King of the Rocket Men (1949), The Rocketer (1991)

King of the Rocket Men is a 1949 Republic serial that mixes crime and science fiction. 

There are those who consider it to be the last great Republic serial.

The hero battles a crime lord, with the aid of a rocket suit. It's a lot of fun.

My full review can be found at Cult Movie Reviews.

And for an equally enjoyable later rocket man movie, The Rocketeer (1991) is highly recommended.