The Drone Threat to Public Events

The explosive popularity of unmanned aerial vehicles (UAVs)—commonly called drones—is creating a tangle of regulatory questions involving managing airspace and avoiding accidents. It also summons up possible nightmare scenarios of drone attacks on large public events, such as the upcoming Super Bowl in the United States. One person who’s been thinking about such threats, and how optics and photonics might be used in confronting them, is Gregory Quarles, the CEO of the laser firm Applied Energetics in Tucson, AZ, USA.

In a career of more than 30 years, Quarles has filled a number of roles in government, academia and industry, all focusing on laser, optical and photonic technologies and applications. (He also served for several years as chief scientist at Optica, the publisher of OPN.) We recently talked with Quarles about aspects of the UAV threat, and the role of optics in meeting it.

Before we dig into the subject of drones at public events, could you tell me a bit about Applied Energetics and what it does?

Gregory Quarles: Sure. We’re a publicly traded company, and just completed our 20^th year in business. We continue to grow, and have more than doubled our staff in each of the last two years; we’re now at 12 full-time employees and another 12 full- and part-time contractors.

Our focus is in developing short-pulse lasers, and our current revenues are coming in almost exclusively from the national security, Department of Defense and intelligence community areas. Our primary objective, though, is multi-use technology—where we want to do what we can for homeland security and national defense, but we also try to ensure that everything that we build out has a secondary use.

For example, I was recently at the Photonics West conference in San Francisco, looking at all the biomedical and tissue-imaging applications of short-pulsed lasers. The pulses are short enough that they don’t interact with the water in the molecule; therefore, you don’t have any burning of the tissue when you’re going in to create the multiphoton fluorescence for imaging.

There are also commercial applications, in additive and subtractive manufacturing. Other insertion points for our USPL [ultrashort-pulse laser] technology include quantum computing enhancements, via accessing various wavelength and time sequences, which could possibly allow for other Rydberg states to be accessed. We’ve got a good, strong team that constantly keeps within the guardrails in what we’re doing, but is always looking at the possible offramps for trying to get things out into the public domain.

From a defense perspective, reduction of size, weight and power is a key concern with USPLs in the directed-energy sector. Our innovation is to enable small, tactical vehicles to rapidly carry these systems, even down to possibly man-portable systems technology.

Let’s dive into this issue of unauthorized drones at public events. When did you start personally thinking about this emerging danger of aerial attack from these devices?

We’ve been engaging with the Department of Defense (DoD) since late 2019 or early 2020 because there have been threats on the battlefield from drones, and you have to worry about how you disrupt that threat.

As we watch what’s taking place in the war in Ukraine, we see that there are an awful lot of off-the-shelf, commercial drones and small drones manufactured by other countries that are being put into play there. It’s become the “asymmetric” threat that IEDs [improvised explosive devices] were in Afghanistan—it’s that threat that you don’t see coming, that flies below the radar.

“ As we watch what’s taking place in the war in Ukraine, we see that there are an awful lot of off-the-shelf, commercial drones and small drones manufactured by other countries that are being put into play there. ”

—Gregory Quarles

A lot of what’s taking place in Ukraine is that they’re using drones as a means of watching … as the “forward eyes” of the group. And the Ukrainians especially have come up with really ingenious ways of using a thousand-dollar, off-the-shelf drone. Video images on social media have highlighted the ease with which Ukrainian soldiers have developed techniques to use drones to drop a grenade into a chimney stack into an underground bunker.

So you watch these individuals there that are making this technology work, and you realize that this could realistically be a threat to public events such as those in the United States.

What kind of threats are we actually talking about here?

Well, I can’t go into every movie scenario … But the first thing to think about is, most of these drones can carry only very little weight with them. We’ve seen what they can do in Ukraine—they can carry a grenade; they can carry a small munition. They could drop toxic chemicals, nerve agents, at a public event and let them spread in the air; that would certainly be one thing that I would worry about.

Looking at it domestically, it’s difficult to predict the intent of 200 drones flying at 200 miles an hour at a government building or sporting event. Furthermore, how do you stop a swarm of drones in that scenario if you can’t use bullets or lasers that are not eye safe, because there are people and spectators in the area?

But I think the larger issue is that you don’t know what they’re going to do. Most of this, in this non-military environment, isn’t necessarily nefarious. You know, 99% of the people flying these drones are people who want to take videos and then turn around and either boost their image on YouTube or sell the video to whatever news outlets want to use it.

In Tucson, there were large wildfires a few years ago, and the fires were really burning the mountains up around the city. They were bringing in the big airborne water tankers to drop the water to fight the fires. And they kept having to ground the planes and helicopters, because people were flying over with these drones to try to get images of the fire and then sell them to the news stations. And anytime there’s a sighting of a drone or detection of it on a radar system, you need to ground every aircraft in the area until you’ve made sure that the drone is out of the way.

And it’s not necessarily just one drone. What happens if you pop out 50 or 100 drones, and then fly them towards a big public event—say, a NASCAR race with 100,000 people, all outside, or a big concert venue? If you remember the 2020 Tokyo Olympics, they synchronized over 1,800 drones simultaneously. There are a lot of scenarios that can play through your head on how these could really wreak havoc.

That sounds frightening—what’s being done about this?

Well, there are articles as early as 2017, talking about how we need to keep an eye on the domestic threat. In the United States, the National Football League has its own director of security that looks for what could potentially happen at big games. There’s been work on legislation to protect events that have over 30,000 people.

A lot of stadiums now have electronic detection—they look for the radio-frequency signal coming from the drone, or using radar, and they can tell when the drones in the air and how far away it is. And the rules with stadiums and sporting events right now is, from an hour before the event until an hour after, you can’t have a drone within three miles of the stadium.

So during that whole time, they’re sweeping the sky and looking. And one of the only things they can do if they find one is use an electronic jammer and cause the drone to come to the ground, or possibly get into the guidance system of the drone if it’s not protected, and reprogram it. The problem is that you have laws on tampering with an aircraft and hijacking of radio frequency that prevents most local agencies from doing anything like that.

And you see a role for the kind of technology of a company like Applied Energetics to address these kinds of threat?

Yes—from our perspective, the question is how do we use optics and photonics, lasers, to mitigate these threats and keep airspaces safe.

The technology that we’re working on is using lasers with femtosecond pulses and up to a terawatt of peak power—really high-intensity pulses for a really brief burst. And what we’re looking at is multiple possible effects in a layered threat defense.

“ If you can direct [pulsed laser] energy into the camera on one of these drones, you have the potential for instantaneously destroying the sensor. If you destroy the sensor, then the drone can’t see. ”

—Gregory Quarles

Number one, if you can direct that energy into the camera on one of these drones, you have the potential for instantaneously destroying the sensor. If you destroy the sensor, then the drone can’t see; if it can’t see, the operator may not be able to make money—or, if they’re nefarious, the drone may not be able to perform for the operator as they intend for it to. So our number-one solution is: Take out the camera.

Second, if you’re using short pulses and you interact with the outside surface of the drone, and it’s at a high enough intensity that you create a plasma, that plasma could convert into a radio frequency and that radio frequency, at the right intensity, could sweep through the electronics and jam the drone and cause it to drop.

And the third solution—not using our technology but more common continuous-wave technology—is that you burn through it. Some of these CW lasers are essentially flamethrowers; you’re sending 50 kilowatts and more out there in the atmosphere, and you can burn through the outside of the drone and drop it.

I can imagine some people having concerns about using these high-power, short-pulse lasers in an environment where there are lots of people around. How does one address that in considering these kinds of solutions?

Well, one of the things we’ve worked on and made part of our culture and our technology focus is to get these USPL systems operating out past 1.7 microns in wavelength, where the laser is going to be non-threatening to the eye—you’re never going to be able to burn a retina with it. That’s something you’ve also got to do to satisfy the requirements of the Federal Aviation Administration.

Then, also, if you can engage them at three miles outside of the stadium or venue, as soon as they cross that boundary, perhaps they’re far enough out that if the drone does drop, it’s not going to be in the middle of the crowd. And the technology we’re talking about is not going to break the drone apart or do anything like that. But we feel we can use the short-pulse technology to take out part of their system or take out the camera, and either have the drone drift down or force the drone to go home.

These kinds of solutions seem to get into some tricky legal and policy areas, though.

Yes. You’re not allowed to drop these things in the United States unless you have federal orders. So local law enforcement has zero oversight on this—they’re not allowed to do anything. Yet you can’t do anything from the Department of Defense level, either, because legally it’s covered by local jurisdiction!

So the Department of Homeland Security, border patrol, the Secret Service and the FBI—these are the agencies that probably have it under their umbrella. But they need to develop clear interagency policies that allow them to pull the trigger. And they also don’t have the research budgets; they’re either going to have to adapt defense-based technology to protecting the skies locally, or they’re going to have to come up with their own and be 10 years behind where everybody else is.

And the FAA is another large interested party, in view of what can happen when drones fly into restricted airspace. In the UK several years ago, drones were buzzing London airports, and then they kept having to shut down the airport over seven days and divert flights to other area airports, and then take the cargo off and ship all that to London. It cost them almost US$69 million for a one-week shutdown in terms of revenues.

Is there any effort to try to bridge the policy gaps?

“ [The] policy area has to be discussed by legislatures and the agencies. But then you’ve also got to look at the technology and what can be done. ”

—Gregory Quarles

Well, agencies are having joint meetings; I’ve been a part of some of those, where different groups are having a dialogue and trying to find out, how do we do this, and who’s got the appropriate jurisdiction. And there also needs to be a broad discussion between the suppliers of technology and the people that need to use it—at all levels; local, state, federal, global.

I think getting various federal groups together, and starting to coordinate with local authorities, coordinate with the sporting authorities and organizers of big concerts and other events—there’s got to be this kind of coordination and a discussion on policy. Currently, you’ve got groups on one side that say, You have no right to interfere with my personal property or to tap into my electronics to steer my property away from something; and then you’ve got groups on the other side saying, Yeah, but we don’t want somebody to get hurt. So how do you strike that balance?

So that policy area has to be discussed by legislatures and the agencies. But then you’ve also got to look at the technology and what can be done. There are a lot of potential solutions, and we need to come up with ways to use those solutions to try to protect the personal safety of individuals first and foremost. That’s where I think we have to go.