Multidisciplinary evaluation of next steps for human space exploration: Technical and strategic analysis of options

There is a growing consensus among stakeholders around the world that the long-term objective of human space exploration is the long-duration presence of humans on the surface of Mars. However, the key question concerns the choice of near-term missions that will bridge current human spaceflight activities in low Earth orbit (LEO) and eventual Mars exploration. This paper contributes to this debate by identifying the scope of possible near-term missions, arguing that there are only four realistic proposals for initial human exploration beyond low Earth orbit: a cis-lunar habitat, asteroid redirect, Mars flyby, and a short lunar surface sortie. The paper then evaluates these missions across five criteria: 1) technical/economic feasibility, 2) contribution to the eventual goal of exploring Mars, 3) potential for international cooperation, 4) global readiness for the mission, and 5) political feasibility to establish a clear assessment of the pros and cons of each of these four missions. While recognizing that any one of these missions represents a feasible option for future human space exploration, we recommend that the international community pursue development of a cis-lunar habitat as its immediate goal. This mission maximizes development of technology necessary for Mars exploration, provides significant opportunities for meaningful international participation, and could be achieved on a reasonable schedule with current budgets. Both the asteroid redirect mission and lunar exploration plans have the potential to benefit from the development of a cis-lunar habitat and could be retained as intermediate or parallel missions, as resources allow.