Stratospheric balloons constitute an original mean of atmospheric observations able to fly between 12 km and 45 km. Thanks to their lower cost and less drastic condition of use, they are a useful complement to astronomy and Earth observations with satellites. They can also constitute a solution to calibrate the satellite measurements or validate instruments for future space applications.

Stratospheric balloons are currently used for scientific missions. In order to meet the requests expressed by the scientific community, the French Space Agency (CNES) has developed different types of balloons [1]. Each balloon family has its own mission specificities, which means different requirements for balloon envelope properties. However, the specific environmental conditions encountered in the stratosphere result in the need for specific selection. For example, balloons can be exposed from one day to several months to stratospheric environment, from 20 km to 36 km.

A good understanding of balloon envelope materials is therefore essential to ensure the success of future missions. For this purpose, CNES and ONERA have developed a panel of relevant tests in order to estimate the evolution of these functional properties during their whole mission [2]. They allow to study the different materials constituting the envelopes of the stratospheric balloons, to qualify them in their initial state and estimate their future evolution during their missions.

This presentation shows the study and results obtained on different polymer films currently used for making balloons. Particularly, thermo-optical, mechanical and gas permeability properties are investigated, at several temperatures (ambient and low temperatures, down to -100 °C). Solutions for improving properties, in particular helium permeability properties, are presented.

[1] Sadourny, I., Advances in Space Research; vol 30.5 (2002) 1105-1110.
[2] Guigue-Joguet, P., Siguier, J.M., European Rocket and Balloon Programmes and Related Research 471 (2001) 547-552.