That "cresent" shape made me think all kinds of dirty thoughts.
On topic: Your designs lack form, balance of shapes, and flow. I suggest you do a lot of concept sketching before you go into the 3d stuff. Post your sketches on the forum. Also, try to copy drawings of other space ships. If you do it often enough, you'll establish a library of shapes and forms in your head and be able to use them in ways that work best.
I can comment on this model here, but nothing I say will really help you. You're at a point where you need practice and understanding of form before I can give you helpful critique.
