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Pilotless research aircraft

Flying free

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Pilotless aircraft could help monitor forest fires, or collect data over vast areas of ocean. But aviation authorities are reluctant to let them share the sky with other aircraft. Tom Clarke reports.

The pilotless Aerosonde has been used in hurricane research, and larger craft could help Veerabhadran Ramanathan study the Indian Ocean. Credit: JON BECKER/AEROSONDE; SIO/UCSD

Veerabhadran Ramanathan has a dream: fleets of gossamer-winged, solar-powered robotic aircraft cruising in formation for tens of thousands of kilometres, high above the Indian Ocean. As they fly, they carry out the atmospheric experiments that he struggles to do now with planes and satellites. Planes cannot stay airborne for long enough, and satellites are too far above the Earth's surface. “We can't continue to rely on conventional aircraft,” says Ramanathan, who is based at the Scripps Institution of Oceanography in La Jolla, California. “We need an equivalent of satellites in the atmosphere.”

Ramanathan's dream could be realized with the help of unmanned aerial vehicles (UAVs) — aircraft that can fly without pilots or remote control. UAVs already exist, and are capable of doing the science he wants and much more. The US military's Predator UAV, for example, has seen service in Kosovo and Afghanistan. And as the cost of UAVs falls, the craft are ready to fly the hawk's nest and be put to peaceful use by scientists.

But getting UAVs airborne is proving tricky. Insurance costs are staggering and aviation authorities are unsure how to regulate the craft. Fears that they could be used by terrorists have grown after 11 September, making UAVs about as welcome in civilian airspace as a UFO. Before scientists can benefit from UAVs, the runway needs to be cleared of red tape.

UAVs have clear advantages over manned aircraft. For safety, take-off and landing are usually remote controlled. But once up, UAVs can stay aloft for days or weeks on end, following a predetermined path and guided by Global Positioning System satellites.

Some can fly higher than piloted craft. The altitude record for a powered aircraft, 29,500 metres, was set last year by Helios, a super-light, solar-powered UAV made by AeroVironment, an aeroengineering company based in Monrovia, California. More robust UAVs can cruise at heights considered too low for manned craft. And with no lives at risk, they can enter extreme environments such as thunderstorms or the smoke plumes above volcanoes.

Fire watchers

The vehicles have already been involved in some impressive experiments. Jim Brass, a remote-sensing expert at NASA's Ames Research Center in Moffett Field, California, has used Altus, a modified version of Predator, to study forest fires. His team equipped the aircraft with visual and infrared sensors that could see through smoke. In September 2001, they used these to follow the hot spots of a Californian wildfire, and had the images on the Internet in just 15 minutes.

But UAVs will really come into their own when they can be used to study interactions between Earth and atmosphere. Brass's team hopes eventually to fly a UAV over the Amazon. He thinks it could be used to track daily changes in the gases released by the forest. “We've never been able to run a 24-hour flight over an ecosystem before,” he says.

Ramanathan wants similar capabilities. His project, the Indian Ocean Experiment, is designed to study the particles that seed cloud formation. The research area is the entire Indian Ocean — far too large for conventional planes to cover. So Ramanathan wants to use teams of three UAVs in parallel. One will monitor particle formation at the ocean's surface, another will fly through the clouds, measuring their chemical and physical properties, and a third will take readings from above the clouds. Plans are at an early stage, but Ramanathan has started talking to AeroVironment's Paul MacCready, the designer of Helios, about what kind of UAV might be suitable.

Aerosonde, a robotic-aircraft company based in Melbourne, Australia, is already providing its eponymous UAV to researchers. The aircraft is small, simple and efficient, and can carry enough equipment for atmospheric monitoring, weather prediction and some remote-sensing work, although not for the kind of project Ramanathan is contemplating. Last summer, Aerosondes participated in a NASA-run study of the hurricanes that batter the east coast of the United States during August and September. The UAVs were able to skim the ocean surface, measuring variables such as temperature and wind speed.

Eyes in the sky: unmanned craft have put forest fires on the Internet and Pathfinder (bottom) will be checking the ripeness of coffee. Credit: NICK GALANTE/NASA DFRC; GENERAL ATOMICS AERONAUTICAL SYSTEMS

Other applications abound. Later this year, researchers at NASA's Environmental Research Aircraft and Sensor Technology (ERAST) project, based at the Dryden Flight Research Center in Edwards, California, plan to demonstrate the commercial potential of UAVs. They will use Pathfinder Plus, a high-altitude solar-powered craft similar to Helios, to monitor large coffee plantations, with the aim of enabling farmers to spot areas where the beans are ready to be picked. Other researchers want to use the vehicles for disaster monitoring or as high-flying relay stations for mobile-phone networks. When, in 1998, NASA asked scientists to apply for funding to develop UAV experiments, it received more than 60 applications.

But researchers' enthusiasm is not shared by everyone. Stephen Hottman, a UAV expert at New Mexico State University in Las Cruces, says insurance companies charge hundreds or thousands of dollars per hour to cover UAVs. And even if researchers can clear that hurdle, they can find the aviation authorities blocking their way.

There is no regulatory body for UAVs. Researchers wanting to fly them in US airspace have to apply to the US Federal Aviation Administration (FAA) on a case-by-case basis. UAVs are always restricted to airspace where other craft rarely fly. Even so, each application can take weeks or months to process, and not all are successful. An application to fly an Altus over southern Florida, for example, was turned down because some of the flights, which were part of a plan to study electrical discharges from thunderstorms, crossed the airspace of the Kennedy Space Flight Center.

Is it a plane...?

Hottman, who is working on ways of integrating UAVs into airspace regulations, says that the FAA is still scratching its head over whether you can even register a UAV as a plane. The lack of guidelines creates a catch-22 situation. Until there are rules, there are no criteria for UAVs to meet. But because the FAA has little experience of dealing with UAVs, it is hard for it to develop rules. “It's chickens and eggs and donkeys and carrots,” says Hottman.

But researchers on the ERAST project, together with others in the UAV industry, are now putting pressure on the FAA to get the ball rolling. New Vistas International, an aerospace consultancy based in Austin, Texas, recently submitted a white paper to the FAA outlining the case for accepting UAVs into the aviation industry. And Hottman's group has developed a 'roadmap' document that outlines how one type of UAV — high-altitude, long-endurance vehicles — might be licensed. This document, currently being considered by the FAA, suggests rules for everything from a UAV's headlights to the fuel it carries.

The FAA says it recognizes the need to license UAVs, if only to remain competitive with other countries. Alton Scott, manager of the administration's Special Operations Division in Air Traffic, based in Washington DC, says the agency is “pressing on” with developing rules, and it hopes to incorporate UAVs into its regulations over the next 5 to 10 years. But with the exception of the military, requests for airspace from UAV users will still be dealt with on a case-by-case basis for now.

Although much of the investment in UAVs is in the United States, other countries seem to be ahead with their legislation. Australia already has rules for UAV flights, and Britain's Civil Aviation Authority is releasing a guide this month on how UAVs can be used and licensed to fly in UK airspace. It has also prepared draft rules on certification of UAV flightworthiness, design specifications and qualifications for operators. Other European countries are also drafting regulations.

US authorities might be encouraged to follow suit if new 'see-and-avoid' systems prove successful. These would ensure that UAVs don't fly into other aircraft or hit things on the ground. One system relies on aircraft and UAVs regularly sending out radio signals. If a craft picks up a signal, it sends out a warning in reply, alerting other aircraft and UAVs to its presence. The FAA plans to require all civilian aircraft to carry the technology needed to run this system, and it could be fitted to UAVs at relatively little cost.

Systems that do not depend on other aircraft could provide extra security. Aircraft radar has until recently been too large and power hungry to be carried by UAVs. But new lighter radar could be fitted to UAVs if the FAA required it. The Canadian company Amphitech of Laval in Quebec has developed a radar system that scans a hemisphere-shaped volume of sky around 10 kilometres in radius, and is light enough to be fitted to the larger UAVs.

Hottman and colleagues are also championing the idea of a triangular flight corridor stretching from New Mexico to Alaska, across the Pacific to Hawaii and back to New Mexico, a route that includes airspace that is less busy than elsewhere in the United States. They hope to gain clearance from the FAA to fly regular UAV missions within this corridor. As other aircraft would have to cross it, Hottman hopes it would get the FAA used to UAVs sharing airspace, and help drive the development of rules for the operation of UAVs.

The FAA says the idea is under review. But if it does get approval, UAV researchers will finally have a test-track for their vehicles. And with the new see-and-avoid technologies coming up, aviation authorities may be more willing to let UAVs range farther afield. The demand from the scientific community is clearly there. If the FAA can be persuaded to come on board, disciplines ranging from atmospheric science to ecology could benefit from a new addition to their experimental toolbox.

Altus Fire Demo → http://geo.arc.nasa.gov/sge/UAVFiRE

Indian Ocean Experiment → http://www-indoex.ucsd.edu

Pathfinder coffee project → http://www.clarku.edu/faculty/herwitz

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