Introduction

This chapter is devoted to the modeling of actual gravitational accelerations and the forces and moments acting on the flight vehicle to simulate its real world motion. For example, the spherical gravitational field of the point mass, as discussed in the previous chapters, becomes the nonspherical field approximated by using the Legendre polynomial expansion to simulate the actual mass distribution of an astronomical body. The Two-Body Problem of astrodynamics becomes the Perturbed Two-Body Problem, where closed-form Keplerian motion solutions no longer describe the real motion of the space vehicle. Hence, motion solutions must be approximated by using perturbation analysis methods or the equations of motion must be numerically integrated using Cowell s method.

As a refresher for the reader, I have included subsections covering some of the important concepts of atmospheric modeling and also a brief description of the correspondence between aeronautical nomenclature and the variable names used in the text.

In the late 1960s, large scale digital computer system resources became availiable to the aerospace engineer. As a result a very exciting age began for the aerodynamist. Finite element aerodynamic modeling of the velocity flow fields over the flight vehicle surfaces are now possible. Using potential flow and fluid dynamic modeling the pressure coefficients on the vehicle surfaces can be estimated. This effectively simulates the actual airflows over the real flight vehicle. Both subsonic and supersonic airfoil sections, airplane wings, and indeed entire airplanes have been designed and tested long before the actual flight vehicle is test flown.

As...