electric energy, by eliminating the need to launch rocket fuel. Further development awaits the day when the space launch market off-Earth is large enough to justify the cost. The idea for the mass driver may have come from the 1966 Robert A. Heinlein book The Moon Is a Harsh Mistress. Heinlein referred to a similar device as an "induction catapult". References Image: pictured (L to R) are Kevin Fine, Jonah Garbus, G.K. O'Neill, Henry Kolm, and Eric Drexler. Vehicles introduced in 1977 Space colonization Space launch vehicles of the United States