By the time Neil Armstrong walked on the moon in July 1969, two rocket scientists--Gary Hudson, a college dropout, and George Mueller, perhaps the most respected engineer of his generation--already knew that something radical had to be done about the way we get ourselves into space.
The problem is a mean trick of physics called the rocket equation. Every rocket engineer learns about the rocket equation—first to love it, then to hate it, eventually to accept it. The equation tells you how much fuel your rocket needs to pry itself from the claws of gravity. The premise is deceptively simple: the heavier the rocket or its payload, the more fuel it takes to reach orbit. But fuel is heavy; so when you plug the weight of the fuel into the rocket equation, you find that you have to add even more fuel. Adding fuel means building a bigger tank, which ...
