DESIGN OF LUNAR AND INTERPLANETARY ASCENT TRAJECTORIES
The near-Earth or "ascent" portion of lunar and interplanetary trajectories is investigated. Of particular interest is the matching of the powered-flight and coasting phases. To achieve a suitable match, consideration of vehicle-related engineering constraints, payload, and geometrical and energy requirements imposed by the extraterrestrial trajectory is essential. The geometrical constraints and trajectory shaping are treated in detail. To satisfy these constraints, direct-ascent and parking-orbit types of trajectories are investigated and compared. Advantages and disadvantages of each are noted. The superiority of the parking-orbit type is illustrated. It is shown that this type has consistently greater pay load capability and provides a convenient method of launch-time delay compensation. Finally, injection locations of Mars and Venus trajectories using parking orbits are mapped.