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Oblivion: Would drones fall out of the sky if they losT communications?



Tom Cruise works with one of the drones he maintains in Oblivion (2013)

The 2013 sci-fi movie features Tom Cruise as a drone repairman after an alien invasion is a springboard for discussing real-world drones.


Oblivion is a surprisingly good scifi movie with a big focus on drones and a small teachable moment about drones crashing. 


A brief background: Oblivion is 2013 movie with Tom Cruise, Morgan Freeman, and Jamie Lannister (oops I mean Nikolaj Coster-Waldau). Cruise and his female partner are the last people on Earth. They are currently working the final shift maintaining the drones that protect the fusion reactors that are sucking up all the Earth’s water for the rest of the human race to use on Titan. Titan? The human race had to flee Earth after bad evil aliens invaded. Humans won the war but it was a pyrrhic victory and Earth was scorched. Some evil aliens were stranded and are still around sabotaging the reactors and shooting down the drones. 


The heavily weaponized drones seem mostly, mostly being the key word here, under Cruise’s control but the viewer gets a bad feeling that this won’t last much longer. It doesn’t-  and soon, among other interesting plot threads, we have mano a drono. But fortunately for the human race, small spoiler alert here, when Cruise cuts comms between the mother ship and the drones, the drones literally stop and fall out of the sky.


So let’s talk drones. Particularly drones falling out of the sky. 


In real life, drones are everywhere. Drones of all sizes are becoming increasingly common and some, indeed, do fall out of the sky. Bloomberg had an article about how Amazon’s experimental 80 pound monster delivery drone fell out of the sky in June of 2022.  But that appeared to be a classic case of bad software engineering. I’ve been working with drones since 2004 and my team has witnessed a couple of experimental drones or newly marketed ones fall out of the sky. But it’s rare and it’s definitely not due to loss of communications. Rest assured drones are designed not to fall out of the sky if comms are cut. They usually just return to home, an automated response.


Comms get lost all the time. And that’s great that drones don’t fall out of the sky from loss of comms because they lose comms All.The.Time. 


Let’s go with a quick tutorial on drones, specifically rotorcraft- the ones that can hover and take off vertically. (Drones can be fixed-wines- ones that look and act like planes not helicopters and most of this tutorial applies to them as well.) 


You have a drone which has some micro-computers onboard and a controller.


A couple of those computers are dedicated to things like hovering and not falling out of the sky. Drones are now “joystick neutral” or “GPS locked”- that means if you let go of the controls, it will just hover in the air. The whole breakthrough of the 2000s in drones was that micro-controllers could autonomously keep them from falling out of the sky. The operator could make dumb mistakes like driving the drone into trees while landing but the little drone could generally handle staying upright and on location despite gusty winds. 


A couple more computers may be devoted to executing paths that get uploaded.  Another computer may be devoted to trying to determine if the camera is seeing anything that it’s about to hit.  Another is probably constantly trying to find the best communications channel. 


Now let’s talk about the controller or ground station. The controller has joysticks to directly control the drone, a 1970s little status display, and buttons for preprogrammed functions- kinda like a video game controller. The controller may have a built in monitor and computer for programming paths or actions- this often a smart phone running an app but it can be a laptop or something bigger. In the movies, it’s a mother ship or a big display on a mother ship. In real life, your phone or a tablet works fine.


Drones usually carry two separate radios, one for controlling the drone (the go up, go down, come back commands from the joysticks and buttons) and one for streaming what the camera is seeing (oh look, it’s a wildfire right there). The camera is recording to a SD card, the streaming is just for the operator. 


It’s like having a separate app for text messages and one for streaming movies. The text messages always seem to get through but the movie may glitch-because they take up more bandwidth. You can have drones which do both with a single radio but most safety engineers cringe at this- you want to ALWAYS be able to control the drone, you don’t want the video streaming to interfere and suck up all the comms at the worst possible moment.  The control radio is usually working at a different frequency than the streaming video radio, plus the control radio frequency is chosen to work over the longest distance. That generally means you can’t transmit very much content, just simple commands but you do it over several miles- it’s a tradeoff between distance and volume.  


The streaming video is often Wifi and we all know how well that works when we walk out into the backyard. Wifi is designed for high bandwidth- for streaming movies, YouTube, and TikTok- when we’re near a router, but it’s not really good for miles and miles. 


So drones have radios and those comms are likely to stop unpredictably, especially the further away you go from the ground control station. 


Drones are designed with fail-safes, and usually the companies get them right (though sometimes not as the Bloomberg article points out). One of the big fail safes is what to do when comms are lost. You know how you get a tiny 4 bar indicator on your comms but ten when driving in a rural area, wham! it can go from 4 bars to 0 bars without warning. This happens A LOT with drones, so the drone has to be able to handle it.


Before launching, the drone operator is supposed to pick a preprogrammed response to a loss of communications more than a few seconds. There are usually three options: return to home and land, hover, or land right there. That preprogrammed response is uploaded to the drone before it takes off- it becomes an autonomous function, a spinal reflex for the drone. 


Return to home is usually the default.  Once comms has gone out for a long time, the drone immediately flies up to a safe altitude, say 200 or 300 feet which should be above the trees, then flies a straight line back to the GPS coordinate that it took off from and lands, no hands needed.


Hover is useful when you are flying indoors or in trees and if the drone tried to fly up, it would probably crash into something. Instead, you expect that you can walk closer to it or climb on top of a pickup truck (yes I’ve done that) and regain comms. 


I’ve never used the land now option but I suspect is it there for videographers who are essentially leapfrogging: fly ahead, land, drive to the drone, replace battery, fly again.


Again, notice that falling out of the sky is not one of the three options. 


There’s another aspect- you can preprogram entire operations and upload them. A common application of drones is to map out a large area, say a wildfire or flood. You the operator specify the area, the camera settings, all of that. You press a button on your phone app, it uploads that program to the drone’s onboard computers, it beeps that it got it, you press a button and the drone takes off. It zips to the area to be mapped, then starts moving back and forth taking pictures. Meanwhile the operator sees a dot on a Google Earth map that shows where the drone is and a low resolution video feed on their phone.  And you can open a can of Coke Zero and sit back in one of those comfy camping chairs and watch for hawks or vultures trying to attack your drone.


So what about comms and that part about going from 4 bars to 0 bars? That could happen. Since the drone is preprogrammed, most autonomous mapping packages don’t care whether YOU get the blue dot or video or not. It doesn’t need you. So if it loses comms, it just keeps on with its path and then returns to home when finished.  You should be able to see the drone, the whole FAA visual line of sight regulations thing, just not what the drone is seeing and that separate control radio should have enough umph to get an emergency abort/return home command to the drone.


The point is: as of today, drones don’t fall out of the sky when they lose comms. If they were programmed to kill Tom Cruise, they would probably keep executing that program to kill Tom Cruise.  They might return home or land afterward, but falling out of the sky wouldn’t be because of cutting comms.


Now let’s talk about preprogramming. Is that a good thing or a bad thing? 


Generally it’s a good thing. A person could use the joystick and “take picture” button on the controller to fly the drone along a straight path, back and forth to get mapping data. But people are not as accurate, either in flying straight lines or figuring out how often to take pictures so that they overlap enough to be overlaid into a single big map of the area. Plus since the operator is on the ground, possibly in a comfy camp chair, they can’t feel the drone slipping sideways due to the wind and compensate the way a pilot in an aircraft can or the drone can. And humans are pretty darn slow compared to computers. The military wants drones that can autonomously identify a Bad Person and shoot them because in the time it takes for a person to recognize that it is the Bad Person, line up the shot, and press shoot, they’re gone. (And sure, there could be a “ask for confirmation” step in there too.) 


BTW we call the drone the situated agent- it’s the one actually in the environment who is sensing and acting and needs to quickly make intelligent decisions. 


The point here is: drones may be preprogrammed. So they don’t need comms. 


If you’re into robotics, you have to see this movie: seriously, the main plotline is Tom Cruise as a drone repairman. If you just like action scifi movies, this is worth watching and its fine for the family, though they may fall asleep at some point... Could be a great STEM watch.


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