Modern militaries depend on fuel. Nearly 80 percent of the supplies delivered to operations in Iraq and Afghanistan consist of fuel, and it's no surprise that those military convoys are frequently the targets of insurgents.
"Do you know how many people have died delivering gasoline?" said Tom Nugent, president and co-founder of LaserMotive, a Kent, Wash.-based company looking to replace fossil fuels with laser power.
The answer to Nugent's question? Nearly 1,000 soldiers in the last decade. And that's why Nugent wants to drastically reduce the need for delivering fossil fuels. His company's approach could save lives.
It starts with a machine able to emit a beam of laser light. The beam is different from the lasers used in pointers and industrial applications. It's wide -- about 8 inches wide as it leaves the transmitter -- and then spreads wider as it travels. The beam emitter is located at a ground-based unit and operated by a person, who could control it from the same location or remotely from an entirely different place altogether.
The operator uses the machine to fire the laser beam at a photovoltaic collector located on an unmanned autonomous vehicle (UAV), small plane or helicopter. The current range of the system is about a kilometer.
By the time the beam reaches the collector on board the UAV, it's still about 10 times as intense as sunlight, although human eyes can't see it since its wavelength is deep red to near-infrared. The power levels are in the hundreds of watts to kilowatt range -- definitely hot, but not deadly at the range where it hits the plane.
When the laser hits the photovoltaic device, the photons in the light beam are converted to electricity in the same way that solar cells convert sunlight into electricity. But because the laser beam is comprised of a single wavelength of light, the conversion to electricity is much more efficient than converting multiple wavelengths of sunlight to energy.
The photons become electricity and the energy needed to fly the AUV.
Nugent says the beam could power UAVs essentially forever, because the power source is continuous and refueling is unnecessary. (An aircraft with this system would carry a small battery to power it just in case the beam was interrupted).
Beaming the laser to an UAV is just one application, though. Laser beams could be sent down fiber-optic cable to power anything currently powered by copper wire. Think: vehicle components or ground-based machines and networks.
LaserMotive is talking to military contracting companies now, and is looking to sell beam-powered UAVs to both first-responders and the military. Another aspect of the design is making it "eye safe." Nugent says he can't say exactly how they are going to do that (for copyright reasons), although it involves cutting off the beam when it encounters an object in its path that isn't supposed to be there.
The company demonstrated the technology to NASA in 2009 and won $900,000 in funding. The beam powered a robot as it climbed up 900 meters (2,952 feet) of cable suspended from a helicopter.
NASA is interested because beamed power could make space elevators more realistic. The space elevator would involve a cable strung between Earth and a satellite. Beamed power would make carrying a power source on the elevator car unnecessary.
Not everybody thinks the best application or the technology is in the military. David Graham is CEO of Powerbeam, a company that uses a similar technology to deliver small amounts of power to home appliances. He says the advantages of powering a UAV via a beam are lost because of the distances involved, and eventually solar power will take care of the energy needs for future military bases.
Space-based applications are a much better bet, said Graham.
For example, powering a lunar rover while it is out of range of sunlight would work well.
"The far side of the moon is a great place for this," he said.
The use of lasers in fiber-optic cable is also one he sees as more viable. "It's really great for places where you need power but don't want anything combustible," he said. Copper wires inside fuel tanks to power sensors are dangerous because they can create a spark, but fiber-optic cable would be much less so.
Geoffrey Landis, a scientist at NASA's John Glenn Research Center and author who has written extensively on proposals for beaming power from orbit, is more optimistic about LaserMotive's idea, and its prospects.
"I'm very much an advocate of what [LaserMotive co-founder] Jordin Kare is doing," he said. "The UAV is really not a bad application."
The big advantage to beamed power over ordinary solar energy is that it can work at night, Landis says. He adds that the distance problem is relatively easy to deal with by increasing the power of the laser, and it is less challenging technically than his proposals to beam power from orbit.