One of the arguments for colonising the Moon is that it contains a lot of material that may be useful back on Earth, such as O helium-3, an isotope of helium that some say could be used as fuel in future nuclear fusion power plants to provide a huge new source of energy. If we are going to colonise the Moon, then we could do with an innovative and low-cost way to send this useful material back to Earth. After all, we don’t want to have to use numerous expendable rockets to continually transport cargo to and from the Moon.
With that in mind, some space enthusiasts have envisioned a railgun of sorts that would fire projectiles from the Moon to Earth. Using magnetic levitation, it would accelerate a payload to the speed required to escape the gravity of the Moon and return to Earth. This idea was used in the 2009 movie Moon, with helium-3 being mined on the Moon and sent to Earth by such a machine, known as a lunar mass driver.