Plasma rifle

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This article is about the science fiction weapon. See also the plasma gun as used in plasma physics.

Plasma rifles are weapons often used in science fiction. They are in effect a type of raygun. Conventional firearms launch a metal projectile from a barrel using an expanding gas, but plasma weapons use a small nuclear reactor or fuel cell or other type of advanced energy storage device to power an electromagnetic accelerator that fires a stream or pulse or toroid of plasma (i.e. very energetic excited matter).

When fusion reactors exist, one potential source of weapons-grade plasma sources might be a direct tap on a fusion reactor, especially a dense plasma focus, since the natural yield of such a reactor is a hot high-speed plasma beam.

As well as rifles, several science fiction universes also contain pistol- or cannon-scale plasma-firing weaponry.

Plasma rifles should not be confused with plasma torches, which have existed for some years, and project plasma streams a foot at most, and are used to cut metal and concrete.

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The possibility of plasma rifle existing in the real world

Template:Not verified At present, plasma weapons are only hypothetical weapons, as the amount of power that they need is currently beyond the capacity of any handheld device. Plasma rifles might not be possible, as the concept of plasma-firing weapons is scientifically difficult, for various reasons:

The plasma shot out of a plasma rifle tends to dissipate in the surrounding environment within about 50 centimeters from the gun, from thermal and/or electric pressure expansion, called blooming, unless the magnetic confinement bottle is extended all the way to the target (as it was in the games Halo: Combat Evolved and Halo 2), or the particles are fired at high enough speed to reach a target before blooming occurs. This is then a particle beam more than a plasma beam.
The technology to create plasma toroids and particle beams is presently far too bulky for anything man-portable. In such a high-performance design, the plasma would have to be stored and created in highly focused magnetic bottles, such as those used in NASA's VASIMR rocket: this design has been suggested as a potential weapon design for future real human-engineered plasma weapons. For simpler designs based on plasma cutting torches, a designer could get away with using an arcjet to heat the plasma, if his power source is strong enough.
Using current technology, if a plasma beam was fired in a planetary atmosphere, it would quickly be stopped by atmospheric resistance and would make a short hot flame like a blowtorch
One virtually universal characteristic of plasma weaponry is its tendency to overheat, thus being sometimes impractical even within the context of science fiction.