Unmanned aerial vehicle

An unmanned aerial vehicle (UAV) is an aircraft with no onboard pilot. UAVs can be remote controlled or fly autonomously based on pre-programmed flight plans or more complex dynamic automation systems. UAVs are currently used in a number of military roles, including reconnaissance and attack. They are also used in a small but growing number of civil applications such as firefighting where a human observer would be at risk, police observation of civil disturbances and scenes of crimes, and reconnaissance support in natural disasters.

There are a wide variety UAV shapes, sizes, configurations, and characteristics. For the purposes of this article, and to distinguish UAVs from missiles, a UAV is defined as being capable of controlled, sustained level flight and powered by a jet or reciprocating engine. Cruise missiles are not classed as UAVs, because, like many other guided missiles, the vehicle itself is a weapon that is not reused even though it is also unmanned and might in some cases be remotely guided.

The acronym UAV has been expanded in some cases to UAVS (Unmanned Aircraft Vehicle System). The Federal Aviation Administration has adopted the generic class Unmanned Aircraft System (UAS) originally introduced by the US Navy to reflect the fact that these are not just aircraft, but systems including ground stations and other elements.

History

Main article: History of unmanned aerial vehicles

The earliest UAV was A. M. Low's "Aerial Target" of 1916. A number of remote-controlled airplane advances followed, including the Hewitt-Sperry Automatic Airplane, during and after World War I, including the first scale RPV, developed by film star and model airplane enthusiast Reginald Denny in 1935. More were made in the technology rush during the Second World War; these were used both to train anti-aircraft gunners and to fly attack missions. Jet engines were applied after WW2, in such types as the Teledyne Ryan Firebee I of 1951, while companies like Beechcraft also got in the game with their Model 1001 for the United States Navy in 1955. Nevertheless, they were little more than remote controlled airplanes until the Vietnam Era.

Front view of a Predator (Reno Air Show)

With the maturing and miniaturization of applicable technologies as seen in the 1980s and 1990s, interest in UAVs grew within the higher echelons of the US military. UAVs were seen to offer the possibility of cheaper, more capable fighting machines that can be used without risk to aircrews. Initial generations were primarily surveillance aircraft, but some were fitted with weaponry (such as the MQ-1 Predator, which utilized AGM-114 Hellfire air-to-ground missiles). An armed UAV is known as an Unmanned Combat Air Vehicle (UCAV).

In the future, it is expected more and more roles will be performed by unmanned aircraft. Bombing and ground attack will be added to the surveillance role. Air-to-air combat will likely be the last domain of the human pilot. Search and rescue could be performed by UAVs with heat sensors to help find humans lost in the wilderness, trapped in collapsed buildings, or adrift at sea.

UAV classification

Luna X 2000 UAV of the German Army

UAVs typically fall into one of six functional categories (although multi-role airframe platforms are becoming more prevalent):

• Target and decoy - providing ground and aerial gunnery a target that simulates an enemy aircraft or missile
• Reconnaissance - providing battlefield intelligence
• Combat - providing attack capability for high-risk missions (see Unmanned Combat Air Vehicle)
• Logistics - UAVs specifically designed for cargo and logistics operation
• Research and development - used to further develop UAV technologies to be integrated into field deployed UAV aircraft
• Civil and Commercial UAVs - UAVs specifically designed for civil and commercial applications

They can also be categorised in terms of range/altitude and the following has been advanced as relevant at such industry events as ParcAberporth Unmanned Systems forum.

• Handheld 2,000 ft (600 m) altitude, about 2 km range
• Close 5,000 ft (1,500 m) altitude, up to 10 km range
• NATO type 10,000 ft (3,000 m) altitude, up to 50 km range
• Tactical 18,000 ft (5,500 m) altitude, about 160 km range
• MALE (medium altitude, long endurance) up to 30,000 ft (9,000 m) and range over 200 km
• HALE (high altitude, long endurance) over 30,000 ft and indefinite range
• HYPERSONIC high-speed, supersonic (Mach 1-5) or hypersonic (Mach 5+) 50,000 ft (15,200 m) or suborbital altitude, range over 200km
• ORBITAL low earth orbit (Mach 25+)
• CIS Lunar Earth-Moon transfer

The U.S. Military employs a tier system for categorizing its UAVs.

U.S. Military UAV classifications

The modern concept of U.S. Military UAVs is to have the various aircraft systems work together in support of personnel on the ground. The integration scheme is described in terms of a "Tier" system, and is used by military planners to designate the various individual aircraft elements in an overall usage plan for integrated operations. The Tiers do not refer to specific models of aircraft, but rather roles for which various models and their manufacturers competed. The U.S. Air Force and the U.S. Marine Corps each has its own tier system, and the two systems are themselves not integrated.

US Air Force tiers

• Tier N/A: Small/Micro UAV. Role filled by BATMAV (Wasp Block III). [1]
• Tier I: Low altitude, long endurance. Role filled by the Gnat 750.
• Tier II: Medium altitude, long endurance (MALE). Role currently filled by the MQ-1 Predator and MQ-9 Reaper.
• Tier II+: High altitude, long endurance conventional UAV (or HALE UAV). Altitude: 60,000 to 65,000 feet (19,800 m), less than 300 knots () airspeed, 3,000-nautical-mile (6,000 km) radius, 24 hour time-on-station capability. Complementary to the Tier III- aircraft. Role currently filled by the RQ-4 Global Hawk.
• Tier III-: High altitude, long endurance low-observable UAV. Same parameters as, and complementary to, the Tier II+ aircraft. The RQ-3 DarkStar was originally intended to fulfill this role before it was "terminated."

US Marine Corp tiers

• Tier N/A: Micro UAV. Wasp is targeted for this role, now more so given commonality with USAF BATMAV. [2]
• Tier I: Role currently filled by the Dragon Eye but transitioning to the RQ-11B Raven B.
• Tier II: Role currently filled by the Scan Eagle and, to some extent, the RQ-2 Pioneer.
• Tier III: For two decades, the role of medium range tactical UAV was filled by the Pioneer UAV. In July 2007, the Marine Corps announced its intention to retire the aging Pioneer fleet and transition to the Shadow® Tactical Unmanned Aircraft System by AAI Corporation. The first Marine Shadow systems have already been delivered, and training for their respective Marine Corps units is underway.

US Army tiers

• Tier I: Small UAV. Role filled by the RQ-11A/B Raven.
• Tier II: Short Range Tactical UAV. Role filled by the RQ-7A/B Shadow 200.
• Tier III: Medium Range Tactical UAV. Role currently filled by the RQ-5A / MQ-5A/B Hunter and i-Gnat, but transitioning to the Extended Range Multi-Purpose (ERMP) MQ-1C Warrior.

Future Combat Systems (FCS) (US Army) classes

• Class I: For small units. Role to be filled by all new UAV with some similarity to Micro Air Vehicle.
• Class II: For companies. (cancelled.) [3]
• Class III: For battalions. (cancelled.) [4]
• Class IV: For brigades. Role to be filled by the RQ-8A/B / MQ-8B Fire Scout.

Unmanned Aircraft System

UAS, or Unmanned Aircraft System, is the official U.S. Department of Defense term for an Unmanned Aerial Vehicle. The term was first officially used in the DoD 2005 Unmanned Aircraft System Roadmap 2005–2030. Many people have mistakenly used the term Unmanned 'Aerial' System, or Unmanned 'Air Vehicle' System.

Officially, the term 'Unmanned Aerial Vehicle' was changed to 'Unmanned Aircraft System' to reflect the fact that these complex systems include ground stations and other elements besides the actual air vehicles. The term UAS, however, is not widely used, as the term UAV has become part of the modern lexicon.

The military role of UAS is growing at unprecedented rates. In 2005, tactical and theater level unmanned aircraft (UA) alone had flown over 100,000 flight hours in support of Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF). Rapid advances in technology are enabling more and more capability to be placed on smaller airframes which is spurring a large increase in the number of Small Unmanned Aircraft Systems (SUAS) being deployed on the battlefield. The use of SUAS in combat is so new that no formal DoD wide reporting procedures have been established to track SUAS flight hours. As the capabilities grow for all types of UAS, nations continue to subsidize their research and development leading to further advances enabling them to perform a multitude of missions. UAS no longer only perform intelligence, surveillance, and reconnaissance (ISR) missions, although this still remains their predominant type. Their roles have expanded to areas including electronic attack (EA), strike missions, suppression and/or destruction of enemy air defense (SEAD/DEAD), network node or communications relay, combat search and rescue (CSAR), and derivations of these themes. These UAS range in cost from a few thousand dollars to tens of millions of dollars, and the aircraft used in these systems range in size from a Micro Air Vehicle (MAV) weighing less than one pound to large aircraft weighing over 40,000 pounds.

UAV functions

UAVs perform a wide variety of functions. The majority of these functions are some form of remote sensing. Less common UAV functions include interaction and transport. To create viable new UAV systems, these functions are integrated to allow the UAV to perform complex tasks within its given application.

Remote Sensing

UAV remote sensing functions include electromagnetic spectrum sensors, biological sensors, and chemical sensors. A UAV's electromagnetic sensors typically include visual spectrum, infrared, or near infrared cameras as well as radar systems. Other electromagnetic wave detectors such as microwave and ultraviolet spectrum sensors may also be used, but are uncommon. Biological sensors are sensors capable of detecting the airborne presence of various microorganisms and other biological factors. Chemical sensors use laser spectroscopy to analyze the concentrations of each element in the air.

Interaction

UAV interaction functions intentionally alter the UAV's environment in some way. These functions include attacking, taking samples, delivering a payload, and repairing a given structure.

Transport

UAVs can transport goods using various means based on the configuration of the UAV itself. Most payloads are stored in an internal payload bay somewhere in the airframe. For many helicopter configurations, external payloads can be tethered to the bottom of the airframe. With fixed wing UAVs, payloads can also be attached to the airframe, but aerodynamics of the aircraft with the payload must be assessed. For such situations, payloads are often enclosed in aerodynamic pods for transport.

Scientific Research Unmanned aircraft are uniquely capable of penetrating areas which may be too dangerous for piloted craft. The National Oceanic and Atmospheric Administration (NOAA) began utilizing the Aerosonde® unmanned aircraft system in 2006 as a hurricane hunter. AAI Corporation subsidiary Aerosonde Pty Ltd. of Victoria, Australia, designs and manufactures the 35-pound system, which can fly into a hurricane and communicate near real-time data directly to the National Hurricane Center in Florida. Beyond the standard barometric pressure and temperature data typically cultivated from manned hurricane hunters, the Aerosonde system provides measurements far closer to the water’s surface than previously captured. Further applications for unmanned aircraft can be explored once solutions have been developed for their accommodation within national airspace, an issue currently under discussion by the Federal Aviation Administration.

Design and development considerations

UAV design and production is a global activity, with manufacturers all across the world. The United States and Israel were initial pioneers in this technology, and U.S. manufacturers have a market share of over 60% in 2006, with U.S. market share due to increase by 5-10% through 2016. Northrop Grumman and General Atomics are the dominant manufacturers in this industry, on the strength of the Global Hawk and Predator/Mariner systems. Israeli and European manufacturers form a second tier due to lower indigenous investments, and the governments of those nations have initiatives to acquire U.S. systems due to higher levels of capability. European market share represented just 4% of global revenue in 2006.

Degree of autonomy

File:CPonte Predator2.JPG

Rear view of a Predator (Reno Air Show)

UAV monitoring and control at CBP

Some early UAVs are called drones because they are no more sophisticated than a simple radio controlled aircraft being controlled by a human pilot (sometimes called the operator) at all times. More sophisticated versions may have built-in control and/or guidance systems to perform low level human pilot duties such as speed and flight path stabilization, and simple prescripted navigation functions such as waypoint following.

From this perspective, most early UAVs are not autonomous at all. In fact, the field of air vehicle autonomy is a recently emerging field, whose economics is largely driven by the military to develop battle ready technology. Compared to the manufacturing of UAV flight hardware, the market for autonomy technology is fairly immature and undeveloped. Because of this, autonomy has been and may continue to be the bottleneck for future UAV developments, and the overall value and rate of expansion of the future UAV market could be largely driven by advances to be made in the field of autonomy.

Autonomy technology that is important to UAV development falls under the following categories:

• Sensor fusion: Combining information from different sensors for use on board the vehicle
• Communications: Handling communication and coordination between multiple agents in the presence of incomplete and imperfect information
• Path planning: Determining an optimal path for vehicle to go while meeting certain objectives and mission constraints, such as obstacles or fuel requirements
• Trajectory Generation (sometimes called Motion planning): Determining an optimal control maneuver to take to follow a given path or to go from one location to another
• Trajectory Regulation: The specific control strategies required to constrain a vehicle within some tolerance to a trajectory
• Task Allocation and Scheduling: Determining the optimal distribution of tasks amongst a group of agents, with time and equipment constraints
• Cooperative Tactics: Formulating an optimal sequence and spatial distribution of activities between agents in order to maximize chance of success in any given mission scenario

Autonomy is commonly defined as the ability to make decisions without human intervention. To that end, the goal of autonomy is to teach machines to be "smart" and act more like humans. The keen observer may associate this with the development in the field of artificial intelligence made popular in the 1980s and 1990s such as expert systems, neural networks, machine learning, natural language processing, and vision. However, the mode of technological development in the field of autonomy has mostly followed a bottom-up approach, and recent advances have been largely driven by the practitioners in the field of control science, not computer science. Similarly, autonomy has been and probably will continue to be considered an extension of the controls field.

To some extent, the ultimate goal in the development of autonomy technology is to replace the human pilot. It remains to be seen whether future developments of autonomy technology, the perception of the technology, and most importantly, the political climate surrounding the use of such technology, will limit the development and utility of autonomy for UAV applications.

Interoperable UAV technologies became essential as systems proved their mettle in military operations, taking on tasks too challenging or dangerous for warfighters. NATO addressed the need for commonality through STANAG (Standardization Agreement) 4586. According to a NATO press release, the agreement began the ratification process in 1992. Its goal was to allow allied nations to easily share information obtained from unmanned aircraft through common ground control station technology. STANAG 4586-compliant aircraft are equipped to translate information into standardized message formats; likewise, information received from other compliant aircraft can be transferred into vehicle-specific messaging formats for seamless interoperability. Amendments have since been made to the original agreement, based on expert feedback from the field and an industry panel known as the Custodian Support Team. Edition Two of STANAG 4586 is currently under review. There are many systems available today that comply with STANAG 4586, including products by industry leaders such as AAI Corporation, CDL Systems, and Raytheon, all three of which are members of the Custodian Support Team for this protocol.

Endurance

Because UAVs are not burdened with the physiological limitations of human pilots, they can be designed for maximized on-station times. The maximum flight duration of unmanned aerial vehicles varies widely. Internal combustion engine aircraft endurance depends strongly on the percentage of fuel burned as a fraction of total weight (the Breguet endurance equation), and so is largely independent of aircraft size. Solar electric UAVs hold the potential for unlimited flight, a concept championed by the Helios Prototype, which unfortunately was destroyed in a 2003 crash. One of the major problems with UAVs currently is that there is no capability for in flight refuelling. Currently the US Air Force is promoting research that should end in an inflight UAV refueling capability, which should be available by 2009.

Notable high endurance flights

UAV	Flight time	Date	Notes
Boeing Condor	58 hours, 11 minutes	?	The aircraft is currently in the Hiller Aviation Museum, CA. Hiller Aviation Museum reference to the flight
QinetiQ Zephyr Solar Electric	54 hours	September 2007	QinetiQ press release New Scientist article
IAI Heron	52 hours	?	NOVA PBS TV program reference IAI reference
AC Propulsion Solar Electric	48 hours, 11 minutes	June 3, 2005	AC Propulsion release describing the flight
MQ-1 Predator	40 hours, 5 minutes	?	UAV Forum reference Federation of American Scientists reference
GNAT-750	40 hours	1992	Directory of US Military Rockets and Missiles reference to the flight UAV Endurance Prehistory reference
Aerosonde	38 hours, 48 minutes	May 3, 2006	Aerosonde release on the flight
I-GNAT	38 hours, landed with 10 hour reserve	?	General Atomics reference to the flight
RQ-4 Global Hawk	30 hours, 24 minutes	?	Space Daily story on the flight RAND Corporation report
TIHA (Turkish Unmanned Aerial Vehicle)	24 hours	Prototypes: 24 December 2004 Serial Production: To be complete by 2010	TIHA Program Turkish Aerospace Industries UAV Products

Existing UAV systems

UAVs have been developed and deployed by many countries around the world. For a list of models by country, see List of unmanned aerial vehicles.

Trivia

• UAVs have been used in many episodes of the science fiction television series Stargate SG-1, and a sentient Unmanned Combat Aerial Vehicle (UCAV) was a central figure in the action film Stealth.
• Marilyn Monroe, then named Norma Jeane Baker, was discovered while working in the factory building the first mass-produced UAVs, the OQ-2 Radioplane.
• During the Gulf War, Iraqi Army forces surrendered to the UAVs of the USS Wisconsin.
• In October, 2002, a few days before the U.S. Senate vote on the Authorization for Use of Military Force Against Iraq Resolution, about 75 senators were told in closed session that Saddam Hussein had the means of delivering biological and chemical weapons of mass destruction by UAV drones that could be launched from ships off the Atlantic coast to attack U.S. eastern seaboard cities. Colin Powell suggested in his presentation to the United Nations that they had been transported out of Iraq and could be launched against the U.S. Actually, Iraq had no fleet of UAVs nor any capability of putting UAVs on ships. Neither did Iraq have any chemical weapons. Iraq's UAV fleet consisted of only a few outdated Czech training drones. At the time, there was a vigorous dispute within the intelligence community as to whether CIA's conclusions about Iraqi UAVs were accurate. The U.S. Air Force agency most familiar with UAVs denied outright that Iraq possessed any offensive UAV capability.
• In December 2002, the first ever dogfight involving a UAV occurred when an Iraqi MiG-25 and a U.S. RQ-1 Predator fired missiles at each other. The MiG's missile destroyed the Predator.

See also

• History of unmanned aerial vehicles
• Unmanned Combat Air Vehicle (UCAV)
• Unmanned Aircraft System (or UAS)
• UAV Battlelab
• International Aerial Robotics Competition
• Unmanned Ground Vehicle
• Remotely Operated Vehicle (or ROV)
• Autonomous Underwater Vehicle
• Intelligence, Surveillance, Target Acquisition, and Reconnaissance (or ISTAR)
• Aerobot
• Cruise Missile, a related but distinct class of autonomous flying systems
• Kettering Bug
• ParcAberporth

External links

• Current Unmanned Vehicles and Systems
• Gyrodyne UAV History
• VTOL UAV's
• UAV MarketSpace - a comprehensive UAV and UAS Resource Website
• Picture of Swiss UAV in Finnish Army
• "Human Pilots: Who Needs 'Em?" — Wired News, 23 November 2003
• Future Possible Uses and Designs of UAVs from the World Think Tank
• AUVS International Aerial Robotics Competition — Home page by Robert Michelson, AUVS International / Georgia Tech Research Institute
• Defense Update coverage of UAV Mission Systems
• Defense Update reports about UAV employment in Persistent Surveillance
• UAVs at IAI/Malat
• UAVs over Kosovo - did the Earth move? Defense Systems Daily article about NATO UAV operations in Kosovo 1999, includes a list of losses
• UAV operations An Indian Journal of Aerospace Medicine Analysis of Human Factor Issues in UAV accidents
• The UK and US governments are sharing the latest technology for unmanned aerial vehicles (UAV)
• Civilian UAV development
• Autonomy Technologies for Rotorcraft and Fixed Wing Platforms
• TAI's Tiha MALE UAV
• DoD UAS Roadmap 2005-2030
• FAA UAS FAQ
• History of WWI-era UAVs
• White paper detailing development and flight test of experimental tail-sitter UAV
• Raven UAV (tiny drone) launch from building in Najaf, Iraq
• A Fully Autonomous Helicopter Flight Demonstration Video
• Officially confirmed / documented NATO UAV losses in the Balkans
• UAV Focus - Daily News and Information for the UAV and UAS Industry
• The Remote Control Aerial Photography Association, commercial UAS operators
• Opensource UAV control system
• Israel sets combat drones against missile launchers in Gaza, World Tribune, May 8, 2007
• Israel Starts Reexamining Military Missions and Technology, Aviation Week, August 20, 2006
• UAV uses and Technology
• Wasp III