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Doesn't a standard microwave (or any other) transmitter produce a tiny force due to radiation pressure? I understand that this is different because the radiati

Doesn't a standard microwave (or any other) transmitter produce a tiny force due to radiation pressure? I understand that this is different because the radiation bounces around an enclosed chamber and so momentum wouldn't be conserved, but if the issue is to create propellant-free propulsion, doesn't that already exist (even though it's not practical)?

ribble 10y ago
> Doesn't a standard microwave (or any other) transmitter produce a tiny force due to radiation pressure? pressure against what?
- pmcollins 10y ago
  https://en.wikipedia.org/wiki/Radiation_pressure#Radiation_pressure_by_emission https://en.wikipedia.org/wiki/Radiation_pressure#Radiation_p...
  - ribble 10y ago
    this article includes a grey body that the force is acting upon. the difference with the EM drive's method of propulsion is, that while the article you posted describes a force reacting upon an external, "grey body," as is acceptable with the copenhagen interpretation of quantum mechanics, the EM drive force exhibits a characteristic betrayed by a theoretical pilot wave, which indicates a non-copenhagen interpretation of quantum mechanics, but rather a bohmann version of quantum mechanics, in which the force can act upon itself. run-on sentence alert.
gus_massa 10y ago
Yes, but they suppousedly got 4000 times the maximal theoretical value. I'll repost one of my old comments with more details: If you use a photon thruster (aka a laser or a flashlight in the right direction (or a microwave)), then the maximal thrust/energy ratio is at most 1/c = 3.33 nano-Newtons per Watt = 0.0033 uN/W = 0.0033 mN/KW. Someone compiled here two lists of experiments: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1302455#msg1302455 http://forum.nasaspaceflight.com/index.php?topic=36313.msg13... http://emdrive.wiki/Experimental_Results http://emdrive.wiki/Experimental_Results Some of the experiments are few years old, but you can compare the current result with 0.0033 mN/KW. The results in the tables vary from 3x to 200000x the theoretical maximum of a photon thruster. I think that the typical current value is x4000. It's a theoretical upper bound that is very easy to calculate using special relativity, and it depends on very fundamental laws, not tricky details of the universe. The theoretical bound is so fundamental, that it's even true if you use a graviton thruster instead of a photon thruster. This example is not totally made up, someone have an alternative impossible massless drive that "push against the far away stars". They claimed also a thrust/energy ratio > 0.0033 mN/KW, so it was also impossible from a theoretical point of view. Also, for the EmDrive, someone proposed that it emits twin photons that somehow cancel each other, but the pair still carry momentum. That explanation extremely wrong.

ribble 10y ago

> Doesn't a standard microwave (or any other) transmitter produce a tiny force due to radiation pressure? pressure against what?

pmcollins 10y ago
https://en.wikipedia.org/wiki/Radiation_pressure#Radiation_pressure_by_emission https://en.wikipedia.org/wiki/Radiation_pressure#Radiation_p...
- ribble 10y ago
  this article includes a grey body that the force is acting upon. the difference with the EM drive's method of propulsion is, that while the article you posted describes a force reacting upon an external, "grey body," as is acceptable with the copenhagen interpretation of quantum mechanics, the EM drive force exhibits a characteristic betrayed by a theoretical pilot wave, which indicates a non-copenhagen interpretation of quantum mechanics, but rather a bohmann version of quantum mechanics, in which the force can act upon itself. run-on sentence alert.

gus_massa 10y ago

Yes, but they suppousedly got 4000 times the maximal theoretical value. I'll repost one of my old comments with more details: If you use a photon thruster (aka a laser or a flashlight in the right direction (or a microwave)), then the maximal thrust/energy ratio is at most 1/c = 3.33 nano-Newtons per Watt = 0.0033 uN/W = 0.0033 mN/KW. Someone compiled here two lists of experiments: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1302455#msg1302455 http://forum.nasaspaceflight.com/index.php?topic=36313.msg13... http://emdrive.wiki/Experimental_Results http://emdrive.wiki/Experimental_Results Some of the experiments are few years old, but you can compare the current result with 0.0033 mN/KW. The results in the tables vary from 3x to 200000x the theoretical maximum of a photon thruster. I think that the typical current value is x4000. It's a theoretical upper bound that is very easy to calculate using special relativity, and it depends on very fundamental laws, not tricky details of the universe. The theoretical bound is so fundamental, that it's even true if you use a graviton thruster instead of a photon thruster. This example is not totally made up, someone have an alternative impossible massless drive that "push against the far away stars". They claimed also a thrust/energy ratio > 0.0033 mN/KW, so it was also impossible from a theoretical point of view. Also, for the EmDrive, someone proposed that it emits twin photons that somehow cancel each other, but the pair still carry momentum. That explanation extremely wrong.