Weapon concept, vortex cannon

I have seen a few things on the air vortex cannon, which is usually a simple toy for blowing out candles from afar and other such wonders. There have been larger, more powerful cannons that have been made that can knock down small structures (that aren't bolted down). This is still quite weak, probably only making a grown human stumble or fall, and I hope to weaponize the vortex cannon.

The question is realism. Can I create a new, unique weapon from the concept of a simple air vortex cannon that can send a vortex through a human (simply breaking ribs and/or sending them flying is good too)?. How much power would I need for the vortex ring to have this force and how large would it have to be? What would be used to push the air through the chamber?

• Police made some experiments trying to deliver tear gases and paint via vortexes(to disable/mark protesters). But leakage from rings was too big, I guess droplets were thrown out with centrifugal force. Jun 29, 2020 at 22:46

No, not really.

To penetrate something is really about energy density, you have to have enough joules for the area of impact for the desired effect. This means that a penetrating weapon needs to have a good energy density and be efficient in transferring that energy to the target.

Kinetic energy density depends on the mass density and square of velocity. Unfortunately the density of the projectile of a vortex cannon is for any significant distance the same as the ambient air density, which is to say very low both in absolute terms and in comparison to human body. Similarly the speed is capped well below the speed of sound or you would in effect be building a sonic shock-wave weapon not a vortex gun. (This might actually be a useful weapon though; shock waves have lots of interesting physical effects.)

This means that beyond certain value you can only increase the kinetic energy of the impact by making the vortex bigger which does absolutely nothing to increase energy density. And since the density of air is quite low compared to typical projectile values, the energy density will start quite low as well.

Additional problem comes from the ability of vortex to impart the energy to the target. This depends on relative hardness and toughness of the projectile and the target with toughness enhanced by the relative densities of the colliding objects. Your vortex is made of air, which is neither hard nor tough and has much lower density than the targets it hits. Most of impact energy would not be transferred to the target, I think, and would instead create strong turbulence around the target.

This might be okay if the air was unable to flow around the target, but when hitting a target like a human the air is able to flow around and much of the kinetic energy will simply keep going as a chaotic vortex system behind the human.

A weapon for knocking people down might be believable.

• My father knew a physicist in the '30s who built a vortex box using the packing crate for a piano, which he would excite with a sledge hammer. It would knock the hat off a pedestrian on the other side of the street. Jan 31, 2016 at 16:49
• @WhatRoughBeast Yeah, people usually think physicists should be these boring, nerdy types, but actually "people who think up weird stuff and then go to great effort to try it out" is sometimes more accurate. Jan 31, 2016 at 22:31
• i had a feeling it wouldn't work, but either way it was a fun idea. thanks for the input, your answer was well thought-out and researched. Feb 1, 2016 at 6:57

While cool, I don't think it is possible to injure someone with such a weapon, at least, not normally.

In this question, you will see that one of the main difficulties of weaponizing water is that it does not maintain a coherent chunk (ie: it spreads out to much) and so it doesn't hold much kinetic energy for long. An air vortex weapon would suffer from this issue even more: All the energy would spread out before hitting the target.

Additionally, a quick perusing of Wikipedia showed up this video of a giant Air Vortex Cannon: it can knock over (empty) cardboard boxes at ~100 meters, this might be able to knock someone over if they are unsteady on their feet. Unfortunately, it is rather large and not man portable.

So the Air Vortex itself wouldn't be able to injure people, but...

If you filled the Chamber with a poisonous or corrosive gas (such as Chlorine, Florine, etc) you could poison someone from a distance (provided they are not prepared for this).

Is this practical? No.
Is this possible? Just Barely.

• small vortex cannon able to knock down a cinderblock wall youtube.com/watch?v=QrgTtZXuj4w Jan 31, 2016 at 15:18
• The actual force looks to be about as strong as a human giving it a really strong shove. Jan 31, 2016 at 15:20
• @Jim2B Yeah, I don't think that could do more than knock someone over. It might do some damage if scaled up though, but that could run into some into issues. I don't think it would make a terribly practical weapon. Jan 31, 2016 at 15:24
• @Amziraro The trouble is that scaling it up makes it hit a bigger area, it doesn't increase the force at any one point. Feb 19, 2016 at 12:18