How it works: The Army’s laser-powered drone project
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Multiple lasers will be shot through a series of mirrors to create a single, larger laser beam that targets a photovoltaic cell on a drone.
In 2009, a group of researchers gathered at the NASA Dryden Flight Research Center in Ohio for the Space Elevator Power-Beaming Challenge Games. The task was to send a vehicle's one-kilometer climb up a cable using a remote power source. The winner, a company called LaserMotive, used a laser to beam energy up to a small motor on its vehicle that pulled it up the cable.
Now the Army plans to leverage this concept to power drones in flight with light beamed from lasers, according to Eric Conrad, a mechanical engineer for the Army Communications-Electronics Research, Development and Engineering Center (CERDEC).
“Other than laboratory evaluation and one-off demonstrations there really wasn’t a lot of field testing for laser power beaming,” Conrad said of the state of the technology when the Army began its effort. “And now we’re trying to work on getting more field tests out to the soldiers so they can evaluate it themselves and give us feedback on specific mission [concept of operations] details we would need to implement for our technology.”
Will Rowley, also a mechanical engineer at CERDEC, said the Army's system is source agnostic, meaning the energy can come from a battery, a generator, a vehicle’s alternator or another source. This energy will be used to power multiple lasers that will be shot through a series of mirrors to create a single, larger laser beam that targets a photovoltaic cell on a drone. The cell captures the laser's energy and transfers it to a power management system, which in turns converts it to power the drone can use.
The process is similar to how a solar panel is used to harvest energy from the sun.
“A solar panel has low efficiency just because it has to pick up many different wavelengths or colors,” Rowley said in an interview. “With a laser, however, you have one single wavelength or color of light. It can be much more efficiently absorbed, and that photovoltaic [cell] can be specifically engineered to get the maximum power conversion out of that light.”
The goal of a system like this is not to replace batteries, Conrad said, but to provide an alternative power source to keep small rotary drones aloft longer than the few dozen minutes of flight time they currently can manage. Batteries will still be needed because the laser-beaming technology only works within line of sight and in good weather.
The size of the transmitters depends on the specific project. They can be as small as a desktop computer rack or as large as a library bookshelf. They also require a cooling system that’s usually about half the size of the laser transmitter.
Conrad and Rowley said they are working with industry partners to prepare for “a key series of demos early next year.”