While something called a "vortex gun" might sound like a device from science fiction, the fact is that they have been available as novelties for years - if you've ever used a toy gun that shot out a smoke ring, then you've used a vortex gun. Lately, however, scientists from the Ohio-based Battelle R & D group have developed one that could have practical uses for people such as firefighters, exterminators and riot cops.
Vortex guns work by forcing air or another gas at a high velocity, down the inside of a cylinder. Friction along the inside of that cylinder wall slows down a thin layer of that flowing gas, causing it to roll forward on itself. By the time it exits the cylinder, it's formed into a self-contained donut shape, which it is able to maintain as it flies through the air - even when subjected to cross winds.
According to Battelle's data, a big enough version of its gun could deliver an electrically-charged ring vortex initially traveling at 90 mph (145 km/h), that would be able to maintain a speed of at least 60 mph (97 km/h) for a distance of over 50 yards (45.7 meters).
The scientists propose that if ionized air were used in their gun, firefighters could shoot it down a smoke-filled hallway or flight of stairs - the electrical charge would cause the smoke particles to clump together and cling to nearby surfaces, instead of hanging in the air. If it were loaded with a pesticide gas, on the other hand, it could be used to selectively target things such as wasp's nests, without spreading the pesticide wider than necessary. Similarly, in a riot situation, shots of tear gas could be strategically delivered, instead of drifting over the entire crowd.
A patent application for the device (which can be seen in the video below) was recently filed by the research team.