Laser Guns or Rail Gun

so railgun will be replacing the massive cannons on destroyers and battleships... yah... one problem the British navy is slowly being down sized by the stupid Labour government, which would mean no scary railguns

(british railguns would be better (sorry))

I can see the same thing in the US. As the Navy slowly de-commision's it's battleship fleet, I would think that the rail guns would have to be developed at a smaller size in order to fit on things like guided missle cruisers and what not. -Muzz

sumbled upon this thread in google searching for more info on klystron machinery... joined up to make a comment or 2...

Firstly, the air superiority fighter of tomorrow is the F22, not the F35(JSF). Sure, its ground capabilities are pathetic, but it wasnt designed to touch anything on the ground, it was designed to drop other planes, whereas the F35 is a multi-role fighter, designed to do a little bit of everything. It had to make some sacrifices in air superiority to achieve this.

[edit: F35 uses a lot of technology from the F22 design programme, but still lacks in the air-superiority department because of the compromises that were made in keeping it a multi-role fighter]

Doubt me? The F22 will down any craft before even being noticed. It has the radar signature of a bumblebee, and can peg any craft with a missile before the other craft is even within visible range. When they say "First strike capability", they arent blowing smoke in your face...

And on to the topic of Rail Guns vs. Lasers... the topic is moot. They both have severe technical drawbacks. A rail gun can be though of as little more than an electrostatic slingshot. The difference between a railgun and a slingshot, is that the energy efficiency of a railgun is something like 2%.

With all the arguments about the metal vaporizing, I have to agree with the skeptics. There is no metal or metal alloy in existance that could effectively withstand the temperatures that the armature(slug, round, projectile, whatever) would be exposed to. (In fact, aluminium would be a decent metal to alloy with for a projectile like this, but still not adequate enough) That is why you would have a ceramic sabot fastened to a conductave armature (aluminium would be ideal here). The metal would mostly burn off, but the ceramic sabot would keep its form and deliver more of its energy than a metal one would.

As for tourqing of the rails, this is a serious issue. Many of my attempts at building a rail gun have met with failure because of this force. I finally came to a conclusive solution in the form of continuously perpindicular rails (details for those who request them). But the manufacturing of this setup was such an incredible pain...

The sad truth is that rail guns are just too immature for practical application. I give humans 50 years before it becomes an easy reality (mainly because of the technology chokehold we are living in today!)

As for lasers... I definately see incredible potential for lasers mounted on aircraft/sattelies.

For infantry/armor applications, advancements in chemical projectile weapons would be the most pragmatic/potentially effective choice. I have seen what a 2kg rail gun projectile can do... and then I have seen what a shaped charge warhead can do... warhead is vastly cheaper, and does about the same damage.

Plus, I cant wait to get my hands on a flechette rifle...

[edit on 7-9-2004 by the_hoser]

why do u need a 2kg slug?
when like somthing the size of a golf ball will do?

Im not talking for use as a personal weapon, nor am I talking about use as a tank weapon. This would have to be a mounted weapon, such as an installation or a battleship.

You might thing that a small, lightweight projectile moving at an incredible rate of speed would be better, but in all reality, it would not. The problem is that, though a heavier projectile could not be accelerated to as high a velocity as a lighter one, the lighter projectile would decelerate faster than the heavier one, and would be more likely to lose too much energy to the same amount of areodynamic loss as the larger projectile. Both projectiles losing energy at the same rate, the weight/speed ratio of the larger projectile is more favorable, so it decelrates faster.

Now, before you rant about areodynamic loss, let me divulge the solution to that quip.

First, the heavier projectile would be no wider and no less areodynamic as the smaller one. It would simply have to be longer. It is not unknown to munituion designers that a longer, thinner projectile delivers more energy to the target than a broader, shorter one. And in the case of a rail gun, a longer projectile has a few other advantages.

Firstly, the area for the conductor would be longer, reducing the heat from discharge contact resistance, and improves the reusability of the rails. This --does-- add more friction to the equation, but we have conductive lubricants that can solve that problem.

Also, at the rate of speeds being achieved by a high-powered railgun, the projectile wouldnt vaporize as quickly as if it were broader.

Now, Im sure that my arguments can just be turned against me, saying "why cant the 50g projectile be a dart, then", but bear in mind, I have --built-- rail guns. I have found that, despite what you would belive to be true, heavier projectiles end up delivering more energy to the target, and thats what a weapon is all about, delivering energy to the target. The reason heavier projectiles work better is: A) More mass for heat absorbtion, so the projectile doesnt melt... B) lower friction loss because the mass/surface area ratio is better C) increased conductivity, improving the efficiency of the induction field.

As a side note, the rail guns i have constructed are nowhere near weapons grade, and the highest velocities I have achieved are around 700m/s (calculated using a two stage light-break device, and then confirming that aginst the damage done to a target cinderblock...)

My most succesful design used a continuously perpindicular rail system with the projectile being an aluminum dart and a copper jacket. the projectile weighed 670g when loaded, and ended up weighing 600g after firing (lots of copper burned up...)

And yes, the recoil was immense...

Just out of curiosity, I was wondering how much recoil would come from a personal rail gun. My specs may be way off what yours might be, but the math is right, according to my textbooks... walk down memory lane to physics class with me...

For the sake of argument, lets just say that we want a gun that shoots a 1g projectile at 10,000m/s from a rifle that has 1m worth of rails.

First, we must determine the time it must take for the projectile to leave the rails...

time = distance / speed

speed = 10,000m/s
distance = 1m
time = 1 / 10,000 = 0.0001s

Now we must determine the average acceleration of the projectile along the length of these rails...

acceleration = change_in_velocity / time
change_in_velocity = speed - initial_speed

initial_speed = 0m/s
change_in_velocity = 10,000 - 0 = 10,000m/s
acceleration = 10,000 / 0.0001 = 100,000,000m/s^2

Now we can convert that to g forces...

g_force = acceleration / gravity
gravity = 9.8m/s^2

g_force = 100,000,000/9.8 = 10,204,082G

Calculate the total amount of recoil based on the weight of the projectile, and the g forces...

recoil = g_force * weight

weight = 1g

recoil = 10,204,082 * 1 = 10,204,082g

So there ya go. Your personal rail gun puts off a shoulder-cracking 10,204kg of recoil when you pull the trigger... for reference, a winchester 8-guage, double-barrel shotgun drops ~500kg of recoil into your shoulder when both rounds fire at once, and has been known to dislocate the shoulder of even the stockiest of shooters. If 500kg of force can dislocate your shoulder, I wander what 10,000kg of force would do...

[edit on 8-9-2004 by the_hoser]

hmm yes
some sort of tripod is in order unless you PURPOSELY want to break your upper torso
hmm right i see where you comeing from i thought u were meaning like an actual cube or something.

Yes, a tripod mount of sufficient depth and strength and a gun of sufficient weight (tripod about 4m long, 1m wide, gun weighing in at 250kg) you could effectively fire the gun without losing a limb.

But there remains one more problem. No man-made material in existance can be put through 10,000,000G's and remain a solid. Most metals wont even remain a liquid, but would phase-change all the way to a gas (you thought powerlabs had a big plasma plume...) Acceleration of any object to that kind of speed is not only impractical, but impossible. Yes, the matter will be moving at 10km/s, but it wont even be solid anymore, and it wont matter! The gun would literally explode from the violent expansion of the metal particles as they phase change from a solid to a gas in the frame of one ten-thousandth of a second!!

Some ceramic materials may fare better in these conditions, but they would still not be in any condition to strike a target.

This is why I said "Bigger is better". A larger projectile would not need to be accelerated to as high a rate of speed in as short an amount of time (the gun would have to be longer). Therefore, the projectile remains intact, and delivers its energy to the target. A 100g projectile accelerated to 2.5km/s with 5m worth of rails would deliver much more energy, and wouldnt disentigrate the projectile.

Bah... you know the future of modern warfare is scalar weaponry anyway...

@the_hoser
Your calculations are on the right way, but not quite correct.

I'm a physician and a friend of mine and I did some math recently about railguns and their physics.

Let me do a couple of calculations for you.

First I'll calculate the average acceleration of the projectile while still in the barrel (between the rails). We assume that it reaches 10000 m/s muzzle velocity with 10m barrel length:

a t = 10000 m/s (equation number 1)

0.5 a t^2=10 m (equation number 2)

a being the acceleration in m/s^2 and t the time in seconds.
Solving these two equations for a and t, this gives us:

a=5000000 m/s^2 and t=0.002 s

The acceleration force is the force that must be applied to the projectile in order to accelerate it, and at the same time, this is the force the projectile has to withstand. It is:

F=m a ; with m being the mass of the projectile

Assuming we have a projectile with a mass of 0.01 kg (10grams), the force is:

F= 0.01 kg x 5000000 m/s^2 = 50000 N

That means in terms of g-forces (a somewhat misleading term), that the projectile has to withstand 509684 G's.

And this is how came to the result:
The gravitational force on the projectile would normally be:
Fg = m g ; where g is the gravitational acceleration on earth(9.81 m/s^2)
Fg= 0.01 x 9.81 = 0.0981 N

The number of G's is simply how many times the gravity is acting upon the object, hence:

F / Fg = 509684


Let's move on to recoil, the most interesting topic.

Actio = Reactio means if you are applying a force on something, it "pushes back". When a glass of water is standing on the table, the glass pushes against the table with the amount of its gravitational force and with the same force, the table is pushing against the glass. If this isn't the case, the glass of water falls through the table.

With the railgun, it's the same. If the railgun is pushing against the projectile, thus accelerating it, the projectile is pushing against the railgun. It doesn't matter how the force is generated.

Let me elaborate a bit. The net momentum of the system must remain the same. At the beginning, before the gun is fired, the momentum is zero, since nothing is moving. At the end, the momentum will be zero again, because momentum can't be created. The projectile is moving in one direction, the gun in the opposite, both having exactly the same momentum. One momentum is negative (because of its opposite direction), hence when you add up the two, you get zero.

The formula for the momentum is:

P = m v ; m being the mass of the object and v the velocity

The momentum of the projectile would be:

p = 0.01 kg x 10000 m/s = 100 Ns

Let's assume that the gun has a mass of 100 kg.

The momentum of the gun has to be the same as the projectile's momentum.
If you solve the above equation for v, you get the velocity of the gun and shooter after the shot:

v = p / mGun = 1 m/s

This means that a gun weighing 100 kg will move at 3.6 km/h after having shot a tiny projectile weighing 0.01 kg at 36000 km/h. This requires a force oof 500N to stop the recoiling barrel within 10cm (just as a sidenote).

Feel free to play with the equations and try different combinations of barrel lenght, muzzle velocity, projectile weight etc. You will get interesting result.


That took me quite a long time to write! I hope everything is clear and helps clarify the physics involved a bit better. In order to find out whether the projectile will handle the acceleration, you'll have to look up the tensile strength of different materials. And this topic gets even nastier when you take into account the friction, air drag etc.!

If you would like to know something else, feel free to ask and I will try to answer. I thought I'll just cover the basic things but there are many more left. By the way, I'm not a physics professor but just a student, so I don't know everything.

Railguns are kind of impractical being charged using capacitors. A better system would have a flywheel that speed up, and dumps it's energy into a generator. This is what the US gov is doin'. I think it's called a compulsator. The US gov is paying 30.8 million dollars to have a prototype.
I have made coilguns and railguns. The coilguns i have made are far more efficient than the railgun. I got a .25 caliber steel ball to go 40 yards before. It was 20 joules at 300v. I used 4 photoflash caps, 120 uF 330v. It was only charged to 300 volts though. Thompsons coils are interesting. They work using a copper or aluminum ring , discharging a cap bank into a coil beneath the ring. eddy currents cause the ring to repel the coil, making it fly away. I haven't to build one though.

try a gauss rifle, there quite smart.
yeah railguns are difficult but not so impratical if say a massive asteroid or unkown thingy was comeing towards earth.

A gauss rifle and a coilgun are the same thing, but gauss rifle also means a gun that uses magnets that smack into more magnets so it speeds up faster and faster. Coilguns are capable of much higher velocities because the magnets you would use for a gauss rifle would break at high speed.

really? i thought a coil gun used EM not just normal magnetics.
i mean iv seen a coil of wire shoot a disc 3 inches into solid oak before that looked kool.

If it shot a disk, it was most likely a Thompson's Coil, works on repulsion. Normal coilguns create a magnetic field which pulls a piece of iron or ferrite to the coil, but turns off so the bullet will keep flying, as opposed to being sucked back if you applied a constant power source. Most people use capacitors.

I can see the same thing in the US. As the Navy slowly de-commision's it's battleship fleet,

Uhh... the US navy decommissioned all of its battle ships in 91-92 so what are you talking about we did that cuz they were obsolete and were nothing but an expensive missile launching platform. Destroyers in the future will be the ones with rail guns not battleships.

technically a battleship is one with only really guns and a rail gun is gona take up most of the ship.

"Which do you think is better? Rail Gun or Laser"
The answer to this question, as most "which is better" questions are too, is "which ever is better for the job" I mean, if you going after a Rabbit at 100 yards in a feild, a .50 Cal BMG isnt gunna be the right thing to use is it? Your gunna use a .22 Rifle or somthing along those lines. Sombody pointed out very early in this thread that The laser would be used to shoot down missles and the Rail gun would make most armour useless and do lots of killing. This sounds about right, use the right tool for the job!

Your not gunna use a hammer to put a screw into a peice of wood (unless your a complete retard!)

Get my point?? I hate to be boring and all, but you ask the question, I'll tell you the answer if I know it, or otherwise ill give you my opinion or keep my trap shut!

YAY!!! I agree! But I just figured it was no use. Really, people want to talk about their favorite and the gun's applications.
PS. Of course I never tried to use a hammer on a screw!

OOPS! I typed under my sister Katie's profile! KatieD is my sister. Sorry all