Navy Gets 8-Megajoule Rail Gun Working 650
prototypo writes "The Free Lance-Star newspaper is reporting that the Navy Surface Warfare Center in Dahlgren, Virginia has successfully demonstrated an 8-megajoule electromagnetic rail gun. A 32-megajoule version is due to be tested in June. A 64-megajoule version is anticipated to extend the range of naval gunfire (currently about 15 nautical miles for a 5-inch naval gun) to more than 200 nautical miles by 2020. The projectiles are small, but go so fast that have enough kinetic punch to replace a Tomahawk missile at a fraction of the cost. In the final version, they will apex at 95 miles altitude, well into space. These systems were initially part of Reagan's SDI program ("Star Wars"). An interesting tidbit in the article is that the rail gun is only expected to fire ten times or less per day, presumably because of the amount of electricity needed. I guess we now need a warp core to power them."
95 miles altitude is space..Way Cool (Score:5, Interesting)
However, this seems very interesting as an Anti Satellite/"Star Wars" platform. If they can get the software working to intercept, this should (scaled up version) be able to knock out satellites, ballistic missiles, etc - shouldn't it?
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Re: 95 miles altitude is space..Way Cool (Score:4, Funny)
;-)
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Re: 95 miles altitude is space..Way Cool (Score:4, Insightful)
No, because when you shoot a projectile, you're putting it into a orbit that intersects the earth. You need some other impulse source to circularize the orbit.
Probably sufficient for a first stage. (Score:5, Insightful)
From the above, I'm assuming they have a reasearch project underway that would directly translate into launch survivability for the hardware. I'm not a electrical or mechanical engineer, but I'm going to guess that electronics embedded in high-impact composite ceramics (a la tank armor) might be the ticket here. The rocket engine and the fuel are another story. My understanding is that solid rockets are relatively simple construction (compared to liquid) so they would be the best candidate for survial. Pretty much every weld or joint I can think of would come apart under those kind of forces, so the fewer parts the better.
Re:Probably sufficient for a first stage. (Score:5, Interesting)
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My understanding is that solid rockets are relatively simple construction (compared to liquid) so they would be the best candidate for survial.
Just don't rely on the fuel to provide any structural integrity, as it is not really solid like a fireworks rocket. The SRBs used to launch the space shuttle are a good example of this. They have a void in the center of the rocket running through their entire length. This is because the fuel burns at the surface, and this configuration enlarges the surface by a large factor, providing considerably more power. So rather than burning from the end of the rocket, the fuel burns from the inside out.
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Piece of cake. (Score:5, Funny)
Attach projectile to giant bungee cord.
Attach giant bungee cord to object you want in orbit.
Give object giant scissors.
Expanding on this, you could tie one object with several rubber bands to several projectiles.
Re:Probably sufficient for a first stage. (Score:5, Insightful)
No - getting the hardware capable of surviving the G-forces is the easy part. The hard part is explaining to the beancounters why you are replacing a 50 million dollar first stage with a 10 billion (or most likely more) dollar accelerator - and not reducing your launch costs significantly because of vastly increased infrastructure maintenance and operations costs.
There's a reason why only the lunatic fringe of the alt.space community keeps insisting that an EM accelerator is the 'only way to go'.
Re:Just fine if you don't need electronics (Score:4, Informative)
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Re: 95 miles altitude is space..Way Cool (Score:5, Informative)
Re: 95 miles altitude is space..Way Cool (Score:4, Insightful)
If you fire the projectile "strait [sic] up, and at the perfect velocity that it's not moving that fast when it leaves the atmosphere" then it will certainly come back down, and pretty fast at that. These naval guns are putting up a projectile that leaves the atmosphere and it's entire flight time is 6 minutes. Oh, and there's the matter of the big bang when it comes back down on your head.
You're right, it is impossible for the rail gun to hit itself from behind, but definitely not for the reason you say. Air resistance will slow down the shell, causing it to fall short. BUT, neglecting air resistance, if you fire your shell at orbital speed (for the altitude of your gun) then the shell will circle the planet and hit you from behind. That's how orbits work. It will not "fly out too far for the earth's gravity to have an effect on it." If you fired the shell at escape velocity or greater then it would fly away forever, but that wouldn't be very useful for putting it in orbit, would it?
Re: 95 miles altitude is space..Way Cool (Score:5, Informative)
You can say that the ability of an object to orbit is determined by the energy only if you want, but an object that has part of that orbit that intersects the ground won't orbit for very long. That's what happens if you fire an unpowered projectile from the surface. It's orbit MUST intersect the firing point, barring some sort of acceleration in flight.
None of what you describe admits a spiral as an allowed orbit.
Re: 95 miles altitude is space..Way Cool (Score:4, Informative)
The basic idea is that, if you want to change the altitude of an orbiting object at a certain point, you need to give it a push ON THE OTHER SIDE of the planet the object is orbiting (you want a lower altitude over china, you need to decrease speed over america).
If you change the velocity the bullet exits the muzzle of the cannon (or the railgun or whatever), you are making the bullet go higher/lower at the other side, and then hitting the cannon faster/slower when it returns. That is, unless it reaches escape velocity (it'll never return) or hits the planet. To circularize the orbit (basically to make the bullet go higher over the cannon), you need to give it a push when it's on the other side of the planet, that's what the rocket is for.
Re: 95 miles altitude is space..Way Cool (Score:5, Funny)
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Re: 95 miles altitude is space..Way Cool (Score:5, Interesting)
Re: 95 miles altitude is space..Way Cool (Score:5, Funny)
Even more profitable would be to make Earth pay you NOT to lob 100 tons of titanium at them per day.
TANSTAAFL
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Put big enough wings on it, and you can steer it in just like a 747.
Launch Loop (Score:5, Interesting)
Basically, its a magnetic rail gun for launching space-craft into orbit. And in order to avoid the crushing G-forces involved, it has to be hundreds of miles long. So, while it may not be economically or politically viable, it is technically feasible. We know how to build a launch loop, as opposed to a Space Elevator, which can't be constructed with current technology.
-Sean
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8,000j = 2,222 V*mAh
2,222 V*mAh/1.2V = 1851.85 mAh
As a result, using an array of eight paralell AA rechargables and a capacitor array, one could probably build a railpistol, capable of 4-8 shots per charge (depending on the failure characteristics of the batteries, and the wear-and-tear on the caps). That is, given they've solved the rail damage issue.
Mind you, the max discharge rate on Lithium is 1.5A, and o
Re: 95 miles altitude is space..Way Cool (Score:5, Interesting)
You'd need to build a space tugboat that can hunt down and gather the payloads, then boost them to a higher orbit. No biggy, you can use robots with ion drives for that stuff.
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No biggy, you can use robots with ion drives for that stuff.
Ion drives would be worthless for your proposal. From Wikipedia:
In practice, with currently practical energy sources of perhaps a few tens of kilowatts, and given a typical Isp of 3000 seconds (30 kNs/kg), ion thrusters give only extremely modest forces (often tenths or hundredths of a newton).
Hardly the kind of propulsion you want to use for something that would be constantly stopping and changing direction. Ion drives are best used for crafts that travel extremely long distances with no need to change direction.
Re: 95 miles altitude is space..Way Cool (Score:5, Informative)
Not to say that this gun cannot fire projectiles into orbit, just to say that firing something into space and having it stay there is much harder than just firing something into space.
Re: 95 miles altitude is space..Way Cool (Score:5, Funny)
1. *some idea*
2. "use robots with ion drives for that stuff"
3. profit!
Re: 95 miles altitude is space..Way Cool (Score:5, Informative)
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Re: 95 miles altitude is space..Way Cool (Score:4, Funny)
I don't see them replacing crusie missles (Score:5, Interesting)
Re:I don't see them replacing crusie missles (Score:5, Funny)
if you can only fire 10 per day.
I'd be very careful accounting for winds over a distance of 200 miles, particularly where chinese embassies are located. Must be a hell of a job to be spotter for this kind of weapon.
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=Smidge=
Re:I don't see them replacing crusie missles (Score:4, Informative)
You are correct, sir! (*DING*)
Unless something has changed in the last year or so, the railguns will fire Extended Range Guided Munitions [globalsecurity.org] - a type of GPS-guided "smart" shell.
On another subject, it seems I was right [slashdot.org] when I suspected that these ships would be unable to maintain a high rate of fire. I never expected it to be this bad, though. Seems our DD(X) class is going to need a fleet of tanker escorts shoud a real war break out.
*grumbles something about failure to improve nuclear generators for destroyer use*
Re:I don't see them replacing crusie missles (Score:5, Interesting)
There's nothing wrong with the nuclear reactors we have now; you could easily fit one of them into a destroyer without any problems. I'm sure Westinghouse Nuclear would be happy to draw you (assuming 'you' have a few billion bucks to spend) some plans of how it could be done. Much of the space optimization has already been done, for submarines. There are several basically standardized designs that you could build the ship around, and then plop one in when you got everything else ready. It's totally doable.
The Russians have several nuclear powered ice breakers that aren't much larger than destroyers, and they used to have several nuclear-powered cruisers as well (although I think they've all been decommissioned).
The reason that surface ships haven't been built with nuclear reactors has more to do with the perceived economics of fossil fuels, rather than any real technical limitations. And for that matter, I've seen analyses that show that bulk supertankers could be economically driven by nuclear reactors -- if the NS Savannah was around today, and upgraded to use containerized cargo instead of manually loaded stuff, it would probably make money due to the high cost of bunker and diesel.
If it's really electricity that's the problem with the rail gun, putting a nuclear reactor on a smaller ship wouldn't be more work than breaking out some old plans, or making a long-distance phone call to a retired-engineer's home in Russia.
Re:I don't see them replacing crusie missles (Score:5, Interesting)
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The GPS-guided artillery shells that I've seen actually don't use "fins" in the same way that a missile does, but little pop-up retarders that change the shape and aerodynamic characteristics of the
Re:I don't see them replacing crusie missles (Score:4, Interesting)
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"they will apex at 95 miles altitude, well into space."
There are no winds in space. For that matter, the atmosphere thins out considerably before then. If it didn't these long range railguns would be pretty useless because most of the kinetic energy would be lost. And at the velocities we are considering the time spent in the deeper atmosphere is miniscule. Neither do we know how much spin the projectiles will have (a major stabilizi
Well (Score:5, Insightful)
Most likely it will end up as an augment. One of the virtues of this system being, though, it can set up a shot quicker than a Tomahawk.
Re:I don't see them replacing crusie missles (Score:5, Interesting)
Re:I don't see them replacing crusie missles (Score:5, Insightful)
That said, the point of "How many cruise missles do we expect to actually fire in one day?" is a good one.
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Somehow, I don't see generating power as a huge problem. Even a 64MJ launcher operating at 1% efficiency would only require 42 seconds of power from the D2G.
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Solar won't help with this to any significant degree - at least not anything mounted on a ship. On the other hand, you could theoretically make a bunch of little floating hockey-puck shaped robots that would be just smart enough
Re:I don't see them replacing crusie missles (Score:5, Insightful)
(I'm ignoring whether they are practical or not, or if they cost too much, compared to alternatives. I'm just pointing out that the military can solve many limitations by throwing money at them, and no one in the government is embracing plans to limit military spending at this time.)
Re:I don't see them replacing crusie missles (Score:5, Informative)
You need to read more about the DOD budget process inside the Pentagon and the White House. It isn't so much that they are proposing spending less, as there are a LOT of fights over exactly where to devote the spending, and which service gets how much, and how it is portioned out. How much goes to maintenance, how much to new equipment purchases, how much to soldiers, sailors, marines, and airmen. How much to R&D like this?
Very high cost equipment does indeed get canceled, simply because it costs too much. Usually measured as "too much over budget" but it is related to cost. Cost does matter.
The Navy has this as a very real problem over the next 10 years. The next generation aircraft carrier is projected to cost $10 billion. The Navy currently spends $10 billion per year building ships and submarines. A ship must be fully appropriated in the year that construction is begun. The year they start building the next-gen aircraft carrier, does the Navy simply not build any submarines, which they want to build 2 per year for a cost of $2.2 billion each? How about DDG-51 class destroyers, at a cost of $1.4 billion each? Or DD(X) (now renamed to DDG-1000) class destroyers, at a cost of about $3 billion each? Amphibious assault ships, like the LPD-17, which I don't know a cost for, probably north of $1 billion? Or LCS ships, for the low cost of about $400 million each?
What doesn't get built the year they start the next aircraft carrier?
The Air Force has the same problem, with F-22 aircraft that cost $200 million each... they aren't buying 600 of them like they planned 10 years ago. Instead they are getting... 190 I think. Ditto with the F-35 (JSF), which they are not buying 4,000 of, or whatever the original purchase number was, because they are also fairly pricey.
Just because the military works with large budgets, doesn't mean that the cost of equipment doesn't matter. It matters very much.
And they really do care about limiting costs, because it really does affect how many they can buy.
Not electricity (Score:5, Informative)
I'm almost positive the main issue is not electricity generation but rail friction. The best rail guns I'd heard of until today needed completely overhauling after each test firing because the rails themselves are damaged so badly as the projectile passes. Coil guns are better in this respect, as the projectile doesn't have to touch the coils...
Rail damage (Score:5, Informative)
Full-scale models have been built and fired, including a very successful 90 mm bore, 9 MJ (6.6 million foot-pounds) kinetic energy gun developed by DARPA, but they all suffer from extreme rail damage and need to be serviced after every shot. Rail and insulator ablation issues still need to be addressed before railguns can start to replace conventional weapons.
Re:Not electricity (Score:5, Informative)
The projectile in a rail gun should barely be touching the rails at all so it doesn't get welded in place. You end up with the equivalent of a huge arc welder traversing the rails with several thousand degree plasma.
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Re:I don't see them replacing crusie missles (Score:4, Insightful)
Re:I don't see them replacing crusie missles (Score:5, Interesting)
The contract is awarded to a nuclear shop so I suspect that the thing will have an integrated reactor which makes it even more interesting.
What goes around, comes around. After realising that missile tech is too expensive, Iraq tried to build the Babylon gun with a 1000 miles range. For the same reason (the missiles being too expensive) Russians have now developed a gun launcher (forgot the name) to fire high altitude atmospheric probes instead of the old missile system . US nearly did that with the HARP, but heavy lobbying by the aerospace industry killed that. And now we come full circle with US looking at long range guns for cost reasons.
Remo Williams, not lobbyists (Score:3, Funny)
Where can I get one? (Score:5, Funny)
Projectile distortion? (Score:3, Interesting)
What happens to the projectiles in these things? Such a gauss density I would assume, beyond simply the accelleration of the projectile has to be considerable. The coin shrinker is only 1600-2500 J [delete.org]
Assuming 2500 J in a space of 3 mm does to an object the size of a quarter, 8 mega Joules would have an equivilent magnetic density spread over a gun 96 metres in length. Or me math is fscked...
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They transfer their kinetic energy to whatever poor sumbitch they happen to hit?
My dad worked on a similar weapon for the DoD in the late 80s and early 90s. Since it's a kinetic weapon the projectile as such doesn't matter much. It's basically just a hunk of solid metal aerodynamic enough not to miss the target.
Power Sources (Score:5, Funny)
If only we knew when lightning was due to strike some sort of a clock tower? Surely, then, we could harness the power needed.
If that doesn't work, perhaps some new technology involving trash?
boom! (Score:4, Funny)
Yeah, but can you headshot with it from the far platform on the Longest Yard?
sooo... (Score:5, Funny)
More nuclear ships? (Score:5, Insightful)
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The Navy keeps nuclear power on submarines because the air independence is too valuable (notwithstanding the nuke/diesel arguments) and on carriers because it makes for a ready source of steam (think catapults), hot water, etc.
Powe
physics of railguns (Score:5, Informative)
One presumes there are sonic booms associated with this. Anyone know if they're louder or quieter than the explosions associated with heavy ship artillery?
Re:physics of railguns (Score:5, Interesting)
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As far as a sonic boom goes:
I have several rifles that fire bullets that travel faster than the speed of sound. They don't make a sonic boom. They make a hell of a racket from the shell firing, but it isn't a sonic boom. Basically unless you're firing or moving something significantly large (a jet), there isn't going to be an audible sonic boom.
even the tip of a bullwhip makes a sonic boom [wikipedia.org], and that's not particularly large. but i was under the impression that you need to be along the path of flight to hear the full effect of a sonic boom, so i don't think you would hear it when firing a rifle (where the flight path starts in front of you and continues away from you) as it's not building up a continuous shockwave that passes you all at once
Mmmm.... I love rail guns! (Score:2, Informative)
It's an old site but it's still just as awesome. I almost considered trying this out myself but I'm not exactly sure if such a thing is legal.
Not sure about this (Score:5, Funny)
Slight correction? (Score:5, Insightful)
I think they mean deployment, unless the Navy knows something Congress doesn't. Which wouldn't surprise me.
I wonder..... (Score:2, Interesting)
*Meteorites leaves evidence. Meteors can explode in midair.
Cool to think about....
Amount of power (energy really) (Score:5, Interesting)
Heat might be more of an issue. That would be over 30,000 BTUs, or a 60 degree rise in a quarter ton of cooling water.
Yeahbut.... (Score:4, Informative)
A cubic foot of seawater weighs approximately 64 pounds. A quarter ton, or 500 pounds, means this thing would raise less than 8 cubic feet of seawater by those 60 degrees. (A cubic foot of fresh water is 62 pounds, so the difference is negligible) That's a miniscule amount of global warming that this thing will add to the ocean each time it fires. And with entire oceans to heat up I doubt the Navy is too concerned about that environmental impact.
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Somebody please add this to the metric article as an counter example for when people are talking about how easy imperial units are to deal with.
Admiral Gates (Score:5, Funny)
Nobody will ever need more than a 64 Megajoules rail gun.
Return of the Battleship (Score:3, Interesting)
power not the problem (Score:5, Interesting)
I believe that the time to fire is more likely dominated by the maintenance issues - making sure that the rails are perfectly straight, the warhead is correctly placed, etc. If you're off by even a little bit that sucker could destroy the railgun on the way out, costing you millions and making it inoperative until you're back home.
you're right (Score:3, Informative)
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The next generation of destroyers will have a turbine-electric powerplant, with the entire 80 MW available as electric power.
And regardless of current specs, if the USN adopts rail guns, they'll find a place to park another generator, if need be. 2.5 MW generators aren't that large.
Forget Replacing Cruise Missiles... (Score:5, Funny)
Come on, if you could fire a projectile 200 miles, you could just mount these on coastlines, serviced by ground-based power plants. True, it wouldn't replace navies ENTIRELY, but it would suddenly become extremely UN-economical to have one with even the slightest capability to get near a shoreline. Pushing back aircraft carriers 200 miles would severely reduce the flight time of the planes, which now have to fly a lot farther just to get to the coastline, let alone targets inside countries.
On the plus side, land-locked countries can now hunt whales for food. :)
Think twice. (Score:4, Insightful)
I believe a Navy does a lot more than just throw shells at buildings. That aside, you'd probably have a hard time hitting an even slightly moving ship with one of these at any range, let alone finding the ship in the first place without any of your own. After all, if the ship makes a slight random adjustment to course every six minutes or so (travel time of the shell at maximum range), then they're reasonably safe--especially if we assume that each gun could only fire at the maximum noted rate of ten shots a day, which means they get a shot every few hours or they blow all their shots in a few hours. Mounting these on shorelines is a waste.
Accuracy? (Score:4, Insightful)
Of course, if they get the rate of fire up high enough...
Chip H.
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The projectile that is fired DOES use GPS guidance. Look at slide 3 from this presentation from the Office of Naval Research.
http://www.onr.navy.mil/about/conferences/rd_partn er/2006/04thursday/dandrea_inp_track.ppt [navy.mil]
Power is relative, I guess. (Score:5, Interesting)
During a 5-second 'shot', when the stored energy was released, the motor, generator and flywheel would go from 480 to ~100 rpm, and dump 960 mega joules of energy into the coils of the experiment. You could feel the vibration in your feet anywhere you stood at the site, all the CRT's images would collapse due to the intense magnetic field generated. Then it was another twenty minutes before they could do it again.
Useless? (Score:4, Interesting)
I assume a gun like this would go onto a destroyer. I can't think of the last time a destroyer was used in any meaningful way in combat since WW2. If I remember correctly, the only reason the navy even keeps destroyers is because congress forces them to. I guess you could put it on a tank or something, but most conflicts that are fought now are on the ground and are more guerilla tactics than formal engagements. It's being shown in Iraq and Afghanistan that all the fancy new technology that the military keeps buying doesn't really mean squat when it comes to fighting a war.
Am I missing something here?
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I assume a gun like this would go onto a destroyer. I can't think of the last time a destroyer was used in any meaningful way in combat since WW2. If I remember correctly, the only reason the navy even keeps destroyers is because congress forces them to. I guess you could put it on a tank or something, but mo
Knocking out satellites? (Score:3, Insightful)
I saw something like this in use (Score:4, Funny)
alternative to nukes (Score:4, Interesting)
I mean, it's true that nuclear weapons have basically brought peace to modern nations through the principle/doctrine of mutually assured destruction (thats why, for example, all of Europe isn't Soviet Union now -- Russia forced to stop taking over stuff and be peaceful or else get nuked).
Maybe a new doctrine of mutually assured destruction through the crushing of cities through colossal projectiles with ungodly kinetic energy would still provide the umbrella of traditional MAD, but without that tiny little problem (which will never go away as long as there are nuclear weapons) of the potential of some lunatic dictator, who cares more about being in power than he cares about whether or not the rest of life on planet gets wiped out by radiation poisoning, getting his hands on nuclear weapon.
Railgun Campers (Score:4, Funny)
What 90% of Slashdot readers are thinking ... (Score:4, Funny)
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Paging Mr. Newton... (Score:3, Informative)
With that said, the Navy has had decades of experience in dealing with guns that make your whole battleship slew sideways when fired. There are ways to absorb and/or re-direct the recoil.
Re:Paging Mr. Newton... (Score:4, Informative)
You mispelled centuries.
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