Mass Driver 1
Constructed in 1976 and 1977, Mass Driver 1 was an early demonstration of the concept of the mass driver, a form of electromagnetic launcher, which in principle could also be configured as a rocket motor, using asteroidal materials for reaction mass and energized by solar or other electric power. As originally envisioned, the mass driver was intended to launch payloads from a lunar base to L5, the fifth Lagrange point in which a stable orbit can be maintained.