I had a brief chat with Shadocat in Las Vegas regarding orbital habitats, which got me thinking about the best way to handle them and what part they could play in Aurora. This is a potentially complex area, especially as everything relating to colonies in Aurora is based on system bodies, not ships. I have been searching for a way to add the concept without a major code rewrite and I think I have found a solution. Already in Aurora is the concept of ships in orbit contributing to a colony, such as terraformers, mining ships or maintenance ships, so I am going to extend that to population as well. Population living in an orbital habitat, which is effectively a ship with Worker Hab Modules (or O'Neill Habitats or whatever they eventually are called), will be included in the population of the system body of which they are in orbit. This isn't of great benefit for ideal or low cost colony worlds but will prove very useful for high colony cost planets or non-habitable worlds, such as low gravity moons and asteroids. Instead of trying to live on a freezing small moon with minimal gravity, the population can live in orbit in hab modules with artificial gravity and climate control. The workers could then be used in mines, factories or orbital shipyards based on the moon/asteroid before returning to their hab module at the end of their shift. As well as adding the concept of orbital habitats, this solves the problem of long term low gravity exposure for small system bodies and makes asteroids/small moons much more useful in terms of colonies without adding the performance issues involved in making them habitable. It can also be done without any major code re-writes, although there are a few areas I will need to update. The only drawback is that this concept doesn't allow deep space, stand alone population centres but that can probably be handled in the future by devising a way of moving small asteroids to the desired location to act as an 'anchor' for the colony.
Now, to make this anything close to realistic, the actual habitats are going to be BIG! REALLY, REALLY BIG!! For comparison, the cryogenic transport module is 50 HS and can carry 10,000 frozen colonists. That is 200 colonists per HS and a HS is 50 tons, so one colonist per 0.25 tons. In Aurora, mass and volume are used interchangeably without defining the actual volume per ton, which isn't very realistic but it makes life a lot easier (if you want some form of visualization, Traveller uses a similar method and has fourteen cubic metres per ton). Besides, it can be explained away as part of the Trans-Newtonian techno babble. So, back to the 0.25 tons per frozen colonist. Lets compare that to crew quarters and troop transport bays. The crew quarter system requires 1 HS per 250 crew, which is actually more crew per HS than in cryo! My first reaction on realizing this was to increase the size of crew quarters but I think it would be reasonable to assume that this is primarily life support and bunks for the crew and that most of the crew time would be spent elsewhere within the ship. As bunks take up less space than cryo modules, I will live with this for now. Besides I just finished designing all the ships for my new campaign
Troop Transport Bays are probably the most realistic starting point for comparison as they are a self-contained module in which troops will live for months at a time. They are 50 HS and support 500 troops and their equipment, which is 10 people per HS, or 1 person per 5 tons. Civilians probably need more living space but don't have the same amount of equipment so it probably balances out, leaving us with 10 people per HS as a basis for hab modules. Using 50,000 people as the baseline, as that is the number required for a basic factory, that gives us a hab module size of 5000 HS, or 250,000 tons. Obviously that seems huge but it is probably on the small side given the number of people. However, huge doesn't necessarily mean expensive. The hab module is essentially just a living space and has no requirement for the structural integrity that would be associated with military systems or those needed to transport heavy cargo. Therefore the cost can be relatively low, especially given the economies of scale that would be involved. The cryogenic module that supports 10,000 frozen colonists is 100 BP. I going to fix the hab module cost at 200 BP, or 2x as much. Partly because freezing people and keeping them alive would be harder than just warming a huge living complex so there is some justification on costs grounds. Secondly, and more importantly, making it more expensive than this would probably make the hab module too expensive within Aurora's economic model. In the end, fun game play has to take precedence over physics as long as I can maintain internal consistency. Thirdly, as part of justifying the relatively low cost and making my life much easier in other areas (more on this later), the orbital habitat can only support inhabitants when it is in orbit. Due to its lightweight structure, it cannot be used as an extra-large colony ship. It can be towed from planet to planet but will automatically leave behind any colonists on board.
On a col cost 2.0 planet you need 10 points of infrastructure for 50,000 pop, the equivalent of a hab module. That costs just 20 BP and requires 500 HS of cargo space for transport. Even at 5000 HS and 200 BP, that makes the hab module 10x larger and 10x more expensive. Actually, it is cheaper than it appears because the population in habitats does not require any agriculture and environment workers so that percentage of the population is available for manufacturing instead. The habitat population is still considered for the service sector. Obviously as the colony cost rises (especially given the lack of an agriculture requirement for habitats) or if the planetary surface is unsuitable for colonization, the orbital habitat becomes much more attractive. Hab modules are intended to be specialized, for those times when you want to establish a strategic colony in a difficult or remote location, rather than for general use. Their main drawback is size rather than cost as they are difficult to move under their own power, although you can tow them just like any other 'ship'.
Another issue is that habitats are so large they could not be built by shipyards under the existing rules unless the shipyard was enormous. Therefore, any commercial vessel with habitation modules can be built by construction factories in the same way as PDCs. They can be built by shipyards as well if you have a shipyard large enough. As with other ship construction projects, any system modules in the population stockpile will be used to reduce the total construction cost for habitats built by either shipyards or construction factories. Therefore, you can choose between constructing the habitat and towing it to its destination, or building the components, moving them in freighters and then building the orbital habitat in the destination system. Because of their immense size, orbital habitats cannot be refitted, although at some point I may allow them to be combined.
Something else has also occurred to me while working on this. It's entirely possible for an Empire to have multiple populations on the same planet, especially given the recent introduction of genetic modification. In that situation, it is necessary for orbital habitats and other population-specific ships, such as asteroid miners, to be assigned to a specific population. Otherwise they would contribute to all populations of the same Empire on the same planet. Therefore, when a fleet completes an order that has a population as the destination, the ships of that fleet will automatically be assigned to that population. In addition, a ship can now be manually assigned to a population, using the existing population dropdown in the top right of the Ship Window. For Orbital Habitats and Mining Ships to contribute to a population they will have to be assigned to that population and in the same location.
The population capacity provided by orbital habitats is treated in a similar way to that provided by infrastructure. You deliver new colonists to a Colony as you do now, not directly to the habitat. The Colony itself will use the habitats to house as many colonists as possible before starting to use up infrastructure. When you pick up colonists from a Colony they will be taken from the surface first and only taken from the habitats when there is no surface population. When the percentage of the population dedicated to agriculture and environment is calculated, it will only be based on the surface population, not the total colony population. Growth will be handled independently for the surface and orbital populations, with colony cost and radiation only affecting the surface population. The orbital population will be treated as colony cost zero but with the limitation that the orbital population cannot exceed the capacity of the hab modules. Therefore, on a colony that is partly based on orbit and partly on the surface, the population growth in orbit will be zero. When calculating infrastructure demand for civilian trade, only the surface population will be considered. When calculating the size of the service and manufacturing sectors, the combined orbital and surface populations are considered as one whole population. Of course, in many cases the entire population will be either orbital or surface so none of the complications associated with populations that have both orbital and surface components will arise.
Below is a screenshot of a small Martian colony that includes both orbital habitats and infrastructure. Both growth rates are shown, as are the population capacities provided by both infrastructure and the habitats. Note that the agriculture percentage of 12.9% is a little lower than would be expected for a planet with a colony cost of 2.1818. This is because the actual percentage of 15.9% only applies to the surface population of 3.25m rather than the total population of 4m. 15.9% of the surface population of 3.25m is only 12.9% of the total population.
[attachment=0:1x2sh99g]Orbital.JPG[/attachment:1x2sh99g]
Because Orbital Habitats are very large ships or bases and use the class design window, as with any other ship design, I have not needed to include any new detection or combat code. In terms of detection, movement and combat, they are treated exactly like any other ship or base. You can detect them in orbit, or in transit if being towed or moved under their own power, and attack them as you would any other ship. If the orbital habitat is destroyed, I am assuming the population will evacuate to the surface of the planet around which it is orbiting. This saves a lot of potential messing about with civilian casualties. Of course, in many cases evacuating to the surface will be a death sentence anyway. If its is in transit, it won't have any population. Because the orbital habitat is assigned to a particular population and can be reassigned, it doesn't have any species limitations.
Here is an example of a basic orbital habitat and a second version with thicker armour, a small sensor and some CIWS.
O'Neill class Orbital Habitat 1,256,650 tons 20 Crew 2072.6 BP TCS 25133 TH 0 EM 0
1 km/s Armour 1-1037 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 1 PPV 0
Maint Capacity 1 MSP Max Repair 8 MSP
Habitation Capacity 250,000
This design is classed as a Commercial Vessel for maintenance purposes
This design is classed as an Orbital Habitat for construction purposesImproved O'Neill class Orbital Habitat 1,264,700 tons 52 Crew 3254.2 BP TCS 25294 TH 0 EM 0
1 km/s Armour 2-1041 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 1 PPV 0
Maint Capacity 2 MSP Max Repair 34 MSP
Habitation Capacity 250,000
Guardian CIWS (4x6) Range 1000 km TS: 16000 km/s ROF 5 Base 50% To Hit
This design is classed as a Commercial Vessel for maintenance purposes
This design is classed as an Orbital Habitat for construction purposesI hope the new habitats will add an extra dimension to colonization in v5.20
Steve
