1) Availability of Water. Probably at least 2.00 colony cost with no water, with this reducing to zero once a certain hydrosphere coverage is available (maybe 20%). Water would be created by adding water vapour to the atmosphere. Over time this would condense out of the atmosphere and create a hydrosphere. Exact mechanics TBD.
Absolutely yes. People underestimate how important water is to life on earth. The entire water->water vapor->rain cycle is the very basis of life on earth. Not to mention the effect humidity has on temperature excursion in the day-night cycle. I'll also say, finally at long last. Wanted this for ages
2) Too much CO2 is harmful. Essentially C02 above fairly minimal concentrations would be a dangerous gas.
Agreed, and another thing I've wanted forever.
3) Small planets are faster to terraform than large ones. The speed at which terraformers add atmospheric pressure would be modified by the surface area of the planet (this would also apply to the hydrosphere coverage), using Earth as the baseline.
Yes, yes, yes. Another thing I've wanted forever because it makes sense.
4) As a corollary to 3), a planet's gravity would determine if any gases could be added.
Rather than calculate the exact situation, which would be based on escape velocity, temperature and the molecular weight of the specific gas, I would have a fixed boundary, perhaps 0.1G, as the lowest gravity that would retain an atmosphere. This would result in a lot of low gravity bodies that could be colonised at 2.00 LG (which can't currently be colonised) but which would never improve beyond that point because they would not retain the atmosphere required for terraforming.
Putting a 0.1G limit sounds a good compromise to me. Anything lower belongs to the planetoid-class really. And for the sake of actually playing the game, some sort of simplification has to be used.
The combination of 3) and 4) would mean a significant disparity in how fast worlds could be terraformed, but not to extremes. For example, compared to Earth, Mars would be terraformed 3.5x more quickly, Ganymede 5.9x more quickly and Luna 13.5x more quickly. In fact, it would probably make sense to slow down the base rate of terraforming to the middle of that range, aiming for perhaps 25% - 50% of current rates. In the case of 25%, the rate of terraforming vs current would be:
Earth: 25% of current speed
Mars: 88% of current speed
Ganymede: 147% of current speed
Luna: 337% of current speed.
Large planets would take a suitably long time to terraform, with small planets and moons (that are still large enough to retain atmosphere) being terraformed relatively quickly. Depending on how much effort is required for the hydrosphere element I could make the reduction 50% instead on the assumption that the additional water vapour would also act to slow down the process.
50% base terraforming reduction sounds a good compromise to me. Maybe it is even too much. Slowing down the base rate of terraforming to 25% would make colonize larger planet wayyy to slow. Not really feasible in the length of a normal Aurora game.
For a low gravity colony, I think there should be a minimum colony cost. Even if the air is breathable, some form of gravity assistance would still be needed. Perhaps LG worlds are always at least colony cost X, so (in the above situation) you could reduce the colony cost to X by improving the temperature, but the low gravity prevents any improvement beyond that.
X = 2.00 seems the obvious choice, but that would mean there was no point making the air breathable or adding water, so perhaps 1.00 is a more interesting option (essentially the low gravity element of the LG infrastructure without the life support requirement).
I agree that low gravity should pose some problems even if a planet is terraformed. But I think colony cost 1.0 is too much. My suggestion would be that the colony cost, in case of a terraformed planet with low gravity, be set at 0.5.
I think it's a good, realistic compromise: a planet which IS low gravity, but with a perfectly breathable atmosphere is four times less "costly to live in" than, basically, a space base on mars. That is what colony cost 2.0 is at the moment.
It makes sense to me, considering all the things you don't NEED compared to a pressurized, self reliant space base. Which does not have the luxury of having structural faults, because in cause of a structural problem most of the inhabitants would die. So there has to be so much more redundancy, safety measures and the like. On a terraformed, low gravity world you don't die horribly if something breaks. Hence, 4 times less costs than a pressurized base.
I've been considering the questions raised regarding planetary capacity. Given the proposed changes in terraforming, some rules regarding planetary capacity would provide a reason to colonise larger worlds.
So using that as a base, we get the following growth rate penalties and max populations:
That doesn't look too bad, with Mars still worthwhile at 3.4 billion max pop, the Moon less than one billion, dwarf planets or medium moons ten of millions, small moons single millions and small asteroid less than one million. That should provide some flavour and give a good reason to terraform larger bodies.
This is perfect and another change I've waited for a long, long time. Those numbers also seem good for a self-reliant, normal world. They should really be visible before you colonize a planet however. Add another couple of fields to the system and planet view so we know those numbers and can more easily choose what to colonize.
However I have two other proposals to integrate in this.
1) I think that there should be a bonus/malus to population-generated wealth (not to financial centers generated wealth) based on planet size. The reasoning for this is: a larger planet has a lot more "resources" and a lot more "real estate" than a small planet. I'm not talking of minerals here.
A lot of Earth's "riches" come from the impossibly complex ecosystem we have, with all its different environments and biomes. Just think of chemistry, biology, biotechnologies and the like. So, since a terraformed planet is basically a planet where the atmosphere was added and an ecosystem has been imported/developed, it would make sense that a terraformed planet has a bonus/malus to wealth generation based on size, compared to baseline wealth generation on Earth.
This would also imply that any planet which is not terraformed, and so has no ecosystem, would have a malus. And it does make sense, what do these people sell anyway? Space dust? A lot of the normal activities we have on earth are not possible or more costly in a pressurized, relatively cramped environment. So a malus to wealth generation seems logical.
A planet should be allowed to go "beyond maximum". At a cost. Sci-fi is full of examples of such "hive worlds", which a population far beyond its normal limit. The cost of that is that the planet is no longer self-reliant. And that there is so much population that the average wealth generated goes down compared to what it could be on a normally populated, self-reliant world.
My suggestion to model this is that the population limit can be increased by adding infrastructure. I'm not really sure how much would be appropriate though. And that a wealth generation malus should be put in place, progressively increasing as population grows beyond the normal planet limit, because more people have to do with less. Less resources, less space.