In the Borderlands series, specifically Borderlands 2 and Borderlands: The Pre-Sequel, corporate villain Handsome Jack and the company of Hyperion use a device on their moon base/corporate HQ to launch supplies and killer robots down to the planet of Pandora and its moon, Elpis. But just what is said device?
During the beginning of Borderlands: The Pre-Sequel, you get the luxury of being shot out of the moonshot cannon in an emergency evacuation. Fun! But, in the chamber for the moonshot, there is no visible propulsion device: no explosive charge or rocket to launch it. So what does propel the moonshots? Simply put, the moonshot cannon acts as a railgun.
So, how does a railgun work? By connecting a projectile between two long rods, and running a current through the rods, it's possible to create an induced magnetic field which launches said projectile without the need for a conventional propulsion mechanism.