Accession Number : ADA243933

Title :   Performance and Stability Analysis of the Non-Linear Dynamics of a Simple Powered Lifting Hypersonic Vehicle Flying on a Minor Circle.

Descriptive Note : Master's thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Zavala, Mark A.

Report Date : DEC 1991

Pagination or Media Count : 162

Abstract : The nonlinear equations of motion for a hypersonic vehicle flying on a minor circle were modeled using the control design and simulation software package, MATRIXx. The model includes earth rotation and gravity gradient effects. Aerodynamic forces and moments are expressed as first order Taylor series expansions using the full nonlinear expression for the dynamic pressure. Minor circle equilibrium flight conditions are generated via a Newton iteration technique (Turbo Pascal program) for both a rotating and non-rotating earth model. Equilibrium performance over speeds from Mach 5 to Mach 40 and 0 to 85 degree latitudes at east and west flight headings are compared. The speed and latitude determine equilibrium bank angles, altitude, and roll, pitch, yaw control moments (to sustain minor circle flight). These parameters are analyzed to assess equilibrium performance. Results show that earth rotation and gravity gradient torques have significant effects on performance. The system is shown (via MATRIXx) to be marginally unstable. For near-major circle routes, the modes are poorly damped and decoupled into lateral and longitudinal modes. For mid-latitude minor circle routes, the modes are poorly damped and coupled. However, the modes are comprised of either mostly longitudinal or mostly lateral states. For minor circle latitudes greater than 65 deg, we see poorly damped coupled modes, with new mode shapes appearing as equilibrium speeds increase.

Descriptors :   AERODYNAMIC FORCES, ATTITUDE CONTROL SYSTEMS, CIRCLES, COMPUTER PROGRAMS, COMPUTERIZED SIMULATION, CONTROL, COUPLING(INTERACTION), DAMPING, DYNAMIC PRESSURE, DYNAMICS, EARTH MODELS, EARTH(PLANET), EQUATIONS OF MOTION, EQUILIBRIUM(GENERAL), FLIGHT, GRADIENTS, GRAVITY, HYPERSONIC VEHICLES, ITERATIONS, LATITUDE, MOMENTS, NONLINEAR ANALYSIS, NONLINEAR SYSTEMS, PACKAGING, PITCH(INCLINATION), ROTATION, ROUTING, SIMULATION, STABILITY, TORQUE, VELOCITY, YAW.

Subject Categories : Spacecraft Trajectories and Reentry

Distribution Statement : APPROVED FOR PUBLIC RELEASE