The application of geometric and materially non-linear finite element analysis techniques to the NASA Super Pressure Balloon Project has been driven by the need to understand and overcome deployment and stability problems that have shadowed the chosen 'pumpkin' design. Early iterations of the super pressure balloon designs showed problems of shape instability, characterized by improper deployment and the potential for overall geometric instability once deployed. Deployment instability was better understood following a series of large-scale hangar tests simulating launch and ascent, and has subsequently been captured numerically using Abaqus by team members at Caltech. Deployment instability has been reproduced numerically using inTENS . In both cases the solution lies in minimizing the film lobing between the tendons. As the development and test project proceeds the analysis effort has additionally focused on more detailed aspects. For example, the behavior of the balloon under the combination of low temperature and pressure as it reaches float and begins to pressurize needs careful investigation because of high film stresses local to the end fittings. This necessitates including the effects of seams, tendon sleeves and taped reinforcement in the model. This paper covers a number of detail analysis studies as well as documenting the current analysis strategy.
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