Just child the terrain object to the space ship object to make it stick with it, and to make the terrain invisible for whatever reason then set it's terrain enabled to false.
quick test : throw this on your terrain object and try it ->

function Update(){
   if(Input.GetKeyDown(KeyCode.T))
      gameObject.getComponent(Terrain).enabled = false ;
 
   if(Input.GetKeyUp(KeyCode.T))
      gameObject.getComponent(Terrain).enabled = true ;
}