Is the Impossible "Emdrive" Possible?
Written by Nancy Atkinson
Proposed design for an electromagnetic drive. Credit: SPR Ltd.
A controversial concept called the electromagnetic drive, or Emdrive for short has been called impossible. But one company believes the concept is viable and has worked for several years on building demonstration models. The Emdrive is a reactionless propulsion system that supposedly generates thrust by converting electrical energy via microwaves. If it works it could provide an almost endless supply of thrust for satellites and possibly other spacecraft. But no detectable energy emanates from the device, and most scientists say the Emdrive violates the well-established principle of the conservation of momentum. Satellite Propulsion Research, Ltd. (SPR), the company working on the drive now says researchers from China have confirmed the theory behind the Emdrive, and they should have a trial engine ready to test by the end of this year.
A reactionless drive was first proposed in the 1950's, but came to attention in 2006 when New Scientist published an article about Dr. Roger Shawyer, who founded SPR, and claimed he had constructed a prototype that produced 88 millinewtons of forces while using only 700 watts of power. The idea was met with criticism from nearly all fronts.
The idea of the Emdrive involves forces created by reflecting microwaves between opposite walls of a cavity. If a cavity could be designed which would cause the forces on one side to be greater than the other, thrust could be achieved. The proposed cavity is cone shaped, which supposedly would provide the unequal force design.
In principle, no microwaves or anything else leaves the device, and so it is considered reactionless. But Shawyers website claims that the device is not reactionless, or a perpetual motion machine, because the force is created by a "reaction between the end plates of the waveguide and the Electromagnetic wave propagated within it."
Originally, Shawyer, a British scientist, got funding from the UK, and then from am US company. Now the researchers at China's Northwestern Polytechnical University (NPU) in Xi'an say they have confirmed the Emdrive theory, and have gotten funding to build the device.
Their device is based on Shawyer's theories, and if it works, it would confirm what Shawyer has been claiming all along. The Chinese lead researcher, Professor Yang Juan, previously has worked with microwave plasma thrusters, which has similar engineering principles. A recent article in Wired said he Chinese should be capable of determining whether the thruster really works or whether the apparent forces are caused by experimental errors.
If the Emdrive works, what would it mean for spaceflight? Shawyer says a solar-powered Emdrive could take a manned mission to Mars in 41 days.
Paper by Shawyer on the Emdrive (not peer reviewed)
Opposing paper by Dr. John Costella
Sources: Wired, Emdrive.com, Wiki
Filed under: Satellites, Space Flight
October 10th, 2008 at 2:03 pm
Radiation pressure is at least the propulsion of a solar sail, isn't it?
October 10th, 2008 at 3:24 pm
Microwave propulsion, the "theory" behind the Emdrive, is not a worthwhile idea. Here's why? Roger Shawyer makes a basic mistake in vector addition and doesn't explain it. It's like having a bank statement that doesn't add up.
One assumes the error is in the calculation, and not an improper understanding of money. If the statement is correct then the bank had better have a very good explanation. But the Emdrive uses microwaves so special relativity changes things. Would changing the currency make the bank statement more acceptable? For anyone who believes a simple error in calculation represents a revolutionary new way of understanding the universe, I would like to be your accountant.
October 10th, 2008 at 8:28 pm
For reasons I will not go into here, I had occasion to make a cone shaped cone of brass (not having gold) and lined it with woollen carpet, and inserted another brass cone, and lined that with more carpet, and inserted another brass cane. Yes: I built an orgone-engine! It quivered on the drive-way, and then took off, and it has not been seen since, anywhere by anyone who admits it. Next time I build the body and load, and work out its trajectory before I build the engine. Let that be a warning to you all. [ my joke ]
Entropy: Nothing from nothing; and everything to nothing eventually.
New ideas are good, and great if they are substantial.
October 11th, 2008 at 1:36 am
No detectable emission?
… so the microwaves simply bounced back and forth forever inside, becoming more and more intense as the solar arrays power it up, never being absorbed and re-released as heat?
So the inner surface is a perfect mirror including the microwave emitting device itself?
If you say yes in support of the device, then you must concede there is no thrust because the vector sum of all the bouncing microwaves in the closed device will always be zero.
If you say no to the infinite perpetual internal reflections of the microwaves, in defiance of the device, then at the very least the device emits heat … a detectable emission that contradicts the author.
However If the heat is all coming out the back of the engine then maybe you'll get some thrust in a manner similar to a solar sail … but NOT by the erroneous mechanism the scamming author is promoting.
This scam idea has been around for decades, just waiting for ignorant people in positions of power to fund it. File this crap in the same category as the 'water fueled' car scams.
You would think the guy who runs this blog would see through it. He is a scientist isn't he?
Perhaps I will visit this website less often now, the credibility of this website is damaged.
October 11th, 2008 at 2:07 am
The momentum exchange is between the electromagnetic wave and the engine, which is attached to the spacecraft. As the engine accelerates, momentum is lost by the electromagnetic wave and gained by the spacecraft, thus satisfying the conservation of momentum. In this process, energy is lost within the resonator, thus satisfying the conservation of energy.
October 11th, 2008 at 2:31 am
"As far as I know, Shawyer has never claimed his drive exists as a closed system (and how can it ?) therefore those who prattle on about conservation of momentum rather miss the point that all he states is an empirical effect and then provides a theory of explanation. If his theory is incorrect, but the effect is real, what then ?"
October 11th, 2008 at 2:38 am
Costella is addicted to conspiracy theories.
October 11th, 2008 at 6:32 am
I stick out my right hand and then step up onto it with my left foot. Then I stick out my left hand and step up onto it with my right foot…
October 13th, 2008 at 12:50 pm
Meh, not too far fetched. Is this supposed to be anything like what Heim and Droscher had in mind? I'll save my naysaying till I read more
October 14th, 2008 at 10:52 am
Ok, so ultimately speaking, the device must allow microwave frequency photons to exchange momentum with the waveguide in a preferential direction. So, unlike a poptart in a microwave, the exchange of momentum from photon to solid matter must be, on average, in one direction. I don't follow the math in the author's paper yet because I haven't tried to, I've got my own research to attend to.
As to the issue with the vector addition, any vector can, of course, be expressed as the summation of two or more other vectors. Has anyone bothered to see if the author just skipped the step of telling his readers that he broke down the components of the vector that hits the sloping wall into their x and y components? It seems to me that he's claiming that over time the microwaves are converted from a random distribution of x and y components into being mostly x (the direction of travel) and very little y (which cancel each other out).
In a sense, this concept is the reverse of the flashlight on a train thought experiment. Instead of increasing the frequency of the light shining from the front of the train, the microwaves moving around in the chamber must become red-shifted as the give up their momentum. If, that is, this device actually functions.
October 14th, 2008 at 10:55 am
Whoops, 2nd to last sentence should read:
"In a sense, this concept is the reverse of the flashlight on a train thought experiment. Instead of increasing the frequency of the light shining from the front of the train, the microwaves moving around in the chamber must become red-shifted as they give up their momentum.
October 14th, 2008 at 1:56 pm
Reminds me of the Dean Drive which was featured in Missiles & Rockets magazine back in the 60's.
October 15th, 2008 at 8:51 am
i didint read all the posts so i dont know if anyone already posted this but in the FAQ os EMDRIVE.com states:
Q. Is the thrust produced by the EmDrive a reactionless force?
A. No, the thrust is the result of the reaction between the end plates of the waveguide and the Electromagnetic wave propagated within it.
October 18th, 2008 at 10:33 am
This is a funny discussion! If you lean out of the window too much here … (well, one can sense a lot of group pressure here. So as usual, either be careful what you write or else you are already hardened against being f'ed up!)
Conservation of Momentum and of energy both do not need an advocatus diaboli to speak for them against the mass who shouts "she shall burn" because they cannot be disregarded. They are not negotiable (only gods can break the laws of nature… anyone?)
But on the other hand the scientific method is for sure not fulfilled by the methods which Mr. Costella has chosen to refute Mr. Shawyer.
Look at what Mr. Costella did.
http://www.assassinationscience.com/johncostella/shawyerfraud.pdf
The abstract of his article starts with a prejudice:
"Abstract
It is well known that Roger Shawyer’s ‘electromagnetic relativity drive’ violates the law of con-servation of momentum."
Wow!
In the very beginning Mr. Costella claims that if you do not already share a pre!judice, then shame on you. No, you don't learn anything here if you do not already know beforehand! That is not the way things start if you expect to LEARN something trustfully.
October 18th, 2008 at 11:00 am
@ RL
Don't let the name fool you
Northwestern Polytechnical University is not a polytechnic institute. It is a key government funded research university under direct jurisdiction of ministry of industry and information technology. (restructured from Commission of Science, Technology, and Industry for National Defense)
Professor Yang worked for china's space program.
October 18th, 2008 at 12:21 pm
In his article, Dr. Costella tries to explain "what’s wrong in Shawyer’s paper". He refers to a scetch and concludes:
"Now look back at Shawyer’s Figure 2.4. He has Fs1 and Fs2 pointing perpendicular to the axial direction, not perpendicular to the cone’s walls.
His arrows are wrong.
This is the fundamental blunder that renders Shawyer’s paper meaningless."
But the point is that whatever arrows he skipped in this figure Mr. Swayer claimed that instead "he had constructed a prototype that produced 88 millinewtons of forces while using only 700 watts of power."
So it is rediculous to refer to an imperfect scetch when there is an experimental evidence. But how does Dr. Costella demonstrate that the result of the experiment is wrong? The point is that he is too lazy to proof that Shawyers experiment is of no meaning. He just refers to a missing arrow in a scetch. This is what he writes:
"I started having waking nightmares about what would be needed to disprove him: complicated mathematical solutions of horrendous equations; complex computer simulations of conical waveguides; … I shuddered at what I had, mentally, committed myself to. But just as the computer-ised woman in the train’s roof told me that we were approaching Seaford Station, the penny dropped. It was something that I could have explained to my Year 11 students when I was a still a teacher."
And thus he builds his critics on a figure which is of no meaning for Mr. Shawyers experimental results.
I don't know what is wrong with Mr. Swayer's engine. But I know that Dr. Costella does miss the point.
November 6th, 2008 at 10:34 am
Scientific method (and for that matter, engineering) implies reproducible results.
Mr. Shawyers who built the "Emdrive" releases the design and someone else builds an identical copy and tries to make it work. The new drive either works or it doesn't.