Science Alert reports that accurate testing of the so-called EM reactionless drive showed that it does not produce any thrust. A previous test at NASA Eagleworks lab claimed to have detected thrust, but at a statistically insignificant level.
The latest attempt to replicate the shocking results has resulted in a simple answer: the Eagleworks measurement was from heating of the engine mount, not any new physics.
The Conservation of Momentum is a bedrock principle of Physics, so no one should be surprised when a real world apparatus conserves momentum. There ain’t no such thing as a free lunch.