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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Aeronautical and Space Sciences
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The Korean Society for Aeronautical & Space Sciences
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Volume & Issues
Volume 10, Issue 2 - Nov 2009
Volume 10, Issue 1 - May 2009
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Effect of the Stagnation Temperature on the Normal Shock Wave
Zebbiche, Toufik ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 1~14
DOI : 10.5139/IJASS.2009.10.1.001
When the stagnation temperature increases, the specific heat does not remain constant and start to vary with this temperature. The gas is perfect, it's state equation remains always valid, except, it was called by gas calorically imperfect or gas at high temperatures. The purpose of this work is to develop a mathematical model for a normal shock wave normal at high temperature when the stagnation temperature is taken into account, less than the dissociation of the molecules as a generalisation model of perfect for constant heat specific. A study on the error given by the perfect gas model compared to our model is presented in order to find a limit of application of the perfect gas model. The application is for air.
Efficient Aerodynamic Computation of a Wing Model Considering Body Effect for the Aeroelastic Application
Lee, Seung-Jun ; Im, Dong-Kyun ; Lee, In ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 14~19
DOI : 10.5139/IJASS.2009.10.1.014
The typical aeroelastic analysis for a complex configuration such as a complete aircraft was done using the aerodynamic results of the wing and the structural modes of a complete aircraft; that is, the aerodynamics of a wing of a complete aircraft is assumed to be not much influenced by the body shape. Nevertheless, the body shape can cause a distortion of aerodynamic pressure on the wing surface and it is necessary to investigate the body effect in flutter analysis. In this reseasrch, MGM inverse design method is applied to include the body effect of a wing-body model which disturbs the pressure distribution on the wing surface.
Investigation of the Downwash Induced by Rotary Wings in Ground Effect
Tanabe, Yasutada ; Saito, Shigeru ; Ooyama, Naoko ; Hiraoka, Katsumi ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 20~29
DOI : 10.5139/IJASS.2009.10.1.020
There are concerns about the influence of the gust wind caused by helicopters affecting the moving vehicles while hovering over the road during rescue activities. For the understanding of such complicated flow. numerical simulation of a rotor hovering above the ground has been carried out, changing the rotor/ground clearances. The rotor thrust is kept constant. and the rotor control is determined by trim adjustments incorporated into the CFD algorithm. Collective pitch angle and the required power decreases with the rotor/ground clearance which agrees with experience. Changes of the flowfield near the rotor with regard to the rotor height are investigated based on the calculated results.
Nonlinear Formation Guidance Law with Robust Disturbance Observer
Shin, Hyo-Sang ; Kim, Tae-Hun ; Tahk, Min-Jea ; Hwang, Tae-Won ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 30~36
DOI : 10.5139/IJASS.2009.10.1.030
Many formation guidance laws have been proposed for VAV formation flight. Since most autonomous formation flight methods require various active communication links between the vehicles to know motion information of other vehicles, damage to the receiver or the transmitter and communication delay are critical problem to achieve a given formation flight mission. Therefore, in this point of view, the method that does not need an inter-vehicle communication is preferred in the autonomous formation flight. In this paper, we first summarize the formation guidance law without an inter-vehicle communication using feedback linearization and sliding mode control proposed in previous study. We also propose the modified formation guidance law with robust disturbance observer, which can provide significantly better performance than previously mentioned guidance law in case that other vehicles maneuver with large accelerations. The robust disturbance observer can estimate uncertainties generated by acceleration of leader vehicle. By eliminating the uncertainties using the estimated uncertainties, VAVs are able to achieve the tight formation flight. The performance of the proposed approach is validated by numerical simulations.
UAV Conflict Detection and Resolution Based on Geometric Approach
Park, Jung-Woo ; Oh, Hyon-Dong ; Tahk, Min-Jea ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 37~45
DOI : 10.5139/IJASS.2009.10.1.037
A method of conflict detection and resolution is described by using simple geometric approach. Two VAVs are dealt with and considered as point masses with constant velocity. This paper discusses en route aircraft which are assumed to be linked by real time data bases like ADS-B. With this data base, all DAVs share the information each other. Calculating PCA (Point of Closest Approach), we can evaluate the worst conflict condition between two VAVs. This paper proposes one resolution maneuvering logic, which can be called 'Vector Sharing Resolution'. In case of conflict, using miss distance vector in PCA, we can decide the directions for two VAVs to share the conflict region. With these directions, VAVs are going to maneuver cooperatively. First of all, this paper describes some '2-D' conflict scenarios and then extends to '3-D' conflict scenarios.
Minimum-Time Guidance and Control Law for High Maneuvering Missile
Yamaoka, Seiji ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 46~58
DOI : 10.5139/IJASS.2009.10.1.046
This paper deals with design procedure of online guidance and control law for future missiles that requires agile maneuverability. For the purpose, the missile with high powered side thruster is proposed. The guidance and control law for such missiles is discussed from a point of view of optimal control theory in this paper. Minimum time problem is solved for the approximated system. It is derived that bang- bang control is optimal input from the necessary conditions of optimal solution. Feedback guidance without iterative calculation is useful for actual systems. In this paper. multiple design point method is applied to design feedback gains and feed forward inputs of the guidance and control law. The numerical results show that the proposed guidance and control law has a high -performance for wide-ranging boundary conditions.
Design of Optimal Controllers for Spacecraft Formation Flying Based on the Decentralized Approach
Bae, Jong-Hee ; Kim, You-Dan ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 58~66
DOI : 10.5139/IJASS.2009.10.1.058
Formation controller for multiple spacecrafts is designed based on a decentralized approach. The objective of the proposed controller is to make each spacecraft fly to the desired waypoints, while keeping the formation shape of multiple spacecrafts. To design the decentralized formation controller, the output feedback linearization technique using error functions for goal convergence and formation keeping is utilized for spacecraft dynamics. The primary contribution of this paper is to proposed optimal controller for formation flying based on the decentralized approach. To design the optimal controller, eigenvalue assignment technique is used. To verify the effectiveness of the proposed controller, numerical simulations are performed for three-dimensional waypoint-passing missions of multiple spacecrafts.
Optimal Perilune Altitude of Lunar Landing Trajectory
Cho, Dong-Hyun ; Jeong, Bo-Young ; Lee, Dong-Hun ; Bang, Hyo-Choong ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 67~74
DOI : 10.5139/IJASS.2009.10.1.067
In general, the lunar landing stage can be divided into two distinct phases: de-orbit and descent, and the descent phase usually comprises two sub-phases: braking and approach. And many optimization problems of minimal energy are usually focused on descent phases. In these approaches, the energy of de-orbit burning is not considered. Therefore, a possible low perilune altitude can be chosen to save fuel for the descent phase. Perilune altitude is typically specified between 10 and 15km because of the mountainous lunar terrain and possible guidance errors. However, it requires more de-orbit burning energy for the lower perilune altitude. Therefore, in this paper, the perilune altitude of the intermediate orbit is also considered with optimal thrust programming for minimal energy. Furthermore, the perilune altitude and optimal thrust programming can be expressed by a function of the radius of a parking orbit by using continuation method and co-state estimator.
Enhanced SBAS Integration Method Using Combination of Multiple SBAS Corrections
Yun, Ho ; Kim, Do-Yoon ; Jeon, Sang-Hoon ; Park, Bynng-Woon ; Kee, Chang-Don ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 75~82
DOI : 10.5139/IJASS.2009.10.1.075
In this parer, we propose a new way of improving DGNSS service using combination of multiple SBAS information. Because SBAS uses Geostationary Earth Orbit (GEO) satellites, it has very large coverage but it can be unavailable in urban canyon because of visibility problem. R. Chen solved this problem by creating Virtual Reference Stations (VRS) using the SBAS signal . VRS converts SBAS signal to RTCM signals corresponding its location, and broadcast the converted RTCM signals over the wireless internet. This method can solve the visibility problem cost effectively. Furthermore it can solve DGNSS coverage problem by creating just a transmitter instead of a reference station. Developing above method, this paper proposes the methods that integrate two or more SEAS signals into one RTCM signal and broadcast it. In Korea, MSAS signal is available even though it is not officially certified for Korean users. As a Korean own SBAS-like system, there is the internet-based KWTB (Korean WADGPS Test Bed) which we developed and released at ION GNSS 2006. As a result, virtually two different SBAS corrections are available in Korea. In this paper, we propose the integration methods for these two independent SBAS corrections and present the test results using the actual measurements from the two systems. We present the detailed algorithm for these two methods and analyze the features and performances of them. To verify the proposed methods, we conduct the experiment using the logged SBAS corrections from the two systems and the RINEX data logged at Dokdo monitoring station in Korea. The preliminary test results showed the improved performance compared to the results from two independent systems, which shows the potential of our proposed methods. In the future, the newly developed SBASs will be available and the places which can access the multiple SBAS signals will increase. At that time, the integration or combination methods of two or more SBASs will become more important. Our proposed methods can be one of the useful solutions for that. As an additional research, we need to extend this research to the system level integration such as the concept of the decentralized W ADGPS.
IRF Analysis Considering Clutter Background for SAR Image Qualification
Jung, Chul-H. ; Oh, Tae-B. ; Song, Sun-H. ; Kwag, Young-K. ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 83~90
DOI : 10.5139/IJASS.2009.10.1.083
A new IRF (Impulse Response Function) analysis technique in high resolution SAR image is presented by taking into account the real clutter environment. In order to investigate the realistic effect of clutter background on the impulse response function of SAR image, an ideally generated impulse response function is superimposed with a large number of background clutter data which are extracted from the various regions of an actual SAR image. As a performance measure, PSLR (Peak Sidelobe Ratio) of the clutter-contained IRF is presented in the various groups of clutter background, and finally the results are compared with the stochastic model.
Alternative Energy - Environment Safety
Kurnaz, Sefer ; Rustamov, Rustam B. ; Zeynalov, Ismayil ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 91~97
DOI : 10.5139/IJASS.2009.10.1.091
It is undertaken systematization of results of satellite and ground observation parameters characterizing a current condition and climatic variability of two selected geographical areas. One of them covers territory of Azerbaijan and another covers a wide area of Caspian See region. Average values and mean square deviations of following values are investigated: outgoing long wave radiation during a day and night (in nebulosity and cloudless). absorbed within a day of the stream of a sunlight of the system in "a terrestrial surface-atmosphere". degree of a covering by clouds of the selected areas during a day and at night, ground temperature values of air. pressure and speed of a wind. Monthly average values of corresponding parameters create a basis of suggested investigations. It has been presented features of a time course of investigated parameters for each month and year in the whole due to the continuously observations since 1982-2000. The scientific problem consists that there are no existed models which authentically would be cover the main aspects of a realities specified changes: they are identified by economic activities. growth of the population and other features of development of a human society or internal fluctuations of biogeophysical/climatic system. Possibilities of predictability of biosphere and climate changes depend on available timely supervision. adequacy of construction of appropriate models. understanding of mechanisms of direct and feedback influences in such complicated systems.
Monitoring of The Impacts of the Natural Disaster Based on The Use of Space Technology
Kurnaz, Sefer ; Rustamov, Rustam B. ; Zeynalova, Maral ; Salahova, Saida E. ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 98~103
DOI : 10.5139/IJASS.2009.10.1.098
The forecasting, mitigation and preparedness of the natural disaster impacts require relevant information regarding the disaster desirable in real time. In the meantime it is requiring the rapid and continuous data and information generation or gathering for possible prediction and monitoring of the natural disaster. Since disasters that cause huge social and economic disruptions normally affect large areas or territories and are linked to global change. The use of traditional and conventional methods for management of the natural disaster impact can not be effectively implemented for intial data col1ection with the further processing. The space technology or remote sensing tools offer excellent possibilities of collecting vital data. The main reason is capability of this technology of collecting data at global and regional scales rapidly and repetitively. This is unchallenged advantage of the space methods and technology. The satellite or remote sensing techniques can be used to monitor the current situation, the situation before based on the data in sight. as well as after disaster occurred. They can be used to provide baseline data against which future changes can be compared while the GIS techniques provide a suitable framework for integrating and analyzing the many types of data sources required for disaster monitoring. Developed GIS is an excellent instrument for definition of the social impact status of the natural disaster which can be undertaken in the future database developments. This methodology is a good source for analysis and dynamic change studies of the natural disaster impacts.
Numerical Simulation of Unsteady Rotor Flow Using an Unstructured Overset Mesh Flow Solver
Jung, Mun-Seung ; Kwon, Oh-Joon ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 104~111
DOI : 10.5139/IJASS.2009.10.1.104
An unstructured overset mesh method has been developed for the simulation of unsteady flow fields around isolated rotors and rotor-fuselage configurations. The flow solver was parallelized for the efficient calculation of complicated flows requiring a large number of cells. A quasi-unsteady mesh adaptation technique was adopted to enhance the spatial accuracy of the solution and to better resolve the rotor wake. The method has been applied to calculate the flow fields around rotor-alone and rotor-fuselage configurations in forward flight. Validations were made by comparing the predicted results with those of measurements. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.
Trajectory Optimization for a Supersonic Air-Breathing Missile System Using Pseudo-Spectral Method
Park, Jung-Woo ; Tahk, Min-Jea ; Sung, Hong-Gye ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 1, 2009, Pages 112~121
DOI : 10.5139/IJASS.2009.10.1.112
This paper deals with supersonic air-breathing missile system. A supersonic air-breathing missile system has very complicated and incoherent thrust characteristics with respect to outer and inner environment during operation. For this reason, the missile system has many maneuver constraints and is allowed to operate within narrow flight envelope. In this paper, trajectory optimization of the missile is accomplished. The trajectory optimization problem is formulated as a discrete parameter optimization problem. For this formulation, Legendre Pseudo-Spectral method is introduced. This method is based on calculating the state and control variables on Legendre-Gauss-Lobatto (LGL) points. This approach helps to find approximated derivative and integration quantities simply. It is shown that, for this trajectory optimization, trend analysis is performed from thrust characteristics on various conditions so that the trajectory optimization is accomplished with fine initial guess with these results.