YouTube player

I’d been aware of vortex cannons for quite some time, mostly as an interesting toy, and after I kept stumbling on the concept while touring the web, I decided I had to build my own. There’s something fascinating about taking a substance as ubiquitous and amorphous as air and transforming it into a coherent and persistent structure, almost like a crystal. I also hoped to find some use for my vortex cannon, perhaps to propel scents or give the touch of a ghost in a haunted house.

Photo by Michael Thad Carter

An extreme example of the vortex’s “reach out and touch someone” power is the military vortex gun, which uses explosives to drive air rings that can knock people over, or at least generate enough sound pressure to render an area uninhabitable. And the Shockwave Cannon created by Survival Research Labs delivers an invisible boot to the head.

This project doesn’t go that far, but it will show you how to make two different cannons: a 5-minute version as well as a computer-controlled version driven by a subwoofer

How it Works

Just as a sphere (ball) is the natural shape for solids to roll on a surface, the toroid (donut) is the natural shape for a gas to “roll” axially through space.

Illustrations by Damien Scogin

As air moves forward through the toroid’s inside edge, it draws air back around from the outside edge to replace it. The moving air exerts less pressure than the still air around it, so it stays in the donut shape.

Making a traveling vortex is easy: just push a puff of air evenly through a wide circular aperture. As the puff emerges, surrounding air travels in to fill the low-pressure zone behind it. This pinches it off and curls it back on itself to form the ring. You can make the ring visible by using smoke or fog from a fog machine.



An empty, topless gallon milk jug will make a vortex if you thump its bottom. The “Tub Thumping” cannon here is a larger version based on a garbage can.


The “Barking Tube” cannon uses a subwoofer to push out a series of vortices. The velocity curve of the impulse affects the vortex ring: an accelerating push makes it fly faster, while a decelerating push adds spin, making it fly slower and disintegrate dramatically.


Exploring the Vortex

Tub-thumping a fog vortex at the camera. Action and build photography by Edwin Wise

With the computer-controlled Barking Tube, I wanted to experiment with different waveforms that would slowly pull the speaker cone back, and then fire it forward in a shaped pulse. I wrote a waveform generator in Java, but unfortunately found that the speaker wouldn’t follow the form. Instead, the cone moves in one “bounce” which pulls the smoke ring back into the cannon before it can detach and fly away. Either the audio synth in my computer or the amplifier itself filtered out most of the signal’s very-low-frequency components, distorting my waveform beyond any use. So I ended up using regular sawtooth waves, which work, but the only parameter to play with is the frequency. More work is needed.

These cannons will work only in still air; a breeze will break up the vortex structure. In general, faster and smaller vortices dissipate sooner than slower and larger ones. In a controlled, still environment, a big, slow vortex can travel a long distance.

The cannons are primarily meant for fun, and to illustrate the physics of the vortex. Any potential practical uses come from their ability to convey a blob of anything that’s about the same density as air through space, including things like bad smells, tear gas, or pepper spray. But with these, there is easily as much risk to the launcher as there is to the target.

Meanwhile, I am wondering whether it’s possible to launch a ring vertically, laden with a fine flammable powder such as powdered creamer, to form a flaming donut.

Happy vortexing!

Project Steps


This simple cannon, which you can make in 5 minutes, is a good way to get started.

Prepare the trash can

Cut a 6″ hole in the bottom of the trash can. That’s it — you’re done! Now you can fill the can with fog from the party fogger and generate vortexes by thumping on the lid.

Build the diaphragm

The trash can’s lid will only take this abuse for so long before it cracks and falls apart. You can replace it with a snappy new plastic diaphragm.

Start by gathering the center of a trash bag or tarp around a ball and using a small bungee cord to tie it off into a knob.

TIP: A light thump makes a slow-moving vortex, while a hard thump makes a fast-moving but less stable vortex.

Attach to the can

Duct-tape the diaphragm all around the top of the can with the knob in the center, leaving some slack.

Stretch the large bungee cord across the handles. To fire, pull back and release the knob.

NOTE: You can experiment by cutting the hole larger. This makes larger vortexes that move more slowly.


This computer-controlled cannon was inspired by Bill Beaty’s Amateur Science website.

Attach subwoofer

Tape a 12″ subwoofer into one end of a 12″ cardboard tube.

Wire it up

Wire the speaker to an amplifier, and wire the amp to your audio source. I used a laptop running Tone Generator.

Create the vortex

Cut a plywood or foam ring for the exhaust end of the barrel, with an inside diameter between 4″ and 6″. Glue and tape it into place. This ring creates the vortex, and controls its size and velocity.

Let 'er rip

Fill the barrel with fog and play sawtooth waves in the 1Hz to 10Hz range. Admire your vortices. Experiment with the frequency; when it gets too fast, the rings blur together and lose their structure.