UAV record

Unmanned Aerial Vehicles or UAVs have long been used by the military for applications ranging from reconnaissance and surveillance to armed attacks.

While larger UAVs are powered in the same way as conventional aircraft, small UAVs - under five kilograms (11 pounds) - are battery powered, which generally limits flight time to 20 to 45 minutes.

However, German and American research teams have been working hard to overcome the shortcomings of battery-life and recently set a world record earlier this month at 12 hours, 26 minutes and 56.9 seconds.

The AscTec Pelican is a small quadrocopter developed by Ascending Technologies, a young German company based just outside of Munich. The Pelican weighs less than a kilogram and is less than 45 cm across (almost 18 inches).

Ascending Technologies teamed up with LaserMotive, an American research company that specializes in laser power technology, and was the winner of the 2009 NASA-sponsored Power Beaming Competition.

In their reach for the holy grail of unlimited power for UAVs, researchers fitted solar cells to the underside of the AscTec Pelican.

When hit by the laser, which can reach up to one kilometer, these cells convert the beam into electrical power and continuously charge the battery. Conceivably, this UAV could stay aloft forever, given unlimited laser power.

The AscTec Pelican's battery lasts for 20 minutes, so for it to fly for over 12 hours is a major breakthrough, said Michael Achtelik, the CEO of Ascending Technologies, in an interview with Deutsche Welle.

An order of magnitude greater

Law enforcement experts also are impressed by the new UAV's hover, or loiter, time.

"A UAV that has a 12 hour loiter time, its right off the charts right now,” said Charles "Sid" Heal, a technology consultant and technology chairman for the National Tactical Officers Association in the United States. Heal is also a former commander in the Los Angeles County Sheriffs Department.

"To give you an example, the best hover UAV that we have in the United States right now, even under the most ideal conditions, would have a loiter time less than one hour. So they've increased the loiter time by one order of magnitude."

Beyond law enforcement officials, others in the scientific community say that this new approach shows promise.

"It shows how much energy can be transferred via this laser powered system, since the quadrocopter system needs about three times more energy than a conventional fixed wing UAV," said Gordon Strickert, a research scientist at the German Aerospace Center in Braunschweig.

"It also shows that such a quadrocoptor system can be flown very precisely and can hold its position accurately."

Restricted use of UAVs in the United States

UAV's are currently not authorized for use in law enforcement in the United States, much to Heal's chagrin. He said this kind of breakthrough could make a real difference in law enforcement in the United States, where he worked SWAT for many years.

"Some of our incidents were in high-rise buildings," he said, noting that UAVs have particular advantages over helicopters, in that they're significantly cheaper, quieter and much less visible.

"One of the most vulnerable places is the windows, but yet we can't see in the windows. We could actually take a UAV and park it up 20 stories and literally look right in the window as if we were standing on the ground."

Drawbacks of laser power

Despite the new hover record, the laser power has its flaws, too, noted Strickert.

"You need a powerful laser and a tracking system and a power supply on the ground,” he said.

Strickert also pointed out that that the whole system is extremely inefficient because less than 10 percent of the power needed to drive the laser is converted into energy in order to fly the UAV.

Strickert also said that it's not possible to "perform rapid manoeuvres or out of sight operations when you don't fit in an additional battery."

However, Michael Achtelik from Ascending Technologies countered that the UAV has an onboard battery that can be used when the UAV flies outside of the range of the laser beam.

While some critics say that staying in the line of sight of the laser beam is a limitation, Heal said that when UAV's finally get the go ahead from the United States Federal Aeronautics Administration, they will probably only be allowed to be flown within line of sight anyway.

Heal predicts that this kind of UAV might also have civilian applications too - he posited that they could be used by lifeguards to patrol the surf line and to alert them of swimmers in distress.

Still, this kind of application may not take place until researchers can solidify the power situation - German researchers ideally would like to use solar power so that a UAV could stay aloft indefinitely.

Author: Cinnamon Nippard, Munich
Editor: Cyrus Farivar