Electromagnetic rail guns "on brink of fruition"

[Preacherman]

NOTE: I've provided conversions from Metric units into American in parentheses where necessary.

From Janes Defence Group (http://www.janes.com/defence/land_forces/news/idr/idr050429_1_n.shtml):

29 April 2005

EM gun on the brink of fruition for land and sea applications

After more than two decades of research, the science and technology behind electromagnetic (EM) rail guns has now advanced sufficiently to allow practical exploration of novel military applications, according to Dr Harry Fair, director of the Institute of Advanced Technology (IAT) at the University of Texas (UT).

Speaking at the IQPC Future Artillery 2005 conference held in London in March, he told delegates that in the field of pulsed-power supplies, capacitor technology can now be considered mature, but still requires an excessive volume for land applications. Pulsed alternators are therefore emerging as the preferred option at relatively low risk and (particularly in the context of a ship) ensure a very large volume magazine. For shore bombardment, the high terminal velocities achieved allow small kinetic-energy penetrators to put as much energy on target as larger explosive-filled projectiles and at greater ranges.

The US Navy is initiating what Dr Fair characterised as "a significant science and technology programme for ultra long-range artillery", noting however that "gun life and high-acceleration tolerant guidance, navigation and control (GNC) will be critical issues". He added: "When successful, EM guns will provide overwhelming lethality and significantly improved survivability and logistics at unprecedented ranges."

UT-IAT has devised a common low-cost projectile concept for both naval surface-fire support and army non line-of-sight (NLOS) engagements using an EM gun launcher. It has a flight mass of 15 kg (33 pounds) and contains either multiple kinetic-energy flechettes or a smaller number of sub penetrators made of tungsten. In its naval guise it has a muzzle energy of 64 MJ; a muzzle velocity of 2,500 m/s (8,125 fps); a maximum range in excess of 500 km (312½ miles) and an impact velocity of 1,600 m/s (5,200 fps). From a more size-constrained land tactical platform it would be expected to have a muzzle energy of 20 MJ; a muzzle velocity of 1,400 m/s (4,550 fps) and an impact velocity of 700 m/s (2,275 fps) out to ranges in excess of 100 km (62½ miles).

 

[DelayedReaction]

The US Navy is initiating what Dr Fair characterised as "a significant science and technology programme for ultra long-range artillery", noting however that "gun life and high-acceleration tolerant guidance, navigation and control (GNC) will be critical issues".

Yeah, gun life is one of the main reasons that railguns haven't hit off. Railguns are incredibly inefficient, as most of the energy is lost as heat due to electrical resistance. Most of this heat is transferred directly to the rails, and dramatically corrodes them. It's like taking an arc welder and running it across the surface of a metal bar.

 

[CleverName]

I've read that if the rails aren't machined perfectly parallel, the "bullet" can fuse to a rail.

Violently.

So I'm still a little wary. We've got centuries of technological development behind chemically-driven arms. Let's work out the kinks on the EM ones before we replace chemicals.

 

[cidirkona]

I heard of idea's instead of using a Lorentz' type to use a series of coils which a rod in tube passes through the middle of. Sure, the inductance induced by the coils would slow the whole process, but if you made enough small coils and used high enough voltage, you'd get back most of that energy back and wouldn't ever have to deal with arcing or sliding across the conducting material? You could use lasers to figure out where the rod was and which coils to electrify, or, neutralize by shorting as most efficient would be to have all coils ahead of the rod electified. I take it that it wouldn't be legal to attempt to build a electromagnetic slingshot?

-Colin

 

[hcker2000]

You can build them. I'v seen a fair amount of home made ones before on the net. Heck I would some day (read: when I have the extra cash) like to make my own.

The rails heating up are a problem but the balistic is ment to heat up do to air friction. This is so that the air in front of the bullet is super heated enough to melt mettles. This alows for easy penitration of tanks and other units. Some may think that it wouldnt do much to a tank to just poke a whoal right threw it but think about when the bullet with the super heated air in front of it passes threw one of a normal tanks rounds blamo gose the tank.

 

[Control Group]

Maybe I'm just missing something (wouldn't be the first time), but wouldn't this have to be a direct-fire weapon? I mean, sure, 312 miles is a long way inland, but if the round is just falling, it's only going to hit with terminal velocity. Not that I'd want to get hit in the head with a tungsten dart at terminal velocity, but it seems to me that explosives would still be a worthwhile effect multiplier in that scenario.

The immense muzzle velocity and the associated kinetic energy would make an explosive charge superfluous in a direct-fire situation, absolutely. But how often is shore bombardment from a ship a direct-fire situation at targets 312 miles inland? I can see this being an incredible anti-ship weapon, but not as effective as traditional cannon for bombardment purposes.

Or am I just being dumb, and missing something really, really obvious?

 

[hcker2000]

The one's I have seen talked about were not intended to be used a long range weapons. They were for tanks and boats (for I'm guessing boat to boat and boat to shorline). I think what eventualy will happen is now that we have computers that can calculate things very fast is that we will shring the size of the balistic to maby the size of a sure fire flash light or so and then have the computer target critical things (ammo storage on ships and tanks, engens, any thing else u might want).

 

[Bwana John]

NOTE: I've provided conversions from Metric units into American in parentheses where necessary.

FYI
64 megajoule = 47,203,979 foot pounds
20 megajoule = 14,751,243 foot pounds

 

[Daniel T]

Or am I just being dumb, and missing something really, really obvious?

You wouldn't slow to terminal velocity if you fired in an arc. A projectile would have to expend its momentum and start falling back to earth before it'd slow to terminal velocity. You might not be able to get a classic rainbow arc with a rail gun that you could with a mortar, but remember, 312 miles of range is beyond the horizon, so firing at that range by definition would be non-LOS, wouldn't it?

 

[Tinker]

Saw a TV documentary about rail guns back several years ago. The thing had like a 2" square bore and shot a metal (copper?)covered plastic cube. For safety the crew had to evacuate the all the nearby buildings before firing it remotely. The target was a 3" thick steel plate. The back stop was a huge, thick steel dray packed with hundreds of phone books. When it fired it blew through the target and actually moved that huge back stop. It also shot what looked like a bolt of lightning out after the projectile. It was awesome to see a tiny chunk of plastic blow through that much steel. Boogles the brain to think of what later developements could do.

 

[fletcher]

Yeah, gun life is one of the main reasons that railguns haven't hit off. Railguns are incredibly inefficient, as most of the energy is lost as heat due to electrical resistance. Most of this heat is transferred directly to the rails, and dramatically corrodes them. It's like taking an arc welder and running it across the surface of a metal bar.

Yep. One of my professors is doing research on improving the life of the barrels. From what he was saying, they would only last for 10 shots or so (with the current way they're designed).

 

[Vern Humphrey]

Maybe I'm just missing something (wouldn't be the first time), but wouldn't this have to be a direct-fire weapon? I mean, sure, 312 miles is a long way inland, but if the round is just falling, it's only going to hit with terminal velocity.

"Direct fire" means fire that is controlled by the gunner, from the gun position.

"Indirect fire" is fire controlled or observed from some position other than the gun.

Neither of these has any effect on impact velocity. To get an impact at "terminal velocity" you'd have to fire the gun straight up, and eventually its velocity would decay to zero, and it would fall back to earth, accelerating under the force of gravity until it reached terminal velocity -- which would depend on the mass and shape of the projectile and the thickness of the atmosphere -- which would be very thin for most of the trip back to earth!

In its naval guise it has a muzzle energy of 64 MJ; a muzzle velocity of 2,500 m/s (8,125 fps); a maximum range in excess of 500 km (312½ miles) and an impact velocity of 1,600 m/s (5,200 fps).

In other words, some person or sensor system could locate a target more than 300 miles from the gun, and the projectile would hit with an impact velocity of over 5,200 fps -- slightly more than the muzzle velocity of a cuttent M1A2 tank round.

 

[Preacherman]

They're obviously designing this thing to be effective in the bombardment role as well as for direct-fire use. If you consider the muzzle velocity quoted, and the impact velocity, it's clear that this gun's projectile would cover the maximum range listed (312½ miles) in a little over 4 minutes (which is moving some! ). That's a lot faster than a ship-fired missile like a Tomahawk could cover the same distance. This would make ship fire effective against a moving target, particularly with terminally-guided munitions. Given the weight of the projectile at that impact velocity, the kinetic energy generated would be pretty awesome.

Also, the barrel life can be completely removed from the equation if they perfect current experiments using magnetically "floated" projectiles. These would be tube- or rail-fired, but would never touch the tube or rails, as they'd be suspended in the air on magnetic fields. The heat generation aspect would still be a problem, but there'd be no direct friction involved.

 

[chris in va]

I'll be glad when we can totally do away with projectiles.

 

[Vern Humphrey]

I'll be glad when we can totally do away with projectiles.

You're a shill for the ammo companies, aren't you? This is all a plot to get us to switch to guns we can't handload.

 

[shotgunner]

My Quake 2 Railgun owns everybody!

 

[Waitone]

Fleet anti-cruise missile defense?

 

[DelayedReaction]

Also, the barrel life can be completely removed from the equation if they perfect current experiments using magnetically "floated" projectiles. These would be tube- or rail-fired, but would never touch the tube or rails, as they'd be suspended in the air on magnetic fields. The heat generation aspect would still be a problem, but there'd be no direct friction involved.

Not really. Although friction has a lot to do with it, most of the heat stems from the arcing between the rail and the projectile. It's identical to an arc welder, if not worse because of the extreme currents involved.

I heard of idea's instead of using a Lorentz' type to use a series of coils which a rod in tube passes through the middle of.

They're called coilguns, and they're much less powerful. The advantage offered by railguns is that they can transmit so much force with no moving parts.

Yep. One of my professors is doing research on improving the life of the barrels. From what he was saying, they would only last for 10 shots or so (with the current way they're designed).

Who's your professor, and where is he working?

 

[Joejojoba111]

If your prof is for real, then don't tell us his name or else he Won't be working anymore!

If the heat is generated by electrical resistance, then the solution is easy. Just mix in fullerenes into the equation. Carbon Nano Tubes are the most conductive substance known, so conductive that 1 molecule chain could transport all the electricity to power a city. !

And they are already using them (not long chains, but ugly tangles of short chains, like a pile of worms) in cars in bumpers and gas lines, gas lines particularly because they are there to reduce static electricity build-up.

And you can make the crude CNTs with 2 pieces of charcoal and some current. A little household electricity passes between the 2 chunks and the smaller one is vapourized, leaving a pile of ash lots of which is CNTs.

 

[Crosshair]

Another problem is the incredible ammount of electrical energy required to make suck a weapon work. Chemical energy like gunpowder is easy to store. Electrical energy is very difficult to store in any great quantity. This the greatest barrier to such weapons. Without fussion power of some sort, these weapons will remain a novelty.

A good example can be seen with electric cars. A half ton of batteries still can't keep up with a few gallons of gasoline in terms of energy storage.

 

[UnknownSailor]

These type of guns are one of the many technologies that would be helped tremendously by room temperature super-conductors.

That I anxiously await a PC with a room-temp superconductor CPU is obvious, no?

 

[chopinbloc]

"Direct fire" means fire that is controlled by the gunner, from the gun position.
"Indirect fire" is fire controlled or observed from some position other than the gun.

sorry, but i must disagree. the terms have nothing to do with the position of the gunner but with the trajectory of the round. i'm with a FA unit and i can tell you that direct fire means the round travels a relatively straight line while indirect fire follows a parabola. consider - a mortar crew operates the weapon from the gun position, yet it is considered indirect fire. i have witnessed a direct fire mission with 155mm paladin self propelled howitzers; (awesome sight) this is where they lower the tubes to just above zero elevation and pound away at targets only a few hundred meters away. in combat it is used as fpf (final protective fire) when the enemy is about to overrun your position.
on another note, one of the most interseting ideas i've heard for em guns is to use them to fire miniature ramjet or scramjet engines. you can make these engines very small because they have no moving parts and they can accelerate to absolutely insane velocities. the practical result is that your rounds efectiveness actually increases as the rang does. obviously accuracy decreases without a guidance package, but for larger targets that isn't always as important, plus we already have experience with laser guided artillery projectiles (copperhead) so we know we can put a guidance package in a small space.

 

[Gifted]

Someone on another forum mentioned an experiment where they used two tapering rails and shaped charges. Set off the explosives to squeeze the rails together, and they push the projectile out at 20,000+ FPS. Single use only, but it would make a heck of a LAW replacement if you could keep from blowing up the operator. Or I wonder if a gun breech could handle something like this.

They're called coilguns, and they're much less powerful. The advantage offered by railguns is that they can transmit so much force with no moving parts.

I can't see a moving part that a coilgun would have that a railgun would not.

 

[Ivy Mike]

For shore bombardment, the high terminal velocities achieved allow small kinetic-energy penetrators to put as much energy on target as larger explosive-filled projectiles and at greater ranges.

I told you light and fast was the way to go!!!!

Slow and Heavy..pssh

 

[Brett Bellmore]

Someone on another forum mentioned an experiment where they used two tapering rails and shaped charges. Set off the explosives to squeeze the rails together, and they push the projectile out at 20,000+ FPS.

Yeah, you generate electricity by pushing a conductor through a magnetic field. The stronger the field, and the faster you push it, the more power you get. What you've got there is a one shot electric generator, powered by the explosives, directly coupled to a regular style railgun. Smaller than carrying around a rail car full of capacitors, but it only works once, and it's not very healthy to stand next to.