The September 11, 2001 attacks initiated a flurry of advances in military technology over the past decade that has helped the U.S. and its allies redefine modern warfare. None of these advancements have had a greater impact on America's missions in the Middle East than the maturation of remotely piloted aircraft (RPA), also known as unmanned aerial vehicles (UAVs) or, more generically, drones. The U.S. Army's drone armada alone has expanded from 54 drones in October 2001, when U.S. combat operations began in Afghanistan, to more than 4,000 drones performing surveillance, reconnaissance and attack missions in Afghanistan, Iraq and Pakistan (pdf). There are more than 6,000 of them throughout the U.S. military as a whole, and continued developments promise to make these controversial aircraft—blamed for the deaths of militants as well as citizens—far more intelligent and nimble. Whereas drones themselves are certainly not a new concept—their origins can be traced back to the 1840s—since 9/11 they can now be loaded with a variety of sensors and weapons and are controlled by highly trained operators using a joystick and video monitor thousands of kilometers from a combat zone. "One of the most significant things that has occurred since 9/11 is the shift from, if you will, peer-to-peer warfare to a focus on irregular warfare," says U.S. Air Force chief scientist Mark Maybury. RPAs, as the Air Force refers to them because they are indeed operated by pilots, are helping U.S. troops and their allies adjust to that shift by delivering reconnaissance data and attack support against enemies difficult to spot because of their ability to blend in with noncombatants and the rugged terrain of their surroundings. [View a slide show featuring different drones used by the U.S. military] Use of drones has grown across several branches of the military as well as the CIA (one of the earliest users of unmanned aircraft). The Air Force, for example, logged its first 250,000 hours of drone flight time between 1995 and May 2007. The next 250,000 hours of drone flight time, however, took only a year and a half, from May 2007 to November 2008. The Air Force achieved its third set of 250,000 flight-time hours in just one year, from December 2008 to December 2009. The Department of Defense's 2012 plan calls for "purchasing more of the existing unmanned aircraft systems for current operations, improving the systems already in service, and designing more-capable unmanned aircraft systems for the future," according to a Congressional Budget Office (CBO) report published in June (pdf). The CBO estimates that the Defense Department will spend about $36.9 billion across its different branches on 730 new medium-sized and large drones through 2020. This expansion of the military's unmanned aircraft campaign brings with it a degree of concern as drones have come under fire by critics. Some dispute the military's accuracy claims and point to unmanned aircraft as the cause of thousands of civilian deaths in the war-torn Middle East over the past decade. Others note that the fight against terrorist organizations such as al Qaeda embedded in civilian zones—most notably the killing of Osama bin Laden—has primarily been carried out using time-tested intelligence methods rather than drone-launched Hellfire air-to-surface missiles. Dawn of the drone The use of unmanned aircraft in war goes back 162 years, when Austria used pilotless balloons to drop bombs on Venice in 1849. As Scientific American reported at the time: "In a favorable wind the balloons will be launched and directed as near to Venice as possible, and on their being brought to vertical positions over the town, they will be fired by electro magnetism by means of a long isolated copper wire with a large galvanic battery placed on the shore. The bomb falls perpendicularly, and explodes on reaching the ground." In the early 20th century the U.S. military recruited remote-controlled airplanes to serve as decoys or even to attack enemy targets during the First and Second World wars. From the 1950s, these aircraft began to support troops with the aid of cameras, sensors, communications equipment or other payloads. "In terms of modern use, drones really started in the early 1990s, where they were an advanced concept technology demonstration at DARPA [the Defense Advanced Research Projects Agency]," Maybury adds. General Atomics Aeronautical Systems, Inc.'s Predator drones were introduced to combat in the mid-1990s and deployed in the U.S.'s 1999 Kosovo air campaign for surveillance and reconnaissance. Predators (which have a 20-meter wingspan) were first used in Afghanistan in October 2001 to provide intelligence and a strike capability to Operation Enduring Freedom, the official name used by the U.S. government for the war in Afghanistan. A CIA-controlled Predator drone firing a Hellfire missile killed six suspected al Qaeda terrorists in Yemen on November 3, 2002—the first use of an armed Predator as an attack aircraft outside of a theater of war such as Afghanistan, according to the Federation of American Scientists (FAS). Stepping up drone missions In the past year alone, the Air Force has supported more than 400 firefights involving RPAs, Maybury says. In 2010 they captured 30,000 hours of full motion video during their missions along with 11,000 high fidelity images. "We call them remotely piloted aircraft because in fact we have professionals—both pilots and sensor operators—operating them," Maybury says. "I don't even like the word 'drones.' It sounds boring personally." The Air Force's large-scale RPA deployment began after 9/11; it had a single RPA in operation in 2001. The Air Force now operates at least four different models of medium-sized or large unmanned aircraft. In addition to its 175 Predators, there are 14 jet-powered Northrop Grumman RQ-4 Global Hawks, the largest RPAs in the Air Force's fleet with wingspans of 35 to 40 meters. About 40 turboprop-powered General Atomics MQ-9 Reapers (a larger version of the Predator) were supposed to be entering the fleet this year. The Air Force also uses the Lockheed Martin RQ-170 Sentinel, a "stealthy reconnaissance aircraft whose existence has only recently been acknowledged by the Air Force," the CBO reports. Last year, for the first time in its history, the Air Force trained more RPA pilots than fixed-wing pilots. RPAs are often equipped with full-motion cameras, infrared cameras to provide night vision, signals intelligence sensors to eavesdrop on communications and a variety of other sensors. In addition to a pilot, each RPA has a sensor operator who directs the cameras and signals sensors during a mission. All of this information is fed to a system of "exploiters," Air Force personnel who analyze all of that streaming video and other signal intelligence coming in and feed information as needed back to the pilot and sensor operator. Other branches of the military, as well as the CIA, have also come to rely heavily on drones. The Army primarily operates three medium-sized models of unmanned aircraft—Northrop Grumman MQ-5B Hunters, AAI Corp. RQ-7 Shadows (also used by the Marines), and two different types of Predators. The CBO estimates that the Army alone will spend about $5.9 billion in the next five years to add to its drone fleet. The Navy is testing two new types of RPA—the long-endurance Broad Area Maritime Surveillance (BAMS) aircraft—a Global Hawk variant—and the Northrop Grumman MQ-8B Firescout unmanned helicopter. The Navy's plans call for purchasing 65 BAMS through 2026 and 168 Firescouts through 2028, according to the CBO. ROVER ground stations This wide variety of drones enables attacks on a diversity of enemy positions, but perhaps as significant is the ability to communicate with troops on the ground. This is done with the help of Remotely Operated Video Enhanced Receiver (ROVER) ground stations that combine a ruggedized laptop, software, a handset and a radio to give troops live, overhead intelligence from a variety of platforms—manned aircraft, unmanned aircraft, just about anything with a camera able to stream a data feed, says Chris Bronk, an information technology policy research fellow at Rice University's James A. Baker III Institute for Public Policy in Houston and a former U.S. State Department diplomat. "This helps American soldiers see beyond the next hill, in real time," he adds. The original ROVER system, developed in 2002, required a Humvee to lug it around. Newer systems can fit into a backpack. ROVERs "are particularly transformational because now you have people on the ground who can see what the aircraft is seeing in the air in real time while also communicating with the DCGS [distributed common ground station] back in the U.S.," Maybury says. Troops with ROVERs can even request that RPA pilots and sensor operators fly or scan in a particular direction or over a particular area. A key development in RPA operation over the past five years has been the ability to install systems of multiple cameras such as the Gorgon Stare video capture system and the Autonomous Real-time Ground Ubiquitous Surveillance Imaging System (ARGUS-IS). "Now we're able to see not just a single full-motion video but actually wide area motion imagery [WAMI], which provides multi-spot infrared imagery," Maybury says. "Ten years ago, you get a single feed, today we're looking at 65 spots of two frames a second around a wide area." A ROVER can dial into a particular channel or tell a sensor operator to follow a particular vehicle on a particular channel. Micro air vehicles Military and intelligence units have become increasingly interested in smaller drones that can improve reconnaissance and surveillance operations. Some of these drones are hand launched while others are even smaller and resemble birds and insects. The Air Force Research Laboratory Air Vehicles Directorate Micro Air Vehicle Integration & Application Research Institute at Wright-Patterson Air Force Base in Ohio is dedicated to the development and testing of micro air vehicles (MAVs). Less than 0.6 meters in length, a MAV is capable of operating below rooftop level in an urban environment. It may have a fixed wing, rotary wing (helicopter), flapping wing or even no wings. The Air Force has been developing MAVs as a way of getting in close on enemy fighters, although such small devices are difficult to control (even a wind gust can take them out of position). AeroVironment, Inc. is developing even smaller drones that weigh less than 20 grams. DARPA contracted the Monrovia, Calif., company to design and build a flying prototype "hummingbird-like" aircraft for the Nano Air Vehicle (NAV) program. In February AeroVironment introduced its 16-centimeter-long Nano Hummingbird, capable of climbing and descending vertically, flying sideways left and right, flying forward and backward, as well as rotating clockwise and counter-clockwise under remote control and carrying a small video camera. The biologically inspired prototype is in the second phase of a three-phase DARPA NAV program, started in 2005. AeroVironment is one of four companies with phase-one contracts to develop miniature drones. The Charles Stark Draper Laboratory, Inc., in Cambridge, Mass., and Lockheed Martin have built rotary-wing NAVs, while AeroVironment and Oakland, Calif.,-based MicroPropulsion Corp. focused on flapping-wing aircraft. Collateral damage Drones are promoted to the American public as a way to strike against threats to the U.S. without putting airmen or soldiers in harm's way. Another purported benefit of drones is the precision with which they attack America's enemies. Numerous reports of civilian casualties, however, indicate that these robotic aircraft are precise only to a certain degree. The CIA and White House have been quick to point out they have found no evidence of collateral deaths from U.S. counterterrorism operations outside of Afghanistan or Iraq, a claim disputed on several fronts, most recently in a report compiled by British and Pakistani journalists. Reports of the number of civilian deaths attributed drone strikes vary, particularly in Pakistan. The Long War Journal, a Web site produced by nonprofit Public Multimedia Inc., claims that, since 2006 in Pakistan alone, drone strikes have killed 2,080 leaders and operatives from Taliban, al Qaeda, and allied extremist groups as well as 138 civilians. Meanwhile, the U.S. government claims that its drones have killed more than 2,000 militants in Pakistan and about 50 noncombatants since 2001. The Bureau of Investigative Journalism, a not-for-profit organization based at City University in London, disputes the U.S. government statistics, saying its research concluded that of the 2,292 people killed in U.S. attacks since 2004, 385 were civilians, including more than 160 children. In an August 14 New York Times editorial, former director of national intelligence Dennis Blair, a retired admiral, pointed out that, particularly in Pakistan, "drone strikes are no longer the most effective strategy for eliminating al Qaeda's ability to attack us." His reasoning: "Drone strikes hinder Qaeda fighters while they move and hide, but they can endure the attacks and continue to function." In the meantime civilian casualties from drone strikes discourage support within Pakistan for the U.S.'s efforts to eliminate al Qaeda from that region, he wrote. Blair, however, does not call for an end to drone strikes but rather closer coordination between the U.S. and Pakistan militaries when planning such strikes. The Future One of the U.S. military's goals is to increase the use of drones on a variety of mission types. In addition to adding MAVs and NAVs to the mix, Maybury sees Air Force RPAs delivering fuel and other supplies to troops in the field. RPAs will also become increasingly autonomous, monitored but not necessarily piloted by humans. This will not be easy as autonomous systems must have the capability to adapt to changing conditions with the help of artificial intelligence that aids in decision making. Still, a long-term goal is to create fleets of RPAs that can travel as a self-coordinated unit and strike in concert. The Air Force claims it will build in override controls that enable pilots on the ground to reassign or reroute RPAs if necessary. Missions for unmanned aircraft systems are expected to expand from reconnaissance and attacking ground targets to a much wider array of missions, including personnel recovery, airborne refueling, medical evacuation, and missile defense (pdf), according to FAS. In addition to launching missiles, future drones may someday be able to fire directed energy weapons, including lasers to disrupt or destroy enemy equipment and high-power microwave systems designed to burn enemy combatants without being lethal. Drones will also be able to stay in the air for years, rather than hours or days, at a time. "Last year, we did a lot of work in energy, which includes ultra-long endurance aircraft such as the Vulture and Integrated Sensor Is the Structure (ISIS), which are powered in part by lightweight solar cells," Maybury says. Regardless of how far drone technology advances it is clear that the utility they have demonstrated in supporting U.S. troops over the past 10 years will ensure that these remotely controlled aircraft are here to stay.