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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 Missile s 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 ('''U'''nmanned '''A'''ircraft '''V'''ehicle '''S'''ystem). 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 See Also: History of unmanned aerial vehicles The earliest UAV, the Hewitt-Sperry Automatic Airplane was developed during and after World War I , and a number of advances were made with the technology rush that accompanied the Second World War ; these were used both to train anti-aircraft gunners and to fly attack missions. Nevertheless, they were little more than full-sized remote controlled airplanes until the Vietnam era. Lately, with the maturing and miniaturization of applicable technologies, interest in such craft has grown within the higher echelons of the US military, as they offer the possibility of cheaper, more capable fighting machines that can be used without risk to aircrews. Initial generations have primarily been Surveillance Aircraft , but some have already been fitted with weaponry (such as the MQ-1 Predator , which utilizes AGM-114 Hellfire air-to-ground missiles). The military envisions that more and more roles will be performed by unmanned aircraft, initially bombing and ground attack, with air-to-air combat expected to be the last domain of the fighter pilot for now. An armed UAV is known as an Unmanned Combat Air Vehicle (UCAV). Another area of interest in the field of UAVs is to utilize the aircraft as a search and rescue instrument. Heat sensors could be put in place to help find humans trapped in mountain ranges, collapsed buildings or lost at sea. UAV CLASSIFICATION UAV of the German Army ]] UAVs typically fall into one of five functional categories (although multi-role airframe platforms are becoming more prevalent):
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.
The U.S. Military employs a Tier System for categorizing its UAVs. U.S. Military UAV tier system 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
US Marine Corp tiers
US Army tiers
Future Combat Systems (FCS) (US Army) classes
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. 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."UAVs on the Rise." Dickerson, L. '' Aviation Week & Space Technology ''. January 15 , 2007 . 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 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:
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 System s, Neural Network s, 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. Under the NATO Standardization Policy 4586 all NATO UAVs will have to be flown using the Tactical Control System (TCS) a system developed by the software company Raytheon . 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 a inflight UAV refueling capability, which should be available by 2009. 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.http://www.acq.osd.mil/usd/Roadmap%20Final2.pdf#search=%22Dod%20UAS%20Roadmap%202005%22 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. 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
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