Propulsion system works -- Nobody knows why?
Posted by robgambrill 10 years, 9 months ago to Science
Well it turns out the Emdrive does produce thrust. The problem is that the engine appears to violate the principle of conservation of momentum.
So, it has been independently shown to work, but nobody knows exactly how it works. Some unknown quantum effect perhaps?
So, it has been independently shown to work, but nobody knows exactly how it works. Some unknown quantum effect perhaps?
Previous comments... You are currently on page 2.
Let me see if I understand what you guys are saying about the source of the hype.
When the NASA guy says
"... is producing a force that is not attributable to any classical electromagnetic phenomenon"
he probably would have been more correct to say something like
"..is producing a force who's mechanism is not clearly understood".
Maybe the guy is just trying to get his research grant renewed?
Still the idea of a propulsion system that does not expel mass sounds pretty cool. If you don't have to carry propellent and it does not require sunlight, it could be a way to send probes into interstellar space.
EmDrive (also Relativity Drive) is a spacecraft propulsion system proposed by British aerospace engineer Roger J. Shawyer, who develops prototypes at Satellite Propulsion Research Ltd (SPR),[1] the company he created for that purpose in 2000.[2] New Scientist ran a cover story on EmDrive in its 8 September 2006 issue.[3] The device uses a magnetron producing microwaves directed inside a specially shaped, fully enclosed tapering high Q resonant cavity whose area is greater at one end, upon which radiation pressure would act differently due to a relativistic effect caused by the action of group velocity in different frames of reference. The inventor claims that the device generates a thrust even though no detectable energy leaves the device. If proven to work as claimed, the EmDrive could allow the design of spacecraft engines that would be electrically powered and would require no reaction mass. Such an engine would be a breakthrough in airflight and spaceflight.[4][5][6][7][8][9]
The device and its mode of operation are highly controversial. As of 2014, there are still arguments about whether the EmDrive is a genuinely new propulsion method, a misinterpretation of spurious effects mixed with mathematical errors, or a scam. The proposed theory immediately received virulent criticism because it seems to violate basic Newtonian laws of physics, notably conservation of momentum,[10][11] though the inventor insists on the contrary.[12] Chinese researchers from the Northwestern Polytechnic University (NWPU) in Xi'an first repeated the experiment in 2010,[7][13][14][15] then NASA in the Eagleworks Laboratories at the Johnson Space Center in 2014.[9][16]
Should the EmDrive produce a real thrust, various conjectures have been made to explain the underlying physics. Shawyer claims the thrust would be caused by radiation pressure imbalance due to group velocities of electromagnetic waves within the framework of special relativity. Dr. Yang from NWPU predicts a resulting net force using classical electromagnetism.[15] An alternative theory has been proposed in 2013 by Argentine physicist Fernando Minotti from CONICET, who explains the alleged forces on asymmetric electromagnetic resonant cavities by a particular class of scalar-tensor theory of the Brans–Dicke type.[17] Dr. Harold G. "Sonny" White, who investigates field propulsion at Eagleworks, NASA's Advanced Propulsion Physics Laboratory, notes that such resonant cavities may operate by creating a virtual plasma toroid that would realize net thrust using magnetohydrodynamics upon quantum vacuum fluctuations.[18] The named quantum vacuum based theories, however, can predict maximal efficiency of 3.33 nN/W, on the order of a millionth as much as EmDrive proponents claim.[citation needed]
"Impulse power only! Aye, capt'n!"
Jan
I agree completely. The force is "not particularly strong" b/c c^2 is not particularly small. You have to have some source of E. So the rocket equation is still in effect, contrary to what the article implies.
It is the same principle as the laser, which itself began as an o-maser (optical maser) from the microwave amplification by stimulated emission of radiation. (Their theory paper here: http://www.emdrive.com/theorypaper9-4.pd... )
As I said, this is interesting and has potential. What I found "baloney" was the hype from Mashable. "EmDrive Is an Engine That Breaks the Laws of Physics .... since it violates the law of the conservation of momentum. ..."
The NASA paper was also interesting in that it only underscored the initial claim that the engine works with the wavefronts at relativistic velocities.
"Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion
device, is producing a force that is not attributable to any classical electromagnetic phenomenon and
therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma. Future test
plans include independent verification and validation at other test facilities. -- http://ntrs.nasa.gov/archive/nasa/casi.n...
"... not attributable to classical ... and therefore ... potentially ... quantum ...." I do note that the NASA test also produced an effect on the null test bed. Thus, they called it an "anomaly."