Ecumenopolis

An ecumenopolis, also called a World-City or Megalopolitan Planet, is a planet that has been developed to the point that the entirety of the landmass has been developed into a continuous urban sprawl. An ecumenopolis must be designed and developed deliberately and as a whole in order for it to be sustainable, and as such they are massive projects, taking the concerted cooperation of the local star system and other systems in the region.

Development Process
The development of an ecumenopolis is a long, arduous process, taking many years. It generally begins with the discovery of a star system with several planets viable for Terraforming, and at least one major planet or moon within the Planetary Green Zone. If the system proves to be a large center for new development then the creation of an ecumenopolis becomes a viable option.

Choosing a Planet
For a planet to be viable for conversion to an ecumenopolis it must meet the following conditions:


 * It must be in the Planetary Green Zone so that the surface temperature is not too extreme in either direction.
 * There does not need to be a substantial atmosphere, but if there is the toxicity level must be below a certain threshold or the Aeroforming process will be prohibitively expensive.
 * The world must be geologically sound, with little or no tectonic movement. A significant degree of tectonic movement can occasionally be engineered around, however it usually poses too significant a risk to the structural integrity of the ecumenopolis to be dealt with.
 * The planet must be part of a planetary system that contains other terrestrial worlds viable for colonization or mining, as well as gas giants for fuel collection.

Colonization and Initial Infrastructure
Once the system has been fully mapped and explored, worlds viable for the Terraforming process will be colonized and temporary settlements will be established. All other terrestrial worlds in the system will be built into mining colonies, while gas planets will be surrounded with Fuel Rigs to refuel outbound vessels and  Manufacturing Rigs to produce new vessels for material transport within the system.

On the selected planet surveying and mining colonies will be established to ensure its suitability. Once a Core Map has been made final analysis is done to determine viability. If the planet is approved then initial preparations begin.

Initial Preparations
Before development can begin an atmosphere must be cultivated. Preferably the planet will have an existing nitrogen/carbon-dioxide atmosphere, which can be supplemented if too thin, though if not an atmosphere can be synthesized from the gasses of the local gas planets.

In order synthesize an atmosphere, hydrogen and helium gas is harvested from the gas planets and is alchemically synthesized into nitrogen, carbon, and oxygen. Carbon and oxygen are combined into carbon-dioxide, and relative levels of each gas are produced in quantities depending on the type of atmosphere being created.

The gasses are then liquefied and shipped to the planet. After being shipped down to the surface, they are released slowly and circulated with the existing atmosphere. This process continues until the atmosphere is capable of sustaining life for whatever species is intended to live there.

While this is taking place, mining operations will be doing an initial stripping of the planet's crust in order to establish an foundation for the ecumenopolis and to harvest the resources necessary in its construction.

Construction
Construction is done in stages, beginning with space ports spread over the surface area. Around each port cities are developed, providing housing for the labor forces and for the immigrating population. As the initial portion of each area is completed, the construction region is expanded. Lines of transportation are built between regions, and a base layer of development is completed. Once the base layer is done, development continues down into the planet's depths and up into the air.

Population
Population varies depending on the size of the planet, however average population density is reasonably consistent among world-cities, so total population can be estimated as a function of size. Population density averages around 600,000 bodies per cubic kilometer, so multiplying this by the total developed volume yields an estimate of population. Population for an ecumenopolis built on a planet with a radius of 70,000 km would have a developed volume of roughly 4.3 trillion km3, giving it an estimated population of 258.6 quadrillion (1015).

Agriculture
Most of the food has to be produced locally as the food needs of the population are too great to make importing the majority a feasible possibility. Because of the inefficiency of classic livestock and plant-matter based agriculture, the components of foodstuffs are largely made through Direct Production.

Direct Production
Large-scale production is also done directly, recreating the same biological processes that are done by livestock on a larger scale. Direct production involves taking raw organic compounds and converting them into the basic biological nutrients necessary to sustain life. The production of carbohydrates from water and a carbon source, usually carbon-dioxide gas, is done using artificial chlorophyll and ultraviolet radiation.

Waste Management
Waste management is done through a rigorous system of recycling and reuse. All waste is collected and centralized and organic waste is separated from inorganic waste. Organic waste is then reduced to raw material for agricultural production and inorganic waste is reduced to raw material for industrial production.

Collection
Waste collection is centralized and automated. All private domiciles are supplied with automated waste disposal systems, and public areas have regularly spaced waste disposal units. Collected waste is transported to waste management facilities where it is sorted by chemical composition and the then alchemically reduced. The resulting raw materials are then shipped to production warehouses for storage and later use.

Alchemical Reduction
To ensure maximum return on waste recycling, anything that cannon be reused in its current form is alchemically reduced to its most basic, stable form.

Solar Harvesting
Stellar Energy Harvesting is the largest source of energy for an ecumenopolis, usually accounting for more than 60% of an ecumenopolis' energy production. Because of the localized nature of the consumption, Direct Energy Transmission can be used rather than Electrochemical Storage.

Local Energy Generation
Localized energy needs are met with Fusion Reactors, which can be fueled with hydrogen and helium harvested from gas giants in the system.

Other Sources
In rare cases, geothermal and other terrestrial energy sources can be harvested to compensate for energy needs.