Mission Planning

In traveling to the red planet, Mars Direct uses interplanetary transfer orbits that require about 2.6 years in round trips. Because of the hazards of space radiation and microgravity, it has been argued that high energy missions are necessary, as they only last about 1.6 years. However, the high-energy mission can double the total initial mass of the mission because of the need for more fuel, while engine time doubles and so does the possibility of engine failure. It is also more difficult, and dangerous, to maneuver the craft. The opposition mission also reduces time by cutting the time of the stay on the surface of Mars to 0.1 years. The orbit that this mission takes also loops very close to the sun, raising problems of heat control and especially radiation dosage.

A Hohmann transfer, or minimum energy orbit, has a flight time of 0.707 years (258 days) each way. To help reduce flight time, more energy could be added to the ERV for the return trip. A table follows that compares the two missions and the time they take.

Flight Times and Stay Times of Mars Missions

Radiation is also an important factor in the design of a mission. Cosmic rays are a constant hazard while solar flares can be fatal in large doses. If a nuclear engine is used, that is also another source of concern. For more info, see Space Medicine.