Modeling these has proved to be very difficult. However I found a great tutorial by Roland Baron (at SciFi Meshes ) that briefly explains how he tackled it, and gives some great advice and ideas in how to break up the basic forms involved with the total nacelle shape. I can't say enough what a fantastic help this has been. And while I haven't followed everything exactly as he laid out, just seeing how someone else approached modeling these has given me ideas about how to move forward. So, if you ever decide to model the Enterprise from "Star Trek: The Motion Picture" check this out!