The theory and practice of navigation through air or space; SYN. astronautics.
Science of travel through the Earth's atmosphere, including aerodynamics, aircraft structures, jet and rocket propulsion, and aerial navigation.
In subsonic aeronautics (below the speed of sound), aerodynamic forces increase at the rate of the square of the speed.
Transsonic aeronautics covers the speed range from just below to just above the speed of sound and is crucial to aircraft design. Ordinary sound waves move at about 1,225 kph/760 mph at sea level, and air in front of an aircraft moving slower than this is “warned” by the waves so that it can move aside. However, as the flying speed approaches that of the sound waves, the warning is too late for the air to escape, and the aircraft pushes the air aside, creating shock waves, which absorb much power and create design problems. On the ground the shock waves give rise to a sonic boom. It was once thought that the speed of sound was a speed limit to aircraft, and the term sound barrier came into use.
Supersonic aeronautics concerns speeds above that of sound and in one sense may be considered a much older study than aeronautics itself, since the study of the flight of bullets, known as ballistics, was undertaken soon after the introduction of firearms. Hypersonics is the study of airflows and forces at speeds above five times that of sound (Mach 5); for example, for guided missiles, space rockets, and advanced concepts such as HOTOL (horizontal takeoff and landing). For all flight speeds streamlining is necessary to reduce the effects of air resistance.
Aeronautics is distinguished from astronautics, which is the science of travel through space. Astronavigation (navigation by reference to the stars) is used in aircraft as well as in ships and is a part of aeronautics.

(Irregular plural: aircraft).
A vehicle that can fly. Any aeronautical vehicle, which may be lighter than air (supported by buoyancy) or heavier than air (supported by the dynamic action of air on its surfaces). Balloons and airships are lighter-than-air craft. Heavier-than-air craft include the airplane, glider, autogiro, and helicopter.

Or flight; People first took to the air in lighter-than-air craft such as balloons 1783 and began powered flight in 1852 in airships, but the history of aviation focuses on heavier-than-air craft called airplanes. Developed from glider design, with wings, a tail, and a fuselage, the first successful flight of a powered, heavier-than-air craft was in 1896 by S P Langley’s unmanned plane (Model No 5), for ¾ of a mile near the Potomac River; then, in 1903, the Wright brothers flew the first piloted plane at Kitty Hawk. In 1903, Glenn Curtiss publicized flight in the US and began the first flying school in 1909. A competition for the development of airplanes was inspired by a series of flights and air races in the US and Europe, and planes came into their own during World War I, being used by both sides. Biplanes were generally succeeded by monoplanes in the 1920s and 1930s, and they used runways or water (seaplanes and flying boats) for takeoffs and landings at airfields that soon became airports. In these decades airlines
were formed for international travel, airmail, and cargo. The first jet plane was produced in Germany in 1939, the Heinkel He-178, but conventional prop planes were used for most of the destruction and transport of World War II. The 1950s brought economical passenger air travel on turboprops and jet airliners, which by the 1970s flew transatlantic in about 6 hours. The Concorde, a supersonic jetliner, flies passengers over that route in about 3 hours.
The early development of aircraft took place in the US and Europe. In the US, after the Wright brothers' Kitty Hawk flight, Glenn Curtiss made publicity flights and founded a flight school 1909, then designed and developed 1911 planes with modern ailerons and stabilizers, for guidance control and stability; in France, Louis Blériot brought aviation much publicity by flying the Channel 1909; as did the Reims air races of that year. The flight experience of World War I (1914–18) and the subsequent rapid development of powerful gasoline engines led to planes that could maneuver at speeds of 200 mph/320 kph. Streamlining became imperative; the body, wings, and exposed parts were shaped to reduce drag and the biplane was mostly replaced by the internally braced monoplane structure. Probably the most successful plane of this type ever produced was the Douglas DC-3 and all its variants—with about 10,000 built, used for passengers and cargo in the 1930s and war duty in World War II—about 3,000 are still in daily use.
Although by the 1930s planes had acquired the range for long distance flights needed in cargo, mail, and passenger service, by the 1940s new design concepts were developed especially for warplanes that later became important to peacetime aviation, such as the jet engine.
The first flight of a jet-powered aircraft was the German Heinkel He-178 in 1939, and German jets were in use during World War II by 1943; British jet fighters went into action during the last year of the war.
Turboprop planes were also developed by the end of the war, and became very successful in commercial service during the interim years between propeller and jet service; in the 1960s turboprops found new operational life when they were needed for fuel economy in flying heavy loads over the short distances into small airports with difficult terrain, as in the third world. Jet airliners such as the Comet were introduced in the 1950s. The late 1960s introduced jumbo jets and the supersonic airliner, notably the Anglo-French Concorde; the former brought economical air travel and the latter a transatlantic crossing of under 3 hours with ideal conditions. Today, jet planes dominate both civilian and military aviation, although many light planes —for sport and business—use piston engines and propellers. Clubs now restore old and antique planes, which are flown in demonstrations, displayed and flown in airshows, and donated to museums. Prop planes still see use in agricultural crop dusting, in bush piloting (especiall
y in Alaska), and for sky writing.
The aggregation of a country's military aircraft; SYN. air power.