U.S. Navy Electromagnetic Railgun

[Texas Contrarian]

This is cool stuff:

http://www.onr.navy.mil/~/media/File...20Railgun.ashx

Check out the potential velocities and range.

One beautiful thing about this technology is that it would reduce the need for ships to carry large quantities of high-explosives.

[Guest032516]

What is the warhead though? The railgun eliminates the need for an explosive charge to launch a projectile, but the projectile itself can still be an explosive. right?

How heavy of a projectile can it shoot? It seems like the weight will be limited in order to get it up to 4,500-5,600 mph in a short distance.

I also assume that the warhead can maneuver once launched - rather than a straight ballistic round.

[IIFFOFRDB]

That is very cool.

[Wakeup]

The warhead is a ferromagnetic alloy rod with really good tensile strength. The warhead right now is purely ballistic and non-explosive. It doesn't need explosives. The kinetic energy of a medium mass round traveling at six times the speed of sound is equivalent to the same weight weight of a high explosive round. Kinetic energy is one half mass times velocity squared. As they say, speed kills. The weight, dependant on mass, doesn't have to be large, in increase in speed is much more desirable than an increase in weight when maximizing energy at impact.

Doing the math, they use a two megajoule rail gun. Transmuting that all to kinetic energy, if the projectile is fired at Mach 6.5, that's 2200 meters per second. 2,000,000 divided by 2200 squared, divided by one half, equals a projectile weight of .82 kilograms, or about two pounds.

It's purely ballistic because the round undergoes acceleration of approximately 60,000 gees during firing. That kind of acceleration tends to do nasty things to all types of materials, so putting an electronic guidance system and/or complicated moving parts in it is still under development.

P.S.-Most people think that US Army M1 Abrams tanks fire high explosive rounds. While we do load HIgh Explosive Anti-Tank (HEAT) rounds, our preferred round for killing enemy tanks is the Armor Piercing Fin Satbilized Discarding Sabot Tracer (APFTDS-T), commonly called the Silver Bullet. It's non-explosive as well, just like this rail gun round. It was a depleted uranium rod fired at high velocity. Damage is done by the speed, converting to energy upon impact.

[Wakeup]

Oh...for a frame of reference...

An Intel Pentium processor weighs around 23 grams. If you put one of those inside the rod as part of a computer guidance system, during the firing acceleration, that processor would weigh a bit over 3000 pounds...the plastic and gold inside the processor would crush themselves into a pretty thin paste. Now you grasp just one of the difficulties in putting a guidance system inside the rod.

[Guest032516]

Originally Posted by Wakeuр

The warhead is a ferromagnetic alloy rod with really good tensile strength. The warhead right now is purely ballistic and non-explosive. It doesn't need explosives. The kinetic energy of a medium mass round traveling at six times the speed of sound is equivalent to the same weight weight of a high explosive round. Kinetic energy is one half mass times velocity squared. As they say, speed kills. The weight, dependant on mass, doesn't have to be large, in increase in speed is much more desirable than an increase in weight when maximizing energy at impact.

Doing the math, they use a two megajoule rail gun. Transmuting that all to kinetic energy, if the projectile is fired at Mach 6.5, that's 2200 meters per second. 2,000,000 divided by 2200 squared, divided by one half, equals a projectile weight of .82 kilograms, or about two pounds.

It's purely ballistic because the round undergoes acceleration of approximately 60,000 gees during firing. That kind of acceleration tends to do nasty things to all types of materials, so putting an electronic guidance system and/or complicated moving parts in it is still under development.

P.S.-Most people think that US Army M1 Abrams tanks fire high explosive rounds. While we do load HIgh Explosive Anti-Tank (HEAT) rounds, our preferred round for killing enemy tanks is the Armor Piercing Fin Satbilized Discarding Sabot Tracer (APFTDS-T), commonly called the Silver Bullet. It's non-explosive as well, just like this rail gun round. It was a depleted uranium rod fired at high velocity. Damage is done by the speed, converting to energy upon impact.

Originally Posted by Wakeuр

Oh...for a frame of reference...

An Intel Pentium processor weighs around 23 grams. If you put one of those inside the rod as part of a computer guidance system, during the firing acceleration, that processor would weigh a bit over 3000 pounds...the plastic and gold inside the processor would crush themselves into a pretty thin paste. Now you grasp just one of the difficulties in putting a guidance system inside the rod.

Thanks for the hard numbers analysis. I figured there would be problems with any kind of guidance, because the electromechanical parts needed would be crushed by the acceleration. That's why I asked if anybody knew what kind of round it fired.

If they can't use guidance, this weapon will be of limited use. If the rail gun is long and therefore fixed, that means you have to turn the ship to aim and you have to compensate for the pitching caused by the waves. If you are aiming at something 60 miles away, you have zero room for error. So it has to be a big target - like a building and it has to be stationary.

Even in an Abrams tank, they use advance computer controls to stabilize the gun enough to accurately fire a sabot round at something only a few thousand meters away. To get real accurate, they have to stop the tank to fire.

I imagine the problems with the railgun will be an order of magnitude more complicated.

[Wakeup]

The turrets aren't fixed. They have concept videos on the website, they'll be no different than regular turret armaments on ships now.

Originally Posted by ExNYer

Even in an Abrams tank, they use advance computer controls to stabilize the gun enough to accurately fire a sabot round at something only a few thousand meters away. To get real accurate, they have to stop the tank to fire.

Actually not true. I'll admit, when I was going through 19K basic training they told us about the old M60 tanks which had a "stabilize" button which you had to be stopped to use. As tankers, we trained both defensive and offensive. Defensive shoots are stationary, offensive are moving, and there's no difference in impact point whether you're stopped or going 20 mph. The computer takes all of that into account the instant you pull the triggers. We engage offensively out to the limits of our weapon system, 4000 meters.

Trust me, it's not the tank's problem engaging on the move, it's the gunner. If we could couple our main gun to a phased array radar, or to a military GPS satellite system, the gunner problems would disappear. Don't underestimate what we can do with ballistic computers today, and a ship is a remarkably stable and/or anticipative gun platform. They're saying the rail gun can be used to intercept incoming missiles...I'll be anxious to see it.

I'm also anxious to know what the long range accuracy data is, as I haven't seen any long range targeting tests. Back in the battleship days with purely mechanical firing control calculations and wildly varying shells and charge amounts, they would hit around 4% of the time at ranges around 15,000 yards, or a bit short of three miles. Our accuracy now, using the standard 5" guns on destroyers, has improved so that they hit 60% of the time out to their limits of 15 miles using purely ballistic shells. Even sub-MOA out at 100 miles is 5300 inches...or 440 yards...not even close to hitting a house. We'll see how it goes...

[Texas Contrarian]

The Navy envisions the possibility of firing GPS-guided projectiles from a railgun:

http://www.wired.com/dangerroom/2012...sonic-bullets/

http://www.military.com/soldiertech/...soldiertech.nl

http://www.popsci.com/technology/art...ic-projectiles

http://www.tgdaily.com/security-brie...un-projectiles

[JD Barleycorn]

If you don't have the imagination Hollywood has already ran their version of what it would look like in Transformers II. A navy ship was ordered by a spook to fire their new weapon at a giant robot on top of the Great Pyramid. It is supposed to be a rail gun. There is also talk about using the same tech to launch aircraft off a carrier in the future.

[Guest032516]

Originally Posted by Wakeuр

The turrets aren't fixed. They have concept videos on the website, they'll be no different than regular turret armaments on ships now.

Actually not true. I'll admit, when I was going through 19K basic training they told us about the old M60 tanks which had a "stabilize" button which you had to be stopped to use. As tankers, we trained both defensive and offensive. Defensive shoots are stationary, offensive are moving, and there's no difference in impact point whether you're stopped or going 20 mph. The computer takes all of that into account the instant you pull the triggers. We engage offensively out to the limits of our weapon system, 4000 meters.

Trust me, it's not the tank's problem engaging on the move, it's the gunner. If we could couple our main gun to a phased array radar, or to a military GPS satellite system, the gunner problems would disappear. Don't underestimate what we can do with ballistic computers today, and a ship is a remarkably stable and/or anticipative gun platform. They're saying the rail gun can be used to intercept incoming missiles...I'll be anxious to see it.

I'm also anxious to know what the long range accuracy data is, as I haven't seen any long range targeting tests. Back in the battleship days with purely mechanical firing control calculations and wildly varying shells and charge amounts, they would hit around 4% of the time at ranges around 15,000 yards, or a bit short of three miles. Our accuracy now, using the standard 5" guns on destroyers, has improved so that they hit 60% of the time out to their limits of 15 miles using purely ballistic shells. Even sub-MOA out at 100 miles is 5300 inches...or 440 yards...not even close to hitting a house. We'll see how it goes...

Thought i had seen some videos on the Abrams where they are accurate on the move provided they are going relatively slow (10 mph?). But the top road speed is about 40 mph and the top off-road speed is about 25 mph. Are they really accurate if you are doing 20+ mph over rough, bouncy terrain?

[Guest032516]

Originally Posted by JD Barleycorn

If you don't have the imagination Hollywood has already ran their version of what it would look like in Transformers II. A navy ship was ordered by a spook to fire their new weapon at a giant robot on top of the Great Pyramid. It is supposed to be a rail gun. There is also talk about using the same tech to launch aircraft off a carrier in the future.

I think we may soon decide to get rid of carriers altogether.

See this link:

http://www.tgdaily.com/security-brie...-surface-ships

If you can land drones on small ships and you can use rail guns to launch then, then you can scatter your naval aircraft across many dozens or even hundreds of ships.

This eliminates the enormous cost of an aircraft carrier and the related problem of having a small handful of such high value targets.

Take the $5 billion we spend to build each aircraft carrier and build 10 destroyer-type ships that each service 4 or 5 drones. The annual cost of maintaining is also a fraction of the cost for an aircraft carrier.

[Wakeup]

Got a database error when that went through, or else I would have corrected the post for a math error I made. Sub-MOA at 100 miles is approximately 1800 inches, or 150 yards. Still not hitting a house in the middle of a neighborhood, but within danger close limits for indirect fire support. Anxious if the rail gun can shoot sub-MOA or not.

No tanker is actually going to take a shot while being bounced all over the turret, and trust me, I've been there, done that. We have certainly engaged offensively at 20-25mph. Fun as hell, but we're not about to pull the triggers on the cadillacs if we're not at least somewhat like a stable platform. Shooting Table VIII on the range, we rarely get above 5 mph, you're correct. Like I said though, a destroyer is a much more stable, and predictable platform than a tank is.

[chefnerd]

Why not go a little more high-tech. Seems the Navy has a new weapon to play with. Not quite what you see in the movies, but a laser nonetheless. Due to go into service in Persian Gulf early next year.

http://news.yahoo.com/navys-laser-we...215808231.html

[gnadfly]

Since one would want the nonexplosive round to go as fast a possible that anything more than a very minute change in trajectory would not be desirable.