The science and technology of space flight. Astronautics is the theory and practice of travel beyond Earth’s atmosphere into outer space. It is the science of the construction and operation of vehicles for travel in space beyond the earth’s atmosphere. Spaceflight is one of its main applications and space science its overarching field.
The term astronautics was coined in the 1920s by J.-H. Rosny, president of the Goncourt academy. At this time, Robert H. Goddard was developing liquid-propellant rockets, which would in a few brief decades become a critical component in the designs of such famous rockets as the V-2 and Saturn V.
Watch this video. Difference Between Aeronautical & Aerospace Engineering