[tt] Chinese Say They're Building 'Impossible' Space Drive | Danger Room from Wired.com

[Brian Atkins]

http://blog.wired.com/defense/2008/09/chinese-buildin.html

Chinese researchers claim they've confirmed the theory behind an "impossible" 
space drive, and are proceeding to build a demonstration version. If they're 
right, this might transform the economics of satellites, open up new 
possibilities for space exploration –- and give the Chinese a decisive military 
advantage in space.

To say that the "Emdrive" (short for "electromagnetic drive") concept is 
controversial would be an understatement. According to Roger Shawyer, the 
British scientist who developed the concept, the drive converts electrical 
energy into thrust via microwaves, without violating any laws of physics. Many 
researchers believe otherwise. An article about the Emdrive in New Scientist 
magazine drew a massive volley of criticism. Scientists not only argued that 
Shawyer's work was blatantly impossible, and that his reasoning was flawed. They 
also said the article should never have been published.

"It is well known that Roger Shawyer's 'electromagnetic relativity drive' 
violates the law of conservation of momentum, making it simply the latest in a 
long line of 'perpetuum mobiles' that have been proposed and disproved for 
centuries," wrote John Costella, an Australian physicist. "His analysis is 
rubbish and his 'drive' impossible."

Shawyer stands by his theoretical work. His company, Satellite Propulsion 
Research (SPR), has constructed demonstration engines, which he says produce 
thrust using a tapering resonant cavity filled with microwaves. He is adamant 
that this is not a perpetual motion machine, and does not violate the law of 
conservation of momentum because different reference frames apply to the drive 
and the waves within it. Shawyer's big challenge, he says, has been getting 
people who will actually look into his claims rather than simply dismissing them.

Such extravagant claims are usually associated with self-taught, backyard 
inventors claiming Einstein got it all wrong. But Shawyer is a scientist who has 
worked with radar and communication systems and was a program manager at 
European space company EADS Astrium; his work rests entirely on Einstein being 
right. The thrust is the result of a relativistic effect and would not occur 
under simple Newtonian physics. Many have dismissed his work out of hand, and 
British government funding has ceased. He has had some interest from both the 
United States and China. Now the Chinese connection with the Northwestern 
Polytechnical University (NPU) in Xi'an seems to have paid off.

"NPU started their research program in June 2007, under the supervision of 
Professor Yang Juan. They have independently developed a mathematical simulation 
which shows unequivocally that a net force can be produced from a simple 
resonant tapered cavity," Shawyer tells Danger Room. "The thrust levels 
predicted by this simulation are similar to those resulting from the SPR design 
software, and the SPR test results."

What's more, Shawyer says, NPU is "currently manufacturing" a "thruster" based 
on this theoretical work.

"I could confirm that our mathematical simulation gives the results Dr. Roger 
Shawyer told you. Now we are submitting our result to a journal. It is now under 
the consideration of the editor," Professor Yang adds. "We also developed a 
tapered cavity and are preparing an experiment which will be completed at the 
end of this year."

Needless to say, independent confirmation is a big deal -- though many will want 
to see it published in a peer-reviewed journal. Even when it is, I doubt the 
controversy will subside. Prof. Yang has plenty of experience in this type of 
area, having previously done work on microwave plasma thrusters, which use a 
resonant cavity to accelerate a plasma jet for propulsion. While the theory 
behind the Emdrive is very different, the engineering principles of building the 
hardware are similar. The Chinese should be capable of determining whether the 
thruster really works or whether the apparent forces are caused by experimental 
errors.

The thrust produced is small, but significant. Shawyer compares a C-Band Emdrive 
with the existing NSTAR ion thruster used by NASA. The Emdrive produces 85 mN of 
thrust compared to 92 for the NSTAR (that's about one-third of an ounce), but 
the Emdrive only consumes a quarter of the amount of power and weighs less than 
7 kilos, compared to over 30 kilos. The biggest difference is in propellant: 
NSTAR uses 10 grams per hour; the Emdrive uses none. As long as it has an 
electricity supply, the Emdrive will keep going.

The possibilities are phenomenal: Instead of going out of service when they run 
out of fuel, satellites would have greatly extended endurance and be able to 
move around at will. (We wouldn't have to shoot them down because of the risk 
from toxic fuel either.) Deep space probes could go further, faster –- and stop 
when they arrive. Shawyer calculates that a solar-powered Emdrive could take a 
manned mission to Mars in 41 days. Provided it works, of course.

What will China do with the technology? It may be relevant that professor Yang 
is not unknown in military circles, having published a paper called "Plasma 
Attack Against Low-Orbit Spy Satellites."

Meanwhile, what about the American interest? Shawyer told me that "the flight 
thruster program is on hold for the present. [O]nce the U.K. government had 
provided an export license for a U.S. military application, the major U.S. 
aerospace company we had been dealing with stopped talking to us. "

The company may have decided that the Emdrive could not work. If they're wrong, 
China has at least a year's head start in a technology that will dominate space 
and make previous satellites as obsolete as sailing ships in the age of steam.

-- 
Brian Atkins
Singularity Institute for Artificial Intelligence
http://www.singinst.org/