Modular Structures for Manned Space Exploration: The Truncated Octahedron as a Building Block

TLDR

Modular space exploration systems have historically used linear stacks of cylindrical modules, which limits flexibility and reuse across missions. The study proposes that future exploration vehicles must be reconfigurable, with additional docking ports and improved structural and volumetric efficiency. The authors compare spacecraft geometries using volumetric efficiency, launch stowage, reconfigurability, and stability metrics. A survey and analysis show that the truncated octahedron is the most promising geometry, enabling extensible designs, though a modular Mars transfer and surface habitat vehicle incurs about a 25 % mass penalty compared to a linear‑stack point design.

Abstract

Modular space exploration systems have been built in the past and they exist today. Most of these systems, starting with Apollo and Soyuz, assign high level functions to various physical spacecraft modules and assemble these in a linear stack. The predominant building block for such systems is the cylinder. Unfortunately, this configuration is inflexible and does not promote reuse of modules over a broad range of missions. We argue that future space exploration systems should be reconfigurable and therefore require additional docking ports, reconfiguration options and improved structural and volumetric efficiency. A survey of the modular spacecraft literature and our own analysis reveal that the truncated octahedron emerges as the most promising polyhedron-based spacecraft geometry for future application to space exploration. This argument is supported by comparison of various spacecraft geometries with four metrics: volumetric efficiency, launch stowage and packing efficiency, reconfigurability, and stability. In addition, extensible spacecraft design is enabled by this design concept. This is shown in a preliminary design of manned exploration vehicles based on the truncated octahedron concept in which a mass penalty in designing a modular version of a Mars transfer and surface habitat vehicle compared to a “point design,” linear stack concept, was found to be approximately 25%.