December 24, 2015

Wishing on a Drone: Analyzing the U.S. Air Force's New "Portable Hobby Drone Disruptors" Solicitation

One thing is certainly clear. Governments around the world are having a very difficult time coming to grips with a technological reality. Inexpensive and powerful hobby drone systems, that can be trivially purchased -- or be assembled from scratch using commodity parts and open source firmware -- are not going away. In fact their proliferation has only begun, and -- like it or not -- there are no effective means available to control them.

Yes, the potential for serious drone accidents -- and even attacks -- is real. But so far, the suggested approaches to dealing with this reality seem more out of a Disney fantasy film than anything else.

Not that governments aren't trying.

Here in the U.S., we have the new FAA hobby drone registration requirement, which won't prevent a single drone incident (and bad actors will never register or accurately register), but will present a potential privacy mess for law-abiding citizens -- the FAA has now admitted that names and physical addresses of registrants will be publicly accessible online via their database. More on this at my earlier blog entry:

Over in Japan, they're talking about trying to use bigger drones with nets to try capture hobby drones. I'm not kidding! I'm picturing the attack drones and target drones getting all tangled up together in the nets and plummeting to earth to hit whatever is unfortunate enough to be underneath. Ouch. Seems like a concept from "Godzilla vs. Dronera" to me. (Hey, Toho, if you use this idea, I want a royalty!)

But the more direct, military approach is also in play.

The U.S. Air Force has just issued a solicitation for a radio-based "Portable Anti Drone Defense" system -- essentially a remote drone disruption device that can be easily used by someone familiar with -- well -- shooting guns. The Air Force wants three units to start with. Delivery required 30 days after awarding of the contract.

You can learn all about it here:

It does indeed make for interesting reading, and I thought it might be instructive to dig into the technical details a bit.

So here we go.

The requirement specifically is addressed to the disruption of commercially available personal drones. This appears to implicitly admit that self-built drones (built from easily available commodity parts as I noted above) may represent a more problematic target category.

In practice though, even commercially available drones will often be running altered and/or open source firmware, making their behavior characteristics less of a sure bet (to say the least).

A key attribute of the Drone Disruptor is that it be able to interfere with drone operator communications links in the 2.4 and 5.8 Ghz unlicensed bands.

These of course are the same bands used for Wi-Fi, and are indeed the most common locations for hobby drone comm links. (More advanced hobbyists also may control their drones through ground station links in the 433 Mhz and/or 915 Mhz bands, but who am I to tell anything to the Air Force?)

Another key bullet point of the solicitation is the ability to interfere with the GPS receivers that an increasing number of drones use for Return to Launch (RTL) functions, and for fully autonomous "waypoint" flights that can proceed without any operator comm link active.

All of this gets really, seriously complicated in practice, because any given hobby-class drone can behave in so many different ways (both planned and unplanned) when faced with the sorts of disruptions the USAF has in mind.

The cheapest variety are usually completely dependent on the comm link for flight stability. Jam or otherwise disrupt the link, and they'll usually go crazy and come crashing down.

It's a taller order if you want to actually take over control of such drones, since you need to have a compatible transmitter and a way to "bind" it to the receiver. Not impossible by any means, but a lot tougher, especially if a drone is unstable during the comm link attack process.

More sophisticated hobby drones can be programmed to do pretty much anything in the case of their comm link being interrupted or tampered with. They might be configured to just "loiter" in position, or more commonly to activate that RTL -- Return to Launch -- function that I mentioned (yes, handy if you want to trace a drone back to its point of origin).

But many hobby drones now include sophisticated GPS receivers and magnetometers (that is, electronic compasses) -- and sometimes more than one of either or both for flight control redundancy.

This is obviously why the USAF solicitation includes GPS jamming requirements (it doesn't mention anything about magnetometers).

Here again though, how any given drone will react to such interference is difficult to predict with any degree of accuracy, especially if it isn't running the firmware you presume it does (and we know even commercial drones with restricted firmware will be "rooted" and "jailbroken" to run "unapproved" firmware without restrictions, often by users just to prove that they could do it.)

For example, in the case of GPS disruption, a drone could be programmed to simply fly away as far as it can using its magnetometer references. Even without reliable magnetometer readings, a drone could execute a "dead reckoning" escape plan using only its internal electronic accelerometers and gyros (even cheap toy drones now usually include three of each to deal with the required calculations for stable flight in 3D space).

What's more, at lower altitudes, a small, $100 laser ranging ("LIDAR") system can provide another source of internal control data.

If you weren't already familiar with the field of modern hobby drones, your reaction to this discussion might understandably be something like, "Gee, I didn't realize this stuff had gotten so sophisticated."

But sophisticated it is, and becoming more so at a staggeringly fast rate.

The bottom line seems to be that while it's understandable that the USAF would wish for a portable magic box that can "shoot down" drones via radio jamming and other remote techniques, the ability of such a system to be effective against other than the "low hanging fruit" of less sophisticated hobby-class drones seems notably limited at best.

And that's a truth that all the "wishing on a drone" isn't going to change.

So if a drone shows up under your Christmas tree, please do us all a favor and fly it responsibly!

Merry Christmas and best for the holidays, everyone!

I have consulted to Google, but I am not currently doing so -- my opinions expressed here are mine alone.

Posted by Lauren at December 24, 2015 03:10 PM | Permalink
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