Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

Studies on Flame Spread with Sudden Expansions of Ports of Solid Propellant Rockets under Elevated Pressure.

Abstract: A detailed experimental study on flame spread over non-uniform ports of solid propellant rockets has been carried out. An idealised. 2-dimensional laboratory motor was used for the experimental study with the aid of cinephotography. Freshly prepared rectangular HTPB propellant with backward facing step was used as the specimenfor this study. It has been shown conclusively that under certain conditions of step location. step height and port height which govern the velocity of gases at the step by the partially ignited propellant surface. secondary ignition may occur far downstream of the step. This is very likely to be within the recirculatingflow region. The secondary ignition gives rise to two additional flame fronts one of which spreads backwardat a relatively lower velocity,presumably due to the low reverse velocities present around the separation zone. This phenomenon is likely to play an important role in the ignition transient of solid propellant rockets with non-uniform ports.

Automatic Landing System Design using Feedback Linearization Method

Abstract: Nonlinear control using feedback linearization method is employed to develop automatic landing controller for a fighter aircraft. The three-degree-of-freedom nonlinear aircraft model with elevator as control input is established using the appropriate aerodynamic data from wind tunnel test. The model also considers the landing gears, flaps and speed brakes. Elevator is used to control the angle of attack by means of pitch attitude and throttle controls the speed. The feedback linearization control technique guarantees good tracking performance with respect to a given glideslope trajectory. An exponential trajectory is employed during the flare, which needs a tighter control and hence requires both the altitude and sink rate for the feedback purpose. The elevator dynamics and the engine dynamics are modelled for the simulation purpose. The controllers are tuned considering the “ground effect” encountered during landing, which was mathematically modelled. Nonlinear simulation under measurement noises and external disturbances are included in this study. Simulation results show the importance of designing the controller considering the ground effect.

The impact of the January 15, 2010, annular solar eclipse on the equatorial and low latitude ionospheric densities

Abstract: [1] The January 15, 2010, solar annular eclipse crossed the magnetic equator in the middle of the day over India, in a region instrumented with several magnetometers, Total Electron Content stations using GPS data, and an ionosonde located very near the center of the eclipse. With the help of a one-dimensional model appropriate for the region of interest we show that the ionosonde data was consistent with a lower F region plasma that was moving upwards with only modest velocities in the morning hours and moving resolutely downwards in the afternoon hours. This motion agreed well with the local magnetometer data which revealed a weakened electrojet taking place in the morning hours while a full-blown counter-electrojet was present in the afternoon hours. We show that the unusual solar eclipse-induced electrodynamics resulted in a reduction in the Total Electron Content depletion not just at the magnetic equator but also, more markedly, in the Equatorial Ionization Anomaly (EIA) zone, a further 10 degrees to the north. This latter point clearly shows that the eclipse led to a cut-off in the supply of plasma provided through the equatorial fountain, by altering a fundamental aspect of the equatorial electrodynamics.

On the flow localization concepts in the processing maps of IN718

Abstract: On the basis of microstructural observations in titanium and its alloys, a limit on the workability parameters has been proposed in the literature for flow localization or fracture to occur during hot deformation of materials. In this letter, the fixed limit on the workability parameters is verified by considering the flow stress data and the microstructural observations of IN718.