Railgun project still alive.

[Omeganian]

http://news.discovery.com/tech/navy-sci ... 20131.html

A theoretical dream for decades, the futuristic railgun -- which uses magnets to shoot bullets for hundreds of miles at speeds of up to Mach 7 -- just took another step toward reality.

Military supply company Raytheon announced Monday that it had been awarded a $10 million naval contract to develop a way to supply enough juice to power the whopping gun -- which could someday reshape naval warfare.

"This new system will dramatically change how our Navy defends itself and engages enemies while at sea," said Joe Biondi, vice president of advanced technology for Raytheon's Integrated Defense Systems business.

Rather than relying on a explosion to fire a projectile, the railgun uses an electomagnetic current to accelerate a non-explosive bullet at several times the speed of sound. The conductive projectile zips along a set of electrically charged parallel rails and out of the barrel at speeds up to Mach 7.

But it takes a heck of a lot of electricity to achieve such a velocity.

BIG PIC: Navy Cannon Launch Breaks World Record

To supply it, Raytheon’s building a “Pulse Forming Network” or PFN. That's a large power system that stores up electrical power and then converts it to a pulse that is directed into the gun's barrel, John Cochran, the railgun program manager in Raytheon's Advanced Technology Group, told CNET’s News.com.

Navy scientists with the Office of Naval Research (ONR) have been hard at work on the railgun itself for years, even as the agency admits it could take a decade or more to become practical. The ONR hit a new milestone last fall, successfully firing the railgun for the 1,000th time on Mon., Oct. 31, in Dahlgren, Va., -- edging the state-of-the-art weapon toward real-world deployment.

The next step: turning the test versions of the railgun into an actual gun. Current firings have been limited to Naval test facilities on dry land.

The future of the railgun looked in doubt last summer. The Senate Armed Services Committee voted in April of 2011 to eliminate funding for two of the Navy’s most futuristic (and by the same token least concrete) weapons: the free electron laser, essentially a super-powered death ray, and the railgun.

That changed on Dec. 31, 2011, when President Obama finally signed into law the National Defense Authorization Act for Fiscal Year 2012, or H.R. 1540. A section in that bill demands an update on the feasibility of the electromagnetic railgun, but doesn't kill the weapon outright.

Instead it delays the end, requiring the Secretary of Defense to submit a report this summer on the feasibility of developing and deploying the electromagnetic rail gun system to be used for either land- or ship-based force protection.

[Haruko]

Sounds like the new superweapon for the plot of the next Metal Gear Solid game.

[The Romulan Republic]

Mixed feelings about this. On the one hand, I'm mostly anti-war. On the other hand, I'm generally more sympathetic towards the navy than most parts of the US military. Still, I wonder how useful this will be. It sounds like something you'd use for a battleship engagement, which haven't happened much, if at all, since WWII.

[madd0ct0r]

and they'd like to keep it that way I'd suspect

[Alkaloid]

As far as I know its being touted as a potential replacement for things like ship launched cruise missiles. it wouldn't be much use for a ship engagement simply because of the angle of fire, the rounds enter the stratosphere before falling back to earth. (In theory)

[Simon_Jester]

Mixed feelings about this. On the one hand, I'm mostly anti-war. On the other hand, I'm generally more sympathetic towards the navy than most parts of the US military. Still, I wonder how useful this will be. It sounds like something you'd use for a battleship engagement, which haven't happened much, if at all, since WWII.

Yeah, it's mostly a bombardment platform. The rounds are supposed to be guided, and relatively cheaper than an equivalent number of missiles.

The big bug in the system is figuring out how to keep the gun from burning out its barrel ridiculously fast.

[LaCroix]

The big bug in the system is figuring out how to keep the gun from burning out its barrel ridiculously fast.

Generous application of lard?
There is no way to remove this 'bug', as it is in part due to the internal working of the design (you can't put horrendous amounts of power through a piece of metal and not expect it to get hot), and the massive friction/other effects of getting the projectile to super-sonic speeds within a couple of yards. You'd need some kind of barrel-lining that gets ejected along with the projectile, but good luck with that.

[Shroom Man 777]

Why not coat the projectile in that kind of lining instead?

[Eleas]

I'm strangely happy about this. My feelings about the US military is no secret, but I can't help but hope that this means the US will at some point build a decent bulk goods launcher capable of reaching orbit.

[LaCroix]

Why not coat the projectile in that kind of lining instead?

Because if the lining is around the projectile, it protects the projectile. As this lining moves along the barrel, it fucks up the barrel just as the projectile would have.

You will need a kind of sabot to protect the projectile and a "sabot" lining for the barrel. The projectile sabot will fall off after firing, and some mechanism has to eject the barrel lining after the shot (or every x numbers of shots - it's basically a partial barrel change).

[Shroom Man 777]

I'm strangely happy about this. My feelings about the US military is no secret, but I can't help but hope that this means the US will at some point build a decent bulk goods launcher capable of reaching orbit.

[Lonestar]

The big bug in the system is figuring out how to keep the gun from burning out its barrel ridiculously fast.

IIRC the barrels of WW2 Battleships didn't have that much more of a service life than these do.

[madd0ct0r]

it's a generic artillery problem - hot barrels get droopy.

I am wondering if you could use this to shoot under the horizon.
(over the horizon would be easy, just a matter of finetuning the velocity)

I'm wondering how much of a shockwave a round would make hitting the sea? Comparable to a depth charge?
At the right angle, would your shot bounce?

[LaCroix]

it's a generic artillery problem - hot barrels get droopy.

I am wondering if you could use this to shoot under the horizon.
(over the horizon would be easy, just a matter of finetuning the velocity)

I'm wondering how much of a shockwave a round would make hitting the sea? Comparable to a depth charge?
At the right angle, would your shot bounce?

Generally, if the needed (low) elevation is possible by the gun mount, it should be able to fire LOS. There is nothing that demands the projectile to be lobbed via orbit.

I doubt the projectile being able to bounce as the contact would probably rip it to shreds. At this speeds, water is solid, so the "bounce" would behave like a ricochet against a concrete wall.

For trying to 'lob' it at an underwater target - a few meters of penetration should be possible before it disintegrates fully, so you might be able to hit a sub at periscope depth or snorkelling. Even if not, the design I know(DDX-project) was intended to have at least the power of an 155 '(maybe more, I believe shep or SeaSkimmer do have more date on the project), so the shockwave should be equal to one of these grenades exploding.

I am not completely sure about this, but I do believe that the mechanics might result in a shockwave that mostly propagates in the direction the projectile was travelling, which would make it much worse for the sub below.

Anyway, such a bombardment would definitely be bad enough to at least make them reconsider their plans, if not outright ruin their day. So you probably could use it as an OTH-ASW under the right circumstances.

[Ultonius]

If the railgun project still has the goals depicted in this image, direct fire shots out to the horizon would be possible, taking six seconds or less to arrive, while indirect fire shots could travel 200 nautical miles/230.3 miles/370.4 kilometres in six minutes. A ship armed with such a railgun could therefore take on other ships in visual range if necessary, and would be able to give fire support to troops relatively far inland, assuming it was relatively close to the shore.

[Simon_Jester]

I'm strangely happy about this. My feelings about the US military is no secret, but I can't help but hope that this means the US will at some point build a decent bulk goods launcher capable of reaching orbit.

[Osean mass driver from Ace Combat]

It's actually easier to do this than to build the gun, because you can spread out the acceleration over longer distances and abuse the barrel less.

[Eleas]

I'm strangely happy about this. My feelings about the US military is no secret, but I can't help but hope that this means the US will at some point build a decent bulk goods launcher capable of reaching orbit.

[Osean mass driver from Ace Combat]

It's actually easier to do this than to build the gun, because you can spread out the acceleration over longer distances and abuse the barrel less.

True. My point is that if mass drivers become commonplace, the concept may find much better traction among financiers (not to mention that adapting the tech itself may be far less expensive than developing it from scratch).

[Grumman]

(you can't put horrendous amounts of power through a piece of metal and not expect it to get hot)

*cough*

[SpaceMarine93]

Well what kind of coolant currently exist that could be able to remove the enormous amount of heat generated fast enough to be practical?

[Jaepheth]

Since it's not propellant driven you don't need a gas tight seal, right?

Could you have super conductive rails that levitate the projectile during its acceleration so there's no friction between the projectile and the barrel? Or would that cost more than replacing the barrel every few shots?

[Simon_Jester]

Superconductive barrels mean either liquid helium cooling (which means the entire barrel needs to be stuck in a bulky liquid nitrogen secondary sleeve, because you can't use helium as a refrigerant between 4 K and room temperature), or high-temperature superconductors (which still need a liquid nitrogen cooling sleeve, and may have undesirable material properties like shattering when hit with a shock wave).

[LaCroix]

(you can't put horrendous amounts of power through a piece of metal and not expect it to get hot)

*cough*

Yes, theoretically , you are right. You won 1 internets...

Now, how do you propose to fire a gun that has a barrel and projectile that needs to be immersed in liquid nitrogen? At sea?

Also, I'm pretty sure that they don't take mechanical abuse well. They'd probably deform so badly that the whole thing flies apart.

Superconductors will be a part of the system, but only to reduce loss between the storage condensators (don't know the actual design, but it would be logical to use these to get maximum current) and the gun itself. Every little bit of resistance removed will increase the current and thus, the power of the gun.

Well what kind of coolant currently exist that could be able to remove the enormous amount of heat generated fast enough to be practical?

The problem is that every material that can be used to construct the barrel would be red-hot after the firing. The technical process of a rail gun is similar to shorting a car battery with a spanner. (Don't try this at home!)

Only the enourmous electromagnetic force generated by the current is preventing the projectile to be arc-welded to the barrel. To be precise, it is a really fast process of welding the projectile to the barrel, breaking it loose again while the weld is still warm and soft, which causes an electrical arc that bridges the gap, which vaporizes some of the already hot metal. These ionized clouds close the circuit and act as "lubrication", so to speak. Then the fun part of accelleration begins. The whole process is very similar to pulling a million of arc-welders over the inside of the barrel. In addition to this gentle caress, it will also be heated. And as every engineer or blacksmith knows, heating a hardened material causes the atomic lattice to relax, which makes the material softer. So the material is not only removed, the material left behind is now softer, and wear will increase.

In theory, you could use something like nitrogen to cool the barrel from the outside, but it won't matter - if the gun fires, the inside of the barrel will be vaporized, or the barrel won't fire, at all. Cooling would just increase ROF.

[Terralthra]

Since it's not propellant driven you don't need a gas tight seal, right?

Could you have super conductive rails that levitate the projectile during its acceleration so there's no friction between the projectile and the barrel? Or would that cost more than replacing the barrel every few shots?

That's called a coilgun. It has benefits when it comes to reducing barrel decay, but much higher power consumption, and for high-mass, high-velocity projectiles, has problems when it comes to switching power from one coil to the next at the appropriate time. Railguns don't require any switching, simplifying the power supply issues considerably.

[Sea Skimmer]

IIRC the barrels of WW2 Battleships didn't have that much more of a service life than these do.

They tended to last 150-300 rounds. But that’s around 10 times what a rail gun will last right now. Also the life of battleship guns was normally measured using the heaviest APC rounds they could fire which in turn would only be used against heavy enemy warships of of course, very high value; high explosive/bombardment rounds were lighter, training ammo lighter still, and didn't eat up the barrels nearly as quickly. They would also be fired with a reduced powder charge if possible, further reducing damage to the barrel. The US eventually managed to adapt the good enough 16in gun propellant, using cooler powder and IIRC wax mixed in, in the 1980s that barrel life was no longer defined by barrel erosion firing HC bombardment ammo, but rather fatigue failure of certain barrel parts from the expansion under pressure. IIRC life had gotten into the range of over 1,000 HC shells.

Still in WW2 even with a barrel being good for maybe 4-500 rounds of HE, the shear cost of the ammo as well as limited barrel life meant that it could in fact take several hours to get battleship fire support in the big Pacific battles. The navy would call between ships until they literally found the least worn gun barrel to fire a mission, and basically a general in command of a division had to call for it. The only time you could freely get battleship support was during the actual initial phase of a landing. Everything else before and after was extensively preplanned or else very slow to come. You had to basically have already had a bunch of guys die to try to take a position…

Meanwhile the USN wants railguns to be kill all weapons firing hundreds of guided shells to essentially replicate what would take an alfa strike of F/A-18s with JDAM to otherwise accomplish and then rain down call fire for MARINES. It’d be brilliant if it worked but at this stage I’d be more optimistic at the chances of a 50,000 dollar cruise missile. But a small missile, however cheap, is going to be slow as balls and the shear speed of an artillery shell is a huge advantage.

[LaCroix]

Coilguns also suffer from the fact that this design, even with optimal timing, can barely manage low double digit efficiency. Also, the physical limits are much tighter, as you must factor in switching times. After a certain number of stages (coils), you can't switch fast enough to accellerate anymore.

Railguns are only limited by the available power and barrel lenght/ability to withstand the forces.