Proposed design for an electromagnetic drive.  Credit: SPR Ltd.

Is the Impossible “Emdrive” Possible?

Article Updated: 26 Apr , 2016

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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


Sort by:   newest | oldest | most voted
Chuck R.
Guest
Chuck R.
October 9, 2008 6:56 PM

Freakin’ sweeeeeet.

The Occupant
Member
The Occupant
October 9, 2008 6:56 PM

Is it real? I have my doubts. But if one can prove it works, and show a working model, then it would certainly be a breakthrough, to put it mildly.
If they can get it working that is.

leafguy
Member
October 9, 2008 7:03 PM

A propellantless source of thrust would be very good indeed. My questions are…for longer space flights (where solar sails don’t apply), how will this technology fair with other sources of power. Given the success of the ion engine, where do costs and comparisons stack up?

Can someone explain to me by what they mean of endless thrust…are we talking acceleration, or maintaining a constant speed?

Mars Man
Guest
Mars Man
October 9, 2008 7:22 PM

If we have anything to say about it, humans will have to walk to Mars first….

GekkoNZ
Member
October 9, 2008 7:56 PM

@Steve: They are meaning acceleration when talking about endless thrust, as in a vacuum no thrust is required to maintain a constant speed due to lack of friction.

pro
Guest
pro
October 9, 2008 8:25 PM

This sounds like an April’s fool joke.
Why they do not open one end of the chamber and let the microwaves be radiated (this will then behave as a classical horn antenna)? This will certainly produce the thrust (VERY small, but it will be there for sure)

Micah Sittig
Member
October 9, 2008 9:09 PM

It’s hard to believe this is getting coverage on Universe Today.

Astrofiend
Member
Astrofiend
October 9, 2008 10:20 PM

Highly dubious. I cannot possibly see how this would work through the mechanism they are describing, unless I’m misunderstanding some part of the concept. For the moment, I’m sticking with the tried and true physics of conservation of momentum in a closed system, as opposed to the claims of some small, unknown company.

alan
Guest
alan
October 9, 2008 10:47 PM

Instead of microwaves, use flashlights! Tie a bunch of flashlights around your ship and wait a couple hundred years and away you go. DOH!

Brian
Guest
Brian
October 9, 2008 11:27 PM

I am frankly shocked and saddened that this crackpot’s idea got onto the Universe Today.

Read the refutation. It explains exactly what’s wrong.

The “emdrive” is logically equivalent to a closed box with balls bouncing around inside it. No matter how funny-shaped the box is, you can’t get net momentum out of such a thing.

kbutler
Member
kbutler
October 10, 2008 6:40 AM

“# GekkoNZ Says:
October 9th, 2008 at 7:56 pm
@Steve: They are meaning acceleration when talking about endless thrust, as in a vacuum no thrust is required to maintain a constant speed due to lack of friction.”
Yeah, Yeah, pure newton, BUT even in a vacumn area such as our solar system I would think that particle friction, solar wind, magnetic fields will affect the velocity of an object.

btw
Guest
btw
October 9, 2008 11:41 PM

I want to believe…….

That flashlight idea could be fashioned here in the US. That’s one piece of hardware the US has down pat. We buy them from China.

quantum_flux
Member
October 10, 2008 12:12 AM

Of course this idea won’t work, there are many possible resonant modes in such a superconducting cavity. Quantum Uncertainty Principle would have it that the pressures will be equivalent throughout the cavity via modal diffraction effects, ergo no unbalanced forces.

Sean Ellis
Guest
October 10, 2008 1:16 AM

If I were a betting man, I would be putting money on the theories. I’m *very* skeptical about this, but the proof of the pudding, as always, is in the eating. If they demonstrate it working, then we’ll have to work to change the theories, and that will be exciting.

InvaderXan
Member
October 10, 2008 8:40 AM

I’m going out on a limb here, because I really don’t know all that much about theoretical physics, but…

Would a device like this work on similar principles to the Casimir effect (ie, changing the vacuum expectation value on one side of the device and therefore causing thrust)?

Or is it something totally different, and I’m just mixing up my physical effects again? smile

rayceeya
Guest
rayceeya
October 10, 2008 2:48 AM

I call it bunk. There’s no way of creating momentum from nothing. This goes into the same box as cold fusion and zero point energy machines.

It’s almost as ridiculous as the water powered car.

Fenring
Guest
Fenring
October 10, 2008 3:57 AM

Completely agree with Costella’s assessment of Shawyers paper. At first I was intrigued by the idea that some relativistic effect takes place here, but something was bugging me from the very beggining of the paper. It soon dawned on me that the forces, that tapered walls experience, are going to cancel out any difference between the forces that opposing plates feel. Shawley’s paper somehow misses that fact. Costella’s rebuttal confirmed my suspicions.

If this contraption actually works it is not the way Shawley describes it and I doubt it works at all.

Kevin F.
Member
October 10, 2008 4:51 AM

I hope it works, and doesn’t not even get tested and fade into obscurity like so many science stories like this.

Chris Coles
Guest
October 10, 2008 4:51 AM

All you naysayers are going to have to eat humble pie. The underlying science, (not specifically for this device), is about to be published and it will change almost everything you know.

This device works and the full understanding why is about to be revealed.

RL
Member
RL
October 10, 2008 6:06 AM

I don’t know much about China’s Northwestern Polytechnical University, but are they a credible university that has done this kind of research in the past? Since they have claimed to have proven out the theory then the evidence should prove or disprove the claim.

To borrow and twist a saying from ESPN, “That’s why they test the theories.”

And why research is peer reviewed (eventually).

And, Thank You, Universe Today. This is an interesting story I know something about even if the theory turns out to be wrong.

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