1) While a violation of a widely accepted law of nature is indeed unlikely - it's not like it hasn't happened before.
2) There may yet still be some way to model the experimental data that at once makes the em-drive viable, while still preserving conservation of momentum. Still unlikely, but arguably more likely than 1).
3) And while these both remain unlikely - it is yet rational to have an increased credence for them while the experimental data remains unaccounted for. In fact, it's arguable that this increase of credence is significant - for if it were not, performing the necessary experiments to find out either way would be a waste of time. There are of course some very smart domain experts performing these experiments. Your tone and use of the word 'know' implies their irrationality. I would advise greater humility.
1) While a violation of a widely accepted law of nature is indeed unlikely - it's not like it hasn't happened before.
2) There may yet still be some way to model the experimental data that at once makes the em-drive viable, while still preserving conservation of momentum. Still unlikely, but arguably more likely than 1).
3) And while these both remain unlikely - it is yet rational to have an increased credence for them while the experimental data remains unaccounted for. In fact, it's arguable that this increase of credence is significant - for if it were not, performing the necessary experiments to find out either way would be a waste of time. There are of course some very smart domain experts performing these experiments. Your tone and use of the word 'know' implies their irrationality. I would advise greater humility.