Atomic Awesome, Big Complicated Machines

Velocitas Eradico


The Navy has a new gun to play with

Good morning everyone.

The image above is a prototype of what could possibly be the future in the long line of powerful naval weapons: a railgun. This is not to be confused with “railway guns”, such as the huge cannons that the Germans made in WWI and WWII that had to be moved on railroad cars. A railgun, if you’re unfamiliar with the term, is a device that uses a huge amount of electrical power to fire a projectile at incredible speed at targets up to hundreds of miles away. Up until the last couple of decades, weapons such as this have been largely a matter of theory, with just small test models being built, but the Navy has been working on making it a practical reality, although they’ve been having a tough time selling it to Congress, but they’ve been working hard and have gotten a reprieve.

The Navy is making tangible progress, however. In December of 2010 they set a record for the world’s most powerful railgun by launching a 23 pound projectile at 5,500 feet per second using 33 megajoules of electrical energy, or about 1.5 million amps, stored in several very large capacitor arrays (some of my favourite things). The railgun used isn’t the one pictured above, but an earlier model one in the picture below,  after the jump.

Cathy Partusch, Dir. of Corp. Communication, ONR Cleared for Public Release

The record setting railgun

This picture is from 2007 when it was only rated at 32 megajoules. Here is a good video of the railgun and the supporting machinery, and views of the record breaking test shot:

[youtube width=”425″ height=”344″][/youtube]

Here’s a better video of the test shot:

[youtube width=”425″ height=”344″][/youtube]


A railgun works by sending a large current through two metal bars (the rails) separated by a gap. A movable metal conductor called an armature is placed between the rails completing the circuit. This makes the rails behave as an electromagnet, and creates a Lorentz force that pushes the armature down the rails and out of the end. It’s all so simple….

Another view of the lab unit

The concept of a railgun-type weapon has been around for quite a while. In 1918  a Frenchman,  Louis Octave Fauchon-Villeplee invented an electric cannon to fire metal projectiles which he patented, but it never really went anywhere. Then in WWII, those damned clever Germans dug up the idea, and made plans for building railgun anti-aircraft cannons. They were to be mounted in batteries of six that would fire at 12 rounds a minute, with the  ½ kilogram projectiles traveling at 2,000 meters per second. They would have been an extremely nasty weapon, but it was never built. After the war, the plans were discovered and generated a lot of excitement (Cool! Another superweapon!), and detailed studies were done, “culminating with a 1947 report which concluded that it was theoretically feasible, but that each gun would need enough power to illuminate half of Chicago.” Dang. Details, details.

DARPA did some tests making railguns in the 1990s (I think) and found that, yeah, you can make them work, but the heavy wear on the rails due to arcing and heat was a real problem, and the gun was only good for a couple of shots before it needed to be rebuilt. In 2005, the Office of Naval Research (ONR) started a project to develop an advanced electromagnetic railgun for the Navy, with an experimental gun making its first shots in 2008. The motto of the project is “Velocitas Eradico” roughly translated as “Speed Kills”. I approve. The goal is to develop a ship-mounted weapon that can fire 10 accurate shots a minute at targets 50 to 100 nautical miles away. They have a long way to go. On top of the severe wear problems, it needs to fire smart projectiles without destroying the guidance systems. Another big problem is that the current generation of Destroyers can’t generate enough electricity to charge the weapon without cutting off power to the propulsion systems, something that is generally considered to be a bad move, tactically.

Delivering the 32-megajoule prototype demonstrator

On January 30, 2012, BAE Systems delivered the first 32 megajoule prototype demonstrator, which actually resembles a naval gun rather than a lab construct. After they installed it and outfitted it with boatload of sensors (it’s the Navy, remember), they fired some low energy test shots, one of which is shown in this video:

[youtube width=”425″ height=”344″][/youtube]
That ungainly projectile that the officer is loading weighs around 40 pounds and is about as aerodynamic as an aluminum brick. I know they can do better than that, but I’m sure that there is a reason for it. Possibly there was a sale, and they got too excited and bought too many brick-faced projectiles. I’ve heard stranger stories.

The General Atomics company (the link will take you to a video) is trying to get into the game, and it looks like they have some good ideas. Here is their gun:

The General Atomics prototype railgun

It looks like we might see some interesting new weapons in the not-too-distant future.


Office of Naval Research

gizmag – U.S. Navy set to test first industry railgun prototype

General Atomics AWL

Wikipedia – Railgun – Video: Navy Fires Off Its New Weaponized Railgun



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  • Massive amounts of electricity on the deck of a ship and salt water, what could possibly go wrong.

    • The Professor

      Corrosion, for starters. They'll have to keep up on their painting.

      • FЯeeMan

        I need to start a gold-plated contact contracting business. Stat!

  • mr. mzs zsm msz esq

    So are those flames caused by the heat from friction and resistance of the armature moving? I immediately thought, why have it touch even? And why not use super conducting magnets for strong fields! And quickly learned that I am not the first to think of that:

    • The Professor

      I would imagine that complexity and cost were the biggest issues. Railguns are much simpler to build and don't require all of the cooling machinery that superconducting magnets require. Electrical power would be an issue too, as you still have to recharge the capacitor banks, but now you have to run the cooling machinery too.
      A coilgun cannon is a great idea though, and I imagine that they'll try it eventually, especially since DARPA is doing research on it. Although you'll have the military's factional disputes to deal with and the "not invented by us" problems that always crop up.

      • jeepjeff

        My shoddy, back-of-the-envelope analysis of railgun vs coilgun configuration is that railguns are just much more energetically efficient. Trying to suck a magnetic core into and out of a coil just doesn't have the same magnetic leverage as a railgun. It's a shame railguns are so hard on materials.

        • The Professor

          I suspected as much, but I was too lazy to research it, and field to field magnetic interactions can be a real bastard to sort out.
          Thanks for the quickie analysis. Need a job as a grad student?

          • jeepjeff

            The commute is almost certainly a problem (Davis, right?), and it would be a 75%+ pay cut… But weapons research, right? Make things go boom? I can't say it isn't temping. I have to warn you though, my GRE scores suck and my GPA on my BS is merely ok/pretty good.

          • The Professor

            That's fine, it was a jest anyway, aside from the fact that I don't want to get murdered in my sleep for messing with the GS program.
            And no, I'm not at Davis, although they do have some good people there.

          • jeepjeff

            Yeah, I figured it was a jest. Grad school doesn't fit in my life right now (I've thought long and hard about it). Leaving the comment might have been best, but I didn't feel like it.

    • The Professor

      Oh, and I'm pretty sure that all of the fire is from the armature arcing all the way down the rails. 1.5 million amps will give you a very nice fireball, believe me.

      • Mr_Biggles

        One of the articles I read said it is partially from the arcing as you say, but also from aluminum particles from the projectile reacting with air. I think aluminum dust itself is somewhat combustible.

        Why do you suppose an aluminum projectile is used? I would have thought something ferrous would be more suitable for this kind of thing.

        • The Professor

          Aluminum is a better conductor of electricity than iron or steel. Then why not copper? My guess would be cost, and perhaps durability. It's hard to find any real detail about the project, as much of it is classified.
          You're probably right about the aluminum making the dramatic flame, only it would be aluminum vapor, not dust, I believe. I'd really like to examine one of those projectiles after a shot. Fat chance of that happening.

          • pnkndssy

            There is a coating of Al dust on everything down range after the shot. A co-worker of mine has one of the targets on his desk at work. He had to scrub the powder of to clean it up. The target is very cool! A fist sized hole in a steel plate with a cuff of flare protruding a couple of inches from the back side.

        • jeepjeff

          They don't use ferrous (or rather, ferromagnetic) materials for the projectile because of the field configuration. The magnetic field generated by the current through the rails pushes on the current through the projectile. There isn't a way to magnetize the projectile that would improve the operation of the gun, but more current through the projectile at lower voltages does help (hence The Professor's explanation). And I'm sure they're using aluminum because the price difference between Al and Cu cannot be justified by the performance gain.

        • jeepjeff

          Oh, and aluminum dust is just a wee bit more than "a little combustible". Once you get your aluminum particles small enough, it becomes an explosive (making aluminum powder is very dangerous). Also, go over to YouTube and type "thermite" into the search bar. You're welcome.

          • GlassOnion9

            Thermite is really cool stuff. I enjoy what it does to a car when lit on the hood. I also enjoy the fact that it has to be lit with a magnesium fire.

          • The Professor

            If you enjoy experiments such as that, obtain a few ounces of very fine Al powder, 2 micron (~4800 mesh) or smaller. Wearing an appropriate filtre mask, use a fan to blow it into a small room that you no longer need. When you have a nice thick haze in the room, introduce an ignition source. And duck. It's quite impressive.

  • Number_Six

    When they get this thing into production, the next logical step is building the Space Battleship Yamato.
    <img src="; width="500" />

    • PowerTryp

      I preferred SDF-1 much more. Course we're thirteen years past the time the ship should've crashed here and three years after it should've launched. Sigh.

      <img src="; width="500">

    • The Professor

      But of course. It's so logical to turn a sunken WWII battleship into an interstellar spaceship. I'm amazed that they haven't done it yet. I'd like to see the Bismark in the skies…

  • OA5599

    But can it shoot an actual rail?

    [youtube dWSjE8DXZw4 youtube]

  • Railguns are wonderful, but someone on that project needs to work on their Latin. I was recently reminded on Hooniverse that my grasp of French is essentially nonexistent, but "Velocitas Eradico" is a different matter. It means "I, Speed, uproot [it]."

    I'll grant the figurative use of the verb in the sense of "utterly destroy" but really, unless this phrase is intended as a self-affirmation for Speed Racer to utter while gardening, it's a pretty poor effort.

    • The Professor

      Well, it was most likely coined by someone in the ONR, probably a PR person who isn't as familiar with dead languages as you are, and he thought he was being clever. His bosses thought it was cool and tough sounding, and there you are.

      • I don't doubt it. The other problem with that motto is that although Latin does have abstract nouns, the Romans weren't generally keen on using them. I'd go with ACCELERO⋅VT⋅PVLSAM (or, if one must, Accelero Ut Pulsam) instead. This encompasses enough ambiguity so that it can be taken as "I impart speed so that I may strike" or "I am quick for the purpose of pushing it along" and so can refer to the action of the gun either upon the target or upon the projectile. It's multipurpose!

        If one really wants a way of saying "speed kills" instead, well, take your pick:

        <img src="; width="300">

        • The Professor

          Now there's a blast from the past. I still have my collection of the Fabulous Furry Freak Brothers comics around here somewhere.

          Yes, I'm sure that your version is more grammatically correct, but the Navy's is more aesthetically pleasing to the average undereducated military hack and average congresscritter because it resembles English words that they understand (such as it is), and that's who it's intended to impress. I'm sorry, but the knowledgeable opinions of mineralogists from a University in the Northwest don't factor in. Even if you do go launch rockets in the high desert with college girls.

        • texlenin

          or maybe, "Thru speed, I uproot my own gun-mount"?

  • GlassOnion9

    Holy hell.
    That General Atomics Boeing projectile is obscene. 7 km with 0 deg elevation. That's some damn fine ballistics.

    • The Professor

      Yeah, and that's after punching through the 1" steel plate. Lots of kinetic energy in that little bullet.

  • theTokenGreek

    I wouldn't be surprised if the projectile was intentionally not aerodynamic… they've only got so much real estate, y'know

    • The Professor

      Hmmm, that would be a problem, wouldn't it, although I would hope that they have a big dirt pile along their back fence to catch stray shots. It's bad PR to lob 40 pound chunks of aluminum into the local business district at several thousand meters per second.

      • mr. mzs zsm msz esq

        Unless you are a TV show like Myth Busters, or the US Army in Germany. Wait that was bad PR and why they do some much training in Poland and Romania now.

  • pj134

    <img src="; width=500>
    <img src="; width=500>

    … It's time to bring back the New Jersey. I bet trading all of the 2700 lbs out, even for more 100 lbs shells would save enough weight to put in something like a couple dedicated generators. Just think, four giant rail gun turrets.

    Are they thinking of building small scale ones that fire rapidly with a lower range/velocity? That could be a pretty effective anti aircraft gun with a small projectile and a good targeting computer.

    • FЯeeMan

      That sounds like a recipe for a good anti-anything gun with a small projectile and a good targeting computer.

    • The Professor

      I think using the New Jersey is a great idea. Leave one turret of 16" rifles for short range bombardment and mount railguns in the other two for accurate long range fire. There should be plenty of room and weight saving there to mount dedicated generator machinery, maybe even enough for a coilgun or two. It would be glorious to behold in battle, and give battleships a reason to be feared again. Unfortunately, they still make a big, easy to sink target, unless we get really good at making railgun/coilgun AAA.
      What the Navy actually has planned, I don't know. They're not giving out a lot of info on where the railguns might be deployed, when and if they get them working up to spec.

      • pj134

        Yeah, that was the small railgun AA part of my comment. Although, maybe a flechette style round out of a big one would be more effective if they could figure it out. Might have some collateral damage issues though. Between the CIWS and whatever else they're developing, there has got to be enough of something to make it a floating fortress. For something like this, a battle ship seems like the answer. You need enormous amounts of power, and the only thing I can think of with enough space is that or an aircraft carrier.

        The main outdoor concert venue for the Philadelphia area is in Camden and BB-62 is mothballed there. It is quite something to see. It's a strange thought that it could fire a 2700 lbs round to within a couple miles of where I live and it takes me an hour to drive down to Camden.

  • jeepjeff

    There is a very simple solution to the "have to turn off the power to the engine to fire the guns" problem. Second Nuclear Reactor! When you need more power, there is nothing like more power to solve your problems.

    • FЯeeMan

      I was confused by that statement. Isn't that what the capacitors are for, holding a charge to fire the gun? How long does it take to recharge them all? Could the power be shifted to charging the guns, while allowing the boat to glide, then once charged, send the power back to the drive? I'd think the somewhat sudden speed changes would make for a somewhat more difficult targeting solution for the enemy, too.

      • jeepjeff

        If you are trying to fire volleys as fast as possible, you'll never have the ability to use the engine. The capacitors are there to take a continuous stream of electrical energy at a lower power and store it until you have them filled enough to fire a round. Then all of the energy in the capacitors is discharged over a much shorter time (fraction of a second) and therefore at a much higher power to fire the gun.

        So, the process is charge for a minute, fire the gun for a few milliseconds, charge the gun for a minute… At maximum fire rate, there isn't time to run the engine. The problem is picking between shooting and going. You can drop your rate of fire, but you are then putting less flak in the air and probably prolonging the fight. I wouldn't want to pick between shooting and sailing if I were a naval captain.

      • The Professor

        It's hard to fool tracking radar once it has found you, especially if you're a large ship. You need the ability to maneuver quickly and repeatedly to have any hope of dodging whatever they're shooting at you, especially missiles.
        The capacitors hold the charge for the shot, and the shot drains them very nearly completely. The time to recharge big capacitor banks like that varies as to how much juice you can shovel into them without overheating the lot and damaging the system. At a guess (and a very wild one at that) I'd expect 5 to 10 minutes from what I saw of the hardware in pictures. Maybe a bit faster if you're a tricky engineer and have tuned the charging process well.