DEPLOYMENT SIMULATION OF ULTRA-LIGHTWEIGHT INFLATABLE STRUCTURES Abstract.pdfVIP

1 DEPLOYMENT SIMULATION OF ULTRA-LIGHTWEIGHT INFLATABLE STRUCTURES John T. Wang* and Arthur R. Johnson? NASA Langley Research Center Hampton, VA Abstract Dynamic deployment analyses of folded inflatable tubes are conducted to investigate modeling issues related to the deployment of solar sail booms. The analyses are necessary because ground tests include gravity effects and may poorly represent deployment in space. A control volume approach, available in the LS-DYNA nonlinear dynamic finite element code, and the ideal gas law are used to simulate the dynamic inflation deployment process. Three deployment issues are investigated for a tube packaged in a Z-fold configuration. The issues are the effect of the rate of inflation, the effect of residual air, and the effect of gravity. The results of the deployment analyses reveal that the time and amount of inflation gas required to achieve a full deployment are related to these issues. Introduction Ultra-Lightweight Inflatable (ULI) space structures have become attractive because they can meet structural requirements for space applications at a low cost. These thin membrane structures can be fabricated and deployed for millions of dollars less than conventional structures. The roles envisioned for inflatable structures include solar sails, space telescope sunshades, solar arrays, pressurized habitats in space, antenna reflectors, and optical telescope mirrors. Solar sails capture the momentum of sunlight photons. The area density of the available momentum is small. As a result, solar sails must be large. The thrust provided by these large sails is so small that the sails must also be thinner than paper to produce useful thrust vectors on the spacecraft. Billowing solar sails are less effective than flat solar sails due to the reduced momentum exchange provided by oblique incidence photons. To keep billowing within allowable limits, membrane tensi