Defence Science Journal
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Wind Profile Estimation during Flight Path Reconstruction
Get PDFAccuracy of flow angles measurements becomes crucial as the aircraft approaches higher angle of attack. Flight path reconstruction (FPR) is an excellent tool for air data calibration. An important element of air data calibration is the estimation of wind velocities. The objective of this paper is to evaluate different approaches of wind estimation within the framework of FPR. Flight test data of a high performance aircraft is subjected to FPR and the estimated wind velocities and flow angle trajectories are presented and discussed to demonstrate the impact of wind estimation on aircraft flow angles. Results clearly show that accuracy of reconstructed flow angles improves when time varying wind models are used. The proposed analytical wind model is found to be as effective as augmented parameters in Extended Kalman filter and computationally less intensive
Investigation of kerf Characteristics in Abrasive Water Jet Machining of Inconel 600 using Response Surface Methodology
Get PDFAbrasive water jet machining (AWJM) has found its application in the manufacturing industries for machining hard materials with precision. A degree of high precision in machining of complex geometries makes AWJM valuable. The selection of optimum process parameters is important to the resulting quality of machined parts. In this study, an experimental investigation was conducted to evaluate the machinability of Inconel 600. A response surface methodology (RSM) is used to determine the influence of the AWJM process parameters on the considered performance characteristics, i.e., kerf top width (KTW) and taper angle. The analysis of variance is performed to obtain the contribution and influence of each process parameter on the considered responses. The value of R-Squared obtained for KTW and taper angle using regression model is 0.97 and 0.96 respectively. The optimum setting of the parameters for single and multiple response characteristics are obtained using the desirability analysis of RSM. The results obtained using desirability analysis of RSM is validated by conducting the confirmation experiments. The experimental confirmatory values obtained for the considered performance parameters KTW and taper angle as 27.138 and 0.125 respectively. The corresponding value of error obtained as 0.383 and 0.013 respectively. Further, an optimum set is obtained with KTW as 27.461 mm and taper angle as 0.582° for multiple response optimisation
Estimation of Compressional Wave Speed in Marine Sediments using Biot Stoll Model and Buckinghams Grain shearing Model
Get PDFAcoustic properties of seafloor sediments can be estimated using theoretical models by giving geophysical properties of sediments as inputs to the respective models. Empirical relations connecting the geophysical and geoacoustic properties are available in literature. In this study an experimental assessment of two such theoretical models viz., Biot-Stoll model (BSM), a poro-elastic model and the Buckingham’s grain shearing (GS) model, a visco-elastic model is done by estimating the compressional wave speed. Compressional wave speed is measured using in-house developed sediment velocimeter and is compared with the speed estimated using both the models and a regression analysis was done. It was observed that the Coefficient of determination R2 for BSM and GS model are 0.769 and 0.729, respectively. It shows that once the constants used in GS model are evaluated for the Indian waters, then it can be used to estimate the acoustic properties of sediments
Effects of Projectile and Gun Parameters on the Dispersion
Get PDF Main battle tanks constitute one of the most powerful fire powers for the armoured land forces. To use this very high fire power efficiently, the dispersion of shot impacts becomes crucial. Dispersion is affected by the aerodynamic factors, gun-projectile interactions, projectile and gun dependent factors, manufacturing tolerances and environmental factors. The change in aerodynamic factors and environmental conditions varies the aerodynamic forces applied on the projectile and this affects the dispersion characteristics of the projectile. In this study, the effects of the changes in recoil stiffness, gun support stiffness, projectile muzzle velocity and manufacturing tolerances of projectile forward/rear bourrelet diameters on the dispersion for 120 mm L44 and L55 calibre guns are investigated. Armour piercing fin stabilised discarding sabot type projectile is used in the analysis. Statistical dispersion analyses including interior ballistic, in-bore balloting and exterior ballistic analyses are conducted using PRODAS ballistic software. According to the results, it is determined that the decrease in projectile/bore clearance (forward/rear bourrelet diameter) results in improved dispersion of ammunition. The 10% changes from the nominal recoil stiffness and the vertical support stiffness values have negligible effects on the dispersion. In addition, the results show that muzzle velocity variations influence the dispersion in vertical direction substantially. Using the procedure applied in this study, it is shown that different clearance conditions can be analysed and most suitable tolerances may be determined taking into consideration of both the gun system performance and manufacturability
High Accuracy Parameter Estimation for Advanced Radar Identification of Electronic Intelligence System
Get PDFRadar identification is one of the vital operations in an electronic intelligence system. The conventional methods based on basic parameters comparison of unique identification of a radar in a cluster of similar radars, is prone to ambiguities. To meet the current tactical requirements of unique identification of a radar, the methodology needs to be based on better feature extraction, even in low SNR conditions. The paper explores a novel technique based on moving autocorrelation for the extraction of intra-pulse and inter-pulse radar parameters. Extensive simulation and empirical studies have been carried out to establish the approach to extend accurate radar parameters in noisy and low SNR conditions. The technique is found to be promising even in field data conditions. The paper describes the methodology, simulation results, FPGA implementation using system generator and resource utilisation summary
Narcotic Drug Detection and Identification through Synchronous Fluorescence Technique
Get PDFIllegal production of potentially hazardous narcotics as well as various psychotropic drugs is being carried out in the neighbouring countries and international market which is causing narco-terrorism a global havoc. Compared with traditional/natural drugs the synthetic drugs are more smuggled nowadays. Because of the vulnerability of the borders to drug trafficking, India has increased surveillance at borders and coasts and thus has tackled the problem to some extent. Authors developing a Narcotic drug sensor (point sensor) for detection and identification of Narcotic drugs based on Laser Induced Fluorescence more specifically Synchronous Fluorescence Spectroscopy in an effort. Some narcotic samples viz. Caffeine, Quinine and Tramadol were considered for the study. The fluorescence spectrum was studied using our own laboratory-based sensor incorporating charge coupled device-based Spectrometer and Laser source (266 nm wavelength) and commercial system from ‘Horiba Scientific’ incorporating Photomultiplier tube and Xe lamp source
Operational Feasibility Study of High Altitude Balloon Platform based on the Wind Environment in South Korea
Get PDFNaval helicopters flying at extremely low altitudes often face communication problems when the helicopter is located in the distance from the mother ship. Accordingly, new attention is being cast on the high altitude balloon (HAB) to solve this problem due to its cost-effectiveness and ability of rapid deployment to the battlefield. The balloon is one of a lighter-than-air vehicle that the blowing wind determines its speed, direction, and travel distance. Therefore, it is likely that seasonal changes in wind conditions will restrict the operation of the balloon. In this paper, the feasibility study of the balloon, which is regarded as a future communication relay platform, on the theater of operation of the Republic of Korea Navy the First Fleet was performed. The trends of the balloon trajectory for five years (2014 ~ 2018) with respect to seasonal wind variations were investigated employing the numerical trajectory prediction program. Simulated balloon trajectories of summer and winter showed considerable differences due to seasonal wind. Summer season was found that it has the most favorite flight environment for the balloon campaign. Upon reflecting on the simulation results, the HAB operating procedure, which capitalised on the Ulleungdo, was also suggested
Synthesis and Thermal Decomposition Kinetics of Epoxy Poly Glycidyl Nitrate as an Energetic Binder
Get PDFAn energetic binder epoxy poly glycidyl nitrate (e-PGN) with a molecular weight of about 1244 gr/mol was synthesised via end modified poly glycidyl nitrate (PGN) is presented in the paper. This structure was characterised by the number of epoxy groups, infrared spectroscopy, and nuclear magnetic resonance. The thermal degradation behavior of e-PGN was studied by thermo gravimetric analysis (TG) and differential scanning calorimetry (DSC) under nitrogen atmosphere at different heating rates. The glass transition temperature (Tg) was measured to determine the compatibility of energetic plasticizer with the binder in the mixture of plasticizer/binder and compared with the results of e-PGN, and initial decomposition temperature in e-PGN was studied using the DSC method. The DSC results showed that the glass transition temperature of a mixture of 20 % Bu-NENA/e-PGN mixture (Tg = −56 °C) was lower than e-PGN (Tg = −37.78 °C) that shows the most compatible plasticizer is Bu-NENA. The activation energy of degradation e-PGN and e-PGN-20% Bu-NENA were calculated with DSC by the model-free methods and compared with the results of AKTS software in version 3.51(2013-07-10). The activation energy of exothermic decomposition of the e-PGN and e-PGN-20% Bu-NENA were calculated by the Kissinger, Flynn–Wall–Ozawa, Starink, and AAdvanced kinetics and technology solutions (Friedman) methods. Finally, the half-life prediction of the e-PGN and e-PGN-20% Bu-NENA were investigated
Forebody Wake Effects on Parachute Performance for Re entry Space Application
Get PDFForebody generates its own wake that influences the performance of aerodynamic decelerators during the flights. Many parachute Jumpers have experienced the failure of an ejected pilot chute as the parachute canopy collapsed and fell back on the Jumper because of wake developed behind the Jumper. In the available literature, limited data is available to predict the exact loss of parachute drag in presence of the forebody (FB). The purpose of this paper is to generate a comprehensive aerodynamic data to study the behaviour of FB-parachute dynamics by conducting the wind tunnel experiments. Wind tunnel test has been carried out to establish the initial design parameters of aerodynamic parachute. The experiment was carried out on a scale down model of 20 degree conical ribbon drogue parachute and FB with and without each of them at a subsonic speed for studying dynamic stability characteristic for different orientation of FB. The test results indicate that to ensure adequate stability for the capsule to descend vertically at a low subsonic speed, a cluster of two drogue parachutes be used. Under such condition, the overall drag coefficient found to be above 0.50 providing not only a safe descends velocity but increasing reliability of mission as well
Thermo mechanical and Control Behaviour of Copper based Shape Memory Alloy Bimorph Actuator towards the Development of Micro Positioning System
Get PDFA shape memory alloy (SMA) bimorph actuator is a composite structure composed of flexible polyimide substrate and SMA thin film deposited using thermal evaporation technique. In this work, the substrate thickness in the range of 25 - 75 mm was selected for the development of CuAlNiMn SMA bimorph actuator. An investigation on the control behavior of copper based SMA bimorph towards the development of micro positioning system has been performed. The actuation behavior of the SMA bimorph was studied using electrical actuation. Subsequently, a proportional integral derivative (PID) controller was designed to control the bimorph actuator with proper tuning of gain parameters. The displacement of the bimorph actuator was controlled through dedicated experimental setup consisted of laser displacement sensor, data acquisition system and LabVIEW software. The CuAlNiMn SMA bimorph actuator resulted in a satisfying control performance which can be extended to MEMS applications. A preliminary prototype of the SMA bimorph actuator based micro positioning system has been developed