Showing papers by "Vikram Sarabhai Space Centre published in 1988"

Large deflections of a nonuniform cantilever beam with end rotational load

Abstract: Large deflection analysis of a cantilever beam under a tip concentrated rotational load governed by a second order nonlinear differential equation is solved with a simple and accurate numerical scheme. The details of load deflection curves for a class of beams having variable cross-section are presented.

Long-term orbit computations with KS uniformly regular canonical elements with oblateness

Abstract: This paper concerns with the study of KS uniformly regular canonical elements with Earth's oblateness. These elements, ten in number, are all constant in the unperturbed motion and even in the perturbed motion, the substitution is straightforward and elementary due to the transformation laws being explicit and closed expression. By utilizing the recursion formulas of Legendre's polynomials, we are able to include any number of Earth's zonal harmonics J n in the package and also economize the computations. A fixed step-size fourth-order Runge-Kutta-Gill method is employed for numerical integration of the canonical equations. Utilizing 5 test cases covering a large range of semimajor axis and eccentricity, we have carried out computations to study the effects of Earth's zonal harmonics (up to J 36) and integration step-size variation. Bilinear relations and energy equation are used for checking the accuracies of numerical integration. From the application point of view, the package is utilized to study the behaviour of 900 km height near-circular sun-synchronous satellite orbit over a longer duration of 220 days time (nearly 3078 revolutions) and the necessity of including more number of Earth's zonal harmonic terms is noticed. The package is also used to study the effect of higher zonal harmonics on three 900 km height near-circular orbits with inclinations of 60, 63.2, and 65 degrees, by including Earth's zonal harmonics up to J 24. The mean eccentricity (e m) is found to have long-periods of 459.6, 6925.1 and 1077.6 days, respectively. Sharp changes in the variation of Ωm near the minima to em are noticed. The values of Ω m are found to be very near to +-90 degrees at the extrema of em. The same orbit is employed to study the effect of variation of inclination from 0 to 180 degrees on long-period (T) of eccentricity with J 2 to J 24 terms. T is found to increase rapidly as we proceed towards the critical inclinations.

Behaviour of harmonic components of the geomagnetic field during counter electrojet events.

Abstract: On presente une analyse harmonique des donnees des composantes du champ geomagnetique durant les episodes de contre-electrojet equatorial pour 4 stations

Thermal Functional Polymeric “Iniferters” Based on Phosphorus-Containing Poly(Thiuram Disulfides); Synthesis and Characterization

Abstract: Secondary amine end-terminated oligomeric poly(phosphonamides) and poly(phosphorylamides) were synthesized by the condensation reaction of phenylphosphonic dichloride, ethyl dichlorophosphate, 2,2,2-tribromoethyl dichlorophosphate, and 2,2,2-trichloroethyl dichlorophosphate with an excess of piperazine or N,N′-dimethyl-1,6-hexanediamine. The macrodiamines were chain extended by reaction with CS2 to the macrobis(dithiocarbamates) followed by oxidative coupling to the corresponding poly(thiuram disulfides) bearing the phosphorus functions. The diamine precursors and their polythiuram disuffides were characterized by elemental analysis, spectral analysis, thermal analysis, and viscosity measurements. The thermal stabilities of the prepolymers were correlated with their structures. The composition of the thiuram disulfide functions could be determined by TGA, whereas the kinetics of their thermal decomposition in the solid state was studied by DSC analysis. The activation energy varied with the chemi...

Development of navigation guidance and control technology for Indian launch vehicles

Abstract: The orbital injection accuracy of any payload depends on the calibre of the inertial guidance system used on board the launch vehicle. This paper outlines the mission definition and the rationale for the selection of a proper guidance system to meet final mission objectives. The functions and the architecture of the navigation, guidance and control are discussed. The developmental aspects of the sophisticated inertial sensors, inertial systems, associated complex electronics, on-board computers, control actuators and systems are reported. The complexity of the on-board control and guidance software and the test and evaluation procedures used for their validation are included. The general scheme of the inertial guidance systems and the critical role played by them in the realization of Indian satellite launch vehicles SLV-3, ASLV and PSLV are presented in brief.

A profile of aerodynamic research in VSSC with application to satellite launch vehicles

Abstract: Some of the aerodynamic and fluid dynamic problems associated with the satellite launch vehicles of the Indian Space programme are discussed in this paper. Taking into account the aerodynamic flight profile of a launch vehicle and also the configurations of interest, the topics considered are vehicle lift-off fluid dynamics, strap-on aerodynamics, strap-on separation problem, stage separation aerodynamics, boat-tail aerodynamics, hypersonic flow problems and some special fluid dynamic problems of interest like nozzle flows and shock wave-boundary layer interaction. The topics are mostly related to external fluid dynamics though certain aspects of internal ballistics are also touched upon. More emphasis is placed on the results and their applications rather than on the methodology used. Also, the main features of two special wind tunnel facilities developed at the Vikram Sarabhai Space Centre (VSSC) — the hypersonic wind tunnel and the heat transfer facility — are discussed briefly.

Finite element analysis of conductive and radiative heating of a thin skin calorimeter

Abstract: The main purpose of the present work is to investigate the influence of normal and lateral conduction on the temperature distribution and heat transfer coefficient on the surface of a typical sounding rocket.

Monte carlo simulation for molecular gas dynamics

Abstract: The dynamics of low-density flows is governed by the Boltzmann equation of the kinetic theory of gases. This is a nonlinear integro-differential equation and, in general, numerical methods must be used to obtain its solution. The present paper, after a brief review of Direct Simulation Monte Carlo (DSMC) methods due to Bird, and Belotserkovskii and Yanitskii, studies the details of theDSMC method of Deshpande for mono as well as multicomponent gases. The present method is a statistical particle-in-cell method and is based upon the Kac-Prigogine master equation which reduces to the Boltzmann equation under the hypothesis of molecular chaos. The proposed Markoff model simulating the collisions uses a Poisson distribution for the number of collisions allowed in cells into which the physical space is divided. The model is then extended to a binary mixture of gases and it is shown that it is necessary to perform the collisions in a certain sequence to obtain unbiased simulation.

Effect of addition of an interfacial agent on the joint strength of a nitrile-phenolic structural adhesive

Abstract: A study was conducted to determine the effect of adding p-cresol formaldehyde (PCF) resin as an interfacial agent to a nitrile rubber (NBR)-phenol formaldehyde (PF) structural adhesive, on its joint strength, stress-strain properties, glass transition temperature (Tg), and morphology. The addition of PCF resin up to 20% showed a remarkable improvement in joint strength accompanied by an improvement in the mechanical properties. Scanning electron microscopy and DSC analysis (Tg) showed that the NBR/PF blend is a two-phase system and with the addition of PCF resin, the two phases tend to become continuous and the Tg of the NBR phase is increased. From the results obtained we propose that PCF acts as an interfacial agent and facilitates the bonding between the two phases, which improves the mechanical properties, and hence the joint strength. PCF contents above 20% produced a decrease in the joint strength, which is attributed to decreased toughness resulting from the high cross-linking of the NBR phase.

The axisymmetric melting of a homogeneous solid

Abstract: The process of axisymmetric melting of a homogeneous solid is analysed theoretically A free boundary problem consisting of continuity, momentum and energy balance with an appropriate boundary condition at the interface is formulated to describe the process of axisymmetric melting The analysis is simplified by the assumption of thermal boundary layer around the melting solid

Large deflection analysis of a nonlinear elastic column under uniformly distributed axial load

Abstract: Combined effects of geometrical and material nonlinearities on a uniform column subjected to a uniformly distributed compressive load are examined. The problem is solved using a simple and accurate numerical scheme. The details of load-deflection curves are presented.

Numerical investigation of the impingement of an oblique shock on a flat plate

Abstract: The unsteady, compressible Navier-Stokes equations in Reynolds-averaged variables are solved for a shock wave turbulent boundary layer interaction For the free stream Mach number 37 and Reynolds number 8202×106 computation is performed using MacCormack's explicit-implicit finite difference scheme with 42×42 grid points It is found that the peak heating amplification correlation agrees well with computational results