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Fluid-Structure Projects for Reentry Vehicles made of Inflatable Structures

Coupled fluid-structure interaction studies of two configurations of inflatable decelerators (balloon-parachute, ballute) were performed. A novel and test-validated method for mapping loads and displacements were employed to transfer data between the fluids and structural models such that the errors in the data transfer remained below 1.0%. The first study was conducted on a gossamer-like trailing toroidal inflatable decelerator (major diameter of 48 m, minor diameter of 6 m, 5 mil membrane), and attempts were made to include the influence of the shocks emanating from an attached reentry vehicle. This study was followed by a detailed verification using a second set of computational fluid dynamic and finite element software. Several areas examined in this study could be viewed as potential contributors to the overall accuracy of results. The second study was conducted on a scaled wind tunnel test article tested at a Mach 6 condition. The test article represented an attached inflatable decelerator. The purpose of the second study was to validate the analysis methodology for the trailing toroidal inflatable decelerator. The requirements for the second study were relaxed to not only achieve quicker solution cycles, but to examine the accuracy of analysis versus computational time. All studies used a coupled fluid-structure interaction procedure, and this procedure was proven to be accurate enough to produce a maximum displacement that was within 6.7% of that observed from the wind tunnel test data. The future work consists of validations of the methodology using a series of subsonic and supersonic ground and flight tests.