To create physics for a ship or any other physical object in the game you can use a special program called "VE Physics Adjuster". This would allow you to define physical body for this object as well as other properties such as mass.
The program does not require installation and you can simply download it and extract to your desktop or any other location and then run.
Download: VE Physics Adjuster
You can also open .OBJ files by providing it's path as a launch parameter to the software VoidExpansePhysicsAdjuster.exe ModelName.obj, usually it is not necessary, but it could be useful to some advanced users.