Science Fiction D&D - starships and vehicles

Following on from my 'quick n' dirty game system' blog post, I've got around to developing a simple, if not entirely accurate or balanced, system for starships and vehicles.

VEHICLES AND STARSHIPS

The stats for these are decided by the vehicle’s length. For every metre in length, a vehicle or starship has 1 hit point. For every ten metres all vehicles must have at least 1 crewmember. So, a starship 50 metres in length will have 50 hit points and 5 crewmembers minimum. A car 5 metres in length will have 5 hit points and 1 crewmember (driver).

For every metres in length over ten metres, a vehicle can hold 1 cubic ton of cargo.

Armour class is decided by length – the smaller a vessel is the harder it is to hit. The AC is added (or subtracted) to the basic to-hit target number of 10 (I'm using the D&D 4th to-hit system, now).

Length(metres) followed by: AC
1-10: 8
11-30: 7
31-50: 6
51-70: 5
71-90: 4
91-100: 3
101-130: 2
131-150: 1
151-200: 0
201-250: -1
Every extra 50m: -1 cumulative

Roll D20 higher than to-hit target of 10 + AC. If firer is using normal hand weapons (such as pistols or rifles) against the target, minus the vehicle’s current hit points score from the damage rolled (this way, handguns can’t really do any damage to huge vessels but can possible damage very small ones).

Each vessel has weapon slots. For every twenty metres in length the starship has a single weapon slot in which it can place a weapon.

Each weapon slot generates 1D8 points of damage from a single hit. So, a vessel with 3 weapon slots can fire three times and each shot does 1D8 points of damage. Each weapon must be manned individually.

However, weapon slots can be combined into a single shot and still be fired by a single crewmember. For each extra weapon slot added to the original for a single shot, add another 1D8 damage roll. So, one weapon slot does 1D8 damage, 2 combined weapon slots 2D8, 3 slots 3D8 and so on. These slots cannot be added to or removed at random – the combined feature means heavier weapons and must be chosen during creation. Pilots can fire any single weapon anywhere on the ship.

Any vehicle/starship hits on characters are multiplied by 10.

EXAMPLE: A 50 meter starship – 50 hit points, minimum crew 5, AC 6, 2 weapon slots, able to carry 50 cubic tons of cargo.