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.'"

Comments

How silly

[JesseL]

An effective military rail gun would need a huge vessel to carry the capacitor bank and a nuclear power station to make a rail gun practical. Where is the Navy going to get something like that?

Oh wait...

Re:How silly

[paganizer]

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.

Re:How silly

[AKAImBatman]

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.

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. :P)

Re:How silly

[ThePeices]

The majority of people here seem to think the rail gun is powered by a huge capacitor bank which takes a long time to charge, or required a nuclear power station to run it in a ship....bollocks.

A Megajoule class railgun is powered by a Compulsator, a type of modified alternator ( compensated for low inductance to provide enormous current pulses )...the rotor is spun up by a large engine, and the rotational energy in the rotor is turned into multiple high current pulses...in earlier test systems ( still megajoule class ), they can fire a burst of 10 shots on one spinup. These things can be scaled to fit in a modern tank, or up to naval gun size.

Re:How silly

[jollyreaper]

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.

Re:How silly

[Anonymous Coward]

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.

Re:How silly

[Baddas]

Wait wait, are we talking a simple flesh wound here? Or like, a through and through to the calf? Because it might be worth it. Did it hurt when they shot you?

Re:How silly

[DerekLyons]

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.

Re:How silly

[jollyreaper]

It's interesting how the cost accounting of the modern navy works out. Nuclear power makes sense for carriers and the three classes of subs we operate, SSN, SSBN, and SSGN, but it's never really taken off for surface ships. The last non-carrier nuclear surface boat was the Long Beach, I believe, an escort cruiser.

The whole naming and classification of surface vessels is also weird. Frigate is a name held over from the age of sail. Back then, heavy fighting was done with ships of the line, frigates were used for the free-wheeling missions of escort and raiding and scouting and what have you. Line ships were too important to risk being lost on mundane missions like that. Destroyers were originally called torpedo boat destroyers, ships capable of keeping up with the fleet while screening against torpedo boat attack. A cruiser was not a class but a job description, with frigates operating as cruisers in the age of sail.

By WWII, you had frigates, destroyers, and destroyer escorts operating as small ships working in various roles. Destroyers carried torpedoes to threaten larger ships, 5 inch guns to use against other destroyers and merchantmen, AAA for use against planes and depth charges for subs. The cruiser was intended to be a heavy combatant that could catch anything it could sink and flee from anything that could sink it. You then ended up with all the weird categories of light and heavy cruisers, battle-cruisers, etc. Then you had your battleships, slow sluggers that could not control the range of the fight. Then improvement in propulsion technology created fast battleships that could keep up with the cruisers. Carriers then pissed in everyone's cheerios because the battleship admirals didn't know what to do with them. Concerted air attack could take out a battleship with minimal loss of air crews but the formations the Americans put together towards the end of the Pacific war would have made conventional air attack suicidal for a well-trained and well-provisioned air force, let alone the Japanese. If two US-style fleets faced off, they'd likely run out of planes and pilots before running out of ships, thus forcing the engagement into a gun battle. The rapid development of technology changes everything.

Since the Cold War, the US has dicked around with cruisers and battleships but now the only large surface combatants left are carriers. Even the Aegis cruisers are running on hulls more comparable to destroyers and the arleigh burkes are using the same aegis. With the hitting power of modern anti-ship missiles, it's seen as impossible to armor a ship sufficiently to survive a strike. Then again, US naval thinking is still shaped by the Cold War and the idea that incoming weapons are going to be nuclear so you have to knock them down or else be incinerated, there's no such thing as armoring against a nuke fireball. Since we haven't had a proper naval engagement since WWII, all we're operating under is a bunch of theory that has not been put to the test in a very long time.

Re:How silly

[LeafOnTheWind]

I'm afraid you're misinformed: the USS Enterprise is equipped with a single power generator - a deuterium matter-antimatter power plant. In addition, while the Enterprise does employ a variety of energy weapons, including a full bank of 12 phaser arrays, the primary purpose of the warp core is to provide the energy for warp-speed interstellar travel.

Re:How silly

[Duhavid]

"Everything beyond that is classified. I could tell you, but then I'd have to shoot you."

You have it backwards! Shoot them first, then tell them.

And to optimize this, you can remove the 'nop', and just shoot them.

I mean, telling them and shooting them is not good, unless they
support transactions. ACID and all that.

Re:How silly

[hcdejong]

With such powerful power source as nuclear reactor is, why don't Navy use hydrogen-powered jets and just produce hydrogen for them from sea water, as needed? That would boost operational autonomy over the top.

Hydrogen is hard to store. You end up either with heavy high-pressure tanks, or with metal hydrides. Both take up much more volume than the equivalent amount of energy in oil-based fuel. It might be possible, but space and weight for carrier aircraft are always at a premium: making them all 50% larger to accomodate hydrogen tanks would halve the number of aircraft on the carrier, which would make the carrier only 30% as effective as it is now.

Also, you'd need a huge plant to keep up with demand.
The A4W used in the Nimitz class can supply some 100 MW.
Hydrogen contains 37 kWh/kg, let's say hydrolysis is 50% efficient so you need 74 kWh to make 1 kg. 100 MW will get you 1351 kg of hydrogen per hour. That's 31 tons per day.

The Nimitz carries about 11,000 metric tons of aviation fuel. Every aircraft takes off with 5-10 tons of fuel on board, you've got 85 aircraft, so you're looking at using (2 sorties *85*7 tons average) ~1200 tons of fuel per day. You need a reactor 40 times as large as the A4W to keep up with demand.

Re:How silly

[Guppy06]

"Nuclear power makes sense for carriers and the three classes of subs we operate, SSN, SSBN, and SSGN, but it's never really taken off for surface ships. The last non-carrier nuclear surface boat was the Long Beach, I believe, an escort cruiser."

Different missions.

Submarines are supposed to stay hidden for long periods of time, and they can't do that if they have to pop up ever few days at the local fuel depot. The carriers are supposed to be out there doing the whole power-projection thing, but (again) it's hard to be out there projecting power when your planes spend a few days every month pwning the airspace around Ye Olde Coaling Station. Really, there's nothing interesting going on at Diego Garcia.

As for the not-so-capital capital ships (at least those not tied to a carrier battlegroup), their job is more or less to fly the flag, preferably in places where people can see it, and people have a tendency to live on land. So your frigates and your destroyers have a bit of a diplomatic role to play when they come to a port, disgorging the crew to partake of the local breweries and sex workers, as a way of telling everybody "Yeah, we're still here. And this is our boom stick." And if you're going to be hanging out anyway, why invest in a technology meant to help you avoid doing so? And on top of that, there are people like the Kiwis still squeamish about the whole "nukular" thing.

Once you decide nuclear isn't worth it on these vessels, the only question remaining is whether to pay money to build a whole separate class of nuclear fun-sized ships for escorting the CVNs (and there's only so many), or to pay money to throw a tanker or two into the mix of a battlegroup.

Fusion Power...here we come

[clonan]

The REAL reason Fusion power will be perfected...so the Generals can fire their fancy guns more than a few times an hour.

Re:Fusion Power...here we come

[kabocox]

The REAL reason Fusion power will be perfected...so the Generals can fire their fancy guns more than a few times an hour.

Non-solar fusion won't produce that much energy any time soon. What we need is serious solar energy collection; I'm talking about solar powered orbital microwave death rays. That's how to properly power your death dealing toys. With a proper number of death rays, you should be able to fry any acre of land on the globe fairly easily. It's assumed that frying the land will kill off all enemy soldiers, peasants, and nature lovers that may be hiding there.

Hmm, my SI is fuzzy...

[Anonymous Coward]

Amps of power?

I miss the days of gunpowder

[INeededALogin]

Seriously, how much energy does it take to kill someone.

Re:I miss the days of gunpowder

[Monokeros]

That clearly depends on how awesomely you want to kill them.

Re:I miss the days of gunpowder

[KTheorem]

> This isn't for killing 'someone', it for poking big holes in things that are very hard.

If you have that much energy, though, then surely lasers become a more practical alternative?
Lasers can't be shot on a trajectory to hit something 1000 miles away. Nor can they cause much damage outside of where they hit.

Re: I miss the days of gunpowder

[blagger99]

Mach 1 = Speed of sound. In air, approximately 1,130 feet per second at 21 degrees Centigrade [1]. Mach 8 = 8 x 1,130 ft/s = 9,040 ft/s.

A 7.62mm round has a velocity of 2,756 ft/s [2], approximately Mach 2.4. Energy use is 3,352 J for a bullet weight of 9.50g.

The article doesn't specify, but I imagine the 32MJ rail gun uses projectiles a little larger than 9.5g.

[1] http://en.wikipedia.org/wiki/Speed_of_sound
[2] http://en.wikipedia.org/wiki/7.62x51mm_NATO

Re: I miss the days of gunpowder

[Hal_Porter]

http://www.fredericksburg.com/News/FLS/2007/012007/01172007/251373

The prototype fired at Dahlgren is only an 8-megajoule electromagnetic device, but the one to be used on Navy ships will generate a massive 64 megajoules. Current Navy guns generate about 9 megajoules of muzzle energy. The same article talks about increasing range 'more than tenfold' to 200-250 nautical miles.

This article about proposals for guns on new destroyers for a talks about muzzle velocities of 800-900 metres per second, or about Mach 2.5. Wikipedia says that 1800 mps or about Mach 5 is 'close to the limit achievable with chemical propellants'

So 64MJ and Mach 8 is pretty impressive. It would mean that US ships would have a profound advantage of having ten times the range of their opponents. More to the point if they were attacking a country with not much navy but decent anti ship missiles, they could avoid getting too close to them. Actually this page says

China acquired SS-N-22 launchers and missiles (specifically, the for-export 3M-80E Moskit variant) with its 19992000 purchase of two Sovremenny destroyers from Russia. According to Russia, the Chinese funded the development of the SS-N-22 version for the People's Liberation Army Navy (PLAN), which has the designation 3M-80MBE, and this version differs from earlier versions mainly in that the range is increased beyond 200 km, and these new missiles will be first onboard the second pair Sovremenny class destroyers. It is speculated that the PLAN intends to use it against the carrier battle groups deployed by United States Navy in case of any confrontation with Taiwan. Now the railgun can actually fire 200-250 nautical miles or about 460 km, so US ships could stay well out of range.

Re:I miss the days of gunpowder

[rahvin112]

The Railguns serve a purpose which right now is being filled by EXTREMELY expensive weapons. The cruise missile has a range of about 600 miles, it also moves at a speed that makes them very easy to shoot down. To compensate for this they fly them at extremely low elevation, but they can still be shot down and you can hear them approaching for quite a while before they get there, making it much easier to avoid being hit by one.

The railgun on the other hand currently has a range roughly 1/3rd the distance of a cruise missile and IIRC the 64MJ version has a range around 2/3 the range of a cruise missile. Not only that but the projectile cannot be shot down as no weapon could catch it, nor even if they could (fired head on) would the interceptor be able to stop it as the kinetic energy of the blob of metal would simply disintegrate anything that tried to stop it with almost no deflection of the weapon. Not only that but the railgun offers extremely high energy on impact, far in excess of the 500-2000lb bomb on cruise missiles. I've heard estimates that place the energy release on impact with that of around 15000lbs of TNT, the explosive energy release is huge but the big blob of metal becomes millions of small pieces of metal that fly in every direction along with rocks and dirt moving at ultra high velocities from the impact site. And above all this the railgun projectile is under $500 in comparison to the $1 million dollar tag for the cruise missile.

The railgun essentially allows the USN to toss moderately sized meteorites at enemies. Whenever a naval article comes up everyone likes to talk about how vulnerable the USN is because of Sunburn and other antiship missiles. What they fail to realize is that once the DDX destroyers come online the fleet wouldn't even need to get in sunburn range to absolutely destroy even fortified coastal positions. Take a couple DDX destroyers and the new CDX carriers and you have a fleet that can sit 400 miles off the coast and bombard all the coastal defenses into oblivion before moving further in to bombard the cities and fortifications further in from the coast. The railgun projectiles also have extreme penetration, they can cut through 10's of feet of reinforced concrete with ease, and even underground facilities become susceptible as 10 projectiles could likely cut a massive hole and penetrate buried facilities that could then be followed up with bombs dropped from planes. There is also another advantage, cruise missiles aren't effective against mobile targets because it takes so long for them to get there, at mach 8 the railgun projectiles flight time is extremely small, along with the no advanced warning (no sound preceding impact) gives the projectile a much better chance at hitting mobile targets without having to use manned aircraft.

The USN is also trying to find guidance systems that can survive the G forces in the hope of having some minimal guidance.

whatcouldpossiblygowrong

[Anonymous Coward]

I noticed that almost every story today has this tag on it. What could possibly go wrong if you stop using this tag for every article?

Re:whatcouldpossiblygowrong

[stephencrane]

Seriously. This tag is being used way too much. A rail gun is, for all its complexity, a relatively straightforward concept. A story about, oh, releasing genetically-manipulated mosquitoes into the wild really should set the benchmark. Standards, people, standards. We're -geeks-, fer crissakes.

Re:whatcouldpossiblygowrong

[Chris Mattern]

Meh. He's got some cute pictures, but his grasp of military history is teh fail. The French did *not* discount the possibility of the Germans coming through the neutral Low Countries; in fact, they expected it--it was what they'd done last time, after all. That's what did them in. All their decent units were all lined up on the Belgian border and rushed into the Flanders plain to meet the expected oncoming Germans as soon as Belgium was invaded. But the Germans broke through at the pivot point, in the Ardennes, getting behind the Allied forces now in Belgium and then driving west to the sea to bottle them all up quite nicely, including the British (who managed to evacuate out of the pocket from Dunkirk).

Re:whatcouldpossiblygowrong

[Goaway]

It's simply an expression of the closet technophobia that affects so many Slashdotters.

Obligatory

[DeadDecoy]

They need to attach some focal confirmation for when you hit the target:
Headshot!

1.21 gigawatts

[Anonymous Coward]

Let me know when the flux capacitors get fully charged...

To be a bit mercenary about it...

[KublaiKhan]

There is no such thing as overkill. There is only "still firing" and "out of ammo."

Oblig

[MobileTatsu-NJG]

A spokesman for the Iranian Navy was reported as saying ..."Camping faggots!"

Newton

[dorix]

It's also capable of propelling ships in reverse at speeds of up to Mach 3.

Re:Newton

[clarkkent09]

Projectile weight = few pounds. Ship weight = 50,000 tons. I think the ship will win

What are they launching again?

[koa]

As far as I can tell- the article mentions nothing about the types of ammunition they fire with this- however upon closer inspection,
  I may have found a clue:

"Installation of the laboratory launcher is currently under way"

Seems like a waste of some perfectly good laboratories!

I've got Wood

[cthulu_mt]

God, this is why I love being an American.

Bill Gates was heard to comment...

[Anonymous Coward]

No one needs more than a 64-megajoule rail gun.

Space Gun

[Doc Ruby]

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.

Re:Space Gun

[afidel]

The problem with using a railgun to launch anything but raw materials into space is acceleration. If you have to impart enough energy into the object over a track that at a maximum is a couple kilometers long you're going to be impacting too many g's for much of anything to stand up to.

Re:Space Gun

[Cochonou]

Kinetic energy equals mass times speed squared.
Deploying twice the energy should only send the projectile 1.4 (the square root of two) times faster.

Re:Wave Motion Gun

[robvs68]

I hope that the Navy's new Rail Gun doesn't require a brief but critical period to charge before firing, and I hope that is does not require all non-essential power systems to be deactivated, leaving the ship powerless and adrift for a short time after firing... (wiki)

Looks nice

[OeLeWaPpErKe]

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.

Re:Looks nice

[JesseL]

The best bet would probably be to use something like tungsten for the rail surfaces, to minimize the arc vaporization. I doubt you'd get ceramics conductive and physically durable enough to be suitable.

Einstein on rail guns

[sakdoctor]

I don't know if World War III will be fought with railguns or belt-fed airport screening devices, but World War IV will be fought with sticks and stones.

Re:Einstein on rail guns

[xleeko]

I don't know if World War III will be fought with railguns or belt-fed airport screening devices, but World War IV will be fought with sticks and stones.

No, no ... you got the quote all wrong.

"World War III will be fought with radioactive Monkey-Snake Hybrids, World War IV will be fought with watermelons and trebuchets, World War V will be fought with intelligent berzerker cheeses, and World War VI will be fought with sticks and stones ... the size of planets!"

Hey, don't knock it

[Sycraft-fu]

We get a lot of cool technologies because the military wants new toys. You can argue about if it should be that way or not, but it is how things go. GPS is a great example. No civilian organization would invest in something that big. Are you crazy? Who would want that? However the cost wasn't a problem for the military and hence we got one of the most amazing navigational aids ever. Even now that the technology has been proven feasible and useful, or rather essential, the military run systems remains the only one. The European civilian governmental version remains snarled up in political battles.

So while you jest, there could be truth in the statement. Fusion is all well and fine, but there's only so much money going to be thrown at it. We have other cheap power sources in terms of commercial use, so not a lot of commercial dollars, and it just isn't sexy or pressing enough to get much government research dollars... However if there's a major military application, well that could get billions easily.

That's one reason I'm not always opposed to defense spending. Though it is very often wasteful and it seems there are better things to do with the money, it does seem to be one way for getting projects that just don't get built otherwise. A great many things come directly from defense research.

The military's been testing rail guns forever

[Phat_Tony]

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.

Re:The military's been testing rail guns forever

[San-LC]

I remember watching a movie called the Pentagon Wars where they were dramatizing the tests of the M2/M3 Bradley Fighting Vehicle. In it (based on a true story), they tested the aluminum armor plating by launching an anti-tank warhead against it and seeing what would happen inside. They used sheep in the place of humans, and all of the sheep were killed via overheating due to the internal air temperature flaring up.

How long will the barrel be?

[jollyreaper]

Are these things going to be turret-mounted like with battleships or will the rail have to be as long as the ship, requiring the whole vessel to turn to align the weapon?

Re:uh, wrong. please check your math.

[AKAImBatman]

The DDX Destroyer is just the first step in the Navy's futurization of the fleet. The CVNX project intends to modernize carriers in the same way that the DDX Destroyers will be modernized.

Some of the features:

• Better, more powerful reactors (3x increase in available power!)
  
• Stealth
  
• Electromagnetic catapults
  
• Greater automation leading to reduced crew complement
  
• Better survivability in a fight (like that's been a big concern :P)
  
• Advanced arresting gear (no idea what that means)
  
• Dual Band Radar support
  
• "Flexible ship infrastructure" (i.e. We can mount some kewl energy weapons once Congress gives us the green.)
  

Navy Fact File

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.

Vs Light Gas Gun?

[IdeaMan]

I think the jury is still out on whether rail guns or light gas guns will be the next step.

Let me list the current advantages/disadvantages:
Rail Gun:
+ Simple firing mechanism (Two rails, one plug, massive juice)
+Very little muzzle flash
+Very rapid fire (Gatling configuration to spread out heat on rails)
*Acceleration limited by current carrying capability of rails.
- Complex/heavy electrical system (Banks of caps + power supply to charge them)
- Rail wear
-Heavy projectiles increases support structure significantly

Light Gas Gun:
+ Heavy projectiles scales up rather well.
* Medium complexity (More complicated than Gatling mechanism)
* Acceleration limited by maximum chamber pressure.
- Bore wear
- HUMONGOUS muzzle flash (hydrogen combusting)
- Medium rate of fire.

Bottom line: Flechettes: Rail gun; Sub Orbital or ship killer: Light Gas Gun

Currently light gas guns emit a huge fireball out the end of them, which may tend to limit their use for a shoulder fired weapon (anti-tank, anti-air). On the other hand it is a lot easier to store and release obscene amounts of energy in a gas or powder than in electrical form. I would imagine porting the barrel would allow recovery of some of the hydrogen.

One advantage the railgun might have is it might allow different projectile shapes like fins that would be difficult to achieve with a light gas gun.

We should be using light gas guns to ship fuel up to the bottom of a chain of a LEO space elevators.

Amps != Power

[BlueParrot]

Ampere is a measure of current, not power.

To put it this way, the European Spallation Source is a planned particle accelerator which is planned to have a proton-beam current in the range of a few milli-ampere. That is, comparable to the current drawn by your LCD monitor in standby. The catch is that ESS will be using proton energies up to a billion electron volts, thus making the power output of the accelerator comparable to a small nuclear reactor.

You can NOT quote power in terms of ampere without specifying the voltage. Conversely I've generated several thousands of volts using my bare hands and a piece of nylon, but because the current was rather small nobody noticed.

What is even more interesting is the time over which you can sustain a given power output. Over at our physics department we have lasers with power outputs beyond all the worlds nuclear reactors taken together. The pulse doesn't last very long however...

This has been thought of

[Quila]

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.

Watts!

[Roger W Moore]

Eight and 9-megajoule rail guns have been fired before, but providing 3 million amps of power per shot has been a limitation.

I agree. This would be extremely hard to achieve since amp is a unit of current. The problem is not that but rather that in combination with the voltage required to drive it.

Amps/watts

[Cheesey]

Surprised more people haven't commented on this. Ending a summary with "3 million amps of power" is a classic Slashdotism. It would once have provoked many responses pointing out that an amp of power makes as much sense as a gallon of distance. Perhaps we can't be bothered correcting the editors any more.

Re:uh, wrong. please check your math.

[calebt3]

Advanced arresting gear (no idea what that means) If it refers to the carrier, arresting gear is a cable that the fighters try to hook when they land so that they don't go off the edge.

Respawn...

[Misch]

The editor who posted this was fragged with the BFG, but respawned this article a few days later.

Interesting Facts

[timias1]

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.

Re:uh, wrong. please check your math.

[Shakrai]

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.

Uhh, wouldn't that require a line of sight to the intended target? Naval combat within visual range went out of style after Coral Sea. If you don't need a LOS then it would seem to be that this is a guided projectile and you don't exactly need a railgun for that (see harpoon, exocet, etc, etc).

I would suspect that the Naval interest in rail-gun technology is probably aimed at point-defense (i.e: shooting down incoming anti-ship missiles) more then anything else.

Re:It's all fun and games...

[AKAImBatman]

It's all fun and games until someone decides to make a nuclear-capable artillery shell for this thing.

There are some serious problems to mounting a nuclear munition on this sucker. First off, the weight of the round currently being fired is actually quite small. The weapon would need to be scaled up by many, many fold just to fire the nuclear munition.

Second, no existing type of warhead would survive the shock of launch. A gun-type device would detonate on launch. (NOT good.) An implosion device requires that the plates surrounding the charges that surround the plutonium core be carefully calibrated. A single charge or plate out of place and the bomb will fizzle out. Advanced hydrogen weapons are out as well, as they require an atomic explosion as a trigger. Plus, the cores of hydrogen bombs need to be kept even more precisely in place in relation to the uranium shell of the weapon.

All in all, the only thing you'd accomplish by combining a rail gun with a nuclear warhead is to either blow yourself up or damage your highly-expensive-bomb-that-could-have-been-more-easily-deployed-with-a-super-sonic-missile.

Re:uh, wrong. please check your math.

[baldass_newbie]

I have no idea how an "advanced" arresting gear differs from a "regular" arresting gear. i.e. The navy isn't saying. It's just... advanced.

These go to 11.

Correction...

[tjstork]

Since the Cold War, the US has dicked around with cruisers and battleships but now the only large surface combatants left are carriers. Even the Aegis cruisers are running on hulls more comparable to destroyers and the arleigh burkes are using the same aegis. With the hitting power of modern anti-ship missiles, it's seen as impossible to armor a ship sufficiently to survive a strike. Then again, US naval thinking is still shaped by the Cold War and the idea that incoming weapons are going to be nuclear so you have to knock them down or else be incinerated, there's no such thing as armoring against a nuke fireball. Since we haven't had a proper naval engagement since WWII, all we're operating under is a bunch of theory that has not been put to the test in a very long time.. 1. Arleigh Burke destroyers are actually pretty big. Let's compare, shall we, a Burke destroyer against, say, an Royal Navy King George V class battleship of World War I.

CategoryArleigh BurkeKing George V>
Displacement9000 tons23,400 tons
Length509 feet598 feet
Beam60 feet89 feet
Propulsion100,000shp31,000shp
Crew320/td>870

So, the Arleigh Burke is nearly as long, has three times the engine power as a World War I era top of the line British Battleship. In terms of firepower, there's really no comparison. If you plopped an Alreigh Burke and a KGV into the same ocean, the Burke is going to have missiles away before the KGV can even make visual contact.

The moral of the story is that you really have to think about what the Navy has evolved into. It's not that there are no more battleships, per se, it is more like every combatant the navy has is a capital ship in its own right.

I must also digress about armor. It's also a bit of a gap to say that American ships aren't armoured. Yes, it is true that American warships do not have thick steel armour belts in the past, but its also true that thick armour belts can't resist modern shaped charges, its also true that they only were really thick at areas of a ship where designers anticipated the firing arcs of other shells would be. Have a look at the now declassified maps of the USS New Jersey's armor belts. You could theoretically program missiles to hit other parts of the ship. Against a range of threats, from bombs to torpedos, or even missiles that can be programmed to hit a ship from any angle, it is simply impossible to provide passive armor protection on all surfaces.

So, what designers do do is local armoring. They might not armour the entire hull, but they'll wrap critical equipment with some kevlar jackets, and that's not too shabby. That does come from combat experience, in a weird way. During vietnam, they did nothing to protect combat aircraft, but, they realized that putting a little bit of armor around a few critical things would save a lot of planes. These things were incorporated, among other things, into the highly successful A-10, which is a very survivable plane, and, to some extent, that sort of thinking has found itself into US Navy ships as well.

Re:uh, wrong. please check your math.

[Shakrai]

But if you have a computer to adjust firing angle, firing energy, etc, you can very well make it targeted (by doing the calculation required for it to strike a target XX miles away at XX altitude).

How do you have a projectile with a 200+ mile range that isn't guided?

Even at Mach 8 there's almost a two minute flight time to reach 200 miles. Ignoring wind, the coriolis effect and everything else that could change the course of your projectile, what happens if the target changes course in that time or takes evasive action? A lot can happen in two minutes.....