I read about ion engines in 1952, when I was in High School, we are leaping forward.
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This is not an ion engine. An ion engine shoots out charged ions at extremely high velocity to achieve thrust from a relatively small (wight wise) energy source.
As described, it appears to me that Conservation of Monentum AND Conservation of Energy principles are being violated. Personally I have more faith in these laws than in this report. But if the report is true then I expect that some smart guy or gal will find the actual energy source that is being depleted as the craft is being accelerated.
The fact that the one that was designed to fail worked as did the other tells me there may be an outside agency impacting the results.
Nothing mysterious nor does it appear to violate any physical laws. It simply relies on radiation pressure. The description is somewhat misleading regarding “no tradition fuels”, but generating microwaves obviously takes energy, usually electrical to drive klystron or magnetron tubes. So think of a wave guide (pringles can) attached to a nuclear battery. The poynting vector goes out the tube nozzle producing radiation pressure, and by conservation of linear momentum our battery and wave guide go the other way.
Thanks.