Robert M. Zubrin

Martin Marietta Astronautics

PO Box 179 Denver, CO 80201

David B. Weaver

Johnson Space Center

Houston, Texas

ABSTRACT

This paper investigates means for achieving human expeditions to Mars utilizing existing or near-term technology. Both mission plans described here, Mars Direct and Semi-Direct are accomplished with tandem direct launches of payloads to Mars using the upper stages of the heavy lift booster used to lift the payloads to orbit. No on-orbit assembly of large interplanetary spacecraft is required. In situ- propellant production of CH4/O2 and H2O on the Martian surface is used to reduce return propellant and surface consumable requirements, and thus total mission mass and cost. Chemical combustion powered ground vehicles are employed to afford the surface mission with the high degree of mobility required for an effective exploration program. Data is presented showing why medium-energy conjunction class trajectories are optimal for piloted missions, and mission analysis is given showing what technologies are optimal for each of the missions primary maneuvers. The optimal crew size and composition for initial piloted Mars missions is presented, along with a proposed surface systems payload manifest. The back-up plans and abort philosophy of the mission plans are described. An end to end point design for the Semi-Direct mission using either the Russian Energia B or a U.S. Saturn VII launch vehicle is presented and options for further evolution of the point design are discussed. It is concluded that both the Mars Direct and Semi- Direct plans offer viable options for robust piloted Mars missions employing near-term technology.