Om Prakash

View Video Presentation: https://doi.org/10.2514/6.2021-3271.vid The futuristic aspirations of quick global passage on Earth and in near future in Space can be achieved with the Air-breathing Hypersonic Vehicle (AHV). This paper presents the highly nonlinear dynamic AHV model with high altitude and Mach number analysis for the 3-DOF model. The topological behavior of AHV provides quantitative assessment of the equilibrium states for the entire wide flight regimes, nonlinear phenomena, static and dynamic stability, global stability of the AHV using Bifurcation Analysis. Flight dynamics analysis and stability for the generic AHV using 3-DOF dynamic simulation model is presented here with the Bifurcation Method.

An Attitude control system plays the important role to maintain the satellite to desired attitude orientations. The intended application of NANO satellite in low earth orbits (LEO) helps find transient responses with and without controllers. LEO satellites typically orbit at an altitude ranging between160-2000 km. LEO satellites are widely used for remote sensing, navigation, and military surveillance applications. The Nano NPSAT-1 satellite attitude control systems (ACS) are described in this research work. The high pointing accuracy attitude estimation and feedback control systems are presented. The design specifications have been taken to meet the accuracy requirements (desired value ≤ 0.2 seconds) of Nano satellite attitude control. The feedback signal from on-board sensors compared with reference orbit trajectory and implementation of the Proportional Derivative (PD) controller is constructed. An algorithm of Nano satellite (NPSAT-1) attitude control is implemented using MATLAB Tools. In addition, the closed loop poles help find the gain of the system using Root Locus (RL) methods. The satellite control system is used to improve the transient response like overshoot and settling time of the system. Thus, the design of attitude control to improve the rise time, the settling time, the maximum overshoot, and no steady state error was carried out.

The effects of attaching multiple ramps to the standard double ramp configuration along with variations in ramp angle, free-stream Mach number and surface temperature are discussed in this investigation. This study investigates the changes associated with shock wave boundary layer interaction (SWBLI) due to ramp induced flow breakdown and the flow field fluctuation with changes in flow characteristics and design. This type of ramp junctions typically features in re-entry vehicles, engine intakes, system and sub-system junctions, control surfaces, etc. Ramp junctions usually are associated with strong separation bubble that has significant upstream influence impacting the effectiveness of aerodynamic surfaces, engine performance, thermal behavior and stability. Computation studies are carried out using Second order accurate, finite volume RANS solver considering compressible laminar flow characteristics, with solver settings provided like experimental conditions as per literature. Comprehensive double ramp studies with suggestions on reducing the separation bubble size are invariantly considered in literature, however there has been no study in understanding the inclusion of additional ramps in such flow scenarios. At the end of this study it was evident that such complex junction needs detailed understanding on how they benefit or impact the overall design of the system. It also gave a very good insight on the nature of flow around such complex junctions and instills motivation for detailed experimental understanding.

Numerical simulation results are presented to show the effect of ramp angle variations and leading-edge bluntness on the flow around triple ramped cone flare in hypersonic flow. This study investigates the changes associated with shock wave boundary layer interaction due to ramp induced flow breakdown and the fluctuation in flow in the presence of blunted leading edge. This type of ramp junctions typically features in re-entry vehicles, engine intakes, system and sub-system junctions, control surfaces, etc. Ramp junctions usually are associated with strong separation bubble that has significant upstream influence impacting the effectiveness of aerodynamic surfaces, engine performance, thermal behavior and stability. Computation studies are carried out using finite volume-based RANS solver, accuracy of second order and considering compressible laminar flow characteristics, with solver settings provided similar to experimental conditions as per literature. Comprehensive double ramp studies with suggestions on reducing the separation bubble size are invariantly considered in literature, however there has been no study in understanding the inclusion of additional ramps in such flow scenarios, hence efforts are taken to understand the benefits and implications of including a third ramp along with varying bluntness on the bubble size and its upstream intensity.