What movie star, who once was filmed in a nude scene that brought her the attention of the film world, and who was in some major films (and turned down a role that would have made her even more famous), is credited for inventing a part of a weapons guidance system?

I'm going to venture a guess---Marlena Deitrich?

No cigar for you, Kelley. Sorry.

Hedy Lamarr co-invented a frequency hopping torpedo guidance system with George Antheil and patented it in 1941.

Well Done, Berger ! See the Internet Movie Data Base for details.