Traditional chemical rockets are 90 percent fuel by weight:
In the beginning of the 20th century, it occurred to Russian rocket scientist Konstantin Tsiolkovsky that there was another way: by keeping the energy source on the ground and beaming the required power to a rocket, it could be launched with very little fuel on board.
With the invention of the maser, or microwave laser, scientists were granted a tool to realize Tsiolkovsky’s dream. So in the 1970′s they began to model just what it would take. Some were optimistic about its potential to decrease the cost of going to orbit by orders of magnitude, but the bottom line is that, for a lack of funding, the technology never took off.
The Japanese recently demonstrated (another) prototype microwave-powered rocket:
The latest demonstration used a Gyrotron — essentially a maser — at the Naka Fusion Institute of the Japan Atomic Energy Agency. (This super high-powered microwave beam emitter was originally developed as part of Japan’s contribution to ITER, the international effort to create a workable fusion reactor.)
Using this beam, the scientists were able to send pulses of microwave energy into the bottom of their hollow 126 gram rocket model, heating the air within to 10,000 degrees Celsius and resulting in its rapid expansion. The result is a little boom, “like thunder,” they report.
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The rocket traveled 1.2 meters into the air — the world record for such a craft is 72 meters and 12.7 seconds of flight, accomplished in 2001.
(Hat tip to Nyrath.)