Tether

A tether is a thin cable that connects two portions of a spacecraft. Tethers have been flown in space with lengths of as long at 20 km. Much longer tethers have been proposed.

Tethers have possible applications including space propulsion, power, and artificial gravity.

Possibly the simplest and most elegant use of tethers is for space propulsion, using the method of momentum exchange by tethers. This concept has been analyzed, among others, by Tethers Unlimited^[1].

This could be built fairly easily, possibly cheaper than building a mass driver on the Moon.

Cislunar tether propulsion paper in PDF format

It has an advantage over mass driver in that it can be used to soft land on the Moon as well as depart from the Moon. If the energy imparted by the cargo is balanced, the tether would require little if any energy input and minimal propellant usage.