Here are all the rules I can find on non-weapon bays on dropships and larger craft:
TM, P196: "On DropShips, however, transport bays—including those for fighters, BattleMechs and other units—must assign a minimum of 1 bay door each, to allow for entry and egress from the vessel. For any given vessel, the maximum number of bay doors is equal to 7 plus the vessel’s total weight (in tons) divided by 50,000 (rounded up)."
TM, P239: "Fighters, Small Craft and DropShips must separate any and all transport bays by type, but need not allocate them to equipment slots on the unit’s design."
TW, P239: "Cargo: Part of the unit’s cargo sustains damage, determined randomly between general cargo bays and unit bays. To determine the percentage of cargo destroyed, divide the amount of damage that caused the critical hit by twice the vessel’s SI. Multiply that number by 100, rounding fractions up. For DropShips and small craft, use the standard-scale damage value in this calculation. When a cargo hit occurs, roll 1D6. On a result of 1–3, general cargo suffrs damage (if present). On a result of 4–6, unit bays (if present) are affected. Round any fractions up."
The only limit to the number of non-weapon bays on a ship is the number of doors it can have (p196TM), but this doesn't seem to apply to large support vehicles. This means a 2.5mt warship could have FIFTY various cargo and unit bays. Based on the construction rules, it appears there is nothing stopping you building a unit with dozens (up to 50!) individual bays to avoid losing too much from any single hit.
Door hits are fine, it just randomly takes out some door somewhere, easy enough.
Based on the critical hit description I listed above (TW239), it really appears there are always just 2 bays, regardless of how the TRO lists them. The bays are "cargo" and "unit", and whenever that critical is taken you destroy a percentage of the carried units/cargo. The Aqueduct liquid cargo carrier (HB Perphery, p203), has 7 bays. This is really just for fluff, as what really matters is it has *CARGO* bays (31422 Tons in 5 bays), and *UNIT* bays (2 Fighters, 2 Small Craft, 2 bays). So any hit to this dropship with 7 SI would do DAMAGE/14*100% damage to either of those bays, 50/50 chance of either. I'm not sure if the part in bold means split between *ALL*, or just "all the ones listed, so if 6 bays, roll a 1d6 to see which one".
And also, along these same lines, when a bay is listed as "Fighters/Small Craft = 18" (Conquistador, TRO3067p184), does that mean 18 small craft bays that typically hold some fighters since they aren't split up?
And what about bays that say something like"
Bay 3: Small Craft (3) 0 Door
Cargo (225 Tons) 1 Door
(Vengeance, TRO3057R, p54)
Does that mean that the small craft have no launch capability, or can it just use the cargo doors? And if it can use the cargo doors, what about all the units like the Titan (TRO3057R, P88) that have bays like:
Bay 1: Cargo (696) Tons 2 Doors
Fighter (6) 2 Doors
It would be able to launch 4 of those 6 fighters in 1 turn? Or is there some wacky rule saying if 0 doors it can use other doors in the bay, but if doors listed those are the only doors that line item can use?
Thanks, built a construction app for all aero craft and got pretty confused in that last step of adding bays/doors :(