Introduction: 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.