Research and development are permanent concerns in the French Balloon activity. One of the most significant improvements took place in the mid 80's in the field of materials, where linear low density polyethylenes demonstrated outstanding qualities at very low temperature, and allowed balloons to renew with success after the gap of the years 1985-1986. Successfull flights have since then been achieved under very cold temperatures, either in tropical or artic zones, with very large and heavily loaded balloons. Significant steps have equally been achieved in balloon design, thanks to a new approach using the finite elements method. Because of its versality, this method allows a very precise design of any shaped enveloppe (spherical, cylindrical, natural or else) with any type of appendix (belt, polar load, sleeve or else).