We’ll explain the history and basic principles of railguns, covering the differences between sci-fi movies and real-life railguns, how the technology has evolved, and explore their current practicality.
A giant, monstrous robot made up of several cars climbs a pyramid. American soldiers at sea in the distance watch and fire a giant laser cannon-like weapon from their ship. Soon after, the monster is hit by the laser and staggers to the ground. You may recognize this scene from the movie Transformers: Revenge of the Fallen. The weapon that looks like a laser cannon in the movie is actually a railgun. If you’ve ever seen a sci-fi movie or game, you’ve probably heard of railguns before, but they’re often portrayed differently in most media. Let’s take a look at how railguns are made and what they actually do.
Railguns have a very long history. In 1920, almost 100 years ago, the American Willeff filed a patent for a railgun. At the time, the idea was only proposed, but never actually used due to technical difficulties. Later, during World War II, the Nazis actually developed a weapon that used a railgun, but the war ended before it could be put into practice. Development of the railgun has continued ever since, and relatively recently, the U.S. military successfully test-fired a railgun, signaling that it will be deployed in the field. As such, railguns have long symbolized a revolutionary advance in military technology.
With such a long history of research, you might be wondering if railguns are based on some crazy theory that’s hard for the average person to understand. Not really. The basic principle of the railgun as envisioned by Willebrand over 100 years ago is so simple that it doesn’t look much different from a modern railgun. Imagine a model that you might have seen in a high school physics textbook: two wires side by side, each with an electric current flowing in opposite directions. What happens if you put a thin rod of iron, which can roll freely, on top of the wires? The bottom line is that the iron rod will roll on the rails of the wires.
This situation can be explained by electromagnetic induction. First, recall Fleming’s right hand rule. The two wires each have a current flowing through them, and the right-hand screw law creates a magnetic field that wraps around each wire. At the center of the two wires, a magnetic field is formed perpendicular to the ground. Since the current flows in opposite directions in the two wires, the magnetic fields of the two wires do not cancel each other out at the center, but act in the same direction and become stronger. In other words, there is a strong magnetic field perpendicular to the ground between the two wires. Now, let’s use the two wires as rails and put a bar on top. There is a voltage difference between the two wires, which causes an electric current to flow along the rod.
Now it’s time to think about the Lorentz force. If the direction of the current and the magnetic field are perpendicular, the wire through which the current flows will experience a force in the direction perpendicular to both the current and the magnetic field, which is the Lorentz force. In the above situation, there is a current flowing through the rod, and the magnetic field from the wires on either side of it is perpendicular to the ground, which is also perpendicular to the rod. Therefore, the rod is forced in a direction perpendicular to both the current and the magnetic field, causing it to roll along the rail. This is the same principle with a railgun. The only difference is that you replace the wire with a very large and strongly energized rail, and instead of a bar, you use a giant metal bullet.
While the principle of the railgun is simple, there were many technical challenges to realize it. The high currents require sophisticated power management techniques to handle, and effectively controlling the heat generated by firing bullets at high speeds was also a major problem. To address these challenges, scientists have been researching new materials such as superconductors and developing various methods to prevent arc discharge. This process involved numerous failures and successes that eventually led to today’s railgun technology.
A decade ago, railguns were considered the stuff of science fiction. Today, they’re so close to reality that the U.S. military is considering deploying them. This doesn’t just mean the development of a new weapon. In fact, the development of the railgun overcame existing technological limitations and used various technologies, such as superconductors and arc protection, which means that advances in science and technology can realize our imagination. With the railgun as a precedent, we look forward to the day when technologies that are currently considered fanciful will become a reality. Science and technology are constantly evolving, and with it, humanity will achieve even more amazing things. The railgun is just the beginning.
