Microwave-Powered Rocket Ascends without Fuel
A scale model is further proof that beamed-energy propulsion works.
Christopher Mims 09/07/2010
- 8 Comments
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Early this year, scientists in Japan successfully "launched" a tiny metal rocket using an unusual source of thrust - microwaves. The test was the latest a proof of principle for a kind of propulsion that has never been the beneficiary of the levels of investment poured into traditional chemical rockets, but which its proponents say could some day be a superior way to get spacecraft into orbit.
Sending rockets into space using a combustible mixture of on-board fuel isn't an optimal solution to the problem of escaping Earth's deep gravity well. Not only is it dangerous to strap humans and satellites on top of giant bombs, it's also incredibly wasteful: 90% of the weight of a rocket sitting on the launch pad is fuel.
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.
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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.
Every few years, however, someone reminds the world that it's at least possible to get a rocket off the ground with little or no fuel. 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.
Here's a never-before-seen video of the launch:
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.
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rsanchez1
213 Comments
nice demo
The video was a nice proof-of-concept of using microwaves to propel a craft upward. I wonder how well it scales. It heats the air on the bottom of that little thing to 10,000 degrees. If scaled to a full-size craft, like a space shuttle-sized craft, what effect would it have on the surrounding atmosphere? What effect would transmission of such amounts of energy, and having it concentrated on the small area of a shuttle flying hundreds of miles into the sky, have on the lower atmosphere?
Moreover, that little thing seemed to take off almost instantly. Small rockets do that as well, but how quickly would a full-sized craft take off? If it quickly accelerates, it might not be good for humans or delicate cargo (such as space telescopes).
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doanwon
76 Comments
Re: nice demo
Lots of work is needed for true scaled functionality. I would think that variable power or multiple thrust pockets could be fired incrementally. Then they would have to design the thruster so that airflow can quickly fill the heated void. They can even eject on-board air into the thruster pocket once the atmosphere can no longer deliver the thrust. The launch of a rocket or shuttle is basically a controlled explosion so this should work in the same way. I am probably blowing smoke so hope to hear from a real rocket scientist.
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