Railguns: Making Metal Go Fast Using The Lorentz Force

February 24, 2026 by Maya Posch 49 Comments

In science fiction, the use of gunpowder-based weapons is generally portrayed as something from a savage past, with technology having long since moved on to more civilized types of destructive weaponry, involving lasers, microwaves, and electromagnetism. Instead of messy detonating powder, energy-weapons are used to near-instantly deposit significant amounts of energy into the target, and railguns enable the delivery of projectiles at many times the speed of sound using nothing but the raw power of electricity and some creative physics.

Of course, the reason that we don’t see sci-fi weapons deployed everywhere has arguably less to do with today’s levels of savagery in geopolitics and more with the fact that physical reality is a very harsh mistress, who strongly frowns upon such flights of fancy.

Similarly, the Lorentz force that underlies railguns is extremely simple and effective, but scaled up to weapons-grade dimensions results in highly destructive forces that demolish the metal rails and other components of the railgun after only a few firings. Will we ever be able to fix these problems, or are railguns and similar sci-fi weapons forever beyond our grasp?

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A row of electromagnetic coils fastened to a metal track

Propel Paper Planes, Bisect Sausages With Electromagnets

November 14, 2021 by Chris Wilkinson 7 Comments

Are you still launching paper airplanes using your hands? That’s like a baby’s toy! [Tom Stanton] and his homebrew electromagnetic rail launcher are sure to bring your paper airplane game into the 21st century.

To be fair, these kinds of linear motors can be used for more than just launching paper airplanes, and can already be found in niche industrial applications, mass transportation systems and roller coasters. And, yes, the potential to leverage electromagnetism in the theater of war is also being vigorously explored by many of the world’s superpowers in the form of Gauss rifles and railguns. In the meantime, the video (after the break) proves that it’s entirely possible to build a rudimentary yet effective linear motor in your makerspace, using relatively basic components and fundamental physics.

In short, these launch systems use electromagnetism and well timed electronics to propel a mass of magnetic material down a straight (or sometimes curved) track. Multiple pairs of coils are placed along the track, with each pair subsequently energized by high current as the payload approaches. By using many coils in succession, the mass and its payload can be accelerated to high speed.

While a homemade rail launcher is unlikely to turn the tides of war, [Tom Stanton] explores their lethal potential with an experiment involving high-speed video and supermarket sausages, with gruesome results.

If you’re looking for more, why not check out our our previous coverage on electromagnetic weaponry?

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Semi-Automatic Rail Gun Is A Laptop Killer

October 14, 2017 by Dan Maloney 37 Comments

It’s huge, it’s unwieldy, and it takes 45 seconds to shoot all three rounds in its magazine. But it’s a legitimate semi-automatic railgun, and it’s pretty awesome.

Yes, it has its limits, but every new technology does, especially totally home-brew builds like this. The aptly named [NSA_listbot] has been putting a lot of work into his railgun, and this is but the most recent product of an iterative design cycle.

The principle is similar to other railguns we’ve featured before, which accelerate projectiles using rapidly pulsed electromagnets. The features list in the video below reads like a spec for a top-secret military project: field-augmented circular bore, 4.5kJ capacitor bank, and a custom Arduino Nano that’s hardened against the huge electromagnetic pulse (EMP) generated by the coils. But the interesting bits are in the mechanical design, which had to depart from standard firearms designs to handle the caseless 6 mm projectiles. The resulting receiver and magazines are entirely 3D printed. Although it packs a wallop, its cyclic rate of fire is painfully slow. We expect that’ll improve as battery and capacitor technology catches up, though.

Want to check out some more railgun builds? We’ve got them in spades — from one with $50,000 worth of caps to a wrist-mounted web-slinger.

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Pulsed Power And Its Applications

January 11, 2017 by Manuel Rodriguez-Achach 43 Comments

Pulsed power is a technology that consists in accumulating energy over some period of time, then releasing it very quickly. Since power equals energy (or work) divided by time, the idea is to emit a constant amount of energy in as short a time as possible. It will only last for a fraction of a second though, but that instantaneous power has very interesting applications. With this technology, power levels of more than 300 terawatts have been obtained. Is this technology for unlimited budgets, or is this in reach of the common hacker?

Consider for example discharging a capacitor. A large 450 V, 3300 uF electrolytic capacitor discharges in about 0.1 seconds (varies a lot depending on capacitor design). Since the energy stored in it is given by 1/2 CV², which gives 334 Joules of energy, the power delivered will be 3340 watts. In fact a popular hacker project is to build large capacitor banks. Once you have the bank, and a way to charge it, you can use it to power very interesting devices such as:

untitled1 — A portable, 1.25 kJ coilgun by [Jason Murray]

Railguns in particular are subject to serious research. You may have read about the navy railgun, capable of reaching a muzzle speed of more than 4,600 mph (around Mach 6), more than any other explosive-powered gun. Power is provided by a 9-megajoule capacitor bank. The capacitors discharge on two conducting rails, generating an electromagnetic field that fires the projectile along the rails. The rail wear due to the tremendous pressures and currents, in the millions of amperes range, is still a problem to be solved.

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24kJ Capacitor Bank

September 20, 2008 by Jason Rollette 42 Comments

The Leyden jar capacitor posted the other day fails to compare to what [FastMHz], one of the members over at the 4HV.org forums, has been busy building, a 24kj capacitor discharge bank. This capacitor bank will be configured for 4500v @ 2400uF and can be charged up slowly using microwave oven transformers. It can then release all its stored energy in under a millisecond through a triggered spark gap. This allows for some pretty big sparks as seen in this video, we are not sure about the laughing in the video maybe the power has gone to his head? Continue reading “24kJ Capacitor Bank” →