The primary objective of the Human Expedition to Mars three-mission set was to send the first human explorers to the Martian surface in order to capture early leadership in the piloted exploration of the solar system. Once there, the crew would conduct local geological reconnaissance, emplace long-lived geophysical instruments, and collect samples for return to Earth. An additional key objective was to conduct ancillary exploration of the Martian moons, Phobos and Deimos.
The transportation strategy employed for each of the three missions would be a split/sprint trajectory. For the first expedition, a cargo transport carrying the landing vehicle (including Mars surface habitat and exploration equipment and the ascent vehicle), and the Earth-return propellant would be launched via an expendable escape stage on a minimum-energy trajectory in September 2005. Upon arrival at Mars, this vehicle would be placed in Mars orbit to await the piloted flight. In December 2006, approximately 15 months after the first launch, a vehicle carrying eight crewmembers would be launched via an expendable escape stage on a high-energy, sprint-class trajectory. Upon arrival at Mars, the piloted vehicle would rendezvous with the cargo vehicle in Mars orbit. Four crewmembers would transfer to the Mars Lander Vehicle and depart for a 20-day exploration of the Martian surface. The four remaining crew members would perform the propellant transfer from the cargo to piloted vehicle, conduct Mars orbital science, and monitor and assist the activities under way on the surface of Mars. After a total of 30 days in the Martian system, the surface crew would rendezvous with the orbiting piloted vehicle to depart for Earth, arriving about 5 months later. Total mission length was 440 days.
Cargo/piloted vehicle pairs would again be launched to Mars during the next two launch opportunities (2009 and 2011). The third piloted flight, in 2011, had a total round- trip flight time of 500 days. This longer flight time was necessary to avoid prohibitive mass penalties associated with the sprint trajectory in 2011.Piloted excursions to Phobos and Deimos were envisioned as part of the first two Mars expeditions. Each of the three Mars landing missions would also visit a different site on the Martian surface.
The Mars expeditions would deliver a crew of eight to Mars, with four landing on the surface, but arrivals would begin almost five years later than the Phobos expedition. This difference resulted from the fact that the Mars case was of a much larger scale, with increased dependence on infrastructure and new technologies. The Mars expeditions would require significant LEO infrastructure and a substantial degree of on-orbit assembly operations at a LEO transportation node.
The Mars expeditions were more complicated than the Phobos expedition from several standpoints. Separate cargo and piloted vehicles must be built to land on (cargo and piloted) and ascend from (piloted) the Mars surface, significantly increasing the vehicular infrastructure complexity (and resultant IMLEO) for these missions. Mars EVA operations would require new pressure suits, portable life support systems, and surface transportation systems which could safely and productively operate in the Mars one-third gravity, non-vacuum environment. The fact that the Mars Expeditions launch to Mars over three successive opportunities introduces significant astrodynamic effects into the analysis. Substantial variations in mission delta-V requirements, and corresponding IMLEO, occurred as a result of the heliocentric trajectory sensitivity to launch year. The doubling of crew size from four (for Phobos) to eight for the Mars Expedition also introduced a level of complexity to the mission design. Due to the extremely large annual LEO mass requirements (peak year mass = l,770 metric tons), two of the major drivers affecting these expeditions were the Earth-to-orbit (ETO) level of activity and LEO assembly techniques.
It was important to acknowledge, however, that the IMLEO estimates to support the three missions associated with this particular case study were unrealistically high. It was also important that in deriving these estimates, the supporting analysts obtained a cause-and-effect knowledge base of the various transportation and surface systems element/trajectory sensitivities that drove IMLEO to these high levels. This knowledge would enable substantial reductions in IMLEO estimates for future Mars system expeditionary case studies.
Human Expedition to Mars Mission Summary: