Celestia Forums

I read this somewhere but I am not sure... Is it possible to manouver a starship inside Celestia?

Not in Celestia.

However, you should investigate
"Mostly Harmless" at http://mostlyharmless.sourceforge.net/index.htm
and "Orbiter" at http://www.medphys.ucl.ac.uk/~martins/orbit/orbit.html

A quibble:

Celestia does include joystick commands. Although they don't make it into a real spacecraft simulator, they may be adequate for what you want to do. They're listed in the User's Manual and in the Help page (controls.txt)