Thanks for all the comments and feedback related to landing operations.
I haven't completely decided on the final numbers yet, but in principle I am going for the following options for landing on planets:
1) Troop Transport Bays will be similar to before, except there are now three sizes (small, standard, large), which are: 100 ton (2 HS), 1000 tons (20 HS) and 5000 tons (100 HS). This is a commercial system and functions in the same way as in VB6 Aurora.
2) Troop Transport Bays - Drop Ship Equipped is a new module which can function as a normal troop transport bay or quickly deliver troops from orbit using abstract drop ships. If the fast orbital delivery is chosen, there will be two options for the drop - Normal and Abandon. A normal drop will include waiting for the drop ships to return to the bays, which will require two minutes without additional research. A new tech line will reduce drop ship return times, starting with 90 seconds for 2000 RP and ending with 20 seconds for 64,000 RP. In an Abandon drop, the drop ships make a one way trip, allowing the ship to leave orbit immediately after the drop. In this case the bay is damaged (to simulate the loss of the drop ships) and can only be repaired at a shipyard. A ship with intact drop ships can also pick up troops from a planet, although this requires double the normal return trip time (as it is faster to unload than load). In all cases, the ship may only carry out landing or recovery operations if it starts the movement phase in the same location as the planet. For example, in an Abandon drop, the troop ship will arrive at the planet, take any fire for that turn, then launch drop ships and move away in the following turn. There are drop ship equivalents for the three normal bays. They have the same capacities but are 20% larger, 150% more expensive and a military system.
3) Troop Transport Bays - Boarding Equipped is a new type which can function as normal troop transport bays or launch infantry units in a boarding attack against a hostile ship (in a similar way to VB6 Aurora). There are equivalents for the Small and Standard normal bays. They have the same capacities but are 10% larger, 50% more expensive and a military system.
There are no longer any short-duration troop transport modules, as the 'landing craft' are now the abstract drop ships. This is partly to reduce micromanagement and the number of different ground-related orders, but also to create a real flavour of an opposed landing and to require investment in 'amphibious' operations. Any STO weapons on the surface will be able to target the landing ships on the way in and out of the drop zone. The player has a few options in terms of the troop ships. For example, large and heavily armoured dropping large formations, small and fast with small formations or raiding parties, or bare bones and expendable. Of course, additional ships can accompany the troop ships in an attempt to distract or suppress the defences.
In terms of orbital bombardment support from ground units, I will use a system where a ship is linked to a formation with Forward Fire Direction. Ships will function as bombardment units similar to artillery. I will probably use 20x the square root of the energy weapon damage for the bombardment value with half that as the AP value. So that would be (AP/Damage) 10/20 for a 10cm railgun round or gauss cannon, 17/35 for a 10cm laser, 40/80 for a 25cm laser, etc.. The smaller weapons would be more effective en masse against infantry or static weapons while the larger weapons would be more effective against vehicles. Each Forward Fire Direction component will be able to support one ship or a number of fighters (number TBD).
I haven't completely decided yet on fighters, but I at the moment I am leaning towards new, relatively small, ground-specific modules for 'normal' fighters. Anti-air units will have a ship-type damage value, rather than a ground-type value. For the moment, there will be no 'ground unit fighters', although in the future I might add some 'attack-helicopter' type units.
Of course, all of this has to be coded so I might run into something unexpected at that point which changes things. I think it will be obvious to everyone that this diversion into completely changing ground combat has put C# Aurora back a few months. This is probably the largest overall change so far in game mechanics so I have been giving it a lot of thought before diving into the programming. Also, things are going to be slow over the next few weeks due to the Xmas run-up, although I should have some time off work over the holidays and get some work done then.