix material which is filled with Hexagonal Boron Nitride (h-BN) particles. Moreover, we characterize thermal behavior of the developed composite structure. A facile synthesis method was developed for minimizing the void formation while achieving a homogenous distribution of h-BN particles. SEM analysis has been employed to study the effect of the h-BN particles on the microstructural morphology. In addition, DMA (Dynamic Mechanical Analysis) and DSC (Differential Scanning Calorimeter) techniques were employed to examine the glass transition and viscoelastic mechanical behavior. The obtained results are consistent with the existing ones in the literature.</em></p> Tuncay Yalcinkaya ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/353 Wed, 23 Jan 2019 08:28:30 +0000 Evaluation of Two-vs-One Air Combats Using Hybrid Maneuver-Based Framework and Security Strategy Approach http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/350 <p><em>In this paper, we aim to develop a simulation platform and maneuver selection methodology for two-vs-one air combats. It consists of the aircraft performance model, aerial combat maneuvers and game theoretical decision strategy. The performance parameters of F-16 are used to implement the aircraft dynamics. The hybrid system theory underlies the modeling methodology of the aerial combat maneuvers, which are the possible options of combatants. The decision strategy is derived from security policy approach in game theory using some metrics that present the air superiority. The definitions of these metrics and evaluation strategy are presented. The verification of the models and developed decision processes are given through the simulations</em></p> Barış Başpınar, Emre Koyuncu ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/350 Wed, 23 Jan 2019 08:34:58 +0000 Frequency Analysis of Launch Vehicle Oscillation Absorbent Configuration on Performance of LPE http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/304 <p>Pogo phenomenon is considered as low-frequency instability at system level in heavy satellite launchers. This instability results from the frequency interactions between structure and propulsion subsystems. To compensate for or prevent the occurrence of this instability in a satellite launcher, an element that reduces the frequency interaction effects of these two systems is used. This element, which is known as ‘accumulator’, absorbs the pogo vibrations in satellites. In this paper, by dynamically modeling the engine elements (tank, supply line, accumulator, pump, and thrust chamber), and by considering the connection of structure to engine at two points of tank and pump, the effects of the accumulator element and parameters on the natural frequency of the propulsion system have been investigated and the considerations related to operating conditions and the placement of this element along the supply line of the propulsion system have been determined. The findings indicate that placing the accumulator near the pump assembly and along the suction path reduces the natural frequency of the propulsion system; which contributes to a greater stability of the satellite launcher. With the increase in the compliance and inertance of accumulator, accumulator’s influence on the natural frequency of the propulsion system becomes more significant.</p> Seyed Alireza Jalali Chimeh, Hassan Karimi Mazareh Shahi Karimi Mazareh Shahi, Mohammad Shafiey Dehaj ##submission.copyrightStatement## http://www.jast.hho.edu.tr/JAST/index.php/JAST/article/view/304 Wed, 23 Jan 2019 08:46:05 +0000