Talk:Railgun

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[edit] Old comments

Also, railguns have been used to initiate fusion reactions, by firing pellets of fusible material at each other. The impact creates immense temperatures and pressures, allowing nuclear fusion to occur.

That's really interesting. Can you provide a cite?

Look at http://www.physics.northwestern.edu/classes/2001Fall/Phyx135-2/19/railgun.htm, I think that it theoretically could be used to create fusion rather than has been. I will wait until the author has a chance to provide a cite before changing the article. -- Chris Q 09:57 Apr 30, 2003 (UTC)

Hmmm, I can't remember where I first heard of the idea, but this page has a mention:

http://www.physics.northwestern.edu/classes/2001Fall/Phyx135-2/19/railgun.htm

Looks like I might have been mistaken about it having been done! I'll go through my list of railgun bookmarks to see if I can find the original reference, but will change it for the time being.

Google has come up with many links about using railguns to inject fuel pellets into certain kinds of fusion reactor, too.

http://www.google.co.uk/search?q=railgun+fusion

(beware science fiction sites!)

Lots of good links that I need to add to the page, I think...

Alaric 10:07 Apr 30, 2003 (UTC)

Hmm, given the sudden spate of edits on this new article, I'd think there had been an enormous amount of untapped interest in railguns amongst the Wikipedian crowd, for some reason. ;-) -- John Owens

Indeed! Sorry I mangled your comment, resolving the conflicts on each update was getting confusing -- Alaric 10:50 Apr 30, 2003 (UTC)

In The Moon Is A Harsh Mistress, they do not use a rail gun.
The projectiles used there are ferric vessels filled with rocks; the accelerator uses magnetism to push & pull, not the railgun effect.
--Einstein9073 21:43, 2004 Nov 19 (UTC)

There are a couple of points that I don't understand, which could possibly be :explained in the article.
Firstly, won't there be a force equal to that on the projectile pushing the :rails apart? Given the high level of force, how can they withstand this?

By being made of tough stuff (they are likely to be thick metal anyway to withstand the current without overheating) and by trying to optimise the design to ensure that the magnetic field is bunched around the projectile rather than the rails. There is also a recoil felt on the rails, but that's along the rails, the direction in which they're strongest. I will clarify the section about the physical stresses on the rails. -- Alaric 10:50 Apr 30, 2003 (UTC)

Actually, the force separating the rails is one of the greatest issues with using railguns. A tough, heat-resistent, superconductive material simply has not been found, and rails have been known to split apart in tests. Take a look at the How Stuff Works article. It's in the science section under Engineering. I also have several other sources for this, but I don't have time to cite them. CommKing 01:14, 25 March 2006 (UTC)

Secondly the article says:
Railguns only fire bullets, not shells?. Shells depend on their arrival at the target being more violent than their launching, so they can be detonated by impact without detonating in the barrel of the gun. However, being fired from an anti-tank railgun is more violent than hitting a tank (the projectile accelerates to maximum velocity in the space of a metre or two, but when it hits the tank it punches straight through and decelerates for several metres)...,
Surely a conventional shell only accelerates (at most) through the length of the gun barrel. Whereas the acceleration needed to reach 150km/s would be too much for a shell, you could reduce the current to give an equivalent acceleration of an explosively-propelled shell. Wouldn't it be more accurate to say that the advantage of a rail-gun is that it does not require an explosive shell, rather than saying that it cannot use one? -- Chris Q 10:37 Apr 30, 2003 (UTC)

You could indeed build a small railgun that is used to launch shells, yes, but I've not heard of any interest in doing so. I'll mention that. -- Alaric 10:50 Apr 30, 2003 (UTC)

The heating effect of the current in a railgun means that the projectile often leaves the barrel molten - this is clearly unsuitable for a shell.

I remember reading from somewhere that the use of railguns as artillery has been considered since World War I: the lower noise and lack of muzzle flash or smoke when firing the gun would have been a big advantage back then. -- Erzengel 11:16 Apr 30, 2003 (UTC)

I believe you might have that confusion will the original definition for railgun. It probably should be mentioned in this article that the weapons first known as railguns, short for railroad guns, are howitzers mounted on train cars, like the Paris Gun or Big Bertha. EisenKnoechel

Just to avoid any weapons country getting a patent I think I should point out that plasma windows described in http://flux.aps.org/meetings/YR97/BAPSDPP97/abs/S5800006.html and other places have obvious uses in railguns. The gun could be in a vacuum, firing through a plasma window, eliminating air friction until the projectile is released. This would reduce the damage to rails from fragments of the projectile, oxidation etc. -- Chris Q 09:48 May 1, 2003 (UTC)

[edit] Railguns in the navy

Railguns were also experimented by the U.S. Navy, but have proved impractical with the current designs. Just for all those people who don't know. -Someone named Volos.

There's a paragraph about naval railguns in the "Railguns as weapons" section, feel free to expand on it if you know any details about how research in that area's been going. :) Bryan 20:36, 5 Jun 2004 (UTC)

I've heard that the rail gun tech could also be used to lauch fighters off the deck of an aircraft carrier. DoSho 13:34, 25 Jun 2006 (UTC)

[edit] Too vague. it is postulated?

The artical says: It is postulated that the next generation of reactive armour will be impenetrable by conventional ammunition and shaped charges.

I think this is a bit vague By whom? Is this a reasonable postulation? within what limits - presumbreach the aemour.

Reactive armour only works onece It is just pieces of explosive that explode and hit the incomming projectile rective armour has nothing to do with penitration except to repell incoming shells DudtzImage:Kardos.jpg 7/21/05 1:43 EST

[edit] Railgun in Stargate Atlantis!

WOW, it is wonderful! I like it so much. Hope to see it more in the second season blasting the Wraith's heads!

[edit] Glitter Boy

A lot of us RPG players were introduced to Rail Guns by the Glitter Boy http://en.wikipedia.org/wiki/Glitter_Boy

[edit] Railguns in Video Games

I think this warrants its own heading in the article, because sci-fi doesn't really fit for me - it implies either written fiction or TV/film. Thoughts? Tiefighter 08:36, 16 Jun 2005 (UTC)

I think it doesn't. I periodically trim the list down to the most significant few, because otherwise, it would grow to the point where it takes over the article, as everyone adds their favorite reference. Weapons called "railguns" appear in a great many science fiction and video game settings. --Carnildo 17:50, 16 Jun 2005 (UTC)

[edit] Competing/alternative technologies?

Maybe it would be useful to link this page to http://en.wikipedia.org/wiki/Project_HARP (Gerard Bull's Supergun) and possibly other pages related to launching projectiles?

People can find those by looking in the article's category. ··gracefool |☺ 13:19, 19 September 2005 (UTC)

[edit] Another game with Railguns

Fallout 2 and Fallout Tactics: Brotherhood of Steel are two post-nuclear-apocalypse RPG PC games that make use of such weapons.

[edit] Recoil Issue

I read somewhere that railguns would not have a serious recoil issue due to the fact that the projectile is in effect being carried out of the barrel by the magnetic forces.

Conservation of momentum will still apply, so whatever force has been applied to the projectile will also be applied to the barrel in the opposite direction. --Martyman-(talk) 23:39, 12 November 2005 (UTC)
Sweet, thanks for clarifying that. It's always fun to learn off Wikipedia. Karmon 00:58, 1 December 2005 (UTC)


Actually, while the physics are the same (obviously), the recoil for a given projectile in a rail gun is less than for a conventional gun. All other things being equal,the accelerated mass is less in a rail gun because there is no propellant. In addition, there are more structural options for dealing with reaction forces in an electromagnetic system.

[edit] Railguns in science fiction

I have moved the scifi section to it's own article, and replaced it with a short summary. I think one of wikipedia's largest faults is the prevalence of pop-culture references drowning otherwise valid articles. Please discuss here if anyone has a problem with this. --Martyman-(talk) 22:55, 15 November 2005 (UTC)

[edit] Peaceful Use

I would assume a "railgun" placed in a coil would act much like a particle accelerator. Is there a point that a projectile would no longer "touch" the rails and be a self-sustaining moving object - presumably in a zero-g environment? On earth, perhaps putting the "coil" on an axis and forcing a tilt to use gravity as an accelerator? Basically, is there a point (much like a magnetic "engine") that the object would cease movment if placed on a designated track inside a continuous loop rail gun? (think "O") - Amejin

I don't quite get what you mean, but if the projectile stopped touching the rails then it would stop. --SHCGRA Max 12:52, 2 September 2006 (UTC)

[edit] History

If anyone is interested in adding the history of railguns into the article this paper seems to have a decent history of railguns up to the end of WW2: http://ieeexplore.ieee.org/iel4/20/15929/00738413.pdf?arnumber=738413 128.12.90.56 15:41, 20 April 2006 (UTC)


[edit] Pictures/Bullet at high speed?

At the top of the page it says the article needs more pictures theres a good one at http://images.military.com/pics/SoldierTech_Rail1.jpg i dunno whether you can use it or not thats a copyright issue. completely different topic now wouldn't a projectile fired at such high speeds as mentioned in that article melt a bullet or at least deform it? Probably wouldn't effect the penetrating abilities of a bullet to much at that speed but maybe somewhere could be gone with that... Also I think this should bump the other picture under rail guns in video games but of course im biased on that one... its just cooler http://upload.wikimedia.org/wikipedia/en/4/48/Metal_Gear_Solid_-_Metal_Gear_REX.jpg MetalGear2698 07:47, 29 November 2006 (UTC)MetalGear2698MetalGear2698 07:47, 29 November 2006 (UTC)

[edit] Glaring error - conservation of momentum

"Additionally, the recoil of a hand-held weapon is not solely dependent on the momentum of the projectile."

Yes, the recoil isn't solely dependent of the momentum of the projectile, but it's completely dependent on what comes out of the barrel. I'm studying physics at stanford, and this is a pretty clear error--the article implies that traditional guns violate the conservation of momentum principle, which isn't possible. I don't know much about guns, but I'd guess the extra recoil from gas-propelled would come from hot gas rushing out of the front of the barrel. A railgun wouldn't have this problem.

-Danny Neumann

If you read the rest of that section, it becomes clearer. If two guns have the same total recoil (ie, deliver the same impulse when fired - measured in units of momentum, such as sN), but one delivers that impulse over a longer period of time than the other, then the practical effects of the recoil will be different. The word 'recoil' is being used to refer not just to the magnitude of the impulse, but to the graph of impulse vs time over however long the gun takes to fire - which seems consistent with definitions of the word that I've seen.
If it misled you, though, that suggests that it may need to be rewritten to be clearer. I'll take a look when I have some more time. --144.136.185.68 13:50, 22 May 2006 (UTC)

Im in first year engineering, and in our standards physics problems to do with "force exherted by firing a projectile of this mass at this velocity" force exherted could be intermitedly changed with force of recoil. What im trying to say is that i agree with danny on how the article should be written, because when i first read that I also disagreed. And the following explanation is somewhat vague. Maybe only keep the part of how shock absorbers could reduce the effect of the recoil. I'm not going to change that part of the article as if i did anything it would only become more vague. -nick

It sounds to me like the way you're using the word recoil - ie, to mean 'force exerted by firing this projectile' - is perfectly consistent with the use of the word in the article. After all, this force is not solely dependent on the momentum of the projectile - it's related to it by the equation p = F*t, where p is the momentum of the projectile, F is the force on the projectile (equal in magnitude to the force on the gun, assuming no exhaust gases), and t is the time over which the force is applied. (Strictly speaking I should be integrating F with respect to t, but this approximation is close enough if F is constant.)
I strongly disagree that the paragraph should be cut down to a mention of shock absorbers. There's a real effect that it's describing - it just needs to be a little bit clearer. I've rewritten the first couple of sentences, to try to accomplish this. Has it worked? --144.136.185.68 09:00, 23 May 2006 (UTC)
I'm the guy that originally wrote in the recoil bit. Personally, I find it less comprehensible now. Let me try again. Basically, I was trying to say that perceived recoil is extremely different from the "actual" recoil impulse. Recoil impulse determines what the final velocity of the gun is--no more, no less. Recoil force, on the other hand, determines what the recoil feels like. It's like the difference between suddenly braking from 55 mph to 0, and crashing into a tree at 55 mph. The impulse is the same, since you go from 55 to 0 in both cases, but the force... Arrkhal 05:36, 24 May 2006 (UTC)
Yes, that's the effect. Although impulse is significant too - to extend your analogy, compare the effects of crashing into a tree at 55 mph with a crash at 5 mph. (You can have a ridiculously high force but, so long as the impulse is insignificant, the recoil will not be noticeable.) I'm having trouble, however, thinking up a simple way of explaining it. --144.136.185.68 11:35, 24 May 2006 (UTC)
Well, I usually prefer to use velocity and acceleration to describe recoil, rather than momentum and force. Final velocity and acceleration are really what you feel. For instance, .357 magnum in a snubnose revolver is very unpleasant, but the same load out of a full sized rifle, despite the higher velocity (and thus momentum) is extremely mild. Basically just that acceleration (and thus force) isn't much of a factor if the final velocity is low, but can be a real problem if the final velocity is high. Arrkhal 05:20, 25 May 2006 (UTC)
The simple way to explain recoil is, "every action has an equal and opposite reaction". Jason S. 02:28, 14 June 2006 (UTC)



Close to half the recoil impulse in conventional guns is from the gas being shot foreward, which is why you see muzzle breaks and rarefaction wave guns and in the other direction, recoiless guns.

energy will tell you the distance it takes to stop something, for a given force. momentum will tell you the time it takes to stop it with a given force.

"recoil impulse" and "felt recoil" is the distinction you're looking for. felt recoil is different from the physical recoil impulse because people would much rather feel a 50lb force for one second than a 5000lb force for .01 seconds, anything that spreads out the recoil force, and keeps the firce in line with the 'piston' absorbing it is a good thing. check out the HIWSHIWS, and the KRISS for examples.

the reason you feel less recoil with the rifle than the pistol, despite the higher velocity, is that the rifle absorbs less energy from the shot than the pistol will, despite gaining more momentum. Solve the M1xV1+M2xV2=0 for momentum with the M1xV1^2+M2xV2^2=2xEk for energy and you'll see. This is the same reason for example that this 20mm rifle has a 35lb weight screwed onto to the barrel. This is also the reason they tell you to keep your rifle tight into your sholder, this way the system acts more like your sholder is part of the weapon. The forces make it to your sholder during firing, insted of bullet to weapon then weapon to sholder, effectivly making the weapon heavier, reducing energy transfer.

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