In the steampunk genre, I was wondering if some kind of steam powered death ray could be done. After a couple of search on google, here’s what I found. It seems astronomers observe natural masers in space. The article mention a 1.3cm wavelength with water vapour at 1000K:
Once we have a maser, perhaps we can pump a laser. Imagine: a steampunk laser powered by steam!
Applied to rockets, you’ll have steampunk space exploration!
Maybe it’s not practical, but it may inspire some good fiction.