1371. Modular Space Structures

Paper

Abstract

Projected space systems are demanding increasingly large, supportive structural systems. The piece-by-piece assembly methods common in terrestrial construction projects cannot be economically practiced in the space environment.
Structures that can be assembled before launch, mechanically folded into a compact package, and then unfolded (deployed) in space to their original size and configuration offer significant advantages, including reduced orbital time, effort, risk, and cost.
The maximum size achievable by a purely deployable structural concept is limited, however, primarily by available launch vehicle stowage space. For space construction projects whose sizes exceed the capability of the ‘deploy from Orbiter’ approach, a feasible concept development is to combine the techniques of space deployment and space erection (assembly) by independently deploying two or more structural ‘modules,’ then joining them.
The Extendable Tetrahedral Truss (ETT) is a deployable structural concept that has considerable potential for this approach. As a basic structural concept, it derives high structural efficiency and stiffness from the three-dimensional triangulation of its geometry. Its uniformly distributed pattern of structural hard points (node fittings) provides for effective module-to-module joining. Its high-density packageability leads to highly efficient use of the Orbiter payload volume.
Of the several optional approaches to ETT modularization, side-by-side joining of minimum-section ‘beam’ truss structures offers certain advantages. Such beams are capable of controlled, incremental (bay-by-bay) deployment, and have been developed to the advanced hardware stage. When deployed, they offer flat, planar interfaces for joining.
A 100-meter hexagonal space platform can be assembled by joining 48 such beams, which, together with the necessary support equipment, would represent two Orbiter payloads.