Can this have any other use other than propulsion in a vacuum?
I have no idea.
I don’t think the vaccum would affect the drive working. It was used in the experiment to show it would work in a vacuum.
Microwave in a vacuum would not be attenuated and scattered like it would be in our atmosphere. That might be the point of the experiment. But microwave is not like laser energy where it is focused. Microwave can be beamed, but it does disperse over distance. Strange.
I’m still not certain about the legitimacy of the actual .pdf that was linked.
This could be pop science BS article. I’m not sure about it.