GUY RAZ, HOST:
And as Kelly mentioned, it's not entirely clear who or what carried out those airstrikes in Yemen. Drones are suspected. When the history books are written, the war against al-Qaida could be called a drone war. But it's not just the military using unmanned, pilotless aircraft. Increasingly, civilians are as well.
By 2015, the Federal Aviation Administration will begin to coordinate all drone-related air traffic over the skies here in the U.S. And right now, the technology many of these civilian drones use is fairly basic. So basic that last month, Todd Humphreys, a professor at UT-Austin, managed to intercept a drone mid-flight and land it using a technique called spoofing.
TODD HUMPHREYS: Spoofing is generating counterfeit GPS signals that look to a receiver to be indistinguishable from the authentic ones coming down from the satellite.
RAZ: So you basically are kind of overtaking those signals coming from a satellite in space. You're sending more powerful signals and replicating them and then you kind of begin to shift the instructions to that drone.
HUMPHREYS: Exactly. At first, you get your signals perfectly aligned with the authentic ones and at about the same power, and then you increase the power of your signals, thereby calling during the tracking loops inside the GPS receivers. And at that point, you're in control of the receiver's output, location and time.
RAZ: Now, why we are talking to you and why this is important is because it is estimated - the government estimates that within 15 years, there could be as many as, what, 30,000 drones flying over U.S. airspace.
HUMPHREYS: That's the projection that the FAA has made. First of all, we've got a lot of the drones coming back from Afghanistan, and people realize that they could be put to more benign uses, friendly uses. We've also got a nascent industry that has been propped up in these early years because of our operations in Afghanistan and Iraq and Pakistan. And this industry is just chomping at the bit.
RAZ: How might drones be used in ways that we can only begin to imagine now?
HUMPHREYS: It's the right way of thinking about it. Only begin to imagine it now. I imagine, for example, what I've called the Chipotle copter where it delivers Chipotle burritos to my doorstep.
RAZ: That's not a bad idea.
HUMPHREYS: And then there are ways to monitor power lines. There are efficiencies to be gained in hauling freight and simple surveillance. Perhaps you could even have a drone surveilling your own home. I do think that questions of privacy and security are going to have to be addressed before we see widespread acceptance, adoption. But my thinking is that they will be addressed and that we'll come to accept and even embrace our drone overlords.
RAZ: OK. Maybe. If you could take down one of these civilian drones and let's say, in a few years, there are tens of thousands flying over U.S. airspace, couldn't that be dangerous?
HUMPHREYS: Well, we think so. And one of the reasons we did our test is that we wanted to raise the alarm early. I think of it like reinforcing the cockpit door after 9/11. That was one of the best things we did to prevent further attacks like the ones on 9/11. Well, by the same token, we should reinforce the navigation systems of these drones, harping them against spoofing attacks.
RAZ: Todd, you are going to be speaking before a congressional panel later this month about what you guys did, how you took this drone down. What are you going to tell members of Congress? What are you going to recommend?
HUMPHREYS: I'd like to see the problem solved at the source, at the GPS satellites themselves. They're transmitting an open civilian GPS signal that's easily hackable. I'd like them to add what's effectively a digital watermark to the signal, which makes them very difficult to predict and therefore difficult to spoof.
The Department of Defense is willing to implement changes like that, but it's not built into the requirements now. And who's going to pony up a few million dollars to make the change?
RAZ: That's Todd Humphreys. He's an assistant professor of orbital mechanics at the University of Texas at Austin. He and his team figured out how to intercept drones in mid-flight and take them down. Professor Humphreys, thanks so much.
HUMPHREYS: It's been a pleasure. Transcript provided by NPR, Copyright NPR.