The Most Powerful DIY Railgun

The US Navy is working on a few railgun projects that will eventually replace the largest guns on the fleet’s cruisers and destroyers. These rail guns will fire a projectile away from the ship at around Mach 7 on a ballistic trajectory to a target one hundred miles away. It’s an even more impressive piece of artillery than a gun with a nuclear warhead, and someday, it will be real.

most-powerful-non-military-railgunUntil then, we’ll have to settle with [Zebralemur]’s DIY mobile railgun. He built this railgun capable of firing aluminum projectiles through pumpkins, cellphones, and into car doors and blocks of ballistics gelatin.

All rail guns need a place to store energy, and in all cases this is a gigantic bank of capacitors. For this project, [Zebralemur] is using fifty-six, 400 Volt, 6000 microfarad caps. The MSRP for these caps would be about $50,000 total, but somehow – probably a surplus store – [Zebralemur] picked them up for $2,400.

These caps are just the power supply for the rail gun, and aren’t part of the structure of this already large, 250 pound gun. Luckily, with the seats down in [Zebralemur]’s car, they fit in the back of his hatchback.

These caps are charged by a bunch of 9V batteries stuck end to end. When the caps are charged, all the power is dumped into two copper bars in the gun, accelerating the aluminum projectile to speeds fast enough to kill. It’s an incredible build, but something that should not be attempted by anyone. Although this does seem to be the year that all danger seekers are busting out their electromagnetic projection flingers.

[via reddit]

107 thoughts on “The Most Powerful DIY Railgun

  1. Love the high voltage power supply :D 9-volts have such a high internal resistance, you could probably leave them connected when firing as long as the projectile doesn’t weld to the rails with no effect on shot count. (lots less safe though)

        1. OK. It’s been a while since I did the theory but you still need magnetic propulsion and this is using a non-ferric projectile so you have to induce an opposing magnetic field in a non-ferric conductive so you have to induce eddy currents somehow as the directly applied current has a mostly linear path. ???

  2. I’d love to see that with actual ballistic projectiles and a barrel system capable of hitting a target accurately that’s farther than 5 feet away. Could be a real monster after that.

    1. The trouble is rail degradation is really severe, I would imagine that aluminum is probably the worst in this regard. All of those sparks flying out of the end of the barrel are bits of the rail and projectile… The Iranian guy that rocketed to fame with his coilgun about 10 years ago (Mehdi Sadaghdar?) was using graphite doped with copper projectiles to reduce this, but I can’t remember if they were effective or not. Maybe a sabot style projectile would work.

      Also pretty hard to form the rails around a real cylindrical projectile, and you also have to modify the typical ogive profile to give more contact with the bore for more power transmission, something avoided in traditional guns.

      Because of the forces generated by the charge on opposing rails outward (splitting the rails apart) they are usually made in a square box form to be easily reinforced. If you look at most of the high power prototypes its 1/2″ steel with 3/8″ grade 8 bolts every 4 inches, with some sort of material to keep the rails electrically isolated from one another.

      I have often wondered if it would be practical to line a cylinder with copper and cut two helices opposed to each other the length of the barrel, much like rifling is cut into a bore. Keeping the copper in place would be difficult, especially torsion. Idk if the helix would induce a desirable spin to the projectile or not…

      Cooling is also beneficial to barrel life, iirc the navy is using filtered sea water to cool its rail gun barrels (it started doing this on battleships pre-WW2 on conventional cannons).

      For now, apart from the wow factor, you’ll get much more performance from gunpowder… Until we have a energy storage revolution with higher energy density batteries and capacitors man portable railguns won’t be practical.

      1. All good points.

        What about a two-stage? Square projectile casing launched in the first stage across the rails and either splits upon exit and launches a contained ballistic projectile. It would be like having a bullet, but instead of a cylinder casing, gunpowder, and a projectile, it would have a flat sided launcher. Or (and the logistics are gonna be complex for this) transition from rail to rifled barrel.

        1. If you look at the videos released on the Navy’s recent rail-gun prototypes, several videos show sabotted projectiles. The projectiles have a square pusher housing that drops away to reveal a central hyper-sonic dart as the projectile leaves the barrel.

          The Navy appears to have solved the rail erosion problem as well. They ofc won’t say how. But if they’re testing late state prototypes at sea, they can’t be wearing out the rails with each shot. (I’d guess at least 2000 shots)

          1. 120mm guns for tanks have way a shorter lifespan (heavily depends on what you fire), 400 shots with the less destructive (for the barrel) ammo is the usual number and nobody is complaining that much ;-)

            As for the Navy railgun – all proper railguns have (and have had) a square barrel crossection and use a discarding sabot, the Navy one has this weird, very thick arch the the back of the sabot to maximise efficiency…

    1. I meant that if the USA applied technology research to things other than weapons we might accomplish a lot. This technology could be applied to space travel, cross-country transportation, etc. Instead it’s being used to shoot stuff.

        1. True. I was primarily criticizing the military weapons development referenced in the article, not the man who made the DIY railgun. If he adapts it into something useful that would be awesome though and I’d love to see it.

        1. The problem I can foresee with a electro magnetic launcher is simple. The human body wouldn’t be able to survive the g-force of launching at Mach 7. It would likely crush you. It’s not practical unless we perfect cryo-stasis or something.

        2. You would use this as the motor. Of course you’ll need to find a way to destroy the thing a tad less. After all you’re just ejecting mass out one end. I don’t have the tools or info to calculate ISP right now, though.

    2. Included is Eisenhower’s farewell address in it’s entirety. Eisenhower clearly articulated what’s meant by the term. Anyone who misses it most likely would fail any exam required to be able to vote if such an exam where to exist. Everyone has their priorities what is important in life so it shouldn’t be that difficult why anyone would move from the USA to country that would meet their priorities.

  3. I thought one weighed the ballistic gelatin target, and suspend it from from a kind of pendulum, and record the maximum height to calculate the energy the projectile carried…

    1. Instead of weighing the projectile and measuring it’s speed (both quite easy nowadays) and thus getting far better measurement accuracy…
      The ballistic pendulum is a thing of the past, way too many variables.

      1. Yes and you need a very high number of Joules to create any ‘awesome factor’ due to velocity. However sparks and noise can generate much awesome with a smaller number of Joules so this build is extremely efficient at energy to awesome conversion.

      1. it doesn’t have to, sure, but whats the most probable outcome of developing such technologie? Besides, there are so many things wrong on this planet that hackers should invent solutions for – would be a while before “railgun” would be high priority on this list, dont you think?

        1. Just fun, realistically. It’s not going to replace the traditional weapons we have for actually killing people, any pistol would do a much better job. As far as the list of priorities go, if his aim is to have fun, then he’s done a good job, I think.

      1. That would have to be one hack of a railgun…
        In order to get through the atmosphere, you need to push it out of the way, so the object you want to get through has to be heavier then the amount of air it has to displace in it it’s path, and there’s a lot of air :P

          1. Question was answered incorrectly. They don’t need 100 miles straight and upward of roller coaster track.

            Groom Lake is 6 x 10 miles. The LHC is 17 mi round.

            Here is a landing procedure that experienced pilots use to land.


            Why not use it backwards to accelerate (think going up the parking garage) before straightening it out?

            Add to the a auto rotating cabin to ease human launch and you could stack it with a ‘Stellarator’ reactor rail design.

            Granted I haven’t done the math on distance/speed/revolutions.

            But very easily a shutdown open pit could be refurbished if the surrounding rock integrity is solid.


    1. I get that reference! And I still remember those key sequences, actually had to type in the first two, DQD and KFA, in a dream the other night, believe it or not. It was in “real life” (not a computer game. But not real life either cos it was a dream). But some keys appeared on a rock somewhere so in they went, felt much better for doing that.

      Then LAST night I had the weirdest dream ever. Had sex in it, real kinky shit, with Kyle’s Mom from South Park, among the other South Park women. Then after that a different one with guys.

      Know what they say, there’s no more fascinatingly interesting view into the parts of somebody’s mind that you certainly WANTED to see, than listening to them bang on and on about their dreams.

      They changed it to IDCLIP later. Boring!

    1. You can make a quick and dirty (and dangerous) charger out of a 12V AC inverter. Using a voltage doubler, you can get about 340V or so DC. It is just a matter of limiting the current to protect the inverter. All that for less than a batch of 9V batteries.

        1. Not anything like the sort of capacity you need for a railgun, it’s all about supplying huge amounts of amps, in an instant. I once read a paper capacitor of 1F would be the size of a kitchen.

          Are we sure that HAD’s description is accurate? 56x 6,000 uF capacitors? That’s hardly anything. Even at 400V. Would our guy have been better using a lower voltage but higher capacitance? I realise voltage counts as part of the energy equation, but the voltage is going to be almost nothing, dumped into essentially a short-circuit.

          Then again it’s hard to tell I suppose. The magnetic fields induced are going to oppose each other, providing a high impedance for the circuit over the flash of time during which it’s operating. So maybe you need a voltage of a certain level to do it. I wonder what the equations are for this sort of thing? I’m sure they’ve been thought of. If it was down to me I’d just throw Farads at it.

      1. You want something that can deliver lots of power i.e. lot of current to charge the caps. It is not unusual to find a 500W inverter, but not so for ignition coil. The caps are rated for 400V, so using 340V DC for charging isn’t too bad. Tweaking the inverter to give a slightly higher or lower voltage is pretty basic.

      2. Only 340V? My 12V to AC inverter (cheap “modified sine”) has a peak voltage of about 260 to 300V. Which makes sense as the peak voltage of mains current lies at about 315 to 320V (230V*SQRT(2)).
        But perhaps it makes sense to use a doubler and hack it to regulate the peak voltage down to About 190V. So you come close to 400V for the caps. I also would try to select the value of the doubler caps so the short circuit current would stay at a safe value, as an empty capacitor is essentially a short.

  4. Making a railgun is “trivial”, solving the rail erosion problem and making them efficient aren’t. How much of the stored energy is transferred to the kinetic energy of the projectile?

    1. Surely rail erosion isn’t going to be a problem for a hobbyist. It’s easy enough to replace them, they’re one of the simpler bits of the design. Nobody’s life is relying on them.

      As far as transferring energy, what are the main issues? I’d guess the main opposition to current flow is the induced magnetic fields fighting each other, limiting the speed you can dump current, which ideally needs doing all at once. I suppose the answer to that is lowest ESR possible for the caps. Why lots is parallel is good. You presumably can’t do much about the effective “coil” impedance, since the magnetic field is the point of the device. I guess wire thickness is going to matter a bit, not too much, since the power’s sent in such a short time there’s hardly enough to heat them up.

      I imagine this is something the US Navy has researched, though how much they’re willing to share might be a problem. Or is it obvious?

    1. First of all that was 70 years ago, what’s their excuse now? Secondly, it was mostly the large population of Russia that stopped the Nazis. That, and Hitler’s crumbling mental state, and the way he’d organised things so that nobody could countermand him, or even reason with him. From presumably his pre-existing mental state, being a bit of a dick, and a superhuman consumption of amphetamines.

      Even a couple of nosefuls makes you a paranoid nut. The vicious, gigantic arguments you can have, over almost nothing at all. And that’s just the boring old amphetamine sulphate we get in the UK, not the meth amphetamine that the Nazis had. Problem is you don’t realise how nutty you’ve gone. Drugs that don’t make you feel like you’re on drugs are the most insidious kind!

      Talking of irrelevant subjects, just what the hell went wrong with Star Trek: Deep Space Nine? TNG was great! DS9 was embarassingly ludicrous, when it wasn’t just pompous and boring. Finally an answer to why there are no toilets in Star Trek. Nobody on DS9 could untighten their anuses.

    2. But wasn’t the war against Imperial Japan Douglas MacArthur’s war? Yes Eisenhower coined the term In a warning, but very few of the business and government elite seem to believe it’s something to embrace rather something to keep a cautious, critical eye on.

  5. why blowing up the phone?
    I don’t like how people think cheap -> expendable.
    It requires hard work to make the phone, and a lot of pollution.
    There is absolutely nothing interesting in shooting a phone, but it shows that some people have too much economical power and no knowledge of how things are made. We share this f*cking planet.

    1. Too much economical power… You are talking about the guy that dropped $2500 on a trunk full of capacitors to tie to the 250lb rail gun, that apparently can’t break through a pumpkin(video won’t play for me), right?
      The thing, while cool, is really little more than an impressive toy.

      1. He was actually local to me, went to a nearby technical uni. I think he graduated and went back to Brazil.
        I knew folks who were in classes with him, and they didn’t sound too impressed. He was the son of some rich Brazilian trump clone, and their impression was that he just threw money at projects till something happened.

  6. A really photogenic target medium would be big blocks of ice. Just cut the tops off of 1gal milk jugs or 2l soda bottles, and use them to cast bocks of ice. They make a great big spectacular show of disintegrating when you hit ’em, and there’s no cleanup – the bits ‘n’ pieces just melt. :)

    1. Reminds me of “Use Of Weapons” by Iain M Banks. The protagonist asks for some garbage to shoot at, to practice firing his weapons. The ship points out there is no “garbage”, they have complete control over matter, everything is re-used completely. So the ship conjures up some blocks of black-tinted ice. After switching off the safety field that transfers all large energy blasts into another dimension.

      It’s a great book, btw. The format is a little weird, interleaved chapters, one set heading forward into the story, the other set heading backwards giving our characters’ history. And the AI drone is psychopathic!

      You’ll never look at a chair the same way again.

  7. You know what I’d like to see? A DIY compulsator, or compensated pulse alternator. Real railguns use these, not capacitor banks. Basically it’s a flywheel connected to an alternator that’s wired for high current, rapid discharge. The power density is much higher than an equivalently sized capacitor bank. Anyone working on one?

      1. Much of the research is classified, and capacitor banks take up too much space to be practical with mobile and some ship-bound applications. The compulsator is where it’s at until capacitor tech improves by more than an order of magnitude.

  8. Far out as far as it can do now Not going to be that interesting until the projectile can hit the broad side of a barn from several hundred feet out. Although that may require a connection to the grid or a hefty 3 phase power plant. Maybe a portable DC arc welder?

  9. “To see the world, things dangerous to come to, to see behind walls, draw closer, to find each other, and to feel. That is the purpose of life.”

    Dream big friend. Dream big.

    FYI, Please save the vid, as I find it harder to youtube search for it. Keep it light and aluminum oxide coated. You will need a cool suit.

    That said: Simo Häyhä. Don’t camp. Keep moving.

  10. Thats the exact reason I will go and leave Germany and move to the USA (if I will be allowed to :D ) because I want my taxes rather be spend for security than for bullshit social equalizing of damn lazy people…

    1. When you get here if you happen to be in the Cincinnati Ohio area I’ll happily take you to shoot some real guns (no rail guns yet sadly! lol). If your going to move here you might as well dive right in! LOL

      As for the navy rail guns being cooler then artillery fired nuclear weapons, I totally disagree. Just because we developed them 50 years ago doesn’t make them any less amazing! Nuclear weapons are an easy scapegoat for the anti-war crowd but the reality is they are the primary reason we haven’t already had WWIII.

      That said I tend to agree we should spend less money “projecting power” and more money on space exploration and exploitation, and more money on nuclear research (power, waste reduction, etc). Military R&D is fine and good, we get lots of useful trickle down from military R&D spending. We also get some trickle down from overall military spending (the military buying some outrageously expensive new tech has inadvertently pushed the costs down to the point that the tech then becomes profitable commercially though I can’t remember any specifics at the moment.. its late).

      TLDR; we could afford to shave a few billion off the top of military spending without putting the country at any risk.

      1. Nuclear weapons were the catalyst for the technology we have today. The simple transistor was a break thru developed for Thermal Nuclear Devices in order to improve reliability over the old vacuum tube technology, which had a very high failure rate. Making the weapons small enough for shipboard storage, handling and launching aboard aircraft was a goal of the Navy, much to the consternation of the newly formed Air Force, who at that time, viewed nuclear weapons as their domain. So much so, that they actually cancelled an aircraft carrier designed specifically around nuclear capability, the USS United States. As our knowledge of nuclear physics, nuclear electronics, and thermal dynamics grew, so did our sophistication, reliability, and yields. The weapons became smaller and the yields became larger. We were able to increase the percentage of material used, therefore requiring less material. Battlefield tactical weapons were created, such as projectiles fired from howitzers, and magnetic mines delivered by divers. What escapes most peoples knowledge is that most of these weapons gave the president the power to negotiate the SALT I & SALT II treatise, which in fact, were the demise of these very same weapons, and the folks trained to handle, maintain and repair them. The world is feature rich with the gadgets we have come to take for granted, such as cell phones, computers, pocket calculators, but very few know where that technology originated. As it was for those who maintained the thermal nuclear devices, so will it be for the old Gunner’s Mates who operated and maintained the big guns on the ships, as well as those artillery folks in the field. The rail guns of the near future won’t require as many to operate and maintain. The rapid fire capabilities of rail guns, and I might add, lasers, will make our battlefield weapons much more lethal at greater distances, with very little collateral damage.

  11. I wonder…could you possibly achieve greater muzzle velocity and less wasted energy by perhaps using a slightly higher capacitance and using four rail in a cross (+) with a rail on top, bottom, left and right? Could you use the same capacitor bank to power all four rails? It seems that, if applied properly, the doubled magnetic forces would double kinetic energy. This would definitely create more melting of the projectile, but would it be worth it to even try?

    1. Its really not an issue of muzzle velocity as general atomic has proven rather how can you use magnetic fields to rotate the projectile while accelerating using Lorenz field magnetics.

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