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World's Most Powerful Rail Gun Delivered to US Navy
An anonymous reader writes "The world's most powerful functional rail gun capable of accelerating projectiles up to Mach 8 has been delivered to the Navy. The new rail gun is a 32-megajoule Electro-Magnetic Laboratory Rail Gun. The Navy eventually hopes to have 64-megajoule ship mounted rail guns. 'The lab version doesn't look particularly menacing -- more like a long, belt-fed airport screening device than like a futuristic cannon -- but the system will fire rounds at up to Mach 8, drawing on tremendous amounts of electricity to generate the current for each test shot. That, of course, is the problem with rail guns: Like lasers, they're out of step with modern-day generators and capacitors. Eight and 9-megajoule rail guns have been fired before, but providing 3 million amps of power per shot has been a limitation.'"
I'm vaguely remembering a conversation I had when I was in the Navy, but from what I remember, the USS Enterprise was over engineered to have 8 reactors when they knew only 4-6 were really necessary because they had some thoughts of mounting energy weapons. since the Enterprise was drawn up in the late 50's I'm not sure whether to doubt it or not.
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Mach 8 is about 9800KPH. Escape velocity from the Earth's surface is 40,320KPH. This gun is already firing at over 24% of escape velocity. A 64Mj gun would be almost 50%; a 132Mj gun would shoot projectiles right into orbit.
I wonder whether coming generations of this gun could shoot unmanned exploration vehicles or satellites out into space. The Pentagon will probably try to use it just to shoot down spacecraft, but instead we could use their budgets to increase space industry and exploration.
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I wonder how many times this thing can be fired. They need to get 32 megajoules of energy out of the gun, and without the metal that this power passes through melting. That's not an easy thing to do.
Railguns today tend to melt after each shot, leaving one to replace the rails (the biggest, conducting the part of the gun, the bit in contact with the "bullet").
I wonder what the efficiency is. 32 megajoules come in, how many leave in the bullet. (Generally they only get about 2%-5% efficiency).
An alternative, easier and safer, is a coil gun. Here's a nice index of coilguns : World's coilgun arsenal. But like their railgun brothers, they're not very efficient. The very best of them have the bullet speed of a mini handgun, but they're trivial to make, and rely only on batteries and metal.
The Enterprise was the prototype. Plus, Nimtz carriers only have 2 reactors. So it wouldn't surprise me if they overengineered her power supply for the intent purpose of mounting experimental weapons.
:P)
That being said, the Nimtz reactors are a bit more advanced than the Enterprise (lessons learned and all that), so that has a lot to do with the reduction in the number of reactors.
Everything beyond that is classified. I could tell you, but then I'd have to shoot you. (Assuming that I already knew and therefore had been shot.
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Probably not with the Apache, but Germany's Stuka dive bombers (Spanish civil war/WWII) had sirens fitted specifically for that reason.
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I had a physics teacher who used to work at Los Alamos who did some consulting for the military on the side. In the late 80's/early 90's, they had him evaluate the results of some rail-gun tests. They were shooting a small ball projectile at tanks. The projectile left a perfectly round smooth bored hole all the way through the tank, wherever it was fired. The military wanted to know if they could use this to disable things (fire through the engine block) without destroying other things (people, electronics, paperwork, whatever) inside.
In evaluating it, they found that the internal air temperature flashed to something really high (like an oven) in the microsecond the ball travelled through, and that the vaporized steel from the first surface of the tank would kill everyone in the compartment.
It brings home what kind of speeds we're talking about here.
I'm waiting until they start listing the speeds of rail guns in terms of [decimal]c. Full of relativistic goodness. Of course, if they're only at Mach 8, they've got a way to go. The X-15 was near mach 7 and the scramjet tests have hit mach 10, and I'm sure those were more massive than the rail gun's projectiles.
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As I recall, the original list of superweapons was much more impressive. It just got pared back a smidge when Congress balked at the price tag.
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Keep in mind the relationship between energy and power. Assuming the reactor on a ship can only produce a fixed amount of power there is a trade off between rate of fire and the kinetic energy of the projectile. If the user of said railgun charges the capacitor bank from a 15 amp wall outlet for five minutes the gun will be capable of firing a small projectile at a reasonably high rate of speed. But if the user charges it up over night it can fire a massive projectile at the same speed.
As far as getting the massive amount of power from the capacitor bank to the railgun itself, I am confident that the military has the capital to use some sort of superconducting material to deliver as much power as they need. I think it's likely more difficult to construct a physical "gun" that can handle the "reaction" from the projectile's "action." I suspect the Navy wants to fire very large projectiles at a very high rate of speed and isn't too concerned about how rapidly they fire them.
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The Zumwalt class destroyer (aka DD(X)) destroyers are not "the smallest serious ship the Navy floats" unless you don't consider Ticonderoga and Arleigh Burke class ships to be serious ships.
At 15,000 tons of displacement, the Zumwalt class ships are pretty damn big.
As I recall, the ship had eight reactors because that's how many it took to keep the thing moving. They were expensive and Congress wanted the Navy to go back to fuel oil. As I recall, the JFK was conventional. When the Nimitz class came about, the reactor technology had progressed to the point where they could get away with two and the operational costs came down enough that Congress relented. What the Navy really likes about nuclear is that it gives the carriers so much operational flexibility. A modern carrier has fourteen days of combat stores onboard. The reactors also produce the steam to fire the catapults, a very energy-intensive process. I also heard something about some nuke carriers carrying bunker fuel to help keep the destroyers topped off but that seems a bit silly since there are already fleet oilers to perform that task.
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The funny thing is that there are other technologies (ram accelerators, combustion light gas guns) that can reach the same velocity but without the burly power requirements. And for a fraction of the cost... And the projectile doesn't turn into plasma on the way out... And the rails don't wear out after five shots... Seriously, what I hear from people in the field is that the railgun people are scamming the government, especially when there is other cheaper tech out there that will solve this problem.
An article a while ago had a plan for a circular track a few miles wide. The launch vehicle would be magnetically accelerated along the track and on the last trip around be diverted to a straight launch rail for that last bit of acceleration to target. It was still quite a few gees sideways going around, but a lot less than achieving orbital velocity in a short straight acceleration.
Thats what I suspected.
On large ships, other kinds of weapons are preferable.
This will be more like a traditional gunboat, carrying only one primary gun. Also, as it says in the article, the recoil makes it unlikely that this gun will fire many shots in one battle.
I think this will be a bit like a naval sniper, aiming to destroy major vessels command center before its even detected, and then leave the area quickly and let the big ships take over.
So we won't see many ships with this configuration, but in certain situations, it could probably end a battle before it even gets started. That is, as we all know, the best way to win battles.
Actually, they do, and it's not that foolish when you think about it. Fleet oilers are generally too slow to keep up the battle group and require escorts of their own. The carrier can't entirely replace the fleet oiler but it does add flexibility to the options of the task force commander.
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We are the United States Government! We don't do that sort of thing.
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Well, whatever the range, speed, or lethality of those "rail guns", they'll only give further justification for asymmetrical warfare and tactics. If I were a government faced with my ships being targeted by such guns, I'd resort to deploying ships with 50 or 100 MT nukes designed to detonate when impacted by high-energy rounds. The USN had then better hit my ships SPOT ON to assure they nukes wouldn't go off.
Sheesh, talk about exacerbating nuclear proliferation. As long as ONE nation has super weapons, no other nation can POSSIBLY feel non-threatened. Doesn't matter whether the US actually USES them. It's their existence and actual deployment that is unnerving to some nations. And, it only justifies nations spending exorbitant sums of public money on otherwise phantom or unjustified war footing.
But, then, it's just a matter of time before technology for rail guns that are "good enough" hit the fleets. Now, other navies will just have to mount axial mounts and state publicly that they'll unleash as many shells as they can if they detect shock waves hurtling at their own datum point. "Shoot at me, I'll shoot indiscriminantly and with great fervor." That would create furor in world bodies, but *might* keep powerful, flag-waving navies "at bay".
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The problem occurs because you have a high current. In order to avoid welding the projectile to the rails, you must contact the rails with non-trivial area, so every projectile slides along the rails with significant contact. Rail repulsion is a separate, but still important, problem.
Arcing actually replaces the abrasion problem with an ablation problem (and a conductivity problem). Unless you mean arcing between the rails themselves, which shouldn't happen, as the solution is the same as the contact-area and general resistance solution: wider, thicker rails.
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I sat next to one of the directors of the Navy's rail gun program, during a flight to Boston, and I had one of the most interesting talks with him. The projectiles fired experience about 30,000 g's of acceleration, compared with 12,000 g's for a conventional gun. The major problem is that about 20% of the g's are experienced laterally because the projectile bounce when it is traveling down the rails. The projectiles do not contain explosives, because the kinetic energy is enough to do some pretty good damage. The materials problem with the rails was solved a while ago, and they need to survive for about 1000 shots to be comparable to today's guns. They also don't store the energy for very long before firing, because of losses and safety.
Guided projectiles can be shot down or intercepted or confused with chaff or flares or electromagnetic interference. Unguided projectiles, by their very nature, are not subject to being interfered with--and at such high speeds, it's unlikely the target would be able to see it coming. It'd take 2.2 minutesish to go the 220 mile range, so while it may not be very easy to snipe a mobile target, shore emplacements and the like would be sitting ducks.
If I had such a boat, I would use it against shore batteries, harbor fuel tanks, and other such targets--unless it had some -really- good stealth on it, in which case a bit of close-in sniping might work.
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Actually, this is not correct. There are only 3 types of nuclear powered ships currently active in the navy: Aircraft Carriers (CVN) and submarines (SSN and SSBN). There used to be nuclear guided missile Cruisers (CGN class) as well, but there were never actually any destroyers that were nuclear powered. All ships that used Nuclear Power have an "N" at the end of the class designation (hence DDG is non-nuclear powered). The reactors designated as "Destroyer" were all actually put into Cruiser type ships, and the last nuclear cruiser was decommissioned in the late 1990s. I think the South Carolina (CGN-37) was one of the last ones, I remember we had a bunch of the nukes from there that still had a bunch of sea time left come to the carrier I was stationed on (USS Theodore Roosevelt) the Destroyer reactor (D2G) was a 150 MW design, but again, this reactor was put into the CGN class
I suspect that's an urban legend. (Lots of 'em floating around the Navy.) I've never seen anything, anywhere, indicating that the Navy was looking at energy weapons in that time frame.
At any rate, the reactor plant of the Enterprise was originally sized on the need to launch full (Vigilante) sized aircraft while steaming at maximum speed. Plus some additional capacity for operational reserve, in case one or more reactors were down, plus a fudge factor for future growth and to cover against concerns about reactor performance. There was also a general concern in the Navy at the time over the profliferation of electronic systems and their increasing demands for power.
Since the reactors ended up performing reliably and more-or-less to spec, and big aircraft didn't become common in the fleet - Enterprise ended up considerably overpowered, much more so than follow on CVN's. The follow on CVN's carry fewer reactors partly because of this, and partly because the individual reactors are so much more powerful and specifically designed for carriers. (The A2W reactor used by Enterprise is actually a slightly uprated C1W reactor - originally intended to be used in pairs for cruisers.)
In fact, Enterprise ended up with so much excess steam capacity - that (IIRC) half the steam recievers (a sort of capacitor to hold steam for the catapults) she was built with have subsequently been removed. Off-and-on there has been discussion of mothballing a pair of her reactors in place.
Might the Department of Defense's recent effort and research to develop a feasible, mobile solar power source be related? The idea was to beam solar light from space using satellites and focus it onto a solar grid of some sort.
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I remember it being (potentially) 10 megawatts, which isn't quite enough to power these devices, but with enough R&D...
http://hardware.slashdot.org/article.pl?sid=07/10/14/2129233 http://blog.wired.com/defense/2007/06/post.html And there's always nuclear etc... I'm pretty sure they have a conceived way to power it if they've already gone this far with the plan.
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I also heard something about some nuke carriers carrying bunker fuel to help keep the destroyers topped off but that seems a bit silly
I agree it's silly.
With all that excess reactor power they should just run a really long extension cord to the destroyer.
Hmmmm.... I intended that just as a silly joke, but the more I think about it the more I realize some sort of variation on that concept might actually be viable. Plenty of engineering headaches (probably the main difficulty being ships generally not equipped to power the propeller by electricity) and the hazards of maintaining such close formation... but it would be cool for one ship to be able to power one or two other ships that are either damaged or having fuel worries.
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One less-obvious thing that hasn't been mentioned is the huge distance an attacking force would have to cover just to get to the carrier. You know those pictures of a full carrier group plowing along with the ships right next to each other? They only did that for the picture and spend most of the time at least several miles away from each other.
I think you're on to something there. If you work the kinks out of the technology, such that the gun itself doesn't wear out very fast, then all you need is a lot of electricity.
Add on a few nuke reactors, and/or a nice capacitor bank, and you're suddenly only restricted by how many projectiles you can carry. As you mention, these are going to be simple - basically just metal slugs. There's no more powder or fuel required for the task, which is in sharp contrast to conventional weaponry.