Sub-optimal Low-thrust Trajectories for Human Mars Exploration

The application of the usual optimization techniques to the computation of low thrust interplanetary trajectories is made difficult by some criticality in the choice of the first approximation trajectory and thrust profile, needed to start the numerical procedure. Some simple starting functions are here obtained with the aim of allowing to easily and quickly compute optimized interplanetary trajectories. General results regarding the relationship linking the travel time for the Whole interplanetary travel between the low orbits about the planets, the propellant consumption and the spacecraft performance can thus be easily obtained. The case of human Mars missions is studied in detail, and general considerations are drawn to identify some critical technologies which can allow to substantially shorten the travel time in case of human carrying interplanetary spacecraft or to greatly increase the payload, at equal initial mass, in case of slower cargo ships