The Physics of a Railgun

[Kirk Freeman]

Break out your whiteboards, Gun Sheldons. It's time for Phun with Physics.

Videos at link:

The Physics of the Railgun | Science Blogs | WIRED

 

[CathyInBlue]

James Clerk Maxwell is my *****.

 

[ModernGunner]

Railguns are pretty slick, as are coilguns. The 'challenge' is the massive amount of electrical current necessary.

As we learn to make more efficient use of electricity, maybe another century or so, railguns become more plausible.

That's basically the problem with electric automobiles. The batteries still aren't very efficient for their size and weight. Yet.

 

[6mm Shoot]

I think I read someplace that the Navy was using a rail gun on a ship. The claim is that it moves a shell at 5000 MPH. They may not have one that we can shoulder, but they do have one that works.

 

[T.Lex]

On a related note, the Navy is also testing a system that would replace the hydraulic launchers with EM ones. Same idea, use electricity and magnets to propel something.

Fly Navy.

 

[ashby koss]

Railguns are pretty slick, as are coilguns. The 'challenge' is the massive amount of electrical current necessary.

As we learn to make more efficient use of electricity, maybe another century or so, railguns become more plausible.

That's basically the problem with electric automobiles. The batteries still aren't very efficient for their size and weight. Yet.

Actually the issue with coil guns is the timing across th emultiple coils to get the projectile to travel forward perfectly, the electrical usage sure doesnt help the issues either.

The Railguns though are effective and usable, not just "there yet", with the railguns the issue is repeated use, the high amount of force that the rails under-go when firing can push the rails away from eachother, thus catastrophic failure over time.

The one common issue is the lack of energy, now if there was a small iron man type of arc reactor.......

 

[david890]

IMHO, the current guns are plenty good. Yeah, a railgun can supposedly send a round 100 miles or so, but at that distance, you'd need something to fine-tune the round to impact. The various forces would send ANY purely ballistic round off-target over 100 miles. After all, the Germans could shell Paris from 75 miles, but the best they could hope for was to hit the city, not a particular block or building.

If you need pinpoint accuracy (and current trends toward limiting collateral damage will likely only get tighter), use a cruise missile or smartbomb.

 

[singlesix]

IMHO, the current guns are plenty good. Yeah, a railgun can supposedly send a round 100 miles or so, but at that distance, you'd need something to fine-tune the round to impact. The various forces would send ANY purely ballistic round off-target over 100 miles. After all, the Germans could shell Paris from 75 miles, but the best they could hope for was to hit the city, not a particular block or building.

If you need pinpoint accuracy (and current trends toward limiting collateral damage will likely only get tighter), use a cruise missile or smartbomb.

You are so right. Right now there are no guided artillery shells in the current inventory. Do I really need the purple.

 

[david890]

You are so right. Right now there are no guided artillery shells in the current inventory. Do I really need the purple.

Kindly note the phrase "purely ballistic round" in my post. In other words, a "dumb" bomb, with no guidance package.

My point is, why spend $$$ for such a weapon when our current inventory is more than sufficient for any foreseeable task? IMHO, this is the Navy equivalent of the F-35, and will likely prove just another black hole for our tax money (well, we know it goes to the shareholders of the defense contractor, so I guess they want to see more research).

 

[eric001]

My point is, why spend $$$ for such a weapon when our current inventory is more than sufficient for any foreseeable task? IMHO, this is the Navy equivalent of the F-35, and will likely prove just another black hole for our tax money (well, we know it goes to the shareholders of the defense contractor, so I guess they want to see more research).

The money spent on railgun technology may well revolutionize our whole military capacity. The navy is looking at a projectile being shot at mach 7 with a range of around 100 miles. Has anyone else figured out that this range also includes knocking satellites (or ICBM's) out of space? How about the idea that a ballistic round cannot be jammed by electronic interference, and its nastiness comes from kinetic energy instead of explosives, which means it is MUCH safer to store, handle, and fire...and it is not nearly as vulnerable to countermeasures from defensive missile technologies.

I'll let the defense industries do the worrying about fine-tuning targeting at range. I'm sure they can figure it out. Probably even without relying on a phase-conjugate mirror! (Sorry, couldn't help myself.)

Now, think another step or two ahead: what about the trend of taking big weapons and making them smaller? Think about the main guns on tanks being rail guns--results much like what the Abrams gets now, but with no explosives to protect and much better range, time-to-target, and overall accuracy because of that. Another step ahead and you get crew-portable weapons that can easily defeat cover and armor defenses. Not even thinking about hand-held applications--the energies required may never allow this, or some breakthrough may make it possible at any time. Then you also get the side-effects that bleed over into the rest of society as new technologies find alternate or expanded applications. How we manage and control electricity may become just as important in today's world as doing the same with fire has been to our history.

Yeah, I'd say that is money well-spent.


For your viewing pleasure:

Navy?s New Railgun Can Hurl a Shell Over 5,000 MPH | Danger Room | WIRED

U.S. Navy unveils high-speed rail gun - Videos - CBS News

 

[roadrunner681]

The money spent on railgun technology may well revolutionize our whole military capacity. The navy is looking at a projectile being shot at mach 7 with a range of around 100 miles. Has anyone else figured out that this range also includes knocking satellites (or ICBM's) out of space? How about the idea that a ballistic round cannot be jammed by electronic interference, and its nastiness comes from kinetic energy instead of explosives, which means it is MUCH safer to store, handle, and fire...and it is not nearly as vulnerable to countermeasures from defensive missile technologies.

I'll let the defense industries do the worrying about fine-tuning targeting at range. I'm sure they can figure it out. Probably even without relying on a phase-conjugate mirror! (Sorry, couldn't help myself.)

Now, think another step or two ahead: what about the trend of taking big weapons and making them smaller? Think about the main guns on tanks being rail guns--results much like what the Abrams gets now, but with no explosives to protect and much better range, time-to-target, and overall accuracy because of that. Another step ahead and you get crew-portable weapons that can easily defeat cover and armor defenses. Not even thinking about hand-held applications--the energies required may never allow this, or some breakthrough may make it possible at any time. Then you also get the side-effects that bleed over into the rest of society as new technologies find alternate or expanded applications. How we manage and control electricity may become just as important in today's world as doing the same with fire has been to our history.

Yeah, I'd say that is money well-spent.


For your viewing pleasure:

Navy?s New Railgun Can Hurl a Shell Over 5,000 MPH | Danger Room | WIRED

U.S. Navy unveils high-speed rail gun - Videos - CBS News

but would the rail gun be dangerous to electronics near by? could this thing have serious issues with collateral damage if it misses its going to go a long way.

 

[bradmedic04]

This stuff makes me very happy. That is all.

 

[Kirk Freeman]

Well, we aim to please, brad.

 

[eric001]

but would the rail gun be dangerous to electronics near by? could this thing have serious issues with collateral damage if it misses its going to go a long way.

I would think the railgun's EM signature would be pretty well containable within its structure/housing. I agree that accuracy would be rather important with collateral damage. While thinking about both of those put together, I have to wonder if there's a way to make something like the M982 Excalibur shell for railgun use. Getting the electronics to survive INSIDE that EM field might be a tad bit tricky, but 100 mile range and self-guiding accuracy would be one heck of a combination!

 

[9mmfan]

The more rail guns the Navy can use the better. That is all.

 

[roadrunner681]

I would think the railgun's EM signature would be pretty well containable within its structure/housing. I agree that accuracy would be rather important with collateral damage. While thinking about both of those put together, I have to wonder if there's a way to make something like the M982 Excalibur shell for railgun use. Getting the electronics to survive INSIDE that EM field might be a tad bit tricky, but 100 mile range and self-guiding accuracy would be one heck of a combination!

agree they could probably take a missile down with them if they could do that.

 

[Mr Evilwrench]

With sufficient refinement, not only could one of these take a satellite out, a bit bigger one could launch satellites. This would be an insanely cheap way to LEO compared to rockets; you could put up spy or com satellites on demand, or send up fuel and supplies for a station or to stage an interplanetary launch.

As far as batteries go, there's a limit to the energy density available from chemical cells, and I'm afraid we're pretty close to it already. What we need is "Mr Fusion".

 

[eric001]

I've always wondered about how much capacitors could be used--they seem perfect for a very high output over a very short duration. The last time I looked into them even half seriously was in the late 80's (I blame the Star Wars Defense Initiative or whatever the press called it then.) Since then I'm sure a fair amount of 80's scifi has become reality, but no real idea how much has been done with these specifically.

I'd think with big enough capacitors and a power source that could cook off enough electricity to recharge them fairly quickly, you'd have a pretty viable weapon system.

 

[Mr Evilwrench]

It's possible to calculate the energy storage of a capacitor. The limitations are the capacitance, which is basically proportional to the surface area and proximity of the electrodes, and the voltage rating, which is inversely proportional to the proximity, but dependent also on the insulator between the electrodes. Like the batteries, I'm not sure how far there is left to go on these, but then the "supercapacitors" kind of took me by surprise when they came out. I'd definitely power each coil of the railgun with a large, low ESR (effective series resistance) capacitor.

 

[Kirk Freeman]

INGO brings the nerd! Finally!