This basically just means a ship that is not affected by the push of other ships, this means that you could create space stations that could hold ships as literal torpedos and would allow for arenas that the ships cpouldnt push around, this could only be added to active ship so no junk will just be stuck there
this could be done two ways:
do it as a part you can place on your ship, this means that when it would be destroyed it would start to move again, this also means that the part could only work if there was a command center
you could make it a setting, like setting ships on sides in creative which I think is less effective
this could allow for greater space stations and make Ion cannons Way more effective