Evaluation of Materials for Venus Aerobot Applications

During the last 5 years JPL has examined a number of concepts 2 for robotically controlled balloons or aerobots. The Venus Geoscience Aerobot (VGA) concept uses reversible fluid altitude control to carry out repeated descents to the surface of Venus. This concept uses frozen water to keep the electronics cool. The balloon must periodically go to high altitude so that the water can be refrozen. Balloon materials would be required to withstand the rigors of the Venus atmosphere, including passes through sulfuric acid clouds and survival at temperatures up to 460 oC. Polybenzoxazole (PBO) and polyimidobenzoxazole (PIBO), materials developed by Dow Chemical Corporation, appear very promising. For example, weight loss measurements of PBO and PIBO films have been made with less than 2-percent weight loss observed over a 4-hour period at 460 oC, and mechanical properties appear persistent up to high temperatures, although the high temperature limits have not been determined.