How to Build a Simple Plasma Rifle Aka Electrothermal Rifle




In this Instructable we will show you how to build a simple electrothermal rifle that can shoot bbs using the plasma burst from a capacitive discharge. This design is easily scalable. If you use a higher voltage or larger capacity power supply you will be able to fire the projectile faster. Using only 1 camera as a power supply will launch the bb out at very low velocities. This project uses high voltages and can shoots bbs at dangerously high speeds. We take no responsibility for damages caused by this project. Check out our other inventions and projects at our site WillCorp .

Here is a video of our high power plasma rifle in action

Step 1: Constructing the Plasma Rifle

We'll show you how to build a small low powered plasma rifle using only common everyday items like a disposable camera for the power supply.. The rifle uses pressure produced by the several thousand degree plasma produced by a capacitive discharge to launch a projectile across the room. It transforms electrical energy into kinetic without any motors, gases, explosives or anything else. A great way to amaze your friends. Or have a mini war. Warning high voltages required for the capacitor bank may cause shock.
Simply watch the embedded video for instructions

Step 2: Construction Tips

If the bb seems to just be rolling out or not even leaving the barrel, shorten the length of the pen till it shoots farthest.
Basically the whole point is to short circuit the capacitors across the steel wool inside of the barrel. For a low power cannon, the electrodes can simply be 2 wires stuck into the back of the barrel. Higher power cannons will require stronger construction techniques. Beyond a couple joules, wires cant really be used as the electrodes because they will begin to vaporize along with the steel wool. In a larger version i used 2 stainless steel rods approximately 3/16" thick. i ground the bottom of the rods to a nearly flat surface, then i drilled a 3/16" hole through a block of teflon that transects a .3" hole for the aluminum barrel. I sealed the breach with a lexan plate and a neoprene gasket. the 2 steel rods were inserted into their respective holes and were connected to 8 gauge copper wires running directly to the capacitor bank.

Step 3: Solid State Plasma Generation

Another configuration that we tested was using a trigatron to initiate the plasma discharge. Basically we built a small chamber with 3 electrodes. 2 were connected directly to the capacitor bank. the 3rd was connected to the 20 kv output of a flyback transformer. The ground of the transformer was connected to the negative electrode of the capacitor. The terminals are positioned sufficiently close together so that the hv arc lowers the resistance enough for the capacitors to discharge. The key issue with this setup is that the electrodes ablate fairly quickly and they must be adjusted every few shots. Also this setup works best with a 500v capacitor bank at around 500 joules. The Plasma generated actually sears the back of the bb turning it a dark black.



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    76 Discussions


    Reply 3 years ago

    That's slower then black powder muskets. Most black powder muskets are twice as fast.

    am i right in thinking that you are just putting the discharge of a high voltage capacitor from a camera flash through very narrow wires( the steel wool), this causes them to explode and lets you propel your projectile? i can't seem to see the video.

    can some oe tell me what the compasitor looks like how to discharge the current to the steel wool and how to insulant it would liquid rubber work
    im still a newbie to wire a i keep getting burn wounds


    9 years ago on Step 2

    I trid to bould a bit mor powerful version of that and it dosent work it discharges the 200 µF 330V caps but it dosent vaporiz the steal wool. can you pleas help me? Its a cool project!!! But it dosent work for me :( it just dosent work so pleas help me!!!!!!!!!!!!

    4 replies

    Reply 7 years ago on Introduction

    actually that sounds like a great idea, both metals are chemically very reactive, however they are toxic and unless u have plans to poison the area u fire in, dont use it but still a good idea for extremes.


    Reply 7 years ago on Introduction

    if i was you i would put a bit of flashh cotton infront of the wool so wen the wool heats up it ignites the flash cotton and that becomes your actual propoltation or watever u wana call it.. lol

    If you used Uranium-233, which can be extracted from vaseline glass, the pellet would not only fire at 2000-3000 FPS, but it would explode on contact. please kids, don't try this at home.

    Sorry, no. Once you burn steel wool, you can't do it again. You can do the same thing by touching a 9v battery to steel wool, except here, it's expelled outwards.


    9 years ago on Step 1

    so... What do I do if I can't understand anything in the video?


    9 years ago on Introduction

    i really want to make one of these and put it inside a halo plasma pistol toy and the switch to fire the bb would be in the trigger of the gun


    10 years ago on Step 1

    how far would this shoot with a 940uf 400volt capacitor bank (75J of energy)? I am using a shaped projectile (iron rod modified into a bullet)


    10 years ago on Introduction

    I'm planning on using this as a step in my Rube Goldberg machine for a class project. Would it be possible to charge a 160v, 220uf capacitor by plugging it into an outlet (or would I need to build a charger circuit) and then using that to short the steel wool? All I really need it to do is knock over a contained domino.