Fiction:Nivenian Empire/Nivenia Diffuse Habitat Swarm

Mortal Engines IN SPAAAACE! (and what has essentially become a paper on habitat design)

The "small habitat" component of the Dyson swarm around the Nivenia System is quickly becoming one of the most important parts of the Nivenian Empire, though they have never been particularly unified with each other or the Nivenian Empire - each habitat is almost its own nation, and some of them are very small indeed. While a few percent of these are standard models constructed by the Megastructural Construction Corporation, nearly fifteen percent are heavily modified Megastructural Construction Corporation, almost unrecognizable from the originals, and over eighty percent are either made by small manufacturers, "singletons" made by small communities with help from various contractors, or, most commonly, heavily improvised models made by small communities without extensive contractor assistance. While this part of the Nivenian Empire is comparatively mass- and energy- poor, as they harvest energy from the star after the ringworlds and other megastructures take their cut, and sometimes have to make do with the waste heat from those megastructures, they at the same time have comparatively much lower costs of living than most other places, and are typically beyond the reach of law enforcement, and host to may of the less savoury elements of the Nivenian Empire.

Location and Politics

This loose, disorganized component of the Nivenian Empire exists in the Nivenia System, with much of it clustered in a rough sphere outside the orbit of Nivenia A6, and the rest largely in a loose disk continuously leading from the outside of the orbit of Nivenia A6 to a distance of about 50 AU from Nivenia A. As it is a loose, disorganized component, no Imperial-sanctioned regional government exists, as extremely few single habitats are large enough to qualify with most in the swarm having under a hundred thousand in total population, and most in the swarm living in habitats with populations less than a hundred million - a far cry from the twenty billion required for "Minor Habitat" designation and full incorporation into the politics and governance off the Nivenian Empire. However, as if simply to beef up their population numbers (as if this was needed - it really is not), even the habitats that are not technically part of the Empire's domain are counted. As for the less than five thousand habitats large enough to be "minor stations," they typically dislike each other too much to ever support any sort of Nivenian Imperial control over more than one habitat at a time, making the region impossible to effectively police, even when the large habitats are being relatively cooperative.

Additionally, no one enters the region with the swarm in it unless they have to, or can travel through at high speed, due to the presence of the strange horrors that are a-viruses. A-viruses, or artificial viruses, are the natural result of a culture that developed interplanetary spaceflight long before computer networks - no effort to create a system-spanning computer network could be possible (due to lightspeed delays of hours or days), so nothing similar to the terran internet ever formed, even after computers grew to be as powerful as terran computers were in the 1990s. So, instead of purely electronic viruses forming, viruses much more like biological viruses were created - first as electronic weapons, and slowly evolving a life of their own afterwards. These a-viruses are probes typically in the ten-to-ten-thousand-kilogram range using solar energy and relatively low-thrust chemical rockets to power and maneuver themselves, thus lacking the highly-visible flare of more common torch drives. These probes attach to habitats, burrow into the hull, connect with their internal networks, and force onboard manufacturing bays to create new probes - as many as possible. While the first probes were designed to be built with cores made from precious materials (so the nivenians who built them could get rich quickly), most have lost this feature due to their equivalent of natural selection, as it is detrimental to the delta-V of these probes.

History

The Nivenia Diffuse Habitat Swarm has never been a unifying structure, just a loose category of similar objects. Its beginnings were in the sixth century BNE, though it is hard to tell exactly when, since most of the paper records of the time have since fallen victim to decay. In any case, unaffiliated habitats began to appear during that time period, not affecting history considerably, and generally keeping to themselves. This group grew with the rest of the Nivenian population, making up about a percent during most of its history - until the problem of living space began to need creative solutions.

By about 110 BNE, efforts were beginning to focus on the construction of the ringworlds around Nivenia A - as the final two centuries of dyson englobement were beginning. As the first ringworld would take a significant amount of time to build compared to the population growth rate, there were a couple of years when it was economically advantageous to construct solar- or fusion- powered O'Neill-type habitats in direct orbit of Nivenia A. Although this was largely a passing phase, similar phases began to occur periodically whenever the current ringworlds has finished being bought out and before the next was built.

Due to these jumps in feasibility, the population of the Nivenia Diffuse Habitat Swarm was up to around 4% of the total population of the Nivenian Empire by the time first contact was made with an alien race. However, the Nivenia Diffuse Habitat Swarm would recieve its biggest boost yet at the end of 41 NE when the Megastructural Construction Corporation began its new plan to limit ringworld production in a roundabout attempt to raise profits, as that created a much higher demand for land, making construction of O'Neill cylinders and similar objects in direct orbit of Nivenia A become feasible again.

Composition

The composition of the Nivenia Diffuse Habitat Swarm resembles the microbiome of a planet more than anything else, with the equivalents of bacteria, archea, eukaryotes, simple multicellular life, and viruses harvesting free-floating resources and each other. These free-floating resources include solar energy, asteroids, and hydrogen fusion reactors, which serve a function similar to chloroplasts in eukaryotic cells. Habitats harvesting each other to gain matter, energy collection methods, and higher populations are also relatively common.

Habitats

Minimalist Habitats

The smallest nominally self-sufficient habitats, these are distinguished by only being self-sufficient in the short term - they cannot support populations large enough to have sizable genetic diversity, so there must be a method of exchanging population, even if the habitats could survive for many decades without this luxury. For nivenians, the limit to genetic diversity is around 150, at least if strong anti-inbreeding cultural measures are in place. Thus, the dividing line between "minimalist habitats" and "small habitats" is usually put at a maximum population capacity of 150.

While theoretical habitats with just a single person could theoretically exist with good automation, the automation required is not known by the Nivenian Empire to enough of a depth to make this possible. As such, the minimum crew size of a functioning habitat is about ten, due to the need for various task specializations. While this can sometimes be lowered to as low as two, the vast majority of minimalist habitats are designed for more than ten nivenians to occupy.

These habitats are too small to consume other habitats, or have much in the way of weapons, and as such usually derive energy from concentrated solar power arrays and derive replacement mass from extremely small asteroids. Most use ion or plasma propulsion, powered by solar energy, and using oxygen derived from the rock as propellant.

Typically, the most potent weapons available to these habitats are small-caliber machine guns and low-yield chemical grenade launchers, which create a simple-yet-potent defense to hazards such as low-importance pirates and thieves, a-viruses, and other minimalist habitats. However, these defenses are nigh-useless against larger habitats, which is where the speed of minimalist habitats becomes their advantage.

Common Components

As these are the smallest possible habitats, their components are rather limited, but usually applicaple to all habitats, even the ones billions of times larger.

The main component of any habitat is the rotation drum - the structure that has to both hold in an atmosphere, and spin to provide artificial gravity. Although many of these at the minimalist habitat scale look nothing like those much larger, the basic premise is the same - centrifugal forces can be used to create gravity by rotation.

Life support, however, is not just about pressurization. Water and air are also important, with the former typically being processes in a large plumbing system with reverse-osmosis filters, and the latter actually consisting of two separate problems - oxygen generation and carbon dioxide removal. Three processes exist for the second, which is the most urgent should systems fail. The first of these processes, only viable for minimalist habitats and simple habitats, is to just keep a large stockpile of a material like calcium oxide, which is capable of forming calcium carbonate when exposed to carbon dioxide, thus sequestering it. The second method is one of the most commonly used on spaceships, but is inferior to the third method in the long term - carbon dioxide electrolysis. Under this method the air is pressurized to several megapascals, causing the carbon dioxide to rain out as a liquid. It can then be mixed with some salts to provide carrier ions for conductivity, and can then be electrolysed into carbon (in the form of graphite powder) and oxygen gas (thus preforming the secondary function of replenishing oxygen supplies). While the most efficient method energy-wise, it produces carbon as a waste product, which will begin to accumulate, and is not easy to reuse.

The most elegant solution to carbon dioxide removal also solves the problem of sustainable food growth - hydroponic and algae farming. This method uses plant life to convert carbon dioxide and sewage into food and oxygen gas, solving several problems at once. As such, it is the primary method employed by habitats of all sizes in life support, and is used widely throughout the Nivenian Empire as well. Necessary vitamins are sometimes not easily available, though, so those are typically grown in bacterial vats, or just chemically synthesized in some cases.

There is also the rocket engine, or engines as the case often is. While minimalist habitats can only afford to buy and repair chemical, ion, and sometimes plasma rockets, other habitats can use more advanced methods of propulsion. However, for almost all habitats their maximum acceleration is below 0.1 meters per second squared when operating their main engines (smaller habitats can only afford low-thrust devices, and larger ones cannot make full use of high-thrust engines due to the development of higher stresses in larger habitats), although minimalist habitats present a partial exception with auxiliary chemical rockets for emergency use.

All habitats must have sources of matter and energy, and thus need materials processing centers and reactors. While for the smallest habitats trade is minimal, and recycling much more efficient (due to their limited financial options), waste material still needs to be repurposed into usable products. Destruction and disassembly is almost always done with smelters, centrifuges, composting, and chemical extractions, while construction typically entails a combination of 3D-printing for simple components and creation by artisans in smaller habitats, while much more energy and labour efficient mass-manufacturing methods are used in larger ones. This mass can come from a range of sources, from asteroids to space dust to derelict megastructures to pre-ordered parts shipped from manufacturing facilities in the Nivenian Empire proper, in order of usability. However, a large percentage of larger habitats simply pull in and eat smaller habitats for materials, which is a brutal, if effective, strategy.

Another mass-related component on all habitats is the docking bay - for transportation of packages, produced goods, and people to and from the habitat. For the smallest minimalist habitats this may be nothing more than two or three standard 1.5-meter docking rings, but in larger minimalist habitats a variety of docking ports and clamps are usually available, sometimes even with a small enclosed docking bay attached. For larger stations the significance of the docking bay grows polynomially, with some of the largest habitats having entire economies dedicated to importing and exporting goods.

As for energy, habitats have a few available options, depending on their size. Any energy system needs a heat input at a higher temperature, and a heat output at a lower temperature. One option available to all habitats, and also conveniently scalable, is the option of solar energy. As most of this is in the vacuum ultraviolet and X-ray bands of the electromagnetic spectrum, properly-designed solar panels of low technology level are actually reasonably efficient in the special conditions around Nivenia A in particular, however at the distance of the swarm, solar energy is scarce, and it would be lucky to get more than about twenty or thirty watts per square meter of panel, making them a mediocre option at best, but one available to everyone. Due to this low yield, most solar-powered habitats use thin aluminum foil for mirrors to build Fresnel lenses designed to focus the light onto a much smaller solar farm - concentrated solar power. Other sources of energy are more complicated, and can only be used by habitats much larger than minimalist ones.

Finally, almost all habitats have weapons systems, ranging from machine guns to fusion missiles, and from predominantly demilitarized autotrophic habitats to the most aggressive and weaponized heterotrophs.

Statistics

Size range	Population capacity	Approximate exterior size of habitat	Habitable area	Approximate mass	Power consumption	Non-engine matter consumption	Engines
Small	10	20 m	800 m^2	500 Mg	600 kW (concentrated solar)	100 kg/yr (misc. parts)	Ion rockets
Medium	40	35 m	4000 m^2	2 Gg	2400 kW (concentrated solar)	800 kg/yr (misc. parts)	Ion rockets
Large	150	60 m	2 hm^2	7.5 Gg	9 MW (concentrated solar)	6000 kg/yr (misc. parts)	Ion or Plasma rockets

As these are extremely simple structures, their options with regard to many of the parameters listed above are notably different than those of larger habitats. For example, these habitats have the relatively rare property of being entirely filled with occupied space, resembling a building or small spaceship more than a rotating small world. This leads to the size of these objects being proportional to the cube root of population, unlike the square root relationship seen in systems constrained by waste heat emission. These habitats are also small enough for chemical rockets to feasibly be used to provide high accelerations in emergency situations (something larger structures would have trouble with), and are too small to afford more efficient power generation systems, like nuclear fission, being instead limited to solar energy. These habitats, like most, have energy consumption requirements and masses proportional to their populations, but their mass intake is instead proportional to the population to the power of three halves, something regarded by most as a side effect of increased commerce and deliveries instead of decreased efficiency.

Simple Habitats

These habitats are the smallest habitats theoretically individually capable of replicating in both material and population over sufficiently long timescales. Using the microbiome analogy, if the minimalist habitats were comparable to ultramicrobacteria[1] in the Nivenia Diffuse Habitat Swarm, the simple habitats would be similar to more normal prokaryotes, with a more well-rounded and robust structure, and a much higher complexity and redundancy than smaller units. The academic cutoff between this category and "true" O'Neill-Type habitats is typically viewed as the population capacity required for sustained proton fusion, at a population capacity of around twenty thousand.

While these habitats are too small to routinely consume smaller habitats, some instances of a relatively large simple habitat consuming a relatively large minimalist habitat have been recorded. The reason why instances like this have been rare is less because of the inability of these habitats to consume smaller ones, and more because of the tendency of minimalist habitats to have emergency high-thrust chemical rocket engines on standby - the only minimalist habitats that have a chance of falling to a simple habitat are the larger ones with no emergency chemical rockets, typically while their ion or plasma rockets are being repaired.

Typically, the most potent weapons available to these habitats are drones of sizes comparable to sports balls all the way up to fighter-sized drones in some cases, rocket and missile launchers, and sometimes nuclear fission or fusion bombs in the kiloton range for particularly well-armed habitats. However, these defenses are nigh-useless against larger habitats, encounters with which typically lead to either surrender and consumption or the usage of higher acceleration tolerances to escape.

Common Components

In addition to the components previously listed, simple habitats contain very few new components. However, their complexity comes largely from the improvement of previous components with longer supply chains, economies of scale, and more purchase options for those components.

One of the largest improvements seen at this level is the drastic increase in the complexity of the docking bay due to increases in both total trade and trade per capita. At this scale the docking bay usually requires at least several full-time employees, tasked with managing the comings and goings of ships, and overseeing an area capable of holding dozens of ships of more inside the station. On larger habitats of this type, the docking bay can rival the ports of small cities, with hundreds of employees moving dozens of ships on and off the station per day.

Although these habitats are too small to sustain viable proton fusion, thorium / uranium / plutonium fission is an option for nearly all of these habitats, and deuterium fusion an option for larger ones. Mass is also derived mainly from asteroids when needed in bulk, but ordered from the rest of the Nivenian Empire when specialized or maintenance-related components are needed.

It should also be noted that simple habitats are large enough to have multiple smaller habitat drums, instead of one large one, without great losses to efficiency. After the habitats with only a single drum, by far the most common number is two, as two-drum habitats can set their two drums into a counterrotating state, where the total angular momentum of the structure is zero. This makes it possible to speed up or slow down the habitat drums' rate of spin without significant fuel expenditure (as would be required to change the angular momentum with conventional rocket engines), or to change the orientation of the entire habitat by only using reaction wheels, and without falling victim to drum procession during the procedure, which can sometimes tear apart an entire single-drum habitat if it is not spun down beforehand. Understandably, this greatly increases the rotational agility of habitats with two drums, making them harder to hit and easier to maneuver. While this can not make up for the low-thrust of their engines, this does make double-drum simple habitats hard enough to catch in relation to their single-drum brethren to be some of the safest relatively small habitats to reside within.

Statistics

Size range	Population capacity	Approximate exterior size of habitat	Habitable area	Approximate mass	Power consumption	Non-engine matter consumption	Engines
Small	500	90 m	7 hm^2	25 Gg	50 MW (concentrated solar or nuclear fission)	25 Mg/yr (misc. parts)	Ion or Plasma rockets
Medium	4000	250 m	60 hm^2	200 Gg	400 MW (concentrated solar or nuclear fission)	400 Mg/yr (misc. parts)	Ion or Plasma rockets
Large	20000	600 m	3 km^2	1 Tg	2 GW (concentrated solar or deuterium fusion)	5 Gg/yr (misc. parts)	Ion or Plasma rockets

These habitats have gotten large enough to deal with the issues of waste heat, and thus appear very different both statistically and literally than minimalist habitats. Statistically, the size of these objects is proportional to the square root of population, signifying a waste heat emission and minimum surface area constraint. Their appearance on the inside is an odd hybrid of the typical single-floor "rotating world" design and a filled-in volume, with a thick, multi-floor shell surrounding a central region typically used for storage or a reactor.

While these habitats have similar population-to-mass and population-to-energy ratios as most others, and no longer have the capability to preform high-thrust burns using chemical fuels in emergencies, they do continue the trend of higher populations causing more commerce per capita, and thus a higher material turnover rate when compared to the total mass.

O'Neill-Type Habitats

Continuing the microbiome analogy, O'Neill-Type habitats would be analogous to small- and medium- sized Eukaryotes, with complex internal structures and sub-components, a centralized authority, more available niches, and the ability to consume smaller habitats routinely and preform the equivalent of photosynthesis in this analogy, proton fusion, efficiently. The cut-off between these and the "Super-O'Neill Habitats" is widely stated to be administrative, as Super-O'Neill habitats require a much more complex governmental system to function properly, with their higher populations. The population cutoff is usually given at twenty million.

These habitats are large enough to include the primary tool of habitat consumption, magnetic coils. By activating a magnetic coil near a smaller habitats, the smaller habitat is pulled into center of the coil for storage much faster than can be compensated using the Ion or Plasma rockets of the smaller habitat. Some habitats gain energy and matter through this method exclusively, and usually wind up with hundreds of low-yield generators and solar farms collectively powering a station that gets repaired from the pieces of destroyed smaller habitats.

Other habitats use gigantic proton fusion reactors, which are analogous to chloroplasts in cells, to power themselves, and attach themselves to large asteroids to slowly mine for use as materials for replacement components, similar to algae. This type of habitat faces completely different challenges than the "heterotrophic" kind, and as such the two categories are almost two different kinds of habitat altogether, just at the same size range. For example, heterotrophic habitats need large-scale rocket engines to provide thrust to chase after smaller habitats, magnetic coils to pull them in, docking bays to connect with them, and disassembly facilities to take them apart, while "autotrophic" habitats need fusion reactor complexes, large amounts of radiator panels, heavy-duty smelting facilities, and mining equipment, without needing nearly as many engines or docking bays.

O'Neill-Type habitats can afford much fancier equipment on all fronts than smaller designs, as they are able to get bulk discounts on many products, and need fewer of some of them per unit population or mass. Two examples of this are nuclear fusion rockets (essential for high-thrust, high-efficiency spaceflight) and nuclear missiles, both common on O'Neill-Type habitat, but not on smaller ones, leading to paradoxically higher acceleration in some cases than simple habitats. Many of these habitats also have substantial onboard weapons systems, usually enough to indisputably win against anything smaller.

Common components

In addition to the components previously listed, O'Neill-Type habitats have an assortment of new components available to them, listed below.

O'Neill-Type habitats typically are much more complex than the three-part design of most smaller habitats (a drum, a reactor/solar farm, and an engine component), and have multiple different specialized facilities (either interior or exterior, which preform functions to greatly enhance the productivity and efficiency of the habitat through economies of scale. In addition to the obvious advantages of dedicated specialized areas, these habitats are large enough for multiple cohesive communities to form inside the habitats, which makes administration much more involved than in smaller habitats. Some of the various sub-habitat components commonly found are listed below.

First a component almost all O'Neill-Type habitats have - Command and Control (commonly referred to as "CNC"). Command and Control serves a similar role to the nucleus in a cell, regulating large-scale governance, creating interior laws, and all exterior diplomatic interaction, in addition to controlling weapons systems, and acting as a hub for instruction manuals and bureaucratic oversight. This component usually takes the form of a smaller, yet faster-spinning habitat located in the rough center of the main habitat drum - well-connected to the rest of the habitat, and well-protected from any attacks.

Another component almost all O'Neill-Type habitats have is the manufacturing bay. Typically manifested as a rotating plate attached to the exterior of the station, this bay allows for the mass-manufacture of many different things needed for the habitat, with different levels of centrifugal gravity available for use in manufacturing different products. This component is typically the workplace of a large fraction of the habitat's population, and is analogous to the rough endoplasmic reticulum in cells.

Analogous to the smooth endoplasmic reticulum and golgi apparatus in cells would be the resource and component transportation systems and warehouse units commonly found on O'Neill-Type habitats. Transportation systems tend to cable-based, and tend to be built and used on a non-rotating superstructure around the drum of the habitat, linking at the rotation axis with a "main cable" designed to transport materials along the rotation axis for easy access by both the manufacturing bay and the habitat itself. Warehouses tend to come in two types - the ones on the exterior of the habitat, used for not-particularly valuable goods, and those that make good radiation shielding, and those on the interior of the habitat for more valuable and sensitive items.

Additionally, sections of the station exist for dismantling equipment as well. The importance of this depends strongly on the type of habitat, with autotrophic habitats only needing minimal amounts of these areas, and heterotrophic habitats typically needing to devote over ten percent of their population to this task. These sections are the equivalent of lysosomes in cells, and in heterotrophic habitats provide most of the mass and energy needed to preform maintenance and grow the habitat.

In heterotrophic habitats in particular, another critical component is the acquisition bay - a component used for the acquisition of smaller habitats for disassembly and incorporation. This component is typically connected to the magnetic coils used to pull in smaller habitats against their ion or plasma rockets, which are low-acceleration devices. This component is usually located either at one end of the rotating habitat drum, adjacent to disassembly facilities, or attached to an auxiliary habitat specialized in disassembly for convenience.

In autotrophic habitats, a similarly essential component, and the one which allows then to surpass all autotrophic habitats of smaller classes in efficiency are the proton fusion reactors - devices that create an insanely potent power supply from the most common nuclide in the universe, and thus provide essentially limitless power to these habitats. These reactors are between a few hundred meters and a few kilometers wide, typically in the form of spheres covered with several meters of steel or concrete for radiation shielding with massive fern-shaped radiators attached. These are the equivalent of chloroplasts, as they provide the energy source for these habitats to function.

It should be noted, however, that some of the largest heterotrophic habitats sometimes become effective mixotrophs using proton fusion - if a large heterotrophic O'Neill-Type habitats consumes a smaller autotrophic one, (which does sometimes happen), it can absorb and incorporate the fusion reactor as a secondary power supply, making it much less dependent on outside-sourced rare materials such as actinides, deuterium, or nivenians who know how solar panels actually work, and thus allowing it to keep a larger portion of the salvage than it would otherwise.

Another component of some habitats that can be found across trophic lines is the mining bay - an area, attached to one or multiple asteroids of various sizes, dedicated to extracting and refining minerals from the asteroid. This can substantially alleviate the need for replacement mass, both by providing resources such as iron, aluminum, oxygen, carbon, and water, and by providing an export product other than information for the habitat, allowing for more frequent imports of more complex goods.

One interesting component, equivalent to the flagella or cilia of cells, is the rocket engine. As these habitats have comparatively large budgets, and can take advantage of economies of scale, deuterium fusion rockets are available to almost all of them, and proton fusion rockets to some of the largest ones. However, only heterotrophic O'Neill-Type habitats really have a pressing need for high accelerations, and as such they tend to have at least an order of magnitude more engines and fuel than autotrophic habitats.

Autotrophic Habitats

Size range	Population capacity	Approximate exterior size of habitat	Habitable area	Approximate mass	Power consumption	Non-engine matter consumption	Engines
Small	200000	5 km	50 km^2	50 Tg	20 GW (proton fusion)	100 Gg/yr (trade)	Largely stationary
Medium	2 Million	15 km	500 km^2	500 Tg	200 GW (proton fusion)	2.5 Tg/yr (trade)	Largely stationary
Large	20 Million	50 km	5000 km^2	5 Pg	2 TW (proton fusion)	50 Tg/yr (trade)	Largely stationary

Heterotrophic Habitats

Size range	Population capacity	Approximate exterior size of habitat	Habitable area	Approximate mass	Power consumption	Non-engine matter consumption	Engines
Small	200000	5 km	40 km^2	20 Tg	20 GW (deuterium fusion, nuclear fission, concentrated solar)	500 Gg/yr (consumption)	Deuterium fusion rockets
Medium	2 Million	15 km	400 km^2	200 Tg	200 GW (deuterium fusion, nuclear fission, concentrated solar)	5 Tg/yr (consumption)	Deuterium fusion rockets
Large	20 Million	50 km	4000 km^2	2 Pg	2 TW (deuterium fusion, nuclear fission, concentrated solar, potentially also proton fusion)	50 Tg/yr (consumption)	Deuterium or Proton fusion rockets

O'Neill-Type habitats are significantly impaired by waste heat, and as such their interiors fit the traditional "rotating world" design, with a dense suburban / light urban building composition on most of the surface, and various exterior and interior buildings around the habitat drum. Statistically, they are viewed as example habitats, due to their size being proportional to the square root of their population, their ability to consume other habitats, and their commerce levels per capita increasing further with population.

Interestingly, despite their larger size, they are able to preform high-thrust burns in some instances due to their access to better rocket technology and economies of scale. Energy and matter consumption is also proportional to population with these, but for these habitats commerce becomes much more prevalent than for previous types, with large-scale importing and exporting taking place in some cases, at least for the autotrophs. The heterotrophs, meanwhile, have just as much material flowing in and out, but most of that comes from the consumption of smaller habitats.

Super-O'Neill Habitats

Super-O'Neill habitats are habitats much larger than traditional O'Neill cylinders, either done by attaching dozens or hundreds of otherwise normal O'Neill-type habitats together or by constructing a single (or two in some cases, to provide stability against procession) habitat drums out of extremely strong materials. Interestingly, while many would expect carbon nanotubes and graphene to be the materials of choice due to their strength, their recent invention makes older boron-nitride nanotubes the more common building material.

These habitats fulfill the role that large eukaryotes and extremely simple multicellular organisms would play in the microbiome, to the point where a serious distinction can be made between their respective habitat analogues - large single or double habitat drums for large eukaryotes, and conglomerations of dozens, hundreds, or thousands of habitats for simple multicellular organisms. This makes for four distinct classes of Super-O'Neill habitat, all of which behave very differently, due to the continuing difference between autotrophic and heterotrophic habitats.

The proton fusion reactors from before are still in large use on these habitats, which are more commonly stationary or extremely slow when compared to smaller habitats due to the enormous material stresses caused by the acceleration of extremely large objects. This leads to a bias toward autotrophy, but heterotrophs can use increasingly interesting methods to sneak up on their prey. For one thing, some smaller habitats are either stationary or permanently connected to asteroids, presenting opportunities for larger heterotrophs to consume both the habitat and the asteroid in one large meal (there are of course many logistical problems with this, but those are evaluated more thoroughly in the components section).

Additionally, there is also a class of habitat that does not clearly fit into the definitions of "single or double habitats" or "large-scale conglomerates," instead acting more like a cellular slime mold, where the individual "cells" break up in times of wealth, but conglomerate together when resources must be conserved to form a temporary alliance and take advantage of their mutual benefit in economies of scale, while sacrificing their previous mobility for this newfound efficiency.

These habitats are large enough that a stable completely unitary government is not possible, with sub-divisions such as cities and provinces becoming necessary to maintain stability and order. This is usually done one of three ways - for the conglomerates, either each sub-habitat operates much like a smaller O'Neill-Type sub-habitat individually, but have a loose confederation to determine such things as trading agreements, citizen identification, and outside interaction, or a single sub-habitat (sometimes multiple sub-habitats, but such "cluster" rule is much less common) wields high authority over subordinate sub-habitats, as in a typical empire. For the large single or double habitats, a hierarchical yet democratic structure arranged by component is much more likely, with the docking bay comprising a province, the warehouse complexes comprising a province, the manufacturing bay comprising a province, and so on, with command and control leading the system. Interestingly, while the components are by no means politically equal on the legal stage, they are most of the time extremely similar in political power per capita, with general elections being held in some to determine the staff of command and control, who legislate for the habitat. In others, the highest authority is monarchical, with a single family owning most if not all of the habitat, and leading it accordingly.

The approximate upper limit for this type of habitat is the size at which consideration by the Nivenian Imperial Government begins to become a distinct possibility - at around the population of a typical civilized planet, or small spacefaring empire's homeworld, at 5 billion. While this is not enough to meet the required 20 billion population for a minor station, a population of around 5 billion is close enough that the power dynamics and goals of the habitat must change drastically to compensate for the possibility of formally joining the Nivenian Empire.

The weapons these habitats are able to wield are much closer to actual military-grade weaponry, with high-yield muon-boosted fusion missiles, proton fusion rocket engines, and even actual (small) fleets being able to be wielded, enabling these habitats the rare ability to actually project force to nearby stations. Sufficiently militaristic Super-O'Neill habitats are truly a force to be feared, as they are able to threaten smaller habitats with destruction. This leads to another unconventional strategy for heterotrophic habitats - merely threatening your prey with destruction unless they surrender to assimilation willingly.

Common components

First, it should be noted that all of the components mentioned previously still exist in this case, yet for many of them, their form and structure must be quite different to accommodate the larger size of the habitat they are inside. Nevertheless, some new components exist, which are usually preforming functions which are seen by most other empires as reserved to actual colonized planets - they are nowhere near the nearby Nivenian planets, of course, but a population in the billions allows for much more freedom in technology and resources than one at lower levels.

Due to the large size of these habitats, the habitat drum becomes large enough for the space along the rotational axis to become a vacuum, simply due to the centrifugal force overcoming the repulsive forces of the gas at large distances, meaning that on habitats more than four hundred kilometers wide, the central part of the habitat becomes a vacuum, or close to it. This raises several important concerns, not the least of which is whether the end caps of the habitat are really needed, with a wall along the edges of the cylinder being able to hold in the atmosphere with far less material. As it turns out, removing the end caps creates a very easy target for a-viruses, weapons fire, and raiders, and as such is much less appealing upon investigation.

The transportation systems are perhaps most affected by this. While on smaller habitats a combination of walking and taking elevators to the axis of rotation, and moving from there worked fine, for these extremely large structures, such trips could take literally hours. To combat this, a new system is commonly used in conjunction with an up-scaled version of the system described before (as that method is still more efficient for long trips) - a light-rail[2] system. Light-rail is a kind of urban transit system common in the eighth century BNE, but largely died out when the Autocracy of Northwest Sunside took over the world in the seventh century BNE, due to loosened environmental constraints. Nevertheless, in a large habitat, light-rail become a very useful transit system due to its reliance on electricity, the artificial nature of the habitat, and its comparatively low cost compared to the transport systems found on smaller habitats. For cargo, above-ground conveyor belts, typically suspended hundreds of meters above the outside of the drum, are used instead, with "on-ramps" and "off-ramps" used to load and offload cargo.

Also notable is Command and Control - usually still inside the center of the habitat, where the air is extremely thin or nonexistent. Due to the habitat's larger size, and the need for bureaucratic legislation and organizational structure, one option many take is to have Command and Control balloon in size, becoming itself similar to the O'Neill-Type habitats mentioned before, with populations on the order of one fiftieth of the population of the main habitat. This can lead to the largest Super-O'Neill habitats having Command and Control modules the size of a small Super-O'Neill habitat in extreme cases! However, there is another option, one usually not taken by smaller habitats due to its cost on smaller scales - having multiple Command and Control components. Each one the size of a simple habitat of various sizes, these can then administer the functions of the different provinces/components of the main habitat. The actual administration of the habitat would then reside on the Command and Control module representing the other Command and Control modules. These modules are usually placed in a line along the axis of the habitat, both for defense and for easy access to each other, the main transportation system, and the rest of the habitat. This setup, with a single "macro-CNC" module and multiple "micro-CNC" modules connected along a line, closely resembles the internal structure of some large ciliates, with multiple micronuclei, and a single macronucleus responsible for he day-to-day operation of the cell. Habitats following this method are thus sometimes jokingly called "Stentors."

The manufacturing bay's topological structure must change as well, to accommodate the habitat's new size. While the manufacturing plate from before usually still exists, a new structure begins to emerge. To minimize transit delays between home (generally a pseudo-random location on the inside of the drum), and the workplace, more manufacturing areas are typically constructed in rings a few dozen to a few hundred meters below the surface of the habitat, designed for full-gravity manufacturing of goods, but designed even more so for relative ease of transportation from the surface to the manufacturing rings through vertical elevators. While this system is not by any means perfect, it does provide similar utility to its predecessor on smaller habitats, and is a good way to scale up to larger ones. As a side note, manufacturing on these habitats is not quite as essential as on smaller ones, since volumes of trade have become so high per capita that a single product can theoretically be traded for all necessary supplies.

The acquisition bay is just as important in heterotrophic habitats, but there are usually several major differences. First, quite a few Super-O'Neill habitats are able to put the acquisition bay on the inside of the habitat, underneath an end cap capable of opening in a similar fashion to the Dietrap mouth. The magnetic coils are then typically placed around the end cap to pull in prey. However, a large minority of heterotrophic Super-O'Neill habitats can be classified as herbivorous, as they are specialized to latch onto asteroid-habitat complexes made from autotrophic, stationary habitats. This notably allows the consumption of the asteroid as well as the autotroph.

However, perhaps the most interesting advancement is the emergence of secondary endosymbionts - O'Neill-Type habitats with large numbers of fusion reactors living withing the vacuum area of larger habitats. Essentially, large heterotrophic habitats made a deal with smaller autotrophs - in exchange for providing the heterotroph with energy from their internal proton fusion reactors (which the autotroph would need to build many more of), the autotroph would get to exist inside the habitat drum of the heterotroph, protecting them from predators, raiders, a-viruses, and other environmental concerns. Other reasons for smaller autotrophs to join these habitats include the large assortment of weapons the Super-O'Neill habitats have for defense, the larger volumes of trade that pass through them, and the larger size making their hosts much more influential in the swarm. This creates the odd situation of a habitat containing foreign habitats with their own Command and Control modules, which operate the smaller habitats as if they were tributaries to the main habitat, but not entirely incorporated into the political system.

As far as the rocket engine, most habitats of this scale forgo having a single main engine and instead opt to have dozen, hundreds, or even thousands of smaller blocks of multidirectional thrusters. This switch is due to the low accelerations and huge energy expenditures moving habitats this big would require, and the high utility of control over rotational and vibration motion when compared with full control over translational motion at these scales. Still, some of these habitats are able to exert meaningful thrust (especially the heterotrophs) by mounting hundreds or thousands of smaller engines on a single face of the habitat.

Due to this lack of mobility, mining itself becomes rather different, as the previous system of attaching the mining bay to the habitat only allows for three strategies - eating asteroids the same way habitats could be eaten (which requires high mobility), eating a single, large asteroid over a period of year, decades, or potentially longer, and then slowly meandering to the next (which requires staying still for long periods of time), and simply using magnetic fields (usually salvaged from old ramscoops from fusion drives deemed to be at the end of their life) to attract dust particles for harvesting (which has a very low yield). However, at large sizes, it becomes possible to send out "hauler" vessels, designed to capture nearby asteroids, and slowly drag them back to the main habitat for processing, enabling the main habitat to stay still (while not being entirely constrained) and spend as few resources as possible in acquiring materials. Lastly, trade again comes to the rescue for some habitats, which specialize in manufacturing and secondary industry, and then sell their goods to other habitats or the Nivenian Economy at large in exchange for more raw materials.

Perhaps the most startling feature of habitats this size and above would be the (common, although not ubiquitous) shipyard, an extension of the docking bay (which itself can be as big as a smaller habitat). This area is responsible for constructing and maintaining the combat, ambassadorial, mining, and other fleets owned by the habitat, a daunting proposition for such a large structure. As such, this area can employ thousands to millions, and is usually considered a component in and of itself in the command structure, separate from the main docking bay.

Common components (Conglomerations)

If command structures in non-conglomeration habitats were chaotic, conglomerations are even more so. For one thing, there is a significant difference between obligatory and non-obligatory conglomerations, with obligatory ones containing more specialized habitats with a division-of-labour system that keeps them from being able to separate, and non-obligatory conglomerations having the option to disband if the need (or want) arose. Generally, the political system is not influenced by the type of conglomeration; the type of conglomeration is influenced by the political system.

As an example, the more "hierarchical" regimes (with regards to equality of habitats in the political process, or lack thereof), controlled by a single O'Neill-Type sub-habitat that has established itself as the dominant habitat of the conglomeration (or a more "oligarchic" system, though those are comparatively rare), typically try their hardest to prevent any O'Neill-Type sub-habitats from leaving. This can take the form of bribery and blackmailing towards the leaders of such sub-habitats, or, in cases of abnormal persistence, the form of military coercion using the military arsenal available to them - usually vastly superior to the resources of a single sub-habitat.

With more "democratic" regimes (at least in the sense of the say of each sub-habitat in the politics of the whole) controlling these habitats, the sub-habitats themselves usually have the freedom to come and go as they please, with various degrees of bureaucracy surrounding the process. This is due to the noise a single sub-habitat can make, and the disruptions such a displeased sub-habitat can make in the overall political system - it is usually far easier to just let the offending habitat leave.

It is important to note that some habitats of conglomerate nature have democratic systems that are nevertheless hierarchical in structure, where a single habitat acts as the body of a unitary government, or an autocratic conglomerate with a nonetheless confederate national structure, where each petty dictator ruling over a single sub-habitat sends a representative to a meeting place to work out legislation and management. In other words, the democratic-autocratic and unitary-federal-confederate political axes are completely perpendicular.

Regarding sub-habitat superstructures, like many of the exterior components mentioned previously, one of two things is usually done. If the habitat is relatively strict about entering and leaving, with a relatively unitary regime, then a centralized planning committee is usually used for designing a new superstructure spanning all of the habitats in the system. This allows for far greater efficiency, on par with the non-conglomeration Super-O'Neill habitats, at the cost of adaptability and ease of assimilation into and dismissal from the system. If the habitat has a relatively confederate system where individual habitats are free to come and go as they please, then a secondary superstructure may be constructed to modularly link to the superstructures around the individual sub-habitats. This limits efficiency to levels more similar to the smaller habitats themselves, but there is still a small boost in efficiency compared to the efficiency of a detached sub-habitat, due to trade between the sub-habitat using the secondary superstructure, and the ability to assimilate or dismiss quickly is retained. Visually, the secondary superstructure tends to appear as multiple winding ad-hoc roller-coasters connecting the superstructures of each individual habitat. Of course, governmental systems in-between these two extremes tend to have similarly intermediate transport systems, potentially with centrally planned components and more ad-hoc components (although that can create "tiers" of membership in the conglomeration in some cases, and as such is rarely used), or, more commonly, each sub-habitat is given the freedom to optimize its section of an originally ad-hoc system if it operates under certain constraints. This leads to a partially optimized system with each sub-habitat having a specialized portion of the transit system to call its own.

Propulsion in conglomerations is interesting. While on the surface they are even less resistant to high accelerations than the non-conglomeration Super-O'Neill habitats, they are actually much better at accelerating due to an interesting quirk of their design - being made out of huge numbers of smaller habitats, each habitat can contain its own propulsion system. This allows for quick, fast acceleration, on par with the smaller O'Neill-class habitats, while the maximum angular momentum, and thus turning speed, is still limited by the inter-sub-habitat connections. This still makes heterotrophy much more common among conglomerations than among non-conglomerate Super-O'Neill habitats due to their quicker accelerations.

With more heterotrophy, acquisition bays are just as important, if not more so, to the survival of conglomerate Super-O'Neill habitats. As with the previous components discussed, they tend towards two main extremes, a centralized and decentralized version, each with various pros and cons, and with a wide spectrum of intermediate versions possible between the extremes. In the centralized case, a gigantic acquisition bay is mounted on the front of the structure, with massive magnetic coils being used to draw in prey, and a huge disassembly yard attached to the back of the coil to disassemble prey and use the parts for construction, reinforcement, trading, or maintenance. This approach works much like the approach of the O'Neill-Type habitats, and works just as well due to the speed of these models. Additionally, heterotrophic conglomerations have enough space and capital inside to be powered by proton fusion reactors and engines, even if not completely autotrophic. In the decentralized case, each sub-habitat has its own acquisition bay, complete with magnetic coils and disassembly yards. This comes with the advantage of being able to capture and digest multiple smaller habitats at once, instead of lust one large habitat, and being able to consume habitats from almost any angle. However, this comes at the cost of making the disassembly less efficient due to economies of scale, and making hunting more costly - unless a swarm of smaller habitats can be found, or a number of them stuck to an asteroid or other massive body, consuming a single habitat still requires the same amount of fuel to be used in the chase, and the habitats available for consumption are quite a bit smaller.

Autotrophic conglomerations are actually not that different from autotrophic O'Neill-Type habitats, as almost all of the sub-habitats contain their own proton fusion reactors to power the whole. The centralization on this component is more bureaucratic than physical, with the proton fusion reactors being either in the same quantity and location in each sub-habitat, or the proton fusion reactors placed pseudo-randomly inside the sub-habitats, leading to a less "crystalline" structure.

Autotrophic Habitats

Size range	Population capacity	Approximate exterior size of habitat	Habitable area	Approximate mass	Power consumption	Non-engine matter consumption	Engines
Small	120 Million	120 km	30000 km^2	30 Pg	12 TW (proton fusion)	300 Tg/yr (trade)	Largely stationary
Medium	800 Million	320 km	160000 km^2	200 Pg	80 TW (proton fusion)	2 Pg/yr (trade)	Largely stationary
Large	5 Billion	800 km	1.25 Mm^2	1.25 Eg	500 TW (proton fusion)	12.5 Pg/yr (trade)	Largely stationary

Heterotrophic Habitats

Size range	Population capacity	Approximate exterior size of habitat	Habitable area	Approximate mass	Power consumption	Non-engine matter consumption	Engines
Small	120 Million	120 km	24000 km^2	12 Pg	12 TW (deuterium fusion, nuclear fission, concentrated solar, usually also some proton fusion)	300 Tg/yr (consumption)	Deuterium or Proton fusion rockets
Medium	800 Million	320 km	160000 km^2	80 Pg	80 TW (deuterium fusion, nuclear fission, concentrated solar, usually also some proton fusion)	2 Pg/yr (consumption)	Proton fusion rockets
Large	5 Billion	800 km	1 Mm^2	500 Pg	500 TW (deuterium fusion, nuclear fission, concentrated solar, usually also some proton fusion)	12.5 Pg/yr (consumption)	Proton fusion rockets

Autotrophic Conglomeration Habitats

Size range	Population capacity	Approximate exterior size of habitat	Habitable area	Approximate mass	Power consumption	Non-engine matter consumption	Engines
Small	120 Million	240 km	30000 km^2	45 Pg	12 TW (proton fusion)	600 Tg/yr (trade)	Minimal Deuterium or Proton fusion rockets
Medium	800 Million	640 km	160000 km^2	300 Pg	80 TW (proton fusion)	4 Pg/yr (trade)	Minimal Deuterium or Proton fusion rockets
Large	5 Billion	1600 km	1.25 Mm^2	1.75 Eg	500 TW (proton fusion)	25 Pg/yr (trade)	Minimal Deuterium or Proton fusion rockets

Heterotrophic Conglomeration Habitats

Size range	Population capacity	Approximate exterior size of habitat	Habitable area	Approximate mass	Power consumption	Non-engine matter consumption	Engines
Small	120 Million	240 km	24000 km^2	18 Pg	12 TW (deuterium fusion, nuclear fission, concentrated solar, usually also some proton fusion)	600 Tg/yr (consumption)	Deuterium or Proton fusion rockets (decentralized)
Medium	800 Million	640 km	160000 km^2	120 Pg	80 TW (deuterium fusion, nuclear fission, concentrated solar, usually also some proton fusion)	4 Pg/yr (consumption)	Deuterium or Proton fusion rockets (decentralized)
Large	5 Billion	1600 km	1 Mm^2	750 Pg	500 TW (deuterium fusion, nuclear fission, concentrated solar, usually also some proton fusion)	25 Pg/yr (consumption)	Deuterium or Proton fusion rockets (decentralized)

Whether conglomerate or non-conglomerate, Super-O'Neill habitats appear similar to O'Neill-Type habitats on the inside, however statistically they are quite different, as most parameters now increase linearly with population (while radius increases with the square root of population.). However, conglomerates are both physically larger, heavier, and trade/consume/exchange more mass per unit population. While it may seem like they are less efficient from these statistics, their financial efficiency is actually similar to smaller habitats, due to the decreased cost of materials purchased in bulk balancing out the increased cost of the support structure and overhead required to turn dozens or hundreds of disparate habitats into a cohesive unit.

Larger Structures

Larger than even the Super-O'Neill habitats are the habitats large enough to be politically relevant outside the Nivenia Diffuse Habitat Swarm. These behemoths have the populations of entire worlds, are meeting-grounds for peace negotiations between larger corporations and political factions, and their support is powerful enough to be significant in deciding the outcome of political, economic, and especially military conflicts. Although rarely talked about, they were extremely influential in the Third Nivenian War of Reunifications corporate front in the Nivenia System.

These habitats, with populations of above five billion, are almost exclusively conglomerate, mainly due to the near-impossibility of maintaining a single rotating habitat more than 1000 km in size without carbon nanotubes - born nitride nanotubes are no longer sufficiently strong at those scales. As carbon-nanotubes have only been cheaply mass-produced in the Nivenian Empire in any quantity for about two decades, their use in these habitats is not unheard-of, but also not particularly common. However, over the last ten years or so, after the Megastructural Construction Corporation began restricting the construction of habitats to glean more money from customers, the construction of carbon-nanotube and graphene (which is similarly strong, but even harder to manufacture cheaply on sub-planetary scales) habitats, deemed by many a more affordable (and quick) option for expansion, colonization, and homesteading, became more and more common. Although habitats of this nature are still typically put in the Super-O'Neill range, larger and more politically relevant structures are stating to be produced in-bulk.

Structures in the five-to-twenty billion range have a new force applied to their political structure - the possibility of incorporation into the Nivenian Empire. As habitats of over twenty billion are classified as "minor habitats" by the Nivenian Empire, they are eligible for all of the benefits and detriments that full Nivenian Imperial membership includes. For example, full Nivenian member habitats have to abide by the (minimal) Nivenian Imperial constitution, and are able to be accessed by Nivenian law enforcement for the purposes of apprehending criminals. Of course, this is a double-edged sword, as the possibility of criminal apprehension makes these habitats safer, but lessens the commercial success many habitats enjoy as relatively lawless locations. As such, many habitats want to do all that they can to stay under the population threshold at 20 billion, while many others want to do all that they can to get above it, and reap the benefits the Nivenian Empire has to offer. Thus, habitats in this range have a wide variety of interests, and can be much more unpredictable than their size might suggest.

Habitats of these size ranges typically need at least three, and possibly more layers of governance, a change from the two of the Super-O'Neill habitats, and the one of O'Neill-Types and smaller. Thus, their political systems are usually beats in their own right, sometimes even with distinct, large, and even homegrown ethnic groups and ideologies which do not like each other, which can dominate politics in some democratic habitats. In the more authoritarian habitats, large-scale assimilation measures have to be put in place to prevent breakups like this.

Common components

These habitats are gigantic. While some few might exist as single drums, they comprise less than a percent of the population of habitats this size, which makes them outliers to the typical strategies. However, they do deserve a mention, as their proportion is quickly growing now that the Megastructural Construction Corporation is mass-producing McKendree cylinders at at alarming rate. So, it should be noted that these habitats essentially act much like the Super-O'Neill cylinder habitats, just with some political differences to account for the possibility, and for some, the reality, of full Nivenian incorporation.

The politics of these habitats are, even at their best times, complicated. In addition to the greatly exacerbated intercultural and multi-ethnic problems generated by having multiple billions under one government, the habitats become too large for even a two-layer system to work, necessitating three or more layer, which obviously brings its own political issues regarding which layer of government should have what powers. With all of this, as population increases, the amount of backstabbing usually increases as well, with it being lowest in the closely-knit minimalist habitats, but highest in the highly political and divisive largest structures.

Even if one might think that full assimilation into the Nivenian political system might alleviate this, it actually makes it worse due to the larger interests now at stake - politicians, corporation, and even scientists and engineers trying to rack up funding for new ideas as quickly as possible. In any case, habitats over the twenty billion cut-off are some of the most politically cut-throat places in the Empire due to their relative lack of stability due to recent construction and (comparatively) small size.

With the vast scale of these of habitats, new avenues in business and influence begin to open up for them as well. As an example, while smaller habitats are too small and too numerous for mainstream trading firms (those with ships larger than even the Dragon-class Titan, the largest ship mass-produced for the Nivenian Military. Understandably, while a habitat of one billion might not have enough goods of great enough value for traders to stop at, a habitat of ten billion would probably have enough.

Of course, this creates a self-reinforcing cycle where smaller habitats that want to have their stuff sold first ship it to larger habitats, which then wind up with an even greater volume of goods to sell, and leading to being a stop on more trade routes. This makes the larger habitat even more of a good target for traders, and reduces the trading at smaller habitats even further. Thus, it is actually very hard to either gain the ability to trade in bulk (as that requires either diplomacy with thousands of smaller habitats or more, or getting really, really, really big), and even harder to lose the ability (because no one would actually want to, and even if you have shrunk, smaller habitats will keep bringing you their stuff to trade with as long as the traders are present, and the traders will continue to be present as long as the smaller habitats continue bringing their stuff to trade with you). As this trading is usually vastly beneficial to the habitat it is taking part in (as larger volumes of goods can be exported, and the habitat gets to take a cut of the manufacturing done by smaller habitats as a "middleman," becoming a trading hub is a near-universal goal for habitats, though one that only really becomes feasible at populations above about ten billion.

As such, habitats with populations above ten billion tend to be equipped with trading bays, and stock exchanges, as those provide the easiest methods of attracting traders, entrepreneurs, and the rest of the interested economic elite from both other habitats and the Nivenian Empire as a whole. The trading bay is almost always the most visible of the two, as it typically appears like a gigantic protrusion on the superstructure of the habitat - since more habitats of this size are conglomerations, the protrusion typically has specialized sub-habitats of its own, as well. The protrusion contains areas much like the usual docking bay, but instead of being designed for smaller military vessels, mining ships, and smaller trade vessels, the docks are unusually gigantic, and have equipment in place to accommodate moving the kind of shipping containers that weigh over a million metric tons typically used by those gigantic ships. In addition, as most of the cargo transported in space is micro-gravity-tolerant, warehouse sections even larger than the trading ships will also usually exist - both to store imported items until they can be used, and to stockpile exports to load onto some of the even more gargantuan trading ships. The actual habitat section of the trading bay will have multiple uses in almost all cases - absolutely essential is the need to house the dockworkers, as well as the need to house the sizable support economy specialized in providing amenities for them. While not essential, having an extremely expensive lounge for career traders (the ship owners for smaller trading companies, and the ship's economics expert for larger corporations) is par for the course, since having a pleasant environment (and bribes, which although almost necessary, are rarely disclosed) is quite beneficial in raising the trader's opinion of the habitat, leading to your being recommended to other traders.

However, once trading gets this prevalent, a dedicated stock exchange becomes extremely necessary. While most habitats with populations over a million have some form of stock exchange onboard, the stock exchanges on those habitats typically are neither large enough to actually be dedicated affairs that are noteworthy in the overall economy of the habitat, nor do they have adequate representation from corporations located outside of the habitat - those habitats are not important enough for the massive megacorporations of the Nivenian Empire Proper, and corporations operating on other habitats are usually both extremely unstable due to the possibility of the various heterotrophs and a-viruses making the habitat their next meal, and the fact that most independent habitats are hostile and effectively at war with most other independent habitats, at least most of the time. With all of these being deciding factors, it is simply neither necessary nor feasible to have an actual dedicated stock market on most habitats (even if most above a billion would contain independent stock markets superior to those available to humanity in the 21st century). However, this equation changes when the massive self-perpetuating influx of trade begins at around a population of ten billion.

At that time, the larger trading companies begin to take interest in the station, and, as we discussed before, the volume of trade faces a sudden, massive uptick as nearby habitats begin conducting business through the main one. This creates a very different business environment, with massive corporations and large habitats routinely moving trillions of credits' worth of various industrial goods and resources every day. With all of these commodities flowing through the station, having a securities exchange suddenly goes from an interesting novelty for the well-to-do to an absolute necessity for economic growth. Thus, on tens of thousands of habitats, the dedicated stock exchange was born. This structure, located on or around the protrusion that is the trading bay, could be considered part of it, but is considered by most to be important enough economically to be considered on its own - many a billionaire was made in the violently fluctuating stock markets of the Nivenia Diffuse Habitat Swarm, and many a billionaire has fallen from wealth in the same way as well. The stock exchange itself typically takes the form of a decently-sized sub-habitat, modified with massive computers, screens, and ticker-tape dispensers to aid and inform the traders within. Here, the stocks of verious in-habitat, off-habitat, other-habitat, and even ringworld-based or planetside corporations are traded, with stock in the corporations outside the Nivenia Diffuse Habitat Swarm becoming a de facto currency, due to their relative stability when compared to the economy inside the Nivenia Diffuse Habitat Swarm, of which "hostile" might be an uderstatement - due to random destruction of assets, lives, habitats, and thus corporations, most niches are under-filled, and thus while start-ups and even established firms can be expected to grow at astounding rates, they can be destroyed just as easily

Parasitic Objects

A-viruses

A-viruses are some of the most feared objects in the Nivenia Diffuse Habitat Swarm. Originally built as superweapons by some of the largest habitats sometime between 140 BNE and 130 BNE, they were designed to lock on to an enemy habitat, hijack its internal networks, and force the manufacturing bay to build thousands, or even sometimes millions of new probes, exactly like the original. Then, it would either self-destruct the entire habitat using its reactor, releasing the probes and giving them a massive speed boost to search out new victims, or it would just blow the airlocks on the manufacturing bay, which would cripple, but not destroy the habitat.

The manner of attachment, takeover, and spreading is indicative of the A-virus in question's designer's goals in the construction of their project. For example, a rabidly xenophobic and militaristic habit craving more resources would program their probes to destroy whatever habitat they came into contact with, while a more pragmatic heterotroph might just program the probes to disable habitats without killing them entirely, to make them easy targets for consumption. If the reader is wondering at this point why the only examples given seemed like incredibly hostile habitats, that is because it takes an incredibly hostile habitat to construct such superweapons.

The main weakness of these early A-viruses (in more ways then one) was the piece of code that programmed them to not attack their constructors. Of course, Nivenian computers back in 130 BNE were much more primitive than current ones, being the equivalent of terran computers in the 1970s, so this had to be done by having the probes avoid habitats emitting certain radio frequencies, which the parent habitat would emit. The problem with this was that after someone figured out which habitat any specific a-virus came from, they could just emulate that habitat's radio transmissions and not be attacked. Of course, that meant that the viruses would usually only last for a few months at most, infecting a few hundred to a few thousand habitats, and then they would die out as everyone started broadcasting the key radio frequency, the a-viruses ran out of victims, and then died from maintenance issues (As they were expected to reproduce quickly, they were not designed to last more than a couple of years on their own.). While this would have been the case, the first a-viruses were unstable enough that a small minority of second- or third-generation a-viruses were able to shed this capability, and were able to attack habitats broadcasting the signal.

This lead to only this small minority surviving when the rest of the swarm figured out the code to broadcast to prevent hostile takeover by a-viruses. Of course, only a few a-viruses from each "strain" engineered by a habitat that wanted to unleash them on its enemies survived the distribution of the strain's weakness, so no-one really notices for about two decades, a period of time during which tens of thousands of a-viruses were released, and during which "a-virus engineer" actually became a respected profession, instead of its current reputation as a position only an evil scientist would take.

However, the leftovers from each strain were slowly building up during this period, with their finally being significant around 115 BNE, and leading to an event widely known as the a-virus explosion. The a-virus explosion had actually been exponentially growing for a while but it was only around 115 BNE that the exponential growth surpassed the production of the more restrained a-viruses, and the mutant a-viruses became a significant threat to everyone around 110 BNE, becoming the largest cause of catastrophic failure in habitats.

Thus followed the "dark years," a time in which several catastrophes beset the entire swarm at the same time. First was the construction of the ringworld around Nivenia A, which offered a cheaper alternative to habitat construction, and thus stifled the growth of the swarm. But perhaps more importantly was the fact that between around 110 BNE and 100 BNE, the a-viruses wreaked havoc on the swarm, and there was either no good defense against them, or said defense was still under construction. During this period the population of the swarm actually dropped by over twenty percent.

But, thankfully there was an effective defense, which keeps a-viruses from being a problem for most of the more established and alert habitats today - flak artillery. Flak artillery is a weapon that fires explosive shells at objects coming close, and can damage even extremely agile enemies by having the shell explode before impact, blasting out a cloud of high-velocity shrapnel. This cloud then destroys anything it comes into contact with, although it quickly disperses, making the weapon useless at ranges of more than one to a hundred kilometers, depending on the size of the weapon.

Due to this usage of flak artillery, almost all habitats come equipped with them, and the era of a-virus terror is largely over, with the only habitats at risk being the select few who underestimate the danger of a-viruses and skimp out on flak artillery, and (eventually) fall victim to the much lower numbers of a-viruses that currently exist, with those a-viruses only able to survive on the habitats that underestimate the danger. As the lower a-virus numbers get, the more habitats underestimate the risk, and vice versa, this operates as a self-regulating system, not letting the numbers of a-viruses stray too much from equilibrium. They now account for about 4.5% of catastrophic failures.

Components

A-viruses are relatively simple affairs, typically with just the equipment necessary to hijack another habitat and reproduce. Their size is highly variable, typically ranging from one to twenty meters on their longest axis, but typically around two to five meters. They are mostly polyhedral, with icosohedrons being the most common hull configuration, with octohedrons not being far behind them (Due to the structural advantages of triangles, and the need for many separate reaction control thrusters on the corners, these two designs comprised the majority of a-viruses.).

Their interior usually houses a computer hardwired to a specific program to control the a-virus, which is typically a relatively obsolete one, even by Nivenian standards, as almost all a-viruses were designed before 100 BNE. The computer uses a lot of power, sometimes several kilowatts when running, so the main program, which is typically hardwired into the computer with ROM (read-only memory), can only activate when a secondary, much simpler computer turns on the first one. This simpler computer would probably be better described simply as an integrated circuit, due to its less complex task - it simply uses passive radar methods to scan its surroundings every few minutes (as this is low-energy enough that the a-virus' onboard power supply can sustain it for extended periods), and activate the main computer if a target (a habitat of sufficient size to have certain automatic systems installed in the manufacturing bay) is within about one hundred to one thousand kilometers, depending on the a-virus. The main computer than begins its program, and prepares to take control of the habitat and reproduce.

To actually get to the habitat, and to leave the habitat when they are made, a-viruses need rocket engines to move about. Almost all a-viruses use chemical rockets, with mono-propellants being exceedingly common, surpassed only by the liquid hydrogen/liquid oxygen bi-propellant that is much easier to manufacture - a trait needed by a probe looking to manufacture itself using other, unknown facilities. These a-viruses use their rockets, once in range of a victim, to approach the victim and land on its hull.

Here, a-viruses must make a trade-off between attacking the habitat drum of the vehicle and attacking the superstructure. A large minority of a-viruses, typically the more complex ones, opt to land and attack habitat superstructures. While harder to discern, and thus requiring more sensors to locate, larger a-viruses have both more room and more power to run these sensors. The advantage of the superstructure is that it is stationary, and provides easy access to a part of the station less likely to be well-defended. However, it is typically harder on the software side to break in in these locations, so the computer as well must be bulkier to successfully break in automatically. Smaller a-viruses, a majority in fact, tend towards the hull. It is typically much easier to locate than the superstructure, and so is easier to detect, but is also more heavily defended, so smaller a-viruses are more easily able to slip past unnoticed. Once attached, the a-virus must only stay alive long enough to burrow through the outer hull, and connect with the computer system inside to download its malware package, as even if the virus were found and destroyed afterwards, its reproduction cycle would still be underway. The proximity to the computer network's hub also makes breaking in easier on the software side, and more feasible for smaller a-viruses.

The method of entry is perhaps the most versatile out of all a-virus qualities, there are many methods, each with their own pros and cons. Of course, the brute force method is most widely used, where the a-virus just uses magnets to attach themselves to the hull or superstructure of their victim, aims their rockets at the surface, and burns at full throttle to melt through, like a super-overpowered plasma cutter. Of course, this method is detectable in multiple ways, as it is essentially just blasting through a wall, but it only takes seconds, and the a-virus is free to infect the habitat afterwards. Very similar is the less-disruptive, but also less versatile method of using single-use high-power chemical-pumped lasers to cut through their target. While this is extremely quite, and leaves a clean hole for the probe to enter, vastly decreasing the chances of detection, the chance of failure is vastly increased. Due to the nature of chemical laser technology, the lasers need to be pumped by a chemical reaction, which typically cannot be undone except in special, large, facilities, so a botched break-in with chemical lasers could leave the entire probe out of commission. In other instances, a simple electric drill is used. This system is about halfway between the two mentioned above - it is reliable, but not overly so, and it is noisy, but not overly destructive, either. The main advantage of a drill-based system is actually in the construction phase, though. The components required to make chemical lasers, for example, are specialty, and a lot of habitats might not have the materials on-hand at the time of industrial facility hijacking, making the entire operation a dud - obviously undesirable. Thus, the drill, made from little more than steel, has remained a competitive weapon in a-viruses ever since the first ones were released

However, some probes are much sneakier when it comes to their transmission method. Most habitats have airlocks, which typically have outside control panels in case anyone accidentally locks themselves out - having access to the habitat denied is not what one will want to see when their suit's air supply is leaking or they need a gas refill quickly. Thus, there is usually a computer terminal on the outside of the habitat. And of course, where there is an exterior terminal, there are a-viruses that exist to exploit it - here by downloading their programming through the terminal into the interior of the habitat. This method is risky, though, since airlocks are typically well-defended by flak artillery units. Another, equally sneaky type of a-virus is the kind that pretends to be a delivery from the inner system (usually Nivenia Prime, since their components are usually of the highest quality, and thus a prize to any habitat that acquired them), gets hauled inside the docking area, and ported inside the habitat, and then sprouts treads, homes in on the nearest computer terminal, and downloads its package. This method is actually quite common, as pretending to be a package does not usually come with a high risk. Still, a large minority of habitats are scared enough of these machines to undergo routine checks on packages entering to make sure they do not contain malicious content.

Of course, there are also the enumerable a-viruses that just found some creative way to infect habitats, yet are still relatively few in number due to the small number of habitats with a particular weakness that they can exploit. For example, some habitat operating systems have built-in communications protocol that allows some kinds of radio signal to directly write data into the computer, providing an avenue of transmission for any a-viruses within ten thousand kilometers. Others have hardware weaknesses like open fusion reactor spent fuel expulsion ducts that sufficiently-radiation-shielded a-viruses can take advantage of. The possibilities are endless, and so are the possible a-viruses.

Statistics

Size range	Approximate payload capacity (Download speed / Data / RAM)	Approximate size of object	Approximate mass	Power consumption	Detection range	Engines
Small	200 kBits/s / 15 MB / 120 kB	2 m	300 kg	20 W (concentrated solar), 200 kW under emergency conditions (stored chemical energy)	100 km	Chemical Rockets
Medium	1.25 MBits/s / 200 MB / 2 MB	5 m	20 Mg	125 W (concentrated solar), 1.25 MW under emergency conditions (stored chemical energy)	1000 km	Chemical Rockets
Large	5 MBits/s / 1 GB / 10 MB	10 m	150 Mg	500 W (concentrated solar), 5 MW under emergency conditions (stored chemical energy)	10 Mm	Chemical Rockets

A-viruses are interesting, with almost all of their properties, save for their mass, being determined by their surface area, when normally habitats this small (which do not exist in any significant quantity) would have to actively take measure to keep heat in, not be limited by how fast it could be expelled. This interesting relationship is actually due to multiple factors, not the least of which being that everything an a-virus uses to interact with its environment is on its surface.

This provides a stark contrast to actual habitats, in which the maintenance of an economy, a population, and many other energy-utilizing things are the main purpose of the structure. However, for an a-virus, only two things matter - survival and reproduction. On the survival aspect of the problem, the surface area of the a-virus is typically where energy as generated, as solar panels are the only reasonable way for objects of this size to derive energy. On the reproductive side, the surface area is the access point for such implements as cutters, computer data buses, and other devices used to break into and infect a habitat.

Culture

Nivenian Empire General Information History and Government History before 20 NE Nivenian Government, Nivenian Technology (Nivenian Megastructures) Nivenian Military (Nivenian Weapons Systems, Weapons Range) Titans: Hydra-class, Dragon-class Battleships: Griffon-class, Phoenix-class Destroyers: Serpent-class, Pegasus-class, Dragonfly-class Corvettes: Protector-class, Wasp-class Mobile Shipyards: A-type Mobile Shipyard Facility, B-type Mobile Shipyard Facility, C-type Mobile Shipyard Facility Mobile Munitions Planets: Military Mining Platforms: Cargo Transports: Other Demographics of the Nivenian Empire, Astrography of the Nivenian Empire, Nivenian culture Corporations The Megastructural Construction Corporation, MegaSuperUltraCorp Nivenian History after Dekemurios 32, 20 NE Dekemurios 32, 20 NE - Martex 32, 32 NE Dekemurios 32, 20 NE - Neochios 41, 23 NE Neochios 41, 23 NE - Martex 53, 24 NE Neochios 41, 23 NE - Martex 32, 32 NE Martex 32, 32 NE - Martex 32, 32 NE - Dekemurios 55, 33 NE Dekemurios 55, 33 NE - Nivenia Space Core Systems (within 3.2 light-years) Nivenia System Planets and Moons (Primary - Inner System) Brown Dwarf Nivenia AB Planet Nivenia A1 (demolished) Planet Nivenia A2 Planet Nivenia A3 Planet Nivenia A4 Ecumenopolis Nivenia Prime (History) Planet Nivenia A6, Moon Nivenia A6.1, Nivenia A6 Planet Swarm Planet Nivenia A7 (demolished), Moon Nivenia A7.1, and moon Moon Nivenia A7.2 Planets and Moons (Primary - Outer System) Planet Nivenia A8 (demolished), Moon Nivenia A8.1 Planet Nivenia A9 Planet Nivenia A10, and moon Moon Nivenia A10.1 Planet Nivenia A11, and moons Moon Nivenia A11.1 and Moon Nivenia A11.2 Planet Nivenia A12, and moon Moon Nivenia A12.1 Nivenia Diffuse Habitat Swarm Planets and Moons (Secondary) Planet Nivenia B1 Planet Nivenia B2 Planet Nivenia B3 Planet Nivenia B4 Planet Nivenia B5, and moon Moon Nivenia B5.1 Interests Nivenian Empire, United Democratic Republic of Nivenia B Paulo Fluctus Beta System Planets and Moons (Inner System) Planet Paulo Fluctus Beta 1 Planet Paulo Fluctus Beta 2 Planet Paulo Fluctus Beta 3 Planet Paulo Fluctus Beta 4 Planet Paulo Fluctus Beta 5, and moon Moon Paulo Fluctus Beta 5.1 Planet Paulo Fluctus Beta 6, and moons Moon Paulo Fluctus Beta 6.1, Moon Paulo Fluctus Beta 6.2 and Moon Paulo Fluctus Beta 6.3 Planet Paulo Fluctus Beta 7 Planet Paulo Fluctus Beta 8, and moons Moon Paulo Fluctus Beta 8.1 and Moon Paulo Fluctus Beta 8.2 Planets and Moons (Outer System) Planet Paulo Fluctus Beta 9, and moons Moon Paulo Fluctus Beta 9.1, Moon Paulo Fluctus Beta 9.5, Moon Paulo Fluctus Beta 9.8, Moon Paulo Fluctus Beta 9.9 Interests Nivenian Empire, Republic of Paulo Fluctus Beta Caeruleo System Planets and Moons Planet Caeruleo 1 Planet Caeruleo 2, and moon Moon Caeruleo 2.1 Planet Caeruleo 3, and moons Moon Caeruleo 3.1, Moon Caeruleo 3.2, Moon Caeruleo 3.3, and Moon Caeruleo 3.4 Double planet Planet Caeruleo 4 - Planet Caeruleo 4.1 Planet Caeruleo 5, and moons Moon Caeruleo 5.1, Moon Caeruleo 5.2, Moon Caeruleo 5.3, Moon Caeruleo 5.4, Moon Caeruleo 5.5, and Moon Caeruleo 5.5 Planet Caeruleo 6, and Moon Caeruleo 6.9 Planet Caeruleo 7, and moons Moon Caeruleo 7.1, Moon Caeruleo 7.2, Moon Caeruleo 7.3, and Moon Caeruleo 7.4 Interests Nivenian Empire, Caeruleo Governmental Holding Corporation Thadus 0002 System Planets and Moons Planet Thadus 0002 1 Planet Thadus 0002 2, and Moon Thadus 0002 2.1 Planet Thadus 0002 3, Moon Thadus 0002 3.1, and Moon Thadus 0002 3.2 Planet Thadus 0002 4, and Moon Thadus 0002 4.1 Planet Thadus 0002 5 Planet Thadus 0002 6, Moon Thadus 0002 6.5, Moon Thadus 0002 6.7, and Moon Thadus 0002 6.8 Planet Thadus 0002 7, Moon Thadus 0002 7.1, Moon Thadus 0002 7.2, Interests Nivenian Empire Nivenia Space Rouge Planets Planets and Moons (0 to 4 light-years) Planet Thadus 0037, Moon Thadus 0037 2 Interests Nivenian Empire, Democratic State of New Home†