sideranautae said:
Looking over the rules (ground to spacecraft damage) and the reverse, it is safe to say that the battlefield would be dominated by armoured small craft over grav tank "vehicles" if they were available.
I'd say there is plenty of room for personal interpretation and what I call filling in the blanks the rules don't cover. Of course there is house ruling too.
Maneuverability
What is the maneuver drive in space craft (small or large) and how does it work? They are designed to produce thrust and these ships need to be streamlined to work in an atmosphere.
A streamlined ship is designed to enter a planetary atmosphere, and can function like a conventional aircraft.
One could say, like a aircraft, a small craft can not hover and a grav vehicle might have certain advantages.
Rate of fire
While certain publications have have clarified it (Mercenary: ship fire once every 3 rounds of ground combat), if you don't own them or don't want to adhere to them, there could be a vast difference due to a small craft with a 6 minute combat round, and a vehicles personal combat 6 second combat round. So a grav tank could possibly take out three targets for every one a small craft takes out.
Size of target
Weapons and targeting systems designed to hit ships which are rapidly moving and hard to turn might have trouble targeting a small nimble target. Possibly even trouble hitting a small stationary object. Can they even lock on to something the size of a man? I was thinking their would be size modifiers somewhere but I couldn't find them just now.
Stationary targets
Speaking of stationary targets, would this fall under ortillary for ships?
Other targeting modifiers
How do a ships weapon targeting systems function? Motion, heat, other energy emissions? Could they lock on to a man not generating much? Would energy emissions from a variety of sources in urban warfare be a problem? Ships typically are not bunched together, would their be trouble differentiating between friend and foe locked in close combat? (close for ship based ranges is 1-10km).
A grav tanks targeting systems may be sensitive enough to lock onto the heat of an individual, target gps coordinates, and otherwise target ground forces in ways a small craft can't.
EDIT:
Crewing
A Grav tank has a crew of 2. One can fly and one can shoot. A Light Fighter only has a crew of one and needs to fly and shoot. I forget where, but I think there is a rule for -DM due to trying to do two things at once. Even if there is no rule, it isn't breaking the rules for a GM to impose a penalty.
Scale
The rules use the term "Starship scale" when discussing modifiers. A small craft light fighter is 10 tons. A Grav Tank is 12 tons. Do the rules really mean for such a small craft to be considered on the same scale as a ship that is thousands of tons?
A Vehicle could be considered something other than personal scale. The rules already say that an attacker (people, other vehicles and ships too? or just people?) gets a +1DM to hit most vehicles because of their size.