TABLE OF CONTENTS Astrodynamics is the study of the motion of man-made objects in space subject to both natural and artificially induced forces. It is the latter factor that lends a design element to astrodynamics that is lacking in its parent science, celestial mechanics. The function of the astrodynamicist is to synthesize trajectories that, within the limits imposed by physics and launch vehicle performance, accomplish desired mission goals. Experience gained since the dawn of the space age in 1957, together with the tremendous growth in the speed and sophistication of computer analyses, have allowed the implementation of mission designs not foreseen by early pioneers in astronautics. This trend was discussed briefly in Chapter 2 and shows every sign of continuing. The use of halo orbits [1] for the International Sun-Earth Explorer (ISEE) and Wilkinson Microwave Anisotropy Probe missions, the development of space colony concepts using the Earth-moon Lagrangian points, [2] together with the analysis by Heppenheimer [3] of "achromatic" trajectories to reach these points from the moon, and the extensive modern use of gravity-assist maneuvers [4] for interplanetary missions are but a few examples.
Astrodynamics, through its links to classical astronomy, has its roots in the very origins of the scientific revolution. The mathematical elegance of the field exceeds that found in any other area of astronautics. Problems posed in celestial mechanics have been a spur to the development of both pure and applied mathematics since Newton's development of the calculus (which he used, among other things,...
