Nonlinear Rigid-Body Equations Used in 6-Dof Simulations

This chapter discusses various nonlinear rigid-body equations of motion used in 6-DOF simulations, and begins with the nonlinear earth-based, simultaneous equations of motion. The vehicle roll, pitch, and yaw body rates about its center of mass are obtained by integrating the nonlinear rate of change of momentum equation. The attitude and direction of a rocket vehicle is controlled either by gimbaling the TVC engines, or by varying the thrust of the engines (throttling), or both. The aerodynamic model consists of a set of coefficients for the base vehicle, plus increment coefficients that provide additional forces for each aerosurface deflection. The forces acting on a vehicle from a sloshing propellant in a partially filled tank can be characterized by a nonlinear pendulum model. Turn coordination is desirable for passenger comfort and also the pilot functions more efficiently.