Fabrication Time Diagrams for In-Space Manufacturing of Large Reticulated Structures

Abstract

In-space manufacturing (ISM), or the construction of structures from raw feedstock materials in the space environment, is a promising approach for building large, external support structures for future space missions. Most research and development on ISM to date has focused on ground-based or microgravity-based demonstrations of candidate fabrication processes; however, the combined design of the ISM spacecraft and the fabrication process has not been fully investigated. In this paper, we estimate the fabrication times for truss support structures subject to various spacecraft constraints, including the available fabrication power, the attitude control system (ACS) authority, and the avoidance of control–structure interactions. Using the key assumptions of (1) a fabrication process that sequentially extrudes struts, (2) a fixed spacecraft orientation, and (3) negligible effects of environmental disturbance torques, we generate fabrication time diagrams that depict the dominant constraints and estimates of the fabrication time for a range of dimensions. Our results indicate that for large, dense reticulated geometries such as the curved gridshell and tetrahedral truss, the angular momentum storage of the spacecraft ACS is the dominant constraint on fabrication time. Additionally, our results suggest the following strategies for reducing fabrication time: manufacturing with multiple spacecraft; using stiff, lightweight feedstock; maximizing fabrication power and ACS capability; and minimizing spacecraft bus mass. These strategies represent design tradeoffs, emphasizing how the design of an ISM spacecraft cannot be considered independently of the fabricated structure.