Northrop Grumman Bat UAV in flight in June 2014

An unmanned aerial vehicle (UAV), commonly known as a drone, is an

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. ...

without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controller and a system of communications with the UAV. The flight of UAVs may operate under remote control by a human operator, as remotely-piloted aircraft (RPA), or with various degrees of autonomy, such as

autopilot An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator' ...

assistance, up to fully autonomous aircraft that have no provision for human intervention. UAVs were originally developed through the twentieth century for military missions too "dull, dirty or dangerous" for humans, and by the twenty-first, they had become essential assets to most militaries. As control technologies improved and costs fell, their use expanded to many non-military applications.Hu, J.; Bhowmick, P.; Jang, I.; Arvin, F.; Lanzon, A.,
A Decentralized Cluster Formation Containment Framework for Multirobot Systems
IEEE Transactions on Robotics, 2021. These include forest fire monitoring,Hu, J.; Niu, H.; Carrasco, J.; Lennox, B.; Arvin, F.,
Fault-tolerant cooperative navigation of networked UAV swarms for forest fire monitoring
Aerospace Science and Technology, 2022. aerial photography, product deliveries,

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled peop ...

, policing and surveillance, infrastructure inspections, entertainment, science, smuggling, and drone racing.

Terminology

Many terms are used for aircraft which fly without any persons on board: The term drone has been used from the early days of aviation, being applied to remotely-flown target

used for practice firing of a battleship's guns, such as the 1920s Fairey Queen and 1930s de Havilland Queen Bee. Later examples included the Airspeed Queen Wasp and Miles Queen Martinet, before ultimate replacement by the GAF Jindivik. The term remains in common use. In addition to the software, autonomous drones also employ a host of advanced technologies that allow them to carry out their missions without human intervention, such as cloud computing, computer vision, artificial intelligence, machine learning, deep learning, and thermal sensors. For recreational uses, an aerial photography drone (as opposed to a UAV) is an aircraft that has first-person video, autonomous capabilities, or both. An unmanned aerial vehicle (UAV) is defined as a "powered, aerial vehicle that does not carry a human operator, uses aerodynamic forces to provide vehicle lift, can fly autonomously or be piloted remotely, can be expendable or recoverable, and can carry a lethal or nonlethal payload". UAV is a term that is commonly applied to military use cases. However

missile In military terminology, a missile is a missile guidance, guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously ...

s with warheads are not considered UAVs because the vehicle itself is a munition. Also, the relation of UAVs to remote controlled model aircraft is unclear, UAVs may or may not include remote-controlled model aircraft. Some jurisdictions base their definition on size or weight; however, the US FAA defines any uncrewed flying craft as a UAV regardless of size. The term ''unmanned aircraft system'' (UAS) was adopted by the

United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secur ...

(DoD) and the United States

Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...

(FAA) in 2005 according to their Unmanned Aircraft System Roadmap 2005–2030. The

International Civil Aviation Organization The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international ...

(ICAO) and the British Civil Aviation Authority adopted this term, also used in the European Union's Single-European-Sky (SES) Air-Traffic-Management (ATM) Research (SESAR Joint Undertaking) roadmap for 2020. This term emphasizes the importance of elements other than the aircraft. It includes elements such as ground control stations, data links and other support equipment. A similar term is an ''unmanned-aircraft vehicle system'' (UAVS), ''remotely piloted aerial vehicle'' (RPAV), ''remotely piloted aircraft system'' (RPAS). Many similar terms are in use. "Unoccupied" and "uninhabited" are occasionally used as alternatives to "unmanned". Under new regulations which came into effect 1 June 2019, the term RPAS (Remotely Piloted Aircraft System) has been adopted by the Canadian Government to mean "a set of configurable elements consisting of a remotely piloted aircraft, its control station, the command and control links and any other system elements required during flight operation".

Classification types

UAVs may be classified like any other

, according to design configuration such as weight or engine type, maximum flight altitude, degree of operational autonomy, operational role, etc. According to the

, UAVs are classified into five categories below: Other classifications of UAVs include:

Range and endurance

There are usually five categories when UAVs are classified by range and endurance:

Size

There are usually four categories when UAVs are classified by size, with at least one of the dimensions (length or wingspan) meet the following respective limits:

Weight

Based on their weight, drones can be classified into 5 categories— ."Nano, micro, small: The different drone types in India & if Jammu-like strike can be averted"
'' ThePrint'', 29 June 2021.

Degree of autonomy

Drones could also be classified based on the degree of autonomy in their flight operations. ICAO classifies uncrewed aircraft as either remotely piloted aircraft or fully autonomous. Some UAVs offer intermediate degrees of autonomy. For example, a vehicle may be remotely piloted in most contexts but have an autonomous return-to-base operation. Some aircraft types may optionally fly manned or as UAVs, which may include manned aircraft transformed into uncrewed or Optionally Piloted UAVs (OPVs).

Altitude

Based on the altitude, the following UAV classifications have been used at industry events such as ParcAberporth Unmanned Systems forum: * Hand-held altitude, about 2 km range * Close altitude, up to 10 km range * NATO type altitude, up to 50 km range * Tactical altitude, about 160 km range * MALE (medium altitude, long endurance) up to and range over 200 km * HALE (high altitude, long endurance) over and indefinite range * Hypersonic high-speed, supersonic (Mach 1–5) or hypersonic (Mach 5+) or suborbital altitude, range over 200 km * Orbital low Earth orbit (Mach 25+) * CIS Lunar Earth-Moon transfer * Computer Assisted Carrier Guidance System (CACGS) for UAVs

Composite criteria

An example of classification based on the composite criteria is U.S. Military's

unmanned aerial systems An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controll ...

(UAS) classification of UAVs based on weight, maximum altitude and speed of the UAV component.

History

Early drones

The earliest recorded use of an unmanned aerial vehicle for warfighting occurred in July 1849, with a balloon carrier (the precursor to the aircraft carrier) in the first offensive use of air power in

naval aviation Naval aviation is the application of Military aviation, military air power by Navy, navies, whether from warships that embark aircraft, or land bases. Naval aviation is typically projected to a position nearer the target by way of an aircraft ...

. Naval Aviation in the First World War: Its Impact and Influence
R. D. Layman, page 56 Austrian forces besieging Venice attempted to launch some 200

incendiary balloon An incendiary balloon (or balloon bomb) is a balloon inflated with a lighter-than-air gas such as hot air, hydrogen, or helium, that has a bomb, incendiary device, or Molotov cocktail attached. The balloon is carried by the prevailing winds to ...

s at the besieged city. The balloons were launched mainly from land; however, some were also launched from the Austrian ship . 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''. The Spanish engineer Leonardo Torres y Quevedo introduced a radio-based control-system called the "''Telekino''" at the

Paris Academy of Science The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at ...

in 1903 with the intention of testing an

airship An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In early ...

of his own design without risking human lives. Significant development of drones started in the 1900s, and originally focused on providing practice targets for training military personnel. The earliest attempt at a powered UAV was A. M. Low's "Aerial Target" in 1916.Taylor, John W. R.. ''Jane's Pocket Book of Remotely Piloted Vehicles''. Low confirmed that Geoffrey de Havilland's monoplane was the one that flew under control on 21 March 1917 using his radio system. Following this successful demonstration in the spring of 1917 Low was transferred to develop aircraft controlled fast motor launches D.C.B.s with the Royal Navy in 1918 intended to attack shipping and port installations and he also assisted Wing Commander Brock in preparations for the Zeebrugge Raid. Other British unmanned developments followed, leading to the fleet of over 400 de Havilland 82 Queen Bee aerial targets that went into service in 1935.

Nikola Tesla Nikola Tesla ( ; ,"Tesla"
'' These developments also inspired the construction of the Kettering Bug by Charles Kettering from

Dayton, Ohio Dayton () is the sixth-largest city in the U.S. state of Ohio and the county seat of Montgomery County. A small part of the city extends into Greene County. The 2020 U.S. census estimate put the city population at 137,644, while Greater ...

and the Hewitt-Sperry Automatic Airplane – initially meant as an uncrewed plane that would carry an explosive payload to a predetermined target. Development continued during World War I, when the Dayton-Wright Airplane Company invented a pilotless aerial torpedo that would explode at a preset time. The film star and model-airplane enthusiast Reginald Denny developed the first scaled remote piloted vehicle in 1935. Soviet researchers experimented with controlling Tupolev TB-1 bombers remotely in the late 1930s.

World War II

In 1940 Denny started the Radioplane Company and more models emerged during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

used both to train antiaircraft gunners and to fly attack-missions.

Nazi Germany Nazi Germany (lit. "National Socialist State"), ' (lit. "Nazi State") for short; also ' (lit. "National Socialist Germany") (officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945) was ...

produced and used various UAV aircraft during the war, like the Argus As 292 and the V-1 flying bomb with a

jet engine A jet engine is a type of reaction engine discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include Rocket engine, rocket, Pump-jet, water jet, and ...

Postwar period

After World War II development continued in vehicles such as the American JB-4 (using television/radio-command guidance), the Australian GAF Jindivik and Teledyne Ryan Firebee I of 1951, while companies like

Beechcraft Beechcraft is an American brand of civil aviation and military aircraft owned by Textron Aviation since 2014, headquartered in Wichita, Kansas. Originally, it was a brand of Beech Aircraft Corporation, an American manufacturer of general avi ...

offered their Model 1001 for the U.S. Navy in 1955. Nevertheless, they were little more than remote-controlled airplanes until the

Vietnam War The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...

. In 1959 the U.S. Air Force, concerned about losing pilots over hostile territory, began planning for the use of uncrewed aircraft. Planning intensified after the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

shot down a U-2 in 1960. Within days, a highly-

classified Classified may refer to: General *Classified information, material that a government body deems to be sensitive *Classified advertising or "classifieds" Music *Classified (rapper) (born 1977), Canadian rapper *The Classified, a 1980s American roc ...

UAV program started under the code name of "Red Wagon". The August 1964 clash in the Tonkin Gulf between naval units of the U.S. and the North Vietnamese Navy initiated America's highly-classified UAVs ( Ryan Model 147, Ryan AQM-91 Firefly, Lockheed D-21) into their first combat missions of the

. When the Chinese government showed photographs of downed U.S. UAVs via ''Wide World Photos'', the official U.S. response was "no comment". During the War of Attrition (1967–1970) in the Middle East, Israeli intelligence tested the first tactical UAVs installed with

reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain, and other activities. Examples of reconnaissance include patrolling by troops ( skirmishe ...

cameras, which successfully returned photos from across the Suez Canal. This was the first time that tactical UAVs that could be launched and landed on any short runway (unlike the heavier jet-based UAVs) were developed and tested in battle. In the 1973 Yom Kippur War,

Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...

used UAVs as decoys to spur opposing forces into wasting expensive anti-aircraft missiles. After the 1973 Yom Kippur war, a few key people from the team that developed this early UAV joined a small startup company that aimed to develop UAVs into a commercial product, eventually purchased by Tadiran and leading to the development of the first Israeli UAV. In 1973 the U.S. military officially confirmed that they had been using UAVs in Southeast Asia (Vietnam). Over 5,000 U.S. airmen had been killed and over 1,000 more were

missing Missing or The Missing may refer to: Film *Missing (1918 film), ''Missing'' (1918 film), an American silent drama directed by James Young *Missing (1982 film), ''Missing'' (1982 film), an American historical drama directed by Costa-Gavras *Missi ...

or captured. The USAF

100th Strategic Reconnaissance Wing The 100th Air Refueling Wing (100th ARW), nicknamed ''the Bloody Hundredth'', is a United States Air Force unit assigned to the Third Air Force, United States Air Forces in Europe – Air Forces Africa. It is stationed at RAF Mildenhall, Suffolk ...

flew about 3,435 UAV missions during the war at a cost of about 554 UAVs lost to all causes. In the words of USAF

General A general officer is an officer of high rank in the armies, and in some nations' air forces, space forces, and marines or naval infantry. In some usages the term "general officer" refers to a rank above colonel."general, adj. and n.". O ...

George S. Brown George Scratchley Brown (17 August 1918 – 5 December 1978) was a United States Air Force general who served as the eighth chairman of the Joint Chiefs of Staff. In this capacity, he served as the senior military adviser to the president of th ...

, Commander, Air Force Systems Command, in 1972, "The only reason we need (UAVs) is that we don't want to needlessly expend the man in the cockpit." Later that year, General John C. Meyer, Commander in Chief, Strategic Air Command, stated, "we let the drone do the high-risk flying ... the loss rate is high, but we are willing to risk more of them ...they save lives!" During the 1973 Yom Kippur War, Soviet-supplied surface-to-air missile-batteries in

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Med ...

and Syria caused heavy damage to Israeli fighter jets. As a result, Israel developed the IAI Scout as the first UAV with real-time surveillance. The images and radar decoys provided by these UAVs helped Israel to completely neutralize the Syrian air defenses at the start of the 1982 Lebanon War, resulting in no pilots downed. In Israel in 1987, UAVs were first used as proof-of-concept of super-agility, post-stall controlled flight in combat-flight simulations that involved tailless, stealth-technology-based, three-dimensional thrust vectoring flight-control, and jet-steering.

Modern UAVs

With the maturing and miniaturization of applicable technologies in the 1980s and 1990s, interest in UAVs grew within the higher echelons of the U.S. military. In the 1990s, the U.S. DoD gave a contract to AAI Corporation along with Israeli company Malat. The U.S. Navy bought the AAI Pioneer UAV that AAI and Malat developed jointly. Many of these UAVs saw service in the 1991 Gulf War. UAVs demonstrated the possibility of cheaper, more capable fighting-machines, deployable without risk to aircrews. Initial generations primarily involved surveillance aircraft, but some carried armaments, such as the General Atomics MQ-1 Predator, that launched AGM-114 Hellfire air-to-ground missiles. CAPECON, a

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been ...

project to develop UAVs, ran from 1 May 2002 to 31 December 2005. the

United States Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army S ...

(USAF) employed 7,494 UAVs almost one in three USAF aircraft. The

Central Intelligence Agency The Central Intelligence Agency (CIA ), known informally as the Agency and historically as the Company, is a civilian intelligence agency, foreign intelligence service of the federal government of the United States, officially tasked with gat ...

also operated UAVs. By 2013 at least 50 countries used UAVs. China, Iran, Israel, Pakistan, Turkey, and others designed and built their own varieties. The use of drones has continued to increase.Sayler (2015) Due to their wide proliferation, no comprehensive list of UAV systems exists.Singer, Peter W
"A Revolution Once More: Unmanned Systems and the Middle East"

The Brookings Institution
November 2009.Franke, Ulrike Esther The global diffusion of unmanned aerial vehicles (UAVs) or 'drones'" in Mike Aaronson (ed) Precision Strike Warfare and International Intervention, Routledge 2015. The development of smart technologies and improved electrical-power systems led to a parallel increase in the use of drones for consumer and general aviation activities. As of 2021, quadcopter drones exemplify the widespread popularity of hobby

radio-controlled aircraft A radio-controlled aircraft (often called RC aircraft or RC plane) is a small flying machine that is controlled remotely by an operator on the ground using a hand-held radio transmitter. The transmitter continuously communicates with a receiver ...

and toys, however the use of UAVs in commercial and general aviation is limited by a lack of autonomy and by new regulatory environments which require line-of-sight contact with the pilot. In 2020 a Kargu 2 drone hunted down and attacked a human target in

Libya Libya (; ar, ليبيا, Lībiyā), officially the State of Libya ( ar, دولة ليبيا, Dawlat Lībiyā), is a country in the Maghreb region in North Africa. It is bordered by the Mediterranean Sea to the north, Egypt to the east, Su ...

, according to a report from the UN Security Council's Panel of Experts on Libya, published in March 2021. This may have been the first time an autonomous killer-robot armed with lethal weaponry attacked human beings. Superior drone technology, specifically the Bayraktar TB2, played a role in Azerbaijan's successes in the 2020 Nagorno-Karabakh war against Armenia. Dragonfly-landing

UAVs are also used in

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...

missions. The Dragonfly spacecraft is being developed, and is aiming to reach and examine Saturn's moon

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...

. Its primary goal is to roam around the surface, expanding the amount of area to be researched previously seen by

Lander Lander may refer to: Media and entertainment * Lander (computer game), ''Lander'' (computer game), computer game published by Psygnosis in 1999 * Lander (game demo), ''Lander'' (game demo), the 3D game demo provided with the Acorn Archimedes co ...

s. As a UAV, Dragonfly allows examination of potentially diverse types of soil. The drone is set to launch in 2027, and is estimated to take a seven more years to reach the Saturnian system.

Design

Crewed and uncrewed aircraft of the same type generally have recognizably similar physical components. The main exceptions are the cockpit and environmental control system or life support systems. Some UAVs carry payloads (such as a camera) that weigh considerably less than an adult human, and as a result, can be considerably smaller. Though they carry heavy payloads, weaponized military UAVs are lighter than their crewed counterparts with comparable armaments. Small civilian UAVs have no life-critical systems, and can thus be built out of lighter but less sturdy materials and shapes, and can use less robustly tested electronic control systems. For small UAVs, the quadcopter design has become popular, though this layout is rarely used for crewed aircraft. Miniaturization means that less-powerful propulsion technologies can be used that are not feasible for crewed aircraft, such as small electric motors and batteries. Control systems for UAVs are often different than crewed craft. For remote human control, a camera and video link almost always replace the cockpit windows; radio-transmitted digital commands replace physical cockpit controls.

Autopilot An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator' ...

software is used on both crewed and uncrewed aircraft, with varying feature sets.

Aircraft configuration

The primary difference from manned aeroplanes is the lack of need for a cockpit area and its windows. However some types are adapted from piloted examples, or are designed for optional piloted or unmanned operational modes. Air safety is also less of a critical requirement for unmanned aircraft, allowing the designer greater freedom to experiment. These two factors have led to a great variety of airframe and engine configurations in UAVs. For conventional flight the flying wing and blended wing body offer light weight combined with low

drag Drag or The Drag may refer to: Places * Drag, Norway, a village in Tysfjord municipality, Nordland, Norway * ''Drág'', the Hungarian name for Dragu Commune in Sălaj County, Romania * Drag (Austin, Texas), the portion of Guadalupe Street adj ...

and

stealth Stealth may refer to: Military *Stealth technology, technology used to conceal ships, aircraft, and missiles **Stealth aircraft, aircraft which use stealth technology **Stealth ground vehicle, ground vehicles which use stealth technology ** Stea ...

, and are popular configurations. Larger types which carry a variable payload are more likely to feature a distinct fuselage with a tail for stability, control and trim, although the wing configurations in use vary widely. For vertical flight, the tailless quadcopter requires a relatively simple control system and is common for smaller UAVs. However the mechanism does not scale well to larger aircraft, which tend to use a conventional single rotor with collective and cyclic pitch control, along with a stabilising tail rotor.

Propulsion

Traditional internal combustion and

s remain in use for drones requiring long range. However for shorter-range missions electric power has almost entirely taken over. The distance record for a UAV (built from balsa wood and mylar skin) across the North Atlantic Ocean is held by a gasoline model airplane or UAV. Manard Hill "in 2003 when one of his creations flew 1,882 miles across the Atlantic Ocean on less than a gallon of fuel" holds this record. Besides the traditional piston engine, the Wankel rotary engine is used by some drones. This type offers high power output for lower weight, with quieter and more vibration-free running. Claims have also been made for improved reliability and greater range. Small drones mostly use lithium-polymer batteries (Li-Po), while some larger vehicles have adopted the a

hydrogen fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen fuel, hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most bat ...

. The energy density of modern Li-Po batteries is far less than gasoline or hydrogen. However electric motors are cheaper, lighter and quieter. Complex multi-engine, multi-propeller installations are under development with the goal of improving aerodynamic and propulsive efficiency. For such complex power installations, Battery elimination circuitry (BEC) may be used to centralize power distribution and minimize heating, under the control of a microcontroller unit (MCU).

Ornithopters – wing propulsion

Flapping-wing ornithopters, imitating birds or insects, have been flown as microUAVs. Their inherent stealth recommends them for spy missions. Sub-1g microUAVs inspired by flies, albeit using a power tether, have been able to "land" on vertical surfaces. Other projects mimic the flight of beetles and other insects.

Computer control systems

AbuseMark AfroFlight Naze 32 Flight Controller rev5 white

UAV computing capability followed the advances of computing technology, beginning with analog controls and evolving into microcontrollers, then system-on-a-chip (SOC) and single-board computers (SBC). System hardware for small UAVs is often called the flight controller (FC), flight controller board (FCB) or autopilot. Common UAV-systems control hardware typically incorporate a primary microprocessor, a secondary or failsafe processor, and sensors such as accelerometers, gyroscopes, magnetometers, and barometers into a single module.

Architecture

Sensors

Position and movement sensors give information about the aircraft state. Exteroceptive sensors deal with external information like distance measurements, while exproprioceptive ones correlate internal and external states. Non-cooperative sensors are able to detect targets autonomously so they are used for separation assurance and collision avoidance. Degrees of freedom (DOF) refers to both the amount and quality of sensors on board: 6 DOF implies 3-axis gyroscopes and accelerometers (a typical inertial measurement unit IMU), 9 DOF refers to an IMU plus a compass, 10 DOF adds a barometer and 11 DOF usually adds a GPS receiver.

Actuators

UAV actuators include digital electronic speed controllers (which control the RPM of the motors) linked to motors/ engines and propellers, servomotors (for planes and helicopters mostly), weapons, payload actuators, LEDs and speakers.

Software

UAV software is called the flight stack or autopilot. The purpose of the flight stack is to obtain data from sensors, control motors to ensure UAV stability, and facilitate ground control and mission planning communication. UAVs are real-time systems that require rapid response to changing sensor data. As a result, UAVs rely on single-board computers for their computational needs. Examples of such single-board computers include

Raspberry Pi Raspberry Pi () is a series of small single-board computers (SBCs) developed in the United Kingdom by the Raspberry Pi Foundation in association with Broadcom. The Raspberry Pi project originally leaned towards the promotion of teaching basic ...

s, Beagleboards, etc. shielded with NavIO, PXFMini, etc. or designed from scratch such as NuttX, preemptive- RT Linux, Xenomai, Orocos-Robot Operating System or DDS-ROS 2.0. Civil-use open-source stacks include: * Agilicious (also open-source hardware) * ArduCopter * CrazyFlie * KKMultiCopter * MultiWii ** BaseFlight (forked from MultiWii) *** CleanFlight (forked from BaseFlight) **** BetaFlight (forked from CleanFlight) **** iNav (forked from CleanFlight) **** RaceFlight (forked from CleanFlight) * OpenPilot ** dRonin (forked from OpenPilot) ** LibrePilot (forked from OpenPilot) ** TauLabs (forked from OpenPilot) * Paparazzi * PX4 autopilot ** DroneCode (Umbrella organization managing PX4 within the Linux Foundation) Due to the open-source nature of UAV software, they can be customized to fit specific applications. For example, researchers from the Technical University of Košice have replaced the default control algorithm of the PX4 autopilot. This flexibility and collaborative effort has led to a large number of different open-source stacks, some of which are forked from others, such as CleanFlight, which is forked from BaseFlight and from which three other stacks are forked from.

Loop principles

UAVs employ open-loop, closed-loop or hybrid control architectures. * Open loop This type provides a positive control signal (faster, slower, left, right, up, down) without incorporating feedback from sensor data. * Closed loop This type incorporates sensor feedback to adjust behavior (reduce speed to reflect tailwind, move to altitude 300 feet). The PID controller is common. Sometimes,

feedforward Feedforward is the provision of context of what one wants to communicate prior to that communication. In purposeful activity, feedforward creates an expectation which the actor anticipates. When expected experience occurs, this provides confirmato ...

is employed, transferring the need to close the loop further.

Communications

UAVs use a

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transm ...

for control and exchange of video and other data. Early UAVs had only narrowband uplink. Downlinks came later. These bi-directional narrowband radio links carried command and control (C&C) and telemetry data about the status of aircraft systems to the remote operator. In most modern UAV applications, video transmission is required. So instead of having separate links for C&C, telemetry and video traffic, a broadband link is used to carry all types of data. These broadband links can leverage quality of service techniques and carry TCP/IP traffic that can be routed over the Internet. The radio signal from the operator side can be issued from either: * Ground control – a human operating a radio transmitter/receiver, a smartphone, a tablet, a computer, or the original meaning of a military ground control station (GCS). * Remote network system, such as satellite duplex data links for some military powers. Downstream digital video over mobile networks has also entered consumer markets, while direct UAV control uplink over the cellular mesh and LTE have been demonstrated and are in trials. * Another aircraft, serving as a relay or mobile control station military manned-unmanned teaming (MUM-T). Modern networking standards have explicitly considered drones and therefore include optimizations. The 5G standard has mandated reduced user plane latency to 1ms while using ultra-reliable and low-latency communications.

Autonomy

The level of autonomy in UAVs varies widely. UAV manufacturers often build in specific autonomous operations, such as: * Self-level: attitude stabilization on the pitch and roll axes. * Altitude hold: The aircraft maintains its altitude using barometric pressure and/or GPS data. * Hover/position hold: Keep level pitch and roll, stable yaw heading and altitude while maintaining position using GNSS or inertial sensors. * Headless mode: Pitch control relative to the position of the pilot rather than relative to the vehicle's axes. * Care-free: automatic roll and yaw control while moving horizontally * Take-off and landing (using a variety of aircraft or ground-based sensors and systems; see also " autoland") * Failsafe: automatic landing or return-to-home upon loss of control signal * Return-to-home: Fly back to the point of takeoff (often gaining altitude first to avoid possible intervening obstructions such as trees or buildings). * Follow-me: Maintain relative position to a moving pilot or other object using GNSS, image recognition or homing beacon. * GPS waypoint navigation: Using GNSS to navigate to an intermediate location on a travel path. * Orbit around an object: Similar to Follow-me but continuously circle a target. * Pre-programmed aerobatics (such as rolls and loops) One approach to quantifying autonomous capabilities is based on OODA terminology, as suggested by a 2002 US Air Force Research Laboratory report, and used in the table on the right. X-47B receives fuel from an Omega K-707 tanker while operating in the Atlantic Test Ranges

X-47B receives fuel from an Omega K-707 tanker while operating in the Atlantic Test Ranges

Full autonomy is available for specific tasks, such as

airborne refueling Aerial refueling, also referred to as air refueling, in-flight refueling (IFR), air-to-air refueling (AAR), and tanking, is the process of transferring aviation fuel from one aircraft (the tanker) to another (the receiver) while both aircraft a ...

or ground-based battery switching. Other functions available or under development include; collective flight, real-time collision avoidance, wall following, corridor centring, simultaneous localization and mapping and swarming, cognitive radio and

machine learning Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence. Machine ...

. In this context,

computer vision Computer vision is an Interdisciplinarity, interdisciplinary scientific field that deals with how computers can gain high-level understanding from digital images or videos. From the perspective of engineering, it seeks to understand and automate t ...

can play an important role for automatically ensuring flight safety.

Performance considerations

Flight envelope

UAVs can be programmed to perform aggressive maneuvers or landing/perching on inclined surfaces, and then to climb toward better communication spots. Some UAVs can control flight with varying flight modelisation, such as VTOL designs. UAVs can also implement perching on a flat vertical surface.

Endurance

Flight time against mass of small drones

UAV endurance is not constrained by the physiological capabilities of a human pilot. Because of their small size, low weight, low vibration and high power to weight ratio, Wankel rotary engines are used in many large UAVs. Their engine rotors cannot seize; the engine is not susceptible to shock-cooling during descent and it does not require an enriched fuel mixture for cooling at high power. These attributes reduce fuel usage, increasing range or payload. Proper drone cooling is essential for long-term drone endurance. Overheating and subsequent engine failure is the most common cause of drone failure. Hydrogen fuel cells, using hydrogen power, may be able to extend the endurance of small UAVs, up to several hours. Micro air vehicles endurance is so far best achieved with flapping-wing UAVs, followed by planes and multirotors standing last, due to lower Reynolds number. Solar-electric UAVs, a concept originally championed by the AstroFlight Sunrise in 1974, have achieved flight times of several weeks. Solar-powered atmospheric satellites ("atmosats") designed for operating at altitudes exceeding 20 km (12 miles, or 60,000 feet) for as long as five years could potentially perform duties more economically and with more versatility than low Earth orbit satellites. Likely applications include weather drones for weather monitoring, disaster recovery, Earth imaging and communications. Electric UAVs powered by microwave power transmission or laser power beaming are other potential endurance solutions. Another application for a high endurance UAV would be to "stare" at a battlefield for a long interval (ARGUS-IS, Gorgon Stare, Integrated Sensor Is Structure) to record events that could then be played backwards to track battlefield activities.

Reliability

Reliability improvements target all aspects of UAV systems, using

resilience engineering Resilience engineering is a subfield of safety science research that focuses on understanding how complex adaptive systems cope when encountering a surprise. The term ''resilience'' in this context refers to the capabilities that a system must pos ...

and fault tolerance techniques. Individual reliability covers robustness of flight controllers, to ensure safety without excessive redundancy to minimize cost and weight. Besides, dynamic assessment of flight envelope allows damage-resilient UAVs, using non-linear analysis with ad hoc designed loops or neural networks. UAV software liability is bending toward the design and certifications of crewed avionics software. Swarm resilience involves maintaining operational capabilities and reconfiguring tasks given unit failures.

Applications

In recent years, autonomous drones have begun to transform various application areas as they can fly beyond visual line of sight (BVLOS) while maximizing production, reducing costs and risks, ensuring site safety, security and regulatory compliance, and protecting the human workforce in times of a pandemic. They can also be used for consumer-related missions like package delivery, as demonstrated by Amazon Prime Air, and critical deliveries of health supplies. There are numerous civilian, commercial, military, and aerospace applications for UAVs. These include: ;General:

Recreation Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for enjoyment, amusement, or ple ...

, Disaster relief, archeology, conservation of

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity' ...

and habitat,

law enforcement Law enforcement is the activity of some members of government who act in an organized manner to enforce the law by discovering, deterring, rehabilitating, or punishing people who violate the rules and norms governing that society. The term ...

crime In ordinary language, a crime is an unlawful act punishable by a state or other authority. The term ''crime'' does not, in modern criminal law, have any simple and universally accepted definition,Farmer, Lindsay: "Crime, definitions of", in Ca ...

, and

terrorism Terrorism, in its broadest sense, is the use of criminal violence to provoke a state of terror or fear, mostly with the intention to achieve political or religious aims. The term is used in this regard primarily to refer to intentional violen ...

. ;Commercial: Aerial surveillance, filmmaking,

journalism Journalism is the production and distribution of reports on the interaction of events, facts, ideas, and people that are the "news of the day" and that informs society to at least some degree. The word, a noun, applies to the occupation (pro ...

scientific research The scientific method is an empirical method for acquiring knowledge that has characterized the development of science since at least the 17th century (with notable practitioners in previous centuries; see the article history of scientific ...

, surveying,

cargo transport Freight transport, also referred as ''Freight Forwarding'', is the physical process of transporting commodities and merchandise goods and cargo. The term shipping originally referred to transport by sea but in American English, it has been e ...

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic ...

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ...

, Forestry, solar farming,

thermal energy The term "thermal energy" is used loosely in various contexts in physics and engineering. It can refer to several different well-defined physical concepts. These include the internal energy or enthalpy of a body of matter and radiation; heat, ...

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as ...

s and

Warfare

As of 2020, seventeen countries have armed UAVs, and more than 100 countries use UAVs in a military capacity. The global military UAV market is dominated by companies based in the United States, Turkey, China, Israel and Iran. By sale numbers, the US held over 60% military-market share in 2017. Top military UAV manufactures are including General Atomics, Lockheed Martin,

Northrop Grumman Northrop Grumman Corporation is an American multinational aerospace and defense technology company. With 90,000 employees and an annual revenue in excess of $30 billion, it is one of the world's largest weapons manufacturers and military tec ...

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and ...

, Baykar, TAI, IAIO, CASC and CAIG. China has established and expanded its presence in military UAV market since 2010. Turkey also established and expanded its presence in military UAV market. Of the 18 countries that are known to have received military drones between 2010 to 2019, the top 12 all purchased their drones from China. According to a report of 2015, Israeli companies mainly focus on small surveillance UAV systems and by quantity of drones, Israel exported 60.7% (2014) of UAV on the market while the United States export 23.9% (2014). Between 2010 and 2014, there were 439 drones exchanged compared to 322 in the five years previous to that, among these only small fraction of overall trade – just 11 (2.5%) of the 439 are armed drones. The US alone operated over 9,000 military UAVs in 2014; among them more than 7000 are

RQ-11 Raven The AeroVironment RQ-11 Raven is a small hand-launched remote-controlled unmanned aerial vehicle (or SUAV) developed for the United States military, but now adopted by the military forces of many other countries. The RQ-11 Raven was originally i ...

miniature UAVs. General Atomics is the dominant manufacturer with the Global Hawk and Predator/Mariner systems product-line. For intelligence and reconnaissance missions, the inherent stealth of micro UAV flapping-wing ornithopters, imitating birds or insects, offers potential for covert surveillance and makes them difficult targets to bring down. UAVs are used for

attack Attack may refer to: Warfare and combat * Offensive (military) * Charge (warfare) * Attack (fencing) * Strike (attack) * Attack (computing) * Attack aircraft Books and publishing * ''The Attack'' (novel), a book * '' Attack No. 1'', comic an ...

, demining, and target practice.

Civil

The civilian (commercial and general) drone market is dominated by Chinese companies. Chinese drone manufacturer DJI alone had 74% of the civil market share in 2018, with no other company accounting for more than 5%, and with $11 billion forecast global sales in 2020. Following increased scrutiny of its activities, the US Interior Department grounded its fleet of DJI drones in 2020, while the Justice Department prohibited the use of federal funds for the purchase of DJI and other foreign made UAVs. DJI is followed by Chinese company Yuneec, US company

3D Robotics 3DR is an American company headquartered in Berkeley, California that makes enterprise drone software for construction, engineering, and mining firms, along with government agencies. Prior to 2016, the company designed and marketed commercial a ...

and French company Parrot with a significant gap in market share. As of May 2021, 873,576 UAVs have been registered with the US FAA, of which 42% are categorized as commercial drones and 58% as recreational drones. 2018 NPD point to consumers increasingly purchasing drones with more advanced features with 33 percent growth in both the $500+ and $1000+ market segments. The civil UAV market is relatively new compared to the military one. Companies are emerging in both developed and developing nations at the same time. Many early stage startups have received support and funding from investors as is the case in the United States and by government agencies as is the case in India. Some universities offer research and training programs or degrees. Private entities also provide online and in-person training programs for both recreational and commercial UAV use. Consumer drones are also widely used by military organizations worldwide because of the cost-effective nature of consumer product. In 2018, Israeli military started to use DJI

Mavic Mavic may refer to: * Mavic (bicycle parts company), a French manufacturer of bicycle parts * Mavic (UAV) The Mavic () is a series of teleoperated compact quadcopter drones for personal and commercial aerial photography and videography use, rel ...

and Matrice series of UAV for light reconnaissance mission since the civil drones are easier to use and have higher reliability. DJI drones is also the most widely used commercial unmanned aerial system that the US Army has employed. DJI surveillance drones have also been used by Chinese police in Xinjiang since 2017. The global UAV market will reach US$21.47 billion, with the Indian market touching the US$885.7 million mark, by 2021. Lighted drones are beginning to be used in nighttime displays for artistic and advertising purposes.

Aerial photography

Drones are ideally suited to capturing aerial shots in photography and cinematography, and are widely used for this purpose. Small drones avoid the need for precise coordination between pilot and cameraman, with the same person taking on both roles. However, big drones with professional cine cameras, there is usually a drone pilot and a camera operator who controls camera angle and lens. For example, the AERIGON cinema drone which is used in film production in big blockbuster movies is operated by 2 people. Drones provide access to dangerous, remote or otherwise inaccessible sites.

Agriculture, forestry and environmental studies

As global demand for food production grows exponentially, resources are depleted, farmland is reduced, and agricultural labor is increasingly in short supply, there is an urgent need for more convenient and smarter agricultural solutions than traditional methods, and the agricultural drone and robotics industry is expected to make progress. Agricultural drones have been used in areas such as Africa to help build sustainable agriculture. The use of UAVs is also being investigated to help detect and fight wildfires, whether through observation or launching pyrotechnic devices to start backfires. UAVs are also now widely used to survey wildlife such as nesting seabirds, seals and even wombat burrows

Law enforcement

Police The police are a constituted body of persons empowered by a state, with the aim to enforce the law, to ensure the safety, health and possessions of citizens, and to prevent crime and civil disorder. Their lawful powers include arrest a ...

can use drones for applications such as

search and rescue Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...

and

traffic monitoring Traffic reporting is the near real-time distribution of information about road conditions such as traffic congestion, detours, and traffic collisions. The reports help drivers anticipate and avoid traffic problems. Traffic reports, especially ...

Safety and security

Threats

Nuisance

UAVs can threaten airspace security in numerous ways, including unintentional collisions or other interference with other aircraft, deliberate attacks or by distracting pilots or flight controllers. The first incident of a drone-airplane collision occurred in mid-October 2017 in Quebec City, Canada. The first recorded instance of a drone collision with a hot air balloon occurred on 10 August 2018 in Driggs, Idaho, United States; although there was no significant damage to the balloon nor any injuries to its 3 occupants, the balloon pilot reported the incident to the

National Transportation Safety Board The National Transportation Safety Board (NTSB) is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and inci ...

, stating that "I hope this incident helps create a conversation of respect for nature, the airspace, and rules and regulations". Unauthorized UAV flights into or near major airports have prompted extended shutdowns of commercial flights. Drones caused significant disruption at Gatwick Airport during December 2018, needing the deployment of the British Army. In the United States, flying close to a wildfire is punishable by a maximum $25,000 fine. Nonetheless, in 2014 and 2015, firefighting air support in California was hindered on several occasions, including at the Lake Fire and the

North Fire The North Fire was a wildfire that occurred in the Mojave Desert near the towns of Victorville and Hesperia, north of San Bernardino and south of Bakersfield, California. The fire began on July 17, 2015. The areas most impacted were adjacent to ...

. In response, California legislators introduced a bill that would allow firefighters to disable UAVs which invaded restricted airspace. The FAA later required registration of most UAVs.

Security vulnerabilities

By 2017, drones were being used to drop contraband into prisons. The interest in UAVs cyber security has been raised greatly after the Predator UAV video stream hijacking incident in 2009, where Islamic militants used cheap, off-the-shelf equipment to stream video feeds from a UAV. Another risk is the possibility of hijacking or jamming a UAV in flight. Several security researchers have made public some vulnerabilities in commercial UAVs, in some cases even providing full source code or tools to reproduce their attacks. At a workshop on UAVs and privacy in October 2016, researchers from the Federal Trade Commission showed they were able to hack into three different consumer quadcopters and noted that UAV manufacturers can make their UAVs more secure by the basic security measures of encrypting the Wi-Fi signal and adding password protection.

Aggression

UAVs could be loaded with dangerous payloads, and crashed into vulnerable targets. Payloads could include explosives, chemical, radiological or biological hazards. UAVs with generally non-lethal payloads could possibly be hacked and put to malicious purposes. Anti-UAV systems are being developed by states to counter this threat. This is, however, proving difficult. As Dr J. Rogers stated in an interview to A&T "There is a big debate out there at the moment about what the best way is to counter these small UAVs, whether they are used by hobbyists causing a bit of a nuisance or in a more sinister manner by a terrorist actor".

Countermeasures

Counter unmanned air system

The malicious use of UAVs has led to the development of counter unmanned air system (C-UAS) technologies. Automatic tracking and detection of UAVs from commercial cameras have become accurate thanks to the development of deep learning based machine learning algorithms. It is also possible to automatically identify UAVs across different cameras with different view points and hardware specification with re-identification methods. Commercial solutions such as the Aaronia AARTOS have been installed on major international airports. Anti-aircraft missile systems such as the Iron Dome are also being enhanced with C-UAS technologies. Utilising a smart UAV swarm to counter one or more hostile UAVs is also proposed.

Regulation

Regulatory bodies around the world are developing

unmanned aircraft system traffic management Unmanned aircraft system traffic management (UTM) is an air traffic management ecosystem under development for autonomously controlled operations of unmanned aerial systems (UAS) by the FAA, NASA, other federal partner agencies, and industry. They a ...

solutions to better integrate UAVs into airspace. The use of unmanned aerial vehicles is becoming increasingly regulated by the civil aviation authorities of individual countries. Regulatory regimes can differ significantly according to drone size and use. The International Civil Aviation Organization (ICAO) began exploring the use of drone technology as far back as 2005, which resulted in a 2011 report. France was among the first countries to set a national framework based on this report and larger aviation bodies such as the FAA and the EASA quickly followed suit. In 2021, the FAA published a rule requiring all commercially-used UAVs and all UAVs regardless of intent weighing 250g or more to participate in Remote ID, which makes drone locations, controller locations, and other information public from takeoff to shutdown; this rule has since been challenged in the pending federal lawsuit '' RaceDayQuads v. FAA''.

Export controls

The export of UAVs or technology capable of carrying a 500 kg payload at least 300 km is restricted in many countries by the Missile Technology Control Regime.

References

Citations

Bibliography

*Axe, David. ''Drone War Vietnam.'' Pen & Sword, Military. Great Britain. (2021). ISBN 978 1 52677 026 4 * *

External links

How Intelligent Drones Are Shaping the Future of Warfare
''Rolling Stone Magazine'' {{DEFAULTSORT:Unmanned Aerial Vehicle Wireless Avionics Robotics Emerging technologies Articles containing video clips