1374. Deployable and Erectable Concepts for Large Spacecraft

Paper

Abstract

Computerized structural sizing techniques are used to determine structural proportions of minimum mass tetrahedral truss platforms designed for low earth and geosynchronous orbit. Optimum (minimum mass) deployable and erectable, hexagonal shaped spacecraft are sized to satisfy multiple design requirements and constraints. Features integrated into the sizing procedure include design for: 1) packaging constraints imposed by Space Shuttle limits, 2) fundamental vibration frequencies of the platform and struts, 3) strut axial stiffness reduction due to curvature and/or taper, 4) strut buckling due to design loads such as gravity gradient control, orbital transfer, or assembly, and 5) geometric constraints on strut thickness, diameter and length. Strut dimensions characterizing minimum mass designs are found to be significantly more slender than those conventionally used for structural applications. Comparison studies show that mass characteristics of deployable and erectable platforms are approximately equal and that the Shuttle flights required by deployable trusses become excessive above certain critical stiffness values. Recent investigations of erectable strut assembly are reviewed. Initial erectable structure assembly experiments show that a pair of astronauts can achieve EVA assembly times of 2-5 min/strut and studies indicate that an automated assembler can achieve times of less than 1 min/strut for around the clock operation.