Gun Question

TommyVercetti · July 2003

<div class="IPBDescription">About Railguns...</div> Okay, I'm writing a fanfic but I need some extra info to add a touch of realism; how much recoil would a man-portable railgun generate, and would it make a bright blue line like in the movies? I recall someone posting that they had seen one fire, and as most of the people on these forums are rocket scientists compared to those I could ask IRL, please tell meh!

Salty · July 2003

Rail gun just means it uses electiricity and magnets instead of chemical explosives for propelant. So the recoild I guess depend on how much momentum the projectile has after it has left the gun when they shoot. They have the potential to get projectiles to greater speeds but that dosent mean it has to have more recoil then a chemical weapon firing the same projectile. One of the benifts to having a rail gun over convential means though is that they can fire oddly shapped rounds. As for thouse varpor trails I don't think they happen in real life a supper sonic shock wave though yeah.

Marik_Steele · July 2003

Salty's right, it depends on the intended velocity of the round. Look on Google and you'll find people who've made magnetically-launching railguns in their garage, but don't expect them to fire at relativistic (i.e: near-lightspeed) velocities like in the movies. A railgun capable of putting a golfball-sized metal ball in earth orbit would likely have considerable recoil.

Frikk · July 2003

I seem to remember having a conversation with one of my physicist acquaintances shortly after the movie "Eraser" was release. He came to, as I remember, the conclusion that the force required to produce the velocity detailed in the movie would take approximately the output of all the nuclear power plants on the earth (or North America, I can't remember). The alminum slugs would into sort of a plaza, because of the air friction. Lastly, the recoil would knock Arnie out into space for a while. He said he was laughing really hard when Arnold started firing two at once.

Burncycle · July 2003

I have a question.

If you have a serious of magnet like donouts like so (with a projectile at the end.)

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>CODE</b> </td></tr><tr><td id='CODE'>| | | | | | <
^ projectile</td></tr></table><span class='postcolor'>

and one magnet is turned on, and as the projectile approaches, it's turned off, then the next is turned on (etc).

Why is there recoil?

I know every action has an opposite reaction, but each magnet is only boosting the projectile slightly so the force generated towards the rear is minimal if at all. The magnet and the projectile are attracting each other; but the magnet is anchored so it cannot move, so the thing that CAN move (the projectile) is perceived to accelerate with little if any force going the opposite direction right?

And whats the difference between a coilgun and a railgun? Do they operate on the same principle, or a different one?

TommyVercetti · July 2003

Okay, let me be a little more specific: what I need it to do for meh fanfic is fire straight through most walls and infantry/aliens but expend all of its kinetic energy on a heavy armored vehicle as an anti-armor shoulder-mounted weapon. Recoil would definitely be a problem... Perhaps I'll just use the excuse of future technology to dampen it down to about what the Noisy Cricket does in MiB...

Gree · July 2003

Rail guns are fun!!!!!
You can build one by following these easy steps:

1. Buy an 8x8 piece of glass
2. Cover one side of the glass with aluminium foil then the other side( be sure the foil isn't touching)
3. Get 2 metal rails and place them parallel
4. connect one of the rails to the aluminium foil(be sure only one is attached)
5. Connect the positive side of a battery to one piece of the aluminium foil then the negative side to the other
6. Wait for the aluminium to have a good charge.
7. Place a small metal object between the rails.
8. Put on electical gloves and connect the other rail to the side that the first rail is not connected to.
9. Observe as the small metal object is hurlted in a shower of sparks out of the rails.

I saw eraser too. Me and my dad worked out if you ignore the friction from air. You could fire that gun 8 times and reach escape velocity!!!!

TommyVercetti · July 2003

Stupid me. I always thought those blue trails were real, that they were air turned to plasma by the sheer friction of the projectile passing through it, as seen in games like MechWarrior 4 and Tiberian Sun.

Talesin · July 2003

Odd... I always thought that the blue corkscrew-trails were actually the projectile pulling along a bit of excess supercoolant from the accelleration series. Though it'd just be odd with it corkscrewing unless the projectile were rifled.. after all, it never touches the magnets, or it'd have a far greater chance of simply turning into a thin layer of iron-foil on the coils.

And yes.. the magnets are anchored. But they're anchored to something that is only held steady by *you*. It's the whole equal-and-opposite-reaction bit, and is pretty simple if you draw a parallel to a normal gun.. the recoil doesn't come from the explosion inside, and only partly from the expelled gasses. It more comes from the kinetic force transferred to the bullet.

Oh, and just for a bit of 'realism' in the fanfic.. it'd make a whipcrack sound when firing.

Silver_Fox · July 2003

er .. it was a movie ..

-_-

sheena_yanai · July 2003

yeah thats true.. ..newtons 3rd axiom says actio=reactio... a railgun with that power will possible rip off your arms and go airborne.. even when you just use a tiny projectile... and its not possible to accellerate it to close lightspeed.. like in some movies ( i dont say any names ) hypersonic speed is possible.. but the air friction will evaporize your bullet before its in your target..
and the stuff they showed in movies isnt not even close to realism... its just fiction... there are physical laws you know <img src='http://www.unknownworlds.com/forums/html/emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif'>

oh..yeah and there where some railgun projects.. but the smallest i know was mounted on a truck trailer that was fixed to the ground with heavy concrete blocks... and the magnetic rails where junk after this one test shot(later models where able to shot some more times).. the power you have to put it is also very high(1.6 million amperes of current). they have given the projectile so much momentum it went at short range trough a tank,and sucked on the opposite side the sheep dummys through the exit hole and left a very long bloodsplat..
sounds nice..but is very inpractical..

Jasp · July 2003

Took we awhile to find this again but its a comparisen between eraser and a real railgun <-- i know lots of typos but i like em

<a href='http://www.scienceweb.org/movies/eraser.html' target='_blank'>http://www.scienceweb.org/movies/eraser.html</a>

UZi · July 2003

yeah check this webpage out

<a href='http://www.intuitor.com/moviephysics/eraser.html' target='_blank'>http://www.intuitor.com/moviephysics/eraser.html</a>

Im a physics student...

and um...your friend is right...tho arnie would come apart if they used such a big weapon.

DOOManiac · July 2003

if (fiction) then style > realism

Smoke_Nova · July 2003

My boy...ahhh, you shouldn't have Railguns in a fanfic. They simply won't work, bad aim, ok recoil, hard to lug around.

a Guass Rifle is what you want. Computer controled with micro-magnets to fire and give the shot the turn. It's the standard weapon of any good 'Mech pilot. Hell, my Bushwhackers in MC2 carry them. You can also see a Guass Rifle in Fallout 2. It's small, minute recoil, and good aim.

TommyVercetti · July 2003

Thanks for the help, guess I'll just make it something like this: <a href='http://world.guns.ru/sniper/sn46-e.htm.' target='_blank'>http://world.guns.ru/sniper/sn46-e.htm.</a>.. Unless you think in about 500 years the tech will be refined enough to justify a shoulder-mounter version.

[edit] Me goes to research Guass (Gauss?) guns in response to SmokeNova's post. [/edit]

Burncycle · July 2003

I suppose you could have lead countershot or some other way to compensate, but that adds to the weight significantly plus it would take precise timing....

But seriously, there's no way the projectile is going to displace enough air for you to get sucked out the exit hole, thats a common myth even with modern APFSDS rounds. If I'm wrong, I stand corrected, but I need to see that to believe it.

It would probably superheat the air around it though, meaning once you penetrate something like a tank, metal particles that came off during the penetration would ignite and follow the round into the tank

I wonder if you could make a baby ramjet projectile <img src='http://www.unknownworlds.com/forums/html/emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif'>

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'>Thanks for the help, guess I'll just make it something like this: <a href='http://world.guns.ru/sniper/sn46-e.htm..' target='_blank'>http://world.guns.ru/sniper/sn46-e.htm..</a>. Unless you think in about 500 years the tech will be refined enough to justify a shoulder-mounter version.</td></tr></table><span class='postcolor'>

thats pretty much the best AMR today. I don't see why you can't have a shoulder mounted version. The barret M-82A2 is a shoulder mounted version of the popular M-82.

Smoke_Nova · July 2003

It can go either way. Guass is easier to type for me.

But my friend is a 'Mech fanatic. He's researched Gauss/Guass rifles AND railguns and he prefers Gauss. Because it can rifle (rotate to make accurate) the round while it's being fired it doesn't have to be a traditional bullet shape - you can have the Tungsten Ferrite rounds of the 'Mech's.

X_Stickman · July 2003

i thought that a Railgun used chemical explosives (like a normal bullet) and then used magnest to speed it up even more? I'm probably wrong though. And, because of how strong the magnest would have to be to propell a bullet to that speed, when they're turned on, wouldn't they buckle the gun and tear all the other magnets off?

Josiah_Bartlet · July 2003

Speaking of rail guns.

In my GCSE Double Science paper there were two extremely bloody stupid questions.

One was about growing algae on something and then attaching it to balloons so it could grow better in the upper atmospehere so we can feed Africans with it, or something like that.

The other was that someone came up with the idea of sending a rail gun to the moon and then mining the moon for aluminium and shooting the aluminium balls back to Earth using this rail gun.

I almost wet myself laughing.

X_Stickman · July 2003

"Yay! super fast mining! I sure am smart!"

"But you've killed half of the population of Africa with your super charged bullets of Moon Ore. And the other half is dying out because they can't reach the baloons with the algae on, which isn't very good to eat anyway."

"Oh. plan b. SHOOT A LAZAR MACHAINE AT TEH SUN AND SEE WAHT HAPPANES!111"

Gree · July 2003

Does anyone here know what a capacitor bank is?

It is a a means of storing electricity. It is an insulater that has opposite sides covered in a conductor. If you discharge a capacitor bank into two rails it can propel an object forward. Amazing! No magnets necessary, though it does take many farads and volts to propel a decent sized object. The charge required can be gotten from just a few car batteries.

yoda_143 · July 2003

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> (Gree @ Jul 11 2003, 09:13 PM)</td></tr><tr><td id='QUOTE'> 1. Buy an 8x8 piece of glass
2. Cover one side of the glass with aluminium foil then the other side( be sure the foil isn't touching)
3. Get 2 metal rails and place them parallel
4. connect one of the rails to the aluminium foil(be sure only one is attached)
5. Connect the positive side of a battery to one piece of the aluminium foil then the negative side to the other
6. Wait for the aluminium to have a good charge.
7. Place a small metal object between the rails.
8. Put on electical gloves and connect the other rail to the side that the first rail is not connected to.
9. Observe as the small metal object is hurlted in a shower of sparks out of the rails.  </td></tr></table><span class='postcolor'> 
Does this work at all ?
If this is meant seriously plz try to explain how to do it in a more precise way plz, I would love to try it out.

Salty · July 2003

Well first you must remeber momentum is conserved in a closed system. So if you want less recoil either shoot something smaller, have a more massive gun or use somthing to cancle it out. Thats all I can think of atm. I would use the 3rd though. This is the future so slap on some reverse momentum booster thingy on the back of the gun and frag some aliens.

On a diffrent note about those vapor trails: so thats fuggin why? I honestly never thought about air friction causing them. That would be hot as hell to have vaporized lead/tungsten/DU.

Talesin · July 2003

Gauss guns are impractical at anything over about five to ten feet. They also draw just slightly less power than a rail gun, and are VERY touchy about the type and size of projectile. The barrel also has to be made of glass, and usually shatters on the first firing as the mass-coil contracts around the slug. However, it will slice through an inch of solid steel with ease. But only in those first ten to fifteen feet. Twenty, you might get the wind knocked out of you, or get a broken bone. Thirty, and it's completely ineffectual.

Repeat after me. Video games are not reality. Microsoft screwed up Mechwarrior. We want Activision back.

Oh, and yeah.. if you ARE going to include a railgun in your fic, having a gas-vent anti recoil system could be a good idea. Or even five or ten BMG blanks. Or a small pulse jet on the back, if it was hip-mounted.

SoulSkorpion · July 2003

Damn. I was going to mention gauss guns, but I've been beaten to it <img src='http://www.unknownworlds.com/forums/html/emoticons/smile.gif' border='0' style='vertical-align:middle' alt='smile.gif'>

No, these things can't fire through walls. In terms of recoil... think about the chaingun from Predator. Those things don't exist, but it looks kinda plausible.

Anyway, don't use railguns. Use coilguns. That's a railgun with instead of having the electromagnets in a line, in rails, they're coiled around the inside of the barrel. Makes for a shorter barrel for the same power. A little one could fire a coke can through a car door, a big one could fire something into orbit (with enough power).

It makes much more sense to mount it on a mech, or something <img src='http://www.unknownworlds.com/forums/html/emoticons/smile.gif' border='0' style='vertical-align:middle' alt='smile.gif'>

Trojan · July 2003

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> (X_Stickman @ Jul 12 2003, 06:22 AM)</td></tr><tr><td id='QUOTE'> i thought that a Railgun used chemical explosives (like a normal bullet) and then used magnest to speed it up even more? I'm probably wrong though. And, because of how strong the magnest would have to be to propell a bullet to that speed, when they're turned on, wouldn't they buckle the gun and tear all the other magnets off?  </td></tr></table><span class='postcolor'> 
Could be, but they whole big 'thing' about railguns is that they don't use any heat/chemical signitures. Almost all current anti-missile systems that work use the heat signiture from the rocket and track it using that. If someone were to manage to make a full-size and working railgun they could fire anything, from anywhere, to anywhere without the slightest warning for the other side. Ala MGS <img src='http://www.unknownworlds.com/forums/html/emoticons/smile.gif' border='0' style='vertical-align:middle' alt='smile.gif'>

yoda_143 · July 2003

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'>Could be, but they whole big 'thing' about railguns is that they don't use any heat/chemical signitures. Almost all current anti-missile systems that work use the heat signiture from the rocket and track it using that. If someone were to manage to make a full-size and working railgun they could fire anything, from anywhere, to anywhere without the slightest warning for the other side.</td></tr></table><span class='postcolor'>

Jep, "Almost". There are several types of pulse laser anti-missle-weapons that actually work and that are faster than a railgun ever could be.

Talesin · July 2003

Yoda, read closer. He's talking about using a railgun to SEND missiles without using propellant, to avoid the heat/turbulence signature that an engine (whether solid-fuel or otherwise) causes.

Essentially making a railgun/coilgun into a giant catapult, and loading it up with nukes, so they'd be less likely to be shot down by other anti-ballistic systems.

Burncycle · July 2003

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'>think about the chaingun from Predator. Those things don't exist, but it looks kinda plausible.</td></tr></table><span class='postcolor'>

The minigun does exist (if that is what your referring to), and you CAN fire it from the hip, although it's unlikely that you can really control it (I saw a video of kurt russel doing it for soldier, I think the first time he fell on his butt).

But the batteries to power it, plus ammo, plus gun would all be uncarryable by one person. Alas...

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'>Yoda, read closer. He's talking about using a railgun to SEND missiles without using propellant, to avoid the heat/turbulence signature that an engine (whether solid-fuel or otherwise) causes.</td></tr></table><span class='postcolor'>

Many missiles run out of fuel before reaching their target, using the kenetic energy gained from the thrust phase to maneuver terminally.

Tube artillery would work just as well if you wanted to hide the heat signature, a 155mm round doesn't emit heat, and the only real heat exerted on it is from the propellant right when it fires. I guess the friction of traveling through the air would cause some....

Anyway, contrary to what Trojan said, most anti missile systems use radar.

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