Defence Science Journal
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Experimental Performance Evaluation of Small Solid Rocket Motor with Composite Case for Environmental Conditions
Get PDFPolymeric composites are widely used in aerospace. One such important use of polymeric composites is the filament-wound composite case for the Solid Rocket Motor (SRM). Environmental conditions expected during flight and other phases of the SRM’s life cycle affect its performance. The performance of SRM, in turn, depends primarily on the composite case and propellant grain. In this study, the performance evaluation of SRM with the composite case is carried out for different environmental conditions. These cases are designed to sustain very high pressure and temperature environments generated due to the combustion of propellant grains and are intended to perform adequately at any time during their service life. The performance evaluation test matrix is formulated considering various expected dynamic and thermal conditions. The small SRM with a composite case is subjected to planned tests as per the matrix, followed by static tests. The pressure versus time data is plotted for all test conditions. The ballistic parameters result of the virgin (without subjecting it to any test) small SRM is considered as a reference for comparative studies with the rest of all other test conditions results. All the ballistic performance test results are also analysed with respect to the pressure-time curve for mission bounds. The analysis of experimental test results reveals that various environmental dynamic conditions like random vibration, acceleration and shock, do not affect the composite case and the ballistic performance of a small SRM. The effect of grain temperature on ballistic performance is also found as expected
Aircraft Parameter Estimation using Feedforward Neural Networks With Lyapunov Stability Analysis
Get PDFAerodynamic parameter estimation is critical in the aviation sector, especially in design and development programs of defense-military aircraft. In this paper, new results of the application of Artificial Neural Networks (ANN) to the field of aircraft parameter estimation are presented. The performances of Feedforward Neural Network (FFNN) with Backpropagation and FFNN with Backpropagation using Recursive Least Square (RLS) are investigated for aerodynamic parameter estimation. The methods are validated on flight data simulated using MATLAB implementations. The normalized Lyapunov energy functional has been used to derive the convergence conditions for both the ANN-based estimation algorithms. The estimation results are compared on the basis of performance metrics and computation time. The performance of FFNN-RLS has been observed to be approximately 10% better than FFNN-BPN. Simulation results from both algorithms have been found to be highly satisfactory and pave the way for further applications to real flight test data
Comparative Studies of Photochemical and Electrochemical Methods on Mineralization of Picric Acid
Get PDFThe effluents generated from synthesis and processing plant of Picric acid is reported to be carcinogenic and hence needs to be treated to reduce its concentration below safe discharge limit. Present paper deals with studies on mineralization of Picric acid by adopting photochemical and electrochemical processes and the efficacy of the both processes have been explored in details. Crucial process parameters viz. pH, concentration of oxidizer and catalyst for mineralization of Picric acid are optimized. In photochemical method, It is observed that Picric acid is treated to bring down its concentration from 100 ppm to ≤ 1 ppm under Photo-Fenton process in 2 hrs whereas same treatment carried out under Photo- catalytic process takes only 1 hr. It is also observed that TiO2 xerogel and beads of nano-TiO2 are more efficient compared to that of commercially available TiO2. The TiO2–Polysulfone (PS) beads show less efficiency than TiO2 xerogel. However, the Picric acid oxidation efficiency for TiO2–PS beads is comparable and advantage of TiO2–PS beads is that it can easily be recovered from the treated solution and can be reused in the next experiments. Electrochemical process is user’s friendly and economical. In case of electrochemical treatments at optimized process parameters under Electro-Fenton reaction picric acid is completely mineralized below its drain discharge limit where as under Electro-peroxide reaction picric acid is mineralized upto 3 ppm within 3 hrs. The treated solution has been characterized by using UV-Visible spectrophotometer, High performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC) Analyzer. The observed results have been interpreted and reported in the present paper
IRNSS Performance Evaluation of SPS Services on Military Aircraft
Get PDFThe essence of this paper is to study and characterise the performance of Indian Regional Navigation Satellite System (IRNSS), also known as NavIC (Navigation with Indian Constellation), in actual dynamic environment by conducting field trials on military aircraft. The dynamic accuracy of IRNSS receiver in terms of position, velocity and altitude has not yet been tested on any aircraft system i.e. commercial or military applications. These field trials and performance evaluation will help in on-field assessment of IRNSS receiver performance with availability of five, six and seven IRNSS satellites. During conduct of trials, IRNSS receiver and IRNSS antenna were placed inside the aircraft. Results analysis of 18 hours flying data depicts position availability of 99.872% with five satellites and 100% position availability with six and seven satellites
Modelling and Optimisation of UHF band EW Based WTA Problem within the Scope of Threat Assessment
Get PDFThe classical weapon target allocation (WTA) problem has been evaluated within the scope of electronic warfare (EW) threat assessment with an electromagnetic effect-based jammer- tactical radio engagement approach. As different from the literature, optimum allocation of non-directional jammers operating at different operating UHF frequencies under constraints to RF emitters is aimed in this study. The values of the targets are modelled using an original threat assessment algorithm developed that takes into account operating frequencies, jamming distance, and weather conditions. The computed jammer-target effect matrix has been solved under different scenarios according to the efficiency and cost constraints. It is seen at the end of the simulations that the allocation results for EW applications largely depend on the effect ratio used. The better results are taken in the case of under 0.5 effect ratio. Finally, jammer-radio allocation problem specified at the suggested model is solved successfully and effectively
Comparative Study of Structural and Mechanical Properties of as Deposited and Shock Wave Exposed NiW Nano Structured Thin Films
No full textThe current work describes the effect of shock wave exposure on electroplated NiW thin films. NiW thin films were deposited through electrodeposition process by varying the bath temperatures (35°C and 70°C) at constant current density of 1A/dm2. The deposited NiW thin films were exposed to shock waves with varying Mach numbers of 1.13 and 2.33 using an in-house shock wave tube facility. The as-deposited and shock wave-exposed NiW thin films were characterized by XRD, FESEM, EDS, and EIS to reveal its structural and mechanical properties. The XRD results disclose the stable cubic structural phase of as deposited and shock wave exposed NiW thin films with average crystallite size varying between 5 nm to 17nm. The elemental composition of as-deposited and shock-wave exposed films are similar as confirmed in the EDS analysis. This henceforth represents the stability of nanostructured NiW film in terms of compositional and structural aspect. Morphological analysis through FESEM shows that the exposed thin film is defect free due to the impact of shock waves. Furthermore, corrosion resistance is observed to enhance ten times in shock-wave exposed thin film than as-deposited thin film for higher mach number (Pressure ~63 bar). Similarly, corrosion resistance for low mach number (pressure ~13 bar) increases by three times of as deposited film according to the EIS analysis. Therefore, the structural, morphological and corrosion properties were enhanced upon surface treatment by shock wave exposure. NiW thin films with enhanced mechanical properties such as low corrosion rate, high corrosion resistance is used in various industrial applications like defense applications, aircraft, and marine applications
A Novel Design Approach for Low Speed Recovery of High Performance Fighter Aircraft
Get PDFIn this paper, a novel design approach for low-speed recovery of a high-performance fighter aircraft is presented. It is shown that the phugoid mode has an important bearing on the problem of low-speed departure. Based on the analysis of the phugoid mode trajectories, a novel low-speed protection algorithm is presented in this paper. The proposed low speed recovery is achieved in three phases. The first phase consists of detecting the incipient departure followed in the second phase by the application of suitable recovery controls and finally the third phase ends with the transfer of controls to the pilot. The design of the first and the third phase consist of choosing the correct trigger conditions which ensures safe recovery of the aircraft in all conditions. The proposed Automatic low speed recovery is triggered when the aircraft trajectory crosses a fixed boundary in the region spanned by the dynamic pressure and its rate of decrease. It is observed that this boundary is approximately a straight line, implying that it is equivalent to a forward prediction in time to indicate when the aircraft will reach the lowest controllable airspeed. This Automatic Low Speed Recovery with Forward Prediction (ALSR-FP) algorithm is found to be simpler than other existing design methods and effective in preventing low speed departure for a variety of pilot inputs that result in the aircraft losing airspeed leading to stall. In the second phase control inputs are chosen to align the velocity vector to the direction of local gravity. The recovery phase is considered complete after the aircraft reaches the dynamic pressure which is approximately 10 % higher than the minimum dynamic pressure for control. Performance of the ALSR-FP is demonstrated using the high-performance fighter aircraft ADMIRE model which has a delta wing configuration, canards and multiple redundant controls. It is also shown that the proposed algorithm can be easily implemented on board for any other fighter and civil aircraft
Design and Development of High Voltage High Pulse Power Supply using FPGA for Dynamic Impedance Matching
Get PDFHigh Voltage High Pulse Power Supply (HVHPPS) is designed with the goal to match fixed load, so thatprecise pulse output can be achieved. Generally the loads involve magnetron, klystron, and particle accelerators etc. The HVHPPS output pulse shape changes with load impedance variation due to various reasons. Due to changes in impedance, the performance of Pulse Power Supply degrades and reflects the power at the source end which causes component failure and system shut down. To overcome such problems, a scale down High Voltage High Pulse Power is designed and developed to match the dynamic impedance variations upto 25 % of mismatch. In earlier days, all HVHPPS were designed using microcontrollers where the problem of pulse to pulse monitoring and computational speed was compromised. The availability of variable and self-defined, Field Programmable Gate Array (FPGA) controller, which provided flexibility to design the pulse to pulse shaping and various vital parameter monitoring, made it possible. This paper presents the design and implementation of HVHPPS over an FPGA platform to meet the fast response requirement. This paper provides a solution for impedance mismatch problems associated with such types of power supply, and also presents specifications for major components in a high voltage pulse power system for various types of load ranges. An experimental test hardware was designed and developed for HVHPPS to implement dynamic impedance algorithm and validate the results
Novel Statistical Techniques for Conducting Accelerated Life Test to Demonstrate Product Reliability
Get PDFIn Reliability Demonstration Testing (RDT), finding the right sample size is very important since the cost of the prototypes is high and difficult to make. If the sample size for the RDT is test is less, the amount of information obtained from the test will be insufficient, and the conclusion will be meaningless; on contrary, if the sample size is big/huge, the amount of information obtained from the test will be in excess of what is required, resulting in unnecessary costs. Most of the time, the required sample size and test time are decided based on the RDT test design. Resources required for RDT in terms of batch size and long testing-time is practically not feasible, due to limitation of the project schedule and budget. The reliability engineers must have a sound knowledge of type challenge/risk that is allowed for conducting RDT. The research paper with a case study provides the required information about the modern techniques adopted in reducing the sample-size and testing time with the help of accelerated test models such as Arrhenius, Erying etc., for conducting accelerated life test to demonstrate the product reliability
Terrain Specific Real Time Pixelated Camouflage Texture Generation & its Impact Assessment
Get PDF“Camouflage” is a natural or nature identical phenomenon where the sensory route of vision is delayed toavoid visual detection. Reducing detection capability and hiding in the background environment is critical for Army vehicles, equipment, and soldiers. This research aims to implement a process that will generate digital camouflage patterns specific to the terrain. The adapted digital pattern helps an object blend symmetrically into the background environment. Pixelated textures combine macro and micro designs that blend with ambient shrubs, trees, branches, and shadows. The technique presented in this paper consists of the following main modules: terrain classification model, pixelated camouflage texture generation, and texture evaluation. Experiments have been conducted to detect camouflage objects in the scene to evaluate the performance of the resultant camouflage texture generated for a natural environment. Photo simulation and saliency maps for hidden object detection have been used to evaluate the effectiveness of generated textures for a given terrai