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In a lot of science fiction, the advanced weaponry takes the form of guns firing directed bursts of plasma. These searing bolts of fire are classic ways to create weapons apparently rooted in science, but still fantastical and mysterious. Holy Fire!

Is it plausible, given what we know of plasma and how it works today, to create a weapon that works much like the popular concept of the plasma gun?

Assume:

  • The weapon needs to be man-portable
  • Economic and industrial practicalities are not important
  • The weapon needs to be able to engage targets at 500 meters at least. (the plasma "bolt" needs to still be coherent and deadly at that range.)
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  • $\begingroup$ I assume designs that create plasma at the desired point don't count. Plasma throwers only, rather than any plasma-creating weapon? $\endgroup$ – Rowanas Oct 30 '14 at 13:43
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    $\begingroup$ Yup, just checking. I read something once that had plasma guns whose shots that flared into life after passing the majority of the distance. I need to find it. $\endgroup$ – Rowanas Oct 30 '14 at 13:48
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    $\begingroup$ I have a vague memory of proposed weapons that create a stream of plasma as stage one, and then use that stream of plasma to send electric current to further fry the target. $\endgroup$ – trichoplax Oct 30 '14 at 14:15
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    $\begingroup$ @githubphagocyte Yes, the "Thor's Hammer" style weapons. Lightning based energy weapons. Cool, but doesn't really fit the question. $\endgroup$ – Danny Reagan Oct 30 '14 at 14:16
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    $\begingroup$ @Rowanas See: popsci.com/technology/article/2012-06/… $\endgroup$ – Danny Reagan Oct 30 '14 at 14:24
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The plasma weapons from UFO AI would work.

Essentially, plasma is generated in a chamber in the weapon, using particles of compressed gas in a magazine-like reservoir. Every time the weapon is fired, it projects those particles up and out the firing aperture of the gun, between spinnerets that hold a thin membrane of plastic. The plastic sheet or thread produced by the spinnerets is deformed by the plasma bolt, containing it and preventing it from dissipating too soon.

Picture a stone being dropped into a tub of water, with a sheet of plastic on the surface. As you drop the stone, the plastic sheet folds and wraps most of the way round the stone, preventing it from touching the water (which for plasma would represent the air it must pass through to reach the target).

Thicker and more carefully sculpted plastic would hold the plasma for longer before it burns through, giving the plasma bolt a longer range. Of course, the range is still dependent on the pressure at which the particle is fired.

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    $\begingroup$ My first thought was what about the second shot? What about a material that could reform itself after the first shot? Like a soap bubble! Now I'm suddenly intrigued by the idea of bubble guns. $\endgroup$ – Mooing Duck Oct 30 '14 at 19:36
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    $\begingroup$ A similar effect could be had, perhaps, by having a magnetic bullet in the middle of the plasma packet that holds it together. $\endgroup$ – Annonymus Jul 4 '16 at 5:41
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    $\begingroup$ @Mooing Duck You could have multiple cartridges with a reservoir of compressed gas and a plastic sheet at the end. Chambering a cartridge would magnetize it, therefore "activating the munition", and you could have a multiple shot weapon. I can already picture a straight-pull weapon using this kind of ammunition, the chamber would magnetize once closed and if the safety is off. $\endgroup$ – Hawker65 Sep 11 '18 at 16:17
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One neat possibility would be taking advantage of the fluid-like properties of plasma to fire vortex rings or spherical votrices. Range might be an issue but that is definitely a way to move cohesive bundles of one fluid (plasma) through another fluid (air). A weapon of this sort would require a gas resevoir, a plasma exciting mechanism, and a launching mechanism. This would be managable as a man sized weapon but definitely bigger than a sidearm.

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By definition Plasma is a state of super excitement of mater and can be described as a super hot gas. Well, the main problem is how to make a burst of plasma, normally many times less dense than the air, cross a significant rang of atmosphere. Let say, 100 m. As the burst exits the gun the gas start to:

  • Move up. It's hot air.
  • Chill.
  • Dissipate and melt with atmosphere.

So some sort of compress chamber will be needed, to compress the plasma to a equal pressure as the ambient, to increase the range. Even with this I can't imagine a long range or a concentrated shot for this weapon, lets say 20 m. The result would be more like slugs in a shotgun than a laser-like bolter.

Compress much more the plasma wouldn't work, because the expansion forces are proportional to the difference of pressures. A optimal balance point between pressure and burst speed need to be calculated to maximize the range and/or effect, so the gun must have a computer and these controllers.

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  • $\begingroup$ That isn't true to spheromaks. $\endgroup$ – Mephistopheles May 18 '17 at 20:00
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Where are we now:

It is possible to create Plasmoids using Dense Plasma Foci. Those can be table-pop sized and still generate "essentially the same plasma characteristics (temperature and density) as the largest plasma focus". This plasmoid has the shape of a torus, a Ring.

Now we want this rotating ring of plasma to reach the target.

If it was that easy we'd already have plasma weapons around but I'll add some thoughts on how it might work (so it is not hard science from here on).

A laser beam can be used to ionize the atmosphere between the weapon and the target which is, essentially, plasma.

If we use five laser beams in a pentagon shape this could lead to a ring-shaped tunnel of plasma in a direct line towards the target. That could help the torus retain its shape longer as it travels along this tunnel.

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You might check out the MARAUDER project. It used a magnetic ring to generate a coaxial plasma beam. Its first test was shockingly successful in sending directed plasma at a target "miles" away. After that, the whole project got locked down top-secret. That was in 1995. The project is still on-the-books (public information shows money still being spent on it). As it is not yet declassified, still being invested in, and still keeps all the details under wraps, its a good bet that at least minimal progress has been made.

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  • $\begingroup$ See this post for an expanded explaination of this. $\endgroup$ – JDługosz May 30 '17 at 21:20
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I am 52 year's old and I have been designing and building my mad inventions most of my life.

I started contemplating a plasma gun about five years ago... I designed and began construction and after some time of deliberation I decided to use a shock tube design... it consisted of a charging circuit a capacitor bank fired by an S.C.R discharging between two drilled graphite rods which are holding a magnesium wire... Inside a tea shaped burst disc sealed camber...it is holding back a high vacuum held inside a tapering barrel.... also fitted with a burst disk at the end an intersecting T-junction is fitted just before the end burst disc to allow a vacuum to be drawn a pipe leading to an on-off gas tap so the vacuum can be housed and the vacuum pump used... can be used to draw a vacuum inside the hydrogen generator system I also designed... .it pumps both hydrogen and oxygen through a flashback arrestor into the detonation chamber it is a pretty cool design and when the h2o2 detonates inside a partial vacuum its gas is accelerated and expands at a higher velocity also the plasma off the detonating wire super heats the gas vaporising the burst disc now the gas is folded by a holed ceramic disc fitted in the burst disc cavity...folded into a vortex it is drawn into the vacuum by expansion and retraction the rotation of the vortex is compressed as the vortex moves forward down the barrel reduced by the barrels shape rotational speed increases its heat by friction and reduction compression adding to the heat as it leaves through the end burst disc its heat repels the air away forming a vacuum around itself and as it has no impact friction the speed it leaves the gun is the speed it hits the target at.. shockwaves would also cause damage.

Heat from the operator's hands and body, as well as solar, would power a well-made prototype mine is OK but I have to admit I would love to have had built a lightweight good looking gun that has try-gate re-usable burst discs and an electromagnetic vacuum forming piston maybe one day...

P.S. I haven't fired mine as the construction could be unsafe so it will just be shelved until I can afford to upgrade to a firing model...I hope that my ideas have given all that can hopefully understand my explanation of the workings a need to experiment themselves either on paper or models..be cool..

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    $\begingroup$ This is excellent un-punctuated writing. I like tearing people's bad science apart around here, but I read through this twice, and I'm not even sure what to criticize. I'm 50% convinced this guy made a real plasma gun. $\endgroup$ – kingledion Aug 20 '18 at 1:01
  • $\begingroup$ Please use paragraphs. Unformatted stream of conscious is very hard to understand. $\endgroup$ – Leliel Aug 20 '18 at 1:46
  • $\begingroup$ Question: is my plasma gun illegal the projectile has limited mass but very high forward and rotational velocity....? $\endgroup$ – Michael Roberts Aug 23 '18 at 10:24
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I would rather provide thoughts about the reasoning of the usage of plasma weapons in general.

What if plasma weapons are inferior to projectile weapons and more expensive? They wouldn't be built and therefore never exist in a sci-fi world. A weapon which is destructive, has slow moving projectiles and is not lethal is of no real use on ground combat, unless causing injury and terror becomes a priority in future warfare - or policing.

Another consideration is that while plasma weapons are being developed, projectile weapons will also enjoy technological advancements. They could be able to fire around corners, have automated aim/aim assist, contain special payloads, etc. For large scale weaponry there are Gauss cannons and missiles.

So plasma weaponry has to be superior in at least many regards if you want it to be sufficiently often used.

For that they have to be either somewhat effective yet cheap to build, have immense destructive force in ground combat or have other advantages. They must be able to compete well enough against projectile weapons.

One example: Armors in general have been improved vastly, which render kinetic damage inferior. People in these armors (which became generic use) shrug of incoming hails of bullets and only suffer some recoil. Even if the area in which lethal injury occurs is heavily reduced, it's still worth it (as of lighter versions of such armor). The projectiles are either deflected or absorbed, but do not cause significant injuries. Explosive/kinetic damage may also be simply absorbed without too much trouble. However, the material used should be vulnerable to heat/plasma. But dismissing the protection from projectile weapons can never be afforded given what they would be capable of.

Plasma could however not only pierce such protection, but still be effective against unarmored targets. It would have to be able to pierce armor and the body covered by it.

Now, how it should occur is more technical and I will not go into that here. @Rowanas gave a good answer for that. My point is just that no matter what, it has to be able to compete well with projectile weapons in order to justify its existence. Why would aliens or humans use plasma weaponry if it wouldn't be better than projectiles? Just look at Star Wars - plenty of pew-pew weaponry with slowly moving shots, all of which could be deflected with light sabers. That's very badly thought-out. Mere WWII weapons would have been more effective.

The same goes for Star Gate - the Goa'uld only use energy weapons, even though they can travel through space and have extensive knowledge about the universe. It's simply inferior to the weapons of humans (in ground combat), even though they are considered to be oh-so primitive.

Don't repeat the same mistake and implement inferior, yet energy based weaponry! Make them reasonable and powerful.

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I recently thought of surrounding the bolt in the chamber with some form of particles to contain the plasma, which would last to a given range before dissipating. But now I'm trying to find a way to make that sound plausible instead of a hand wave. It's a start.

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I can't remember where I read it but something that bends into this territory is a "blaster shot" of laser/plasma. Scientists have recently figured out/tested a way to fire a burst of light and have wavelength and refraction interplay and create a self-reinforcing bolt like a vortex ring. Damage dealt by the laser weapon would be in the form of plasma.

Edit: I didn't find the paper but I did find the name of the relevant effects, Self-focusing and filament propagation. Related to piping laser over distances is this paper.

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    $\begingroup$ Any claim of "scientists figured out" should be attributed to a source. There is a lot of bad science reporting in media where scientific claims are vastly misinterpreted and exaggerated for more dramatic headlines. $\endgroup$ – Philipp Dec 13 '14 at 13:29
  • $\begingroup$ @Philipp Agreed. But I was researching recent advances in various branches of science and looking at papers. As you can expect after a few weeks "recent advances" became an entirely different set of research papers and I couldn't find it. It was US government research however from after 2000, I think it was fusion research. I can provide a link to an older paper with older techniques though: ll.mit.edu/publications/journal/pdf/vol05_no1/… $\endgroup$ – Black Dec 13 '14 at 22:30
  • $\begingroup$ I do remember that the wave was expanding and contracting and not rotating (like a helix or vortex would) if anyone cares to look for it (3+ hrs and I still can't find the paper) $\endgroup$ – Black Dec 13 '14 at 22:37

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