EmDrive

[MrNlul77]

http://www.ibtimes.co.uk/emdrive-roger-shawyer-paper-describing-space-propulsion-uavs-finally-passes-peer-review-1513223

http://emdrive.com

[AncapFTW]

The first time I saw this device I thought it was interesting.  Unfortunately, it needs huge amounts of energy to create decent amounts of thrust.  In deep space with solar panels, it's not that big of a deal, but one of the links talked about using it for an SSTO ship.  I think you would need beamed power to make that work.

[Guest Gee]

?

[MrNlul77]

Its interesting as it evidently produces thrust, but as to why/how, the scientific community is still debating/experimenting. In understanding how it is producing thrust, there is talk of rewriting the known laws of the universe.

[Guest Gee]

No.

 

What he is proposing is a violation of the conservation of momentum and so can be disimsed out of hand.

 

Incidently modern physics and the product of the scientific method will never and can never be rewritten, it can only ever be extended and or simplified. This is because there are only two ways of something being accepted as superior;

 

1. It must explain everything the current theory explains + 1 more thing (extended)

 

or

 

2. It explains everything the current theory explains but it is simpler (simplfied as per the principle or parisomony)

 

So it is not shocking to see that his theory has not been independently experimentally verified, nor will it be, because what this theory requires is the invalidation of fundimentals which have been validated ad nausium.

[AncapFTW]

No.

 

What he is proposing is a violation of the conservation of momentum and so can be disimsed out of hand.

 

Incidently modern physics and the product of the scientific method will never and can never be rewritten, it can only ever be extended and or simplified. This is because there are only two ways of something being accepted as superior;

 

1. It must explain everything the current theory explains + 1 more thing (extended)

 

or

 

2. It explains everything the current theory explains but it is simpler (simplfied as per the principle or parisomony)

 

So it is not shocking to see that his theory has not been independently experimentally verified, nor will it be, because what this theory requires is the invalidation of fundimentals which have been validated ad nausium.

New physic discoveries often appear to violate established principles.  At one point the conservation of matter and energy didn't include that matter and energy could be converted into one another because they didn't know that they could.  Relativity appeared to violate the laws of Newtonian physics at significant portions of C.

 

As I understand it, this drive isn't really any more a violation of the laws of physics than a solar sail.  Maybe it only works because it is interacting with either the Earth's atmosphere or its magnetic field, though the way they describe it is like bouncing a ball against something (say a soccer net) to impart momentum into it.  It would be an efficient Photon drive.

[Guest Gee]

Right, relativistic physics extends Newtonian, it would be Newtonian + at least one more and the equations of relativistic physics are prefectly valid for low energies (it explains all pre existant theories, which is to say it explains all known phonenonma + at least one more).

 

The issue isn't the validity of radiation pressure, which would be how solar sails work (incidently solar sails are inpractical because the intensity of radiation and so the pressure varies with the square of the distance from the radiation source, the sun). The issue is that his design violates the conservation of momentum.

 

So what the author argues is that the force produced by the radiation pressure is an external force (this is why he aruges that the system is an open system, which it is not).

 

The philosophical equivilent would be the preformative contridiction, the content of his statement (his em drive theory) contridicts the presupisitions required to assert his statment (the conservation of momentum).

 

*edit

 

Its like this, the author has designed a trapezoid contain in which he he bouncing around a bunch of light particles, no worries.

Now when the light hits the sides of the trapezoid it is reflected and imparts the a force upon the sides of the trapezoid equil to the change in momentium of the light particle, this is the radiation pressure, no worries either.

The issue is that author is claiming that if he uses waveguides (just a peice of kit to guide a wave) he can set up his trapezoid such that there is more momentum imparted upon the base of the trapezoid than the top, or,

 

a light particle hits the base and has a change of momentum dM_b creating a force on the base F_b

the particle changes direction and travels through the waveguide before hitting the top and being reflected with a change in momentum dM_t creating a force F_t

 

now the author claims that due to the set up, as a direct result of the waveguides, the change in momentum on the bottom is greater than the change in momemtum in the top, dM_b > dM_t thus the force on the bottom is greater than the force on the top F_b > F_t and a net force in the direction of the base has been produced, the effect of which is a reactionary force in the opposite direction, equil in magniture and coliniear upon the system resulting in a thurst.

 

cool.

 

but momentum is a conserved quantitiy and it is a vector quantity meaning the ammount of momentum is conserved in the direction of the momentum so where did the momentum (the difference in the change in momentum in the bottom and the top) go?

 

this is when the author starts invoking relativity and making comparisons to laser ring gyroscopes because all known physics and the physics upon which his theory is indeed predicated requires conservation of momentum BUT conservation of momentum means there can be no differential in momentum upon the top and bottom thus no force and no thurst.

 

Now if the author was to say....... hey, check it, here is a prediction that requires that momentum is no longer conserved that would be cool but he would be laughed out the building.

If he said he could show that momentum was not a conserved quantity then that would be ground breaking paradime shifting world changingly cool, but it would fail because he would be wrong.

 

What the author has done, is created a theory that requires the invalidation of the conservation of momentum with no refrence to such fact and tried to obfuscate this by invoking relativity and this is why no one is taking him seriously, his results will never be independently verifeid (because they are unphysical) and the only journal that will publish him will be click bate publishing a very heavily edited peice.

[MrNlul77]

Right, relativistic physics extends Newtonian, it would be Newtonian + at least one more and the equations of relativistic physics are prefectly valid for low energies (it explains all pre existant theories, which is to say it explains all known phonenonma + at least one more).

 

The issue isn't the validity of radiation pressure, which would be how solar sails work (incidently solar sails are inpractical because the intensity of radiation and so the pressure varies with the square of the distance from the radiation source, the sun). The issue is that his design violates the conservation of momentum.

 

So what the author argues is that the force produced by the radiation pressure is an external force (this is why he aruges that the system is an open system, which it is not).

 

The philosophical equivilent would be the preformative contridiction, the content of his statement (his em drive theory) contridicts the presupisitions required to assert his statment (the conservation of momentum).

 

*edit

 

Its like this, the author has designed a trapezoid contain in which he he bouncing around a bunch of light particles, no worries.

Now when the light hits the sides of the trapezoid it is reflected and imparts the a force upon the sides of the trapezoid equil to the change in momentium of the light particle, this is the radiation pressure, no worries either.

The issue is that author is claiming that if he uses waveguides (just a peice of kit to guide a wave) he can set up his trapezoid such that there is more momentum imparted upon the base of the trapezoid than the top, or,

 

a light particle hits the base and has a change of momentum dM_b creating a force on the base F_b

the particle changes direction and travels through the waveguide before hitting the top and being reflected with a change in momentum dM_t creating a force F_t

 

now the author claims that due to the set up, as a direct result of the waveguides, the change in momentum on the bottom is greater than the change in momemtum in the top, dM_b > dM_t thus the force on the bottom is greater than the force on the top F_b > F_t and a net force in the direction of the base has been produced, the effect of which is a reactionary force in the opposite direction, equil in magniture and coliniear upon the system resulting in a thurst.

 

cool.

 

but momentum is a conserved quantitiy and it is a vector quantity meaning the ammount of momentum is conserved in the direction of the momentum so where did the momentum (the difference in the change in momentum in the bottom and the top) go?

 

this is when the author starts invoking relativity and making comparisons to laser ring gyroscopes because all known physics and the physics upon which his theory is indeed predicated requires conservation of momentum BUT conservation of momentum means there can be no differential in momentum upon the top and bottom thus no force and no thurst.

 

Now if the author was to say....... hey, check it, here is a prediction that requires that momentum is no longer conserved that would be cool but he would be laughed out the building.

If he said he could show that momentum was not a conserved quantity then that would be ground breaking paradime shifting world changingly cool, but it would fail because he would be wrong.

 

What the author has done, is created a theory that requires the invalidation of the conservation of momentum with no refrence to such fact and tried to obfuscate this by invoking relativity and this is why no one is taking him seriously, his results will never be independently verifeid (because they are unphysical) and the only journal that will publish him will be click bate publishing a very heavily edited peice.

From what I read, the EMDrive uses microwaves. Also people are taking the findings seriously as it does raise questions about the the known laws of the universe, Ive not given it much thought for a while so can't remember the source, I don't just make up random statements. The link explains more about the EMDrive

 

http://www.sciencedirect.com/science/article/pii/S0094576515002726