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viernes, 28 de diciembre de 2007

Articulo The Economist. www.economist.com. 14/12/07

The Economist


Aviation: Unmanned aerial vehicles are a vital tool of modern warfare. Once-harmless drones are now deadly attack aircraft. Where did the technology come from, and where is it going?

Foto: www.economist.com

DUSK falls over Baghdad and Kabul, and the Predators take their places in the skies overhead, ready for action. Western soldiers prefer to fight in the dark, when their night-vision gear gives them the advantage over insurgents. They know that with drone aircraft scanning the ground, with unblinking eyes able to see by day or night and radars that can see through cloud, they “own the night”.

For the Predators' pilots, however, it is still bright daylight. Sitting in cramped metal containers in bases across America, they fly their machines by remote control from thousands of miles away, via satellite links. The video from the drones is gathered in a makeshift operations centre in the Nevada desert and distributed to leaders in the Pentagon and commanders on the ground. In the Predator operations centre, one screen monitors the weather around the Arabian Sea (Predators do not like rain or high winds), another shows the location of each aircraft on a map, and a third projects a mosaic of video images from each plane. One image shows a house under close observation in a palm grove in Iraq; another shows a road being scanned for hidden bombs. A laptop computer system known as Rover allows troops on the ground to watch the footage, and will soon let them mark out targets.

First flown in 1995, the Predator is a flimsy drone that flies as slowly as a Cessna and can carry far less weight. Yet it has become one of the most prized assets in today's wars in Iraq and Afghanistan. Initially a surveillance drone, the Predator was given a laser designator to enable it to guide precision-guided weapons from other aircraft, and then acquired its own weapons in the form of Hellfire missiles. It has thus shortened the process of finding, identifying and destroying a target—known in military jargon as the “kill chain” or the “sensor-to-shooter” cycle—to a matter of seconds if necessary. The 432nd Wing, which flies the Predators, is one of the fastest-growing units of the American air force. In 2006 it flew more than 50,000 hours, and fired Hellfires roughly every other day.

The Predator is far from being the only unmanned aerial vehicle (UAV) in use today, though it is probably the best known. The success of military UAVs is helping to push them into mainstream civil uses all over the world, in applications including border patrol, police surveillance, scientific research and disaster response. And there is a growing community of hobbyists who attach satellite-positioning units, cameras and other sensors to remote-controlled aircraft, turning them into UAVs.

Not everyone approves. Civil regulators are worried about unmanned aircraft sharing the sky with the usual manned variety, since UAVs have previously been limited to war zones or remote areas. And air forces may be reluctant to lose the mystique of the combat pilot. “There's going to be resistance,” says Colonel John Montgomery, vice-commander of the 432nd Wing. “When I first saw a briefing on the Predator three years ago, I saw one of my mission sets disappear. I miss the thrill of flying. But hanging around for hours in a plane is a waste of manpower.”

Mad as a kite
Unmanned flying machines go back a long way. Kites were used in the late 19th century to carry cameras aloft to take pictures of battlefields. And even before the Wright brothers succeeded in building a heavier-than-air flying machine, the physicist and inventor Nikola Tesla speculated that it would be possible to build a remote-controlled flying bomb—a premonition perhaps of German V-1 flying bombs and modern cruise missiles. Yet aviation history is littered with the wrecks of unmanned-aircraft projects—some of them barmy, others simply too far ahead of their time—that were given a variety of names, including “aerial torpedo” and “remotely piloted vehicle”.

Occasionally UAVs found a valuable niche, for instance as targets for anti-aircraft gunnery. The first such machine, a radio-controlled “Fairey Queen” biplane, was catapulted into the air in 1933 and survived two hours of live fire from a British warship. The following year the Air Ministry ordered 420 such aircraft, known as the Queen Bee. This gave rise to the word “drone”, which is still used to describe unmanned planes. But this was a rare success. More often, UAVs were defeated by the immaturity of the available technology, changing needs, soaring costs and, above all, the successful development of rival technologies.

Pilots wanted
For decades a human pilot's eyes, sense of balance and hands were simply the best way to guide a flying machine, stay on course and cope with problems. Orbiting satellites were better at spying on enemies than wayward reconnaissance drones, and rockets destroyed targets more reliably than temperamental flying bombs did. The success of modern UAVs such as the Predator is not due to a single technological breakthrough, but to the combination of innovations in several areas—faster computers, fly-by-wire controls, satellite navigation, miniaturisation of sensors and fast data-transmission—into a workable and affordable whole.

Early attempts at unmanned guidance involved gyroscopes. During the first world war a flying bomb known as the Kettering Bug was developed. It was an unmanned biplane with player-piano bellows to power its gyroscope and a cash-register mechanism that calculated distance flown by counting the rotations of a propeller-like rotor. But it proved unreliable and inaccurate, not least because the catapult launches upset the sensitive gyroscopes, and it never saw action.

The development of radio (for remote control), radar (to gauge height from the ground) and television (to provide final aim when nearing a target) revived the idea of flying bombs. In the second world war the American navy experimented with TV-guided drones controlled from another aircraft, but these were little more than sideshows in the Pacific, where air power came mainly from aircraft carriers. In Europe attempts to fly old American bombers packed with explosives were a failure. If anything it was the Axis powers that made the breakthrough. The Japanese used suicide kamikaze pilots to direct flying bombs with deadly effect against American ships, proving the superior guiding ability of the human brain, and the Germans successfully used the V-1 flying bomb as a weapon of terror against London—a large target a short distance away that was hard to miss.

Dibujo: www.economist.com

At the end of the war General Henry “Hap” Arnold, the chief of America's army air forces declared: “We have just won a war with a lot of heroes flying around in planes. The next war may be fought by airplanes with no men in them at all.” It was not to be. The advent of nuclear weapons relaxed the need for pinpoint accuracy, but early American cruise missiles designed to carry them—such as the navy's Regulus and air force's Matador—suffered from the perennial problem of guidance. The initial launch using rockets upset the gyroscopes, and radio guidance was unreliable because vacuum tubes suffered under high acceleration.

Radar mapping was attempted on Matador, but suffered from the limitations of 1950s computers. Another UAV, the Snark, was supposed to have intercontinental range and used a stellar guidance system that weighed one ton. “It is possible to build a transoceanic missile right now,” said one official at the time, “but we don't know whether it will land in Spain, Portugal or France.” One test shot ended up in the Amazon. As nuclear bombs became smaller, ballistic missiles won the day. Rockets flew much faster and required inertial guidance for just a few minutes to put the weapon on a predictable ballistic path. And unlike radio-controlled aircraft, rockets were all but invulnerable to jamming or interception.

Drones sometimes found a useful role in reconnaissance, especially as improvements in surface-to-air missiles made manned spy flights risky. The loss of a U2 spy plane piloted by Francis Gary Powers over the Soviet Union in 1960 led to the search for alternatives. A reconnaissance UAV known as Red Wagon did not fare well, and funding went instead into a fast, high-altitude plane that later became known as the SR-71 Blackbird, and the first Corona surveillance satellites.

But America's air force continued to experiment, converting a small jet-powered target drone, the Firebee, into an unmanned spy plane called the Lightning Bug. This was launched from another plane, took photographs of its target, and released a parachute upon its return so it could be picked up by a helicopter. It was flown over China in 1964 and then used in the Vietnam war. It was also used as bait to activate North Vietnamese anti-aircraft missile defences and transmit the resulting signals to a manned aircraft before being destroyed. Navigation progressively improved, from inertial systems to a camera with a video link, but by 1973 the drone still missed about half its targets.

The development of integrated circuits and better data links promised a bright future for UAVs in the 1970s. But the shift of military attention to the Soviet Union, the refusal of European civil authorities to allow unmanned planes in their airspace, arms-control agreements and the perennial problem of accurate navigation over long distances conspired against UAVs. Once again, rival technology for manned aircraft stole the thunder: stealthy designs to reduce the radar signature, precision weapons such as cruise missiles and laser-guided munitions and new sensors such as synthetic-aperture radar that could look through clouds.

Ultimately it was Israel, not America, that revived the use of drones in warfare. It had seen at first hand in the 1973 Arab-Israeli war the damage that modern air defences can cause. In the 1982 Lebanon war, the clever use of small Israeli-built UAVs (incorporating technology developed in America's disappointing programmes) helped win a startling air campaign in which Syria's anti-aircraft batteries in the Bekaa valley were destroyed and up to 100 Syrian jets shot down against no losses for Israel. In carefully choreographed moves, drones were used to spy on the Syrian defences, fool their radars and gather the electronic intelligence needed to destroy them.

Unlike America, which sought to operate large UAVs at long distances through hostile air space, Israel's drones operated from its own defended territory, and real-time video was transmitted through short line-of-sight data links. Israeli UAV technology became all the rage in the Pentagon, especially after the American navy lost three aircraft over Lebanon in 1983. Predator is in fact derived from a design devised by a former Israel Aircraft Industries engineer. It also benefited from the advent of the satellite-based Global Positioning System in the 1990s, which finally resolved the problem of accurate navigation. And the Predator's ability to stay aloft for a whole day helped to overcome the main shortcoming of satellites and jets: they can only glimpse a target, rather than watch it over time.

But the Predator is slow and vulnerable, requiring full mastery of the air so it can loiter without being shot down. Like Israeli machines, it was designed for benign weather conditions. In the Balkans, where Predators were first deployed, their wings tended to ice over. Pilots still say it is “skittish” to fly, and UAVs of all kinds are much more prone to crashing.

Removing the pilot from the cockpit means the UAV has to be wirelessly connected to its controllers by vulnerable data links, whether via satellites or ground-based receivers. The Pentagon buys as much as four-fifths of its bandwidth from commercial satellite operators, and the launch of a new generation of military-communications satellites is unlikely to satisfy the demand for capacity, given the need to pipe full-motion video back from UAVs. Against the Taliban and Iraqi insurgents, these problems are manageable. But against a more sophisticated state foe, particularly one able to wage electronic warfare, the benefits of such UAVs could quickly fade.

The technology of UAVs has already moved beyond the Predator, however. There are now hundreds of models under development, from vast flying wings intended to stay aloft for five years using solar power (acting more like a satellite than a plane) to tiny bug-like flying machines that could swarm and interact wirelessly.

Beyond the Predator
The cost of building UAVs is falling, making them more attractive for civilian use. It may be a long time, though, before they become as safe and reliable as civil aircraft. Allowing UAVs to fly alongside airliners will require them to develop the means to “sense and avoid” other planes; new air-traffic control systems, based on electronic rather than voice communications, will also be needed. Even in war zones, the American air force is starting to worry about the danger of aircraft colliding with smaller UAVs. Predator pilots say it is not unusual to abort a Hellfire missile strike when an army helicopter unexpectedly comes into view.

Foto: www.economist.comMilitary UAVs are evolving quickly. In recent months Predator's big brother, called Reaper, went into service in Afghanistan; it recorded its first “kill” in October. Reaper can fly twice as fast as Predator and can carry about ten times the payload, including 500lb precision bombs. Future UAVs will carry other weapons, such as air-to-air or anti-radar missiles. Support aircraft such as unmanned air-to-air refuelling tankers are already being considered; so too are unmanned “wingmen” to accompany, and be directed from, manned fighters.

Global Hawk, a large reconnaissance drone, has demonstrated the ability to take off, cross oceans and land without guidance. More processing power on board UAVs will make them more autonomous and reduce the demand for bandwidth. Surveillance drones could, for example, alert operators only when an area under observation has changed. But UAVs' growing complexity could make them as expensive as manned planes.

On the ground, control systems are becoming more sophisticated. As UAVs become more autonomous, pilots will be able to control more aircraft at once, by giving each one occasional instructions. New displays will fuse video from UAVs seamlessly with computer-generated “synthetic” scenery (generated from maps and surveillance imagery), to create the feeling of being in a real cockpit, rather than looking through a “soda-straw”, as pilots describe today's experience.

Might UAVs eventually replace manned combat aircraft altogether? The Centre for Strategic and Budgetary Assessments, an influential American think-tank, advocates cutting back the next generation of manned jets—the Joint Strike Fighter—in favour of unmanned stealth bombers that would operate from aircraft carriers. Much of the work of modern air-defence involves long-distance missile shots rather than acrobatic dog-fights. And when extreme agility is required, the limiting factor on an aircraft's performance is often the need to keep the pilot alive and conscious under high G-forces.

If manned combat aircraft do vanish, however, human pilots will still be needed. Even people developing UAVs doubt that computers will entirely replace the brain in as dynamic, unpredictable and horribly human an activity as war. “Can you still win a medal flying a UAV?” asks Colonel Montgomery, himself a jet pilot. “You may not have the fear of death, but all the other fears are still there: the fear of the unknown and the fear of failure.”

Fuente: www.economist.com
Fecha: 14/12/07

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