You’re probably familiar with Newton’s third law of motion: every action has an equal and opposite reaction. This is evident in firearms. Whenever a bullet is propelled forward, the weapon recoils backward. But what about those futuristic energy weapons you see in science fiction? The blasters in Star Wars appear to recoil; the phasers on Star Trek do not. Which is more realistic?
While the kind of energy weapon we see in science fiction is far beyond our current technology, several other Sci-Fi-like weapons do already exist or are in development. Take for example the railgun. Rather than use a chemical explosion like gunpowder or a mechanical force like a spring or hammer to fire a projectile, railguns use high powered magnetic fields to accelerate a metal slug to an enormous speed. By the time that slug exits the barrel of the gun, it’s traveling so fast it can shoot straight through solid concrete walls.
But even though railguns don’t experience the same mechanical recoil as traditional firearms, they do experience recoil of a different kind. Think about what happens when you try to press two refrigerator magnets together. They push against each other. The magnets inside a railgun are exponentially more powerful than the ones on your refrigerator, so the forces at work are much stronger. Also, depending on how the magnets are arranged inside the gun, the magnetic recoil tends to push outward rather than to cause the gun to kickback.
It’s amazing this magnetic recoil doesn’t cause railguns to explode, flinging shrapnel in all directions with that same devastating force that punches holes in concrete walls. According to Tom Boucher, the Navy’s test director for their experimental railguns, despite the extremely sturdy design on the Navy’s railgun prototype “… if we don’t carefully manage [the current in the railgun], it will still come apart. We have huge amounts of forces we’re dealing with here.”
So should phasers and other futuristic energy weapons have recoil? I’d say yes, but not necessarily in the same way as a Colt .45 or an AK-47. Perhaps they have magnetic recoil, like a railgun. Or perhaps, if the weapon uses an energy source beyond our modern science, the recoil manifests itself in some other way that science has yet to understand. But however phasers and blasters and other Sci-Fi weapons are supposed to work, they must still obey Newton’s third law.
Click here for more from Tom Boucher and a demonstration of the U.S. Navy’s railgun prototype on YouTube.
Click here for “Recoil in Electromagnetic Railguns,” a scientific article from the Third Symposium on Electromagnetic Launch Technology.