Ever since I was old enough to read science fiction, I've wanted to visit Mars. Even the Moon would be better than nothing. Alas, rocket technology is unlikely to take me there within my lifetime.

The problem is that rockets are a poor tool for the job. Even if their safety record improves, they are inherently limited by the basic concept of reaction mass. Hot gases must blast out of the rear in order to move a space vehicle forward, and this entails carrying a fuel load that is hundreds of times heavier than the payload.

Ever since H. G. Wells imagined a gravity-shielding material in "The First Men in the Moon," space enthusiasts have fantasized about ways to achieve thrust without any need for reaction mass. Unfortunately, it seems impossible.

Or is it?

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