Several years ago, a research program dealing with the optimization and guidance of flight trajectories from Earth to Mars and back was initiated at Rice University. The decision was based on the recognition that the involvement of the USA with the Mars problem had been growing in recent years and it can be expected to grow in the foreseeable future ( [1] [15]). Our feeling was that, in attacking the Mars problem, we should start with simple models and then go to models of increasing complexity. Accordingly, this paper deals with the preliminary results obtained with a relatively simple model, yet sufficiently realistic to capture some of the essential elements of the flight from Earth to Mars and back ( [16] [19]).
There are two basic alternatives for Mars missions: robotic missions and manned missions, the latter being considerably more complex than the former. Within each alternative, we can distinguish two types of missions: exploratory (survey) missions and sample taking (sample return) missions.
Regardless of alternative and type, there is a basic maneuver which is common to every Mars mission, namely, the transfer of a spacecraft from a low Earth orbit (LEO) to a low Mars orbit (LMO) and back. For both LEO-to-LMO transfer and LMO-to-LEO transfer, the first objective is to contain the propellant assumption; the second objective is to contain the flight time, if at all possible.
Under certain conditions, the propellant consumption is...
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