Space Colony

The thought occured to some people (most notably Gerard O'Neill) that if the delta-V cost for traveling up and down a planet's gravity well is so expensive, the expense can be avoided if you simply live in space inside a titanic space station. The classic "L5 Colony" was about 32 km long, and held 10,000 inhabitants. Such a colony could earn its keep by harvesting solar energy or with other more shady revenue streams. A quick Google search on "L5 Colony" will reveal a wealth of details.

And if you stick an engine on the end, you have a Generation Starship

It sounds very utopian, and it is.

Now, in a Rocketpunk future, when space stations are dotted over the entire solar system (or even the entire galaxy), they might start out as being just a tiny habitat functioning as a Transport Nexus. Yes, they may start as glorified airplane terminals, but they can become more than that. Space stations near research sites can become college towns, ones near mining sites can become mining towns. Then along will come people willing to import and sell things to the inhabitants, and suddenly you've got a city. Think about the TV show Babylon 5, about a space station at the intersection of interstellar transport routes between several star nations. Started as an outer space bus terminal, but grew to become a center of trade and diplomacy.

If the space city has its own revenue stream, it can go even further, and become an independent city state or station-republic. At some point they will be growing fast enough to justify investing in the construction of a full sized L5 colony.

But remember what Thucydides said above about devolution. If the space city's revenue stream dries up, the city becomes a slum, or even a ghost town. Especially if the space city is a boomtown, there to supply a fine selection of expensive vices to the local asteroid gold strike or Spaceguard military base. If the strike dries up or the base is relocated, the space city will die and become a ghost town.

Space habitats appear in science fiction in the Mobile Suit Gundam Wing animes, C. J. Cherryh's Alliance-Union novels, Alexis Gilliland's Rosinante trilogy, George Zebrowski's Macrolife, John Varley's Gaea Trilogy, Sir Arthur C. Clarke's Rendezvous with Rama, and the tv series Babylon 5.

One problem is that you cannot make a small O'Neill cylinder as a pilot project to gain the expertise to build a full size one, due to the nausea caused by the Coriolis effect. Your first one has to be full sized.

A space colony is a particularly pure example of a hydraulic state because Air Is Not Free. If citizens make angry the powers-that-be (defined as "the people who control life support), said citizens will suddenly find themselves trying to breath vacuum. Obey or die. The way to avoid this is with massively redundant life support infrastructure, in an attempt to decentralize control. Of course this only means you do not have to obey the space colony boss, just obey the boss of the segment you live in.

In C.J. Cherryh's Alliance-Union universe, none of the interstellar colonies are actually on an extrasolar planet. Instead they are space habitats in orbit around various lifeless planets (with the exception of planet Pell). The glaring unanswered question is if you are not going to be using the extrasolar planets, why did you go to the insane expense of using slower-than-light technology to create space habitats in other stellar systems? It would have been about a million times cheaper to just build the habitats somewhere in our own solar system.

If one is colonizing other stellar systems with slower-than-light starships, mass is at a premium. The expense of delta-Ving every microgram up to insterstellar velocities then braking to a halt means you won't be able to carry much of anything. It requires much lower mass to carry the needs for a colony on a human-habitable planet as compared to carrying the industrial machinery required to construct kilometer-long L5 colonies. In fact, such a colony ship might not even carry full grown colonists.

Naturally if you postulate FTL starships, all bets are off. Then it simply becomes a matter of transport costs.

This may or may not boil down to Space Habitats initially being unique to Terra's solar system.

If the space colony is larger than your average planet it is called a Megastructure. This includes things like Ringworlds and Dyson Swarms.



  • Aerostats are massive cities floating in the upper cloud layers of Venus.
  • Beehives are tunnel warrens inside asteroids and moons.
  • Clusters are microgravity habitats consisting of interconnected modules.
  • Cole bubble habitats are hollowed-out asteroids, terraformed on the inside, and also spun for gravity.
  • Dome habitats are massive domes built on the surface of moons, asteroids, or Mars.
  • Hamilton cylinders are self-building advanced nano-tech habitats designs.
  • O'Neill cylinder habitats are like large soda cans, only huge, over a kilometer wide and several kilometers long. The interior is terraformed and the entire cylinder is spun for light gravity. O'Neill cylinders are sometimes paired together, end to end.
  • Reagan cylinders are an inefficient type of O'Neill cylinder, built by hollowing a cylinder within a spinning asteroid, and used in the Jovian Republic.
  • Tin can habitats are small, cramped, cheap, modular boxes, typically used in early space colonization.
  • Torus habitats are big donuts or wheels, spun so that the outer rim has gravity. The interior spokes are zero-G.


Transhumanity is not just a spacefaring race, it is also largely space-dwelling. While a substantial portion of transhumanity inhabits planetary bodies like Mars, Luna, Venus, and the moons of the gas giants, the balance live in a variety of space habitats, ranging from the old-fashioned O'Neill cylinders of the inner system to the Cole bubbles of the outer system.

Space Habitats

Space habitats come in many sizes and configurations, from survivalist outposts designed to support ten or fewer people to miniature worlds in resource-rich areas housing as many as ten million people. In heavily settled regions of space, such as Martian orbit, habitats may be integrated into local infrastructure, relying to some extent on supply shipments from other orbital installations.

More commonly, especially in the outer system, habitats are independent entities. This usually means that in addition to the main space station, the habitat is attended by a host of support structures, including zero-g factories, gas and volatiles refineries, foundries, defense satellites, and mining bases.

Habitats—especially large ones—sometimes have visitors, as well. Majors habitats are crossroads in space. In addition to scheduled bulk freighter stops, they may have hangers-on such as scum barges, prospectors, or out-of-work autonomous bot swarms.

Many habitats have some form of transportation network. This is most common in large cylindrical habitats with centrifugal gravity. Common solutions for public transit include monorail trains, trams, and dirigible skybuses. Common personal transit options included bicycles, scooters, motorcycles, and micro-light aircraft, with larger vehicles being uncommon and usually reserved for official use.

Most habitats with large interior spaces also use augmented reality overlays to create consensual hallucinations of a sky and clouds, to which most residents keep their AR channels tuned. One would think that in space, talking about the weather would have disappeared from transhumanity's repertoire of small talk, but the habit persists—only the weather discussed is usually virtual (if it's not real "weather"—solar flare activity and the like).

Cluster Colony

Clusters are the most common form of microgravity habitat. Clusters consist of networks of spherical or rectangular modules made of light materials and connected by floatways. Typically business and residential modules are clustered around arterial floatways and infrastructure modules such as farms, power, and waste recycling. Limited artificial gravity areas may exists, frequently parks or other public places and specialized modules like resleeving facilities (morphs often keep better when stored in gravity). Arterial floatways in large clusters may have "fast lanes" where a constantly moving conveyor of grab-loops speeds people along.

Clusters are most commonly found in volatile-rich environments like the Trojans and the ring systems of the gas giants (particularly Saturn). Clusters are rare in the Jovian system because shielding a cluster of individual modules rather than one large station from Jupiter's intense magnetosphere is hideously inefficient.

Cluster colonies can have anywhere from 50 to 250,000 inhabitants.

Cole Bubbles

Cole bubbles (or "bubbleworlds") are found mostly in the main asteroid belt, where the large nickel-iron asteroids used to construct them are abundant. Bubbleworlds are less common in the Trojans and Greeks, where crusty ice asteroids predominate. A Cole bubble is similar in many respects to an O'Neill cylinder, but there are no longitudinal windows. Sunlight instead enters through axial mirror arrays. The bubbleworld is also constructed very differently, using a large solar array to heat a pocket of water inside of a metal asteroid so that the metal expands. Rotating the asteroid causes the malleable material to form a cylinder, which is then capped off and the water drained. The inside can then be pressurized, built out, and planted. Cole bubbles can also be spun for gravity, according to the whims of the inhabitants, though the gravity lowers as you near the poles of the bubble, with zero gravity at the axis of rotation.

Cole bubbles are among the largest structures transhumanity has created in space. The largest Cole habitat, Extropia, has a population of 10 million.

Hamilton Cylinders

Hamilton cylinders are a new technology. There are only two fully operational Hamilton cylinders in the system, but the design shows great promise and is likely to be widely adopted over the coming period. Hamilton cylinders are grown using a complex genomic algorithm that orchestrates nanoscale building machines. These nanobots build the habitat slowly over time, a process more like growing than construction.

Similar to O'Neill cylinders and Cole bubbles, a Hamilton cylinder is a cylindrical habitat rotating on its long axis to provide gravity. Both known Hamilton cylinders orbit Saturn in positions skimming the rings near the Cassini division. From this position, they can graze on silicates and volatiles using harvester ships.

Neither of the currently-operating Hamilton cylinders have grown to full size yet, but estimates say they could each house up to 3 million people.

O'Neill Cylinders

Found mostly in the orbits of Earth, Luna, Venus, and Mars, O'Neill cylinders were among transhumanity's first large space habitat designs. O'Neill cylinders are no longer built, having been replaced by more efficient designs, but are still home to tens of millions of transhumans. O'Neill cylinders were constructed from metals mined on Luna or Mercury, Lunar volatiles (including Lunar polar ice), and asteroidal silicates.

A typical O'Neill habitat is thirty-five kilometers long, eight kilometers in diameter, and rotates around its long axis at a speed sufficient for centrifugal force to create one Earth gravity on the inner wall of the cylinder. Smaller cylinders exist, though these usually feature lower gravity (typically Mars standard). Cylinders are sometimes joined together, end-to-end, for extra long habitats. A spaceport is situated at one end on the rotational axis of the cylinder (where there is no gravity). Arrivals by space use a lift or microlight launch pad to get down to the habitat floor.

The inside of an O'Neill cylinder has six alternating strips of ground and window running from one cap of the cylinder to the other. One narrow end of an O'Neill cylinder points toward the sun. The opposite end is the mooring point for three immense reflectors angled to reflect sunlight into the windows. Smart materials coating the windows and reflectors prevent fluctuations in solar activity from delivering too much heat. The air inside the cylinder and its metal superstructure provide radiation shielding.

The land in most O'Neill cylinders is one-third agricultural (a combination of food vats and high-yield photosynthetic crops), one-third park land, and one-third mixed use residential and business. O'Neill habitats have a day and night cycle regulated by the position of the external mirrors. The business and residential sections of the cylinder usually alternate with the park land over two of the strips of land; cropland usually takes up the third. Bridges cross the windows every kilometer or so, linking the land strips. The interior climate, the architectural style of the structures, and the types of vegetation and fauna present vary with the tastes of the habitats' designers.

Depending upon size, O'Neill cylinders can house from 25,000 to 2 million people.

Tin Cans

Antique research stations and survivalist prospector outposts often fit this description. Tin can habitats are only a few notches up from the early 21st-century International Space Station. Tin cans usually consist of one or more modules connected to solar panels and other utilities by an open truss. Deluxe models feature actual floatways or crawlways between modules, while barebones setups require a vacsuit or vac-resistant morph to go from room to room. Food growing capacity is severely limited and there may be no farcasters, but fabricators are available, as well as mooring for shuttles and perhaps prospecting craft. Tin cans rarely house more than 50 people.


Interchangeably called toruses, toroids, donuts, and wheels, these circular space habitats were a cheap alternative to the O'Neill cylinder used for smaller installations. Like O'Neill cylinders, toruses are seldom constructed anymore, but many are still encountered in the inner system, particularly in Earth and Lunar orbit.

A toroidal habitat looks like a donut 1 kilometer in diameter, rotating on great spokes. There is a zero-g spaceport at the wheel's hub. Visitors take a lift down one of the spokes to the level of the donut, where rotation creates one Earth gravity.

The plan of toroidal habitats varies greatly, as many were designed for specific scientific or military purposes and only later taken over as habitats by entrepreneurs or squatters. Many have a succession of decks in the donut. Most of those designed for long-term self-sufficient habitation have smart material-covered glass windows for growing plants along much of the inside surface of the torus. Toroidal habitats equipped for farming normally face the sun in a direction perpendicular to their rotational axis, but then use a slow processional wobble of that axis to create a day/night cycle.

Toruses were usually built to accommodate small crews of 500 or fewer people, though some larger ones exist, able to house 50,000. A few rare double-toruses also exist, like two large wheels spinning in opposite directions, joined at the axis.


      The last winnowing-screen will probably be the most controversial: I decided not to include any stories about space stations or “O’Neill"-style orbital L5 colonies. For one thing, because there’s been a recent rush of anthologies full of such stories—including Skylife, edited by Gregory Benford and George Zebrowski, and Star Colonies and Far Frontiers, edited by Martin H. Greenberg and John Helfers—but also because “L5 colony” stories have a dated smell to them now, to me, anyway.

     There was a glut of such stories in the late seventies that persisted throughout much of the eighties, a fad that dominated the field for several years, but now, more than fifteen years later (this was written in 2001), that particular concept seems faded to me, dusty, an SF dream of the future that's never going to come true, receding into distance, much like domed cities and continent-girdling slidewalks and automated highways.

     (My own opinion, for whatever it's worth, is that deliberately planned and created all-in-one-shot space cities of the “L5 colony” type are unlikely, anytime in the reasonably foreseeable future—enormously too expensive, for one thing, and, as many stories, such as Paul J. McAuley’s recent “Quiet War" stories, have shown, too vulnerable to a million forms of sabotage and terrorism to be really practical; easier by far to create bases dug into the sheltering rock of the Moon, or Mars, or even to hollow out an asteroid.

     We probably will get space cities eventually, but they won’t be planned, as such; instead, my guess is that they'll accrete slowly and gradually, haphazardly, bit by bit, around space factories and other installations that have a practical reason for being there, like company towns springing up around a mine or a military base, and although the inhabitants may be de facto colonists, in the long run, they won't think of themselves as such until several generations have gone by— they'll just be people who work in space, until their children or grandchildren decide not to go home.)


8.24 Space colonies

     I can imagine some readers at this point saying, all this talk of going to space and traveling in space, and no mention of space colonies except those on the surface of planets. There are hundreds and hundreds of stories about self-sufficient colonies in space.

     There are indeed, and during the 1970s I read many of them with pleasure and even wrote some myself. One of the most fruitful ideas involved "L-5 colonies." "L-5" describes not a type of colony, but a place. In the late eighteenth century, the great French mathematician Joseph Louis Lagrange studied the problem of three bodies orbiting about each other. This is a special case of the general problem of N orbiting bodies, and as mentioned in the previous chapter, no exact solution is known for N greater than 2. Lagrange could not solve the general 3-body problem, but he could obtain useful results in a certain case, in which one of the bodies is very small and light compared with the other two. He found that there are five places where the third body could be placed, and the gravitational and centrifugal forces on it would exactly cancel. Three of those places, known as L-1, L-2, and L-3, lie on the line joining the centers of the two larger bodies. The other two, L-4 and L-5, are at the two points forming equilateral triangles with respect to the two large bodies, and lying in the plane defined by their motion about each other.
     The L-1, L-2, and L-3 locations are unstable. Place a colony there, and it will tend to drift away. However, the L-4 and L-5 locations are stable. Place an object there, and it will remain. There are planetoids, known as the Trojan group, that sit in the L-4 and L-5 positions relative to Jupiter and the Sun.

     The Earth-Moon system also has Lagrange points, which in the case of the L-4 and L-5 points are equidistant from Earth and Moon. In the 1970s, an inventive and charismatic Princeton physicist, Gerard O'Neill, proposed the L-5 location as an excellent place to put a space colony (L-4 would actually do just as well). The colonies that he designed were large rotating cylinders, effective gravity being provided by the centrifugal force of their rotation. Within the cylinder O'Neill imagined a complete and self-contained world, with its own water, air, soil, and plant and animal life. Supplies from Earth or Moon would be needed only rarely, to replace inevitable losses due to small leaks.
     The idea was a huge success. In 1975 the L-5 Society was formed, to promote the further study and eventual building of such a colony.
     What has happened since, and why? Gerard O'Neill is dead, and much of his vision died with him. The L-5 Society no longer exists. It merged with the National Space Institute to become the National Space Society, which now sees its role as the general promotion of space science and space applications.

     More important than either of these factors, however, is another one: economic justification. The prospect of a large self-sufficient space colony fades as soon as we ask who would pay for it, and why. Freeman Dyson (Dyson, 1979, Chapter 11) undertook an analysis of the cost of building O'Neill's "Island One" L-5 colony, comparing it with other pioneering efforts. He made his estimate not only in dollars, but in cost in man-years per family. He decided that the L-5 colony's per family cost would be hundreds of times greater than other successful efforts. He concluded "It must inevitably be a government project, with bureaucratic management, with national prestige at stake, and with occupational health and safety regulations rigidly enforced." All this was before the International Space Station, whose timid builders have proved Dyson exactly right: "The government can afford to waste money but it cannot afford to be responsible for a disaster."
     The L-5 colony concept has appeal, and the technology to build the structure will surely become available. But it is hard to see any nation funding such an enterprise in the foreseeable future, and still harder to imagine that industrial groups would be interested.
     The L-5 colony—regrettably, because it is such a neat idea—is part of what I like to call false futures of the past, projections made using past knowledge that are invalidated by present knowledge.

     I believe there will certainly be space colonies in the future. Write stories about them by all means. But don't make them rotating cylinders at the L-5 location. Those stories have already been written.

From BORDERLANDS OF SCIENCE by Charles Sheffield (1999)

Space Colony Fates



The problem with a space station as Mos Eisley is simple. Who's providing the air? A lawless space station sounds good, but it's going to run into an extreme form of the "Three Generations Rule" from Attack Vector: Tactical. Either air will be ignored and everyone dies, or it will be the major point of conflict. No space station can survive without a single controlling power that runs the life support. The same applies to any other form of space habitat.

Neon Sequitur:

The 'Mos Eisley' concept may not work for an entire functional space station, but it makes a bit more sense if all or part of a station is considered 'written off'. Babylon 5 had a slum sector, which the station management considered not worth cleaning up. This conveniently allowed the writer(s) to have both a strong central authority on B5 as well as part of the station which resembled Mos Eisley.

In Transhuman Space, the Three Generations Rule rule might be considered a blessing when it comes to squatters in abandoned habitats. It saves the Powers That Be the expense of evicting them, or even deciding who's responsible for doing so. It's a given the life support will fail eventually. Until that happens, however, it's sort of a temporary 'tent city' version of Mos Eisley. (And that sounds like yet another pile of story ideas....)


There's no reason that this can't be worked into the plot. Our own human nations are not immortal. Our corporations can be consumed or die of incompetence. Just because Rome was not eternal did not mean it could not exist for the span it did. The vast majority of seeds do not become trees but that does not mean a forest cannot be.

Any properly vast station would have hundreds of sectors with redundant life support and power generation systems. If we imagine the station as an island in space, consider Hispaniola. On one side we have a functioning states, the Dominican Republic. On the other side we have Haiti, a dysfunctional mess. Same island, same resources, different results.

I could imagine a very interesting setting on a vast station that is suffering from the collapse of unified control. Some sectors are properly maintained and society is functioning as it should. Other sectors are in poor maintenance. Some of the common areas are completely out of maintenance, possibly open to hard vacuum. Perhaps the functioning side lacks the resources to fix the broken areas, maybe lack the manpower.

You have a story of resource depletion and civil war on Easter Island. A relatively advanced primitive society tore itself apart, likely over religion and politics. Imagine if you had a dozen islands within sight of each other, some of them maintaining social order while others descend into cannibalism and anarchy.

So as far as your Mos Eisley station example, a small one would be operated by one pirate king, the same way pirate settlements in the Carribean were founded by notable individuals. His house, his rules. Visitors pay rent. He provides the power, air, and food. For larger pirate settlements, each faction would maintain their own area. You wouldn't see chaotic evil pirates running these places, they'd be pragmatic amoral. These would be the guys you could trust in the sense that you know they are rational and have reputations to maintain in the community. You might get knifed in the back if no one is to be the wiser but they're not going to cheat you openly in a way that would harm their reputations. Get known as a cheat and no other pirate will risk doing business, savvy?

The rationale for a pirate haven like this is fairly obvious. Pirates can't get their ships worked on in legitimate yards. They need a place to handle repairs too big for the hands onboard. They need a place for R&R, can't exactly stretch your legs in places where the cops are. Ships can refit and recrew here. And there's also the need to fence stolen goods. Here pirate cargo gets traded to "honest" merchantmen and can get back on the open market.

Now any number of things can happen to jeopardize the viability of such a pirate haven and that's where the stories get interesting.


In our hypothetical space station, however, why would people who are keeping their sections in good shape provide for those who don't. Any earth analogy can only be taken so far, as we can managed to get all we need to live pretty much on our own here. The same is not true of a station, and if a sector is in chaos, the life support is going to get neglected, and that's going to lead to a crash very quickly. Atomic rockets points out that a space colony very much resembles a hydraulic empire. It simply can't be anarchy. There might be some parts that are seedy, but I doubt an entire station will be a lawless area, or even most of it. The pirate lord described is plausible, however.


Ah, good question. That's just it — it wouldn't be a hydraulic empire. For a large station, I'm imagining it being more like a condo. Stations have sections and sections are controlled by some form of polity, a faction. All the equipment necessary for survival is contained within that section. Each section beyond that is also self-supporting, just like owners in a condo -- the owner pays the note on his mortgage and nobody else in the community needs to help him on that. Of course, condos have areas of common responsibility and expense. When the organization becomes dysfunctional, that sort of stuff deteriorates. And then you can end up with the situation of individual units held onto by owners as the rest of the neighborhood deteriorates.

Now you may ask "Why would a station be built with so much redundancy in the first place?" And that would be precisely to avoid the situation of a hydraulic empire as you state. Say three factions come together to build a trading station in neutral territory. The expense is greater than any individual power can afford so they split the cost. The station is constructed. Each faction has territory on the station that they own in the clear. Furthermore, those sections are self-supporting for all essentials because they wish to avoid the chance of anyone cutting them off from the station's grid. But because there are common needs of the station, all three pay towards the maintenance of the structure and what elements cannot be easily triplicated. On paper this operations company may be considered independent and neutral with personnel drawn from all three factions or maybe from third parties. But you can well imagine how things on such a station could become dysfunctional in time.

From comments to Transport Nexus

“Charges in place? Conduits sealed? Okay, go ahead and open it up.”

The heavy wrench descending, clangingly, on the sealed emergency hatch once, twice, three times before the seal broke, a wave of fouled air rushing out past the linobir enforcer and hsis men. Beyond, the milling crowd, faces pale and dark and congested with nerves, eyed them uneasily and decided not to make a break for it.

“All right, which of you self-f*ck*n’ dock-rats claims t’be in charge of this section?” hse bellowed. “He’s got some things to ‘splain and so have I. Speak out, if breathin’ this crud hasn’t rotted your brains too much to parse plain Trade.”

Hser eye fell on a pair of scruffy deshnik arguing with one of his men, brandishing a smart-paper token.

“She’s got a pass? Any of the rest of you recognize this one?”

“Sure, boss, up on Thirty with the Torashanika clan.”

“Then get out of here — Just you, kid. He ain’t got a pass… No arguin’. You got three choices. You can stay here and kiss space with the rest of ‘em when their time comes, or you can run back to your clan-group and try an’ talk ‘em into buying out his life-debt.” Not that there was much chance of even a desperate clan-group doing that for a casteless deshnika flesh-peddler. “Or you can try and get past me an’ I’ll paint the deckhead with your brains. Estrev always gets his cut; no exceptions.”

“Listen up, the rest of you clut-grubbers! I speak for the drift-estrev, and the drift-estrev is not happy. You’re breathin’ his air and burnin’ his bunkerage, and what’s he getting back from you? Nothin’ but dioxide, taint, and an infestation of this pink sh*t.”

The linobir kicked at a squirming tendril of the ubiquitous hab-slime with a mid-limb.

“Now the estrev says you’ve got two cycles to pay off your life-debts and figure out how to make him value your worthless selves, or else I get to take the four pounds of trinol packed into these joints and blow your sh*t-house sewerslum right off station-end. Tell whoever’s hidin’ back there and breathe deep while y’can.”

“Close it up, boys. Message delivered.”


Traveling algae tank salesman: "The right to recycle air is the right to be free."


    The Ahk designated as FT-0101 was an Espatier.  It’s Ka was the pruned fork of Sergeant 5Djeffries Muh.  It’s Ba was a mechanical monster.
    The interior of the vast O’Neill cylinder that was now part of 3Gleise’s territory was patrolled by Cerberus fighters modified for use as squad transports.  Eight hulking brutes, clipped to the exterior of each war rocket, were launched from the destroyers escorting the space station to secure the inside.  It had taken days to go through the vast habitat, comparment by compartment, capturing and removing the thousands of workers found within.  Most were Gleise citizens, now repatriated.  The remainder, AdStar overseers, were captured and sent for interrogation.
    FT-0101 lead the first squad of the first platoon of DesCon 3’s Expeditionary Force.  It had been online for eight-seven hours now, leading its squad in what was essentially a massive boarding action.  It was the certainly the right Ahk or the job.  FT-0101 had faught on planets, with and without atmosphere, asteroids, moons, and habitats of all sizes.  It had fought on starships ranging from corvettes to to titanic battlers. It was the best of the best.
    It had never seen anything like this before.
    “Roger that, FT-0101.  Get video on all frequencies.”  
    The Espatier Ahk began recording what it saw, in thermal, visible, ultraviolet and x-ray.  The O’Neill was small, as these things go; only eight kilometers long with a radius of a thousand meters.  Despite this, the interior cavity should have been at least five hundred meters wide.  Espatiers on the ground recorded an internal space only two hundred meters wide, divided into compartments every half kilometer.
    “This is downright claustrophobic.”
    FT-0101 focused on an area of the interior skin that hadn’t been completed.  A vast cenote in the artificial ground gaped open, exposing layers upon layers of water bags and aerogel bricks under the surface.  Through the middle of the hole was a what looked like a tall ridge made of carbon that was spun in long ropes of self-supporting latticework.
    “It looks almost like buttressing.”
   FT-0101 continued moving forward.  There was no soil on the decking — just layers of woven carbon fiber plates.  Here and there were other Espatiers examining the odd modifiactions to the habitat.  The central hub, for example, was ribbed by additional buttressing that curved outward toward the compartmenting wall dividing the entire open space of the cylinder a few hundred meters ahead.  The curving buttresses from the column gradually arched over the dividing wall to meet the even larger and wider ridges in the rimward walls.
   “That’s one way of putting it.  Looks familiar, though.  Keep panning around, please.”
   FT-0101 anchored its bulk to the deck and began rotating its main cameras around a hundred and eighty degrees, missing nothing.  There were veins of raised tubing standing out upon the partition like spiderwebs of renforcement.  The curving arches made a graceful symmetry.
   “Wait a moment!  Right there!”
   FT-0101 froze, as only a robotic Ba could.
  “Oh, oh Netjer.  I know what this is!
  “Those dividing walls, they’re rib vaults.”
  “They’re oriented to support the cylinder’s mass along the long axis. Against accelleration.”
  “The outer walls are filled with enough insulation to absorb a full laser barrage.”
  “UNDERSTOOD.” This was the closest FT-0101 ever got to an exclamation. “THIS IS NOT A HABITAT CYLINDER.”
  “Not anymore.  Its a capital ship.”  

From O'NEILL CYLINDER by Ray McVay (2016)

(ed note: "Earthplanet" is Terra. It had a world government. It has since balkanized due to several civil wars. "Earthsystem" is the solar system space colonies. Politically they have little or no contact with Terra.)

      McNulty shut off the tapeviewer. “During the past two ship days,” he remarked, “I have recorded news reports of forty-two of these so-called miniwars on the planet. Several others evidently are impending. Is that normal?”
     “Actually it sounds like a fairly quiet period,” Hiskey said. “But we might liven it up!” He pulled out a chair, sat down. “Of course I haven’t been near Earthsystem for around eight years, and I haven’t paid too much attention to what’s been going on here. But on the planet it’s obviously the same old stuff. It’s been almost a century since the world government fizzled out; and the city states, the rural territories, the sea cities, the domes, the subterranes and what-not have been batting each other around ever since. They’ll go on doing it for quite a while. Don’t worry about that.”
     “I am not worrying,” McNulty said. “The employment possibilities here appear almost unlimited, as you assured us they would be."

     Hiskey grinned. “There’s a little more to it than that. Did your tapes tell you anything about Earthsystem’s asteroid estates?
     “Yes. They were mentioned briefly twice,” McNulty said. “I gathered their inhabitants retain only tenuous connections with the planetary culture and do not engage in belligerent projects. I concluded that they were of no interest to us.”
     “Well, start getting interested,” Hiskey told him. “Each of those asteroids is a little world to itself. They’re completely independent of both Earthplanet and Earthsystem. They got an arrangement with Earthsystem which guarantees their independent status as long as they meet certain conditions. From what Gage’s sister told him, the asteroid she’s on is a kind of deluxe spacegoing ranch. It belongs to a Professor Alston . . . a handful of people, some fancy livestock, plenty of supplies.”

     “A private asteroid—any private asteroid—is expected to go out of communication from time to time. They’re one of Solar U’s science projects. They seal their force field locks, shut off their transmitters; and when they open up again is entirely up to them. I’ve heard some have stayed incommunicado for up to ten years, and the minimum shutoff period’s supposed to be not less than one month out of every year."

     Professor Derek Alston’s asteroid also remained something of an enigma. In Mars Underground, and in the SP Academy’s navigation school, the private asteroids had been regarded much as they were on Earthplanet, as individually owned pleasure resorts of the very rich which maintained no more contact with the rest of humanity than was necessary. Evidently they preferred to have that reputation. Elisabeth had told him it wasn’t until she’d been a Solar U student for a few years that she’d learned gradually that the asteroids performed some of the functions of monasteries and castles in Earth’s Middle Ages, built to preserve life, knowledge, and culture through the turbulence of wars and other disasters. They were storehouses of what had become, or was becoming, now lost on Earth, and their defenses made them very secure citadels. The plants and animals of the surface levels were living museums. Below the surface was a great deal more than that. In many respects they acted as individual extensions of Solar U, though they remained independent of it.

     Elsewhere were the storerooms; and here Elisabeth loved to browse, and Harold browsed with her, though treasures of art and literature and the like were of less interest to him. Beautiful things perhaps, but dead.

     And then the projects—Step into a capsule, a raindrop-shaped shell, glide through a system of curving tunnels, checking here and there to be fed through automatic locks; and you came to a project. Two or three or at most four people would be conducting it; they already knew who you were, but you were introduced, and they showed you politely around. Elisabeth’s interest in what they had to show was moderate. Harold’s kept growing.

     “You’re running some rather dangerous experiments here,” he remarked eventually to Derek Alston.
     Derek shook his head. “I don’t run them,” he said. “They’re Solar U and SP projects. The asteroid merely provides facilities.”
     “Why do you let them set themselves up here?”
     Derek Alston shrugged. “They have to be set up somewhere. If there should be some disastrous miscalculation, our defensive system will contain the damage and reduce the probable loss in human lives.”

     And the asteroid had, to be sure, a remarkable defensive system. For any ordinary purpose it seemed almost excessive. Harold had studied it and wondered again.

     “In Eleven,” he said, “they’re working around with something on the order of a solar cannon. If they slip up on that one, you might find your defensive system strained.”
     Derek looked over at him. “I believe you weren’t supposed to know the purpose of that device,” he said idly.
     “They were a little misleading about that, as a matter of fact,” said Harold. “But I came across something similar in the outsystems once.”
     “Yes, I imagine you’ve learned a great deal more there than they ever taught in navigation school.” Derek scratched his head and looked owlish. “If you were to make a guess, what would you say was the real purpose of maintaining such projects on our asteroid? After all, I have to admit that the System Police and Solar U are capable of providing equally suitable protective settings for them.”
     “The impression I’ve had,” Harold told him, “is that they’re being kept a secret from somebody. They’re not the sort of thing likely to be associated with a private asteroid.”
     “No, not at all. Your guess is a good one. There are men, and there is mankind. Not quite the same thing. Mankind lost a major round on Earthplanet in this century and exists there only in fragments. And though men go to the outsystems, mankind hasn’t reached them yet.”
     “You think it’s here?”
     “Here in Solar U, in the System Police, in major centers like Mars Underground. And on the private asteroids. Various shapes of the same thing. Yes, mankind is here, what’s left of it at the moment. It has regrouped in Earthsystem and is building up.”
     Harold considered that. “Why make it a conspiracy?” he asked then. “Why not be open about it?”
     “Because it’s dangerous to frighten men. Earthplanet regards Earthsystem as an irritation. But it looks at our lack of obvious organization and purpose, our relatively small number, and it doesn’t take alarm. It knows it would take disproportionate effort, tremendous unified effort, to wipe us out, and we don’t seem worth it. So Earth’s men continue with their grinding struggles and maneuverings which eventually are to give somebody control of the planet. By that time Earthsystem’s mankind should not be very much concerned about Earthplanet’s intentions towards it.
     “The projects you’ve seen are minor ones. We move farther ahead of them every year, and our population grows steadily. Even now I doubt that the planet’s full resources would be sufficient to interfere seriously with that process. But for the present we must conceal the strength we have and the strength we are obtaining. We want no trouble with Earth. Men will have their way there for a time, and then, whatever their designs, mankind will begin to evolve from them again, as it always does. It is a hardy thing. We can wait. . . .”

     “Where’s the asteroid going on interstellar drives?”
     “I told you mankind hadn’t got to the outsystems yet,” Derek said. “But it’s ready to move there. We’ve been preparing for it. The outsystems won’t know for a while that we’re around—not till we’re ready to let them know it.”
     “This asteroid is moving to the outsystems?”

From THE CUSTODIANS by James H. Schmitz (1968) Collected in Agent of Vega

      Time passed. He turned the shell around, fired his little rocket and watched as the tiny shell slowly retarded its fall sunward. Past the orbit of Mars now, the crescent having widened out, until now Mars was an orb, a tiny disc of ruddy color off to his side.
     He watched the gauge of his limited fuel supply, and when it was three-quarters empty, he shut off his engine. The rest might yet save his life.
     Now he watched and scanned the sky. How many days passed, he couldn’t tell. A week, perhaps two weeks… He did not know. He had cut his food intake, limited his meals to drag out the stores. And he became slowly worried. Another meal or two left, and then slow starvation.
     He switched on his automatic S.O.S. sender broadcasting a general call. Was anything near?
     Slowly the hours passed, and he watched and waited and saw nothing. He ate his last meal, lingeringly, and it became a memory. His water supply, constantly renewing itself in a closed cycle would continue indefinitely. How long could a man go without food? Thirty days, he remembered from somewhere.

     He watched and lay on his stomach and wondered how weak he would be. He saw the stars, tiny cold points of white in the deep blackness. He noticed one that seemed to move among the others. It moved slightly, but it moved.
     Was it a ship?
     It had to be, he thought. What else could move? He knew there were asteroids—like Eros and Anteros, and Apollo— that cut deep within the orbit of Mars, went on almost to Venus. But there were also spaceships.
     He watched the tiny point of moving light, headed his shell that way, and started his engine. He began to move across the thousands of miles of space that separated him from the object between Mars and Earth.
     He watched it slowly grow brighter, and he could see that it was moving. It was moving in an orbit that would take it outward from that of Earth into that of Mars. But it moved so slowly, so strangely unlike the passenger liners and the space yachts, that he wondered what it could be. It would cut the orbit of Mars … but not for a terribly long time.
     It came closer, and he swung his shell towards it, and drew nearer. Nothing replied to his S.O.S. What spaceship would not answer such a call at this narrowing distance? What spaceship would not have a robotic tape, recording all the time, that would sound an automatic alarm at the receipt of his signal?

     The ship took shape, and the answers became clear. He saw at first not a slim gleaming metal liner, not a familiar tubular craft, but a wide sweep of white, reflecting starlight and sunlight. He saw emerge a pattern of four huge expanses of metallic surface, and he saw that they were paper-thin sails spread out into the void.
     He watched as it drew closer, and he recognized it from his studies. He saw the four huge sails, spreading over hundreds of square miles of void, and in the center, he saw the tiny doughnut doting the hub of these four incredibly vast sails. He drew toward it, swung his ship in the rear and ran up on it, matching his speed with that of the unusual vessel.
     As he drew closer, the vast sails obscured the stars on all sides, cut out the view of space and left only a curious impression of flickering opacity across the sky. He came up to the doughnut and found it even odder. It was a wheel, the hub of which was a flat disc several hundred feet across. On the edge of this circular disc, exactly like a tire fitted on a wheel, was a tube. A metallic tube perhaps thirty feet in width, fitted onto the rim of the disc, and rotating. It was a tire running around the edge of the disc steadily, at a fairly fast rate.
     He knew what it was. It was a cosmic ion-driven space freighter. It was literally a sailing vessel of the sky, the cheapest and most economical means of transportation ever devised between worlds. Put together in orbit, outside the grasp of Earth’s gravity, it was set on its way by the infinitesimal pressure of the cosmic rays, of the sun’s rays, of the ions generated in little force patches along the frames of the wings. Between the rocket-like drive of the ions and the steady pressure of the light of the sun and stars on its tremendous wing surfaces, it moved across space. Its orbit was a slow, long, leisurely one.

     But it was a refuge; it was life and safety. Ajax swung close to it, circled over the gleaming disc of the central freight compartment, then seeing the unmistakable hatchway of a loading compartment right up near the moving tube at the rim, set his shell down.
     It clung magnetically to the surface. Ajax fastened his helmet, swung back the top of his shell, climbed out. He swayed dizzily, fell to his hands and knees for a moment and hung on. He was weak, weaker than he’d feared. Only the fact that there was no gravity kept him from being entirely helpless.
     He caught his breath, staggered to his feet, and shuffled across on his magnetic shoes to the hatchway. He looked for a means of opening it from the outside, but there was none He clung to it, pounded with his fist on the outside.
     Surely someone must have noticed his arrival. Surely there must be someone who would hear the pounding on the outer hatch, even in the cargo nub. Surely there was a crewman detailed to watch the cargo who would hear.
     Time passed. Nothing seemed to stir inside. What sort of ship was this? Ajax wondered wearily, if he was doomed to die hanging to the outside of salvation?
     He pounded more. Beyond him he could see the sweep of the vast sails, moored to the body of the cargo hold by powerful metal stanchions. He could see now and then the tremor and shift of one of the miles of expanse as the invisible currents of space wafted here and there against those colossal sails.
     Still he clung. Was the ship deserted, dead? Was it all robot, no crewmen? He pounded again, felt his strength diminishing.
     The ionic freighter sailed slowly on.

     AJAX CALKINS clung there for what seemed like hours, but which was more likely minutes in the timelessness of anxiety, when at long last he felt a tremor in the metal disc of the loading port. He got to his feet, stepped aside, and waited as the outer disc slowly unscrewed and then swung open.
     He looked into the wide maw of the cargo airlock, and then stepped inside. He saw the automatic buttons that would close the lock from inside, punched them, waited. With that built-in slowness that seems characteristic of cargo holds, the outer disc swung shut, sealed. There was a hissing of air; gauges on the wall registered the rise of atmosphere inside the chamber, and when it reached parity, Ajax went over and unbolted the inner door.
     He stepped through to a narrow catwalk which threaded its way across a vast area of shrouded masses, undoubtedly the payload of this ship, deposited in the gravityless central hull. A man was standing before him, lit by the dim glow of the permalites in the hold.

     “Calmness, brother,” said this individual in a soft whispering tone. “All is serene in the Retreat of the Nirvanists. I am Brother Augustus. How call you yourself?”
     Ajax opened his space helmet, gulped in a few breaths of air. It tasted fresh to him who had been living in the limited and not-well-laundered air of the emergency shell, though doubtless it was stale and oil-laden.
     “I am … uh … Jack Callans …” he began, making up a name on the spur of the moment, realizing the danger that his real name might have been broadcast as a wanted criminal, “… uh … my ship was wrecked by disaster … thanks for saving me.”
     Brother Augustus looked at him from deep eyes, stroked the trim black beard that decorated the chin of his rather round and plump face, and nodded slowly. “You look in need of sustenance and rest,” he said in his soft, breathy tones. “Come with me to the rim quarters.”

     He turned and began to walk the catwalk, and Ajax followed him, his magnetic shoes clinging to the metal walk, his body floating free in the weightlessness of the unrotating hull. They came to a door, which Brother Augustus opened outwards.
     There was a gap of a yard here, and beyond that yard of space a smooth metal wall moved past rapidly. It was the inner wall of the rim-tube which rushed past, running, Ajax could see, on an endless series of ball-bearings and wheels that raced along a track inside the outer edge of the central hull.
     Brother Augustus beckoned to Ajax to come to the doorway, and when Ajax had done so, the bearded individual deftly stepped behind him. “When the door comes past, I will push you. Grab for the handles, and pull yourself into it.”
     “Whaaa …” Ajax began to question bewilderedly when suddenly a wide circular opening appeared, with a plastic door set into it. There was a shove and Ajax flew across the yard of space and slammed into the moving wall. Clutching out wildly, his hand closed on a metal handle and he clung to it, being dragged swiftly along the moving wall. In a second he was in near darkness, clinging to the moving wall, with only a dim greenish light over the closed door a few feet from him to show the other wall rushing past in the opposite direction.

     Weakly Ajax clung to it; then, as his eyes adjusted, he saw that there were a series of such handles and he moved himself to the door by pulling himself along. Once at the door, he pushed on it, and found it would slide aside. He got it open, pushed himself through, and fell across a narrow room as the door slid automatically shut over his head.
     Over his head? Ajax sat up. Sure enough, from where he was, the door he had entered by was in the ceiling of a low room. There was a ladder running down from it, which he presumably should have groped for.
     He sat a moment and then got his orientation. Of course he should have realized he would have weight; the purpose of the revolving tube area was to provide an artificial gravity for the crew of the ship by means of centrifugal force. The rotation exerted a pressure on the outside of the rim and everything within would feel a sense of gravitational weight. Ajax groggily stood up, only to sit down as his knees gave way under him. He was weak from his experiences, from hunger, and from lack of gravity.
     This ship was obviously based upon an economy of power. The centrifugal system for spaceship gravity had been replaced in faster ships by the new techniques of artificial gravity creation; but those techniques required power. The centrifugal system, once started, required but little to maintain it in space.
     He sat there until, after a few minutes, the door opened in the little room, and Brother Augustus looked in. “Ah,” he said softly, “I see you are weak.”
     He came in, and another man came with him. Now Ajax had the chance to examine the two more closely. Both were garbed alike, in rough brown smocks, reaching to their ankles. An emblem, that of a script letter X, was embroidered on the front of each man’s smock. Their hair was long and both wore short beards.
     The two lifted Ajax to his feet and helped him to leave the chamber. He found himself in a long narrow hallway and they walked him down until they came to a long narrow chamber with bunks lining the wall. They lifted Ajax into one.
     “Rest,” said Brother Augustus. “We will bring you food. You must regain your strength; then we shall talk.”

     It was perhaps two days later that Ajax Calkins was strong enough to leave his bed and have the promised talk with Brother Augustus. Meantime he had learned a good deal about the vessel he was on, through conversation with a patient, gay-bearded man who had been assigned to attend him.
     The ship was one of a number of such in service between Earth and Mars. It utilized the minimum of energy to carry its cargo back and forth; and sailing as it did, its relation to space flight was curiously like that of an old sailing ship of the Mayflower class compared to a fast jet airliner of the Twentieth Century. The Mayflower type took three months to cross the Atlantic; the jet plane six hours.
     This vessel took about three years to cross from Earth to Mars. It never docked on either planet, hovering in orbit while its cargo was unloaded by rocket tenders, and then beginning the slow sail back again. Because of their slowness, because of the endless tedium of the passage, such ships were given over to very special types of crews, crews that would devote the idle hours of the passage…and they were about ninety per cent of the hours involved…into pursuits of the mind and soul.
     There were several such ionic freighters that were true convents…vessels on which the foot of a male had never trod, while saintly women went about their meditations and prayers in an isolation never achieved on Earth. There were monasteries. There was one that was an academy of deep philosophy and abstract mathematics.
     This one was the Retreat of the Nirvanists. It was a sort of cult—a cult run by the man known as Brother Augustus— and its brotherhood were but temporary devotees, paying a good sum for the privilege of the long trip away from the tensions and troubles of Earth. In short it was a retreat of tired businessmen, men who wanted to overcome their ulcers, get away from nagging wives, escape other mental problems, or simply get away from it all for a half-dozen years.
     They spent many hours in meditation, and in the contemplation of music and poetry. They manufactured some items, doing handwork, while not checking the cargo.

     “At least,” said Ajax to the man who was explaining all this, “I didn't land on a convent ship!”
     The man smiled and agreed. It would have been a rather embarrassing predicament all around. “But, still, you are here away from the world …"
     Ajax sat up. “I want to talk to Brother Augustus about getting away from here. Has he a radio? What’s happening in the space war?”
     The man shook his head. “There is no radio here, brother. We are totally isolated from all news. And none may leave here until we reach Mars. You still have a year to go. Rest, take it easy, think, delve into your true self.”
     “What do you mean?” Ajax asked. “I have to get away. Surely I can borrow a ship's tender. You must have a couple of fast rocket craft for emergencies and landings.
     The man shook his head. “There may be such, but only Brother Augustus has access to them, and he will never permit it.”
     “I must speak to him,” said Ajax, getting to the floor. “Right away!”
     He slipped into the brown smock that had been given him while his own clothes were being laundered, and strode along the narrow passages to find the master of the Nirvanists.
     But Brother Augustus, whom he found supervising some work in a long workroom, where men toiled with hand tools at narrow benches, merely smiled sadly. “You must remain our guest,” he said. “Until we return to Earth.”
     “I’ve got to be here for four years!” yelped Ajax.
     “Four blessed, peaceful, soulful years of unchanging bliss. It’s Nirvana!” intoned Brother Augustus, rolling his eyes.
     “It’s Gehenna!” exclaimed Ajax.

     BROTHER AUGUSTUS arched his eyebrows at Ajax and slowly shook his head. “You will find the peace and calm of our retreat very beneficial. Soon you will lose the tension of your Earthly desires, and find the harmonies of our work beneficial."
     “Oh, no," said Ajax. “I’ve got to get going! Isn’t there some way you can lend me an escape rocket, a landing yacht, or something? Surely I can make it worth your while. Whatever it costs …”
     The master of the Nirvanists merely shook his head. “Absolutely not. Abide with us, friend Jack, abide with us in patience.”
     Calkins stamped a foot impatiently, but held back from another angry retort. He would have to find some way to get what he wanted. Meanwhile … He found himself curious about what the brothers were doing in that workroom.
     In spite of himself, he noticed the odd similarity of their work to old electrical light bulbs, not quite completed— but surely that man was twisting tiny filaments; and that one blowing fragile glass bulbs; and down there, several men were delicately inserting the filaments, twisting and cleverly winding and binding.
     Brother Augustus followed his eyes, smiled. “Yes, they are indeed making light bulbs. We find that there is a great demand back on Earth for old-fashioned bulbs, made by the loving care of devoted hands, and filled with the blessed vacuum of outer space itself.
     “We sell these bulbs to light the altars of lamaseries in distant Tibet and in modern Shasta. Students of the mystic lore find them soothing, with their perfect clear vacuum unspoiled by the contamination of machinery and planetary atmospheres.”
     Ajax looked at him, but the deep eyes of the man betrayed no emotion. Surely he could not be sincere; then vaguely Calkins recalled an ad here and there in journals for such bulbs as these. Well, he thought, there are crackpots and there are those who fatten on them.
     Which was Brother Augustus? The answer to his problem might well lie in that question.

     For several more days, Ajax found himself unable to do anything but follow the routine of the Nirvanists. It was a monotonous one, one designed to lull the mind and nerves. Several work hours, several hours devoted to quiet meditation, periods of listening to deep music, or listening to taped lectures on peace of mind.
     There was not a hint of the problems of mundane worlds. No newspaper, no news bulletin, no communication to be found anywhere, no books dealing with anything more substantial than philosophy. Ajax wandered the rim of the ionic sailcraft, was allowed everywhere, and learned that the control room was not in the rim, but in the core of the cargo hub—a locked area inaccessible to all save Brother Augustus.

     He went one morning to talk to Brother Augustus and found that worthy sitting quietly in his meditation room listening to a tape of an ancient symphony. As he entered, the bearded master raised a warning finger. Ajax sat down and listened. The tunes of the old instruments ran on, to Ajax’s ears, monotonously, but the Brother seemed entranced. Suddenly he flicked a finger in the middle of a bar. The music stopped. Ajax was about to talk, but the tape was run back, and instantly began again where it had been several minutes before.
     They waited. Then the music switched off. Brother Augustus looked up. “Did you hear it? The second violin? It was off, definitely off in the seventh beat of that movement. I have been suspecting this for many months. Finally I have traced it down. And now …" He looked at Ajax expectantly.

     Ajax jumped up and dashed angrily out. How could you argue with such an abstract man? He stamped down the long hall, past rooms and workchambers, ignoring the disapproving glances of the brothers.
     He came to a series of bedrooms, and realized suddenly that he was in front of Brother Augustus’ own private sleeping quarters. In a flash of fury, he tried the door, found it open, slipped in.
     Maybe he could find out something about that bearded man who kept him prisoner so efficiently. There must be a means to cajole him into renting one of the ship’s auxiliary rocketcraft!
     It was hardly an ethical act to go through his host’s private effects, but Ajax recalled to himself that few of the empire builders of the past would have worried about such a minor detail. In the establishment of a crown, these things were excusable.
     He glanced around the narrow quarters. The bed, the bureau, no. There was a cabinet. He tried it; it was locked. He pressed on it, and found that it was not too tight. Taking his pocketknife out, Ajax went to work with the tip of the blade. In a few seconds, he had the cabinet open, for the lock was not one of the magnetic modern ones. Brother Augustus went in for the old-fashioned too often at the wrong spots.
     There were notebooks, ledgers, piles of papers, some flat boxes. Quickly Ajax thumbed through them. Bills of lading, sailing orders, ledgers of sales, lists of the brothers on this voyage, profits and losses (that was an interesting one— Brother Augustus had acquired quite a neat bank account in the three tips he had already made).
     On the bottom of the pile, Ajax came to a single flat leather folder, worn and old. He slipped it out, unstrapped it, looked in.
     He sat down on the bed with a thud, eyes agleam. Quickly he took out several clippings, some old photos, a worn spaceman’s notebook. He skimmed through them rapidly and whistled to himself. Carefully extracting one of the old documents, he put the rest back, replaced the folder, closed the cabinet, and left the room.

     As he walked back to Brother Augustus’ music room, he was whistling. He nodded politely to the various recluses he met, and when he reached the music room, he knocked, then opened the door and went in.
     Augustus was still listening to tapes. It sounded to Ajax’s ears like the same tape, and the same composition. He sat down and waited.
     Augustus was beating time with one hand and leaning forward. His eyes flickered, he held up a finger, and smiled deeply. He shut the tape oil. “It’s that beat,” he said. “Definitely, absolutely. I’ve got him now. Oh, what an article I’ll write when I get back to Earth. This’ll be a discovery!”
     “Yes, I venture to say it will be,” said Ajax smiling, “and I made a little discovery of my own just now also.”
     “Indeed,” said the master of Nirvana, “I am pleased for you.”

     “Perhaps you won’t be so pleased,” said Ajax in a deceptively calm tone. “And I don’t think that the tired businessmen and student philosophers who signed up on this cruise will be too pleased either, Scat Ward!”
     Brother Augustus stopped rubbing his hands and stared at Ajax, motionless, silent. Then he said slowly, “What did you say?”
     “I said Scat Ward,” repeated Ajax. “Surely your piratical ears have not lost their keenness for the delicate nuance so suddenly?”
     Brother Augustus lowered his hands to his lap, stared at him with narrowed eyes. “And what does that mean to me, young man?” he whispered.
     “Perhaps it means the loan of an auxiliary rocket, eh, Scat, you old buccaneer?” Ajax pursued his query.
     The man known as Brother Augustus looked at him in silence. “How do you know?” he said. In answer, Ajax took the old document from his pocket and passed it in front of the other’s eyes. “One good bit of skulduggery deserves another,” he remarked. “I think the contents of this little ‘wanted’ notice, issued by the EMSA police, would unstabilize this heavenly retreat of yours. Shall I post it on the meditation board, or shall I be leaving shortly by rocket?”
     Brother Augustus’ eyes flickered. “The space pirate known as Scat Ward is a thing of the past. I have found true peace in my work here. There is no need for the introduction of turbulent thoughts in our serene atmosphere,” he said solemnly. “I am now inclined to feel that your departure from our Retreat would contribute to the general harmony.”
     “Ah,” said Ajax, “I felt sure that you would see the light, Captain Scat … uh, Brother Augustus.”

     Not two hours later, Ajax closed the tiny airlock of the trim little landing rocket tender, housed in its snug berth in the gravityless depths of the cargo hub, signaled a grateful farewell to the spacesuited figure of Augustus Ward, ex-space pirate, captain of the ionic freighter Nirvana, and Master of the Order of the Nirvanists, pushed the button for his exiting catapult, shot in his rocket engines, and headed outwards from the sun towards the asteroid belt.
     In a remarkably short time, the huge sailing vessel of space had dwindled to a spot of white, then finally vanished.

From DESTINY'S ORBIT by Donald A. Wollheim (writing as David Grinnell) (1961)

For twelve years, at a point where three major shipping routes of the Federation of the Hub crossed within a few hours' flight of one another, the Seventh Star Hotel had floated in space, a great golden sphere, gleaming softly in the void through its translucent shells of battle plastic. The Star had been designed to be much more than a convenient transfer station for travelers and freight; for some years after it was opened to the public, it retained a high rating among the more exotic pleasure resorts of the Hub. The Seventh Star Hotel was the place to have been that season, and the celebrities and fat cats converged on it with their pals and hangers-on. The Star blazed with life, excitement, interstellar scandals, tinkled with streams of credits dancing in from a thousand worlds. In short, it had started out as a paying proposition.

But gradually things changed. The Star's entertainment remained as delightfully outrageous as ever; the cuisine as excellent; the accommodations and service were still above reproach. The fleecing, in general, became no less expertly painless. But one had been there. By its eighth year, the Star was dated. Now, in its twelfth, it lived soberly off the liner and freighter trade, four fifths of the guest suites shut down, the remainder irregularly occupied between ship departures.

And in another seven hours, if the plans of certain men went through, the Seventh Star Hotel would abruptly wink out of existence.

From LION LOOSE by James H. Schmitz (1961) Collected in Trigger and Friends

(ed note: in this essay, Asimov uses the term "g people" to mean the people living on Terra, and "null-g people" to mean those living in space habitats and asteroid colonies)

Second, the nature of the null-g environment will make it certain that they will far outstrip us in variability and versatility. The g people will exist as one large glob (earth's population) with small offshoots on Mars, the moon, and elsewhere, but the null-g's will be divided among a thousand or more worlds.

The situation will resemble that which once contrasted the Roman civilization with the Greek. The Romans wrought tremendous feats in law and government, in architecture and engineering, in military offense and defense. There was, however, something large, heavy, and inflexible about Roman civilization; it was Rome, wherever it was.

The Greeks, on the other hand, reaching far lesser material heights, had a life and verve in their culture that attracts us even today, across a time lapse of 2,500 years. No other culture ever had the spark of that of the Greeks, and part of the reason was that there was no Greece, really, only a thousand Greek city-states, each with its own government, its own customs, its own form of living, loving, worshiping, and dying. As we look back on the days of Greece, the brilliance of Athens tends to drown out the rest, but each town had something of its own to contribute. The endless variety that resulted gave Greece a glory that nothing before or since has been able to match; certainly not our own civilization of humanity-en-masse.

The null-g's may be the Greeks all over again. A thousand worlds, all with a common history and background, and each with its own way of developing and expressing that history and background. The richness of life represented by all the different null-g worlds may far surpass what is developed, by that time, on an earth rendered smaller and more uniform than ever by technological advance.

(ed note: though Asimov also pointed out that Greek City States had other problems.)


It's not crazy dreams. It's not even Far Out. It's only basic engineering, and some economics, and a bit of hope. I may even have been too conservative. It probably won't take a hundred years.

Given the basic space civilization I've described, we'll have accomplished one goal: no single accident, no war, no one insane action will finish us off. We won't have to have outgrown our damn foolishness to insure survival of the race. Perhaps we'll all be adults, mature, satisfied with what we have, long past wars and conflicts and the like; but I doubt it. At least, though, there will be no way to exterminate mankind, even if we manage to make the Earth uninhabitable; and it's unlikely that any group, nation, or ideology can enslave everyone. That's Worth Something.

One suspects, too, that there will be an enormous diversity of cultures. Travel times between various city-states-asteroid, Martian, Lunar, O'Neill colony, Saturnian forward base, Jovian Trojan Point—will be weeks to months to years with presently foreseeable technology. That's likely to change, but by the time the faster travel systems are in widespread use the cultural diversities will be established. Meanwhile, communication among all the various parts of the solar system will be simple and relatively cheap, so that there will have been that unifying influence; cultures will become different because people want to be different, not because they don't know any better.

OK. In 100 years we'll have built a space civilization. We'll no longer have really grinding poverty, although there will undoubtedly be people who consider themselves poor, just as we have today people who live better than the aristocrats of 1776, but who think themselves in terrible straits. We'll have insured against any man-made disaster wiping out the race.

From THAT BUCK ROGERS STUFF by Jerry Pournelle (1976)

The Ganapati was a new habitat founded by an alliance of two of the Common­wealth's oldest patrician families. It was of standard construction, a basaltic asteroid cored by a gigawatt X-ray laser and spun up by vented rock vapor to give 0.2 gee on the inner surface of its hollowed interior, factories and big reaction motors dug into the stern. With its AIs rented out for information crunching and its refineries synthesizing exotic plastics from cane sugar biomass and gengeneered oilseed rape precursors, the new habitat had enough income to maintain the interest on its construction loan from the Commonwealth Bourse, but not enough to attract new citizens and workers. It was still not completely fitted out, had less than a third of its optimal population.

Its Star Chamber, young and cocky and eager to win independence from their families, had taken a big gamble.

The (gamble) might have failed almost as soon as it begun, but potentially it might win the Ganapati platinum-rated credit on the Bourse. Margaret and the rest of the science crews would, of course, receive only their fees and bonuses, less deductions for air and food and water taxes, and anything they bought with scrip in the habitat's stores; the indentured workers would not even get that. Like every habitat in the Commonwealth, the Ganapati was structured like an ancient Greek Republic, ruled by share-holding citizens who lived in the landscaped parklands of the inner surface, and run by indentured and contract workers who were housed in the undercroft of malls and barracks tunnelled into the Ganapati's rocky skin.

On the long voyage out, the science crews had been on minimal pay, far lower than that of the unskilled techs who worked the farms and refineries, and the servants who maintained the citizens' households. There were food shortages because so much biomass was being used to make exportable biochemicals; any foodstuffs other than basic rations were expensive, and prices were carefully manipulated by the habitat's Star Chamber. When the Ganapati reached Enki and the contracts of the science crews were activated, food prices had increased accordingly. Techs and household servants suddenly found themselves unable to afford anything other than dole yeast. Resentment bubbled over into skirmishes and knife-fights, and a small riot the White Mice, the undercroft's police, subdued with gas. Margaret had to take time off to bail out several of her crew, had given them an angry lecture about threatening everyone's bonuses.

From REEF by Paul McAuley (2000)

In fact, it’s so difficult and expensive that, once you’re in space, it might make more sense to just stay there.

Landing on alien planets might not be worth doing unless you plan to settle there permanently. Instead, you could wander through space, harvesting all the resources you need from asteroids and comets and perhaps smaller planetoids like the Moon.

That brings us to the world of ancient thalassocracies. Thalassocracies are empires of the sea, as opposed to traditional land empires. The word is Greek for “rule of the seas.”

Well known examples include the Phoenicians, Athenians, and Carthaginians. The British Empire might also be described as a thalassocracy, except the British controlled a lot of land in addition to most of the world’s waterways.

Traditional thalassocracies possessed enormous navies. They rarely bothered waging war on land, preferring instead to exert their military power through piracy, naval blockades, and near unrivaled dominance of maritime trade routes.

I’m guessing that space-faring societies will end up behaving more like ancient thalassocracies than modern nation-states. This might be especially true for space-faring civilizations still early in their development and still struggling with the high costs of takeoffs and landings.

(ed note: I'm thinking this would also apply to mobile asteroid bubble space habitats who threw their weight around. They would have an advantage over planet-based civilizations since the thalassocrats are at the top of the gravity gauge. Thalassocracies can be examples of hydraulic states if they control access to spaceflight and interstellar trade.)

From SCIENCY WORDS: THALASSOCRACY by James Pailly (2015)

(ed note: discussion of Bussard ramjets omitted. The ramjets would be mounted on space habitats to make generation starships. He does believe in the now discredited idea that the magnetic field of a Bussard Ramjet can instantly kill all life on Terra.)

Now that we have the ships let us deal with the warriors and their society. If we assume one system trying to rule another, we have to have some reason for the society to send its sons across many light years (and more real years) to overcome the people of another. Aliens will have their own, alien reasons for doing this. As for humans, idealism, power-lust, need for resources, flight from disaster, or the desire to keep the status quo may cause interstellar invasions.

For instance, the citizens of nearby inhabitable stars hear that the residents of Sol System are going to erect a Dyson Sphere around their system to trap as much energy as possible. This troubles the nearby colonists, who fear that the power produced may go into a blackmailing gamma-ray laser which could reach across interstellar distances to nova suns. An armada is gathered...

The inhabitants of these systems would have some trouble manning their fleets, however. For while relativity would keep the voyager younger than his compatriots back home, you're still spending decades away from home. Hopefully there will be enough Idealists, Militarists, Patriots, and Tourists to man the fleet.

As for an occupation army, you could manage it as long as it was as much a colonization effort as an army. The settler/soldiers, in the midst of an unfriendly land, would tend to be more loyal to the homeland than to the conquered system, but matters would not remain so forever. Eventually they'd feel themselves to be members of the conquered system, and their loyalty would shift to themselves.

The situation may be helped by doubling or tripling the human life span, and thus encouraging a slowly-progressing society at home which could be left for thirty years and still be easily acclimatized to on return.

Nevertheless, an interstellar empire of any size using these methods will not be large, if only due to time lag. If a successful revolt occurred on a colony planet 10 light years away from the fuling system, it would take the rulers 10 years to hear about it and 10 years to send a punitive expedition. This gives the revolting system 20 years at the least to prepare for the counter attack.

Even if systemic rule is difficult or impossible, it may be that rule by a starship people may not be so difficult. Robert Silverberg and Poul Anderson have both written of a people who live out their lives in their ships, carrying the interstellar trade, and seeing many civilizations rise and fall as relativity slows their aging. Such a people could control interstellar trade and, if they wished, even the immediate space around the system.

If they controlled interplanetary space they'd control the planets within it, for shooting up against the pull of gravity is much more difficult than shooting down. Even a planet with no big cities to nuke is vulnerable. All the ship people have to do is turn on their ramfield, and every animal (living on the planet that is more highly evoloved than a) paramecium dies.

(ed note: it is no longer thought that Bussard ramjet fields can kill a planet. But being at the top of the gravity gauge is still quite the decisive military advantage.)

Using the resources of one system a ship people can build another fleet of their tribe, and send it out to conquer another system.

Their deployment in a system would have a star-ship and several systemic spaceships orbiting every inhabited planet, several military starships and systemic spaceships farther out as safeguards in case a revolt should destroy the guard ships, and, yet further out, the home ships of the tribe with escorts. If a successful revolt should occur, these would head for friendlier territory controlled by relatives or allies. As one successful revolt could spark others, they'd probably send forces.

The rule of a star tribe would necessarily be light, as cultural differences and the difficulty of maintaining a garrison on those dirty, disease-ridden, overgravitied planets would work against tight rule. They'd encourage the development of spatial resources and interstellar trade, which they would control the transportation for. Some systems could maintain a precarious independence, but on the whole I see little to stop the star tribes from expanding over the Galaxy. Each ship-family and each little tribe would have a very stable culture (as in Heinlein's "Citizen of the Galaxy") so that a trading voyage by a family will not doom it to the difficulties of culture lag. Eventually all human space (and beyond) would be ruled by many tribes of one people who would certainly have to cooperate with each other against the Flatlanders, the Fraki (Heinlein's Citizens of the Galaxy), the Groundhogs who would certainly attempt in places to overthrow their hold.

From INTERSTELLAR WAR by Scott Rusch, The Space Game issue #5 (1976)

(ed note: the Munditos are L5 colonies set in the asteroid belt (paired spinning habitats about 50 kilometers long, set inside conical mirrors). They are owned by their founding nation and must pay taxes. They are protected by military ships from their founding nation. Mundito Rosinante becomes independent, and decides to build a huge laser, energized by sunlight from the mirrors. Later they use the laser to power a large high-deltaV laser thermal rocket.)

“Suppose we are preparing to defend against a future missile attack, like the one just past. Have you any ideas? I mean it's a little late to be brainstorming once the missile is on its way."

"We might build a big laser,” he said at last. “I mean a really big laser, Governor, say 50 meters by 10,000 meters, or even 20,000. Nothing ultra-hot like the Navy uses, but continuous, you know? Pump it with the big mirrors."

"Navy weapons doctrine calls for a power source to generate light, the hotter the better. We have the big arrays of mirrors for light. No need to use a middleman, as it were. We just build a cool, continuous gas laser, but very, very big. It ought to have an effective range of maybe 200,000 kilometers, and it could pick off a missile like nothing, don't you know?"

"What about your idea to maximize the light density by using only one of the three colors of light our mirrors reflect?"

"We've worked out the system for the green light best,” said Ilgen, running his hand over his crew cut. “We have that stack of mirrors—the red and blue mirrors left over from the quality-control work on making the big array—could we use them? How many do we have?"

"The red and blue combined? Maybe 60 or 70 hectares,” said Skaskash. “That would give us a working length of maybe 16 kilometers. I think we really need 21 or 22."

"Yes, 22 would take all the green light from one of the frustrums on the Don Q array-if we patched it up. But what about the cooling?"

“Hey! Skaskash! If we built a pressurized jacket, oh, say one kilometer in diameter, the laser would be air-cooled except for the face, which would be silica! Then we could run a higher light-density and 16 kilometers would be enough! Hell! We could do it with 10!"

"After the event, I ordered high-resolution pictures taken from Laputa."

"This is the double frustum of Don Quixote during the cleanup,” she said, turning the print over. “This is almost the same view taken on January 20, showing the construction in the right-hand frustum in the interim. The technicians call it the Purple Shaft. Notice the support system, which can rotate the shaft in two planes. I imagine that if it was aimed at an object on the other side of the mirror array, a few of the mirrors could be removed."

"This is an enlarged view of the same scene. It shows the Purple Shaft very clearly. We estimate that it is 1020 meters in diameter, 17,230 meters long. The outer surface is made of salvaged purlin tile mounted in salvaged purlin frames. The faint diamond pattern shows quite clearly."

"It doesn't look purple at all,” said Hulvey. “Why do they call it the Purple Shaft?"

"This is the device in operation,” she said. “A very short exposure time shows the inner structure vividly. It is a tube twelve or thirteen meters in diameter running the length of the structure. It is evidently covered with red and blue layered mirrors, so that it reflects purple light and passes green light into the gas mixture which the inner tube contains. In effect, you are looking at a huge gas laser pumped by an array of mirrors having an area of thousands of square kilometers."

"The radiation data is consistent with methyl isopropyl mercury and carbon dioxide,” she replied, “but we don't know.”

"Is it using the full power of the mirror array?” Hulvey asked.

"No, on that shot they were using 30 percent,” she said. “We took a picture of the mirror, and had the computer calculate the angle of each mirror in the array. It gave us a false-color developed picture.” She pulled a print out of the pile. “Yellow is aimed at the laser, the red and red-purple are not. The little green rectangle was probably being used for something else."

"Could they use the full power of the array to pump the laser?” asked Admiral Vong.

"They've had it as high as 80 percent,” she said. “That is, we've seen them take it as high as 80 percent. It is a formidable weapon."

"Rosinante has honored their agreement,” said Shinaka. “We have received their technical data for building the heat ray.

"This heat ray,” said Shinaka, gesturing with his chopsticks, “it is a most troublesome thing. Why couldn't we have invented it ourselves so we could have suppressed it?"

"It is implicit in the design of the Dragon Scale Mirror,” said Kogo. “I expect the reason we didn't invent it was because we consciously decided not to.” He ate a piece of tuna.

"I was with the Dragon Scale Mirror project as a senior team manager back in ‘23 when it was getting started,” Kogo went on, “and the feature that most troubled the Admiralty at that time was the capability to use the mirror array as a defense against docking ships."

"A short-range defense only,” said Shinaka. “Why were they troubled?"

"A city wall is a short-range defense,” replied Kogo, wishing he could light up a cigar, “but when a city builds such a wall it may suddenly become more adventuresome in its foreign policy. The Admiralty feared the drift away from the Central Government. The habitats lend themselves to autarky very naturally. If they also become defensible, like castles, how will we be able to collect our taxes? The big laser was considered in that context, and we never went ahead with it because the Admiralty was afraid that such a powerful weapon in the hands of the habitat managers would make them impossible to control. That is what bothers you now, isn't it?"

"Yes,” said Shinaka, eating a piece of octopus. “It diminishes our warships, also. Perhaps that bothers me even more."

"It does not matter,” said Kogo, “the heat ray is there. Either we use it to advantage or we do not, but we cannot make it disappear. Consider that to use it one must have the Dragon Scale Mirror—which is standard on Japanese habitats, while only a small number of non-Japanese habitats have them. If we use it, we will have a significant military advantage for a significant length of time.” He smiled, showing his lower teeth. “I say build it!"

"It is true,” conceded Shinaka, taking a fresh slice, “we would achieve a transient advantage with the device. What did you have in mind?"

"Use it to free our Navy from defending fixed and scattered points,” said Kogo, “so that we can concentrate our forces for a decisive victory!"

"The last time we did that was when we developed the Zero fighter plane at the beginning of World War II,” said Shinaka. “What happens afterward?"

"Right now I am concerned that the Japanese are building big laser prototypes at (Japanese asteroid colonies) Eije-Ito and Tanaka-Masada."

"Defensive weapons, pure and simple,” Lady Dark said. “How can you worry about them?"

"Up till now it was the Japanese Navy that provided the de facto protection,” said Corporate Susan. “Being released from that detail, they are now free to roll around the Solar System like loose cannon. I wouldn't be surprised to find (our home) Rosinante in their path."

"Perhaps you do not know, Captain. Please do not take offense, but Premier Ito felt that civilian control of the Imperial Japanese Navy would be weakened by building the big lasers. So in pursuit of this policy, what was done? The hijacking of the Foxy Lady was arranged, to prevent the completion of the Dragon Scale Mirror at NAU-Ceres I. Why? The NAU might build a big laser there, and then Japan would also have to build big lasers.” The image of Corporate Hulvey smoothed its slate-blue kimono. “Perfectly logical. If we did, then you must. You might call it prophylactic piracy. Why do you suppose that the NAU might want the big lasers at NAU-Ceres I?"

"To protect their gold shipments against piracy,” No-rigawa said, sipping his tea. “I, myself, have taken over two million ounces. In time, we would have taken the mines."

"Quite so,” the computer said. “Premier Ito was already unable to control his navy. And to execute his policy, a policy designed to avoid losing still more control, on whom must he rely? That same navy, of course. It has taken time, but I have learned that the order to hijack the Foxy Lady came from the office of Admiral Hideoshi Kogo. Would it surprise you to learn that Admiral Kogo is the leading proponent of building big lasers on Japanese space stations?"

From LONG SHOT FOR ROSINANTE by Alexis Gilliland

From the carousel's hub Volyova and Hegazi rode a housesized elevator down one of the wheel's four radial spokes, their weight mounting until they reached the circumference. Gravity there was Yellowstone normal, not perceptibly different to the standard Earth gravity adopted by Ultras.

Carousel New Brazilia orbited Yellowstone every four hours, in an orbit which meandered to avoid the “Rust Belt"—the debris rings which had come into existence since the plague. It had a wheel configuration: one of the commonest carousel designs. This one was ten kilometres in diameter and eleven hundred metres wide, all human activity wound on the thirty-kilometre strip around the wheel. It was sufficient size for a scattering of towns, small hamlets and bonsai landscape features, even a few carefully horticultured forests, with azure snowcapped mountains carved into the rising valley sides of the strip to give the illusion of distance. The curved roof around the concave part of the wheel was transparent. rising half a kilometre above the strip. Metal rails were fretted across its surface, from which hung billowing artificial clouds, choreographed by computer. Apart from simulating planetary weather, the clouds served to break up the upsetting perspectives of the curved world. Volyova supposed they were realistic, but having never seen real clouds with her own eyes, at least not from below, she could not be wholly sure.

They had emerged from the elevator onto a terrace above the carousel's main community, a collision of buildings piled between stepped valley sides. Rimtown, they called it. It was an eyesore of architectural styles reflecting the succession of different tenants which the carousel had enjoyed throughout its history. A line of rickshaws waited at ground level, the driver of the closest quenching his thirst from a can of banana juice which sat in a holder rigged to the taxi's handlebars. Hegazi passed the driver a piece of paper marked with their destination. The driver held it closely to his black, close-set eyes, then grunted acknowledgement.

From REVELATION SPACE by Alastair Reynolds (2000)

Space Colony Problems

Air Is Not Free

Habitable planets are great! Inhabitants have quaint expressions such as "Free as Air!"

In space, there ain't no free breathing mix. Any breathable air you consume is either brought along or is manufacturing out of local resources. Neither of which is free, or even inexpensive. Air costs money. If you want to breathe, you have to pay.

With interplanetary tourists, the "air tax" is included in the fee for their tour package. People living in a space station have to pay their periodic air tax or suffer the consequences. This is why a space habitat is a particularly pure example of a hydraulic state. Obey the people who control life support, or you'll find yourself suddenly trying to learn how to breath vacuum.


"Yes, the wording is such that the boycott will affect all space commerce activities carried on by the Commonwealth and its registered space facilities," Trip Sinclair observed, "even the League of Free Traders, Kevin."

"How about our Lagrangian operations?" Ursila Peri's video image wanted to know. "How can they boycott trade operations off-planet?"

"Is your air bill current, Ursila?" Trip asked her.

"Yes, but even if it wasn't, nobody out here would cut off another person's life support. If the credit line got over-extended too much for too long, we'd put the debtor on a ship home. We work together because there's a lot of nothing waiting for everybody beyond the bulkhead," she said. "They're going to have trouble enforcing tariff arrangements and trade boycotts out here, that agreement sounds exactly like something written up by a bunch of people who always have pressure around them and gravity to keep their feet on the floor. Earthworms!" She made it sound like an insult.

"Sandy, this is Jeri Hospah. Don't let his attempts at humor put you off; sometimes he means what he says. Jeri, find a sack for Sandy and issue him some chits. Then fake up some paperwork that will keep the Ell-Five people happy," Ali instructed us...

...Uncountable hours later, I awoke in the wan sleeping light of the personal compartment and was momentarily confused until I remembered where I was. I felt physically refreshed but still mentally fatigued. That's a dangerous condition in space because little things can kill a careless person.

Somebody had left a flight suit and a Remain-Over-Night kit. Jeri Hospah was either thoughtful or had a well-trained station crew. I took a sponge bath, put on the flight suit and slippers, and decided I might live if I could find breakfast.

The RON kit had a pack of chits—air, meal, water, airlock cycles—as well as an L-5 facilities directory and a visitor's card for the Free Traders' Lounge.

A note was in the kit. "Call me at 96-69-54 and I'll chit you breakfast—Jeri."

From MANNA by Lee Correy (G. Harry Stine) (1983)

(ed note: the superintendent explains the facts of life to the new voluntary exiles to Mars. Keep in mind that on Mars, the air you breath is NOT free, it has to be manufactured and you have to pay for it.)

     "Hear and believe," Farr said. "Okay, chums, let me give you the facts of life. Number one. Don't try to escape. There's no place to go. If you make it outside, you'll live about fifteen seconds. There's no air out there, and your blood will boil away in your veins. It's not a pretty way to go, and I'm told it's painful as hell.
     "Number two. Don't try to escape. You may think you're smart and see a way to get a p-suit. You may even be able to operate it. And then what? You can't make air, and you can't carry enough to get anywhere worth going. Running out of air's not a lot better than going out without a suit.
     "Number three. Don't try to escape. Sure there's a town here, and sure there are a lot of people in it. But you'll pay for everything, and I do mean everything."
     He lifted an orange disk that hung from a chain around his neck. I'd noticed that everyone except us newcomers wore one, but they weren't all the same color. "Air-tax receipt," Farr said. "Mine's orange because I'm due to have it recharged. If it turns red, that's it. Pay up or go outside. You'll need air medals, because God help you if anybody catches you in town without one."
     "Why? What happens?" someone demanded.
     "Outside," Farr said. "Not even a chance to pay up. Just out."
     "And who's to put me out?" Kelso demanded.
     Farr grinned. "Every man jack who's paid his taxes, that's who. Might take several for you, but they'll do it."

At Central Processing they charged our air tags to bright green, forty days' worth. They gave us a hundred Mars dollars, worth about half that in Federation credits. We changed our coveralls for new ones, with a choice of blue or orange.

I found a tunnel end to sleep in. They'd been digging out to expand the city, but this project was halted for lack of a labor force. Nobody bothered me. I figured I had nothing worth stealing, anyway. That turned out to be stupid: I had a charged air tag, and that would be worth my life if there was anybody around desperate enough to cut my throat for it. Nobody was, just then.

I'd been there ten days and my air tag was turning from green to yellow, It was getting time to move on. I figured another couple of days would do it.

From BIRTH OF FIRE (collected in Fires of Freedom) by Jerry Pournelle (1976)

     "Okay, "Miller said. "What's my contract?"
     "Find Julie Mao, detain her, and ship her home."
     "A kidnap job, then," he said.
     Miller stared down at his hand terminal, flicking the files open without particularly looking at them. A strange knot had tied itself in his guts. He'd been working Ceres security for thirty years, and he hadn't started with many illusions in place. The joke was that Ceres didn't have laws—it had police. His hands weren't any cleaner than Captain Shaddid's. Sometimes people fell out airlocks. Sometimes evidence vanished from the lockers. It wasn't so much that it was right or wrong as that it was justified. You spent your life in a stone bubble with your food, your water, your air shipped in from places so distant you could barely find them with a telescope, and a certain moral flexibility was necessary. But he'd never had to take a kidnap job before.
     "Problem, Detective?" Captain Shaddid asked.
     "No, sir," he said. "I'll take care of it."
     "Don't spend too much time on it," she said.

     "Okay," Havelock said. "I'm sorry, but I'm missing something here."
     "What?" Miller said. He meant What are you yammering about? Havelock took it as What are you missing?
     "A water hauler millions of klicks from here got vaporized. Why are we going to full alert? Our cisterns will last months without even going on rationing. There are a lot of other haulers out there. Why is this a crisis?"
     Miller turned and looked at his partner straight on. The small, stocky build. The thick bones from a childhood in full g. Just like the (Earther) a-hole in the transmission. They didn't understand. If Havelock had been in this James Holden's place, he might have done the same stupid, irresponsible, idiotic bullsh*t. For the space of a breath, they weren't security anymore. They weren't partners. They were a Belter and an Earther. Miller looked away before Havelock could see the change in his eyes.
     "That ***** Holden? The one in the broadcast?" Miller said. "He just declared war on Mars for us (nation of Ceres)."
     The cart swerved and bobbed, its internal computer adjusting for some virtual hiccup in the traffic flow half a kilometer ahead. Havelock shifted, grabbing for the support strut. They hit a ramp up to the next level, civilians on foot making a path for them.
     "You grew up where the water's maybe dirty, but it falls out of the sky for you," Miller said. "The air's filthy, but it's not going away if your door seals fail. It's not like that out here."
     "But we're not on the hauler. We don't need the ice. We aren't under threat,"
     Miller sighed, rubbing his eyes with thumb and knuckle until ghosts of false color bloomed.
     "When I was homicide," Miller said, "there was this guy. Property management specialist working a contract out of Luna. Someone burned half his skin off and dropped him out an airlock. Turned out he was responsible for maintenance on sixty holes up on level thirty. Lousy neighborhood. He'd been cutting corners. Hadn't replaced the air filters in three months. There was mold growing in three of the units. And you know what we (the police) found after that?"
     "What?" Havelock asked.
     "Not a goddamn thing, because we stopped looking. Some people need to die, and he was one. And the next guy that took the job cleaned the ducting and swapped the filters on schedule. That's what it's like in the Belt. Anyone who came out here and didn't put environmental systems above everything else died young. All us still out here are the ones that cared."
     "Selective effect?" Havelock said. "You're seriously arguing in favor of selective effect? I never thought I'd hear that sh*t coming out of you."
     "What's that?"
     "Racist propaganda bullsh*t," Havelock said. "It's the one that says the difference in environment has changed the Belters so much that instead of just being a bunch of skinny obsessive-compulsives, they aren't really human anymore."
     "I'm not saying that," Miller said, suspecting that it was exactly what he was saying. "It's just that Belters don't take the long view when you screw with basic resources. That water was future air, propellant mass, and potables for us. We have no sense of humor about that sh*t."

From LEVIATHAN WAKES by "James S.A. Corey" (Daniel Abraham and Ty Franck) 2011.
First novel of The Expanse


"Lurker" is a homeless destitute person living on a space station, especially a space colony. The person figures there are opportunities on the colony, they spend most of their money traveling to it, when they can find no jobs the money runs out, so they have no money for a space flight ticket to somewhere else. They then move to anyplace they can find in the station, much like terrestrial homeless live under bridges. The space colony administrators cannot afford to ship the lurkers elsewhere (there are so many of them), so the problem grows. Of course the lurkers are also preyed upon by the criminal underworld.

Michael Hutson pointed out to me that this actually happens in places like Hawaii, which require lots of money to leave. The destitute tend to accumulate in Hawaii since they cannot afford the air fair to leave and go somewhere else. And the Hawaiian government certainly cannot afford to give them free plane tickets.

Roger MacBride Allen has a simple solution, assuming the station controls all transport to the station.

The term was invented by J. Michael Straczynski for his TV series Babylon 5, more accurately he adapted an existing term. In internet forums "lurkers" are people who read the forums but do not make posts or otherwise draw attention to themselves. Straczynski noticed this phenomenon when he was discussion the proposed TV show on GEnie, Compuserve, and Usenet back in the early 1990's. He thought the invisible forum lurkers were a good metaphor for the invisible homeless people on the Babylon 5 space station.


Immigration should do something

     “Spare change, brother?”
     “Get a job!”
     “That’s quite impossible.”
     “Impossible: adj.: not possible; unable to be, exist, happen, etc.”
     “A wise guy, eh?”
     “Yeah. Everybody out here has an IQ over 110. ‘Cept you, ‘parently.”
     “Why, I never!”
     [sighs] “We’re all descended from Earth, one way or another, but the smartest all moved out to space. So us second- and third-gen folks are all the sons and daughters of the upper-bracket erudite–including a fair measure of genius. The funny thing about IQ is that 100 is always average, so the average Earther is 80-something and the average Belter is 120.”
     “I take grave exception to–”
     “Oh can it already. Where are you going anyway?”
     [testily] “… Bureau of Careers. Just shipped in with my last dime.”
     [sarcastically] “And may lady fortune herself light your path to employment.”
     “I will too!”
     “Nope. Yer too dumb. If I can’t get a job, then you sure as hell can’t get a job. And you’re in the same boat as I–without any cash, you can’t buy your way off this rock. Might as well take a seat next to me. Yer gettin’ no job, brother.”

From SPACE BUMS by Ian Mallett (2016)

(Journalist Cooper travels to the Lunar colony to do some investigative reporting, attempting to discover the secret that the scientists won't talk about. Spoilers for the story follow.)

Then Cooper whispered: "My God— you've found a way of prolonging life!"

"No," retorted Hastings. "We've not found it. The Moon has given it to us ... as we might have expected, if we'd looked in front of our noses." He seemed to have gained control over his emotions—as if he was once more the pure scientist, fascinated by a discovery for its own sake and heedless of its implications.

"On Earth," he said, "we spend our whole lives fighting gravity. It wears down our muscles, pulls our stomachs out of shape. In seventy years, how many tons of blood does the heart lift through how many miles? And all that work, all that strain is reduced to a sixth here on the Moon, where a one-hundred-and-eighty-pound human weighs only thirty pounds."

"I see," said Cooper slowly. "Ten years for a hamster—and how long for a man?"

"It's not a simple law," answered Hastings. "It varies with the size and the species. Even a month ago, we weren't certain. But now we're quite sure of this: on the Moon, the span of human life will be at least two hundred years."

"And you've been trying to keep it secret!"

"You fool! Don't you understand?"

"Take it easy, Doctor—take it easy," said Chandra softly.

With an obvious effort of will, Hastings got control of himself again. He began to speak with such icy calm that his words sank like freezing raindrops into Cooper's mind. "Think of them up there," he said, pointing to the roof, to the invisible Earth, whose looming presence no one on the Moon could ever forget. "Six billion of them, packing all the continents to the edges—and now crowding over into the sea beds. And here—" he pointed to the ground—"only a hundred thousand of us, on an almost empty world. But a world where we need miracles of technology and engineering merely to exist, where a man with an I.Q. of only a hundred and fifty can't even get a job.

"And now we find that we can live for two hundred years. Imagine how they're going to react to that news! This is your problem now, Mister Journalist; you've asked for it, and you've got it. Tell me this, please—I'd really be interested to know—just how are you going to break it to them?"

He waited, and waited. Cooper opened his mouth, then closed it again, unable to think of anything to say. In the far corner of the room, a baby monkey started to cry.

From THE SECRET by Sir Arthur C. Clarke (1963)

(ed note: Garrison and Ben are at the Lunar Central colony, and have to travel to the remote isolated Farside station. Tickets for roller (Lunar tractors) transport to Farside are outrageously expensive. Ben has a better idea, buy their own second-had roller.)

“First off, two round-trip tickets overland to Farside cost nearly a third of what a used roller costs. There’s a glut on the market for some reason. Second, the prices for cargo shipment are even more ridiculous. Then I checked on the price of temporary accommodation out there at Farside. Insane. If we spent a month in a rented room out there then we’d have paid for the other two-thirds of the roller. But if we live in the roller until we find a permanent place to live, we’ll save plenty.”

“If the seals on the roller don’t give out and vent our air,” Garrison agreed. Something occurred to him. “Why did you check on the price of round-trip tickets, anyway? One-way is all we need.”

“And round-trip is all they sell. The story is that it's a limited-resource area, whatever the hell that means, and they can’t afford to clutter up the stations life-support system with poor slobs who spend their last buck getting out there and strand themselves. In real life, of course, they make more money selling return tickets. So I spend a roller instead and they don’t get any money at all.”

(ed note: Yes I know this is for Lunar tractors, but the principle can be applied to spacecraft tickets to a space station. Obviously this assumes that the space station can force the spacecraft passenger liners to cooperate.)

From FARSIDE CANNON by Roger MacBride Allen (1988)

A lurker is a term used for the homeless on Babylon 5.

Lurkers are mostly human although others have been seen. They began settling on the station as soon as it was opened, beginning simply as people searching for new lives and opportunities. When they did not succeed, they often don't have the money to go back home so they end up moving into the undeveloped parts of Downbelow. There are also those that are destitute because they are on the run from something or someone, like the Psi Corps. Lurkers have hard lives to say the least and as if being poor and homeless wasn't bad enough, they often become victims of the criminal underworld that robs and steals from them. However, there have been situations where they are hired by smugglers etc. to handle illegal cargo.

In 2261 during Babylon 5's state of independence from Earth, Captain Sheridan instituted work programs so that they could earn money.


Downbelow refers to the various undeveloped areas of Babylon 5, mostly in the lower levels of Brown Sector near the outer hull. Very few ever go there, as it consists of the corridors and chambers around the waste recycling system, the air compressors, and the water reclamation facility.


Downbelow came about as a result of budgetary cutbacks and a rush to finish when construction was nearing completion, leaving many areas of the station unfinished, especially in the Brown and Grey sectors. Being the first station of the much-touted Babylon Project to open for public residency, people flocked to the station in search of a better life. However, many who came to the station didn't find their better life, soon ran out of money, and were reduced to squatting and living in the abandoned corridors of those unfinished levels, scrounging through the refuse of the hurried construction process for anything they could eat, wear, or sell. Due to this style of living, they became known as Lurkers.

In 2258 Dr. Stephen Franklin set up a free clinic in Downbelow to help treat those in need that couldn't afford to go to Medlab and to secretly sort runaway telepaths and get them out through the Underground Railroad.


Downbelow is a hotbed of crime and accounts for as much as 90% of the station's crime rate, mostly because it's the only place for many people to go when they come to the station looking for a new life, but run out of money, unable to buy passage home, effectively becoming the station's homeless. The very worst parts of Downbelow are located in Brown Sector, which is a less than pleasant locale at the best of times. Downbelow is often divided up between an ever changing roster of various criminal factions, small-time thugs and gangsters. Most are little more than violent bullies that have learnt to survive by stealing, intimidation, protection rackets and extortion. Even the secretive Thieves Guild have a presence in this area.


Society Rules

The rules and societal norms on a space habitat are going to be different than here on Terra.

In the Albedo Anthropomorphics universe of Steve Gallacci, one has a cluster of planets colonized by slower-than-light starships (yes, the colonists are furry anthropomorphic animals, but that is beside the point). The planetary cultures that were founded as a consequence have a "shipboard discipline mentality."

Consider, on a spacecraft, if a civilian saw something like an air leak in the hull, and didn't report it to anybody, they would be endangering not only their own life but also the lives of everybody on the colony ship. So that is a crime.

In the United States on the other hand, if a person sees somebody lying injured on the side of the road, and they try to help the injured one, more often than not they wind up being sued by the injured person. Hands off, do not get involved, it is not your problem.

In the Albedo universe, with the shipboard discipline mentality, it is a crime not to try and help somebody who is injured, and there are "Good Samaritan" laws to protect the helpers.

Naturally such a shipboard discipline mentality will rule a society living inside a space habitat, since such a habitat is pretty much a huge spaceship. Even more so, a civilian not bothering to report an air leak on a habitat is endangering many more people than on a spaceship. By several orders of magnitude.


The closest thing to social tradition available to the people of ALBEDO is shipboard discipline, and this is strongly ingrained in all levels of society. Simply stated, the individual member of society is not quite as "free" (in one sense of the word) as a 20th century western man, because the individual is strongly constrained by a set of expectations and responsibilities. The individual is expected to be an active citizen, and is conceived of as having both civil liberties and responsibilities. The fragile ecological and social environment on board colonisation ships has lead to the development of societies where the individual is expected to take his social role very seriously, and to contribute to the working of things around him. The individual is expected to behave in an intelligent, responsible manner, and to be aware of the implications of his or her actions. Citizens are expected to be aware of the long running consequences of their actions, and to act accordingly.

Thus in most cultures, if a person is injured, it is the civil duty of passers-by to assist that person however possible. If a passer-by refuses to aid the injured party, or pretends to ignore them, then the passer-by is held to be partly responsible for the subsequent condition of the injured man, and will be charged under law accordingly. Regional attitudes do vary, however. For instance, to the inhabitants of the Dornthant system, the tools of an ordered and peaceful society are its security measures, and the co-operation of the common citizen is an expected duty. To a Dornthantii, running away from or obstructing the authorities is a clear admission of guilt.

The practical upshot of the social attitudes prevalent in most cultures in ALBEDO is the creation of societies which are very politically and ecologically aware. The average citizens feel that they have a vested interest in the running of their government, their society and their planetary environment. Albedo is set in an age of REASON, where forethought and responsibility are highly valued faculties. In the context of the culture of known space, "honour" will usually equate as social responsibility.

From ALBEDO RPG PLAYER'S MANUAL by Craig Hilton and Paul Kidd

(ed note: In the future there is a failing Terra and some space colonies of dubious longevity. A bunch of visionaries realize that the colonies are going to fail sooner or later and Terra is on its last legs. A prudent person would take out an insurance policy.

The visionaries sold everything they had, built a generational starship named Redeemer, and departed for Tau Ceti.

Sometime later the space colonies and Terra came to blows and started a war. Terra was nuked, and the colonies were shot full of holes. Now that all human life on Terra has been incinerated, the only survivors of the human race are the colonists. And their DNA has suffered a lot of radiation damage.

Of course there is the Redeemer carrying a cannister full of DNA samples from ten thousand healthy people. But the ship has been on its way for 73 years and is out of reach. Until one of the space colonies invents a faster-than light drive.

A colonist named Nagara gets together a consortium to rent a FTL ship and go steal the DNA can from the Redeemer. He rendezvouses with the generational ship, sneaks aboard, and pulls a gun on the leader.)

      He knew she was playing some game but he couldn’t see why. “You’re carrying DNA material for over ten thousand people. Old genotypes, undamaged. It wasn’t so rare when you collected it seventy-three years ago but it is now. I want it.”
     “It is for our colony.”
     “You’ve got enough corpses here.”
     “We need genetic diversity.”
     “The System needs it more than you. There’s been a war. A lot of radiation damage.”
     “Who won?”
     “Us. The outskirters.”
     “That means nothing to me.”
     “We’re the environments in orbit around the sun, not sucking up to Earth. We knew what was going on. We’re mostly in Bernal spheres. We got the jump on—”
     “You’ve wrecked each other genetically, haven’t you? That was always the trouble with your damned cities. No place to dig a hole and hide.”
     Nagara shrugged.
     “How did the planetary enclaves hold out?” the woman was asking. “I had many friends—”
     “They’re gone.”
     Something came into the woman’s face. “You’ve lost man’s birthright?”  
     “They sided with the—”
     “Abandoned the planets altogether? Made them unfit to live on? All for your awful cities—” and she made a funny jerky motion with her right hand.

     (the Revealer said) “We need the genotypes for insurance. In a strange ecology there will be genetic drift.” 
     (Nagara said) “The System has worse problems right now.”
     “With Earth dead you people in the artificial worlds are finished,” she said savagely, a spark returning. “That’s why we left. We could see it coming.”
     “I know quite well why you left. A bunch of scum-lovers. Purists. Said Earth was just as bad as the cylinder cities, all artificial, all controlled. Yeah, I know. You flatties sold off everything you had and built this—” His voice became bitter. “Ransacked a fortune—my fortune.” 
     For once she looked genuinely curious, uncalculating. “Yours?”
     He flicked a glance at her and then back at Zak. “Yeah. I would’ve inherited some of your billions you made out of those smelting patents.” 
     “I’m one of your great-grandsons.”
     Her face changed. “No.”
     “It’s true. Stuffing the money into this clunker made all your descendants have to bust ass for a living. And it’s not so easy these days.”
     He waved her into silence. “I knew you were one of the mainstays, one of the rich Flatlanders. The family talked about it a lot. We’re not doing so well now. Not as well as you did, not by a thousandth. I thought that would mean you’d get to sleep right through, wake up at Tau Ceti. Instead—” he laughed—“they’ve got you standing watch.”
     “Someone has to be the Revealer of the word, grandson.” 
     “Great-grandson. Revealer? If you’d ‘revealed’ a little common sense to that kid over there he would’ve been alert and I wouldn’t be in here.”
     She frowned and watched Zak, who was awkwardly shifting the squat modular canisters stenciled GENETIC BANK. MAX SECURITY. “We are not military types.”
     Nagara grinned. “Right. I was looking through the family records and I thought up this job. I figured you for an easy setup. A max of three or four on duty, considering the size of the life-support systems and redundancies. So I got the venture capital together for time in a translight and here I am.”
     “We’re not your kind. Why can’t you give us a chance, grandson?”
     “I’m a businessman.”
     She had a dry, rasping laugh. “A few centuries ago everybody thought space colonies would be the final answer. Get off the stinking old Earth and everything’s solved. Athens in the sky. But look at you—a paid assassin. A ‘businessman’. You’re no grandson of mine.”
       “Old ideas.” He watched Zak.
     “Don’t you see it? The colony environments aren’t a social advance. You need discipline to keep life-support systems from springing a leak or poisoning you. Communication and travel have to be regulated for simple safety. So you don’t get democracies, you get strong men. And then they turned on us—on Earth.”
     “You were out of date,” he said casually, not paying much attention.
     “Do you ever read any history?”
     “No.” He knew this was part of her spiel—he’d seen it on a fax from a century ago—but he let her go on to keep her occupied. Talkers never acted when they could talk.
     “They turned Earth into a handy preserve. The Berbers and Normans had it the same way a thousand years ago. They were seafarers. They depopulated Europe’s coastline by raids, taking what or who they wanted. You did the same to us, from orbit, using solar lasers. But to—”
     “Enough,” Nagara said.

From REDEEMER by Gregory Benford (1979)



     One can argue that the success of any revolution, no matter how the "mother country" manages the offworld colonies on any scale, can be answered by these questions:
1) Orbital vs. Planetary
2) Must the infrastructure be captured intact?
     For the first question, many of us have debated and learned over the previous blog entries that orbital colonies are very fragile structures compared to planetary settlements and, as such, far more vulnerable to violent action then their planet-side breatheren. Not to mention the near-dictatorship level of control that is needed to keep orbital habitats functional would make any acts of open rebellion a poor judgement at best.
     The only time a planetary settlement is as close to vulnerable to orbital habitats is if the planetary environment is a very close second to space when it comes to hostility towards human survival. The only difference is in the heat management with convection with either the atmosphere or the ground below, just one of many factors that'll make defense against any reactionary orbital constellation task force sent to qualsh any rebellion.
     Of course, this also depends upon if the political and/or economical reasons for the colony to be intact after military action are present and strongly argued for. If not, well as the old addage goes "bombs away".

From REVOLT OF THE COLONIES by Rick Robinson (2010)

Three Generation Rule

RocketCat sez

The Three-Gen rule just says that Space Colonies Die Because People Are Lazy. Unlike the rest of this website, it ain't rocket science. You disagree? Oh, and I suppose you never ever put off scooping the cat's litter-box "for later?"

As you rapidly discover when thrown out an airlock in your underwear; space has zippo breathable oxygen, atmospheric pressure, lack of broiling heat, and other incidentals you need or you'll die. A Ground-gripper living on a planet take these things for granted, but they ain't in space. Not unless you bring them along.

Which means lots of complicated delicate high-tech life-support equipment. All of which had better get regular maintenance or it breaks down. Which will kill everybody.

Commercial and military space station life-support will get that maintenance, since the owners don't want their expensive investments going kablooey. Well unless there is some serious corruption or mismanagement goin' on, but I digress.

Space colonies on the other paw are full of lazy people who figure they can put off fixing the leaky oxygen generator until next Monday. Keep up that attitude for a few decades and you can bet your last rocket it's just a matter of time before a catastrophic breakdown forces mass evacuation or death. This is much the same mindset you see in cities that keep putting off fixing aging bridges and water supply plumbing. Then the city fathers have the audacity to pretend like they are surprised when beltway bridges fall and pancake a dozen cars or a few city blocks wind up under several meters of water or infested with car-eating sinkholes.

Three-Generation Rule was codified by Ken Burnside. It suggests that space habitats (space stations where people live and raise new generations of children, not commercial or military bases) have an average lifespan of three generations before everybody dies or is forced to evacuate.

You see, unlike living on a habitable planet, there is no air in space. Likewise other life-support requirements that can only be provided by lots of technology. Which must be regularly maintained or it breaks down.

Commercial and military space stations (controlled by exterior corporation or military forces) are much better at keeping up the maintenance than are space habitats (controlled successive generations of lazy people who just live there).


The Three Generation Rule is based off of ibn Kaldun in the 12th Century, and my work on civic planning committees. I noticed when people got involved in the process, and how often it turned into well predicted failure modes because people wanted to extract their profits.

It's feasible to do this (and a bad idea anyway) when your air and water are free. It's less feasible (and still all too common) in desert communities in the US. In a space station? That's going to get people killed. "I Got Mine, Fark Off" isn't a sustainable choice.

from a tweet by Ken Burnside (2019)

Three Generations Rule, The – Human habitats in hostile environments are fragile, and human nature tends towards short term, rather than long-term thinking. Because of this, most hostile environment colonies last for three to five generations, once they cease to be outposts of planetary governments. The second generation tends to make choices based on the here and now, and the third generation pays for them. Strongly autocratic societies tend to last longer, but have a lifespan matched primarily by that of their leader.

Visionaries paint futures of humanity living in space. History has not proven kind to them.

From the disasters in the Mars colonies of the late 21st century to the present, human nature has set a clock on human habitation in a hostile environment. While planets have multiple redundant environmental failure modes, artificial habitats in hostile environments lack them. Worse, human beings are frequently forgetful, lazy, criminally negligent, or outright hostile.

So long as an outside government or agency is continually putting funds into a station, or it’s run as a benevolent dictatorship, these problems can be minimized. When the stations gain a measure of autonomy, and the citizens relax bothersome rules as “unnecessary”, the seeds of tragedy are sown.

The first generation keeps things in good working order, remembering enough of the procedures that they are followed, even when they’re boring, or aggravating, or expensive in the short term. The decline begins when the first children are born: any parent can tell you that a 2 year old is 14 kilos of self-animated entropy and destruction, fully equipped with a curious mind, opposable thumbs and no regard for the consequences of actions.

As the second generation comes into power on its own, the “pioneer” ethic dwindles. Children view many of the choices of their parents in a different light. Long-term needs are postponed for shorter-term gains. Budgets aren’t increased as parts wear out, and attitudes of “You were able to do it last year with this amount, I’m sure you can think of something...” enter decision making processes. Elections accelerate this process because politicians play on the short-term concerns of their constituents. The second generation has children of their own, who teach the same entropic lessons their parents did... often with a few tragic accidents to boot.

The third generation reaps the whirlwind sown by the second generation’s decisions. It has to maintain 50 year old equipment that has seen constant use in a high radiation, oxidizing environment. Rust accumulates in awkward places, plants mutate. Machinery works by cannibalization, duct tape and prayers, while the budget for overhaul shrinks due to taxpayer demand. All the problems previously ignored or partially solved come to a head. Crisis follows crisis follows short-term fix. As soon as the environment becomes uncomfortable, those who can afford to emigrate do so, destroying the tax base for future repairs, and accelerating the process. Eventually, the system collapses: everyone departs, or dies in a catastrophic failure. (Example: in the Corinth station in Epsilon Eridani system, with air and water recycling systems nearly failing, the sanitation workers went on strike. Out of 7,324 inhabitants of Corinth Station, 13 were alive when a rescue freighter arrived.)

The greater the degree of personal autonomy, the faster this cycle runs. The few habitats to defeat this rulehave had a cultlike devotion to a leading cadre or code of behavior, with extensive brainwashing and forced learning, beginning with toddlers, with social codes that make the Bedouins of Earth look sybaritic.


Ken can make authoritative correction of this, but the premise of the 3-gen rule is that the degree of social discipline needed for a space habitat to survive indefinitely is beyond the capability of "normal" human societies. The human tendency to favor short-term expediency will, over time, make the habitat ecosystem more and more precarious.

Putting it loosely, people tend to put off patching the leak in the roof till its raining.

In the Ten Worlds setting, this means that space habs tend to run down, and fail catastrophically in 1-5 generations from when they were established. The average is 3 generations, hence 3-gen rule. The one society in the 10W setting that has beaten this rule is the Library of Man, by adopting a social system that makes it seem very strange and almost "inhuman" to others.

Proviso: This applies only to habs that are socially independent, i.e., the major decisions are made locally, thus subject to local political expediency, etc. It does not apply to bases and such that are ultimately under some outside authority — the outside authority can order the leaks fixed, even if it means everyone has to work double shifts.

Rick Robinson

Alistair “Cerebrate” Young

     Been contemplating the Three Generation Rule, worldbuilding-wise, since reading through the Attack Vector: Tactical Setting Book.
     I'm not a particular fan of the Humans Are Morons trope — I prefer my universes without anyone holding the Idiot Ball, even if it wasn't purely hypothetical — assuming rather that humanity is hovering somewhere around about galactic average for smart.
     But, yeah, those special talents of ours for failing to grasp our enlightened self-interest and having abysmally short planning horizons probably would discourage Our Protagonists from handing us serious long-term projects, yeah.

Ken Burnside

     Even in the Ten Worlds setting (the one described in the AV:T Settings Book), the Three Generations Rule is a median in a range. It's really closer to being a "two-to-six" generations rule, with the primary determinant on longer durations being a VASTLY more communitarian society than is the norm.
     This can be from adaptive societal structures like some varieties of Mennonite faiths all the way over to extensive brainprinting of attitudes along with education to keep things running.
     The Library of Man uses the latter... (An organization dedicated to brokering and selling information throughout the Ten Worlds, they are more like fanatical monks or a cult than they are a colony)

(ed note: Inside the Ten Worlds the Library of Man has space colonies in the otherwise uninhabited star systems of AD Leonis, Epsilon Indi, and 1 Pi (3) Orionis)

Alistair “Cerebrate” Young

     I figured it would work out something like that in practice, and indeed, I can totally believe it where Mark 1 Humans are concerned.
     (But having spent a bunch of time marinating my brain in the inhuman psychology of my main protagonist species — as rampaging a bunch of rabid individualists as ever sat around disagreeing with each other about where, when, and how to rampage — I've got a bunch of characters in my head making snarky remarks about how odd it is that a species that isn't, by nature, nearly so predisposed to libertist fanaticism nevertheless manages to suck so much at cooperating long-term without being indoctrinated to first...
     ...don't mind me, writer syndrome.)

Ken Burnside

     One of the little notes that didn't make it in the setting book is that the frothing Libertarians in the setting tended to be disasters at running contained environment systems...

Alistair “Cerebrate” Young

     Heh. Even as someone with a lot of libertarian inclinations, I can see exactly that. (Mostly because I know too many of the unfortunately dim kind of libertarian.) I imagine quite a few similar things happened at various times and places in my setting, too, for that matter.
     The space libertarians mentioned above, contrariwise, when such a thing happens, have a standard response which amounts to rolling their eyes and world-wearily pointing out that "if you want to have a free and consensual society, you have to be at least an order of magnitude better at managing cooperation and obligation and quote public goods unquote than any of those buggers with governments that can brute-force their way out of the situation; and anyone who thinks that taking away the whips and jackboots abolishes all those things too is obviously Doing It Wrong. Idiot atomists had it coming."
     Then they cut a check to the Ellfive Habitat Systems Management Group and call the Life Support Tech-Adhoc to confirm their required-by-volume-lease 10 am atmosphere-sensor checking appointment, 'cause Mama Versine didn't raise no vacuum-sucking dummy, no sir.

Ken Burnside

     I have never seen any arguments more rancorous than zoning arguments at city council planning meetings.
     The fundamental logical fallacy of a lot of libertarianism is that they can find solutions that won't leave some faction desperately unhappy; the knock-on effect of that is that the people left unhappy tend to carry grudges the next time some dispute needs mediation.
     Government serves a purpose in that it acts as a remove on that animus being personal.

From a comment thread in Google Plus (2014)

Brian Renninger

     Well, IMO, 3-gen rule is more like the Pirate's Code — a guideline. There are ways around it, or at least to extend it. Or, not worry about it. 3-gens is certainly enough time to begin something new. Those in a failing colony will certainly have some incentive to move to greener pastures or make a greener pasture.

Ken Burnside

     If you can sidestep the 3-gen rule on an enclosed habitat, you can sidestep it on a planet, and you won't be moving enough people into space to impede humanity's impact on a planet.
     3 generations is the median, and you can see a 3-gen rule scenario playing out now in Detroit. ("now" meaning "2013")

Brian Renninger

     Ken Burnside, Concur with the idea that if you can avoid it in an enclosed habitat you can avoid it on a planet, thus negating any gains made by making habitats. My comment was more on the rule itself rather than the idea that space habitats are a way of avoiding impacts on Earth.
     I think several of Heinlein's novels touch on this with characters having these particular hopes dashed.

Ken Burnside

     It's largely an historical observation about human nature, political corruption, and the fact that infrastructure maintenance tends to result in fewer jobs than infrastructure construction or renewal.
     On a planet, letting your infrastructure rot results in places like Detroit: The population shrinks over the course of 20 years because everyone moves away.
     On a space station, there's no "away" to move to, and the failure modes tend to be more catastrophic.
     My supposition is that different cultures will have different spots on this curve; I suspect a strongly neo-Confucian culture that taught conformity would be both very alien to modern Westerners, and might be able to make this last longer — but even then, there's going to be a tendency to cut corners, put off fixing things until the next budget cycle, and then some. It largely takes a military organization to, say, keep an aircraft carrier running, and that's only because the people in charge of the aircraft carrier aren't living on it....and if you've read readiness reports for Soviet Navy stuff (or seen the Russians try to get their Navy back into functional status...) you'll see that corruption and graft are even worse there than they are in our Navy.
     The best way to solve this problem is to get rid of people. :)

Mad Fabe

     Ken Burnside, the way around that may be to have drones that go out and fix things before they break.

Ken Burnside

     And who fixes the drones? :) Entropy wins in the end, and (at least at our current understanding of the macrocosmic all), human societies have to allocate resources.
     The record for human beings making sensible long-term allocation of resources for society as a whole isn't great.

Mad Fabe

     Ken Burnside, you are making the case for a computer run society. Kind of like the one in Colossus the Forbin Project.

Ken Burnside

     Both the Bedouin and Inuit live in very simple societies without a lot of amenities or social complexity.
     When presented with complex luxuries, they tend to be even worse at taking care of them than "conventional Westerners."
     Talk to anyone who's had to deal with typical Arab/Bedouin maintenance of vehicles, modern firearms and electronics, they'll back this assertion up.
     Three generations is a long span, and space habitats are fragile, and certain types of maintenance really are more easily done by refurbishing the entire system with it's uninhabited.
     Or, let me put to to you like this:
     Have you ever put off cleaning the toilet or doing the dishes? Can you imagine a society where nobody ever puts things off because they're messy, smelly or unpleasant?

From a comment thread in Google Plus (2013)

4) Political priorities — life path problems. Kinda getting back to the idea that each colony will need to come up with their own character, colonies would start with an archetype (not sure how to do this, but it'd be a function of looking at the initial reason for building the colony, money input and world climate/world traits) and then within that framework have random events that could happen based on planet and who colonized it. This would generate a set of planetary traits, such as idealism, pragmatism, greed, environmentalism et al that would effect the options available to the government when problems turned up. For example, a Three Generations Rule problem might be very easy for a highly pragmatic colony to deal with, while one that was high in idealism might run into problems. Yes, in a sense this is trying to ascribe in a half dozen variables a political/social culture...maybe impossible.


I’ll start by saying that the “Three Generation Rule” is more of a general statement and SF plot device, not an absolute.

We live in a kind and gentle biosphere which forgives many (individual and widespread) forms of self-delusion deception and overt ignorance including corruption, laziness, and just plain cost-cutting substandard work.

Might I suggest the (Under) 1 Generation Rule.

In regards to critical maintenance: the life support systems maintenance contractor (and however many of his crew as deemed necessary) who skimps on the work by not changing out filters, aggressively removing mold in air ducts, and swapping out seals on airlocks as usage and maintenance cycles demand will be shortly hauled up on formal charges, yes, of course, by the local authorities, or perhaps simply, and quietly, find themselves chucked out the airlock. If it’s the local authorities at fault, shrugs, well politicians don’t tread vacuum more successfully than crooked contractors, as a rule. Wash rinse repeat enough times and soon space stations and/or even large habitats will arrive at individuals who perform the work to spec.

Populations of entire Habitats who just shrug away such maintenance, well, they will just be the poor (dead) slobs who taught the lesson to everyone else.

Societies do change over time. Social tolerances and attitudes are not fixed, but mutate over time. I am not convinced that any particular aspect of human attitude or behavior can be said to be immutable.

As example. Fifty years ago (speaking largely in regards to American culture) racial, gender, cultural, and sexual-lifestyle intolerance was the norm, and tolerance was a small growing movement of social awareness, viewed in large swaths of American culture with, at best, suspicion. These attitudes have been changing and increasingly those who express overt intolerance are viewed as the misfits, outliers, and oddballs. While there are still notable exceptions, bigotry in general is in decline, which is to say it is not universally socially accepted (not that it has gone away).

From William Black (2015)

Isaac Kuo

     The three generation rule is just idiotic nonsense contrived for purposes of...a misguided attachment to planetary chauvinism.
     Actual historical reality shows us that a city like New York manages to exist for an indefinite number of generations without people magically forgetting how to run essential infrastructure.

William Black

     Isaac Kuo, while I wouldn't necessarily presume to know with absolute certainty, much less judge, the intention of thought behind the rule, I do agree that the three generation rule is a contrivance.
     The "rule" simply doesn't match the real world in any way. Here is my rebuttal to the three generation rule:
  1. It fails to account for the long term viability of cities over historical spans of time.

  2. It presumes a complete lack of self-interest and will to survive.

  3. It presumes a universal and abject lack of critical thinking, and presents an unexplained inability to perceive consequences of inaction. It presumes but does not explain an absence of rational decision making affecting entire city-sized populations. While you might find individual cases of any of the above in any population, it is an over generalization to assume universality of these deficits in cognition for entire populations.

Lilith Dawn

     Isaac Kuo, forget? What about "ignore"? Flint stands out in my mind.

William Black

     Lilith Dawn, granted, however people in the community perceived there was a problem and acted, in a persistent and on-going manner to determine the nature of the problem and raise the alarm. 

John Reiher

     Well, Nieuw Amsterdam New York is bad example. It always has had a constant influx of new people moving in and others moving out. New York City has resources from outside to help it sustain it's growth and infrastructure.
     The 3rd Gen rule assumes no influx of new blood into the colony. That all the resources are internal and no new resources are added to the colony.
     Just changing these two assumptions and the colony becomes much more long term. But... the colonists won't be grounders. They live in a much more precarious environment and there's a certain amount of discipline a resident must have over a grounder living in a city on a planet.
     If a grounder sees a rusty fire hydrant, they shrug and say "The city will fix it."
     If a colonist sees that a fire suppression device shows excess wear, they will report it as it's their responsibility as a citizen of the colony to help keep it up.

Isaac Kuo

     John Reiher I don't see any reason why a constant flux of people and resources wouldn't equally apply to space colonies. In order to create a space colony in the first place, there must be a practical logical chain to bring materiel and people. Whatever that was...the most plausible thing is that they will keep on using it.
     To me, this is the same sort of complaint as those who deride terraforming because lesser gravity will cause the atmosphere to go away in mere millions of years. Okay...but whatever practical mechanism was used to create the human usable atmosphere must surely have taken place over mere hundreds or perhaps thousands of years. Why not just keep on using it to keep the atmosphere topped off?
     (There are plenty of other problems with terraforming, but this one is silly, IMO.)

Alistair “Cerebrate” Young

     Well, that's true to a certain extent, and I generally agree with you as a rule —
     But there are a lot of bits of that history (and live-action examples in any major company's cost-center support departments, like IT) that also demonstrate the tendency of people to skimp on any maintenance that isn't absolutely necessary until the last minute, or to make unwarranted assumptions that the thing that's always been there always will be, or that the low-probability emergency condition will obviously never happen because it never has yet.'s just that the Northeast Blackout of 2003 (and its cascading effects), or the Flint Water Crisis, or assorted lengthy emergency-maintenance London Underground closures, et al. ad naus., were uncomfortably survivable (for most people) because the absolute essentials for life didn't depend on that infrastructure.
     So, y'know, I don't believe in the Three Generations Rule as a general principle. It's quite avoidable by a combination of competence, proper incentives, and cultural support.
     On the other hand, I do expect it to happen all the time if habitat systems management is delegated to the presently incumbent Earthside infrastructure-management firm of Chumpy McTimeserver and Representative Weaselface.

John Reiher

     Isaac Kuo I was just pointing out the base assumption of the 3rd Gen rule is that it's a closed system. As soon as you have a new influx of resources, people, or both, you never get that third generation. Everyone is second generation in that situation.
     New York if full of 2nd Gen New Yorkers. An active and realistic space colony should also be a 2nd Gen place to live.
     Of course, this assumes that the colony is in a civilized system. If you're the first one to a new star system and the only way to get there is by slow ship. It may take multiple generations for any new blood to show up. In that situation the only thing the colony has going for it is resources.
     However, I would say that a proper colony would have a colonial attitude, and the subsequent generations would also have that attitude. So the idea that complacency that would affect the "3rd Gen" situation, isn't a factor. Everyday is a new day and new challenge to overcome. Only when the colony is fully established would you have to worry about 3rd Gen issues arising. 

William Black

     John Reiher If the three generation rule assumes no influx of new blood into the colony. That all the resources are internal and no new resources are added to the colony ... well it seems even more of a contrivance.
     I have no idea why anyone would think this is a reasonable set of assumptions in the first place.
     Once you are on orbit, well you are half-way to everywhere, as a relatively well known author somewhat famously observed.
     Civilization is built on trade. Go as far back in human history as you care, trade is the universal activity of human populations.
     By the time anyone is constructing large scale space habitats there will be widespread ISRU and extensive industry involved in resource extraction, this is the only way such habitats could ever be built.

John Reiher

     William Black that's my point. The 3rd Gen rule assumes that there are no new additions to the colony, no new blood. It also assumes that the parents do not instill a proper respect of the environment the colony is in. It assumes that bunch of Millennial slackers are the 3rd generation, not the children of a viable and prosperous colony.
     And as Alistair Young pointed out, the colony isn't run as a for profit venture, with quality of life management and maintenance done by the lowest bidder.
     The second you get new people on the colony, the dynamic changes and everyone is always 2nd Gen and you never run into the problems of the 3rd Gen.
     It sounds like we're all talking past each other here and we are all in agreement that the 3rd Gen Rule doesn't make much sense. It's more a plot contrivance than an actual rule. 

Alistair “Cerebrate” Young

     John Reiher Well, I wouldn't necessarily say that. After all, the only things I generally see done worse than things done for profit are things done not for profit. Especially by monopolies — for myself, I'd like to see at least two competing life support providers...
     (Another approach worth considering might be the give-the-life-support-department-etc.-medical-officer-privileges approach, in which the CELSS Engineer gets to tell the station commander to shut up, sit down, and replace the gorram auxiliary scrubbers NOW, whatever it means for the rest of his budget.)

From a comment thread in Google Plus (2016)

      Painted aircraft flew through the core of the world. Lindsay stood in knee-high grass, staring upward to follow their flight.
     Flimsy as kites, the pedal-driven ultralights dipped and soared through the free-fall zone, far overhead. Beyond them, across the diameter of the cylindrical world, the curving landscape glowed with the yellow of wheat and the speckled green of cotton fields.
     Lindsay shaded his eyes against the sunlit glare from one of the world's long windows. An aircraft, its wings elegantly stenciled in blue feathers on white fabric, crossed the bar of light and swooped silently above him. He saw the pilot's long hair trailing as she pedaled back into a climb. Lindsay knew she had seen him. He wanted to shout, to wave frantically, but he was watched. His jailers caught up with him: his wife and his uncle. The two old aristocrats walked with painful slowness. His uncle's face was flushed: he had tumed up his heart's pacemaker. “You ran," he said. “You ran! "
     “I stretched my legs," Lindsay said with bland defiance. “House arrest cramps me."

     His uncle peered upward to follow Lindsay's gaze, shading his eyes with an age-spotted hand. The bird-painted aircraft now hovered over the Sours, a marshy spot in the agricultural panel where rot had set into the soil. “You're watching the Sours, eh? Where your friend Constantine's at work. They say he signals you from there."

     They shipped Lindsay into exile in the cheapest kind of Mechanist drogue. For two days he was blind and deaf, stunned with drugs, his body packed in a thick matrix of deceleration paste.
     Launched from the Republic's cargo arm, the drogue had drifted with cybernetic precision into the polar orbit of another circumlunar. There were ten of these worlds, named for the lunar mares and craters that had provided their raw materials. They'd been the first nation-states to break off all relations with the exhausted Earth. For a century their lunar alliance had been the nexus of civilization, and commercial traffic among these “Concatenate worlds" had been heavy.
     But since those glory days, progress in deeper space had eclipsed the Concatenation, and the lunar neighborhood had become a backwater. Their alliance had collapsed, giving way to peevish seclusion and technical decline. The circumlunars had fallen from grace, and none had fallen further than the place of Lindsay's exile.

     The cable in his arm disengaged itself and snaked back into the wall. The camera spoke.
     “You are Abelard Malcolm Tyler Lindsay? From the Mare Serenitatis Circumlunar Corporate Republic? You are seeking political asylum? You have no biologically active materials in your baggage or implanted on your person? You are not carrying explosives or software attack systems? Your intestinal flora has been sterilized and replaced with Zaibatsu standard microbes?"
     “Yes, that's correct," Lindsay said.
     “You will soon be released into an area that has been ideologically decriminalized," the camera said. “Before you leave customs, there are certain limits to your activities that must be understood. Are you familiar with the concept of civil rights?”
     Lindsay was cautious. “In what context?"
     “The Zaibatsu recognizes one civil right: the right to death. You may claim your right at any time, under any circumstances. All you need do is request it. Our audio monitors are spread throughout the Zaibatsu. If you claim your right, you will be immediately and painlessly terminated. Do you understand?"
     “I understand," Lindsay said.
     “Termination is also enforced for certain other behaviors," the camera said. “If you physically threaten the habitat, you will be killed. If you interfere with our monitoring devices, you will be killed. If you cross the sterilized zone, you will be killed. You will also be killed for crimes against humanity."
     “Crimes against humanity?" Lindsay said. “How are those defined?”
     “These are biological and prosthetic efforts that we declare to be aberrant. The technical information concerning the limits of our tolerance must remain classified."

     “I see,“ Lindsay said. This was, he realized, carte blanche to kill him at any time, for almost any reason. He had expected as much. This world was a haven for sundogs: defectors, traitors, exiles, outlaws. Lindsay doubted that a world full of sundogs could be run any other way. There were simply too many strange technologies at large in circumsolar space. Hundreds of apparently innocent actions, even the breeding of butterflies, could be potentially lethal.
     We are all criminals, he thought.

     The camera opened the customs hatch with a creak of badly greased hydraulics. Lindsay shook himself free of the past. He floated down a stripped hallway toward the feeble glow of daylight.
     He emerged onto a landing pad for aircraft, cluttered with dirty machines.
     The landing pad was centered at the free-fall zone of the colony's central axis. From this position, Lindsay could stare along the length of the Zaibatsu, through five long kilometers of gloomy, stinking air.

     The sight and shape of the clouds struck him first. They were malformed and bloated, with an ugly yellowish tinge. They rippled and distorted in fetid updrafts from the Zaibatsu's land panels.
     The smell was vile. Each of the ten circumlunar worlds of the Concatenation had its own native smell. Lindsay remembered that his own Republic had seemed to reek when he first returned to it from the Shaper academy. But here the air seemed foul enough to kill. His nose began to run.

     Every Concatenate world faced biological problems as the habitat aged.
     Fertile soil required a minimum of ten million bacterial cells per cubic centimeter. This invisible swarm formed the basis of everything fruitful. Humanity had carried it into space.
     But humanity and its symbionts had thrown aside the blanket of atmosphere. Radiation levels soared. The circumlunar worlds had shields of imported lunar rubble whole meters deep, but they could not escape the bursts of solar flares and the random shots of cosmic radiation.
     Without bacteria, the soil was a lifeless heap of imported lunar dust. With them, it was a constant mutational hazard.
     The Republic struggled to control its Sours. In the Zaibatsu, the souring had become epidemic. Mutant fungi had spread like oil slicks, forming a mycelial crust beneath the surface of the soil. This gummy crust repelled water, choking trees and grass. Dead vegetation was attacked by rot. The soil grew dry, the air grew damp, and mildew blossomed on dying fields and orchards, gray pinheads swarming into blotches of corruption, furred like lichen…
     When matters reached this stage, only desperate efforts could restore the world. It would have to be evacuated, all its air decompressed into space, and the entire inner surface charred clean in vacuum, then reseeded from scratch. The expense was crippling. Colonies faced with this had suffered breakaways and mass defections, in which thousands fled to frontiers of deeper space. With the passage of time, these refugees had formed their own societies. They joined the Mechanist cartels of the Asteroid Belt, or the Shaper Ring Council, orbiting Saturn.

     In the case of the People's Zaibatsu, most of the population had gone, but a stubborn minority refused defeat.
     Lindsay understood. There was a grandeur in this morose and rotting desolation.

     Slow whirlwinds tore at the gummy soil, spilling long tendrils of rotten grit into the twilit air. The glass sunlight panels were coated with filth, a gluey amalgam of dust and mildew. The long panels had blown out in places; they were shored up with strut-braced makeshift plugs.
     It was cold. With the glass so filthy, so cracked, with daylight reduced to a smeared twilight, they would have to run the place around the clock simply to keep it from freezing. Night was too dangerous; it couldn't be risked. Night was not allowed.

     To his left, the sunlight panel had been cleaned in patches. A cadre of lumpy robots were scraping and mopping the fretted glass. Lindsay nosed the ultralight down for a closer look. The robots were bipedal: they were crudely designed. Lindsay realized suddenly that they were human beings in suits and gas masks.
     Columns of sunlight from the clean glass pierced the murk like searchlights. He flew into one, twisted, and rode its updraft.
     The light fell upon the opposite land panel. Near its center a cluster of storage tanks dotted the land. The tanks brimmed with oozing green brew: algae. The last agriculture left in the Zaibatsu was an oxygen farm.
     He swooped lower over the tanks. Cratefully, he breathed the enriched air. His aircraft's shadow flitted over a jungle of refinery pipes.

     As he looked down, he saw a second shadow behind him. Lindsay wheeled abruptly to his right.
     The shadow followed his movement with cybernetic precision. Lindsay pulled his craft into a steep climb and twisted in the seat to look behind him.
     When he finally spotted his pursuer, he was shocked to see it so close. Its splattered camouflage of dun and gray hid it perfectly against the interior sky of ruined land panels. It was a surveillance craft, a remotely controlled flying drone. lt had flat, square wings and a noiseless rear propeller in a camouflaged exhaust cowling.
     A knobbed array of cylinders jutted from the robot aircraft's torso. The two tubes that pointed at him might be telephoto cameras. Or they might be x-ray lasers. Set to the right frequency, an x-ray laser could char the interior of a human body without leaving a mark on the skin. And x-ray beams were invisible.
     The thought filled him with fear and profound disgust. Worlds were frail places, holding precious air and warmth against the hostile nothingness of space. The safety of worlds was the universal basis of morality. Weapons were dangerous, and that made them vile. In this sundog world, only weapons could keep order, but he still felt a deep, instinctive outrage.

     Lindsay swooped down for a closer look. A squat guardline of black weapons bunkers swiveled visibly, tracking him with delicate bluish muzzles. He was over the Sterilized Zone.
     He climbed upward rapidly.
     A hole loomed in the center of the southern wall. Surveillance craft swarmed like hornets in and around it. Microwave antennae bristled around its edges, trailing armored cables.
     He could not see through the hole. There was half a world beyond that wall, but sundogs were not allowed to glimpse it.
     Lindsay glided downward. The ultralight’s wire struts sang with tension.
     To the north, on the second of the Zaibatsu's three land panels, he saw the work of sundogs. Refugees had stripped and demolished wide swaths of the industrial sector and erected crude airtight domes from the scrap.
     The domes ranged from small bubbles of inflated plastic, through multicolored caulked geodesics, to one enormous isolated hemisphere.

From SCHISMATRIX by Bruce Sterling (1985)

(ed note: in John Varley's Gaea Trilogy, there are some corporations that wait for the 3-gen rule to kill a habitat. Then they swoop in, take possession, vent it to vacuum to sterilize it, and then sell it to some other idealistic group as a unique fixer-upper opportunity.)

They built the Coven there. It was a cylinder seven kilometers long with a radius of two kilometers. Artificial gravity was provided by spin; night, by closing the windows.

But the days of isolation were over almost before they began. The Coven was one of the first nongovernmental groups to move into space in a big way, but they were not the last. Soon the techniques of space colonization were refined, cheapened, standardized. Construction companies began to turn them out the way Henry Ford had turned out Model T’s. They ranged in size from the merely gigantic to the Brobdingnagian.

The neighborhood began to look like Levittown, and the neighbors were odd. Just about any sizable lunatic fringe, band of separatists, or shouting society could now afford to homestead in the LaGrangians. L2 became known as Sargasso Point to the pilots who carefully avoided it; those who had to travel through it called it the Pinball Machine, and they didn’t smile.

Some of the groups couldn’t be bothered with the care and feeding of complex machinery. They expected to exist in pure pastoral squalor inside what was really just a big hollow coffee can. The developers were often happy to accommodate them, reasoning that all that expensive hardware, if installed, would only be abused. Every few years one of these colonies would come apart and fling itself and its inhabitants across the sky. More often, something would go wrong with the ecology and people would starve or suffocate. There was always someone willing to take one of the resulting hulks, sterilize it with free vacuum, and move in at a bargain price. The Earth never ran short of the alienated and the dissatisfied. The United Nations was happy to get rid of them and did not ask too many questions. It was a time of speculation-of instant fortunes and shoddy practices. Deals were made that would have shocked a Florida real estate developer.

From WIZARD by John Varley (1980)

(ed note: the asteroid L5 colony of Rosinante is offered a contract to refurbish the NAU-Ceres I L5 colony. To their horror they discover an early onset case of the Three Generation Rule)

NAU-Ceres I, officially the Senator J. Walter Deegnan III Class II Naval Logistics Support Facility at Ceres, was completed in 2008 by the State of the Art Space Construction Company, the only responsive bidder on the contract issued by NAUGA-Navy, two and one-half years after the deadline and many, many megabucks over cost.

"This place is in ba-ad shape, Charlie,” Rubenstein replied. “The window bays have a biological fouling problem you wouldn't believe. It rains in here, Charlie, from clouds. The windows get rained on, too, okay? They were designed to drain off—when the cylinder was pulling a cee of 500 to 520 cm/sec/sec. They had to reinforce the mirrors to keep them from flexing, okay? And then they were so heavy that they had to cut the rotation speed to keep the hinges from failing."

"So you have algae growing on the windows?” Cantrell asked.

"Charlie, you got duckweed growing on the windows!” Rubenstein replied. “On window bay number two, there is a two-hundred-fifty-hectare lake a meter deep in some places. I saw water lilies and frogs and snails and a turtle—must have been somebody's pet—that was a foot long. Guess what else? Don't guess, I'll tell you. Charlie, the gasket material is rotten."

"That's impossible,” said Cantrell. “We've had silicone rubber formulations that would last forever since ... since ... hell, since before space flight."

"And the Navy specified the right stuff,” Rubenstein agreed, “but this place was built on low bid, remember? The Navy inspector must have missed it.” He grinned and pulled his nose. “Shave two to three cents a pound off a quarter million tons, Charlie, it's a tidy piece of change. Of course, the mylar/aluminum mirror is reflecting ultraviolet, and the whole thing is cycling wet and dry—that doesn't help either."

"The gaskets have to be replaced?” Marian asked.

"From the books, it looks like this dump is leaking a ton of oxygen a day,” said Rubenstein, “and it's getting worse. Myself, I would sooner rebuild from scratch. But what would you use for money?"

"What else is wrong with NAU-Ceres I?” Cantrell asked.

"Thirty years of deferred maintenance. It wasn't built right to begin with, and if they couldn't fix it on the cheap, it didn't get fixed at all. The elevators don't work right, the pipes—steam, sewer, potable water, you name it—they all leak. The ductwork is in need of a major overhaul. The wiring, Charlie, it would make you weep. The wiring has no relation to any of the wiring diagrams on file, the youngest of which, by the way, is dated March 1, 2019."

"Oh, Christ. I think I have the picture, Mordecai.” Cantrell slumped back in the telecon chair and laced his fingers across his chest. “So all right. We'll have to work out the details, but figure I want a sound structure at NAU-Ceres I. Whether we do an extensive overhaul or rebuild from scratch—either way, the first thing we need to do is get an estimate on the cost. We can use the Japanese at Yamamoto and Nakajima as well as the locals and our people from Rosinante."

"You want a write-up, Charlie, I'll do you one,” Rubenstein said at last, “but, Charlie, it'll be guesswork. How much will it cost to build a machine to replace rotten gaskets in the window bays? Multiply that by a few hundred or a few thousand...” He shrugged. “The whole thing will be guesswork, Charlie.” Cantrell sat biting his thumbnail. “And then what you wind up with isn't all that great. Talk about industrial slum—"

"I understand,” Cantrell said. “What's the bottom line?"

"Basically, Charlie, you can spend as much money as you want on this slowly spinning sack of s**t. There just ain't no limit. There really ain't."

From THE PIRATES OF ROSINANTE by Alexis Gilliland (1982)

     Listen, out in the Belt, we do things differently. Not just from the Inner Worlds, but from each other. No two habitats are the same. We're all little islands of culture and history, separated by hundreds of thousands of kilometers of empty space. But the one thing that does run through all of us is the importance of maintenance. It has to. Where it didn't, habitats failed. Societies collapsed. People died. But it wasn't always like that. Enough failures ensured that trait was selected for.

     Earthers don't get it. They have open sky. Free air. Stable ecology. Sure, they had to learn the hard way the importance of managing all of that on a planetary scale, and their society almost failed because of their negligence, but they really have it good down there. Our margin of error is smaller. Resources are more scarce. We've got to budget accordingly

     It's called the Three-Generation rule. Basically, people get lazy. They get used to the idea of having a stable ecosystem around them. They skimp on the upkeep. Things start failing. The next generation grows up and does the same thing. Eventually, things get bad, quickly. The rule comes from the observation that this tipping point usually happens about three generations in. Some vital resource gets used up, a critical system or component fails. The lucky ones manage to get relief efforts from a nearby charitable habitat, or maybe Mars or Earth. Some immigrate to other habitats. Others just collapse. Every few years there'd be a story on the interplaNet about some colony somewhere in a state of emergency. Not so much now. It used to be that some group of wide-eyed idealists got the idea to move out to the Belt, build themselves a nice habitat, and try to set up their own little world. Later they realized just how difficult it is to manage an entire biosphere and society at the same time without resorting to draconian extremes. Sometimes they got it together and joined the rest of Belt civilization.
     As for the rest, there was a small boom in companies that specialized in “refurbishing” failed habitats. They would go in, clean it out, fix it up, and sell it back to someone else. It seemed rather grisly, but apparently the market existed. Most of them were in good physical condition and still air-tight; they just needed an ecological re-boot.

     That was the history of Freeharbor. Back then it was known as Independence.

     I wasn't there when it was founded. But I was there near the end. By my teens it was already well-passed decline. This was probably somewhere around 2230 or so. After about a decade of general corruption and shenanigans, the Administrator had finally decided to try an experiment in corporate plutocracy. To his credit, he seized power on the promise that he would prioritize life support maintenance, overhaul resource recycling systems, and all the rest. He would make Independence a shining exception to the Three-Generations rule. And for a little while, it actually went surprisingly well. Until things started breaking down a little too often. There was always another crisis that could only be solved through the absolute authority of the Administrator's office.
     Technically there are provisions about printing firearms on habitats, but that didn't stop anyone. Armed riots frequently broke out. I tried to keep my head down, often times quite literally. But you can only stay out of these kinds of things for so long, especially when it's your home getting torn apart. So I fought. I didn't stay, though. I ran. I fought my way to safety somewhere else. I got a group of friends and some of my family and we found a small transport. It had enough delta-V in the tanks to get us to Ceres. I took a few bullets in the arm on the way to the docks trying to get to it. There were enough meds onboard to keep me stable for the several weeks it took to get to Ceres, but I don't really remember much. I was out for most of the flight. The last thing I remember seeing was the habitat's big pair of metal cylinders slowly spinning in the night, their huge mirror rings almost too bright to look at.

     When we got to Ceres they had to amputate my arm. It took almost a month for them to grow me a new one, so I spent most of my time in the hospital with my arm stump submerged in a tank of my own cultured, engineered stem cells as it slowly regenerated.
     I never really returned after that, partly because I felt ashamed for running. Most of us ended up staying on Ceres. There was a small flow of refuges coming from what remained of Independence's imploding society. I paid attention to the situation as little as I could at first, not wanting to think about what I left behind. But curiosity crept its way past my desire to forget, and I suddenly found myself looking up news reports on interplaNet. There was a time when I read or watched little else.
     Apparently in the weeks after we had fled, the various resistance movements had all organized and successfully raided the Administration Tower. When they got to Administrator, the bastard had already killed himself. They blew his body unceremoniously out of the main airlock. Now they were asking for assistance in rehabilitating their habitat. A lot of the ecology had been destroyed in the uprising. For a while it didn't look good.
     Mars was one of the first to come to their aid. They offered advanced biotech to help restart their biosphere and maintain a more self-sustaining ecology. They even offered space for some residents to resettle on Mars itself. Some had taken them up, but most stayed. They learned. They rebuilt. And from their struggle, Freeharbor was born.

     I saw first hand how things can go wrong. I was lucky, and so was my habitat. These dangers aren't gone just because it hasn't happened in recent years. This is space. Outside the hull of your habitat is nothing but life-sucking vacuum. No matter how cushy or green or utopian your orbital might feel, it's an important thing to remember; don't get complacent.

Death by Civil Unrest

A space habitat is not planet. The air, heat, and the rest of the life support does not occur naturally. It has to be created by technology.

And remember Every gram counts. This technology is not going to be armor-plated. It is going to be made out of foil and wires. The infrastructure of a space colony is fragile.

Which means a troubled young man angry at the space colony's government, somebody like Timothy McVeigh, would be capable of much worse than killing a paltry 168 people. Using the same level of effort they could shatter the entire freaking colony and kill over 140,000.

So a space colony that does not want to die screaming all alone in the night is going to need to take some steps. Among them are preventing angry young men from carrying out such dastardly acts, and helping not becoming so angry in the first place.

In asteroid mines or cramped space colonies, perhaps a system like Discworld Mine Signs could be utilized. Or Shipnet. Or something like Twitter hashtags, if you can post anonymously.


There's an old saying that only two things are unavoidable: death and taxes. I think this is wrong—the two unavoidable things are politics, and it's seldom-admitted offspring, bureaucracy. (Their Titan parent is of course economics.)

Politics: you may not like it but you can't ignore it because whenever two or more people have ideas about how to do something requiring the participation of two or more people there's going to be an argument about how to do it.

Bureaucracy: because once the argument is settled you need to coordinate the tasks, and once your community exceeds Dunbar's number you need to develop mechanisms for managing work and social relationships between people who don't know each other.

It's fairly obvious that technology affects the implementation details of politics and bureaucracy (and there's feedback involved too, via market regulators and command economies). And there are scale issues too. Back in the 1670s and 1680s century when Samuel Pepys served as Secretary for the Admiralty, administration for the Royal Navy ran on a handful of staff and relied on disbursement of funds—in cash—to ships' captains to see to their maintenance and the pay of their sailors. Today it's hard to imagine a modern defense ministry running on cash-in-hand: even Da'esh have accountants and an org chart. But the ability to run a modern bureaucratic defense procurement and supply organization is required due to the capital-intensive nature of modern warfare (you try buying an Aircraft Carrier with cash) and relies in turn on availability of modern tools: not just computers, but accounting procedures, project management, quality assurance, process control, and a host of other specialities that simply didn't exist back in the age of sail. On the other hand, back in the 17th century ships and squadrons might be commanded by officers weeks or months from the nearest political point of control and operating on the basis of orders which, although obsolete, had not been countermanded (and it wasn't just at sea: for example, the Battle of New Orleans took place in 1815, weeks after the treaty ending hostilities had been signed).

So. Taking the space cadets seriously for once ...

What are the political problems that would arise from the extension of an Earth-based political framework to governance of off-world space colonies? And what kind of bureaucratic mechanisms might be developed to deal with the arising issues?

Most SF centering on near-future space colonization is regrettably polluted by rose-tinted libertarian bullsh*t. Let's face it: in the really short term, outposts like the ISS or a near-term return-to-Moon or expedition-to-Mars will be governed by existing legal arrangements made by the national government with jurisdiction over the crew. In practice this means the 1998 ISS agreement, the Outer Space Treaty, and customary international law. And the "colonists" aren't; they're typically highly trained middle-aged scientists, engineers, and bureaucrats-with-other-skills (note how many of NASA's retired astronauts go on to careers in space program senior management or even seats in the Senate or Congress).

Looking further ahead—by which I mean out past 2030 at the very earliest—we might see encampments with a handful of people living and working off-planet semi-permanently, along the lines of an Antarctic research station (albeit in a vastly more hostile environment). "Law enforcement" overlaps messily with psychological healthcare, and generally is a matter of shipping the unruly home for treatment and diagnosis (and, optionally, restraining them en route). Money? Hah! While informal economies eventually emerge once you have a population in double or triple digits (things like trading extra shifts worked, or food, or homebrewed moonshine) it takes a long time to get to the point where "money" is internally useful for anything other than keeping track of interpersonal exchanges of obligations. And as for "no taxation without representation", that's a really long way in the future, and becomes highly problematic when the polity of 3000 who are objecting to remote governance and taxation is reliant on a distant polity of 300,000,000 who built the metal world they live in.

But by the time we look as far as self-sufficient comet-mining or terraforming colonies, a century or two in the future, the questions of political coordination and local vs. remote administration will become pressing. And these questions also apply to long-term colonies and generation ships. Assuming the (huge) obstacles to these are overcome (notably: deleterious medical radiological and microgravity effects of long-duration spaceflight; economic framework for repaying the cost of foundation; ability to maintain a large-scale closed cycle life support ecosystem; ability to replicate all necessary infrastructure components and consumer goods; ability to care for, educate, and train new members of the population and to sustain those who can no longer work or who aren't suitable for work at core survival tasks) ... what, realistically, happens?

I have some starting assumptions. Notably: the traditional right-wing American vision of settlers in space is utterly untenable because it assumes people can "walk away" from local market failures, and that individuals are solely responsible for their own errors. Libertarianism won't fly in space where any "market adjustment" is likely to prove lethal to a significant proportion of the population. Indeed, the American formulation of rugged individualism is horrifically dangerous in such a setting: imagine the mind-set that gives rise to schoolyard shooters, and put it in an environment where the only things holding in the atmosphere are the walls.

Secondly: in the absence of magical scientific breakthroughs, getting home from a fucked-up colony will range from very difficult to impossible. If you colonize the Gobi desert or Phoenix, Arizona, you can probably escape if you have a gassed-up SUV, some cash, and enough water. If you colonize Mars, though, you're going to need a spaceship capable of reaching orbit and at least three months (more likely 18 months) of air and supplies. That's a whole different ball game, and once you realize you're living in a failed world, you're going to be far too late: it makes the plight of the people in the European migrant crisis today look trivial. Space colonies exist, of necessity, in a kind of liminal Gene Cernan voiced "failure is not an option" territory: and this is not a good place to live, much less to raise a family and expect a peaceful retirement.

So I don't see our contemporary interpersonal or cultural relationships working. Some sort of tribal organizational structure might work, by which people could work with distant or unrelated "relatives" within a web of familial obligations; it's a way of diffusing relationships to allow larger groups to work together for joint survival. Look at parts of the middle east for cultures adapted to that way of life ... or better still, don't (if you're attached to the idea of personal autonomy, choosing your own sexual partners, and deciding whether or not to have children or how to work for yourself). I'm only half-kidding: obviously iron-age tribal practices won't help cultures in brittle, high-risk environments mediated by high technology survive ... but neither will what we've got now on the sleepwalking, neoliberalalism-dominated west.

Nor are our current political representative structures, adapted to heterogeneous nations sharing an open, relatively resilient world, necessarily going to work well in a closed system. A space colony can't afford to be governed by ideology in the absence of feedback from instrumentation. But technocracy isn't the answer either; technocracy has nothing to say by way of answering the core questions of human existence, such as "what is best in life?" much less "what is right?" And a space colony probably can't survive a revolution that turns violent.

Any workable form of government for such a fragile environment is going to have to provide mechanisms for prompt and non ideologically-biased responses to deviations from the baseline. It's going to have to provide solutions that work for everybody, because the environment is a lifeboat and if you give up on someone they will die (or worse, having no expectation of living may choose to take everybody else with them). It's going to have to provide a framework for settling arguments where there is no obvious "best" solution without pissing off one faction or the other, and a framework for orderly and non-violent transfers of power (because shaved apes are addicted to up-ending their social hierarchies). The bureaucracy it comes with is going to have to offer mechanisms for delegating authority across vast gulfs of space and time, be relatively lightweight (at least in the early decades of a colony), and should arguably satisfy Rawls' philosophical notion of justice as fairness and provide distributive justice, lest it give rise to grievances leading to instability or revolution. (As a propensity for fairness seems to be wired into primates at a very low level, running on an administrative system that optimizes for fairness seems like an appropriate way to minimize friction.)

Anyway. What other angles am I missing here? You, too, can help design a constitution for a space colony! Just remember two things: it has to be somewhere you'd be comfortable living the rest of your life as an ordinary citizen, and if you get it wrong, you can't walk away.

From A GAME OF CONSEQUENCES by Charles Stoss (2016)

Technological Decline

A more long-term problem is that of Technological Decline. As Joan Vinge pointed out in THE OUTCASTS OF HEAVEN'S BELT: If a planetary colony falls into barbarism, everybody reverts to a non-technological agrarian society.

If an asteroid civilization falls into barbarism, everybody dies.

It takes lots of technology to run the oxygen system, airlocks, spaceships, hydroponics, nuclear reactors, and other items vital for life in space. No technology, no life. In other words, they are a Hydraulic state.


Betha saw suddenly the fatal flaw the original colonizers, already Belters, must never have considered. Without a world to hold an atmosphere, air and water — all the fundamentals of life — had to be processed or manufactured or they didn't exist. And without a technology capable of processing and manufacturing, in a system without an Earthlike world to retreat to, any Dark Age would mean extinction.

From THE OUTCASTS OF HEAVEN BELT by Joan Vinge (1978)

Sample Space Habitats


     There are several large habitats proposed, generally by people who are both smarter and better-educated than I am. Wherever possible I prefer to use solutions proposed or developed by others, but I disagree with some of the fundamental assumptions made for structures like the O'Neill cylinder. That will necessarily result in a different outcome, thanks to several design decisions that go in another direction. #1 on that list: There are no windows. None. Don't even think about it; windows in space are incredibly stupid.

The headline results so far are as follows:
Design population: 5,000 people
Maximum population: 5,280 without major changes, up to twice that under emergency conditions
Mass: 142,750 tons shielding, 4,552 tons hull, 2,770 tons air, 350 tons occupants. As-yet unknown masses for furnishings, life support, hydroponics, other systems.
Volume: 2,262,000 m³ (79,882,000 ft³)
Area: 138,000 m² (13.8 hectares / 34 acres) under habitable gravity.

     The structure would require the capture and exploitation of 160,000 to 200,000 tons of asteroidal material, or about 67,000 m³ of carbonaceous chondrites. Only about 600 tons (0.3%) needs to be carbon, but nearly 2,000 tons (1%) needs to be nitrogen. A single 50-meter diameter rock should just about do the trick, roughly the size of the Tunguska meteor. An alternative is sixteen 20-meter diameter rocks (Chelyabinsk sized) with the proper composition on average. There are anywhere from hundreds of thousands to tens of millions of near-Earth asteroids in this size range.

     The two driving forces in my mind are radiation protection and moderate to full gravity. We know that microgravity is very harmful to humans even with the best medical care available and years of preparation in advance of relatively short (6-12 month) exposures; there is every reason to suspect that microgravity is not survivable in the long term. For this reason gravity or pseudogravity is a fundamental requirement. Radiation exposure is also tremendously harmful; current spacecraft are not survivable over the long term. Shielding that reduces the level of radiation exposure to Earth-normal or lower is also a fundamental requirement. The combination of these two requirements means a series of trades in structural and shielding materials. For free-space habitats I've settled on counter-rotating composite habitat modules on a common axis surrounded by non-spinning shielding made of bulk rock with a metal skin. For habitats in small bodies (Phobos, Deimos, other bodies with a few % Earth gravity at most), the habitat sections would be buried and would rely on bulk material for shielding. Bodies with significant gravity are different enough that they need to be addressed with unique designs.

     I'll deal with the free-space version first. Shielding is very expensive in mass terms. There are two primary sources of radiation in free space, the solar wind (particularly solar proton events or SPE) and cosmic rays (GCR).
     Cosmic rays are isotropic, so the most efficient shape would be a sphere. The solar wind is highly directional, so the most efficient shape would be a long, thin rod. Spheres are complex and inefficient to turn into living space, so a cylinder is the basic shape of choice. Remember that radiation doesn't turn corners, so we can use unconnected pieces of shielding that allows vessels in and out of the protected area without moving parts.
     We can adjust the relative cost of shielding for the Sun vs. shielding for GCR by changing the aspect ratio (length to width ratio) of the cylinder, but the optimum orientation is for one end of the cylinder to point at the Sun and carry somewhat heavier shielding than the rest of the hull. This imposes a stationkeeping burden to keep the end pointed at the sun. For lower dV costs the structure should be vertical, which means the entire shielded hull will rotate into view of the Sun over the course of a year. There does not seem to be a compelling argument either way except for the slim chance that a catastrophic CME or other solar event might be made survivable by taking shelter at the far end of the rod.
     Human physiology limits the speed of spin gravity, thus setting a lower limit on the diameter of the colony; my design uses a radius of 60 meters and rotation speed of 3.89 RPM for 1g Earth-normal gravity at the outer floor. Biology also sets a lower limit on the population of a self-sustaining colony; research differs on the exact value but 5,000 appears to be safe. I specify a set of four habitat modules each 50 meters long, each to house a nominal population of 1250 people. The structure can grow by adding pairs of habitat modules along the common axis, saving the expense of extra endcaps and costing only the shielding mass for the wall of the outer cylinder.
     The habitats spin inside a stable shielded hull without contacting it; a physical gap of three meters separates the outer walls of the habitats from the inner walls of the hull so either structure can be maintained while under spin. Internal positioning is maintained with magnetic repulsion as necessary, to minimize the torque applied to the outer hull. No isolation is perfect, so the structure will require      thrusters of some kind. Ion would be preferred, using either metals or heavy gases.
     Shielding is composed of 2mm of aluminum with a standoff space (Whipple shield for micrometeoroids), then 1cm of nickel-iron (30/70) followed by 104cm of packed regolith (1.5g/cc density, composition similar to lunar soil or stony asteroids). The outer layer of habitat includes 30cm of water as additional shielding, pump-able counterweight, leak indicator and bulk storage. This combines to provide an attenuation of 4.518 (in units of 1/e^x), blocking 98.91% of radiation. The first floor will still experience slightly more radiation than Earth average. For ideal results an attenuation factor of 5.3 is desirable; longer-term projections indicate that the GCR could potentially be as high as 1500mSv (vs. 740mSv recorded so far) which would suggest a factor of 6.0 attenuation to reach Earth-normal levels. In other words, even with this much shielding there may be times where the inhabitants need to evacuate to the inner floors so the material of the outer floors can protect them from radiation spikes.
     In order to make the most efficient use of this shielded volume the habitats are built in levels or floors of four meters each. Each floor is structural, capable of functioning as the outer hull during the construction phase, capable of independently supporting its own mass and floor loads, and capable of limiting the spread of damage in case of structural failure or impact. The material is UHMWPE, very long-chain polyethylene (Spectra fiber) with an aluminum film liner. This can be manufactured using plants to process CO2 and water (in turn made from any sources of carbon, hydrogen and oxygen). The habitat's hydroponics system is designed to produce plastic for this purpose in addition to food, though during the construction phase the mix of plants will heavily favor plastics.
     The outermost floor is at full Earth gravity, while each floor inward provides progressively less gravity; specific floors can be designed to mimic the gravity of Mars, Venus or the Moon if desired. A microgravity bay in the center of the structure has effectively no gravity; this space can be used as a shirtsleeves environment for building or repairing delicate spacecraft among other things. Total floorspace is 149,540m²; if we define 'habitable' gravity as 0.3g or higher then 138,230m² of that space is habitable. That's eleven floors of useful gravity (including analogs of Earth, Venus and Mars), two more of low gravity (including an analog of the Moon) and one of microgravity.

     A nearly identical design would be built into a pit on Phobos or Deimos. Phobos in particular could host a set of habitat modules in an open pit; if the pit is deep enough and placed to face Mars then the disk of Mars will fully block any views to space. No end-cap would be necessary for radiation protection; further, the vastly greater mass of shielding would mean the habitats would see less radiation than on Earth. One application of this might be as a permanent base at the site of a Phobos-Mars transfer tether. The habitats would be built up over time using materials excavated from the pit, with the option of adding more and more hab modules by excavating the pit deeper and deeper. This technique could be applied to main-belt asteroids like Ceres, Vesta, Pallas, etc.; the floors would need to be tilted slightly to accommodate the gravity of the parent body and a covering shield would be necessary but otherwise a very similar prospect.

     Throughout my design process I have sought to use Earth-normal design standards. This phase of space exploitation is far beyond the early adventurers, meant to be constructed using by-then-proven technologies and inhabited by average people (doctors, mechanics, teachers). Average people like having creature comforts; it's good for our physical and mental health. For example, I assume that each resident requires about 100 m² of space: roughly 32 m² of personal space, 36 m² of public space and 32 m² of work space. This is about 344 ft², or the size of a smallish studio apartment. A family of four would enjoy 128 m² or about 1,378 ft², modest by American standards but ranging from generous to lavish in many other places. Smaller is certainly possible, but that's a size that most people would accept. My research suggests that floor space for growing food, clothing and furnishings will be roughly 20 m² per person; this space is categorized as work space. That leaves another 12 m² per person or 15,000 m² per habitat (160,000 ft²) or roughly one large-ish office building at 32mx32m and 15 floors. The public 36 m² accounts for hallways, engineering spaces (including life support), schools, public eating and/or meeting space and parks. Some of that could be considered 'work' space; I didn't try to stick to some particular metric, but rather used that as a basic assumption. If it turns out that the mix is more like 20 m² public and 48 m² work it makes no difference.

     The internal structure of the habitat starts with the structural hull layer, 7.6mm of PE fiber with an aluminum foil liner to make it gas-tight. This layer is strong enough to handle two atmospheres of pressure; the entire four-meter floor could be flooded with water and still fall within structural limits. This is primarily formed of fibers wound around the cylinder, with secondary layers wound at 45° intervals to provide strength on the axis. These secondary layers flow into the endcap walls or sidewalls and carry the stress of the endwalls through the hull.
     Next is a protective layer. The outer floor uses plastic liners filled with water and plastic-cushioned isogrid aluminum ribs which function like joists. Inner floors use plastic-cushioned planks or deck plates of aluminum or bamboo, potentially over their own isogrid layer for heavy-use areas. This layer protects the hull against abrasion and distributes loads to prevent punctures.
     On top of that floor fits standard furnishings. Walls are thin metal or even Shoji-style paper with foam cores for noise attenuation. This is less about minimizing weight and more about reducing the amount of material used. Each floor has its own unique radius of curvature, so furniture is designed to bear weight along the flat axis and accommodate multiple radii along the curved axis. Still, the structure is designed to handle a floor load of 100kN/m² (nearly 15 psi / 2,160 psf), which is strong enough to drive heavy machinery over without damage. Most objects are made out of 'foamed' aluminum or titanium, or bamboo; the choice of material depends on what resources are most plentiful at the time. Bamboo sinks carbon and nitrogen while foamed metals sink metals; either can be reprocessed back into base material if necessary.
     Furnishings can be painted, anodized or covered in fabrics as appropriate. Bathroom and kitchen facilities will be similar to Earth counterparts, with added efficiency features like auto-off taps. Plumbing would generally be plastic and wiring would generally be aluminum with plastic insulation. Ceramic materials will serve the same purpose as on Earth, so a table setting is likely to have very familiar dishes. Silverware will likely be titanium since that is less complex to produce than stainless steel. Environmental systems will consist of air supply and return, with user-settable temperature and humidity controls. Each compartment will include emergency oxygen supplies and patch-sealing kits, but this is largely a formality.
     The layout of the habitat depends on a number of factors. I've examined dedicated residential and occupational floors but in order to balance the load on environmental systems it may be better to make each floor carry a mix of spaces. There should be a lower limit for gravity in living spaces, and those living in low g should work in higher (and vice versa) if commuting is required. This supports an argument for above-normal gravity in parts of the habitat, but doing this for the entire outer floor would take up a lot of living space at increased gravity. At any rate, some mix of residential and work space will exist, with hallways to connect them and public spaces such as parks to break things up.
     Access between floors would be by elevator at the ends of the cylinder. There should be no penetration of each floor's structural hull; all connections pass through the sidewall at either end and then in or out as needed. The stresses involved are significantly less. In any case, the longest commute to work would be only a few hundred meters at worst; an easy walk.
     Each floor balances its center of gravity by pumping water between storage bags at various points. The elevator system does the same, measuring the mass of occupants for a trip and moving mass on the other side to counterbalance the effect. This allows the structure to respond to shifting mass distribution and maintain balance without requiring significant amounts of power.
     The ends of each cylinder hold other utility connections: air, water, power. Airlock connections to neighboring modules are here. The end habitats have larger airlocks to allow for large equipment to be moved in or out. Each floor handles as much of its own life support and environmental load as possible, but power needs to come in from outside and heat needs to go back out. Power can be transferred through a rotation surface (like a DC brush motor), but      it is more efficient to provide power connections at either end of the cylinder and run electricity through the axis.
     There is no 'central shaft'. Loads are carried through a ring connection between each habitat. This interface is where motors can spin up both members of a habitat pair without needing to use reaction mass. A short nonrotating access tunnel between modules can also accept concentrated sunlight from outside the shield and forward it via waveguide to growing areas. This section carries the load of any position adjustments made using magnetic pads connected to the shield, as well as sensors necessary to determine position and rotation of each module and the shield itself.

     Hydroponics make the most of the available space. Aquaculture tanks will typically occupy the bottom half-meter to meter of the space, with stacked layers of high-intensity hydroponics above. Methods will be specific to each species; leafy greens like lettuce may be grown in float rafts directly in the fish water or in NFT channels while most vegetables will use flood and drain. Grains will generally use sub-irrigation (capillary transport). Racks will be built from extruded aluminum cross-sections that assemble without fasteners. Trays will be either aluminum or plastic sheets, all built to a standard size. Some areas will use motorized tray systems where each tray is passed automatically through a series of racks ending in a harvesting machine. Lighting will be from guided sunlight where feasible and from LED lighting otherwise. LED light sources will be manufactured in the colony's semiconductor facility.
     Edible produce will be routed to food distribution. The specifics depend on culture: do the inhabitants cook their own meals, eat at a cafeteria or some combination of the two? There are some economic questions involved as well, but let's deal with that later. Any harvest waste or surplus that cannot be stored will be converted into feed; part of that stream will be concentrated into high-protein insect meal then mixed back into the rest as appropriate. For production of plastic, sugars and carbohydrates will be fermented into alcohol as a feedstock. The waste from that process is also suitable animal feed. Fibrous production (cotton, bamboo, flax) will be processed as necessary and sent on for spinning and weaving.
     The hydroponics sections will receive waste air from the environmental system. This is high-humidity high-CO2 air that helps maintain an adequate CO2 level for growth (around 1000 ppm). Since plant growth in this system will fix much more carbon than is available from life support, additional carbon must be introduced. All inedible biological waste (including sewage) will be passed through a supercritical water oxidation reactor, which will produce CO2, water and ash (mostly mineral salts). This captures virtually all carbon in the system as CO2, except that which is fixed into structural plastics and similar uses. As a further purification step, the output of these systems will be fed to Spirulina in order to capture any dissolved minerals. The harvested algae can be used as a dietary supplement for people and animals or can be autolyzed into liquid nutrient solution.

     Life support / environmental systems start at the user-facing side with air exchangers. Their purpose is to pass return air through a zeolite bed to extract nearly all CO2, then provide proper humidity and temperature for the supply air. A carbon bed removes odors and VOCs; this is formed from charred plant material and is recycled by burning in the catalytic reactor. Atmospheric bulk is made up with compressed nitrogen tanks as necessary. The hydroponics sections will include oxygen concentrators to provide oxygen-rich air back to residential areas.
     Power to perform this task comes from external systems, and heat extracted plus heat generated by extraction must be rejected to outside systems. Phase-change refrigerants are a convenient way to manage heat transport, so it is expected that either ammonia or light hydrocarbons could be used as working fluids.
     Ultimately all heat produced inside the colony must be rejected to space. This will require a substantial radiator structure that must be sun-shielded. On its way off-station this can be used as process heat for tasks like melting ice or pre-heating ores. The radiators must be highly modular and should limit the amount of coolant in each loop; damage is inevitable so repairs should be straightforward and resources lost to a puncture should be feasible to replace.
     Power for all of this activity comes from concentrating solar PV panels. Reflectors will be built of aluminum, either as sheet or as thin film over plastic. PV cells will be produced in the colony's semiconductor facility and will be actively cooled using the same heat rejection system as environmental (including any process heat applications).

     All of this structure requires a significant industrial base. Materials must be extracted from rock and converted to useful forms, a couple hundred thousand tons of it. The primary tool for this is large-area solar reflectors, so the equipment necessary to build these will be some of the first on the scene. A pre-screen to extract useful metal nodules, volatiles and ice will be done first. The remaining material will be heated and separated into component elements; this process can be stopped while specific oxides are still intact if desired. That yields a stream of nickel-iron, one of volatiles, one of light metals and one of heavier oxides. Trace elements, rare earths and other useful things will be accumulated in the process. Nickel-iron will be separated vial the Mond process, leaving pure iron, pure nickel and assorted iron-phase materials like platinum and rare earths. Rare earth elements and silicon will be processed via zone refining into semiconductor-grade bars and passed to the semiconductor facility to be turned into PV cells, LEDs and microprocessors. Volatiles will be further processed into atmosphere components and water; any hydrocarbons will be fed through the catalytic reactor for reclamation. The leftover slag will be used as shielding material.
     The initial construction of the colony will begin with this kind of industrial equipment, where the first shielding sections will be assembled and the first structural plastics will be prepared. If construction is manned then the initial habitat and greenhouse will start producing plastic as quickly as possible; the greenhouse section would be much larger than necessary for just the construction crew. For an automated 'seed' system, fully chemical means could be used to develop the necessary structural fibers and build the first few floors; with suitable gravity and environmental systems a crew could live and work at the station during the middle construction phase and handle the more complex process of outfitting the internal volume properly as each floor is built. Each new floor would provide higher gravity; the facility could even be spun faster during construction as long as the crew can tolerate it.
     Once a colony is established, it can continue to grow by capturing and processing asteroids into useful material. A wide variety of structures and devices can be built in addition to base materials like water and oxygen. Extra space in the colony can be devoted to food production. Such a facility could serve as a port offering food, medical care, repairs and restocking to spacecraft. Any parts or materials the colony cannot build or acquire for themselves could be bought or traded for valuable metals (platinum, uranium, thorium), bulk PV cells, water, etc.

     The people of the colony will live lives much like we do on Earth, but with a strong reliance on advanced technology for survival. By the time a colony like this is possible, people will be able to live in the worst conditions on Earth: glaciers, deserts and to some extent underwater. It is difficult to predict what might change between now and then; perhaps we will see significant advances in robotic automation to the point that the facility's cleaning and basic maintenance are fully automated. Since I can't guess what the future will look like I've assumed a mostly Earth-normal distribution of occupations, with an emphasis on medical and scientific positions.
     A basic economic system might value a good or service at the number of hours required to create it; time itself then becomes the basis of currency. In one sense, a colony is only possible if the time required to sustain a person is less than or equal to the time it takes them to do their daily work. Using production time as the basis for exchange would provide a starting point; several economic and governmental approaches could be taken from there to make any necessary adjustments and to ensure that enough of the necessary work gets done so the colony survives.
     Construction of such a habitat is likely to be driven for a purpose, whether that be corporate profit, national prestige or religious ideology. It won't be until a significant number of these are built and populations routinely travel among them that people will begin to consider life in space to be normal. Still, there is enough material in the asteroid belt to build colonies for perhaps a few tens of billions of people. Once we include outer bodies and Oort cloud objects that number goes up by a factor of 100 or more. Add in material from various moons and accessible planets and our race's voracious expansion can continue for the next few centuries unabated.



     We present a two-sphere dumbbell configuration of a rotating settlement at Earth-Moon L5. The two-sphere configuration is chosen to minimize the radiation shielding mass which dominates the mass budget. The settlement has max 20 mSv/year radiation conditions and 1 g artificial gravity. If made for 200 people, it weighs 89000 tonnes and provides 60 m2 of floorspace per person. The radiation shield is made of asteroid rock, augmented by a water layer with 2% of the mass for neutron moderation, and a thin boron-10 layer for capturing the thermalized neutrons. We analyze the propulsion options for moving the material from asteroids to L5. The FFC Cambridge process can be used to extract oxygen from asteroid regolith. The oxygen is then used as Electric Propulsion propellant. One can also find a water-bearing asteroid and use water for the same purpose. If one wants to avoid propellant extraction, one can use a fleet of electric sails. The settlers fund their project by producing and selling new settlements by zero-delay teleoperation in the nearby robotic factory which they own. The economic case looks promising if LEO launch costs drop below ~ $300/kg.

1. Introduction

     To live permanently in space, a human being needs air, food, radiation shielding, earthlike gravity, and a suffcient number of fellow settlers and living space. All requirements can be satisfied in rotating free-space habitats made of asteroid or lunar materials as proposed by Gerard O’Neill in his pioneering works. Such unplanetary living is attractive because it offers a way to avoid common natural hazards such as hurricanes, volcanism, earthquakes and wildfires. It is also attractive from the longer term population and economic growth points of view. There is so much material in the asteroid belt (2:4 × 1021 kg) that if made into settlements, it allows several orders of magnitude growth in the human population.

     One could build an orbital settlement in equatorial low Earth orbit (ELEO) with much lower mass than elsewhere, because in ELEO the Earth’s magnetic field protects rather well against cosmic rays and solar protons. However, in LEO there is the risk of orbital debris. For example, recently the insurance company Assure Space stopped offering collision risk coverage policies in LEO [4]. There is also the issue of having to perform a targeted reentry when done with the facility. Letting it fall freely would be a public safety issue for people living near the equator.

     To avoid these issues, in this paper we consider a settlement at the Earth-Moon Lagrange L5 (or L4) point. The L5 point offers Apollo-like short traveltime from Earth, so that the transfer vehicle does not need much radiation shielding. Satellite orbits around ~ 8–10 Earth radii are also an alternative, but they have somewhat larger delta-v for bringing asteroid material than L5. The Moon makes most orbits in ~ 15–150 Earth radii unstable in the long run. L5 is an exception. Distant translunar orbits would also be possible, but they exhibit longer traveltimes from Earth. Longer manned trips increase the mass of the transfer vehicle through the radiation shielding and the life support system.

     The structure of the paper is as follows. First we consider radiation shielding. Then we establish that because radiation shielding dominates the mass, an optimal entry-level configuration is a dumbbell comprising two spheres. We point out that only the radiation shielding mass needs to be sourced from asteroids in the first phase. We analyze a number of propulsion options for moving the material and do costing analysis. We close the paper by discussion and summary.

2. Radiation shielding

     Galactic cosmic rays (GCRs) have higher energies than solar energetic particles. For good radiation protection, the GCR flux must be significantly suppressed, and this requires several tonnes of mass per square meter. At such shielding thicknesses the solar energetic particles are suppressed almost entirely so they can be ignored in the analysis.

     Globus and Strout used the OLTARIS tool to simulate the GCR equivalent radiation doses (millisievert rates) behind various thicknesses of different materials (Table 2). They recommend 20 mSv/year as the equivalent dose level during the solar minimum (of 2010) when the galactic radiation is at maximum, a value which we also adopt here.

     Here we also use the OLTARIS tool. The tool supports two geometries: a slab and a sphere. In the slab geometry, the dose between two adjacent infinite plates is predicted, where each plate has the given shielding thickness. In the sphere geometry, the program predicts the dose at the center of a solid sphere whose radius is equal to the given shielding thickness. The dose predicted using the slab geometry is smaller (typically about two times smaller) than that using the sphere geometry, because in the slab geometry, many of the cosmic rays enter obliquely to the shield and so move a longer distance within the shield. For a hollow sphere, in the limit where the inner radius is much larger than the shell thickness, the dose at the inner wall approaches asymptotically the slab geometry prediction. The dose at the centerpoint of a hollow sphere does not depend on the sphere’s inner radius, so it can be calculated by assuming zero inner radius. Thus for a hollow sphere, the dose at the center is larger than the dose near the walls. The reason is that center-reaching cosmic rays pass through the shell perpendicularly regardless of their arrival direction, whereas near the wall typical rays must pass through the shell obliquely, experiencing more attenuation.

     For radiation shields, Z-grading is in general useful, that is, using high-Z materials as the outer layer and progressively lower Z materials as one goes inwards. We want the bulk of the shield to be asteroid regolith. We also need structural material, which we assume to be steel, which is iron to a good approximation. We put the steel as the outermost layer since iron’s mean atomic mass is larger than that of regolith. Inside the regolith we put a layer of water whose mass is 2% of the mass of the regolith and water combined. It is the intention that this amount of water can be obtained from the asteroid regolith by heating it. If not, the water can be brought from Earth. The dry regolith layer is modeled by OLTARIS’ lunar regolith option.

     Part of the equivalent dose consists of neutrons spallated from the regolith by cosmic rays. The water layer moderates these neutrons. As the innermost layer we add a thin 1 kg/m2 layer of boron-10. (If one wants to avoid isotope separation, one can use 5 kg/m2 of natural boron which is 20% B-10 and 80% B-11.) This isotope absorbs neutrons effciently, especially thermal neutrons. The water moderates the neutrons to be absorbed by the boron.

     Table 1 defines the layers of our wall. This shield was designed to limit radiation to 20 mSv/year equivalent dose at the center of the sphere during worst case, i.e., solar minimum. The equivalent doses were computed for “Female Adult Voxel” phantom.

     For the solar maximum (of 2001) conditions, the equivalent dose is 25% smaller (14.87 mSv/year). For solar minimum, a slab geometry calculation shows that near the inner wall the equivalent dose is 50% smaller (9.97 mSv/year) than at the center. During solar maximum the inner wall equivalent dose drops to 7.53 mSv/year.

     Globus and Strout also require that the absorbed dose for pregnant women be less than 6.6 mGy/year, or 5 mGy per pregnancy. In our case this condition is satisfied since the absorbed dose at the center of the sphere during solar minimum is 4.0 mGy/year.

3. Mass-optimal geometry

     A sphere has the minimal surface area per volume and is thus the best geometry for minimizing shielding mass. To include artificial gravity, we need two spheres rotating about each other in a dumbbell configuration (Fig. 1a). We select a baseline rotation rate of 2 rpm (revolutions per minute), which is probably a conservative choice regarding avoidance of motion sickness. With 1 g artificial gravity, 2 rpm corresponds to rotation radius of R = 230 m. The main structural element is the truss that connects the spheres. It carries the centrifugal load of the heavy spheres. It also acts as the shaft of an elevator that provides access from the living spheres to a central docking port. There are two docking ports for redundancy, upward and downward in Fig. 1. The docking ports are essential because they are the way to enter and exit the settlement. To ease the docking of the connecting spacecraft, the docking ports are located on the axis of rotation.

     To move from one sphere to the other, one can use the elevators, but then one experiences temporary weightlessness in the central region, which is an inconvenience. To eliminate this problem and to provide redundancy in routing, we add a pressurized ring-shaped tube that hosts a road. The ringroad is at constant radial distance from the rotation axis so its user does not need to move uphill or downhill in artificial gravity.

     To produce food as part of the closed ecosystem, we add artificially illuminated greenhouses (Fig. 1). The greenhouses rest on the cylinder on which solar panels are mounted. The greenhouses are served by the ringroad and we place them 90° off the heavy living spheres to make the azimuthal mass distribution more uniform. We assume that food production needs 16 kW of electrical energy per person, so 3.2MWtotal for population of 200. This corresponds to 2500 kcal per day per person of food plus 30% margin, and 1% effciency in converting greenhouse electrical energy into edible energy of the crops. Most of the energy is dissipated inside the greenhouses and radiated into space from their roofs. To keep the heat transfer passive and thus reliable, the radiator must be cooler than the greenhouse. At radiator temperature of +4 C, the emitted thermal power per area is 300 W/m2 at emissivity of 0.9. Thus to dissipate 3.2 MW of power one needs 10,560 m2 of greenhouse roofs. The greenhouses are stacked in as many layers as is needed to yield the wanted amount of radiated cooling power per roof area. The green areas in Fig. 1b show the greenhoused areas. Pressure containment of the greenhouses also contributes to structural mass. The mass is proportional to greenhouse total volume. To calculate the volume, we assume 50 W/m3 of volumetric power dissipation and 1 bar greenhouse pressure.

     Agriculture is performed robotically because the greenhouses are outside of the thick radiation shields. We make an assumption that agriculture works despite GCR. To what extent this is true depends on many factors, one of which is plant lifetime. Plants that grow rapidly from seeds are less likely to have problems due to radiation-induced mutations than long-lived trees, for example. More research is needed on this point. We place the greenhouses so that they can be served by the ringroads. The ringroads are used not only by people, but also by wheeled robots that move crops to the living spheres and human wastes back to the greenhouses. The indicated area of the cylindrical solar panel in Fig. 1b is larger (by factor of 2) than what is needed to produce 3.2MW, because the settlement needs power also for other purposes than food production. The spin axis is perpendicular to the ecliptic plan so that the solar panels are all the time optimally illuminated. The power system is a rather small fraction of the total mass, which is dominated by radiation shielding mass (97 %) and structural mass (2.6 %).

     Figure 2 shows a cross-sectional view of the spheres. The inhabitants live in the centrifugally produced artificial gravity, with their heads towards the axis of rotation. Each sphere has inner diameter of 33 m. In this section we give the baseline values of the parameters and motivate them later. With effective room height of 3 m it contains ten floor levels and provides 6000 m2 of floorspace area for its 100 inhabitants so that each person has 60 m2 of living area. For example, it can be 25 m2 of private area per person, 32 m2 of public and working areas including corridors, and 3 m2 (5 %) taken by walls. Tables 2 and 3 list the main parameters of the 200 person settlement.

     For relatively small settlements such as 200 inhabitants, the density of the regolith affects the mass: the denser the shield, the less of it is needed because the sphere’s radius is not that much larger than the shield thickness. Bulk densities of asteroids vary in rather wide range. Asteroid Eros is stony and with bulk density of 2.67 g/cm3. Smaller stony asteroids are less compressed by gravity and they can have lower densities; for example Itokawa has 1.95 g/cm3. The minerals themselves would allow even higher densities. The most abundant minerals are SiO2 whose density is 2.65 g/cm3 and MgO which is 3.6 g/cm3. Iron-rich minerals are often even denser. We use the value 2.6 g/cm3 which is a bit less than Eros’ bulk density. Reaching this density requires the fragmented rock to be compressed by vibrating, pressing or melting.

     The mass effciency of radiation shielding increases if the population is increased, because the spheres become larger. When making the spheres larger, however, the difference in artificial gravity between the top and the bottom increases, unless one also increases the rotation radius. When scaling up we require that the maximum gravity is not more than 10% larger than the average, and the minimum is not more than 10% smaller.

     Increasing the rotation radius increases the structural mass fraction, because the sphere-supporting trusses become longer. We propose that the structural mass is piano wire steel. This material is 99% of iron, and iron is abundant on asteroids. In the first phase the structural material is brought from Earth, but in later stages it can be sourced from asteroids. We also set a requirement that the structural fraction does not increase beyond 17 %, because the majority of stony asteroids have more iron than this limit. Nothing prevents an even larger iron fraction, but the only drawback is that then one may have to start abandoning some of the asteroid material as waste. When the rotation radius is increased to 1.6 km, the 17% limit is reached. If one wants to further increase the population without increasing the max/min gravity difference beyond ±10 %, one can add more spheres. Configurations of up to ~ 30 spheres are still more mass effcient than an uninterrupted torus.

     Figure 3 shows the rotation radius, mass per person, structural mass (steel) per person and the number of spheres as a function of population. For each population, the mass-optimal configuration was found automatically. The rotation radius is the constant 230 m up to 600 people, after which it grows in order to avoid more than ±10% difference in gravity between sphere top and bottom. The mass per person is inversely proportional to sphere radius, so that it is proportional to power -1/3 of the sphere volume and population. For small spheres, the dependence is slightly steeper because the radiation shield thickness is not negligible in comparison to sphere radius in this regime. For most of the population range, the structural mass per person is almost constant. This is because two competing effects nearly cancel each other. A larger rotational radius makes the truss longer, but it also enables larger spheres which yields less radiation shielding mass per person and therefore smaller carried load for the truss, per person. For population less than 600, the rotation radius is constant because we do not allow faster than 2 rpm rotation rate.

     With the employed parameters, two is the optimal number of spheres up to population of 2 × 105.

     Table 4 summarizes the employed requirements.

4. Material sourcing

     Most of the material is asteroid rock or regolith used for radiation shielding. This fraction is 97% in the baseline case of 200 people. Thus one can already reach asteroid mass ratio of 30 [= 97/(100 - 97)] by bringing only rock from the asteroids.

     Most of the rest is structural material and most of it is used for the two trusses that support the living spheres. Tensile strength is the most important mechanical property required; compressive strength is less important. We recommend to use piano wire steel, which is 99% iron. The tensile strength is 2.6-3 GPa and the production process stems from the 19th century so it is not high-tech. If the structural material is sourced from asteroids, the mass ratio increases to 170 in the baseline case of 200 people (Tables 2 and 3). Sourcing structural material from asteroids requires strict quality control because the structural parts are life-critical.

     To increase the mass ratio further, one could import water and carbon from asteroids as raw materials for growing the biomass that circulates between plants and people.

5. Propulsive transfer of materials

     Most of the mass (97% for a 200-person dwelling) is radiation shielding, for which there are no structural or other requirements so that it can be any unprocessed or processed asteroid rock. Thus the main challenge is propulsion: how to transfer material from asteroids or the Moon to the L5 orbit. Here we briefly analyze some of the potential methods.

5.1. Lunar material

     Lunar material could be lifted by an electromagnetic mass driver as envisioned by O’Neill. The mass driver would be a large investment. The electrical energy of the shot must be stored in large capacitor banks, which is a major cost item. The fixed shooting direction tends to reduce the flexibility regarding target orbit. The centralized nature of the facility is a potential reliability concern.

     Lunar material could also be lifted by a sling, which would be much lighter infrastructure than the electromagnetic mass driver and it avoids the use of capacitor banks. However, because the Moon rotates while the plane of the rotating sling stays inertially fixed, the sling crashes to the surface after some time, unless prevented by propulsion or other means. The time to crashing depends on the parameters, but is typically inconveniently short.

     To lift lunar material, it is often proposed to make LH2/LOX propellant from the water ice that exists in the polar lunar regions. However, the estimated H2O resource is only a few times 1011 kg. This amount is not suffcient for long-term use. For example, a settlement with 106 people corresponds to mass of 3.5×104 kg per person (Fig. 3), i.e. total mass of 3.5×1010 kg, which is already ~ 10% of the total lunar water resource.

5.2. Asteroid material transferred by O2 electric propulsion

     As shown recently, the so-called FFC Cambridge electrolytic process can be used to separate earthly, lunar or asteroid rock into oxygen gas and a solid residue comprising metals and silicon. The oxygen can be used as Electric Propulsion propellant. The O2 Electric Propulsion technology is currently under development in the context of Air-Breathing Electric Propulsion, which is enabling technology for very low orbiting satellites that are naturally immune to orbital debris and do not generate new debris.

     The FFC Cambridge process requires calcium chloride electrolyte. The electrolyte can be recycled, but the initial amount must be brought from Earth. Chlorine is a rather rare element on asteroids. In the proof of concept experiment of Lomax et al., 1.6 kg of CaCl2 was used to process 30 grams of lunar regolith simulant. According to the newest results, ~ 75% of the total oxygen was extracted after 16 hours in the reactor. Thus, during one year, 545 batches can be processed, altogether processing 16.4 kg of regolith and liberating 4.3 kg of O2, if the total oxygen content of the rock is 35 %. Thus for one year, the mass ratio (O2 : CaCl2) is (4.3 : 1.6) = (2.7 : 1). Because the process demonstration was intended only as a proof of concept and was not optimized, it is likely that the amount of electrolyte and/or the throughput time can be improved, maybe significantly.

5.2.1. Delta-v from asteroids

     To estimate the delta-v from a given asteroid to L5, we compute the optimal Hohmann transfer delta-v from the asteroid to circular zero inclination 1 au heliocentric orbit, consisting of two or three impulsive burns, whichever strategy gives the smallest delta-v. The burns set the aphelion, the perihelion and the inclination. In reality, since we are considering low-thrust Electric Propulsion, the burns are not impulsive and therefore they are not optimal. On the other hand, in reality one could make use of lunar flyby maneuver to kill up to 1.6 km/s of of the incoming hyperbolic excess speed. Because the effects work in opposite directions regarding the needed delta-v, we think that the impulsive Hohmann transfer delta-v gives a useful approximate measure of the low-thrust delta-v.

     Figure 4 shows the cumulative mass in known asteroids sorted by the delta-v computed as just explained. The masses in Fig. 4 are based on the tabulated absolute magnitudes in JPL Small Body Database by assuming albedo of 0.15, density of 2 g/cm3, and spherical shape. The cumulative mass jumps at certain large and well accessible asteroids, some of which are marked in Fig. 4. To build the first settlement, we need 78,000 tonnes of asteroid rock, which is only little larger than the estimated mass of asteroid 2000 SG 344, which in one source has been estimated as 7.1 × 107 kg. To be conservative, however, we shall assume the use of asteroid Apophis whose mass is 3 orders of magnitude larger. Apophis is also one of the potentially hazardous asteroids, so reducing its mass is not harmful from the planetary defense perspective.

     The delta-v from Apophis is 3.37 km/s. For the transfer spacecraft using O2 electric propulsion, we assume the parameters listed in Table 5.

     The assumed specific impulse of 2500 s is on the high end of Hall thrusters and low end of gridded ion engines. The assumed effciency of 40%is somewhat lower than the effciency of state of the art xenon Hall thrusters which are typically above 50 %. We motivate the assumption by the fact that O2 is less optimal propellant than xenon.

     The power per mass ratio of 100 W/kg is typical to contemporary solar panel power systems. The thruster is typically quite lightweight in comparison. We assume a passively cooled LOX tank. The tank walls can be thin since the pressure is low and the tank does not have to withstand launch vibrations or impulsive accelerations. We obtain the result that 13% of the initial rock must be turned into oxygen, so that the ratio (propellant : rock) becomes (0.15 : 1). The 13% corresponds to only about one third of the total oxygen content of typical asteroid rock.

     Thus, the ratio of payload to dry mass of the transfer spacecraft is 23. If the spacecraft is used for multiple trips (1.5 year transfer followed by shorter triptime for going back to the asteroid), the effective mass ratio is increased.

5.3. H2O electric propulsion

     A drawback of the FFC Cambridge process is that the CaCl2 electrolyte must be imported from Earth. Instead of extracting O2 from rock, one can use a (C-type) water-rich asteroid, extract water by heating, and use the H2O for Electric Propulsion. For Electric Propulsion thrusters, O2 and H2O are rather similar. Both are light molecules and when in hot and ionized state, they are chemically active.

     The amount of water in the material is likely to be less than what is needed for propulsion, unless the specific impulse is chosen to be particularly high or the asteroid is particularly wet. Thus one must probably be prepared for mining and drying more material than one transports. To handle the waste material in the most sustainable way, one can create an artificial asteroid of the abandoned material and set it to orbit the parent asteroid. Then the dried-up material is not wasted permanently, but it remains most easily accessible to those future miners who prefer water-independent transportation techniques such as FFC Cambridge.

     Water is easier to store than O2 because it is storable as a room temperature liquid.

5.4. Hydrogen reduction of oxides

     The Swedish-Finnish steelmaking company SSAB intends to replace traditional carbon reducing agent in steelmaking by hydrogen, thus enabling CO2-free production of steel. Hydrogen gas reacts with iron oxides to form reduced iron and water. The water is electrolysed to extract the oxygen. The hydrogen is injected back into the reactor.

     Ordinarily, hydrogen reduction is applicable only to iron oxides. Turning the hydrogen to atomic or ionized form might also allow reduction of other oxides. This is relevant for asteroids because most of the oxygen is bound in silicon and magnesium oxides.

     The benefit relative to FFC Cambridge is that there is no need to import process chemicals from Earth. Hydrogen is needed, but it can be circulated, and the initial amount can be obtained from the water that exists in most asteroids to some extent.

5.5. Electric sail

     The solar wind electric sail is a propellantless propulsion method, based on the momentum flux of the solar wind. The E-sail consists of long and thin metallic tethers that are kept in high positive potential by an onboard high voltage source and electron gun that pumps out negative charge from the system. The maximum thrust of an E-sail depends on materials and other parameters, but is roughly of the order of ~ 1 newton. With acceleration of 0.1 mm/s2 as in Table 5, the single transfer spacecraft can thus move 10 tonnes of material. To build a 200 person settlement weighing 78,000 tonnes (Table 2), one needs ~ 105 trips. Thus one needs a large fleet of E-sail spacecraft.

     The E-sails are tens of kilometers in diameter. Thus, traffc congestion at the asteroid and at the settlement construction site become issues. The problem can be avoided by moving the materials first by traditional spacecraft which rendezvous with E-sails once there is enough free space around. This increases the complexity to some extent, but the scheme remains effcient since the majority of the delta-v comes from the propellantless E-sail.

     A fully autonomous optical navigation system is preferred. Otherwise operations and radio communication costs can become high, because the fleet is large. An autonomous optical navigation system was in principle demonstrated already in Deep Space 1 in 1998.

     The E-sail tethers are made of multiple wires to be tolerant of the natural micrometeoroid flux. However, centimeter-sized particles can break all the subwires of a tether at once. Debris possibly generated by the asteroid mining is thus potentially dangerous for the E-sails. Making rendezvous with the E-sails far enough from the asteroid also mitigates this problem.

5.6. Comparison of methods

     Table 6 summarizes the benefits of the four propulsion options for moving asteroid materials.

Table 6: Comparison of propulsion options for moving asteroid materials (Section 5).

5.7. Space manufacturing to increase the mass ratio

     The Dutch-Luxembourgian company Maana Electric is developing a self-contained automatic factory, built in a standardsized shipping container that takes in desert sand robotically and produces finished solar panel arrays, installing them in the surrounding desert. The company targets not only Earth, but also the solar system. If this technology proves to be practical, one could use it to produce solar panels for the transfer vehicle from the mined asteroid regolith, thus reducing the mass that must be brought from Earth. Structural parts of the transfer vehicle may be possible to 3-D print from the metal-rich residue of the FFC Cambridge process.

     Making parts of the transfer vehicle from asteroid materials is simpler than making parts of the settlement, because the transfer vehicles are unmanned and redundant. Thus a failure of one of them is not catastrophic. However, if strict quality checking standards are imposed, then it becomes feasible to also make structural parts of the settlement from asteroid materials. Our baseline structural material is piano wire steel. Piano wire steel is 99% iron, which is abundant on asteroids. Other structural materials such as magnesium alloys or basalt or silica fibers can also be considered.

6. Costing of 200 person settlement

     Table 7 gives the masses and launch costs of the 200-person settlement. We assume FFC Cambridge (subsection 5.2) and that the asteroid surface miners and the O2 extraction factory together can weigh up to 3000 tonnes. The contribution of surface miners is likely negligible in comparison with the factory. In subsection 5.2 we found that at the current unoptimized prototype level of the FFC Cambridge process, one unit of Earth-imported CaCl2 electrolyte produces 2.7 units of O2 per year. From Table 5, transportation of one mass unit of asteroid rock needs 0.15 mass units of O2 propellant. Thus, transportation of one mass unit of asteroid rock needs 0.15/(5×2:7) = 0.011 units of Earth-imported CaCl2, if the production period is taken to be 5 years. Thus, transportation of 96,576 tonnes of rock needs 1,062 tonnes of CaCl2, which is 35% of the 3,000 tonnes allowed for the O2 factory. Recall that this is based on the presently existing unoptimized FFC Cambridge process of Lomax et al..

Table 7: Mass and launch cost budget for 200-person settlement, assuming O2 propellant extraction but no other space manufacturing.

     In Table 7 we assumed — conservatively — that chemical propulsion is used to push the payloads from LEO to L5 so that the mass originally launched to LEO is 3 times larger than the mass that ends up in L5. Falcon 9 costs $3000/kg to LEO in the default partially reusable mode. The fully reusable Starship rocket might be as much as 100 times more cost-effective ($30/kg). Adopting that, the launch cost per settler becomes $4.2M.

     Predicting the eventual per-kilogram cost of Starship or its competitor is challenging at the moment. One recent statement of SpaceX speculated with only $2M cost per launch, i.e. $13/kg. To cover the uncertainty, in the Discussion part we shall also consider an intermediate price case of $300/kg.

     If the launch is e.g. 20% of the total cost (the other being designing and building the settlement and the asteroid mining chain for obtaining the radshield rock), each settler needs an initial capital of 5 × 4.2M = $21M. Settlers can earn their investment back and more, since once living at L5, they can teleoperate the nearby robotic settlement production factory complex in zero-delay mode. Thus the first group of settlers earns money by producing new settlements. They do it more effciently than from ground because they avoid the 2.6 second free-space communication delay in teleoperation.

     As was remarked above in subsection 5.7, solar panels and structural parts (including tanks) of the Electric Propulsion transfer spacecraft could be made from asteroid resources. Structural parts of the O2 factory could also be be made of asteroid-derived steel. Once proper quality control processes are in place, structural parts of the settlement can also be made of asteroid-derived piano wire steel. In Table 8 we show an example where space manufacturing has cut the net Earth-imported mass to 20% of the original.

     That is, under the stated assumptions space manufacturing reduces launch costs by a factor of 4.2.

Table 8: Same as Table 7 but with space manufacturing.

7. Discussion and summary

     Radiation shielding dominates the mass of beyond-LEO settlements. The assumed 9 t/m2 shield provides max 20 mSv/year equivalent dose environment. If the shield is made thinner, the effective dose would increase rapidly.

     For large settlements where the shield thickness is negligible in comparison with the sphere radius, the mass density of the radshield does not matter. But for 200-person settlements it does play a role. We assumed density of 2.6 g/cm3 which is the same as the bulk density of larger asteroids such as Eros. Reaching this density probably requires some technical effort, for example making bricks out of it by pressing, sintering or melting.

     It is advantageous to separate the water and to put it in its own layer, inward of the regolith. In this way, the hydrogen of the water moderates the spallated neutrons so that they can be captured by a thin layer of boron or other neutron absorber. A 2%water content is suffcient for moderating the neutrons. Water is also intrinsically a better shield material than rock, so it is better if more is available. To be conservative, in the calculations we assumed only 2 %.

     For moving the materials from asteroids there are several propulsion options. Extracting O2 from rock by FFC Cambridge and using it for Electric Propulsion is a possible method. A drawback is the necessity to import the CaCl2 electrolyte from Earth. Finding a water-rich asteroid and using H2O as Electric Propulsion propellant is one of the other alternatives. The E-sail is also one option. It needs no propellant extraction, but requires a large fleet size.

     Tables 7 and 8 show the launch cost per person without and with space manufacturing, and with present (Falcon 9) and future (Starship) launch vehicles. Introduction of space manufacturing (under certain assumptions) reduces launch costs by a factor of 4.2, and replacing Falcon 9 by the Starship cost goal of $30/kg reduces them by a factor of 100 (Table 9):

Table 9: Launch costs per settler with various launch prices and with or without space manufacturing.

     If Starship reaches $30/kg, the first 200-person settlement could probably be built without space manufacturing. Each settler might need initial capital of ~ $21M, 20% of which is the launch. Such initial capital sounds realistic for 200 settlers. The money is used to build and launch the parts of the settlement as well as the asteroid mining infrastructure needed to make its radiation shields. Once the settlers have moved in, they can earn back the money by selling new settlements produced by their robotic mining and manufacturing infrastructure, which they are now in the position to use more smoothly by delayless teleoperation.

     In Table 9 we also list the LEO launch price intermediate case of $300/kg, which is 10 times smaller than Falcon 9, but 10 times higher than the Starship goal. Because Starship launches 150 tonnes per launch, $300/kg corresponds to each Starship launch costing $45M, which is about the same as the present Falcon 9 launch cost in its default partially reusable configuration ($50M). Given that Starship is fully reusable, its launch should cost less than that of Falcon 9, because the fuel cost is only ~ $2M per launch. In the $300/kg case, the launch cost per settler is $10.3M if space manufacturing is used. Such figure sounds realistic for 200 settlers. If space manufacturing is not used, then the launch cost is $42.6M per settler. This initial cost level is also probably feasible for 200 settlers, provided that there is a credible roadmap for lowering costs in the future by implementation of space manufacturing and/or by lowering launch costs.

     We summarize our main findings:

  1. The radiation shield against GCRs dominates the mass (97% in the case of 200 person settlement). It can be asteroid rock.
  2. A sphere is the optimal shape for radiation shielding. Hence the two-sphere dumbbell configuration is best.
  3. As structural material we recommend piano wire steel.
  4. Several propulsion options to transport rock from asteroid to L5 are viable.
  5. To cut costs by space manufacturing, one can make solar panels and structural parts of the transfer vehicles and the settlement from asteroid materials.
  6. The economic case looks promising if LEO launch cost is $300/kg or below.
  7. The settlers make money by constructing more settlements by teleoperating a nearby robotic factory with negligible communication delay.
From SHIELDED DUMBBELL L5 SETTLEMENT by Pekka Janhunen (2020)

Asteroid Bubble

Larry Niven popularized the "asteroid bubble" technique of creating a huge space habitat.


The next step up in size is the hollow planetoid. I got my designs from a book of scientific speculation, Islands in Space, by Dandrige M. Cole and Donald W. Cox.

STEP ONE: Construct a giant solar mirror. Formed under zero gravity conditions, it need be nothing more than an Echo balloon sprayed with something to harden it, then cut in half and silvered on the inside. It would be fragile as a butterfly, and huge.

STEP TWO: Pick a planetoid. Ideally, we need an elongated chunk of nickel-iron, perhaps one mile in diameter and two miles long.

STEP THREE: Bore a hole down the long axis.

STEP FOUR: Charge the hole with tanks of water. Plug the openings, and weld the plugs, using the solar mirror.

STEP FIVE: Set the planetoid spinning slowly on its axis. As it spins, bathe the entire mass in the concentrated sunlight from the solar mirror. Gradually the flying iron mountain would be heated to melting all over its surface. Then the heat would creep inward, until the object is almost entirely molten.

STEP SIX: The axis would be the last part to reach melting point. At that point the water tanks explode. The pressure blows the planetoid up into an iron balloon some ten miles in diameter and twenty miles long, if everybody has done their jobs right.

The hollow world is now ready for tenants. Except that certain things have to be moved in: air, water, soil, living things. It should be possible to set up a closed ecology. Cole and Cox suggested setting up the solar mirror at one end and using it to reflect sunlight back and forth along the long axis. We might prefer to use fusion power, if we’ve got it.

Naturally we spin the thing for gravity.

Living in such an inside-out world would be odd in some respects. The whole landscape is overhead. Our sky is farms and houses and so forth. If we came to space to see the stars, we’ll have to go down into the basement.

We get our choice of gravity and weather. Weather is easy. We give the asteroid a slight equatorial bulge, to get a circular central lake. We shade the endpoints of the asteroid from the sun, so that it’s always raining there, and the water runs downhill to the central lake. If we keep the gravity low enough, we should be able to fly with an appropriate set of muscle-powered wings; and the closer we get to the axis, the easier it becomes. (Of course, if we get too close the wax melts and the wings come apart…)

From BIGGER THAN WORLDS by Larry Niven (1974)

Confinement Asteroid is unique.

Early explorers had run across a roughly cylindrical block of solid nickel-iron two miles long by a mile thick, orbiting not far from Ceres. They had marked its path and dubbed it S-2376.

Those who came sixty years ago were workmen with a plan. They drilled a hole down the asteroid’s axis, filled it with plastic bags of water, and closed both ends. Solid fuel jets spun S-2376 on its axis. As it spun, solar mirrors bathed it in light, slowly melted it from the surface to the center. When the water finished exploding, and the rock had cooled, the workmen had a cylindrical nickel-iron bubble twelve miles long by six in diameter.

It had been expensive already. Now it was more so. They rotated the bubble to provide half a gee of gravity, filled it with air and with tons of expensive water covered the interior with a mixture of pulverized stony meteorite material and garbage seeded with select bacteria. A fusion tube was run down the axis, three miles up from everywhere: a very special fusion tube, made permeable to certain wavelengths of light. A gentle bulge in the middle created the wedding-ring lake which now girdles the little inside-out world. Sunshades a mile across were set to guard the poles from light, so that snow could condense there, fall of its own weight, melt, and run in rivers to the lake.

The project took a quarter of a century to complete.

Thirty-five years ago Confinement freed the Belt of its most important tie to Earth. Women cannot have children in free fall. Confinement, with two hundred square miles of usable land, could house one hundred thousand in comfort; and one day it will. But the population of the Belt is only eight hundred thousand; Confinement’s score hovers around twenty thousand, mostly women, mostly transient, mostly pregnant.

From WORLD OF PTAVVS by Larry Niven (1966)

      I had read up on the place. Vapaus had started out in life as a rather routine lump of stone and rock floating through space on an orbit that brought it within easy range of New Finland. The Finns had dragged it into orbit of the planet and set to work making an orbiting industrial base and shipping port out of it.

     The first step was to hollow it out, and trim the oblong lump of rock into a cylinder.
     The New Finnish system had several gas giant planets in its outer reaches. The closest-in giant had a small ice moon far outside its gravity well. This moon was mined for ice, which was towed to the asteroid's orbit.
     The interior of the asteroid was by then a cylindrical hollow, which the Finnish engineers proceeded to pack with ice. The mine shafts were sealed with pressure locks, and the asteroid was then set spinning.
     Giant solar mirrors were brought into position around the asteroid, and tremendous amounts of light and heat were focused on it.

     The stone melted like butter.

     The heat-pulse hit the ice-filled interior. The ice boiled off into super-heated steam and inflated the asteroid the way a child's breath inflates a balloon.
     The engineers having done their math properly, the pressure locks blew off at the right moment. Ninety percent of the water escaped to space, and then the pressure lock resealed. The rest of the water was retained to become the basis of Vapaus's artificial ecology.
     When the molten rock cooled, the Finns had an inside-out world about six times the size of the asteroid they had started with. They had been the first to try the technique with a stony asteroid. (Others had "inflated" iron-nickel asteroids, but those satellites had annoying problems with magnetic eddy fields and electrical effects brought on by spinning up megatons of conductive material.) (I'm not sure if stone has enough tensile strength)

     The scrap rock was dragged down into a lower orbit and the solar mirrors melted it all down into one lump of slag, which never got any name other than "The Rock". The Rock made a good base for a lot of processes that relied on zero-gee, and was also a handy orbital mine.
     Joslyn and I had worked out a plan that was based on the fact that Vapaus had been inflated. It was known that the rock had bubbled in places. It ought to be possible to find a bubble, dig in through it, and reach the interior. I hoped so, anyway. Otherwise, I was dead. I sighed. Best not to worry about that little possibility. It was going to be true of just about everything I did for the foreseeable future.

From THE TORCH OF HONOR by Roger MacBride Allen (1985)

      February 15th, 2099: Our first order of business was to set up the first primitive habitat. Daddy calls it a "Shake and Bake" habitat (although the computer talks about the "Cole Technique"). I don't see where the shaking comes into it, but the baking is easy to understand.
     First, Daddy, Uncle Wes, and Mr. Tanaka dug a hole down to the very core of Haven Rock. There they placed a giant tank of water, and then sealed the tunnel back up.
     Then we deployed the Portable Solar Concentrator. The Concentrator is a giant disk made of two sheets of plastic sealed together at the edges only. One layer is transparent plastic, the other, aluminized mylar. When it was deployed, the modest amounts of air trapped inside were enough to completely inflate it in the vacuum of space. It wound up bulging on both sides, shaped kind of like a magnifying lens. Now if you point it at the sun, you have a reflective Solar Concentrator several kilometers across. The focus is not real good; not really a point, but instead a smeared-out streak several meters long. But it was good enough for our purposes.
     Uncle Wes and Daddy maneuvered the Concentrator until Haven Rock was at the focus. The asteroid, slowly turning on its axis, roasted like a pig on a spit. Over a few days, the surface actually began to glow red, and soften. But the heat traveled only very slowly through the body of the big rock. The surface was yellow-hot, and thoroughly molten before the water tank at the core was very much above the boiling point.
     But today the steam pressure in the tank finally became too great, and the tank ruptured. The steam blew the molten glob of nickel-iron into a huge bubble of low-grade steel. I saw Daddy holding his breath, praying that there wouldn't be a blowout on one side. But we lucked out. The globe wound up a bit on the lumpy side, but stayed intact. It rapidly hardened as it ceased expanding, and now we had the basic structure of our habitat.

     February 22nd, 2099: We've spent the last few days starting to outfit the habitat. The first thing we did was turn loose the replicators.
     The replicators were machines not much bigger than a trailer home, and essentially were mini-ore refineries/manufacturing plants. Given solar power and a supply of asteroidal ore, they can make all of the components of their own design, and then assemble those components into a duplicate. Two can make four... four can make eight... you get the picture. In no time at all you can ramp up to any level of industrial productivity desired.
     While that was going on, Uncle Wes used laser cutters to carve a great hole out of the Haven Rock sphere. The hole is where a giant window about ten city blocks in area goes. Daddy and Mr. Tanaka have almost completed assembly of the big parabolic mirror which will gather sunlight, and focus it though the window and into the interior of our big steel bubble. The mirror is much larger than the mirrors I've seen on the kind of habitats I'm used to. But the sunlight's dimmer this far out from the sun, so we have to scale up our collecting mirrors accordingly. The habitat looks so small attached to this giant reflector.
     Another parabolic mirror (a much smaller one) will be mounted at the very center of our new world on three cables. This one will reflect the sunlight coming in through the window to evenly illuminate the inner surface.

     March 3rd, 2099: Using another asteroid on a turntable, we've been spinning Haven Rock up to speed. Soon the centrifugal force will reach 1G at the equator. At the same time, we've been feeding the oxygen from the ore-smelting operation into the interior. That, plus a bit of nitrogen and water vapor, gives us a breathable atmosphere.

     March 5th, 2099: Wilbur and I watched with interest from the William Penn as Momma and Daddy installed the chair-lift system which will enable us to easily travel from the axis of Haven Rock down to where there's gravity. We're starting to look forward to riding that chair-lift, as we've been cooped up on this tiny little passenger transport for far too many months.

     March 15th, 2099: Today Daddy let Wilbur and I into the interior of Haven Rock for the first time. It's pretty ugly. The interior surface is all dark grey; runny and streaky with melted slag. But a bit of topsoil and vegetation will fix that. For now, Wilbur and I are just mighty glad to be off of that dang ship, and out in the sunshine and open spaces where you can just run and run and run. Which we did, till we collapsed, giggling and exhausted.
     Daddy sure looked happy watching us have fun.

     March 16th, 2099: Now we start on the landscaping. The robots have a simple way of getting the asteroidal soil to us: they just dump it away from the axis, and let it come sliding and rolling down the curving inner surface of the sphere. Then Wilbur and I use our little electric bulldozers to push it around to where it's needed.

     March 17th, 2099: I'm really ticked off at Daddy today. I was pushing some soil quite a ways up on the sphere when he told me that I'm pushing it too high, and to just keep following the equator. I found out to my dismay Daddy has no intention of landscaping the entire inner surface of the habitat, only a narrow ribbon of land running around the equator.
     "No!" I cried. "It'll look ugly! This melted slag junk is so horrid-looking! At least let me go up to 45 degrees! Please!"
"No, sweetheart," he responded. "No more than 25 degrees on either side." Then he hopped up on the bulldozer to put an arm around my shoulder. "You have to understand, we aren't going to be in this habitat forever. This is just a place to live until we can get well-established financially. Once we're far enough out of the red, we'll be building a much bigger, much better habitat. Haven Rock's going to be a bit on the primitive side, but we won't be here long, I promise. At least not past the point where you're having kids who can complain to you about it!"      Then he's laughing, but I'm not going to crack a smile. Right now, I'm not thinking about having kids. I'm thinking about what an awful-looking place this is going to be.
     This s**ks.

     April 11th, 2099: We don't have separate agricultural rings on this podunk little habitat, so we're going to grow our crops and raise our animals in the same main sphere where we're supposed to live. I had so looked forward to finally getting away from the stench of the Animals Deck back on the Penn for once and for all, but I bet this dinky little place will smell all over. This is insane.
     At least now that the grass is starting to grow, this place has greened up a bit (at least along one narrow little strip). But now that farmlands, feeding pastures, and some small buildings are going in, I'm just starting to grasp how tiny this ball is. It's only about a kilometer in circumference; no bigger than the kind of Bernal Sphere grandma used to live in when she was a little girl. Someone can be on the completely far side of the sphere, and if you look at them directly overhead (and shield out the glare from the central solar reflector) you can actually see them waving back at you!
     And our homes aren't really homes at all, just fiberglass shacks. Daddy said all we need is a bit of privacy, and something to keep the rain off our heads (not real rain, it's just water from a sprinkler system). Since there'll never be any high winds, and no seasonal temperature variations, he said it's all we need for now.
     "But Daddy, we've got to have seasons! It'll be so dull around here without Spring or Fall!" But Daddy acted like I didn't even say anything.
     "We'll have seasons in the next habitat, dear," Momma said.
     The situation continues to get s**kier by the minute.

by Mike Combs (1997)

      Lamorak puffed smoke appreciatively and crossed his lanky legs. His hair was powdered with gray and he had a large and powerful jawbone.

     “Home-grown?” he asked staring critically at the cigaret. He tried to hide his own disturbance at the other’s tension.

     “Quite,” said Blei.

     “I wonder,” said Lamorak,” that you have room on your small world for such luxuries.”

     (Lamorak thought of his first view of Elsevere from the spaceship visiplate. It was a jagged, airless planetoid, some hundred miles in diameter—just a dust-gray rough-hewn rock, glimmering dully in the light of its sun, 200,000,000 miles distant. It was the only object more than a mile in diameter that circled that sun, and now men had burrowed into that miniature world and constructed a society in it. And he himself, as a sociologist, had come to study the world and see how humanity had made itself fit into that queerly specialized niche.)

     Blei's politely-fixed smile expanded a hair. He said, “We are not a small world. Dr. Lamorak; you judge us by two-dimensional standards. The surface area of Elsevere (31,416 square miles) is only 3/4 that of the State of New York, but that’s irrelevant. Remember, we can occupy, if we wish, the entire interior of Elsevere. A sphere of 50 miles radius has a volume of well over half a million cubic miles (524,000 cubic miles). If all of Elsevere were occupied by levels 50 feet apart, the total surface area within the planetoid would be 56,000,000 square miles, and that is equal to the total land area of Earth. And none of these square miles, doctor, would be unproductive.”

     Lamorak said, “Good Lord,” and stared blankly for a moment. “Yes, of course you’re right. Strange I never thought of it that way. But then, Elsevere is the only thoroughly exploited planetoid world in the Galaxy; the rest of us simply can’t get away from thinking of two-dimensional surfaces, as you point out.

From STRIKEBREAKER by Isaac Asimov (1957)

But It Probably Won't Work

I hate to, ahem, pop your bubble, but the concept has problems.

Andrew Love notes that if the asteroid is made of stone, once you start to spin it for artificial gravity it will immediately fly into pieces. As he puts it "there are no stone suspension bridges". Stone is heavy and weak, particularly in tension. A 100 meter external radius asteroid made of granite and spun up to 1 gee would put the granite under stresses about twice the expected strength of granite. You will note that Larry Niven specifies a asteroid composed of nickle-iron.

But it gets worse:

ADAM CROWL (Starship Designer with Icarus Interstellar) :

Inflating a semi molten mass as imagined won’t work very well. Natural asteroidal material isn’t even in properties. Any flaw or weakness will be a blow out. Imagine megatons of tumbling metal...


Why is the idea so popular in even hard scifi?


Because it’s repeated uncritically. It goes back to Dandridge Cole and was popularized by Larry Niven’s “Known Space” stories as it’s how the Belter Confinement asteroid was made. Cole had lots of big ideas, but not all workable.


As RocketCat has been reminding you every five minutes Every gram counts. So when building a structure you want the sweet spot between the strongest struture and the lowest mass.

Structures are generally build out of compression members (i.e., girders or struts) and tension members (i.e., cables or tendons). On a planet or moon with an appreciable gravity there is a maximum size limit on compression members, since they have to support their own structual weight as well as whatever they are propping up (does not apply in free-fall since it has no weight). Tension members have no such limit, they can theoretically be of any size.

Compression members push, while tension members pull.

One technique right in the sweet spot is the radical art of "tensegrity" or "floating compression". This was invented in the late 1940s by either Kenneth Snelson or Buckminster Fuller.

Wikipedia says tensegrity is a structural principle based on the use of isolated components in compression inside a net of continuous tension, in such a way that the compressed members do not touch each other and the prestressed tensioned members delineate the system spatially. As you can see from the pictures a tensegrity structure looks like girders floating in the air, captured in a web of cables. Because of the arrangement none of the structural members experiences a bending moment.

Buckminster Fuller allegedly said that a tensegrity structure can be of any size, covering a city or encasing all of Terra. However I have not managed to find a citation yet.

I also did some speculation on using space opera tractor and pressor beams in a tensegrity structure.

Naturally a conventional structure (such as a skyscraper built of girders) tends to collapse if any of the girders break. A tensegrity structure tends to collapse if any of the girders break or if any of the cables snap.

A good low-mass way to prevent cables from failing catastrophically is to use Hoytethers (cables that are elongated Hoytubes). Strengthening a cable by increasing its diameter quickly becomes too expensive in terms of mass. A Hoytether on the other hand is a low mass network of redundant cables that fails gracefully.

A consortium of scientist are working on the SuperBall Bot Planetary Lander which is basically a tensegrity robot. The robot uses a network of cables and struts to roll over terrain, adapting to uneven ground that would trap a conventional wheeled robot.

Currently (2016) a company named Skyframe Research has received $500,000 in second-phase funding from NASA’s Innovative Advanced Concepts program to develop their tensegrity based space habitat design.


This proposal seeks to design a rotating habitat with a robotic system that constructs the structure and provides a habitat growth capability. The tensegrity technology allows minimum mass of both the habitat and the robotic system.

This proposal solves three unsolved space travel problems: a) growth, b) radiation protection, and c) gravity. Our innovative tensegrity-based evolvable habitat designs will solve three critical technical problems that NASA must address: the biological effects of microgravity on humans in long duration space flight, the long duration biological effects of ionizing radiation on human physiology in deep space (beyond the Earth’s magnetosphere) and, the need for outposts in deep space to evolve dynamically over time as mission needs grow.

Our technologies fit hand in glove with NASA's new strategy and will be a key enabler in making NASA's vision of pioneering the space frontier a reality because they are the only economically feasible approach to building habitats that can grow, spin, and manufacture in space. This NIAC Phase II effort will perform critical proof of concept studies, analysis, and ground demonstrations to prove the feasibility of Growth-Adapted Tensegrity Structures (GATS) and their benefit for NASA's evolvable proving ground approach to human exploration.

As part of this effort we will conduct mission studies showing how a version 1.0 outpost in Lunar Distance Retrograde Orbit (LDRO) made from GATS can grow and evolve while utilizing asteroid resources for radiation shielding and later integrate with an asteroid ISRU system such as the NIAC funded ApisT M architecture proposed by Sercel. We will perform mission analysis in collaboration with Sercel showing how asteroid regolith slag left over from the production of rocket propellant can be accumulated over time in LDRO and integrated as radiation shielding into the structure of the GATS based evolvable outpost thereby saving many billions of dollars in launch costs and helping to make NASA’s program of human exploration more affordable.

The critical enabling technology for our GATS technology is Tensegrity Engineering, where new design methods, new dynamic models, and new control approaches are specialized for networks of axially-loaded elements, allowing the structural mass to be minimized, while the dynamic response can be controlled with minimal energy, with repairable, growable structural methods, using tractable analytical tools that are now available.

We also capitalize on asteroid resources for radiation shielding of our habitat. This NIAC Phase II effort will perform critical proof of concept studies, analysis, and ground demonstrations to prove the feasibility of Growth-Adapted Tensegrity Structures (GATS) and their benefit for NASA's evolvable proving ground approach to human exploration.

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