That is the thing about the paper you showed me part of.

It has a microwave generator, and it bounces microwaves all around inside it. They do not leave the contained box, but the box moves forward.

NASA tried to "own" the idea, and say it didn't work. But the word got out that it did. Now they are saying that it is only a small force forward. However, any force, small or not, shows a action, without a equal and opposite reaction.

There is another device that does this. They call it Tesla's Stove. Experimenters find it easy to make a small one, and prove that it works. But they have trouble, mechanically, making a large one. It makes a force upward, with only spinning weights inside it.