1624. Computer-Aided Controllability Assessment of Generic Manned Space Station Concepts

Paper

Abstract

The goal of the NASA space station program is to provide a system of permanent orbiting manned and unmanned elements capable of performing a variety of scientific, commercial and operations missions. The program begins with an initial operational capability (IOC) in 1992 that provides the foundation and
necessary interface provisions to permit a continuing increase in evolutionary capability throughout the decade of the 1990’s. The prime element of the space station program is a permanently habitable facility in low- Earth orbit(LEO) which is capable of being resupplied by the Space Shuttle Orbiter. Initial conceptual studies of permanent habitable LEO space station concepts were performed by the Concept Development Group (CDG) of the NASA Space Station Task Force. The studies considered a broad range of generic concepts for the purpose of assessing configuration geometries with respect to cost, on-orbit assemblability, growth, controllability and mission payload accommodation. Mission accommodation considerations also included provisions for servicing unmanned platforms and free-flying spacecraft as well as provisions for construction of large space structures (Ref. 1).
Although a specific configuration is still yet to be determined, for the CDG studies, the habitable space station was baselined to consist of resource modules with solar arrays; habitability modules for crew living accommodations; and multiple berthing adapters for adding on other modules. Mission equipment can include laboratory and operations modules, Orbital Maneuvering Vehicles, Orbital Transfer Vehicles (OTV), OTV hangars, arid large structural support assemblies to provide mounting of mission equipment. The CDG configurations were categorized into several basic generic classifications depending on architecture, payload accommodation, and orbital flight orientation. The baseline configuration for these studies was chosen to be the CDG-1 axial- radial concept flying in an Earth-oriented attitude shown in Figure 1. A typical arrangement of the various modules for initial and growth station concepts is also depicted in Figure 1.
This paper reports on the task of assessing the on-orbit rigid- body controllability characteristics of each generic configuration proposed for study. The methodology utilized and preliminary results presented provide a ‘first cut’ analysis of these Initial concept considerations. Detailed in-house NASA configuration studies are still on-going and are planned to continue throughout the Phase B Design Definition activity which is scheduled for completion in September 1986.
Rigid-Body Control Dynamics methodology was used to evaluate the salient controllability characteristics and resource requirements for eight different habitable space station configurations. Analytical computer models of each configuration were developed using the Interactive Design and Evaluation of Advanced Spacecraft (IDEAS) computer-aided design system (Ref. 2). The IDEAS system capability provided the necessary tools to perform the controllability study tasks. The initial task required the creation of three-dimensional geometry models of each configuration normalized to the CDG functional module definition to establish dimensional requirements for module connectivity, payload accommodation, and Orbiter, OTV, and OMV berthing clearances. Configuration models were generated from each geometry model to determine the mass, center-of-gravity, Inertias and aerodynamic drag areas of each concept. These data were used along with mission requirements to assess and size the momentum storage system and propellant requirements for attitude control, orbit maintenance, and momentum storage system desaturation.
Also, an investigation to determine the preferred flight attitude of each station configuration was performed. This preferred flight attitude is an orientation in which the normal to the solar array plane has the smallest deviation from the incoming solar flux as well as providing tradeoff evaluation criteria to assess resources for controlling peak cyclic environmental torques as a function of momentum desaturation requirements.