4 ms·

This doesn't have to violate conservation of momentum to work. We don't understand how it works yet, which precludes us from saying that it violates our curren

by tonyhb 11y ago

This doesn't have to violate conservation of momentum to work. We don't understand how it works yet, which precludes us from saying that it violates our current understanding of physics. I'm no physicist but this guy[1] is, and his paper — which is based off of research with evidence backing it up in the 1970's — suggests that the EmDrive creates propulsion from Unruh radiation[2]. [1]http://physicsfromtheedge.blogspot.co.uk/2015/04/light-in-box-emdrive.html http://physicsfromtheedge.blogspot.co.uk/2015/04/light-in-bo... [2]http://www.ptep-online.com/index_files/2015/PP-40-15.PDF http://www.ptep-online.com/index_files/2015/PP-40-15.PDF

gus_massa 11y ago
If this is consistent with quantum mechanics, this must emit some kind of particles, the main candidates are photons (and far less probable gravitons, but some alternatives / variations claim to use gravity). (I'm not sure about Unruh radiation, but the nice thing about radiation is that when you see it far enough, it doesn't depend on the details of the source, it's simple a bunch of photons. (Well, the color of the photon depends on the details of the source, but they are undistinguishable from other photons.)) If this is consistent with special relativity, and the particles are mass less, then the Force/Power ratio is at most 1/c, that is 0.0033 uN/W = 0.0033 mN/KW. If the particles are not mass less, and you just create them at the moment to emit them, the ratio is even smaller, much smaller. If the particles are not mass less, and just accelerate them from a reservoir, the ratio can be much bigger, but now you have a standard rocket, not a fuel-less rocket. Someone compiled here a list of experiments, with the Force/Power ratio: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1302455#msg1302455 http://forum.nasaspaceflight.com/index.php?topic=36313.msg13... They vary from 3x to 200000x the theoretical maximum if we assume that this doesn't break the conservation of momentum, special relativity and quantum mechanics. (Perhaps it's not necessary to use quantum mechanics, because the classical electromagnetic waves have the same Force/Power ratio, because they are actually a good approximation of the quantum electromagnetic waves. But the photons picture makes all clearer.)
pdonis 11y ago
> the EmDrive creates propulsion from Unruh radiation This would just be a standard photon rocket--the cavity would eject photons out one end and move in the other direction. AFAIK all the EmDrive experimenters are claiming that no radiation is coming out of the cavity.

by tonyhb 11y ago

gus_massa 11y ago

If this is consistent with quantum mechanics, this must emit some kind of particles, the main candidates are photons (and far less probable gravitons, but some alternatives / variations claim to use gravity). (I'm not sure about Unruh radiation, but the nice thing about radiation is that when you see it far enough, it doesn't depend on the details of the source, it's simple a bunch of photons. (Well, the color of the photon depends on the details of the source, but they are undistinguishable from other photons.)) If this is consistent with special relativity, and the particles are mass less, then the Force/Power ratio is at most 1/c, that is 0.0033 uN/W = 0.0033 mN/KW. If the particles are not mass less, and you just create them at the moment to emit them, the ratio is even smaller, much smaller. If the particles are not mass less, and just accelerate them from a reservoir, the ratio can be much bigger, but now you have a standard rocket, not a fuel-less rocket. Someone compiled here a list of experiments, with the Force/Power ratio: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1302455#msg1302455 http://forum.nasaspaceflight.com/index.php?topic=36313.msg13... They vary from 3x to 200000x the theoretical maximum if we assume that this doesn't break the conservation of momentum, special relativity and quantum mechanics. (Perhaps it's not necessary to use quantum mechanics, because the classical electromagnetic waves have the same Force/Power ratio, because they are actually a good approximation of the quantum electromagnetic waves. But the photons picture makes all clearer.)

pdonis 11y ago

> the EmDrive creates propulsion from Unruh radiation This would just be a standard photon rocket--the cavity would eject photons out one end and move in the other direction. AFAIK all the EmDrive experimenters are claiming that no radiation is coming out of the cavity.