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MODELING THE COMPLETED SPACE STATION A THREE DIMENSIONAL RIGID-FLEXIBLE DYNAMIC MODEL TO PREDICT MODES OF VIBRATION AND STRESS ANALYSIS

The use of computer models to predict the dynamic behavior of the Space Vehicles is used to understand the natural frequencies, dynamic system responses of complex rigid-flexible multibody system such as the International Space Station (ISS). One of the major problems in assembling the ISS is simulating dynamics and control analysis in orbit. This problem is a challenge that confronts the ISS program and thus computer modeling and simulation becomes a crucial tool for the success of space missions since the Station is being built in Space instead of a lab on earth where dynamic tests could be run. Each new mission of the Space Shuttle is designed to build the ISS and each new mission presents new challenges because the structure changes and thus the model has to change. In this paper, the authors present a model of the ISS assembled after the Space Shuttle STS-133 mission. The objective is that this model can be used to understand the modes of vibration and to design a control system capable of controlling ISS attitude. Once the computer model was assembled in a way that resembles the actual ISS assembly, model data were compared with NASA’s data. This paper proposes an alternative method for producing a new generation of three dimensional simplified computer models while still preserving significant dynamics information. In order to achieve this, the authors used components created in three dimensions via solid modeling and then transformed them into time dependent dynamic finite element models. The idea here is to have a model consisting of rigid-flexible multi-body systems, as this is what ISS is. Such process and results are presented here step by step using a technique that mixes solid modeling and dynamic finite element modeling. Software packages such as SOLIDWORKS, MSC VISUAL NASTRAN4D, MATLAB and SIMULINK were incorporated in the process. The computer model results can provide aerospace engineers with new alternative methods to perform dynamic analysis to study forces, deflections, vibrations, and position of spacecraft. The alternative method can provide aerospace engineers with new simplified methods to quickly get a handle of the forces, deflections, modes of vibration and prediction of dynamic loads during space maneuvers and ultimately crucial information to be used in guidance and control.