I play around with this stuff as a hobbyist.
The Dji quad copter (pictured at the beginning of frostfire's link) is very popular. It ranges in price from ~500 to 1800 and up (depending on equipment).
Here are some average specs for these quads from DJI:
- Max ascent 5 m/s
- Max decent 3 m/s
- Max Speed 16 m/s
- Operating Frequency 2.400 - 2.483 GHz；5.725 - 5.825 GHz
- Max Transmission Distance FCC Compliant: 2.5 mi (4 km)
- CE Compliant: 0.3 mi (500m) (Unobstructed, free of interference)
- Max Service Ceiling Above Sea Level 6000 m
- Max Hovering Time Approx.25 minutes
On-board GPS + flight controller make these things super stable. A friend of mine recently purchased an Inspire model. With absolutely 0 previous experience, he took it off, flew it around the neighborhood and returned it home. (For folks who have ever messed around with RC planes/helicopters/quads, you know it takes a LOT of practice to become proficient in flying this stuff). The same dude could program a path for it to fly into the quad, launch it, go back inside drink a beer and watch the quad do its thing on the monitor.
Notice in the specs I posted that the FCC is involved with how far away from yourself you can fly these things. The FCC also has stipulated that you must not fly one within a certain distance of an airport or military installation (unless you apply for a permit). The same friend I mentioned was outside of the FCC "drone airspace" but DJI ships their quads with a
large safety factor. My friend had to contact DJI multiple times, confirm his actual address multiple times and finally they sent him modified firmware updates that unlocked his quad so he could fly it in his yard.
There are existing laws (*snicker* laws) that regulate where and how these things are used.
Are they a danger? Sure, with some caveats.
- Weight vs flight time. They run on batteries, it takes more power to lift and carry more weight, thus more weight = less range/flight time.
- DJI "drones" are closed systems. You would have to be pretty handy to get in its guts and alter it without "bricking" it.
- If the quad looses contact with its controller, it automatically returns to home, thus jamming its useable frequency range would effectively remove it as a threat.
- It is susceptible to weather. The flight controller will stabilize it against some wind, not strong wind.
Now this only covers DJI's quads. There are others, and you can surely build your own. In building your own, you could remove the safety features built into the DJI quads, and have yourself a single purpose, short range, one-way flying bomb, chemical disbursement tool.
Now if larger payloads and longer distances are a greater threat, I would be more concerned with flying wing type planes like the X8 the author mentioned. It's a big plane (as far as RC stuff goes) and has a very efficient wing surface. It can also carry a bigger payload (pounds vs ounces) much farther distances than a quad could under any conditions. They are more stable in weather. They are easier to build and IMO much easier to fly. One could absolutely add the same type of GPS paired flight control to it and program a route sequence into it making it fairly autonomous once launched and at altitude.
I intend only to offer some general highlights to the information offered in frostfire's link and to pose a question as I am ignorant to the viability of these things being threats: in a domestic location, how much danger could a few ounces or a couple of pounds of explosives strapped to a fairly light air-frame do if detonated in open air?
ETA: re Grateful Citizen - how do we know they haven't? I recall the shock
just a few years ago when we found out the gubment was monitoring our smart phones.