rail/coil guns

[Funkatronic]

I'm in the process of doin a sci-fi story..

would a rail gun or a coil gun the size of a rifle be feasable???(for weapons, not propulsion)

[SlartyB]

Originally posted by Funkatronic
I'm in the process of doin a sci-fi story..

would a rail gun or a coil gun the size of a rifle be feasable???(for weapons, not propulsion)

Since it's Science Fiction - of course you can !!

But seriously, it would be a bit of a push at the moment from a technological point of view, but it could be done. The main issue is that chemical explosives are still the easiest and most economical way of accelerating a projectile to a high velocity - right now.

[talldude]

Originally posted by Funkatronic
I'm in the process of doin a sci-fi story..

would a rail gun or a coil gun the size of a rifle be feasable???(for weapons, not propulsion)

I think it would have to be powered by cold fusion or something similar, but yes, it is feasible. The US military has already made a railgun, but then again, it wasn't exactly hand held...I believe it was mounted on a tank (IIRC).

[!shira!]

the gun itself could be handheld but the power supply wouldn't

[nova]

Originally posted by talldude


I think it would have to be powered by cold fusion or something similar, but yes, it is feasible. The US military has already made a railgun, but then again, it wasn't exactly hand held...I believe it was mounted on a tank (IIRC).

Try a battleship.

The only one ever made militarily useful(and this was only on the edge of useful) had to be mounted on a ship.

I found this out when myself and some friends of mine built a small rail gun our senior year in high school. We could only shoot a BB about a foot or two and we had to have 3 dozen 1 farad capacitors and a huge power supply to do that.

Thats the main thing that prevents hand held rail guns. If a power source is ever developed that is small, light, and can deliver both high voltage and high ampage then it is possible to have a hand held rail gun.

[Strogian]

How about one of those mini-fuel cells?

[Funkatronic]

from what I've seen, railguns are tough to build...but coil guns are a bit easier, though will never have quite as much potential...

[russ_watters]

Fuel cells don't create nearly enough power. There is nothing short of a handheld nuclear reactor that could power a handheld railgun. And in any case, the laws of physics make it unlikely a person could even hold onto one. Just imagine the kick!

[SlartyB]

Originally posted by russ_watters
Fuel cells don't create nearly enough power. There is nothing short of a handheld nuclear reactor that could power a handheld railgun. And in any case, the laws of physics make it unlikely a person could even hold onto one. Just imagine the kick!

Why whould the recoil be any greater than a conventional rifle ? I agree that the power supply is the limiting factor in the feasability of a portable rail gun - but only in so far that it is difficult to deliver that much energy in such a short period of time. You don't need a nuclear reactor - just a lot of storage.

[Mayson]

Think I saw this over at [H]ard|OCP:
http://scitoys.com/scitoys/scitoys/magnets/gauss.html

you can make your own Gauss Rifle, enjoy



As for the "Kick", I think it would follow the laws of conservation of linear momentum. (Total Mass of projectile and gun)*(initial velocity) = (Mass of gun) * ( velocity of gun) + (mass of projectile) * (velociity of projectile).


If the projectile was fairly heavy and traveled extremely fast, and was fired from a light gun then you might have a problem. I think I read somewhere about the CIA (Maybe?) developing an extremely light gun made of plastics etc. so light in fact that it was lighter than the projectiles it fired. In that case, the gun had more "backwards" velocity than the projectile had "forewards" velocity.

[Blacktooth]

I recently saw a show on either TLC or a Discovery channel title Future Guns. One was a rail gun. It took up a room and fired a steel (or exotic alloy) about a foot long and looked about an inch or two diameter at 1.5 MPS! It totally demolished a large concrete embankment without any explosive warheads. The reload time was rather quick as well. The "barrel" wasn't all that long either, so I imagine the acceleration from rest to 1.5 MPS in ~10 feet of an object weighing a few pounds at least, would make quite a recoil. Amazingly enough the reload time was rather quick, a few seconds.

We won't see any "hand-held" models until some major energy producing breakthroughs occur. It took MegaWatts to power the one in the show.

[SlartyB]

Originally posted by Blacktooth
I recently saw a show on either TLC or a Discovery channel title Future Guns. One was a rail gun. It took up a room and fired a steel (or exotic alloy) about a foot long and looked about an inch or two diameter at 1.5 MPS! It totally demolished a large concrete embankment without any explosive warheads. The reload time was rather quick as well. The "barrel" wasn't all that long either, so I imagine the acceleration from rest to 1.5 MPS in ~10 feet of an object weighing a few pounds at least, would make quite a recoil. Amazingly enough the reload time was rather quick, a few seconds.

We won't see any "hand-held" models until some major energy producing breakthroughs occur. It took MegaWatts to power the one in the show.

The *energy* in the projectile is given by ....

M * V * V / 2

Assuming most of the energy consumed by the weapon was transferred to the projectile, and sing some approximate numbers from your post ....

E = 2kg * 2400m/s * 2400m/s / 2 = about 6 Million Joules.

Now, Power is defined as de/dt, I haven't got time to work out exactly how long it took to get from one end of the barrel to the other, but if it was about 2ms, the the *power* required is

6x10^6 / 0.002 = 3 GigaWatts

However ther power is only needed for a very short period of time. If it has a reload time of - say 6 seconds - the the *average* power required is ....

6x10^6 / 1 = 6 MegaWatts.

This is in agreement with the numbers in the program. Interesting ....

[Blacktooth]

If you wanna see some awesome firepower check out this technology.
Metal Storm

A million rounds a second!

[russ_watters]

Why whould the recoil be any greater than a conventional rifle ?"

The entire point of a rail gun is to fire projectiles at enourmous velocity. And that creates the kick as Mayson showed with the math.

"I agree that the power supply is the limiting factor in the feasability of a portable rail gun - but only in so far that it is difficult to deliver that much energy in such a short period of time. You don't need a nuclear reactor - just a lot of storage."

It may be true that the energy for a shot can be held in a battery the size of a car battery (I don't feel like doing the math, but if anyone wants to, feel free), but another problem is getting the power out quickly. To do that requires storing it temporarily in capacitors, which also take up a lot of space.

SlartyB, your math looked good except for the size of the projectile - much too big for a handheld gun, and the projectile speed - much too slow. But cut the size by a factor of 10 and increase the speed by a factor of 10 (and square it) and you end up with 30 GW total power output. Of course increasing the speed decreases the time, which further increases the power output...

The point all remains the same though. Kind of energy required to propel a projectile is currently best produced by an explosion. Hypervelocity projectiles are cool, but use on a small scale will probably always be science fiction.

BTW though - NASA has looked into using railguns or simple air rifles (well, not quite so simple - they would use heated, compressed H2 gas) to lauch satellites. Mount one a mile long on the side of a mountain and you can accelerate a projectile to orbital velocity. Of course the projectile has to be pretty rugged to survive the acceleration....

[mathius grey]

DERA in britain (like DARPA in the US) made one years ago, but it was the size of a house!