Unmanned aerial vehicles (UAVs) include both autonomous (capable of operating without human input) drones and remotely piloted vehicles (RPVs). A UAV is capable of controlled, sustained level flight and is powered by a jet, reciprocating, or electric engine. In the twenty-first century, technology reached a point of sophistication that the UAV is now being given a greatly expanded role in many areas of aviation.
A UAV differs from a cruise missile in that a UAV is intended to be recovered after its mission, while a cruise missile impacts its target. A military UAV may carry and fire munitions on board, while a cruise missile is a munition. Loitering munitions are a class of unmanned aircraft intermediate between them.
Early development
Austrian incendiary balloon attack on Venice The earliest recorded use of an unmanned aerial vehicle for warfighting occurred in July 1849,Air Power in the Age of Total War, John BuckleyThe Future of Drone Use: Opportunities and Threats from Ethical and Legal Perspectives, Asser Press - Springer, chapter by Alan McKenna, page 355 serving as a balloon carrier (the precursor to the aircraft carrier)Naval Aviation in the Second World War, Philip Kaplan is the first offensive use of air power in naval aviation. Taking Flight: Inventing the Aerial Age, from Antiquity through the First World War, Richard P. Hallion, page 66 Naval Aviation in the First World War: Its Impact and Influence, R. D. Layman, page 56Broken Wings: The Hungarian Air Force, 1918-45, Stephen L. Renner, page 2 Austrian forces besieging Venice attempted to float some 200 incendiary balloons each carrying a 24- to 30-pound bomb that was to be dropped from the balloon with a time fuse over the besieged city. The balloons were launched mainly from land; however, some were also launched from the Austrian ship SMS Vulcano. The Austrians used smaller pilot balloons to determine the correct fuse settings. At least one bomb fell in the city; however, due to the wind changing after launch, most of the balloons missed their target, and some drifted back over Austrian lines and the launching ship Vulcano.Military Aircraft, Origins to 1918: An Illustrated History of Their Impact, Justin D. Murphy, page 9-10 Military Ballooning During the Early Civil War, The Johns Hopkins University Press, F. Stansbury Haydon, page 18-20Mikesh, Robert C. "Japan's World War II balloon bomb attacks on North America." (1973).
World War I The first pilotless aircraft were built during World War I. From a suggestion that A. M. Low’s expertise in early television and radio technology be used to develop a remotely controlled pilotless aircraft to attack the Zeppelins"He Lit The Lamp" 1958 A Biography Of Professor A.M.Low Ursula Bloom"The Dawn of the Drone" Steve Mills 2019 Casemate Publishers. a remarkable succession of British drone weapons in 1917 and 1918 evolved. Designers from Sopwith Aviation and its contractor Rushton Proctor, de Havilland and the Royal Aircraft Factory all became involved. They were all designed to use Low's radio control system developed at the Royal Flying Corps secret Experimental Works at Feltham. Of these Low confirmed that Geoffrey de Havilland’s monoplane was the one that flew under control on 21 March 1917.Professor A. M. Low FLIGHT, 3 October 1952 page 436 "The First Guided Missile" Low is known as '"father of radio guidance systems" and in 1976 Low was inducted into the International Space Hall of Fame. Alternatively, John Taylor suggested Low was the ‘Father of the Remotely Piloted Vehicle’.Taylor, John W. R.. Jane's Pocket Book of Remotely Piloted Vehicles.
Soon after, on September 12, the Hewitt-Sperry Automatic Airplane, otherwise known as the "flying bomb" made its first flight, demonstrating the concept of an unmanned aircraft. They were intended for use as "aerial torpedoes," an early version of today's cruise missiles. Control was achieved using gyroscopes developed by Elmer Sperry of the Sperry Gyroscope Company.Pearson, Lee: Developing the Flying Bomb
Later, in November 1917, the Automatic Airplane was flown for representatives of the US Army. This led the army to commission a project to build an "aerial torpedo", resulting in the Kettering Bug which first flew in 1918. While the Bug's revolutionary technology was successful, it was not in time to fight in the war, which ended before it could be fully developed and deployed.
Interwar period
After World War I, three Standard E-1s were converted to drones.Donald, David, ed. Encyclopedia of World Aircraft (Etobicoke, Ontario: Prospero Books, 1997), p.854, "Standard aircraft". The Larynx was an early cruise missile in the form of a small monoplane aircraft that could be launched from a warship and flown under autopilot; the Royal Navy tested it between 1927 and 1929. The early successes of pilotless aircraft led to the development of radio controlled pilotless target-aircraft in Britain and the US in the 1930s. In 1931 the British developed the Fairey Queen radio-controlled target from the Fairey IIIF floatplane, building a small batch of three, and in 1935 followed up this experiment by producing larger numbers of another RC target, the "DH.82B Queen Bee", derived from the de Havilland Tiger Moth biplane trainer. The name of "Queen Bee" allegedly led to the use of the term "drone" for pilotless aircraft, particularly when they are radio-controlled. During this period, the U.S. Navy, continuing work that reached back to 1917, also experimented with radio-controlled aircraft. In 1936 the head of US Navy research group used the term "DRONE" to designate radio-controlled aerial targets. - "[...] the capital letters indicate that DRONE is a military code name" From 1929 Hungarian scientist Kálmán Tihanyi worked on television guidance for defense applications, building prototypes of a camera for remotely-guided aircraft in London for the British Air Ministry, and later adapting it for the Italian Navy. In 1929, Tihanyi invented the first infrared-sensitive (night-vision) electronic television-camera for anti-aircraft defense in Britain. The solutions of the technology that Tihanyi depicted in his 1929 patent became so influential that American UAV-producing companies still used many of its solutions even half a century later, until the mid-1980s.See the citations of the patent .
Subsequent British "drones" included the Airspeed Queen Wasp, the Miles Queen Martinet, and the US-supplied Curtiss Queen Seamew. After WW II these would be replaced by the jet-powered Anglo-Australian GAF Jindivik.
The Soviets tested pilotless munitions-delivery in 1935-1939.
World War II
Reginald Denny and the Radioplane The first large-scale production, purpose-built drone was the product of Reginald Denny. He served with the British Royal Flying Corps during World War I, and after the war, in 1919, he returned to the United States to resume his career in Hollywood. Denny was a successful leading man and between acting jobs, he pursued his interest in radio control model aircraft in the 1930s opening a shop.
The shop evolved into the "Radioplane Company". Denny believed that low-cost RC aircraft would be very useful for training anti-aircraft gunners, and in 1935 he demonstrated a prototype target drone, the RP-1, to the US Army. Denny then bought a design from Walter Righter in 1938 and began marketing it to hobbyists as the "Dennymite", and demonstrated it to the Army as the RP-2, and after modifications as the RP-3 and RP-4 in 1939. In 1940, Denny and his partners won an Army contract for their radio controlled RP-4, which became the Radioplane OQ-2. They manufactured nearly fifteen thousand drones for the Army during World War II.
The true inventor of a radio-controlled aircraft that could fly out of sight was Edward M. Sorensen as evidenced by his US patents. His invention was the first to be able to know from a ground terminal what the airplane was doing, such as climbing, altitude, banking, direction, rpm and other instrumentation. Without these patents the early radio-controlled aircraft could only operate within visual sight of the ground pilot.US Patent 2,490,844 filed in May of 1940; Patent 2,408,819 filed May 16, 1940 and patent 2,482,804 filed May 16, 1940
Aerial torpedoes
The US Navy began experimenting with radio-controlled aircraft during the 1930s as well, resulting in the Curtiss N2C-2 drone in 1937. The N2C-2 was remotely controlled from another aircraft, called a TG-2. N2C-2 anti-aircraft target drones were in service by 1938.Fahrney, Delmar S., RADM USN "The Birth of Guided Missiles" United States Naval Institute Proceedings December 1980 pp.54–60
The US Army Air Forces (USAAF) adopted the N2C-2 concept in 1939. Obsolescent aircraft were put into service as "A-series" anti-aircraft target drones. Since the "A" code would be also used for "Attack" aircraft, later "full-sized" targets would be given the "PQ" designation. USAAF acquired hundreds of Culver "PQ-8" target drones, which were radio-controlled versions of the Culver Cadet two-seat light civil aircraft, and thousands of the improved Culver PQ-14 Cadet derivative of the PQ-8. The US also used RC aircraft, including modified B-17 Flying Fortress and B-24 Liberator heavy bombers in Aphrodite and Anvil operations in combat on a small scale during World War II as very large aerial torpedoes, though with no great success and the loss of aircrew including Joseph P. Kennedy Jr.
The "TDN-1" was an unmanned aerial vehicle that was developed for use in 1940. The TDN was capable of delivering a 1,000-pound bomb but never saw operational duty.
The Naval Aircraft Factory assault drone "Project Fox" installed an RCA television camera in the drone and a six-inch television screen in the TG-2 control aircraft in 1941. In April 1942 the assault drone successfully delivered a demonstration torpedo attack on a US destroyer at a range of 20 miles from the TG-2 control aircraft. Another assault drone was successfully crashed into a target moving at eight knots. The Navy Bureau of Aeronautics then proposed a television-assisted remote control assault drone program of 162 control planes and 1,000 assault drones. Disagreements arose within the Navy concerning the relative advantages of the proposed program for full-scale combat implementation versus a small-scale combat test with minimum aircraft resource expenditure which might reveal the concept to the enemy and allow development of countermeasures prior to full production. Assault drones remained an unproven concept in the minds of military planners through major allied advances of 1944. Utilization was limited to a 4-drone attack on a beached Japanese merchant ship in the Russell Islands at the end of July followed by expenditure of 46 drones in the northern Solomon Islands. Two hits and two near-misses were scored on the stationary ship. Several of the later drones failed to reach their targets, but most were effective.
Pulsejets
The V-1 flying bomb was the first cruise missile ever built. It was built in the Peenemünde Army Research Center and first tested in 1942. The V-1 was intended to target London and was massively fired, achieving more than one hundred launches a day. The V-1 was launched from a rail system to achieve the speed needed to operate its pulsejet engine and would achieve a 250 kilometers radius, at one point flying at 640 km/h.
McDonnell built a pulsejet-powered target, the TD2D-1 Katydid, later the KDD-1 and then KDH-1. It was an air-launched cigar-shaped machine with a straight mid-mounted wing, and a vee tail straddling the pulsejet engine. The Katydid was developed in mid-war and a small number were put into service with the US Navy.