Jet Propulsion

<p>Hi. I recently got a mentor that is a jet propulsion expert. She asked me to give her a general topic of something I would like to do for science fair dealing with jet propulsion. I want something interesting, yet fairly difficult (or very difficult??). Anyways, I've always been interested in JPL, Boeing, etc. that sparked an interest in jet propulsion as well. However, I am TERRIBLE at coming up with topic ideas. Any suggestions for topics?</p>