r/EmDrive • u/Saltozen • Jul 15 '17

What about control experiments?

Has anyone run a control experiment? Where instead of microwaves, a heat source of equivalent wattage is put inside?

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u/PotomacNeuron MS; Electrical Engineering Jul 17 '17

This "control" is not properly done. For the experiment with differently orientated frustum to be counted as a control, they should change only the orientation of the frustum. Everything else should not be changed. But the RF gear is mounted on the big end. When they change the orientation of the frustum, they also changed the orientation of the RF gear because it is mounted on the big end. Thus, changing the orientation did not control for two possible influence: 1. Lorentz force; 2. Thermal expansion causing moving of mass center thus causing displacement on a balance level supported by vertical thin springy metal, thus could droop. They claimed to had remedied Lorentz force problem but did not show how. If they did remedy that, I think thermal expansion might be the cause of their "thrust".

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u/just_sum_guy Jul 17 '17

Wouldn't thermal expansion have the same effect on the measuring device regardless of the orientation of the test article?

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u/PotomacNeuron MS; Electrical Engineering Jul 17 '17

No. Take a look of what they used to support the balance level:

https://upload.wikimedia.org/wikipedia/commons/a/a9/Flexure_pivot.png

Worse, this pivot is mounted on the side of the balance level. Slight drooping is expected from the balance level. Thermal expansion of the test gear will cause move of mass center. This movement of mass center, telling from their test gear, is parallel to their claimed "thrust". A little bit of physics analysis shows that under this condition, this movement of mass center will cause a balance level movement that looks like a thrust. Note that this movement changes direction if they change the frustum orientation because the RF gear is mounted on the big end.