Simulation of Deployment Dynamics of Inflatable Structures

Abstract

Analytical simulation of the ine ation process of ine atable structures is key to assessing their robust deployment in a space environment. Although the problem seems to be intractable, a simplie ed e nite volume ine ation model is developed, which allows discretized description of the gas e ow, pressure variation, and resulting nonlinear large deformation throughout domains of the ine atable structure. Simulation results are presented along with convergence studies, which provide insight into the deployment of three different packaging/deployment schemes: Z-unfolding, rollout, and extrusion of a cylindrical tube. The proposed ine ation model is not limited to prismatic one-dimensional components and can be applied to ine atable shapes with complex cone gurations. As a validation of the numerical simulation, a laboratory experiment was conducted on the Z-folded cone guration. Generally, good agreement in the overall ine ation dynamics is observed between the analysis and experiment. EVERALspacemissionshaveconsideredtheuseoflightweight ine atable structures for components such as booms, sunshades, solar concentrators, solar sails, and antennas for nearly all aspects of Earth and space explorations. As a prelude to these missions, the ine atable antenna experiment (IAE) was deployed from the Space Shuttle Endeavour in May 1996 to demonstrate the readiness and reliabilityoftheine atabletechnologyforalarge14-mantennastructure in a realistic space environment. 1 One of the urgent technology issues revealed by the brief 80-min IAE e ight experiment was the need to better understand the dynamics of deploying ine atable structuresinspaceandhowthe ine ationprocessisine uenced by the deployment scheme. This includes the initial packaging and subsequent release and ine ation. Depending on the deployment scheme, large ine atable structures can be extremely e exible to the point of instability, especially during the early stages of ine ation. Rigidization can begin only after e nal deployment is achieved. Testing the deploymentof alargeine atableinan Earth environmentin the presence of gravity and air is of limited value for inferring its deploymentbehavior in space. Therefore, analytical models for simulating and predicting the dynamics of the ine ation process are essential tools for understanding ine atables’ deployment behavior in space environment and for guiding and improving future packaging and deployment concepts. To thisend,this paper explores theuse ofa e nite volume ine ation model that allows a tractable simulation of the deployment process of various ine atable cone gurations, from their initial stowed state to full deployment. Of interest here is a description of all states of ine ation as a function of time. Knowledge of all states of ine ation is essential for subsequent assessment of conditions of stability and controllability of the deployment process.