In 1956 Crocco, more than 80 years old, produced what is considered his most important contribution to world astronautics: in his “One-Year Exploration-Trip Earth-Mars-Venus-Earth” paper presented at the Seventh Congress of the International Astronautical Federation IAF, Rome, in 1956, he suggested exploiting the Mars and Venus gravitational fields as propelling forces to cut dramatically the travelling time of a space capsule. This ‘gravitational slingshot’ or ‘gravity assist’ or ‘swing-by’ method was such that the NASA recommended the study of his theories and especially his swing-by maneuvers contracting firms working on interplanetary flight and its perspectives.