There is a university student team who wants to build a LOX/propene (aka
propylene) engine for their rocket for the Intercollegiate Rocket
Engineering Competition. I had never heard of propene before (and didn't
know it was the same as propylene) so I checked it out on Wikipedia.
Toxicity doesn't appear to be a major concern. The Wikipedia article also
says that Garvey Spacecraft Corp is developing a LOx/propene engine (and
confirmed by http://www.garvspace.com/Current_Projects.htm, last updated
over a year ago).
So it appears that it should be suitable for a student team--just wondering
if anyone has any information to add.
Thanks, Paul M