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USAF Spy planes to recharge by power lines

LONDON: The US Air Force Research Lab (AFRL) in Dayton, Ohio, US, is developing an electric motor-powered micro air vehicle (MAV) or spy plane that can harvest energy from power lines, which could lead to significantly longer surveillance missions.
19 Dec 2007, 1944 hrs IST,ANI

AFRL wanted to operate extended surveillance missions using remote-controlled planes with a wingspan of about a metre, but had been struggling to find a way to refuel to extend the plane's limited flight duration.

However, it seems that with the new idea of developing a spy plane, which could 'harvest' energy when needed by attaching itself to a power line, has the ability to solve the problem.

The aircraft would even have the ability to transform into inconspicuous objects, like an innocuous piece of trash hanging from the cable.

AFRL's first plan is to work out how to make a MAV flying at 74 kilometres per hour latch onto a power line without destroying itself or the line.

Also, to avoid suspicion, the plane would need to collapse its wings and hang limply on the cable like a piece of wind-blown detritus. Much of the 'morphing' technology to perform this has already been developed by DARPA, the Pentagon's research division.

Technologies developed in that program include carbon composite 'sliding skins', which enable fuselages to change shape, and telescopic wings that allow lift to be boosted in seconds by boosting a wing's surface area.

However, Zac Richardson, a power-line engineer with National Grid in the UK, has warned that the notion of landing on a power line is riddled with challenges.

Richardson said that if the MAV contacts an 11-kilovolt local power line, it could short circuit two conductors, causing an automatic disconnection of the very power the plane seeks. And, on a 400-kilovolt inter-city power line, it risks discharging sparks.

"It will hang there fizzing and banging and giving its position away anyway," New Scientist quoted Richardson, as saying.

Ian Fells, an expert in electricity transmission based in Newcastle, UK, said: "Even kites falling across power lines cause breakdowns. It's an utterly bizarre idea to try to land a plane on one."

Despite these challenges, the AFRL is planning on conducting test flights in 2008.

 link to timesofindia.indiatimes.com

Photographed! 23.Dec.2007 23:53

Freal

Strange craft over power lines, disguised as UFO.
Strange craft over power lines, disguised as UFO.

More likely scenario 25.Dec.2007 07:02

PMR Intelligence

This basic concept, that an aircraft could recharge its batteries from power lines carrying AC current, is not far fetched. But the idea that it would need to LAND on the lines to do so is quite silly.

Power lines use AC, Alternating Current. These push-pull fluctuations in current induce magnetic fields in the lines, and extending some distance beyond them in all directions (Like a series of doughnuts, each coaxial with the line and at right angles to its length). An aircraft flying through these lines of magnetic force, along the direction of the power transmission line, would "cut" the magnetic lines of force, inducing current in any conductors on board the aircraft itself. A properly coiled wire inside the aircraft could thus become the pickup coil for power already being "lost" by the line, if the coil were terminated with diodes (electricity moves one way through a diode and does not pass in the reverse direction until a very high voltage is reached) as in a rectifier. Almost all commercial power generation technology already uses this principle, but in a closed system with a rotary configuration: a power source for kinetic energy, moving a coil of metal wire, through a stong magnetic field, sometimes rectified by diodes to appear as DC current - or left in its original AC state for transmission over long distances. To charge batteries the aircraft version would need DC. (Direct Current)

Weigand cards and RFID chips power their tiny circuits in exactly the same way. AC / magnetic fields are applied, usually in a specific frequency range, and the coil in the circuit rectifies the current to power the usually low power circuit, which chirps back a weak radio pulse modulated with its unique, and pre-programmed, serial number.

A UAV could be powered the same way, if the power line leaked enough energy and the power conversion could be scaled up significantly from that used in RFID chips. But the principle is the same. The math to figure out if this is feasible is beyond my tiny brain, but the speed of the aircraft over a power line would make the power transfer considerably faster than that of a typical RFID application, which involves a recieving coil essentially stationary relative to the power source.

My guess is that a meter long wingspan is an order of magnitude larger than the actual aircraft this technology would support, but I'm not sure. Efficiency of lift climbs with smaller scales, to a point. Micro UAVs are becoming more and more important in surveillance because they can double as landed sensors (imagine a radio-equipped video camera which lands on, or embeds in, a common telephone pole on demand).


PMR Intelligence

More Stuff to look at 25.Dec.2007 09:39

Datum Fluvius

 link to www.tudelft.nl

"RoboSwift is a micro airplane fitted with shape shifting wings, inspired by the common swift, one of nature's most efficient flyers. The micro airplane will have unprecedented wing characteristics; the wing geometry as well as the wing surface area can be adjusted continuously. This makes RoboSwift more maneuverable and efficient. Resembling the common swift, RoboSwift will be able to go undetected while using its three micro cameras to perform surveillance on vehicles and people on the ground. Furthermore, it can be employed to observe swifts in flight, thus enabling new biological research."

 http://www.honeywell.com/sites/portal?smap=aerospace&page=mav_video&theme=T8

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 http://www.engr.sjsu.edu/rkwok/projects/shopcart2B.pdf

A simple low power system for providing power for RFID (explains principles)