Personal scale is anything the size of a personal vehicle, fighter, or tank and smaller. PCs interact without penalty with things this size.
Starship scale is too large to be affected by personal scale characters or vehicles unless they have a special aspect or set of stunts that allows them to do so. This typically means one use rockets or rail weapons. Large cannons such as those mounted on tanks or torpedoes mounted on fighters can attack Starship scale targets by purchasing stunts. This means such weapons can be used more than once. Starship scale weapons firing at personal scale targets automatically inflict a Moderate consequence if they hit. If success with style is achieved, a severe consequence is inflicted.
Celestial scale reacts the same to starship scale targets as starships react to personal scale targets. Celestial scale things can't target personal scale things, but a personal scale thing caught in a blast from a Celestial scale attack is immediately Taken Out.