Industrial Space Station Classification System

I.S.S.C.S

The Industrial Space Station Classification System, or ISSCS for short, is a standardized classification system put in place by the Terran Mandate pre-Silence and is still utilized today. The classification system does not inherently refer to a station's mass; a common misconception among spacers. Instead the ISSCS is a reference to an industrial station's efficiency, crew amenities and self-sustainability.
The term "Industrial" in this context implies any station which provides a public good or commodity used for the general infrastructural framework of a system or society. Mining, Prison and Refueling stations are the most common examples of industrial stations in this context, though they are not the only stations that meet this definition.
Class-I: Class one stations are the cheapest to build, but generally not the most efficient. Usually employed in Asteroid belts for mining purposes, they have no amenities for their crew and require constant supplies of air, water, energy and food. It is not uncommon for a mining project to have a network of Class-I stations where the miners work with a central Class-II or Class-III station that provides housing for the miners and storage for the mined goods.
Class-II: Class two stations are separate from Class one's by their provision of living quarters for the station's operational staff. They posses housing, hygienic and medical facilities for the staff, but like class ones require constant supplication of oxygen, food, water and energy.
Class-III: Class three stations are by far the most common classification. Class three stations have full amenity suites for their operational staff including housing, medical, recreational and hygienic facilities. They have their own supply of oxygen and CO₂ scrubbers that filter the air and they possess water reclamation facilities. Both of these services require occasional resupply, but can sustain the station for periods of months between resupply shipments.
Class-IV: Class four stations are the first classification approaching self-sustainability. They feature all of the same amenities present in the previous class, and have more robust oxygen and water systems capable of going up to a year or more without needing to be resupplied. Generally they have hydroponics gardens where vegetables and herbs can be grown, as well as protein processing plants capable of producing meat like food productions for the staff. Class four's are also the first classification level come equipped with full docking facilities for ships including discharging facilities and repair bays.
Class-V: Class five stations are orbital cities. The rarest by a wide margin (the Rabian Delta currently only has four Class-V stations) these stations boast full habitation rings with gardens, shops restaurants and theaters all for the use of the operational staff and docking vessels. They possess massive hydroponic facilities capable of growing food and herbs for up to ten years without requiring resupply and they have live animal levels where real animal byproducts such as meat, eggs, milk, etc. can be supplied (although at a premium cost) in supplement to protein products manufactured on the station.