The interior of the coilgun, gunsling relay, slingatron, and balloon gun consists of either a vacuum or a helium gas at a very low pressure. If these contraptions are surrounded by dense atmosphere, they must be enclosed in a vacuum chamber. When the projectile leaves the chamber, a large volume of air leaks in before the valve is closed. To reduce the leak, plasma is placed between the chamber and the valve. The low density and high viscosity of the plasma reduce the leak by 3 orders of magnitude. A vacuum pump aided by a simple plasma window made by Ady Hershcovitch reduced pressure inside a vacuum chamber to 350 mTorr. Several plasma windows arranged in a row would completely eliminate the leak. Plasmatron may prove to be a better way to make plasma in large windows than electrodes used by Ady Hershcovitch.

Gas guns located in outer space will leak too much gas propellant unless they are sealed with plasma windows. The most likely application for such a gun is transportation of raw materials from the Moon to Earth orbit.

Plasma windows consume large amount of electric power, so they should be aided by silencer-shaped baffles and gate valves.


Ady Hershcovitch, "High-pressure arcs as vacuum-atmosphere interface and plasma lens for nonvacuum electron beam welding machines, electron beam melting, and nonvacuum ion material modification," Journal of Applied Physics, Vol. 78, No. 9, November 1 1995, pp. 5283-5288.

Web page at Brookhaven National Laboratory.

Plasmatron at von Karman Institute in Belgium.