Electromagnetic guns (Ein :))

kojikun · Post by **kojikun** » 2003-01-27 06:51pm

Whats preventing real usable electromagnet weapons from being developed? Powerlabs' 3KJ gauss gun was able to push a 15.5g (0.0155kg) projectile at 215m/s. The energy of the projectile was then ~350J so the efficiency of the gun is 8.6%. If we want to push a 500g projectile at equal speeds we'd get a projectile energy of 12KJ. For the same efficiency the capacitors require 134KJ to be released. What is preventing modern technology from producing such weapons on battleships? They would be utterly devastating and it seems almost trivial..

jaeger115 · Post by **jaeger115** » 2003-01-27 07:07pm

How many money did it take to develop this thing? If its cost runs into the billions of dollars, you can expect the US military to wait until costs go down. The people in our government aren't exactly cheapskates.

Post by **Sea Skimmer** » 2003-01-27 07:17pm

Cost, power supply and versatility.

As it stands the next generation of US Armor will have some form of railguns armed tank destroyer, but conventional guns will continue on. The problem with modern railguns is you can only fire solid shot from them. That makes them effective against MBT's, and almost nothing else. However the majority of targets on the battlefield are better dealt with using a HEAT, HEP or HE shell.

Exonerate · Post by **Exonerate** » 2003-01-27 07:20pm

And I think there's the power supply problem, although that might be already worked out. Railguns make wonderful anti-tank weapons

kojikun · Post by **kojikun** » 2003-01-27 07:51pm

the PL 3KJ gun cost maybe.. $1000 due to capacitor cost. But it also gets energies equal to a .22 rifle (not that its much smaller

)

Post by **Sea Skimmer** » 2003-01-27 08:24pm

kojikun wrote:the PL 3KJ gun cost maybe.. $1000 due to capacitor cost. But it also gets energies equal to a .22 rifle (not that its much smaller )

Thats great! Of course a .223 M16A2 costs about 400 dollars and doesnt need an external power supply.

The Dark · Post by **The Dark** » 2003-01-27 08:36pm

Sea Skimmer wrote:
kojikun wrote:the PL 3KJ gun cost maybe.. $1000 due to capacitor cost. But it also gets energies equal to a .22 rifle (not that its much smaller )
Thats great! Of course a .223 M16A2 costs about 400 dollars and doesnt need an external power supply.

Why would you use an electromagnetic gun that weak anyway? M16 takes multiple shots against most enemies according to an MP Captain I work with. If it could get a decent rate of fire and have the takedown of a civil war rifle (with modern range and accuracy), then that would be useful in combat.

Post by **Sea Skimmer** » 2003-01-27 10:10pm

The Dark wrote:
Sea Skimmer wrote:
kojikun wrote:the PL 3KJ gun cost maybe.. $1000 due to capacitor cost. But it also gets energies equal to a .22 rifle (not that its much smaller )
Thats great! Of course a .223 M16A2 costs about 400 dollars and doesnt need an external power supply.
Why would you use an electromagnetic gun that weak anyway? M16 takes multiple shots against most enemies according to an MP Captain I work with. If it could get a decent rate of fire and have the takedown of a civil war rifle (with modern range and accuracy), then that would be useful in combat.

Such a weapon would have far too strong a recoil to be used as a indivudal weapon. You might as well get an M-240.

Railguns are basically pointless for infantry. They provide no advantages in small arms, and recoil makes them pointless as anti tank weapons, thats why everyone stopped useing guns in the 40's and issued shaped charge weapons.

kojikun · Post by **kojikun** » 2003-01-27 10:23pm

railguns are shit as is because the lorentz force is far too weak to be of any use. Railguns are like trying to push a large train with a small motor from a remote controlled car: its an attempt to use the weakest version of available force to do something that could be done for smaller, cheaper, and be more efficient.

"True railguns" work on the repulsion between the slugs induced magnetic field and that of the rails. BETTER rail guns work on the repulsion of the slugs induced magnetic field and an external magnetic field. They're better because they use much more powerful externals fields which require less power for a given field strength. Noone will argue that the magnetic field of a lot of wire wrapped around a nail is more powerful then just a single strand of wire. An even better electromagnetic gun uses the magnetic coild to pull a slug towards it. Thats what the PowerLabs guns are, they use a single coil to bull the slug towards the coil and then te coil shuts off so the slug continues on. These are really good and cheap and easy compared to full rail guns which the navy cant even get to shoot a nail through a block of wood (not literally). Our resident coilgun maker, Hyperion, built a gun which can fire through trees and is powered by a car battery. Nice? Yes. Very. Another kind of gun is a multicoil gun which gets better results because it uses multiple stages to accelerate the slug, and it doesnt required fancy oscillators or whatever the fuck that thing is that the PL gun is hooked up to.

Conclusion: Coilguns > Railguns by alot. Cheaper, easier.. If you can use a car battery to put a nail through a three and the whole thing costs under $50 i'd say its worth it.

Post by **Darth Wong** » 2003-01-27 10:39pm

What is the point? Unless you can devise a mag-accel system, complete with power supply, which generates more power per kg than the explosive propellant in a conventional gun, a railgun is always going to be less efficient. And what's it going to solve, again? You'll still have recoil. You'll still have to use projectiles. You'll still have ballistics, wind, etc. affecting your accuracy.

The weapon of the future is the laser. That's still pretty impractical too, but at least it boasts some real capabilities that conventional guns don't already have, which is more than I can say for railguns.

Arthur_Tuxedo · Post by **Arthur_Tuxedo** » 2003-01-27 11:13pm

I can see the range, accuracy, sustained fire, and weight advantages of lasers, but would they really be all that damaging? I mean, you'd have to hit someone in the brain or heart to put them down, since you don't get the concussive effects from a conventional weapon, right?

Post by **Darth Wong** » 2003-01-27 11:14pm

Arthur_Tuxedo wrote:I can see the range, accuracy, sustained fire, and weight advantages of lasers, but would they really be all that damaging? I mean, you'd have to hit someone in the brain or heart to put them down, since you don't get the concussive effects from a conventional weapon, right?

If the laser is powerful enough, it can blow a hole through steel. A laser like that would do a good job on a human head.

kojikun · Post by **kojikun** » 2003-01-27 11:21pm

how efficient are lasers? how much power in versus power out?

Post by **Sea Skimmer** » 2003-01-27 11:22pm

Darth Wong wrote:What is the point? Unless you can devise a mag-accel system, complete with power supply, which generates more power per kg than the explosive propellant in a conventional gun, a railgun is always going to be less efficient. And what's it going to solve, again? You'll still have recoil. You'll still have to use projectiles. You'll still have ballistics, wind, etc. affecting your accuracy.

The weapon of the future is the laser. That's still pretty impractical too, but at least it boasts some real capabilities that conventional guns don't already have, which is more than I can say for railguns.

Railgun ammunition doesn't explode when hit, and it's easier to keep a fuel fire out of the crew compartment. Survivability is an important aspect of armored vehicle design.

Post by **Darth Wong** » 2003-01-27 11:32pm

Sea Skimmer wrote:Railgun ammunition doesn't explode when hit, and it's easier to keep a fuel fire out of the crew compartment. Survivability is an important aspect of armored vehicle design.

True, but its energy draw will be its own problem. It will tax the motor of a tank, it will require a much bulkier gun because of the electromagnets, and the gun will be much more delicate because it requires powered systems all along its length; it can't just be an inert piece of metal sticking out from an armoured turret. And if you want the kind of acceleration you need to get the job done, you're looking at superconducting magnets, which in turn requires liquid-nitrogen cooling, which in turn ... well, you get the idea. Messy.

Post by **Sea Skimmer** » 2003-01-27 11:47pm

Darth Wong wrote:
Sea Skimmer wrote:Railgun ammunition doesn't explode when hit, and it's easier to keep a fuel fire out of the crew compartment. Survivability is an important aspect of armored vehicle design.
True, but its energy draw will be its own problem. It will tax the motor of a tank, it will require a much bulkier gun because of the electromagnets, and the gun will be much more delicate because it requires powered systems all along its length; it can't just be an inert piece of metal sticking out from an armoured turret. And if you want the kind of acceleration you need to get the job done, you're looking at superconducting magnets, which in turn requires liquid-nitrogen cooling, which in turn ... well, you get the idea. Messy.

I think they've notice the issue of barrel size; the released concept art generally shows very heavy barrels.

Engine power is unlikely to be a problem, your freeing up a lot of space and weight by reducing the ammo to a 12 inch dart and sabot that can be placed in a bustle autoloader safely. Doing that with normal ammo works, until a projectile enters the turret. At that point the whole thing explodes and throws the turret 10 meters.

FCS system is looking at an electric drive, so building in the extra power will be much simpler. Though one concept for using an existing chassis replaced the infantry compartment in the LAV-25 with capacitors and an extra power pack though.

Admiral Valdemar · Post by **Admiral Valdemar** » 2003-01-28 08:17am

Railguns are only really being looked at for naval vessels at the moment, possibly even orbital platforms in the not-too-distant future (concepts that seem ti ignore cash).

But for now I think it will be a case of bigger calibre smoothbore cannons and better munitions or AT missiles. The idea to make turrets on tanks as small as possible is also a good thing that cannot be achieved with railguns.

Additionally, coilguns, while easier to do due to lack of wear on the barrel from the armature, can only accelerate at the frequency you can change the fields of the solenoid at. They have a distinct upper limit to velocity compared to railguns hence their lack of military research.

ClaysGhost · Post by **ClaysGhost** » 2003-01-28 09:35am

Darth Wong wrote:
Sea Skimmer wrote:Railgun ammunition doesn't explode when hit, and it's easier to keep a fuel fire out of the crew compartment. Survivability is an important aspect of armored vehicle design.
True, but its energy draw will be its own problem. It will tax the motor of a tank, it will require a much bulkier gun because of the electromagnets, and the gun will be much more delicate because it requires powered systems all along its length; it can't just be an inert piece of metal sticking out from an armoured turret. And if you want the kind of acceleration you need to get the job done, you're looking at superconducting magnets, which in turn requires liquid-nitrogen cooling, which in turn ... well, you get the idea. Messy.

I agree about the power requirements, but I didn't think that railguns required electromagnets at all, in the barrel or elsewhere. They're usually very simple, just rails. There can be structural problems with the gun, in that the reaction forces exerted on the rails can cause them to buckle, and that if the projectile is too small, it can end up being welded to the rails by the current. This problem can be avoided by making the projectile surface area in contact with the rail larger, so that the current density drops, but then you have a poorly-shaped projectile as regards aerodynamics. You could spring the flats and have them drop away from the (nicely-shaped) round as it leaves the barrel - that's where many of the reliability problems are going to come in.

The advantages of railguns are increased muzzle velocity and energy, and possibly a higher rate of fire. The disadvantages, the power requirements and the structural demands are severe. The power requirements and the welding problem especially; this lot:

http://physik.htu.at/railgun/

unfortunately only succeeded in welding their projectile.

ClaysGhost · Post by **ClaysGhost** » 2003-01-28 09:40am

kojikun wrote:how efficient are lasers? how much power in versus power out?

You might expect efficiencies of 20% to 30%, assuming nobody continues to scale up laser diodes (about 90%) whilst reducing their beam size.

I found a reference to a railgun projecting ~3mm beads at 7km/sec which had an efficiency of about 10%. Neither lasers nor railguns are energy cheap when compared to chemically propelled projectiles, although both have capabilities that gas does not, and vice versa.

kojikun · Post by **kojikun** » 2003-01-28 06:04pm

AFAIK, coilguns have no frequency limit. remember, you can trigger a coil in advance so that the coil is on just as the projectile is in the right place.

Admiral Valdemar · Post by **Admiral Valdemar** » 2003-01-28 06:44pm

kojikun wrote:AFAIK, coilguns have no frequency limit. remember, you can trigger a coil in advance so that the coil is on just as the projectile is in the right place.

That's it though, there is only so fast you can do it and they are far more prone to failures than railguns which have gotten around the buckling and armature welding problem using synthetic materials lining the barrel insides. A sabot type round is also better.

Post by **Sea Skimmer** » 2003-01-28 10:51pm

ClaysGhost wrote:
kojikun wrote:how efficient are lasers? how much power in versus power out?
You might expect efficiencies of 20% to 30%, assuming nobody continues to scale up laser diodes (about 90%) whilst reducing their beam size.

I found a reference to a railgun projecting ~3mm beads at 7km/sec which had an efficiency of about 10%. Neither lasers nor railguns are energy cheap when compared to chemically propelled projectiles, although both have capabilities that gas does not, and vice versa.

Current military lasers have about 10% efficiency, with no sign of an increase. The laser F-35 is going to have, which won't be in service for years was stated to be about 10% effiecent

ClaysGhost · Post by **ClaysGhost** » 2003-01-29 05:28am

Current military lasers have about 10% efficiency, with no sign of an increase. The laser F-35 is going to have, which won't be in service for years was stated to be about 10% effiecent

What type of laser is it?

The Dark · Post by **The Dark** » 2003-01-29 12:51pm

ClaysGhost wrote:
Current military lasers have about 10% efficiency, with no sign of an increase. The laser F-35 is going to have, which won't be in service for years was stated to be about 10% effiecent
What type of laser is it?

Don't know type, but powering it for shots will be difficult. Even today's targeting lasers take a rather long time to charge for use, and a weapons-grade laser would take longer, since it needs more power and more cooling.

ClaysGhost · Post by **ClaysGhost** » 2003-01-29 01:25pm

The Dark wrote:
ClaysGhost wrote:
Current military lasers have about 10% efficiency, with no sign of an increase. The laser F-35 is going to have, which won't be in service for years was stated to be about 10% effiecent
What type of laser is it?
Don't know type, but powering it for shots will be difficult. Even today's targeting lasers take a rather long time to charge for use, and a weapons-grade laser would take longer, since it needs more power and more cooling.

You mean target designator lasers for aircraft, yes?