They didn't look at sonofusion, though, did they? That involves room temperature apparatus, but extremely high local temperatures -- due to collapsing bubbles. (Similar to sonoluminescence)

I remember this from the late Robert Apfel's work at Yale -- because wouldn't it just be swell if bubbles could be the basis for fusion and clean energy? The problem was that bubbles need to be perfectly symmetrical for sufficient collapse power and that is only possible in zero gravity.

Here is a paper from Oak Ridge National Laboratory.

https://www.sciencedirect.com/science/article/pii/S002954930...