# A reliable coilgun?



## Omnis (Jan 28, 2012)

While a staple of much science fiction, one factor that would seem to inhibit coilguns and railguns from widespread military use is their relative lack of durability vis-a-vis conventional firearms. Being electro-magnetically powered, both of them could theoretically be vulnerable to the kind of breakdown that characterizes a lot of electronic devices from time to time. Countermeasures employed against such weapons in the future could probably include such crippling phenomena as an Electro-Magnetic Pulse (EMP). How well would they function if exposed to solar radiation? 

Anyway, I thought of a way this kind of thing MIGHT be overcome, thereby making coilguns and railguns just as durable as chemically-powered firearms. What if these guns were human-powered. We are all familiar with the hand-cranked radios often used in the event of power failures (which are also said to be immune from EMP and solar radiation). Why not power a coilgun or railgun in the same way? The human power, in this case, could be generated by pulling the trigger, delivering a single, massive jolt of power all at once to get the projectile flying. While at present there might be some engineering difficulties involved, these could theoretically be overcome in the future. handheld coilguns and railguns, could, therefore, be rendered just almost as durable and immune from power failure as chemically-powered firearms. 

Any other barriers to this concept that I might be overlooking?


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## Vertigo (Jan 28, 2012)

Unfortunately you might run into the first (I think) law of thermodynamics. The problem is that if the only energy source is the pulling of the trigger then that is the maximum energy available for the gun and that amount of energy will not make your projectile fly very far. 

However if your gun were completely shut down until you pulled the trigger ie. no power at all flowing from the battery then it would be unaffected by an EMP. It would only have problems if the EMP happened as you pulled the trigger.


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## Metryq (Jan 29, 2012)

Vertigo said:


> It would only have problems if the EMP happened as you pulled the trigger.



I don't think that's correct—EMP can induce high voltages even in dormant circuits, blitzing many of the components. However, a futuristic weapon that fires projectiles with an electromagnetic pulse will probably be hardened and shielded already—from itself, as well as outside forces.

I'd have to check, but I think the weapons in _Old Man's War_ were EMP. With the warriors in that story, I'd be more concerned about my BrainPal™ going south from an enemy pulse. 

In other news...

I remember tinkering with the power supply to a gas laser one day at work. I thought I had drained all the caps in the parasitic repeater, but I must have missed one. Another tech shared a long workbench with me, and he saw me suddenly twitch—without making a sound—throwing the circuit over my head and into the workshop behind me. He thought I was frustrated or ticked off over some problem with the circuit.

"I just got belted, you twit!"

Nothing like tasing yourself at work!


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## Vertigo (Jan 29, 2012)

You're probably righ there Metryq and not that well up on it I must admit.

I know the feeling; years ago as a kid, in the days of valves, I was building an oscilloscope. Although I was on a nice rubber mat I managed to get one hand on the positive ht and the other on the negative (about +- 300V IIRC). Popped myself 6feet across the floor! Sorry shouldn't drift off thread but I hadn't thought about that for years 'till you mentioned yours!


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## Dave (Jan 29, 2012)

I'm asking here because I don't really know enough:-


Would the advantage of a rail gun in space be that it didn't need a chemical propellant?
(I've read that gunpowder does not need an external source oxygen to ignite, but that the cold vacuum of space would be too cold for the reaction to take place reliably.)
_However on Earth, good old chemical propellants are easier, cheaper and more reliable._

Wouldn't miniaturisation be a problem?
(You could produce sufficient speed within a railgun cannon, but to do the same thing in a portable handgun would be more difficult, though I believe the Russians have needle guns.)

You might find this old thread of interest: http://www.sffchronicles.co.uk/forum/28490-what-weapons-work-in-space.html


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## Metryq (Jan 29, 2012)

Thanks for the link, Dave. I only glanced at some of the posts, but I shall read it through later. 

Anyway, I don't think there's any particular advantage to using a rail gun in _space_, except as a type of "engine." Although there _might_ be advantages in general. And you are correct that gun powder performance can be affected by cold—even within the temperature ranges found on Earth. 

Can a "rail gun" be miniaturized? Any futurist or sci-fi writer will tell you, don't bet against the future. The more firmly one denies the possibility of something, the more likely it will turn up as a reality tomorrow. I think the "pulse rifles" in _Aliens_ were supposed to be EMP weapons, as I don't recall seeing any casings flying around. (It's been a while since I saw the movie, but there is one point when the lieutenant describes the ordnance as "caseless." Of course, the weapons could still be caseless while using a propellant-and-projectile stack like Metal Storm technology.) Deckard's pistol from _Blade Runner_ may also have been EMP, as I remember power lights on the side. And if one can get a good look at the prop, it does not appear to have an ejection port.

So, what might the advantages of an EMP weapon be? For one, the operational temperature range mentioned above. Electronics—particularly batteries—can be affected by cold, too, but there are plenty of space probes deep in the black that seem to be doing just fine. Of course, they may have a constant "body heat" keeping them going just from the power supply. In that case (or caseless as it may be), an EMP weapon may have a broader operational temp range _as long as the power supply holds up._

I think an EMP weapon may have potentially higher muzzle velocities, but there are a number of factors that can affect that. A longer barrel will produce greater velocities, as the projectile will be in the "motor" longer. (This also holds true for today's firearms—more time for the expanding gas to push the projectile.) However, you don't get something for nothing—the person holding the gun will have to tolerate greater and greater recoil for those higher speeds. 

But high muzzle velocity is not always a good thing. The Arnold Schwarzenegger film _Eraser_ features a rifle-sized rail gun. The characters talk about it having a tremendously high muzzle velocity, but then we see every target picked up and thrown a great distance—which is exactly what would _not_ happen. The higher the muzzle velocity, the greater ease with which the projectile will penetrate the target. But that's good, right? It all depends on what you are firing at—armor plating, or a soft, squishy enemy.

"Stopping power" is a non-technical term that has been debated for almost as long as Mankind has had guns. A .45 caliber slug is a very big, very heavy bullet, and typically produces slower muzzle velocities than smaller diameter rounds. However, that big, heavy bullet will generally _knock down_ the target. 

The 9mm "Parabellum" is probably the most popular round in the world. (For comparison, the .45 ACP is 11.43mm in diameter.) The 9mm is smaller, lighter, and typically produces muzzle velocities significantly higher than a .45. However, the 9mm also has the nasty tendency to penetrate (pass through) everything. Remember the scene in _The Last Crusade_, the third Indiana Jones movie, where Indy fires a Walther P38 at three Nazi soldiers fighting him on top of an old tank? That's no joke. So higher muzzle velocity is not always better—although there are ways to control it.

A 9mm FMJ (full metal jacket) will penetrate targets most easily. FMJ means the bullet is covered by copper (typically), rather than being a naked lead slug. A "hollow point" bullet is one with a dimple in the nose and cuts in the jacket around the nose so that the projectile spreads open like popcorn when it strikes a target, thus flattening and expanding the cross section. This causes the bullet to slow down more efficiently and deliver more energy to the intended target (known as hydrostatic shock), rather than passing through, which wastes energy. This sounds nasty, and is (shooting someone is not a game), but hollow points are also called "safety" rounds because they decrease the likelihood of the bullet penetrating the target and hitting unintended targets beyond. 

Even more efficient than hollow points are "frangible" bullets, which completely shatter when they hit a target. That makes frangibles sound completely useless, right? I have a video documenting a range of pistol ammunition from .22 LR up through .45 ACP. Each caliber was also tested with FMJ, hollow point and frangible. The "man-like" target was a panel of pine wood in front of a gallon water jug. Except for the very smallest calibers, all the FMJs passed completely through. Some hollow points passed through, although tended to make the water jug "explode" where the FMJs did not. The frangibles generally did not pass through at all and made the water jug explode while flipping it through the air. The big test for me was the same spectrum of ammo on a car door. Believe it or not, the .45 entered the door, but did not come out the other side—this is sheet metal and plastic. Long story short—in my estimation, the 9mm frangible was the "best" performer. While it penetrated both sides of the door, what came out the other side was a tiny fragment too lightweight to hurt anyone, let alone kill them. (The .357 and .44 magnum were overkill, in my estimation, at least so far as self-defense is concerned. Longer barrels, more recoil, more noise, more overt destruction.)

So, a high muzzle velocity alone is not necessarily good, but it can be controlled to the best advantage. The military uses many rounds even smaller in diameter than 9mm, such as the 7.62 and 5.56. Both are pointed and have a bigger charge behind them than a civilian would use in a self-defense pistol, but then they may also have to penetrate body armor. Both are also "longer" in aspect, which makes the bullet "tumble" after breaking the surface of a target. (Not the same thing as a hollow point or a frangible, but better than making a clean penetration.)

To round up: Operational temperature range may be one advantage to a hand-held EMP sidearm. Muzzle velocity alone is no advantage, but that can be controlled with the type of bullet to help deliver more energy to target—an EMP weapon might also be able to vary muzzle velocity electronically. The one other advantage might be the ability to carry more rounds because there is no casing and its associated charge (which can add up to a lot of weight).


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## Metryq (Jan 29, 2012)

Vertigo said:


> I hadn't thought about that for years 'till you mentioned yours!



The low frequency stuff, like line current, will make you dance around. But the higher frequency jolt will freeze you solid. (I threw my hands over my head only after the jolt completed its work.)


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