Railguns! They are full of electricity, and that can be a problem. It seems that there are two varieties of projectile: ones that conduct by themselves, and ones that have some foil on the back: the foil turns into plasma (a plasma armature) and that conducts the electricity, driving the projectile forward.

A problem is that the rails suffer. Stuff gets blasted off of them from electrical arcing. They must be replaced, which is slow and spendy.

I propose that the rails be replaced with bolts of lightning. Often one sees lightning travel a given path in the sky several times. It is because the lightning has ionized a path which must remain for a second or two. Instead of solid rails, in the plasma railgun there will be two wires, contained within a ceramic bore. The initial pulse of electricity will ionize the wire into plasma, which will serve to conduct the electricity. The plasma armature of the projectile will mix with this plasma to some degree and conduct between the rails. Rail ablation will not be a problem because the rails will already be ablated.

After each firing, new rails in the form of new wires will be pulled down the bore, which will be cheap and fast.

It seems that another big problem with railguns is arcing between the solid rails, which hurts them and wastes energy which should be driving the projectile. To get an arc one must have a conductive medium - vacuum is a perfect insulator. If the ceramic bore contains a vacuum, the same forces which drive the projectile (and push the rails apart) should also push the charged plasma rails apart, so that stray wire ions do not contaminate the vacuum and allow an arc.

Eventually there will be a lot of metal electroplated on the inside of the bore. A stiff bristled brush on the end of a big stick might be used to clean it out.
-- bungston, Aug 02 2006

Railgun info http://www.emlsympo...ers/docs/EML065.pdf
Just a little light reading. [bungston, Aug 02 2006]

Wikipedia on railguns http://en.wikipedia.org/wiki/Railgun
Good stuff. [bungston, Aug 10 2007]

Lasers and lightning http://www.esdjourn...articles/lightn.htm
Laser-induced plasma paths as gigawatt conductors [BunsenHoneydew, Feb 29 2008]

Plasma railgun https://en.wikipedi...wiki/Plasma_railgun
Just in case anyone else sees this idea and thinks "but plasma railguns already exist". What exists is a railgun that shoots a projectile made of plasma, using solid rails. [notexactly, Mar 07 2018]

Another idea I had about railguns is about getting the projectile up to speed before entering the rails. Pneumatic or chemical propulsion would cause gas or propellant to contaminate the vacuum around the railgun and allow arcing. However, a long coilgun could be inside the vacuum, and accelerate the projectile without ruining the vacuum.
-- bungston, Aug 02 2006


1.21 gigawatts? 1.21 gigawatts? Great Scott!
-- MoreCowbell, Aug 03 2006


Would the lightning bolts still have the same magnetic properties? And wouldn’t you melt the rest of the gun?
-- deep fried ice-cream, Aug 10 2007


Hi [DFI]. Thanks for the anno.

1: Same magnetic properties. The "lightning bolts" (really wires become plasma) should conduct electricity. It is the movement of electricity which produces the impulse, which I suppose is magnetic although seems to me different from an ordinary electromagnet.

2: Rest of the gun. I envision the rest of the gun to be ceramic. That space shuttle stuff. No melting.

The wikipedia article on railguns is a lot better than I remember. It looks like it is largely new. I have linked it up.
-- bungston, Aug 10 2007


It occurs to me that rather than a metal wire (which would be electroplated to the barrel interior after the plasma cooled), a graphite rod might be better. Carbon plasma is just as good (as far as I know) and could be oxidized out of the barrel with heat and air.

The idea of avoiding ablation with a graphite rail was [Ling]'s originally, and was in an anno to one of these railgun ideals. Graphite is not strong, a property which is needed in a solid rail - with a plasma rail strength is unimportant.
-- bungston, Aug 10 2007


[A stiff bristled brush on the end of a big stick might be used to clean it out.]

[bungston], if you want to come over and clean guns sometime just let me know.
-- normzone, Aug 10 2007


[bungston] unless you accidentally create a diamond coating from all that graphite.

Wait... is that even a problem?
-- BunsenHoneydew, Aug 10 2007


Do away with the supporting structure altogether. Create your plasma rails instantaneously with one of the two following methods.

Fire two ballistic projectiles on parallel paths, trailing your wires. At the instant the wires snap taut, vaporise them and (by?) injecting your projectile from a third cannon barrel mounted between the other two.

Possible problem with non-exact straightness (gravity catenary, wind shear)

Use a pulsed laser to ionise the air in two dead-straight paths. Insert megawatts and projectile. [link]
-- BunsenHoneydew, Feb 29 2008


ooooo pulsed laser ionization! I likes! Wires are so 19th century. Lasers and railguns together at last.

I like the idea of a pulsed laser lightning summoner as well. I suspect a pulsed laser strong enough to ionize air requires a lot of energy, but if we have a railgun we have that.
-- bungston, Feb 29 2008



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