Can I gain ranks with both the federation and the empire?

[Althure]

I tried searching but couldn't find answer on forums, so I apologize if it has already been answered.
I want to rank up empire because of the imperial clipper (I want one!) but I gained a lot of rep with the feds just doing random stuff and got the rank progression missions for feds popping up. So if I rank up feds does it block the imp progress or do they cancel each other out or...?

Oh and what about the alliance? I mean a war between them will probably happen at some point, what then?

 

[woodhouse]

I just got Outsider with the Empire while I am Midshipman (3rd rank) with the Federation.
So the answer is: yes, it doesn't seem to make any difference if you're already allied to the other power.