Showing papers by "Defence Research and Development Laboratory published in 2016"

Modeling and Optimization of Machining Nimonic C-263 Superalloy using Multicut Strategy in WEDM

Abstract: In recent years, wire-electrical discharge machining (WEDM) has gained popularity in the industry due to its capability to generate complicated shapes in exotic materials, irrespective of their hardness. Conventional machining of Nimonic C-263 superalloy is an extremely difficult and costly process due to its high hardness and tool wear rate. The present research work investigates the influence of the WEDM process parameters on different performance measures during machining of Nimonic C-263 superalloy. A mathematical model for all four important performance measures, namely, cutting rate, surface roughness, spark gap, and wire wear ratio, was developed and the responses were used for studying the interrelationship between performance measures and process parameters. The optimal settings of operating conditions were predicted using desirability function. The effectiveness of multicut strategy was also investigated in the article.

Dissimilar Friction Stir Welds in AA2219-AA5083 Aluminium Alloys: Effect of Process Parameters on Material Inter-Mixing, Defect Formation, and Mechanical Properties

Abstract: Dissimilar friction stir welds of aluminium alloys AA5083 and AA2219 were investigated in a view to get defect free welds by varying process parameters. An attempt has been made to develop a mathematical model to predict sound welds. Design of experiments with three parameters and five levels were used to optimize the effectiveness of process parameters. Analysis of variance and response surface methodology were used to determine the significance and optimal level for each parameter to minimize % area of volumetric defect. The experimental and predicted values of % area of volumetric defect were in good agreement. The effects of process parameters and tool-offset on the extent of intermixing of materials and to minimize % area of volumetric defects were analyzed in detail by employing different methods such as macrostructural analysis and electron probe micro analysis. The defect free dissimilar weldments were characterized for transverse tensile properties. The observed tensile strength values were correlated with reference to the extent of intermixing of materials in the stir/nugget zone. Established mathematical models have depicted a good prediction of relationship between the investigated FSW process parameters and the % area of defect of the welds. It is understood that the mixing pattern in nugget zone and further joint strength are primarily affected by the tool offset and welding parameters.

Enhancement of strain tolerance of functionally graded LaTi2Al9O19 thermal barrier coating through ultra-short pulse based laser texturing

Abstract: Functionally Graded Thermal barrier coating (FG-TBC) based on LaTi2Al9O19 was prepared via air plasma spray and textured using pico-second Nd:YAG laser (wavelength 532 nm, 3 W) over the coating surface to resist the delamination or failure stresses caused by thermal mismatch when exposed to high temperature. Different laser scan speeds, depth and width were set on each sample and the surface structure was investigated by thermal shock test. The microstructure and surface morphology were analyzed by SEM and 3D Profilometer. In the case of the laser-textured TBC, the re-melted coating layer was completely absent. It was found that the laser textured grooves with 375 μm spacing enhances the strain tolerance of TBC and provides excellent thermal durability and lifetime of more than 186 cycles. When top layer experience expansion and contraction under high temperature exposure, the grooves in the top layer of FG-TBC provide additional stress/strain relief gap and prevents the coating from failure.

Conducting polymer coated graphene oxide reinforced C–epoxy composites for enhanced electrical conduction

Abstract: Enhanced electrical conductivities were achieved in C–epoxy composites by integrating them with conducting polymers (CPs), namely poly pyrrole (PPY), poly(3,4-ethylene dioxythiophene) (PEDOT) and graphene oxide (GO) enwrapped by CPs. By in-situ polymerization of pyrrole or 3,4-ethylenedioxythiophene (EDOT) in the presence of the GO (template), sodium bis(2-ethylhexyl) sulfosuccinate (structure directing agent), ferric chloride (oxidant), the electrically conductive sheets of GO enwrapped CPs were obtained. The formation of CP coating on GO was confirmed by Raman spectroscopy, scanning electron microscopy and thermo gravimetric analysis studies. Different wt% of CP and CP coated GO were added to the epoxy resin and this resin was used to prepare the 2D laminated C–epoxy composites by hand layup method. DC electrical conductivity of the prepared C–epoxy composites were analyzed using current–voltage (I–V) characteristics and impedance measurements. Typical results showed that CP coated GO, at 0.5 wt% addition to epoxy imparted highest DC electrical conductivity for C–epoxy composite.

A robust and high precision optimal explicit guidance scheme for solid motor propelled launch vehicles with thrust and drag uncertainty

Abstract: A new nonlinear optimal and explicit guidance law is presented in this paper for launch vehicles propelled by solid motors. It can ensure very high terminal precision despite not having the exact knowledge of the thrust–time curve apriori. This was motivated from using it for a carrier launch vehicle in a hypersonic mission, which demands an extremely narrow terminal accuracy window for the launch vehicle for successful initiation of operation of the hypersonic vehicle. The proposed explicit guidance scheme, which computes the optimal guidance command online, ensures the required stringent final conditions with high precision at the injection point. A key feature of the proposed guidance law is an innovative extension of the recently developed model predictive static programming guidance with flexible final time. A penalty function approach is also followed to meet the input and output inequality constraints throughout the vehicle trajectory. In this paper, the guidance law has been successfully validated from nonlinear six degree-of-freedom simulation studies by designing an inner-loop autopilot as well, which enhances confidence of its usefulness significantly. In addition to excellent nominal results, the proposed guidance has been found to have good robustness for perturbed cases as well.

High-temperature stability of yttria-stabilized zirconia thermal barrier coating on niobium alloy—C-103

Abstract: Thermal barrier coatings (TBCs) of yttria-stabilized zirconia (YSZ) of different thicknesses with an intermediate bond coat were deposited on C-103 Nb alloy using the air plasma spraying technique. The coatings were subjected to rapid infra-red (IR) heating (∼25°C s−1) up to ∼1250°C and exposed up to 100 s at this temperature with heat flux varying from 55 to 61 W cm−2. The TBCs were found to be stable and intact after the heat treatment. In contrast, at the same conditions, the uncoated C-103 alloy specimen showed extensive oxidation followed by weight loss due to spallation. A maximum temperature drop of ∼200°C was observed on the opposite side of the coated alloy with 600 μm YSZ coat; as against negligible temperature drop in case of bare alloy specimen. The temperature drop was found to increase with the coating thickness of YSZ. The coatings before and after IR heating were investigated by scanning electron microscopy, X-ray diffraction, electron probe microanalysis, microhardness and residual stress measurements in order to understand the effect of thermal shock on the properties of the TBC. On account of these high-temperature properties, YSZ coating along with the bond coat is expected to find potential thermal barrier coating system on niobium alloys for supersonic vehicles.

Magnetohydrodynamic Flow Control of a Hypersonic Cruise Vehicle Based on AJAX Concept

Abstract: I N THE history of space exploration, rockets were the only flight vehicles available for transportation such as Earth orbital missions for placing satellites, interplanetary flights, and military missions such as Intermediate Range Ballistic Missiless and Intercontinental Ballistic Missile. Most of these rockets flew a oneway mission of transportation from Earth to the destination and, upon completion of the mission, were either lost in space or fell back to Earth as debris, and hence were nonrecoverable. The cost associated with launching these flight vehicles and the imposing technological challenges, though considered as highly mature as of the present day, were overwhelmingly large. The U.S. Space Shuttle of and the Russian Buran/Energiya were designed and operated as the only reusable flyingmissions that couldmake several sorties between the Earth and the flight to orbit [1]. However, huge operating andmaintenance costs associated with each of these missions, and the inexorable reliability and safety issues, gradually shelved them as unacceptable due to the present-day design philosophy of “low-cost access to space.”Hence, next-generation space exploration required a different class of flight vehicles that was required to be cost efficient and fully reusable. In this realm, the hypersonic airbreathing propulsion system based on a supersonic combustion ramjet (SCRAMJET) was envisaged as the key technology platform for possible realization of the reusable launch vehicle (RLV) in full mission mode, which could perform orbital flights similar to that of spacecraft flown by a rocket system, although with logistics akin to that of an airliner, as on a day-to-day basis [2]. Active flow control of hypersonic flight vehicles forms a crucial design requirement for hypersonic research and technology development. The futuristic RLV concepts, such as the hypersonic cruise vehicle (HSCV) based on the SCRAMJET engine, require complex active flow control techniques that use new multidisciplinary and evolutionary physical mechanisms, such as electromagnetic and plasma discharge flow control, right from launch phase to touchdown. Hence, there is a need and demand to develop a multidisciplinary numerical tool considering the pertinent multiphysics environment for addressing research and development needs, as well as for analysis of various hypersonic flow control problems. A schematic of the hypersonic cruise vehicle configuration based on the RLV concept is shown in Fig. 1. At hypersonic speeds, since the angle of the nose oblique shock is narrow, the entire forebody can be used for compressing the air, and hence forms part of the scramjet engine intake. Due to this, the intake characteristics are strongly coupled to the forebody shape of the HSCV; hence, the forebody is highly design optimized to provide adequate air ram compression and mass capture at the inlet. The exhaust duct of the HSCV scramjet engine is shaped as a nozzle having a considerable length, and it forms part of the HSCV aftbody. The nozzle provides adequate expansion of the combusted gases, which in turn provides thrust to the vehicle. It can be observed that there is a tight coupling of airframe with the propulsion system, and the flight conditions influence the propulsive performance, which in turn affects the aerodynamic performance of the vehicle as a whole, and hence necessitates an integrated aeropropulsive design approach. One of themain challenges encountered in theHSCVdesign is that an adequatemass flow rate should be captured at the inlet and the inlet should start. During offdesign flight conditions, the air mass captured by the air intake might drastically reduce, which can result in flameout and thrust loss. To counter the technical challenges of the HSCV design, such as the subcritical air-intakemass flow rate, high forebody heat flux rates, active thermal management, onboard power generation, thrust augmentation, etc., Vladimir Freighstadt of the Leninetz Holding Company inRussia proposed a novelAJAXvehicle concept [3] in the late 1980s. The AJAX concept hypersonic cruise aircraft was proposed to fly in the mesosphere (50–80 km altitude range) and incorporated various novel technologies based on plasma generation, magnetohydrodynamics (MHD) flow control systems, MHD power generation for controlling and augmenting the hypersonic flow, as well as for thermal management schemes [4–6]. The concept was conceived to use the existing adverse hypersonic environment around the vehicle toward its advantage. The AJAX concept made extensive utilization of MHD-based flow control techniques, where the fluid that was preionized and made electrically conducting was easily manipulated by an externally applied magnetic field. Hence, the hypersonic flowfield could be easily modified for convenience, even at offdesign flight conditions, by application of a suitable magnetic field. Due to the use of various onboard MHD subsystems, such as the MHD-controlled inlet or MHD generator and MHD accelerator, the hypersonic ramjet engine is referred to as the magnetoplasma chemical engine, or MPCE. The schematic of the AJAX concept HSCV [6,7] is shown in Fig. 2. It has a waverider type of forebody design, followed by a flat upper surface to the body end, and it houses the MPCE along the midsection of the lower surface. The MHD generator shown in the figure inhibits the mass flow rate by application of a suitable magnetic field, thereby generating electric current. The hydrocarbon endothermic fuel is converted into the hydrogenenriched mixture and fed into the plasma-stabilized combustor for thermochemical reaction, and it sets on the combustion process. The exhaust products of combusted gas when entering the nozzle region are further accelerated using the MHD accelerator for providing additional thrust. The power source for theMHDaccelerator is drawn from the electricity produced by the MHD generator at the inlet. Since the oncoming air is preionized at the nose region of the HSCV, the overall drag of the vehicle is also reduced significantly. The ionizer housed at the nose region is a microwave beam generator that gets its power supply fromMHDgenerator. As adequate power is generated within the MPCE to solve the high-energy needs of the Received 26 January 2016; revision received 5 May 2016; accepted for publication 16 May 2016; published online 24 June 2016. Copyright © 2016 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal and internal use, on condition that the copier pay the per-copy fee to the Copyright Clearance Center (CCC). All requests for copying and permission to reprint should be submitted to CCC at www.copyright.com; employ the ISSN 0022-4650 (print) or 1533-6794 (online) to initiate your request. *Directorate of Computational Dynamics; bals.cfd@gmail.com (Corresponding Author). Directorate of Computational Dynamics.

Influence of electron beam welding parameters on microstructure and Charpy impact properties of boron-added modified 9Cr-1Mo steel weld

Abstract: The effect of electron beam welding parameters on microstructure and ductile-to-brittle transition temperature (DBTT) of a boron-added modified 9Cr-1Mo steel weld is presented in this paper. Compared to the base metal, for the weld, the upper shelf energy is lower and the DBTT is significantly lower. While the influence of welding parameters on the upper shelf energy of the weld is insignificant, its influence on the transition region and the lower shelf region is quite significant due to the presence of delta-ferrite in the weld. High welding speed reduces the time available for transformation of delta-ferrite to austenite and results in retention of delta-ferrite in weld. Lower welding speed promotes completion of delta-ferrite to austenite transformation as cooling rate reduces which improves lower shelf energy.

Modal Analysis of Monolithic and Jointed Type Cantilever Beams with Non-Uniform Section

Abstract: Modal analysis of non-uniform bolted structures are of significance in modeling many complex mechanical structures. There are vast literatures available related with the analytical as well as numerical modeling of bolted joint. However, most of the analytical model discuss about the modeling of first mode of uniform structures with single bolted joint. In this paper, we present the modeling of single as well as bolted non-uniform beams using approximate mode shapes. To develop the model, we first carry out experiments to measures the modal frequencies and shapes of the test structures. Subsequently, we also do numerical modeling of non-uniform beams in ANSYS to verify the validity of the Euler-Bernoulli beam theory in developing the analytical models. Finally, using the Euler-Bernoulli beam theory, we obtain the analytical values of frequencies using the approximate the mode shapes. The analytical results are found to be closer to the experimental results with a maximum percentage error of about 15 %. The model presented in the paper can be extended to the mechanical structures with many non-uniform sections with or without bolted joints.

Fuzzy risk assessment for electro-optical target tracker

Abstract: Purpose – The purpose of this paper is to evolve a guideline for scientists and development engineers to the failure behavior of electro-optical target tracker system (EOTTS) using fuzzy methodology leading to success of short-range homing guided missile (SRHGM) in which this critical subsystems is exploited Design/methodology/approach – Technology index (TI) and fuzzy failure mode effect analysis (FMEA) are used to build an integrated framework to facilitate the system technology assessment and failure modes Failure mode analysis is carried out for the system using data gathered from technical experts involved in design and realization of the EOTTS In order to circumvent the limitations of the traditional failure mode effects and criticality analysis (FMECA), fuzzy FMCEA is adopted for the prioritization of the risks FMEA parameters – severity, occurrence and detection are fuzzifed with suitable membership functions These membership functions are used to define failure modes Open source linear prog

Roll autopilot design of a tactical missile using higher order sliding mode technique

Abstract: Tactical missiles are used against various aerial/ground targets which can be stationary or maneuvering. Tactical missiles should have highly efficient control scheme in order to intercept such targets with acceptable miss distance. It is known that aerodynamic characterization of the missile with high accuracy is very difficult. In addition to this, the inability to model the external disturbances make the autopilot design very difficult. Hence, the need for a robust control arises in the presence of parametric uncertainties and unmodelled external disturbances. Sliding Mode Control (SMC) which has got invariance property against external disturbances and the model inaccuracies has been applied to this plant. This paper concentrates on application of higher order sliding mode control for the roll autopilot design of a tactical missile. Conventionally, the roll autopilot is designed with roll angle and roll rate feedbacks. The addition of roll acceleration feedback helps to obtain a tighter control of roll dynamics especially during high angle of attack requirements. However, the roll acceleration is neither measurable nor estimable by numerical differentiation of roll rate feedback. A differentiator based on Super Twisting Algorithm (STA) is explored to estimate roll acceleration from roll rate measurement. The use of roll acceleration feedback in the autopilot ensures tight control of roll dynamics. The robust sliding mode control gains are designed using Linear Matrix Inequalities (LMI) based technique.

Computational Fluid Dynamics Simulation of Combustion Instability in Solid Rocket Motor : Implementation of Pressure Coupled Response Function

Abstract: Combustion instability in solid propellant rocket motor is numerically simulated by implementing propellant response function with quasi steady homogeneous one dimensional formulation. The convolution integral of propellant response with pressure history is implemented through a user defined function in commercial computational fluid dynamics software. The methodology is validated against literature reported motor test and other simulation results. Computed amplitude of pressure fluctuations compare closely with the literarture data. The growth rate of pressure oscillations of a cylindrical grain solid rocket motor is determined for different response functions at the fundamental longitudinal frequency. It is observed that for response function more than a critical value, the motor exhibits exponential growth rate of pressure oscillations.

A Singular Perturbation Based Midcourse Guidance Law for Realistic Air-to-Air Engagement

Abstract: In this study, a singular perturbation based technique is used for synthesis and analysis of a near optimal midcourse guidance law for realistic air-to-air engagement. After designing the proposed midcourse guidance law using three dimensional point mass formulation it has been validated through detailed realistic six degrees of freedom simulation. During terminal phase only proportional navigation guidance have been used. The calculation of optimal altitude in present guidance law has been carried out using Newton’s method, which needs generally one iteration for convergence and suitable for real-time implementation. Extended Kalman filter based estimator has been used for obtaining evader kinetic information from both radar and seeker noisy measurements available during midcourse and terminal guidance. The data link look angle constraint due to hardware limitation which affects the performance of midcourse guidance has also been incorporated in guidance law design. Robustness of complete simulation has been carried out through Monte Carlo studies. Extension of launch boundary due to singular perturbation over proportional navigation guidance at a given altitude for a typical engagement has also been reported.

A Novel CFD Method to Estimate Heat Transfer Coefficient for High Speed Flows

Abstract: Accurate prediction of surface temperature of high speed aerospace vehicle is very necessary for the selection of material and determination of wall thickness. For aerothermal characterisation of any high speed vehicle in its full trajectory, it requires number of detailed computational fluid dynamics (CFD) calculations with different isothermal calculations. From the detailed CFD calculations for different flow conditions and geometries, it is observed that heat transfer coefficients scale with the difference of adiabatic wall temperature and skin temperature. A simple ‘isothermal method’, is proposed to calculate heat flux data with only two CFD simulations one on adiabatic condition and other on isothermal condition. The proposed methodology is validated for number of high speed test cases involving external aerodynamic heating as well as high speed combusting flow. The computed heat fluxes and surface temperatures matches well with experimental and flight measured values.

Development and Validation of a Grid-Free Viscous Solver

Abstract: N UMERICAL simulation of the flowfield of a practical configuration poses severe difficulty due to complex gridgeneration procedures. A Cartesian grid with near-wall extruded grids [1], chimera or overset grids [2], grid-free methods [3], and a combination of the aforementioned methods [4] is used to solve flow past complex configurations. The grid-free methods operate on a distribution of points in the domain and require a set of supporting nodes around each point to evaluate the spatial derivatives of the governing fluid equations. The point distribution can be obtained from structured, unstructured, Cartesian, hybrid, or overlapped meshes, or a randomdistribution of points. In recent years, quite a few grid-free methods were proposed in the field of compressible fluid flow. Among them, the least-squares kinetic upwind method developed by Deshpande et al. [5] has received much attention of researchers and been applied to number of complex flight vehicle configurations. Recently, the method was successfully applied to a store separation dynamics problem using a chimera cloud of points [6]. Batina [7] developed a gridlessmethod that used the least-squares method with the unbiased support of points for the discretization of spatial derivatives. Artificial viscosity is used to stabilize the solutions and applied to inviscid and laminar flows. Lohner et al. [8] developed a finite point method, in which an upwind scheme was used to stabilize the solutions, and applied it to inviscid compressible flows. In the finite point method, the direction of upwinding is based on coefficients of the least-squares discretization, which is purely geometric. In recent years, the grid-freemethod has been successfully applied to simulate turbulent flow past complex flight vehicle configurations [9,10]. These methods used either overset grids or extruded layers of points near the wall, along with Cartesian grids in the offbody region, to get the distribution of points; and neighbors are obtained using search algorithms guided by grid information, which is therefore known as the semimeshless method. Lohner et al. [8] developed the advancing point generationmethod to generate a cloud of points, and the neighbors of those points were obtained using a local Delaunay triangulation. The applications, so far, are limited to subsonic and transonic flows. In the present work, a grid-free Euler and Navier–Stokes (GEANS) solver has been developed using a gridless method [7] with upwind fluxes for flow stabilization, and it has been validated for hypersonic flows at higher angles of attack. One of the main drawbacks of the grid-free methods is the lack of conservation. Katz and Jameson [11] enforced conservation by modifying weights in the least-squares discretization. However, such modified weights may become negative for certain distribution of points that leads to nonpositive solutions. Chiu et al. [12] proposed a method of generating meshless coefficients with conservation constraints at the discrete level; however, thismethodwas complex to implement for three-dimensional (3-D) problems with an anisotropic distribution of points. In the present work, high-speed flows are simulated without enforcing the conservation property. A detail experimental results [13] for an all-body hypersonic aircraft is available for comparison of aerodynamic forces and moments in addition to local flowfields. The flowfield around the geometry is very complex, which involves strong compressions in the windward side and strong expansions in the leeward side, with flow separation and vortices at a hypersonic Mach number. Furthermore, highaspect-ratio grid cells are required to resolve the very fine details of the flowfield. The simulation of such flowfields requires a robust flow solver that can handle both strong oblique shock wave and high expansion regions, as well as be accurate enough to resolve the boundary layer. Therefore, the aforementioned configuration is considered for validating the grid-free Euler and Navier–Stokes solver [14] at hypersonic speed and the results are compared with the experimental values. The geometry considered for validations in the present work is simpler and amenable for generation of simple structured grids. Therefore, structured grids are generated around the body to get a distribution of points and supporting nodes are obtained using the structured grid adjacency relation.

Aerodynamic characterisation of ramjet Missile through combined External-internal computational Fluid dynamics Simulation

Abstract: Combined external-internal flow simulation is required for the estimation of aerodynamic forces and moments of high speed air-breathing vehicle design. A wingless, X-tail configuration with asymmetrically placed rectangular air intake is numerically explored for which experimental data is available for different angles of attack. The asymmetrically placed air intakes and protrusions make the flow field highly three-dimensional and existing empirical relations are inadequate for preliminary design. Three dimensional Navier Stokes equations along with SST-kω turbulence model were solved with a commercial CFD solver to analyse the combined external and internal flow field of the configuration at different angles of attack. Estimated aerodynamic coefficients match well with experimental data and estimated drag coefficient are within 8.5 per cent of experimental data. Intake performance parameters were also evaluated for different angles of attack.

Synchronization of high speed OFDM links using variations of Schmidl Cox for SNR improvement

Abstract: Owing to the growing demand for the high-speed wireless communications which uses Orthogonal Frequency Division Multiplexing (OFDM), there is a need to provide high-quality to overcome various channel impairments appearing over the transmission link. One of the main problems in providing such mechanisms is Doppler shift. which reduces the spectral efficiency of the system, raising a need to determine its value with high accuracy. In order to estimate this frequency shift, first the timing recovery is required. Over the years, Schmidl Cox algorithm has been used to determine this Doppler shift with considerate amount of success. But, with the increasing speed of the vehicle and the worsening channel conditions, this algorithm succumb to failure. The paper discusses the limitations of basic Schmidl Cox algorithm and the necessary improvements to be made, so as to push them to work better at harder conditions too.

Damping of modal perturbations in solid rocket motors

Abstract: Quasi-one-dimensional (quasi-1D) tools developed for capturing flow and acoustic dynamics in non-segmented solid rocket motors are evaluated using multi-dimensional computational fluid dynamic simulations and used to characterise damping of modal perturbations. For motors with high length-to-diameter ratios (of the order of 10), remarkably accurate estimates of frequencies and damping rates of lower modes can be obtained using the the quasi-1D approximation. Various grain configurations are considered to study the effect of internal geometry on damping rates. Analysis shows that lower cross-sectional area at the nozzle entry plane is found to increase damping rates of all the modes. The flow-turning loss for a mode increases if the more mass addition due to combustion is added at pressure nodes. For the fundamental mode, this loss is, therefore, maximum if burning area is maximum at the centre. The insights from this study in addition to recommendations made by Blomshield(1) based on combustion considerations would be very helpful in realizing rocket motors free from combustion instability.

Distributed real-time Radar Simulation Test bed for qualification of mission critical systems

Abstract: Testing of radar based systems is an arduous exercise and it is essential to develop a real-time radar simulator for testing such systems. However, as radar simulation test bed demands more computational resources to meet the real-time deadlines, it turns out to be more complicated than the system being tested. Distributed computing provides an elegant solution for its need of high computational resources. However, it calls for data, event and time synchronization among the processors. In this paper, we present a successful realization of distributed real-time Radar Simulation Test bed for testing mission critical systems.

Quasi-One-Dimensional Modeling of Internal Ballistics and Axial Acoustics in Solid Rocket Motors

Abstract: An unsteady quasi-one-dimensional flow solver for simulating internal ballistics and axial acoustic fluctuations in solid rocket motors is presented in this paper. Higher-order numerical solutions of quasi-one-dimensional governing equations are prone to numerical oscillations due to the nonconservative form of the governing equations and the nonsmooth axial variations of the cross-sectional area. Adding artificial dissipation to a central scheme is found to be inadequate for suppression of such oscillations, and so a simple low dissipation shock-capturing scheme (named SLAU2) is used instead. The inherent numerical dissipation of this scheme is helpful in the proper capturing of steep-fronted acoustic waves (that develop at the onset of triggered instabilities) without undesirable numerical damping of the acoustic waves. Using the new solver, a procedure for computing characteristic frequencies, corresponding mode shapes, and damping rates is proposed and validated for a motor with a cylindrical grain ge...

Post Boost Track Processing Using Conventional DBMS Software

Abstract: The design of air defence, traditional command control system is very challenging which has been used with basic methodologies. Traditional design is associated with unstructured and uncorrelated data and requires huge lines of code using hard disk drive (HDD) in the system. Hence an attempt was made for a better simplified database management system (DBMS) software data access methodology, which processed the incoming airborne data, message in RDBMS database to achieve full automation on real-time. The transaction is accomplished through SQL pass through method from the host decision making system into database. An algorithm of track identification during midcourse track separation was undertaken for prototype development on DBMS data access methodology. In this methodology Oracle C++ calls interface embedded query call was used from the host interface system. The purpose of this development was to find a comparison of online process timing between HDD and SSD using commercial database, and to evaluate performance of dynamic processing of RDBMS Database for identification of target vehicle and booster after separation. Produced experimentation results from improved performance of the proposed methodology on which futuristic command control system can rely.