Designing A Drone To Fire From A Grenade Launcher

You might think that tiny autonomous drones that can be fired out of a standard 40 mm grenade launcher for rapid deployment would be the kind of thing the military would love to get their hands on. Which is true, of course, and a number of companies are working on the idea for police and military applications. But [Glytch] thinks the technology could also be used for search and rescue operations, so he’s working on creating a version for us civilians.

During his presentation “3D Printing Canister-Launchable Drones for City-Scale Wardriving” at the 2019 CircleCityCon, [Glytch] gave an overview of his progress towards creating a small fixed-wing Unmanned Aerial Vehicle (UAV) that can be built even by those of us who don’t have the budgets of a three letter government agency. He’s not at the point where he can do a test launch just yet, but the design is coming along nicely, and we’re extremely interested in seeing where it goes from here.

The only way you’re fitting a winged aircraft into the bore of a 40 mm launcher is by folding it up, and so far, that’s where [Glytch] has directed most of his efforts. The wings of his UAV will use a rigid leading edge that folds flat until deployment. When in flight mode, ripstop nylon attached between the body of the drone and the leading edge will be pulled taught to form the actual wing surface; think of it sort of like a bat’s wing. A similar trick will be used for the two control surfaces at the rear of the craft.

Internally, the UAV is using all off-the-shelf components which [Glytch] hopes will keep it cheap enough that they could eventually be mass produced. As he explained in a recent YouTube video, the motor, speed controller, receiver, and flight controller, are all the sort of thing you’d expect to find in a small RC quadcopter. To make it easier to manage the UAV in the field, the batteries and payload will be housed in a detachable nose cone; allowing the user to rapidly configure the hardware for different missions.

Right now, [Glytch] says the biggest obstacle keeping his drone out of the air is finding a foldable propeller with the specific characteristics he requires. Unable to find anything commercially available, he’s currently looking into designing it himself and having it 3D printed on an SLA machine. He also needs to design a sabot to hold the drone as it travels through the barrel of the launcher. Incidentally, he’s currently testing his design with an Airsoft grenade launcher, as he doesn’t want to wade through the paperwork involved in getting the real deal.

[Glytch] is no stranger to the world of high-tech UAVs. The “Watch Dog” inspired hacking drone he created last year was a huge hit, and he’s recently been working on a HD video and telemetry link over WiFi with the Raspberry Pi Zero for his flying creations.

55 thoughts on “Designing A Drone To Fire From A Grenade Launcher

  1. Seems like a air cannon could launch it a pretty good ways up, and there’s no regulatory paperwork (at least that I’m aware of). Probably get a LOT further than something that’s designed to be somewhat child-safe.

    1. Some communities do have specific legislation banning the use of air cannons. Be responsible and avoid breaking the sound barrier and you’ll probably be fine.
      I know from experience you can easily accelerate a 300g payload to half the speed of sound. Quick exhaust valve design, 150psi, barrel length of about 0.75m, cheap to build. That design scaled up did break the sound barrier…

    1. probably can just use centrifugal force to open them up. the prop can either be jointed or might just be made with a solid piece of flexible material. anyone ever try printing a prop out of ninjaflex?

    1. Its crazy how close airsoft stuff is to the real thing. I needed an AR-15 barrel wrench, but couldn’t find one locally. I found a 3d printed one on thingiverse, printed it, and to my surprise it not only fit perfectly, but held up long enough to loosen the barrel. This is a part you can’t even really see easily when the gun is assembled, but the airsoft manufacturer still make it exactly like the real thing. I guess the airsoft crowd takes accuracy very seriously. (i’m on a pun roll today)

      1. There are .22 Long Rifle conversion kits for Colt 1911 design pistols that can be made to fit onto Colt 1911 Airsoft frames, with a bit of work on the frame. Of course you want to use the better grade of Airsoft 1911 frame that’s cast aluminum or at least Zamak.

        What’s beyond the realm of practicality is adapting a higher quality Airsoft AR-15 to hold a real barrel and other parts. While the lower and upper receiver look identical in dimensions at first glance, they need a lot more work to fit real firearm parts and you’ll spend nearly as much as just buying a high quality aluminum 80% lower and machining it, and it will be able to handle more than .22 rimfire.

  2. Whats going to fire it out of the tube? A 40mm grenade has an internal propulsion charge, will he be using gun powder to launch it? Obviously the airsoft model he’s using wont hold up to that, so is that model just for testing that it physically fits in the barrel?

    Another option for launching it would be a can cannon, plus it would give him more room with work with. Its basically a metal tube that replaces the barrel of an AR-15 and uses blanks to launch a coke can or tennis ball or anything else that fits down it and makes a decent seal. We all know how easy it is to get an AR-15 (assuming he’s in the states) and the can cannon isn’t a regulated part, so if you can get the rifle you can get the cannon. I’d imagine getting this setup would be much more attainable, but decidedly less badass, than owning a 40mm grenade launcher.

    Oh and sweet project and concept, hopefully it gets off the ground (pun unabashedly intended)

    1. TAGin makes CO2 launching shells.You charge them with CO2, and a button valve on the back gets pressed by a lever system in the launcher. This releases the CO2 and propels the projectile forward. It basically acts like a self contained air cannon. The GL-06 styled launcher, or the M32 id like to get, just make for convenient aiming and firing. Not to mention look cool as heck :)

      Several people have suggested can-cannons, but I am currently not pursuing gunpowder propulsion for a variety of reasons. Prototyping/test launches are a bit less violent with pneumatic, and gives more options for fields to test at ;)

      Cheers <3

      1. Have a look at the ARMA 100 bean bag launcher. Something along those design lines could work well for a drone launcher. A similar device sold in the 1980’s was called the UN-Gun but I’ve found info on it impossible to find online. ISTR it had a buttstock and trigger rather than the high tech handgonne style of the ARMA 100.

      2. have you taken into account the difference in barrel diameter between the GL-06 and other launchers?
        I have a GL-06 just like yours, and a friend has an M203, and in trying to design printable projectiles, I found out that the GL-06 has a barrel diameter of 41mm vs the 40mm of the M203.

  3. Gonna ask the stupid question…why does it need to come out of a grenade launcher? It can fly by itself, and usually that sort of thing is reserved for devices that can’t. I can see the interest in it being compact for portability, but I don’t see any advantage here over just chucking the thing into the air and letting the flight controller do its thing.

    1. Partially because someone long ago said I couldnt make it work, and partially because its cool as heck :p

      Also it gets the drone to a desired altitude and down range, without expending a mwh of battery. Climb-out is usually the most power intensive stage of flight with small birds like this, so using a bit of compressed gas to get past that and get in the air quickly? Worth it.

      That said, the stall speed is also a concern. I am not yet sure the drone will maintain enough lift and control at a slow enough speed to allow for hand launching, though I would like to make that an option. Time will tell :) Cheers!

      1. Could try a throwing stick arrangement, like an atlatl, there was a bit of a fad for them with hand launched gliders in the 90s, but not sure if development continued in the R/C field since.

      2. Who said it can’t work. They’ve had mortar cameras since the early 2000s. Granted they’re just a whirly-gig / autogyro design, but it accomplishes much of the same deployment role. Hand launch (Raven, iirc) drones have been around about as long.

      3. If you can come up with a design that can withstand long term storage, drone and launcher could be a ready to go unit kept in a search and rescue kit. Looks like there may be some potential in metal air batteries. Pull the seal, wait a bit to ensure the battery is at full power, point to the sky and launch with a big CO2 or nitrogen cartridge. Have the drone programmed to self orient then fly an expanding spiral search while beaming video to a receiver. For better coverage have them switchable between clockwise or counter-clockwise search, or make them in non switchable patterns to be extra dummy proof.

        Flying a search at ~100 foot altitude would be faster and safer than using human crewed helicopters. GPS is so cheap that could be included with coordinates overlaid on the video so people watching the video could direct rescuers directly to a spot.

        When or if recovered the drones and launchers could be sent back to the manufacturer to be refurbished.

        1. many (if not all) MANPADS use a molten electrolyte battery. When stored, the electrolyte is solid and quite inert, these have no problem reaching 10+ years of shelf life.
          When activated, the electrolyte is melted using pyrotechnical charge, they can supply 90V at over 1A for several minutes…

          this one is for a 9K32 (or SA-7 in NATO)

      4. OK, so the project is to tube launch it, but why not leave the nose and propellor just out of the tube mouth? Then it doesn’t have to be made of chewing gum. The sabot can project rearward to still give thrust while the fuselage is leaving the tube. There’s no need for great ballistic accuracy, after all.

        A cardboard storage canister could be large enough to accommodate propellor and sabot.

        1. The barrel length can vary on 37mm/40mm launchers. He could do that for one particular tube but it wouldn’t work for others. Maybe if we had Russian style muzzle loading 40mm (those have consistent barrel length) but those aren’t available in the US.

    2. I had the same question when I read this…. It has propulsion already. Toss and fly. Now ‘Storing’ several in a tube(s) in a backpack or shoulder belt for drone protection and then easy access for deployment… that makes sense to me :) . Neat project!

    3. Sometimes the launch location is such that there is no place to get it flying. Like in heavy forest. Or between buildings. Straight up is about the only solution in those cases. Plus, at least for military use, it can be the case that standing up and giving such a thing a bit of a toss is likely to be fatal.

  4. Putting a harmless observation drone in a tool also used for a deadly fragmentation grenade.

    What could go wrong…. Not as if mistakes don’t happen. “You loaded the drone in this one right Bob?” “Yeah, oh wait it was tha”

        1. Probably the most lethal thing, in many ways, I’ve ever attempted. First shot went through the 4×6, through the 3/4 plywood behind it, through the siding and plywood of the garage, and dented my car. Not the ice, but the perfect plug that the ice had pushed through the 4×6. Subsequent shots had a cinder block backstop with the center rib aligned to the shot.
          It was water tested, and charged and fired remotely, but I was still definitely scared of it.

  5. Am at work so haven’t had time to check out video yet but… reminds me of the Switchblade.
    The switchblade is currently used by military. Photos of crashed ones in Syria show they unfold the wings by using some type of rubber cord. Creating my own canister based fixed wing drone is on my bucket list. When you fly fixed wing planes you find that they are prone to “hanger rash”. That is, very fragile on the ground, eg, inside of your car. An all in one protective + launch canister would be perfect.

    This was one of my test rigs for exactly this purpose…
    I’m convinced that a bungee based system inside the launcher can work.

  6. The Can Cannon is a ton of fun. Sends a full soda can 100 yards. It would be great fun to launch a model from it. Folks have already 3d printed go-pro “darts” to launch.

  7. No one has mentioned using an Estes motor to launch the bird…
    (I don’t have any experience with model rocketry, so feel free to shoot this idea down -there, my own pun in this thread!)

    1. I saw that done using an Ace Stomper R/C unit 40 years ago. Vertical launch R/C boost-glider. Unfortunately they did a test glide first and did not notice a blade of grass got into the swing wing slot so when it got launched only one wing fully deployed. The other got about 45 degrees and it spiraled rather spectacularly. It was at the Comsat facility, if anyone remembers flying model airplanes there.

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