A Proposal for Graph-Theoretic Modeling Approach to Resource-Economy in Spaceflight Campaign Logistics

Abstract

NASA’s new direction for human spaceflight reaffirms that Mars is the ultimate goal of human exploration of the inner solar system. In response to this background, we can expect to see an increasing number of robotic explorations of Mars over the next several decades, followed by human missions. In a period of transition to a new era of space exploration, the question is what the next space logistics paradigm should be. Adding to the technical challenges, logistical concerns should be considered far in advance. A well-planned logistics strategy is essential to balance risks, ensure robustness, and achieve maximum exploration capability. Space logistics is an emerging topic in recent years as we start to see space exploration not as a set of isolated missions but as an intricately-linked exploration campaign. A vast body of research exists for terrestrial transportation networks and supply chain logistics in business and military applications. However, space exploration introduces several fundamental differences such as infrequent launch windows, long transport durations, and minimal cargo capacity. The past studies on space logistics have been mainly focused on a “vehicle” perspective such as propulsive feasibility, cargo capacity constraints, manifesting strategies, and demand satisfaction, assuming a pre-defined logistics network. However, there is more than one way to define a logistics network (transfer points) between origin and destination such as ISRU on the surface nodes and resource depots in orbital nodes or Lagrangian nodes. Therefore, this paper proposes a graph-theoretic modeling approach to analyze spaceflight campaign logistics seeking for “resource-economy” from a “network” perspective. We define resource-economy in the context of space exploration, identify the building blocks of logistics network (nodes, arcs, and costs), and present a quick example to show the potential benefits of ISRU and resource depots. Once the generic framework has been modeled and implemented, it will be able to be used a proof of concept, providing a useful index of resource-economy to quantitatively compare different concepts of exploration. Moreover, this framework will not only evaluate and compare specific scenarios but also find the key drivers of resource-economy in space logistics.