Mad About Science: Gauss rifle

By Brenden Bobby
Reader Columnist

Lifelong video game fans are no strangers to the gauss rifle. What many people may not realize is that these exist in the real world, and you can actually build them from the comfort of your own home with a small collection of household items, a handful of magnets and some ball bearings.

In video games, gauss rifles are extremely powerful weapons that use focused magnetism to blast enemies into gooey fragments. In the real world, we can explore the basis of how a weapon like this might function, and how we can apply the principles behind it into something more beneficial to mankind than liquefying extraterrestrials.

Let’s start with building our own gauss rifle and explaining why it works later.

A Gauss rifle. Courtesy photo.

Before we start, I need to state that you should treat a gauss rifle as though it were an actual rifle. Never point it at a living thing, especially yourself, your family or your pets. Be mindful of what’s in front of you, where the projectile will travel and what it could impact. Always wear safety goggles.

To build your own gauss gun, you will need a grooved piece of wood (rulers with a groove down the center are the best for this) at least four magnets and nine metal ball bearings, as well as some tape and a receptacle for collecting projectiles.

Tape your magnets to the ruler in equidistant positions — two inches apart works well. Now place two ball bearings to the direct right of each magnet inside the groove of your ruler. You should have one ball bearing remaining, which you will now set to the far left of the ruler. The ball bearing should move toward the magnet, but if it doesn’t you can give it a little push. Once the ball bearing strikes the magnet, the reaction happens too quickly for your eyes to see, but the ball bearings will all have shifted positions, while the one to the far right has fired off toward your collection receptacle.

You might be left wondering what happened. Buckle up, folks, because I’m about to drop the dreaded four letter word: math.

The gauss rifle is an experiment in the transference of kinetic energy, which can be summed up by the equation of Ke=1/2mv2. That means kinetic energy is equal to one-half of an object’s mass multiplied by its velocity, squared. As energy cannot be created or destroyed, how did the slow-rolling ball bearing produce so much kinetic energy?

The process was aided by the magnets. The first ball striking the magnet was pulled toward the magnet, and upon impact transferred all of its energy to the magnet, which transferred that energy to the next ball bearing, which transferred to the ball bearing after that, which led to the cycle repeating until there were no more magnets present. 

Each magnet effectively acted as an accelerator for the second ball in the chain, increasing velocity to produce a scaling effect.

If you were to run this across a very long track, you would eventually see one of these ball bearings produce so much force that it would shatter a magnet in the chain upon impact.

This might seem like a completely frivolous experiment that has no real-world applications, but you’d be surprised. Theoretically, we could build a very large gauss rifle several miles long that arcs upward to fling objects into orbit. We are presented with the problem of air on Earth, which creates friction as objects push through it. At high speeds, the amount of energy being converted into heat by friction is staggering — you see this happen to meteorites entering Earth’s atmosphere or from a spacecraft during re-entry. 

(Bonus fact: a spacecraft uses air identically to how your car uses brakes to slow down, by converting friction into heat energy.)

In an environment without air, there would be no friction to sear our payload or slow it down. That same environment would also have a considerably lower gravitational pull than Earth, meaning a payload launched from its surface would be able to travel farther with less fuel required.

The nearest environment that fits that criteria would be the moon, 238,900 miles away. A magnetic sling could theoretically reduce the need for fuel on an undeveloped body like the moon, if humans were to mine it for resources. It’s possible that this could be applied to the asteroid belt as well.

The mechanics behind a magnetic launcher like this would be a little bit different than a gauss rifle. A railgun is a rifled tube with two metal rails alongside the firing chamber and an armature at the back upon which ammunition is loaded. When an electrical charge is introduced to the rails, they create a powerful electromagnetic field. The more “juice” you give the rails, the more powerful the field and the faster the armature will fling that projectile from the barrel. The U.S. Army tested a railgun like this and fired an object at mach six, or 4,567 miles per hour — six times the speed of sound. A .30-06 round from a hunting rifle travels at around 1,900 mph, less than half the speed from the railgun.

The escape velocity of the moon is 5,300 mph, easily achievable in an area where air won’t slow down the payload.

It’s believed that railguns would be considerably safer to transport and operate than traditional munitions or fuel sources, as you don’t have to worry about them exploding when there’s a change in atmospheric pressure or temperature — or if Private Pyle jostles the crate the wrong way. The potential for transporting small payloads through space with magnetic slings could be revolutionary.

Stay curious, 7B.