Part 9: Colony Cost and Terraforming
I recently answered a question on terraforming so I am going to convert that answer into the next section of the tutorial.
Firstly, lets talk atmospheres. Our own atmosphere has a variety of gases but only Nitrogen, Oxygen and Argon are 1% or above. Everything else is in tiny amounts. Aurora only bothers with the major gases in a planetary atmosphere so planets will generally start with no more than three gases in their atmosphere. Open up the Economics window and take a look at the Environment tab for Earth. The list of gases in the Atmospheric Data section shows the following information:
Nitrogen 79% 0.79 atm
Oxygen 20% 0.2 atm
Argon 1% 0.01 atm
Total Atmospheric Pressure: 1
This shows both the percentage of each gas in the atmosphere and the atmospheric pressure (atm) of each gas. As the atm amount is based on Earth's atmospheric pressure of 1, the atm figures match the percentages. Lets create a colony on Mars and compare this to its atmosphere. Open up the F9 System View window, which provides detailed information on every body in a star system (you can open this by pressing the orange sun icon at the middle top of the system map). It is useful to check this view every time you find a new system, just to see what types of planets you have found and their colony cost (more on colony cost later). If there is more than one star in the system, each star and any associated planets will be on a separate tab. If the System View is slow to load, switch to the options tab and select Hide Asteroids then switch back to the Sol-A tab. Select Mars and press the Add Colony button. Open the Economics window, or press Refresh All (middle bottom) if it is already open. You should see a new colony for Mars. Select it and take a look at the Environment tab. The atmospheric data shows:
Nitrogen 70% 0.007 atm
Carbon Dioxide 30% 0.003 atm
Total Atmospheric Pressure: 0.01
The atmospheric pressure on Mars is only about 1% of that on Earth so the atm figures are tiny. In effect, Mars has almost no atmosphere at all. The atmospheric pressure on Venus is about 100x greater than on Earth and 10,000x greater than Mars.
The principle of Terraforming in Aurora is based on changing the atmosphere in order to alter the environment of the planet so it is suitable for your species. Before getting into how that works, we should probably discuss how you know what is suitable for your species. Each species in Aurora has environmental tolerances with their midpoint being their homeworld. The habitability of planets will vary considerably depending on the species tolerances so a world that is ideal for humans may be uninhabitable for some other species and vice versa. Way back in Part 1 of the tutorial, covering game creation, we entered some values in the Species Tolerance section of the New Game window to set these values for human. As a reminder, those were a maximum deviation in oxygen pressure of 50%, a max deviation in gravity of 70%, a max deviation in temperature of 22 and a max atmospheric pressure to 4.
Fortunately you don't have to remember those as you can find them in the top right of the F9 System View Window. Open it up and take a look. The section is called Environmental Tolerances. The first item is a dropdown showing the selected species while the second shows which gas that species can breathe. You can have methane breathers in Aurora in which case every reference to oxygen in this tutorial would read as methane. There are four rows below this showing the min/max for gravity, oxygen and temperature and the max for pressure. If you are playing through this tutorial from the start, those values should show that an ideal habitable world for humans will have a temperature between 0 and 44C, an oxygen pressure between 0.1 and 0.3 atm, a gravity between 0.3G and 1.7G and a maximum atmospheric pressure of 4.0 atm.
In addition to the individual species tolerances, the requirements for an ideal habitable world are no dangerous gases such as Chlorine or Hydrogen Sulphide and a maximum oxygen percentage of 30%. A planet that doesn't meet the gravity criterion is uninhabitable and there is nothing you can do about that. Falling outside one or more of the other criteria means the planet will have a colony cost above zero. The colony cost measures the amount of infrastructure required to support the population. The formula for required infrastructure is Population in millions x Colony Cost x 100. So a population of one million on a planet with a colony cost of 2 would need 200 infrastructure. A population of 15 million on a population with a colony cost of 0.8 would need 15 x 0.8 x 100 = 1200 infrastructure. If there is insufficient infrastructure for the population there will be negative growth, with the percentage based on how bad the shortage is, as well as unrest. You don't need to remember the formula as each population will show the max population for the available infrastructure.
Note that you can put ground bases, troops, sensors etc. on any world except a gas giant, regardless of the habitability. If you want an actual population though, which you will need to run shipyards, factories, etc,, then the planet has to be habitable or at least have enough infrastructure for the inhabitants.
The colony cost is calculated in the following way. The five checks below this paragraph are made. Whichever results in the highest colony cost, that will be the colony cost for the planet. You can see these factors in the Colony Cost Factors section in the lower left of the F9 view for the currently selected planet.
1) If the atmosphere is not breathable, the colony cost is 2.0.
2) If there are toxic gases in the atmosphere then the colony cost will be 2.0 for some gases and 3.0 for others.
3) If the pressure is too high, the colony cost will be equal to the Atmospheric Pressure divided by the species maximum pressure with a minimum of 2.0
4) If the oxygen percentage is above 30%, the colony cost will be 2.0
5) The colony cost for a temperature outside the range is Temperature Difference / Temperature Deviation. So if the deviation was 22 and the temperature was 48 degrees below the minimum, the colony cost would be 48/22 = 2.18
In the case of Mars, the gravity is OK, the atmosphere is not breathable, there are no toxic gases, the pressure is not too high, there is no oxygen and the temperature is too low. Therefore the colony cost will either be 2.0 for the lack of a breathable atmosphere or the colony cost for the temperature differential, whichever is higher. Assuming the temperature colony cost was 2.18, which would also be the colony cost for Mars, the best way to start terraforming would be to warm up the planet until the temperature colony cost was less than 2.0, at which point the lack of a breathable atmosphere would became the main issue and you could start adding oxygen. Once the atmosphere was breathable, you would go back to worrying about temperature.
Terraformers can add or remove a small amount of a selected gas over time. The amount added is measured in atmospheric pressure (atm). Note that as you add atm for one gas, the percentages of the different gases in the atmosphere will change. A single terraforming module or single terraforming installation with basic tech can add 0.001 atm per year. In other words, it could generate Earth's atmosphere in about 1000 years. That can be improved by researching the racial terraforming rate and by building more terraformers. Mars and Venus are both hard to terraform because their atmospheric pressure is so different to Earth's. Mars essentially has no atmosphere and you have to start almost from scratch. The first thing you need to do to make an atmosphere breathable is to ensure the atm of oxygen in the atmosphere falls within your species' tolerance for Oxygen. Assuming the tutorial values for human tolerances, on Mars you would need to create enough oxygen to get the oxygen atm to 0.1, which for one terraformer at the basic tech level of 0.001 per annum will take 100 years. If you had twenty terraformers though, it would only take five years. Increasing the Terraforming rate to 0.002 would halve the time. As you may have guessed, terraforming requires a considerable investment of time and resources.
So you get the 0.1 atm of oxygen into the Martian atmosphere. Is it breathable? Unfortunately not because pure oxygen atmospheres are a bad idea. Apart from the unfortunate consequences of striking a match, breathing pure oxygen over long periods causes lung damage. So an atmosphere in Aurora is not breathable unless the oxygen content is 30% or less. So if we need at least 0.1 atm of oxygen and that can't be more than 30% of the total atmospheric pressure, what does that total atmospheric pressure need to be? 0.1 * 100/30 = 0.333, so we need a total atm of 0.334 or another 0.234 atm, which will take another 234 years for the lonely terraformer. This can be any non-Toxic gas. Nitrogen is a reasonable choice or if you also need to change the temperature too, either up or down, you can use a greenhouse gas or an anti-greenhouse gas. For Mars, Carbon Dioxide would be ideal, although you could also use the abstract Safe Greenhouse Gas.
As you add or subtract any type of gas to/from the atmosphere, the atmosphere will be updated and that will also affect the temperature. Every system body has a base temperature and a surface temperature. The base temperature is based on the solar infall from the star (or stars in binary systems) while the surface temperature includes adjustments for atmosphere and planetary albedo (which is the reflectivity of the surface). The formulas used are shown on the Environment tab of the Economics window
Surface Temperature in Kelvin = Base Temperature in Kelvin x Greenhouse Factor x Albedo
Greenhouse Factor = 1 + (Atmospheric Pressure /10) + Greenhouse Pressure (Maximum = 3.0)
So every gas adds a little to the greenhouse factor but greenhouse gases add 10x as much. You get other benefits from warming as well. If the hydrosphere for a planet is Ice Sheet rather than Liquid Water (check the F9 view again), then at a certain point the ice will melt and form oceans. This will change the albedo because the ice that was reflecting heat back into space just melted and you will see a jump in temperature. The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.
As the pressure increases, you will see the percentages of different gases changing. If there is enough oxygen in terms of atm then once the oxygen percentage drops below 30%, the atmosphere will be breathable
Venus is almost impossible to terraform in Aurora. Each species has a maximum atmospheric pressure (Check F9 again to see yours). Before anything else, you would need to reduce Venus below that point. Assuming your species tolerance is about 4 atm then reducing the Venusian atmosphere, which has a pressure for 100, to that level would take our solo terraformer 96,000 years
You best bet for terraforming is to find a planet where the conditions are much closer to those on Earth. For example, you might find one with the right temperature and sufficient atmospheric pressure but the oxygen atm is 0.08 instead of the required 0.1 (or whatever your min oxygen atm tolerance is). Making this atmosphere breathable would involve adding just 0.02 atm of oxygen, which would take the solo terraformer 20 years, or 1 year for 20 terraformers. Equally, a planet with an already breathable atmosphere that is a little too hot or too cold can be made ideal by adding/subtracting greenhouse gases or adding anti-greenhouse gas.
Another consideration is Dangerous gases. An atmosphere will never be breathable if it contains gases such as Bromine, Chlorine, Sulphur Dioxide, Methane, Ammonia, Flourine, Carbon Monoxide, Nitrogen Oxide, Hydrogen Sulphide, etc. All these will have to be extracted from the atmosphere by your terraformers
Terraformers can even be used as weapons. If you found a planet where you wanted to loot the industry but you didn't want to bombard or invade, you could slowly extract the oxygen from the atmosphere.
The actual mechanics of using terraforming in the game interface are relatively straightforward. If you have any terraforming installations on a planet or any ships with terraforming modules in orbit, go to the Environment tab, select the gas you want and check the Add Gas checkbox if you want to add the gas rather than remove it. Terraforming installations can be built by industrial capacity and transported to a different planet with freighters. A Terraforming Ship is easy to design. Copy your freighter design, remove the cargo holds and cargo handling systems and add a Terraforming Module (or perhaps two). If you don't yet have Terraforming module tech, you can Instant it or research it using the Research tab of the Economics window. It is under Construction / Production