Instead of an explosion of gunpowder, a rail gun uses magnets to accelerate a projectile. That may sound like weak sauce, but rail guns can fire their “bullets” way faster than a regular gun. So that’s why it’s incredibly scary that user NSA_Listbot has managed to 3-D print a DIY “portable” rail gun that he claims can shoot projectiles at up to 560 mph (250 m/sec).
The gun uses six capacitors to pulse 1,800 joules of energy into the projectile. The power comes from a lithium-polymer battery, like you might find in a cellphone or notebook computer, and is stepped up from 12 volts to 1,550 volts through a micro-inverter and then a transformer, a process that gets so hot that NSA_Listbot had to add a heatsink to cool things down again. Charging is regulated by an Arduino controller. Here it is going up against a cantaloupe:
The gun works by first using compressed CO2 to accelerate the projectile up to 100 m/sec, then the electromagnets take over, grabbing the projectile and flinging it out at absurd speeds. Here’s the aftermath:
All of these parts are mounted on a 3-D printed body, and the result is something that stretches the definition of “portable.” The capacitors alone weigh in at nine kilos, or almost 20 pounds. NSA_Listbot has tested the gun with copper plated tungsten, aluminum, and carbon projectiles.
I’m not sure what’s more terrifying: The fact that you can build a high-tech gun with off-the-shelf parts and a 3-D printer, or the face on that cantaloupe.