| The present research is divided in two parts. The first part is a well defined mathematical problem, with exact rules and results, in which the basic constraints for interplanetary round trip travels are used to calculate an interplanetary train schedule (ITS) of missions to Mars, in the general case of orbits with non-zero eccentricity and non-zero inclination. Several possible options for round trip travels to Mars are considered. In particular, options at high energy, which allow rapid round trip missions, are discussed. These options have important applications for human travels to Mars.;The second part of the research is about systems engineering aspects, which are intrinsically less exact, since they can change with time due, for example, to technology development or economic and political factors. For the case of a selected human rapid round trip mission to Mars, the development of a mission architecture, an assessment of the masses involved in the mission (such as the initial masses required in LEO), an estimate of the necessary number of launches, and a preliminary analysis of the radiation protection requirements, are performed.;The main problem that justifies the existence of basic constraints for round trip missions is that by increasing the DeltaV of a mission, in general the total round trip time does not vary much, because a higher DeltaV can only reduce the transfer time and it simply increases the stay-time on the target planet. However, if the DeltaV is increased beyond a well-defined level, the total round trip time has a sudden drop in duration that makes fast round trips possible. This is due to the fact that the traveler can go back before the home planet makes one extra revolution around the Sun. For a sufficiently high DeltaV, a round trip to Mars can change in duration from 2.7 years to about 5 months.;For Mars missions, the round trip times are calculated for different DeltaV's and for different transfer trajectories (T1, T2, etc.). An interplanetary train schedule is created. The behavior of the constraints near transfer time limits, and the impact of real vs. ideal orbital elements of the Earth and Mars (where "ideal" indicates circular and coplanar orbits) are analyzed.;It was found that for the profiles examined (T1/T1, T1/T4, and NT1/NT4) and for the opposition of July 27th, 2018, the transfer times can be shorter by up to 4 weeks at outbound and by up to 6 weeks at return, compared to circular orbits. Instead, for the opposition of February 19 th, 2027, the transfer times can be longer by up to 6 weeks both at outbound and return, compared to circular orbits. Also, for the opposition of February 19th, 2027, rapid T1/T1 round trip missions are not possible given the farther distance between the Earth and Mars. In that case, only long-stay missions are possible.;For the systems engineering part of the research, a comparison between the requirements of a representative rapid round trip mission and those of three NASA Mars reference missions is made, in order to understand the relative advantages and disadvantages of the alternatives. In a rapid, short-stay round trip, the cost for life support system, consumables, and mission operations is smaller compared to a long duration trip, but the cost of the launch system is higher due to the increased propellant requirements.;The example chosen is an intermediate duration mission with a total round trip time of 1.11 years and a stay time of 25.1 days. The mission has a T1/T4 profile, starts on November 27th, 2026, and ends on January 8th, 2028. The conclusion is that the short duration mission is comparable to the NASA Mars reference missions in terms of practicality, number of launches, and masses involved. |
