The International Astronautical Federation is the only professional society in the field of aerospace engineering and Sciences which brings together specialists of all countries interested in the exploration and peaceful exploitation of space. At its annual Congresses a large number of invited and/or carefully selected con­ tributed papers are presented which cover a wide variety of topics and are distributed over a number of sessions, each one being organized by two leading scientists who later chair the session itself. Each year the selection of specific topics to be dealt with. is dictated either by significant new progress achieved in some sectors or by new developments and