Recent Progress in Materials Selection and Characterizations for Ultra Long Duration Balloon (ULDB) Missions

The development and characterization of materials suitable for ultra long duration balloon flights has recently been the focus of the materials R&D efforts for the NASA balloon program. Although basic materials selection criteria is similar to those used for conventional balloon missions, additional considerations related to balloon design, fabrication, durability, environmental effects, and cost must also be considered. Among these, the highest impact on material selection is, related to the design shape of the balloon. Work done by independent researchers indicate that for pumpkin type balloons, the load-carrying member is the tendon rather than the structural envelope. This in turn lowers the strength requirements on the envelope material to a large extent. Several materials and material combinations were explored for both design systems. This paper will present the progress made to date in the selection and characterization of these materials and the technical challenges remaining to be overcome,