In-Space Operations: Developing a Path to Affordable, Evolutionary Space Exploration

This paper explores alternative options for future human spaceflight programs which meet the goals of the Vision for Space Exploration and the Augustine Commission, within achievable cost and time limits. Based on four decades of NASA experience in on-orbit operations, an architecture is developed that allows access throughout cislunar space, including the surface of the Moon, through the use of multiple docking propulsion modules to achieve the necessary mission ∆V. The basic axiom of this study is that all Earth launch must be accomplished solely with existing launch vehicles, to limit early budget requirements and minimize time between the start of the program and initial flight missions. Analysis of prior spacecraft is used to estimate the feasibility of a human spacecraft with a marginally smaller mass than the Apollo command module, which is capable of launch via a direct translunar injection on a human-rated Delta IV Heavy. An optimized standard propulsion module, the Orbital Maneuvering Stage, is designed for lunar descent and ascent, as well as multiple applications to in-space maneuvering. A modified version of this vehicle, the Terminal Landing Stage, includes landing gear and required avionics for the actual lunar landing. Along with dedicated costs to human-rate the Delta IV Heavy, overall cost analysis was performed to find total program costs, and allow a year-by-year budget plan which keeps the peak-year expense on this program below $2.5B. The final program developed provides semiannual rotation of six crew on the International Space Station, two annual human lunar exploration missions, and “Flexible Path” missions as suggested by the Augustine Commission every 24 months. This architecture will support 6-7 human spaceflight missions per year, with a requirement for 16-17 launches of the Delta IV Heavy or its human-rated variant per year.