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Homemade Gauss Gun
bonzoesc writes: "I'm sure we all remember getting owned by some railgun-wielding kid in Quake2. Ever wanted a way to get back? Enter the Homemade Gauss Rifle. Requires wooden ruler with groove down the middle to serve as the rail, steel balls that can roll down the groove to use as projectiles, and magnets to store and redirect energy. Physics is fun!"
Do Doctors (Medics) get guns that are twice as fast as those given to us, the average Joe?
I knew this would happen. First you had Physics for Game Developers Now you have Game Weapons for Physicists.
Sigh, what's next, perpetual motion?
(At least this isn't a homemade BFG -- I'd be really scared then)
Read the article, especially the part labelled "Why a circular track will not be a perpetual motion device"
--
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Eh.. i'm disappointed. I initially misread that as "degauss rifle"..
After discovering in computer labs that hitting the "deguass" button on a monitor will cause the monitors nearby to trip out very slightly for an instant, i had these vague daydreams of rewiring whatever it is in the monitor that makes it deguass to be unreasonably strong, so that hitting "deguass" would cause the monitors of all the computers in the lab or whatever else is in a 40-foot radius to be degaussed at once, Matrix EMP-blast style. This would probably break stuff, but then that's the point, i suppose.
I dunno.. i guess having instructions on how to build a mini-rail-gun really is much cooler, but still, i wonder if the guass-blast idea is possible.. and if it were, modifying the idea to create a gun you could stick at a monitor and pull the trigger to deguass it would be really funny. Alas, there's no practical use for such a thing as far as i can tell, and it isn't really *that* interesting, so i don't really care enough to do any research on the subject, so for now, it looks like i'm going to have to limit myself to putting an electric pencil sharpener next to the monitor, sticking in pencils, and giggling.
Irritable, left-wing and possibly humorous bumper stickers and t-shirts
. . . about 'Gauss Guns' can be found here
Your hair look like poop, Bob! - Wanker.
you didn't just give a bunch of undersexed, over hormonal, arrogant teenagers instructions on how to build a DANGEROUS WEAPON, now, did you?
-ugh-
:)
I guess this is just too damn good to pass up to be waiting for a slashdotted site to load... no pictures, but here's the text.. should satisfy your needs. Enjoy!
Experimenting with magnetorheological fluids.
Suspending a magnet in mid-air.
Levitating pyrolytic graphite.
A Gauss Rifle: A Magnetic Linear Accelerator.
Building a Curie-effect heat engine.
Going further:
Superconductors.
The Gauss Rifle:
A Magnetic Linear Accelerator
This very simple toy uses a magnetic chain reaction to launch a steel marble at a target at high speed. The toy is very simple to build, going together in minutes, and is very simple to understand and explain, and yet fascinating to watch and to use.
The photo above shows six frames of video showing this toy in action. Each frame shows 1/30th of a second. In the first frame, a steel ball starts rolling towards a magnet taped to a wooden ruler. In the second frame, a second ball can be seen speeding between the rightmost two magnets. By the third frame, the accelerator has sped up so much that the ball that is seen leaving the left side of the device is just a blur as it smashes into the target. One ball, starting at rest, has caused another ball to leave the device at a very high speed.
The materials are simple. We need a wooden ruler that has a groove in the top in which a steel ball can roll easily. Any piece of wood or aluminum or brass with a groove will work. We chose the ruler because they are easy to find around the house or at school or at a local stationery store.
We need some sticky tape. Again, almost any kind will do. Here we use Scotch brand transparent tape, but vinyl electrical tape works just as well.
We need four magnets. Most any type will do, but the stronger the magnets are, the faster the balls will go. Here we use the super strong gold-plated neodymium-iron-boron magnets we have made available in our catalog for the other projects. They work great.
We will also need nine steel balls, with a diameter that is a close match to the height of the magnets. We use 5/8 inch diameter nickel plated steel balls from our catalog.
The only tool we will need is a sharp knife for trimming the tape.
We start by taping the first magnet to the ruler at the 2.5 inch mark. The distance is somewhat arbitrary -- we wanted to get all four magnets on a one foot ruler. Feel free to experiment with the spacing later.
With the sharp knife, trim off any excess tape. Be careful, since the knife will be strongly attracted to the magnet.
It is very important that you keep the magnets from jumping together. They are made of a brittle sintered material that shatters like a ceramic. Tape the ruler to the table temporarily, so that it doesn't jump up to the next magnet as you tape the second magnet to the ruler.
Continue taping the magnets to the ruler, leaving 2.5 inches between the magnets.
When all four magnets are taped to the ruler, it is time to load the device with the balls.
To the right of each magnet, place two steel balls. Arrange a target to the right of the device, so the ball does not roll down the street and get lost.
To fire the gun, set a steel ball in the groove to the left of the leftmost magnet. Let the ball go. If it is close enough to the magnet, it will start rolling by itself, and hit the magnet.
When the gun fires, it will happen too fast to see. The ball on the right will shoot away from the gun, and hit the target with considerable force. Our one foot long version is designed so the speed is not enough to hurt someone, and you can use your hand or foot as a target.
How does it do that?
When you release the first ball, it is attracted to the first magnet. It hits the magnet with a respectable amount of force, and a kinetic energy we will call "1 unit".
The kinetic energy of the ball is transfered to the magnet, and then to the ball that is touching it on the right, and then to the ball that is touching that one. This transfer of kinetic energy is familiar to billiards players -- when the cue ball hits another ball, the cue ball stops and the other ball speeds off.
The third ball is now moving with a kinetic energy of 1 unit. But it is moving towards the second magnet. It picks up speed as the second magnet pulls it closer. When it hits the second magnet, it is moving nearly twice as fast as the first ball.
The third ball hits the magnet, and the fifth ball starts to move with a kinetic energy of 2 units. It speeds up as it nears the third magnet, and hits with of 3 units of kinetic energy. This causes the seventh ball to speed off towards the last magnet. As it gets drawn to the last magnet, it speeds up to 4 units of kinetic energy.
The kinetic energy is now transfered to the last ball, which speeds off at 4 units, to hit the target.
When the device is all set up and ready to be triggered, we can see that there are four balls that are touching their magnets. These balls are at what physicists call the "ground state". It takes energy to move them away from the magnets.
But each of these balls has another ball touching it. These second balls are not at the ground state. They are each 5/8ths of an inch from a magnet. They are easier to move than the balls that are touching the magnet.
If we were to take a ball that was touching a magnet, and pull it away from the magnet until it was 5/8ths of an inch away, we would be adding energy to the ball. The ball would be pulling towards the magnet with some considerable force. We could get the energy back by letting the ball go.
After the gun has fired, the situation is different. Now each of the balls is touching a magnet. There is one ball on each side of each magnet. Each ball is in its ground state, and has given up the energy that was stored by being 5/8ths of an inch from a magnet. That energy has gone into the last ball, which uses it to destroy the target.
Speed and kinetic energy
The kinetic energy of an object is defined as its mass times the square of its velocity. As each magnet pulls on a ball, it adds kinetic energy to the ball linearly.
But the speed does not add up linearly. If we have 4 magnets, the kinetic energy is 4, but the speed goes up as the square root of the kinetic energy. As we add more magnets, the speed goes up by a smaller amount each time. But the distance the ball will roll, and the damage it causes to what it hits, is a function of the kinetic energy, and thus a function of how many magnets we use.
We can keep scaling up the gun until the kinetic energy gets so high that the last magnet is shattered by the impact. After that, adding more magnets will not do much good.
Why a circular track will not be a perpetual motion device
I have been getting a lot of mail asking what would happen if we made the track circular. Would we get free energy? Would the balls keep accelerating forever?
I have been tempted to reply with the famous quote: "There are two kinds of people in the world -- those who understand the second law of thermodynamics, and those who don't".
However, I am not the kind of person to leave an inquiring mind unsatisfied, and it is more productive (and kind) to explain in a little more depth what is going on.
Suppose you made a circular track, and put two balls after each magnet. When the last ball is released, it encounters a magnet that has two balls at the ground state. There is no energy to be had from this magnet. The ball just bounces back.
Now suppose you had placed three balls after each magnet. When the last ball is released, it hits a ball that is 5/8ths inch from the magnet. It has not gained much momentum, because most of the momentum gained is in the last half inch as the magnet pulls much stronger on things that are closer. But the ball has enough energy from previous accelerations to release the next ball. However, that ball has less energy than the ball that caused it to release. It may have enough energy to release another ball or two, but each ball that is released has less energy than before, and eventually the chain stops.
You can show by inductive logic that no matter how many balls you stack in front of each magnet, eventually the system stops.
To estimate the losses due to heating the balls as they compress when hit, consider a plastic tube standing upright on a table. Place one steel ball at the bottom of the tube. Now drop another ball into the tube, so it hits the ball at the bottom, and bounces back up.
Now measure how high the ball bounced. If it bounces halfway back up, the losses are 50%. Perform the experiment for yourself with the balls from the Gauss Rifle. How high does your ball bounce? Send me mail with your results.
If you read to near the end of the article it states that scaling the fun up past a certain degree would indeed cause the end magnets to shatter. The force of two of the magnets coming together is larger than that of one of the little ball bearings hitting one of them. Neodymium magnets will easily shatter if you drop them on the floor as well.
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I didn't want to leave this space blank.
That should be "scaling the gun up past a certain degree", although "fun" works too.
The 2 minute posting rule sure does suck.
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I didn't want to leave this space blank.
Now can we have an article on how to make the BFG?
C'mon, please? I wanna know the physics behind whatever the deal is with that "cone" thing.
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Strictly speaking, this is not a gauss gun. A real gauss gun would use the Lentz (sp?) effect or something similar to accelerate the ball down the rails; this weapon, however, is built entirely out of plain old permanent magnets and kinetic energy. Actually, I suppose that maglev trains could be considered as gigantic gauss guns also, though they do not use the Lentz effect.
>|<*:=
Wow, this is exceptionally clever. The only other gauss rifles I've seen talked about used electromagnets and big-ass power.
It makes me wonder... could this scale? What if you built a big version with, say, 50 pound explosive charges (delayed fuse, of course) and big magnets? It seems like with enough phases, you could make a pretty devastating launcher. And I bet it would be pretty damn accurate, too.
Sometimes it's best to just let stupid people be stupid.
Some kid will make the gauss gun,...authorities will find out about it, and claim that he was going to use it to shoot up some kids at school.. it will be taken as further evidence that Computer games (Quake) cause violence in children... yadda yadda yadda...
- Tempestdata
Mirror please, this is important stuff!
Here's a coil gun I found on google.
Instead of using fixed magnets to release the energy of the balls hitting each magnet in sccuession, this coil gun uses a series of timed pulses to accellerate the projectile down the length of a tube. That's a block of concrete in the photo, and I think the black spike in the top left corner is the projectile.
http://www.resonanceresearch.com/prod06.htm
From what I understand, this gun is basically the same thing as the "Newton's Pendulum" toy that clacks back and forth, but with the addition of magnets between the balls, and some distance, to cause the balls to all pick up speed so that the last one gets a lot of kinetic energy transferred to it.
Scaling it up would seem feasible, but the problem would be the shattering magnets, as well as to "reload" you would have to physically move each ball back to the starting point.
Here is where I wonder if this thing could be made "better". The problem is getting a magnet as strong as the ones used, but doesn't shatter - but I think it can be done...
Get a non-ferrous tube - an alluminium or piece of PVC pipe would do fine. Get it with an inside diameter just smaller than the ball you want to fire.
Now, wind up some "double ended" electromagnets - use very fine magnet wire, and do an excelllent job winding the magnets. Use a steel core, and wind them to the thickness of the inside diameter of the tubing. You need these electromagnets to be really strong.
Now, cut 1.5 or 2 inch lengths of the tube - put the magnet on one end, and a ball - secure the magnets extremely well. Then, "stack" the tubes together to make a long tube, so that there is a magnet and a ball between the two magnets.
One end (the "breech") leave a 3 inch piece of tube, and build some kind of "firing mechanism" (spring loaded or something to propel the ball against the first electromagnet). Do the same on the other end, but just the tube - no firing mechanism - you may want this end to be a little longer.
To load and fire:
Get a real big-ass current capacity power supply, and hook the magnets up to turn them on. Don't turn them on yet - tilt the tube up to cause all the other balls to fall to the magnets, then turn on the magnets. Load the ball on the front end (the firing chamber end), and a ball into the firing mechanism. Fire the ball - and, if everything goes right (and my back of the napkin calcs are correct - yeah right), it should do the same thing as the small version, only more powerful (maybe), and reloadable!
Reason is the Path to God - Anon
Instructions to build a gun that shoots a magnet at 2KM/second. Yes you read correctly. Get a 3 meter long pipe made of pure iron. Coil 400km of thin copper wire around it. Buy a cylindrical magnet, the strongest you can get, that fits inside the pipe. Buy the fattest AC/DC converter around (or build it yourself...) and plug it in a 5000 Volt power supply (think neighbourhood electrical supply). Connect this to the 2 ends of the wires around the pipe.
Oh ya, make sure it's pointing the right way around.
My physics teacher did this while he was in university. They shot a concrete wall 2 feet thick and the magnet went through. The velocity was 2KM/s.
Imperium et libertas
Autocracy and freedom
mirrored, to avoid the Slashdot effect... http://spiff.homelinux.net/gaussgun/
When I read the title, I couldn't help thinking about burned spot in one of my old dorm's carpeting. A classmate of mine build a small rail gun using electromagnets, unfortunately during a test the coils melted, which left a very interesting splotch of solidified metal and burnt carpet.
It's nothing like the Quake rifle. I tried killing *THREE PEOPLE* with mine, and all it did was hit them in the head a little.
What a waste of time!
- A.P.
"Remember when the U.S. had a drug problem, and then we declared a War On Drugs, and now you can't buy drugs anymore?"
This is a neat little physics project, but it isn't a guass gun. A real gauss gun uses Lenz's law to propel the projectile. (It's can be a very powerful law, hehe...). The problem is that a real gauss gun of quake-like power would be much to large to carry. But they certainly are very cool.
----
All of whose base are belong to the what-now?
. . . although 'gauss'/'rail' guns may seem fun and interesting projects, unless your a really knowledgeable in the electical field, these are things you just shouldn't try on a large scale. You're dealing with large ammounts of heat and electricity which could explode, burn, shock and otherwise injure youself and others. Safety First!
Your hair look like poop, Bob! - Wanker.
Not quite. The magnets create a magnetic "force field". As you recall from physics 101, energy is defined is force times the delta of distance, not force alone. The energy of separating the magnets is not 'released' during this experiement, as the magnets do not move. Thus, the energy comes from your hand placing the balls which move.
Gravity also does not impart energy to falling objects; the objects already have energy relative to the earth, and actually lose energy to the earth on impact.
Bah! I was that railgun-wielding kid in Quake 2!
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"One touch of Darwin makes the whole world kin." George Bernard Shaw
The heat loss due to friction is enough to bring this "perpetual motion" machine to a halt. There is no way in the universe to convert from one form of energy into another without some loss to heat.
--If you code for the exceptions, the rules fall into place
A while back in G&A I think I saw an article about stun gloves which took the components of a stun gun and housed them inside a leather glove. You pressed down on a trigger and the electrodes were in the cuff of your hand between your index finger and thumb. All you had to do was grab somebody and they were in for a shock.
I'm a loner Dottie, a Rebel.
I've spotted multiple errors in this person's page. It looks like he was cribbing notes from a more informed paper.
Problems I've found:
The authour claims that coilgun coils attract the projectiles. This is not correct. They work by repulson (by Lenz's Law, the induced field in the conducting slug repels the coil's field).
The authour does handwaving towards the 3-body problem to support his claim that you can't figure out what the best configuration of a coilgun is. These are completely unrelated problems. The 3-body problem is hard because the system a) has no general closed-form solution and b) is chaotic, so you can't even approximate a closed-form solution for many configurations.
A coilgun, on the other hand, just has more variables than you need. You don't have one optimal coilgun - you have an infinite number of optimal coilguns. Pick some of your parameters to be convenient, and solve for the others.
It's not hard to calculate how strong the induced field will be in a coilgun, or the force transferred to the projectile. It's also not hard to calculate how a capacitor-driven system will behave (hint: consider the coil's inductance with and without the slug inside it, and you can figure out how the energy transfer works).
If you're building a tabletop coilgun, you don't have to worry about energy storage. Just get a good DC supply, set up the coils in parallel with capacitors to get a nice LC tank circuit, and set up a transistor on each coil driven off an extra turn of the coil (or a secondary coil) just as you'd set up an RF signal generator. You're going to put at most a few hundred joules into your projectile (and that's if you're heaving aluminum pipe segments across the street). Exotic solutions are only needed if you're trying to shell a neighbouring city.
As driving frequency goes up (or pulse length shortens), inductive effects become important. This is how a real coilgun works - it's driven by inductive repulsion of a conducting slug. If you have an iron slug, a) attractive and repulsive forces will fight each other (or you can think of it as induced currents shielding the slug from your applied magnetic field).
Magnetic slugs only work for tabletop devices with slow firing speeds.
He's using a metal pipe as a guide for the projectile. A closed pipe would shield the inside of the tube just as a conducting projectile shields itself. He cuts a slot through the length of the pipe to avoid this, but you still have very high induced voltages around the pipe. A coilgun that switches at any decent speed with a strong magnetic field will induce currents that arc across this gap.
If you want a projectile guide, use rails.
If you want an elegant solution, let the slug move through open air and use secondary coils to adjust the geometry of the magnetic field as the projectile passes through to nudge it back into line if you notice it drifting. But this is not trivial to implement.
Old EA game made by Bullfrog. Lots of fun. The gauss gun in that game looked like an oversized pistol IIRC, and it made big explosions.
It's not enough to bash in heads, you've got to bash in minds. - Captain Hammer
You can also use a large soldering iron or an electric drill to degauss monitors. A soldering iron contains a coil that generates an oscillating magnetic field at 60 Hz. I use this technique to degauss my arcade video games.
Oh yeah, don't actually touch these things to your monitor! You're just using the magnetic fields from them, not the business ends.
{joke}
For helping terrorist manafactur weapons that could cause mass destruction. Anyone who has viewed this page and learned something from it needs to IMMEDENTLY turn themselves into the local FBI and be detained for trial.
This message brought to you by the Local FBI and National Security commision.
{/joke}
-THIS SPACE FOR RENT!
Back in high-school for Honors/Advanced Physics I took it upon myself to build a rail-gun, you know - something that could be cool (everyone in high-school thought Quake/Doom was the shiz) and somewhat useful (provided you needed to drive a projectile at 2 to 3 km/sec). The other students were building oh I don't know weird tinker-toys like reverse-osmosis water filtration and a electrolysis something-or-other (a guy the semester before built a tesla-coil using IBC root-beer bottles as capacitors - turned out he had wayyy more capacitance than needed and not enough current) but I wanted to make something that blew stuff up.
:) So a couple hundred dollars later and I have some copper rails fixed to a base (some wood ;)), a whole lot of 2ga. wire (friend's dad worked for the electric company), and some .9F of capacitors hooked up to provide the juice.
.9F of capacitance (after working out the numbers) proved to be far too few amps to do anything but make a whole lot of sparks. Actually I managed to vaporize some of the smaller projectiles with only a small scrap of what was left pitifully dribbled out of the end of the gun. In any rate, after researching further, I found some 5 and 10F capacitors which would've done the job nicely could I have afforded the several thousand dollars it required to buy one.
:)
So I went to work assembling materials for the gun.. I didn't worry about the math behind why rail guns worked, all I knew is that it did plenty of damage in Quake.
Two things I learned:
1) You need a fuckton of capacitance to really achieve massive current (talking hundreds of thousands of Amps needed)
2) You also need an electronic switch instead of a mechanical switch so you don't lose said Amps to welding the switch to itself.
So I guess the moral of the story is if you don't have $10M in defense contracts you're not going to get a good rail-gun built since it requires MASSIVE amperage to create a plasma to launch your armature out of the weapon. And Capacitors are not tiny objects, so the likelihood of a 'Eraser'-style railgun are slim to none unless someone magically comes up with a much more compact and higher-capacity capacitor (which can still discharge at 1/1000th or better of a second).
The problem with a coil gun is that you need massive voltage plus some sizeable amps, which is generally very hard to come by. Your local mains circuit won't provide enough voltage. Although you could push it through a transformer you would need a very large and bulky one, and then you still probably would wind up with not enough amps to do the job. Most capacitors work at low enough voltages that a commodity (e.g. plugs into your regular wall socket) transformer could easily provide it, but achieving enough capacitance is both cost and size prohibitive (ignoring the rail mass loss due to vaporization).
Stupid Quake.
Thanks,
--
Matt
If You observe system in its initial "armed" condition you will find that it is not in its lowest possible energy configuration. Steel balls that are not immediately adjacent to magnets, do have higher potential energy than the balls touching the magnets. After firing, all the balls (except the projectile) are touching the magnets, meaning that the system has lower potential energy. The difference is the kinetic energy of the projectile.
You are, of course, right when you say that initial energy of the system came from the hands of the person who arranged the balls.
Now let's get semantics straight.
>However, none of the fixed magnets imparts energy to the ball
When the kinetic energy of the particle is enhanced at the expense of the system's potential energy (for the conservative system), the common expression in physics literature is that "field imparted energy to the particle". The expression: energy is "released" is also quite common and it simply means that system is in the configuration with lower potential energy.
Now let's get you straight.
>The energy of separating the magnets is not 'released' during this experiement, as the magnets do not move.
Indeed magnets did not move, but the balls did and the potential energy of the system is lower....
I was able to get one of the balls off the board a few tiems, but never did it have enough force to knock over a tape dispenser. Maybe quality parts would yield better results.
Urgo: "I want to live. I want to experience the universe and I want to eat pie!"
Jack: "Who doesn't??"
I remeber reading a review of those cool rare earth magnets on Dan's Data.
:)
The link to the article is here The link for where to cool magnets on his page is here
Now we just have to wait for a slashdotter to build a large version of this and use it to smash some watermelons
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C-X C-S
Mind now, or you'll take someone's eye out with that!
One boy at the university I studied electricity, one year younger than me, died while disassembling a TV.
Yes, you read well, he died because of remanent current in the electrical circuit (capacitor+inductive).
When I was younger, I decided to wire a 12V DC engine to the 220V AC network. Oh and I had opened the engine. Guess what, it burned and the explosion burned my face (though lightly).
Take care.
Men are born ignorant, not stupid; they are made stupid by education. Bertrand Russel
If you want to know how to build a REAL railgun, try this. Admittedly, its a bit harder to build.
The whole site is cool, browse around. I love the hydrogen bomb (chemical not nuclear). The levitating magnet's cool too. Now, to build that gun...
When in high school, a buddy of mine and I made a magnetic gun of sorts by taking magnet wire (think 24 guage, laminated, solid core wire) and wrapping it around a piece of 1/2 inch pvc pipe about eight times or so. Then, by running a very powerful DC current through the wire, it turned tha apparatus into a very powerful solenoid, of sorts. If you put a projectile in one end, turned on the power, and disconnected it before the projectile reached the middle of the tube, it would continue out the other side of the tube for some distance. I think the final version was able to shoot a small wood screw about 30 feet or so...
After doing further research, I've come across a second operating principle used to make coilguns, which is closer to what the original poster described.
As a conductor resists changes to the local magnetic field (Lenz's Law, cited above), if you set up a moving magnetic field, the projectile will tend to follow it.
Note that the projectile is not "attracted into the coil", as the original article stated. Rather, if you're turning coils on and off in sequence along the gun, the projectile will be repelled by the moving field as it approaches, and dragged along with it (attracted) as it passes. The projectile *won't* just follow along with the first pulse in the moving field, either - it's just tugged briefly in the same direction. You'd have to send a train of moving field pulses over it to bring it up to the speed of the train, and it'll never quite get there (as the speed of the projectile approaches that of the moving pulse train, the pulses pass with lower frequency, so the projectile's efficiency as an inductor drops).
You don't gain much drift-resistance, either. While the projectile is no longer actively perturbed off-axis (as with the previous style of coilgun I described), nothing keeps it on the axis either. You still need active correction (or rails).
You're also wasting more power, because you have to keep many coils (those around the projectile) oscillating instead of just the coil behind the projectile.
This coilgun still does not require a ferromagnetic projectile, though ferromagnetism doesn't actively harm this type of gun.