

Thursday, 24 May 2018

Emdrive Trial by Media

You may have noticed that some of the mainstream scientific media are attempting to debunk the emdrive based on Tajmar's new result, but the data suggests that Tajmar does not yet even have a working emdrive and is looking at some sort of Lorentz force.

To demonstrate this, here is a plot showing Tajmar's newly measured thrust in comparison to the other ones. The thrust predicted by quantised inertia is shown on the x axis and the thrust observed is shown on the y axis. The diamonds show the comparison between the predictions and the data. Most of the diamonds line up along the diagonal line, meaning that QI does a good job of predicting the results (as does the Shawyer equation that also uses power times Q). One point to note is you can predict the thrust from the characteristics of the cavity (eg: Q, length, widths) not the cables. Tajmar's new thrust is way below the line (see the label: Tajmar2018). The thrust expected by QI for his setup was 0.19mN and his observed thrust was 0.004mN. This is almost fifty times smaller! If you have a car that is going 50 times slower than expected, then you can probably conclude that the engine is off. So it seems that Tajmar is not testing an emdrive yet, but is looking at some other, much smaller, effect.

This is further supported by comments from Phil Wilson who has pointed out that the cavity Tajmar is using does not have a resonance at 1.865GHz (the frequency he is inputting) and his results look very much like something else is resonating.

Also, what has been forgotten is that NASA were well aware of the potential problem of a Lorentz force, and showed their thrust was not from that. In their 2017 paper (see below, page 838, top right column) they said "The [cavity] was tested in forward, reverse and null orientations, but dc power cabling, routing & orientation was the same for all three configurations". What this means is that the NASA emdrive's thrust direction followed the cavity orientation and not the cable orientation. Therefore for a real working emdrive, it is the cavity and not the cables that make the thrust.

This is not a criticism of Tajmar, who I have the greatest respect for, but for the media response to his preliminary tests:


White et al., 2017. Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum. Journal of Propulsion and Power, Vol. 33, No. 4 (2017), pp. 830-841 https://arc.aiaa.org/doi/10.2514/1.B36120

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