On-orbit Assembly Strategies for Next-generation Space Exploration

As the world looks ahead to the next generation of space exploration programs, we must focus on designing architectures for both sustainability and affordability. By viewing exploration programs as a “system-of-systems,” we can focus on reducing costs through the use of flexible, reusable infrastructures to support various aspects of manned and unmanned spaceflight. This paper addresses one key aspect of affordable exploration programs by tackling the issue of high costs for access to space. While launch vehicle trades for exploration programs are relatively well understood, on-orbit assembly has been given much less attention, but is an equally important component of the infrastructure enabling human access to space. This paper explores a number of on-orbit assembly methods for modular spacecraft, in order to understand the potential value of a reusable assembly support infrastructure. Four separate assembly strategies involving module self-assembly, tug-based assembly, and in-space refueling are modeled and compared in terms of mass-to-orbit requirements for various on-orbit assembly tasks. Results show that the assembly strategy has a significant impact on overall launch mass, and reusable space tugs with in-space refueling can significantly reduce the required launch mass for on-orbit assembly.