A space station is basically a spacecraft with no propulsion. Which boils down to just the habitat module and the payload.

Like any other living system, the internal operations of a space station can be analyzed with Living Systems Theory, to discover sources of interesting plot complications.

Much like spacecraft, in a science fiction story a space station can become a character all by themselves. Examples include Babylon 5, Deep Space 9, Waystar from Andre Norton's Uncharted Stars, Supra-New York from Heinlein's Farmer in the Sky The Green Hills of Earth and Rocket Jockey, Nowhere Near from Jack Williamson's short story with the same name, Venus Equilateral from the series by George O. Smith, Thunderbird 5 from the Thunderbird TV show, Elysium from the movie of the same name. For an exhaustive list, look up Islands in the Sky: The Space Station Theme in Science Fiction Literature and The Other Side of the Sky: An Annotated Bibliography of Space Stations in Science Fiction, both by Gary Westfahl. The latter has 975 examples.

There are some science fiction stories about star systems that have no colonists living on the surface of planets. All colonists live in swarms of space station habitats. Examples include Downbelow Station by C. J. Cherryl, The Outcasts of Heaven's Belt by Joan Vinge, and the system of Glisten from the Traveller role playing game.

Oh, Werner von Braun had it all figured out in 1952. In six issues of Collier's magazine he laid out a plan to send men to Luna and Mars. First you build a space ferry as a surface to orbit cargo transport (which was the great-grandfather of the Space Shuttle). Then you use it to make a space station.

And it was going to be a beauty of a space station, too. Three decks, 250 feet in diameter, and a crew of fifty. Makes the ISS look like a tin can. This outpost in space was where the Lunar expedition fleet would be constructed.

It would pay for itself as well. Meteorologists could plot the path of storms and predict the weather with unprecedented accuracy. Radio and TV signals could be transmitted all over the globe. Not to mention observing the military activities of hostile nations.

In other words, it would be MacGuffinite.

Why was this marvel never constructed? Because some clown invented the printed circuit. Freed from the tyranny of fragile and short-lived vacuum tubes, technologists could make unmanned satellites for Meteorologists, radio and TV signals, and watching hostile militaries. Such satellites could be assembled and launched at a fraction the cost of a manned station. They also did not require constant resupply missions to keep the crew alive.

If we had followed von Braun's plan, we would have ended up with a fleet of space ferries, a titanic manned space station, a large lunar base, and men on Mars. Instead, we have four overly complicated space shuttles near the end of their operational life that have been retired, a four man space station due to be de-orbited and destroyed in 2016, and a few bits of space trash on the Lunar surface. And we haven't been back to Luna since 1972. So it goes.

It just occured to me...why didn't we have large scale commercialization of space already? And I had a strange answer:

The microchip and the fiber optic cable.

One of the few killer apps for space satellites was the communications satellite. But the microchip allowed multiplexing many voice streams onto a single high bandwidth signal, and the fiber optic cable made cheap long range high bandwidth communications possible.

What might have happened if the microchip and fiber optic cable weren't developed for another few decades? We might actually have needed hordes of communications satellites to keep up with global demand. That means a solid customer base for launchers, and that means mass produced launchers and/or big dumb boosters.

Without the microchip, these communications satellites suck up all sorts of juice. Thus, there's a huge incentive to develop efficient solar cells. With advanced space rated solar cells and cheaper launch technology, space based power may even be practical.

The result? Large scale industrialization of space, and sufficient economies of scale that launch costs are relatively cheap.

Isaac Kuo

Why doesn't a space station fall down? A station is in "orbit," which is a clever way to constantly fall but never hit the ground. The ground curves away just enough so that the station never strikes it.

Actually, the International Space Station is in a low enough orbit that atmospheric drag decays its orbit. Periodically, Russian resupply rockets have to boost it higher. Otherwise it would de-orbit and burn up in re-entry. Many readers of this website are too young to remember when NASA's Skylab unexpectedly fell.

Many station designs are wheel shaped, and large wheels at that. They are wheel shaped so you can spin them for artificial gravity. They are large wheels so the rotation rate can be kept low enough so the crew does not experience nausea. This is conservatively 3 RPM, though studies suggest some can acclimate themselves to tolerate up to 10 RPM. The Collier space wheel is 250 feet in diameter and spins at 3 RPM, providing about one-third gee of artificial gravity at the rim.


Many, but not all, space stations are in orbit around a planet. An orbit is a clever way to constantly fall towards a planet but never hit the ground.

There are certain preferred orbits.

An equatorial orbit is a non-inclined orbit with respect to Terra's equator (i.e., the orbit has zero inclination to the equator, 180° inclination if retrograde). Most civilian satellites use such orbits. The United States uses Cape Canaveral Air Force Station and the Kennedy Space Center to launch into equatorial orbits.

An ecliptic orbit is a non-inclined orbit with respect to the solar system ecliptic.

An inclined orbit is any orbit that does not have zero inclination to the plane or reference (usually the equator).

A polar orbit is a special inclined orbit that goes over each pole of the planet in turn, as the planet spins below (i.e., the orbit is inclined 90° to the equator). Heinlein calls it a "ball of twine" orbit since the path of the station resembles winding string around a string ball. The advantage is that the orbit will eventually pass over every part of the planet, unlike other orbits. Such an orbit is generally used for military spy satellites, weather satellites, orbital bombardment weapons, and Google Earth. The United States uses Vandenberg Air Force Base to launch into polar orbits. Google Earth uses data from the Landsat program, whose satellites are launched from Vandenberg.

When launching from Terra, say a space station resupply cargo rocket, you want to launch due East to get the free delta V boost from Terra's rotation. So one would have expected that the International Space Station (ISS) would be in a 28.5° inclined orbit, which is the orbit you get when launching due East of Kennedy Space Center (latitude 28.5° N).

But it isn't, the ISS is in a 51.6° inclined orbit. Why? So that Russian cargo rockets from Baikonur Cosmodrome can reach it. Launching into a different inclination than the space port's latitude costs rocket propellant and reduces payload.

Changing the ISS planned inclination to 51.6° was in retrospect a very good decision. When NASA stupidly cancelled the Space Shuttle program before the replacement vehicle was online, they assured everybody that the replacement would be flying by 2014 at the latest. This would make a small three-year gap in NASA's ISS transport ability. Unfortunately and predictably when 2014 arrived NASA has not even started work on deciding which of the many proposals will be used, much less bending metal and cranking out functional rockets. This leaves NASA at the mercy of the Russians for access to the ISS, but without the Russians there would be no access at all and the station would have long ago burnt up in reentry like Skylab. But I digress.

Clever readers will say but wait! Baikonur Cosmodrome is at latitude 45.6°, should not that be the inclination?. In a perfect world, yes, but there is a problem. When a spacecraft is launched from Kennedy Space Center the lower stages fall into the Atlantic Ocean. And if something goes really wrong, the entire spacecraft can abort and ditch into the ocean as well. If Baikonur Cosmodrome did the same thing, large spent lower stage boosters and/or huge flaming aborting Russian spacecraft would crash into Mainland China, and the political situation would rapidly deteriorate. To avoid that unhappy state of affairs, Russian spacecraft launched from Baikonur go at a 51.6° inclination, so falling rocket bits will miss China.

The Russians already have an annoying problem with the lack of warm-water ports for seagoing vessels. They really dislike having much the same problem with respect to space launches. Therefore they are in negotiations for launch privileges at the ESA's Guiana Space Centre, which is optimally located quite near the Equator and to the West of the Atlantic Ocean.

Orbits around Terra (geocentric) are sometimes classified by altitude above Terra's surface:

  • Low Earth Orbit (LEO): 160 kilometers to 2,000 kilometers. At 160 km one revolution takes about 90 minutes and circular orbital speed is 8 km/s. Affected by inner Van Allen radiation belt.
  • Medium Earth Orbit (MEO): 2,000 kilometers to 35,786 kilometers. Also known as "intermediate circular orbit." Commonly used by satellites that are for navigation (such as Global Positioning System aka GPS), communication, and geodetic/space environment science. The most common altitude is 20,200 km which gives an orbital period of 12 hours.
  • Geosynchronous Orbit (GEO): exactly 35,786 kilometers from surface of Terra (42,164 km from center of Terra). One revolution takes one sidereal day, coinciding with the rotational period of Terra. Circular orbital speed is about 3 km/s. It is jam-packed with communication satellites like sardines in a can. This orbit is affected by the outer Van Allen radiation belt.
  • High Earth Orbit (HEO): anything with an apogee higher than 35,786 kilometers. If the perigee is less than 2,000 km it is called a "highly elliptical orbit."
  • Lunar Orbit: Luna's orbit around Terra has a pericenter of 363,300 kilometers and a apocenter of 405,500 kilometers.

Geosynchronous Orbits (aka "Clarke orbits", named after Sir Arthur C. Clarke) are desirable orbits for communication and spy satellites because they return to the same position over the planet after a period of one sidereal day (for Terra that is about four minutes short of one ordinary day).

A Geostationary Orbit is a special kind of geosynchronous orbit that is even more desirable for such satellites. In those orbits, the satellite always stays put over one spot on Terra like it was atop a 35,786 kilometer pole. For complicated reasons all geostationary orbits have to be over the equator of the planet. In theory only three communication satellites in geostationary orbit and separated by 120° can provide coverage over all of Terra.

All telecommunication companies want their satellites in geostationary orbit, but there are a limited number of "slots" available do to radio frequency interference. Things get ugly when you have, for instance, two nations at the same longitude but at different latitudes: both want the same slot. the International Telecommunication Union does its best to fairly divide up the slots.

The collection of artificial satellites in geostationary orbit is called the Clarke Belt.

Note that geostationary communication satellites are marvelous for talking to positions on Terra at latitude zero (equator) to latitude plus or minus 70°. For latitudes from ±70° to ±90° (north and south pole) you will need a communication satellite in a polar orbit, a highly elliptical orbit , or a statite. Russia uses highly eccentric orbits since those latitudes more or less define Russia. Russian communication satellites commonly use Molniya orbits and Tundra orbits.

About 300 kilometers above geosynchronous orbit is the "graveyard orbit" (aka "disposal orbit" and "junk orbit"). This is where geosynchronous satellites are moved at the end of their operational life, in order to free up a slot. It would take about 1,500 m/s of delta V to de-orbit an old satellite, but only 11 m/s to move it into graveyard orbit. Most satellites have nowhere near enough propellant to deorbit.

"Okay, T.K., look at it this way. Those three hundred people in LEO Base can get back to Earth in less than an hour if necessary; we'll have lifeboats, so to speak, in case of an emergency. But out there at GEO Base, it's a long way home. Takes eight hours or more just to get back to LEO, where you have to transfer from the deep-space passenger ship to a StarPacket that can enter the atmosphere and land. It takes maybe as long as a day to get back to Earth from GEO Base— and there's a lot of stress involved in the trip."

Hocksmith paused, and seeing no response from the doctor, added gently, "We can get by with a simple first-aid dispensary at LEO Base, T.K., but not at GEO Base. I'm required by my license from the Department of Energy as well as by the regulations of the Industrial Safety and Health Administration, ISHA, to set up a hospital at GEO Base."

He finished off his drink and set the glass down. "If building this powersat and the system of powersats that follow is the biggest engineering job of this century, T.K., then the GEO Base hospital's going to be the biggest medical challenge of our time. It'll be in weightlessness; it'll have to handle construction accidents of an entirely new type; it'll have to handle emergencies resulting from a totally alien environment; it'll require the development of a totally new area of medicine— true space medicine. The job requires a doctor who's worked with people in isolated places—like the Southwest or aboard a tramp steamer. It's the sort of medicine you've specialized in. In short, T.K., you're the only man I know who could do the job . . . and I need you."

Stan and Fred discovered that it took almost nineteen minutes just to get to Charlie Victor, Mod Four Seven. There were a lot of hatches to go through and a lot of modules to traverse. "Fred, if we don't find some faster way to move around this rabbit warren, a lot of people are going to be dead before we reach them," Stan pointed out, finally opening the hatch to Mod Four Seven.

Fred was right behind him through the hatch. "I'll ask Doc to see Pratt about getting us an Eff-Mu."

"What's that?"

"Extra Facility Maneuvering Unit. A scooter to anybody but these acronym-happy engineers."

Transporting was easy in zero-g, but getting through all the hatches while continuing to monitor his condition and maintain the positive-displacement IVs was difficult. It required almost a half hour to bring the man back to the med module.

From Space Doctor by Lee Correy (G. Harry Stine) 1981

Lagrangian points are special points were a space station can sit in a sort-of orbit. Lagrange point 1, 2, and 3 are sort of worthless, since objects there are only in a semi-stable position. The ones you always hear about are L4 and L5, because they have been popularized as the ideal spots to locate giant space colonies. Especially since the plan was to construct such colonies from Lunar materials to save on boost delta V costs. The important thing to remember is that the distance between L4 — Terra, L4 — Luna, and Terra — Luna are all the same (about 384,400 kilometers). Meaning it will take just as long to travel from Terra to L4 as to travel from Terra to Luna.

For a more exhaustive list of possible Terran orbits refer to NASA.

It is also possible for a satellite to stay in a place where gravity will not allow it. All it needs is to be under thrust. Which is rather expensive in terms of propellant. Dr. Robert L. Forward noted that solar sails use no propellant, so they can hold a satellite in place forever (or at least as long as the sun shines and the sail is undamaged). This is called a Statite.

If the planet has an atmosphere and the station orbits too low, it will gradually slow down due to atmospheric drag. "Gradually" up to a point, past the tipping point it will rapidly start slowing down, then burn up in re-entry. Some fragments might survive to hit the ground.

The "safe" altitude varies, depending upon the solar sunspot cycle. When the solar activity is high, the Earth's atmosphere expands, so what was a safe altitude is suddenly not so safe anymore.

NASA found this out the hard way with the Skylab mission. In 1974 it was parked at an altitude of 433 km pericenter by 455 km apocenter. This should have been high enough to be safe until the early 1980's. Unfortunately "should" meant "according to the estimates of the 11-year sunspot cycle that began in 1976". Alas, the solar activity turned out to be greater than usual, so Skylab made an uncontrolled reentry in July 1979. NASA had plans to upgrade and expand Skylab, but those plans died in a smoking crater in Western Australia. And a NOAA scientist gave NASA a savage I Told You So.

The International Space Station (ISS) orbited at an even lower at 330 km by 410 km during the Space Shuttle era, but the orbit was carefully monitored and given a reboost with each Shuttle resupply mission. The low orbit was due to the Shuttle carrying up massive components to the station.

After the Shuttle was retired and no more massive components were scheduled to be delivered, the ISS was given a big boost into a much higher 381 km by 384 km orbit. This means the resupply rockets can carry less station reboost propellant and more cargo payload.

If the planet the station orbits has a magnetic field, it probably has a radiation belt. Needless to say this is a very bad place to have your orbit located, unless you don't mind little things like a radiation dosage of 25 Severts per year. And that is for Terra, Jupiter's radiation belts are a thousand times worse. In 1973 Pioneer 11 was surprised by radiation levels around Jupiter ten times greater than NASA had predicted. This is why Pioneer did not send back photos of the moon Io since the radiation belt had fried its imaging photo polarimeter. Work on the Voyager space probe came to a screeching halt as they frantically redesigned it to cope with the radiation, but still be assembled in time for the launch window.

Terra's zone of glowing blue death is called the Van Allen radiation belts.

The Inner Belt starts at an altitude from 400 km to 1,200 km, depending on latitude, and ends at an altitude of about 6,000 km, with its most lethal area 3,500 km out. The South Atlantic Anomaly can potentially disrupt satellites in polar orbits, but usually does not pose a problem for manned spaceflights. Except for the ISS. The radiation is high-energy protons (400 MeV).

The Outer Belt ranges from 13,000 km to 60,000 km, with its most lethal area 27,000 km out. The Outer Belt is affected by solar winds, and is thus flattened to 59,500 km in the area directly between the Earth and the Sun, and extends to its maximum distance in the shadow of the Earth. The radiation is high-energy electrons (7 MeV).

A safe channel exists between the belts from 9,000 km to 11,000 km.

The Apollo missions had trajectories designed to shoot through the belts at high speed to minimize radiation exposure.

Since Terra's rotational and magnetic axes do not intersect at Terra's Center, there is a deadly spot in the inner belt called the South Atlantic Anomaly. The inner edge of the belt proper is usually 1,000 kilometers from Terra's surface, but the anomaly gets as close as 200 kilometers. Satellites and space stations need extra radiation shielding for when they periodically pass through the anomaly. The ISS has extra shielding for that reason. Astronauts have seen phosphene shooting lights in their eyeballs, laptops have crashed, control computers experience transient problems as they pass through the anomaly.

Since the Van Allen Belts will destroy expensive satellites as well, there have been proposals to drain the radiation out of the belt.

Station Station 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 either brought along or are 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 hydralic 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)
Birth of Fire

(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)
Leviathan Wakes
     "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 habitat. The person figures there are opportunities on the habitat, 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 habitat 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.

The term was invented by J. Michael Straczynski for his TV series Babylon 5, more accurately he adapted the 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.

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.

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

Three Generation Rule

Not generally recognized is the matter of Ken Burnside's Three-Generation Rule for space habitats (space stations where people live and raise new generations of children). As Rick Robinson puts it:

Basic 3 Generation Rule

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

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.

(Under) 1 Generation Rule

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)
Refuting the 3 Generation Rule

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 von Fraumench

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

William Black

     Lilith von Fraumench, 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)
Rapid turnover in space habs

(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
Thirty years of deferred maintenance

(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)
Three-Generations Rule

     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.

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.


Station Functions

In his incredibly useful sourcebook for designing science fiction universes Star Hero, James Cambias lists some common uses for space stations:

Food-producing station
Forward base to support spacecraft. Sometimes called "staging base" if military. Generally located in a "remote" location, remote being defined as "a long distance from the home base of the supported spacecraft." (e.g., a military base can be "remote" even if it is near a huge metropolitan planet belonging to a hostile nation).
Orbital Shipyard. Closely related is Spacedock, an outer space version of drydock where spacecraft are repaired or refitted.
Space Superiority Platform
Armed military station keeping an eye on the planet it is orbiting. If a planet is balkanized, the station will watch military ground units belonging to hostile nations. If the planet is a conquered one, or the government is oppressing the inhabitants, the station will try to maintain government control and deal with revolts. In any case, read about planetary attack
Planetary Defense
Armed military station defending its planet from outside attack, orbital fortress. Note that an orbital fortress will be more heavily armed than a warship of the same mass since the fortress design can allocate the mass budget for propulsion in favor of more weapons. These will be in a close orbit to the planet they are defending.
Orbital propellant depot. Fuel refining and storage facility
Residential colony
Orbital factory or smelting plant. They can be near asteroid clusters with rich mineral deposits, or be for industries that would otherwise pollute an inhabitable planet.
Weather-monitoring station
Station monitoring the planet below. News media, military spy satellite, tracking global ocean and air traffic, remote listening post, etc.
Large solar power satellite, beaming energy to clients via microwaves
Medical isolation station, research into technologies too dangerous to experiment with on an inhabited planet (medical disease research, nanotechnology, biowarfare agents, etc.), customs quarantine stations for infected incoming passengers.
Scientific research. This can be for research that requires microgravity, or the station can be located near an interesting planet or astronomical phenomenon.
Orbital spaceport. There are more details about spaceports here

To which I would add:

Aldrin Cyclers
Cyclers are special stations in Hohmann orbits between pairs of planets. They are used as very cheap but very slow methods of interplanetary transport.
A "gold" strike in an asteroid belt or the establishment of a military base in a remote location may create a "boomtown". The sudden appearance of large numbers of asteroid miners or enlisted people is an economic opportunity to sell them whiskey, adult entertainment, and other hard to find luxuries at inflated prices. Not to mention supplies and tools. Remember, in the California Gold Rush of 1849, it was not the miners who grew rich, instead it was the merchants who sold supplies to the miners. Civilian entrepreneurs may find it expedient to connect their ramshackle spacecraft together to make impromptu space stations. For an amusing look at the development and economy of a boomtown watch the movie Paint Your Wagon. But remember that boomtowns can become ghost towns quite rapidly, if mineral strike dries up or the military base is closed.
Can be general hospitals, hospitals specializing in treating victims of spacecraft disasters, and geriatric hospitals using microgravity to prolong the lives of the elderly. They will also have medical officers examining the crew and passengers of incoming spacecraft. If any are infected with dangerous diseases, they must be quarantined.
Ghost Town
A ghost town is the abandoned skeletal remains of a space station that was formerly a boomtown.
Short or long term living quarters for people. Generally includes restaurants of various quality.
A sort of combination of Space Superiority Platform and Planetary Defense. The idea is that the station is to prevent anything from entering or leaving the planet it is orbiting. A planet might be invested, meaning that the planet is under siege from whoever owns the space station. The station does not want planetary inhabitants escaping, nor does it want blockade runners entering. A planet might be interdicted because they contain something very dangerous (Xenomorphs, thionite, the City on the Edge of Forever, replicators, or 100% lethal plagues). Or the planet might be interdicted because it has something very valuable and the station owner does not want poachers sneaking in and stealing any.
Macrolife is sort of a cross between a huge habitat and a generation star ship. These are traditionally hollowed-out asteroids.
Pirate Haven
Space pirates need infrastructure (fences for pirated loot, fuel and reaction mass, ship repairs, R&R for the crew). A hidden space station can act as a Pirate Haven and cater to these needs.
Ship Docks
Short or long term storage of spacecraft.
Sky Watch
Monitors the entire sky from their location, keeping track of trajectories of known spacecraft and spotting the appearance of unauthorized spacecraft. And other important events, such as unexpected nuclear explosions. Space traffic controllers want to know trajectories of spacecraft. Orbit Guard wants to know about alterations in asteroid orbit both authorized and unauthorized. Military wants to know about enemy battle fleets. Merchant princes want to know about hostile privateers and space pirates. There will be several such stations located in widely separated parts of the solar system, for determining distance by triangulation and to make it harder for spacecraft to hide behind objects.
Space Traffic Controllers
Outer space equivalent of terrestrial air traffic controllers. Monitors and controls the flight plans of local spacecraft. Generally only needed in "crowded" areas,such as the orbital space around inhabited planets.
Space Tug Services
Groups of space tugs for hire, to move spacecraft, cargo, or other massive objects.
Spacecraft Certification

As the traffic around a given planet or space station grows and as the energy contained in spacecraft fuel becomes more dangerous, at some point the authorities are not going to allow the presence of broken-down junker spaceships with sub-standard antimatter containment tanks. Not around our planet you ain't, Captain Han Solo.

The Spacecraft Inspectors will give all spacecraft a periodic once-over, to keep the spacecraft's certification current.

Tax Haven / Data Haven
These are tax shelters used by the wealthy and by corporations. They typically orbit a the planet a corporation is based on, just beyond territorial limits. More details here.
Crew Hiring
Employment services where spacecraft captains can hire crewmembers.
Transport Nexus
A Transport Nexus is a crossroad spaceport for passengers, a port of entry, an orbital warehouses where valuable minerals from asteroid mines are stored and trade goods transshipped, or a "trade-town". Will include related services, such as hotels and stevedore/longshoremen.

Naturally a given space station could have several functions.

Mr. Cambias goes on to note that stations can occupy a variety of orbits. Low planetary orbit just above the planet's atmosphere. High planetary orbit at thousands of kilometers. Geosynchronous / Geostationary planetary orbit at an altitude where the orbital period equals one planetary day (useful for communication, observation, powersat, and meteorology). Stellar orbit where the station orbits the local star instead of orbiting a planet. And Trojan orbits where the station occupies a Lagrange point (beloved of L5 colonies)

The size of a station has many terms, none of which are defined. In arbitrary order of size the terms include Beacon (like an interstellar lighthouse), Outpost, Station, Base, and Colony.


Circum-Terra was a great confused mass in the sky. It had been built, rebuilt, added to, and modified over the course of years for a dozen different purposes—weather observation station, astronomical observatory, meteor count station, television relay, guided missile control station, high-vacuum strain-free physics laboratory, strain-free germ-free biological experiment station, and many other uses.

But most importantly it was a freight and passenger transfer station in space, the place where short-range winged rockets from Earth met the space liners that plied between the planets. For this purpose it had fueling tanks, machine shops, repair cages that could receive the largest liners and the smallest rockets, and a spinning, pressurized drum—"Goddard Hotel"—which provided artificial gravity and Earth atmosphere for passengers and for the permanent staff of Circum-Terra.

Goddard Hotel stuck out from the side of Circum-Terra like a cartwheel from a pile of junk. The hub on which it turned ran through its center and protruded out into space. It was to this hub that a ship would couple its passenger tube when discharging or loading humans. That done, the ship would then be warped over to a cargo port in the non-spinning major body of the station. When the Glory Road made contact, there were three other ships in at Circum-Terra, the Valkyrie in which Don Harvey had passage for Mars, the Nautilus, just in from Venus and in which Sir Isaac expected to return home, and the Spring Tide, the Luna shuttle which alternated with its sister the Neap Tide.

The two liners and the moon ship were already tied up to the main body of the station; the Glory Road warped in at the hub of the hotel and immediately began to discharge passengers. Don waited his turn and then pulled himself along by handholds, dragging his bags behind him, and soon found himself inside the hotel, but still in weightless free fall in the cylindrical hub of the Goddard.

From Between Planets by Robert Heinlein (1951)
The Sands of Mars

The Inner Station—, “Space Station One” as it was usually called—, was just over two thousand kilometres from Earth, circling the planet every two hours. It had been Man’s first stepping-stone to the stars, and though it was no longer technically necessary for spaceflight, its presence had a profound effect on the economics of interplanetary travel. All journeys to the Moon or the planets started from here; the unwieldy atomic ships floated alongside this outpost of Earth while the cargoes from the parent world were loaded into their holds.

A ferry service of chemically fuelled rockets linked the station to the planet beneath, for by law no atomic drive unit was allowed to operate within a thousand kilometres of the Earth’s surface. Even this safety margin was felt by many to be inadequate, for the radioactive blast of a nuclear propulsion unit could cover that distance in less than a minute.

(ed note: this implies an exhaust velocity of about 16,000 meters per second. This could be done by a liquid or gas core nuclear thermal rocket with molecular hydrogen propellant, or a solid-core nuclear thermal rocket using atomic hydrogen as propellant.)

Space Station One had grown with the passing years, by a process of accretion, until its original designers would never have recognised it. Around the central spherical core had accumulated observatories, communications labs with fantastic aerial systems, and mazes of scientific equipment which only a specialist could identify. But despite all these additions, the main function of the artificial moon was still that of refuelling the little ships with which Man was challenging the immense loneliness of the Solar System.

From The Sands of Mars by Sir Arthur C. Clarke (1951)
Hive of scum and villainy

Approach space stations from the bottom up, however, in a Firefly or cyberpunk manner, and you'll get a very different view of them — shady orbital stations where you can get just about anything you want... for a price. It's the perfect nexus for organized crime, given a station's importance to inter-planetary commerce and transport. Plus, in a setting with a Balkanized earth, there will likely be no serious push to police the space station in the first place unless it's run by one country alone, and in that case, I wouldn't be surprised if that country extorts anyone else who uses their spaceport.

If you want to expand on the Western analogies that are found so often in SF, then the station would be a railhead like the sort cattle-drivers used to send their cows to, with the associated markets of extortion and dens of ill-repute that go hand-in-hand with such a locale.

Ferrard Carson in a comment
Hive of scum and villainy 2

The tunnel outside was white where it wasn't grimy. Ten meters wide, and gently sloping up in both directions. The white LED lights didn't pretend to mimic sunlight. About half a kilometer down, someone had rammed into the wall so hard the native rock showed through, and it still hadn't been repaired. Maybe it wouldn't be. This was the deep dig, way up near the center of spin. Tourists never came here.

Havelock led the way to their cart, bouncing too high with every step. He didn't come up to the low gravity levels very often, and it made him awkward. Miller had lived on Ceres his whole life, and truth to tell, the Coriolis effect up this high could make him a little unsteady sometimes too.

Ceres, the port city of the Belt and the outer planets, boasted two hundred fifty kilometers in diameter, tens of thousands of kilometers of tunnels in layer on layer on layer. Spinning it up to 0.3 g had taken the best minds at Tycho Manufacturing half a generation, and they were still pretty smug about it. Now Ceres had more than six million permanent residents, and as many as a thousand ships docking in any given day meant upping the population to as high as seven million.

Platinum, iron, and titanium from the Belt. Water from Saturn, vegetables and beef from the big mirror-fed greenhouses on Ganymede and Europa, organics from Earth and Mars. Power cells from lo, Helium-3 from the refineries on Rhea and lapetus. A river of wealth and power unrivaled in human history came through Ceres. Where there was commerce on that level, there was also crime. Where there was crime, there were security forces to keep it in check.

Eros supported a population of one and a half million, a little more than Ceres had in visitors at any given time. Roughly the shape of a potato, it had been much more difficult to spin up, and its surface velocity was considerably higher than Ceres' for the same internal g. The old shipyards protruded from the asteroid, great spiderwebs of steel and carbon mesh studded with warning lights and sensor arrays to wave off any ships that might come in too tight. The internal caverns of Eros had been the birthplace of the Belt. From raw ore to smelting furnace to annealing platform and then into the spines of water haulers and gas harvesters and prospecting ships. Eros had been a port of call in the first generation of humanity's expansion. From there, the sun itself was only a bright star among billions.
The economics of the Belt had moved on. Ceres Station had spun up with newer docks, more industrial backing, more people. The commerce of shipping moved to Ceres, while Eros remained a center of ship manufacture and repair. The results were as predictable as physics. On Ceres, a longer time in dock meant lost money, and the berth fee structure reflected that. On Eros, a ship might wait for weeks or months without impeding the flow of traffic. If a crew wanted a place to relax, to stretch, to get away from one another for a while, Eros was the port of call. And with the lower docking fees, Eros Station found other ways to soak money from its visitors: Casinos. Brothels. Shooting galleries. Vice in all its commercial forms found a home in Eros, its local economy blooming like a fungus fed by the desires of Belters.

The architecture of Eros had changed since its birth. Where once it had been like Ceres—webworked tunnels leading along the path of widest connection—Eros had learned from the flow of money: All paths led to the casino level. If you wanted to go anywhere, you passed through the wide whale belly of lights and displays. Poker, blackjack, roulette, tall fish tanks filled with prize trout to be caught and gutted, mechanical slots, electronic slots, cricket races, craps, rigged tests of skill. Flashing lights, dancing neon clowns, and video screen advertisements blasted the eyes. Loud artificial laughter and merry whistles and bells assured you that you were having the time of your life. All while the smell of thousands of people packed into too small a space competed with the scent of heavily spiced vat-grown meat being hawked from carts rolling down the corridor. Greed and casino design had turned Eros into an architectural cattle run.

From Leviathan Wakes by "James S.A. Corey" (Daniel Abraham and Ty Franck) 2011. First novel of The Expanse
Station cultures

Various sorts of space stations can exist, with different parameters leading to different societies.

High throughput ports (like the ones at the ends of Skyhook orbital elevators) will have lots of facilities for the "sailors" and "longshoremen" (they may be facilities for semi-automated or teleoperated systems), as well as maintained crews and port officials. Lots of money and valuable change hands, so corruption and crime may be rampant.

A naval support base built on a NEO will be a totally different environment; the crew and contractors will be operating under a code of service discipline, but dealing with boredom and an irregular work load.

Most asteroids will probably have very limited transportation facilities (a cycler might be by once a decade or so), unless they strike it rich, in which case they might end up like Dubai, with lots of money to import luxury goods. Otherwise, the transport is one way outbound as ices and minerals flow down the mass driver.

Given the low population density and the difficulty of surviving in hostile alien environments, most places will be like an apartment block, with everyone and everything sealed inside for protection and shelter. Expansion will probably be by driving tunnels to resource or energy nexus points and building another apartment block there, so most story settings will be quite urbanized, at least until large open Island 3 type colonies can be economically built.

Top down= navy bases and scientific research facilities. These are built for a specific purpose, and generally have little economic rational behind them, although military bases may develop garrison towns and eventually grow into larger settlements (especially when the military rational passes). If the military reason for the base fades away without any compelling economic rational to replace it, it is usually abandoned (think of Hadrian's Wall, the Maginot line or old ICBM silos).

Bottom up= trading ports, crossroads, tollgates and locks, marketplaces. They start small but their economic usefulness attracts more people and more activity, in a positive feedback loop leading to towns and cities.

There is also devolution, the port cities of the Hanse are no longer economic powerhouses, and I can see Luna going the way of Detroit after it becomes more economical to harvest 3He from the atmosphere of gas giants (the Pearson elevator to L1 is a minor tourist attraction, and L2 is a brownfield of abandoned mass catchers in parking orbits. Only criminal gangs and Libertarian squatters make their homes in and around Luna).

Of course lots of compound scenarios can exist as well; an occupying power builds a fort overlooking a captured port, or the squatters become the nexus for urban renewal because they (insert "x" here)...

Thucydides in a comment

Mr. Blue:

Some station societies would form in a very organic fashion.

Let's say there's a big rush to mine (X) in the asteroid belt and a lot of independent prospectors head out to strike it rich.

Bill figures he can make a fortune selling space suits, mining tools and the like, so he loads up a freighter and sets up shop. Sally also had the idea of setting up a hydroponic farm/ yeast vat/ and restaurant, and also headed that way. As it's a pain for a miner to make two different stops, Bill and Sally decide to dock their freighters (man, there is no way to say that without sounding dirty) and maybe even set up an extra hab for a hotel...

Pretty soon, as word gets round, other enterprising individuals begin to connect. Bits and pieces are added- an empty fuel tanker as a bar, a repair yard, or even an official buyer for (X)- sure, he doesn't pay as much, but it's a lot better that flying it to Mars yourself. And other services begin to set up shop.

Then, Billstown becomes an interplanetary destination in it's own right. After all, where else on the 'Belt can one get their ship fixed, pick up some spare hands, have a good meal and a drink, and, um, visit the Seamstresses (hem hem).

Of course, once the mining runs out (or whatever else), the boomtown becomes a ghost town. Any spaceworthy ships will be flown off, everything else may be left behind, or salvaged.

But, if the location is good enough, this random jumble of habs, freighters, and other items can become something better...

(ed note: in Terry Pratchett's marvelous Diskworld series of satirical fantasy novels, the "Seamstresses" was an euphemism for the local brothel)

From comments to Transport Nexus
Odin's Outpost

Ms. Thomas leaned over to look around the end of her console in Mr. Pall's direction. She cast me a look and gave her head a little shake, before refocusing her attention on the plot. After a few ticks of fiddling, she grunted. "Hmmph. I really hate to say this, Captain, but it looks like someplace that might be called High Tortuga."
I got out of the chair and went to look over her shoulder. It looked like a collection of ships, cans, and assorted other metal arranged in a haphazard pattern. As we watched, one small blip split out from the mass and began accelerating away.
"Any idea what that is, Ms. Thomas?"
"Yes, Captain. I believe that's Odin's Outpost. It's grown a bit since I saw it last."
I leaned in to look at the display. At our range there wasn't a lot of resolution but it was enough to see what looked a lot like a freight marshaling yard when viewed from a hundred-thousand kilometers out. "What pray tell is an Odin's Outpost, Ms. Thomas?"
"It's kind of a way station, Skipper. It's not really much of anything. Officially, it's not there. It's been so long since I jumped out here, I'd practically forgotten it. We skimmed by it on some of the doubles we did back on the Hector. We got close enough to give it a good scan on short range, but I've never been close enough to get a direct look."
"Looks like a collection of cans and some small ships, Ms. Thomas."
"I think there's a ship at the heart of it, Captain. The story on the Hector was that this guy, Odin, jumped in and his burleson drives went out on him. He couldn't jump back. He flew around out here for awhile and the next ship through rendered assistance, so he was able to get out eventually. The story goes that when it was over, he took it into his head to come back out and set up this way station. Started as a shipload of food, fuel, and spare parts." She nodded at the screen. "It's more now."
"He just sits out here in the Deep Dark, Ms. Thomas?"
She shrugged. "It appears so. Skipper, but he's really near the crossroads between the Breakall-to-Dree run and the course from Welliver-to-Jett. Those four systems are almost on the same plane so if you've jumped clean, you'll go through this relatively small volume of space no matter which direction or which pair you're jumping to."

"Having the only bar in a billion klicks must be handy for Odin," I said.
She snickered. "Yes, sar. That it is. He's been out here something like thirty stanyers. Nobody's quite sure how he's making a go of it, but apparently enough ships come through that need spare parts or forgot the toothpaste to make it worth his while."
"Blackmarket, Ms. Thomas?"
"I don't know. Captain. With plenty of time, the right incentives, and a twisted mind, anything is possible."

We saw two in the short time it took to slide past Odin's Outpost, not including the smaller craft that seemed to be coming and going from the Outpost itself.
"What do you suppose they're doing, Mr. Hill?"
"Mr. Pall thinks they're pirates, Skipper."
"What do you think, Mr. Hill?"
"They look like fast packets. Skipper. I'd bet on casino junkets."
"Why casinos, Mr. Hill? Gambling's legal in all of the systems around here."
"Yes, Skipper but not in Grail or Fischer. Those are both in range of a fast packet."
"Yes, but why jump way out here?"
He shrugged. "Exotic destination for people with disposable income. I bet there's a lot of people who are in it for the adventure. They run these junkets on the quiet, even out of Diurnia. And I'd bet he has a pleasure dome in there, too, fully stocked with hot and cold running pleasures. All untaxed and unregulated by the Confederated Planets Joint Committee on Everything."
"And plenty of room to dispose of the bodies, eh, Mr. Hill?"
"Can't be too many or the authorities would begin to notice, but who's to say. Skipper."
"The ultimate free port, eh, Mr. Hill?"
"So it would seem, Captain, but free is a matter of opinion."
"Interesting observation, Mr. Hill."
He shrugged. "Some see fences as keeping dangers out. Other see the same fences keeping them in."

Space Traffic Controllers

"Da. Engagement zones are expanded," Omer explains "United States, Europa, Bahia, all announce new requiremen five days ago.

"Sounds like transition-to-war conditions."

"Maybe. Commonwealth ships have had some problems. Some body soon maybe make a 'mistake' with a Commonwealth ship” Omer pointed out. "Or we get clearance that is wrong and take us into engagement zone. So I got from Kevin Graham new data showing positions of all orbiting objects and load into computer I will make sure clearance and trajectory do not lead us into danger."

Twenty minutes before noon, clearance came over the up-link Omer checked it and gave me a thumbs-up. I accepted it. We made a straightforward departure with the catapult slinging the Tomahok into the air at a one-gee goose. I climbed out according to flight plan and watched while the air-breathers transitioned I scram-jet mode and finally lipped-over when the mains ignited at 60 kilometers. I wasn't particularly looking for anything happen at that point because we were still in international space over the Indian Ocean.

The Tomahok was handed-off from Madras Center to Orient Center as we ascended through a hundred kilometers, expected something to happen then. It did.

"Tomahok, this is LEO Orient Center. Amended clearance."

It came on the up-link. Omer shook his head. "Bojemoi!" exploded. "Reject it!"

"LEO Orient Center, this is Tomahok. Negative the amended clearance, sir."

"Tomahok, what's your reason for refusal?"

"What's your reason for issuing this amended clearance, sir?"

"AmSpace Command request through LEO Canambah Center."

"The amended clearance takes us into the engagement zone of Gran Bahia estacao baixo doze."

"Tomahok, stand by. ... Tomahok, amended clearance: De-orbit for Woomera landing. We can't get you through."

I knew what to do, and I let it all hang out. "LEO Orient Center, Tomahok. Negative the amended clearance. We are initiating no-clearance flight under I-A-R Regulation ninety-one- point-eight. We'll take her up to Ell-Five as filed under our responsibility to detect and avoid."

Omer reached over and clapped me on the right shoulder.

There must have been consternation in LEO Orient Center because it took several seconds for the traffic coordinator to acknowledge. "Uh, Tomahok, Center, roger! Service is terminated. Proceed on your own responsibility. Retain your current beacon code."

I acknowledged and told Omer, "Get ready to thread the needle, Russkie! Let's see if we're good enough to make Ell-Five before somebody burns us with a hell-beamer!"

There I was, flat on my back at 30,000 meters, nothing between me and the ground but a thin regulation.

I'd invoked a seldom-used International Aerospace Regulation that harked back to Earth's oceans where a ship captain was an absolute monarch responsible for himself, his ship, and everything in it. It had been carried into the air by a rule that made the; "pilot-in-command" solely responsible for the safety and operation of his aircraft and everything in it, regardless of what traffic coordinators on the ground told him.

In effect, I'd told the space traffic people I'd fly without their help. Avoiding an engagement zone isn't difficult if you know where it is. Space is mostly empty.

The various STC Centers would continue tracking our beacon to keep other spacecraft clear of us. Military trackers would do the same in case we broached their engagement zones, which would mean trouble for the Tomahok.

I'd waived clearance while still under ascent thrust on our original trajectory to a 200-kilometer parking orbit. Our delta-vee margin was excellent

"Russkie, I hope the League data's good," I told Omer. "Display our current flight path and the projected positions and engagement zones of other sky junk."

"Blinking blips aren't in League data," Omer reported. The Kazakh became laconic when he was under pressure, probably because he was thinking in Russian and mentally translating into aerospace English with adrenalin pumping.

I studied the display. A blinking blip indicated a polar orbiting satellite. In parking orbit, we'd broach its engagement zone.

"There's our problem," I pointed out. "AmSpace Command recon bird. That's why the amended clearance. We'll burn out of parking orbit to miss him. What are the options?"

Omer punched the keypad. A series of trajectories came on the display. "Take high delta-vee option. It will be obvious we're avoiding the reconsat."

"But we may run into trouble with this one, Omer," I said, indicating another target with my finger. "It's displaying no code. What is it?"

Omer queried the computer. "Not in League data. Unknown."

"It's got to be registered! I'll query Center for identification."

"Let it be for now. We handle when time comes," the Mad Russian Space Jockey suggested. "We take problems one at a time. Sandy, get us in parking orbit and watch engagement zones. I work on vector for transfer orbit to Ell-Five."

Our burn out of parking orbit came as re-programmed. While, we were under thrust, we got a sensor alarm. "Targeting lidar!" I snapped. "Aerospace Force has seen us closing on the reconsat,"

"We go laser-hard," Omer said, reaching for the switch.

"Negative!" I snapped. "They'll see it, interpret it as a countermeasure, and try to burn us." I indicated another target on the display. "That's annotated as an unspecified military satellite; it's a ten megawatt hell-beamer."

"Hokay, so we do a little tsig-tsag! Give me controls!"

I did and continued to check displayed targets. Omer called out his actions. “Tsang plus-x ten meters per sec."

I got a surface temperature warning signal. "Warning shot without a call. That's not SOP!" The Aerospace Force tapped the data stream from the world STC net and they knew we were the unarmed Tomahok out of Vamori-Free.

"Maybe you got wrong freq. We did not broach engagement zone of reconsat, and now they see us burn into new trajectory. So we are out of hard place under rock for now. You fly now."

Low earth orbit zone is tricky to work in. Velocities and closing rates are high. There isn't much time to detect, track, make decisions, and maneuver. It's full of sensitive earth-oriented reconsats that are automated and passive. They can't defend themselves or maneuver. Even though such unmanned skyapies are considered to be expendable scouts, my former colleagues were sensitive about them. Everyone knew where everyone else's were, and nobody bothered them for fear of retaliation. Fortunately, sensitive satellites advertised themselves with "no trespassing" signals.

Hell-beamers were another matter. They were unmanned with auto defenses. Unless they spotted the proper beacon password— which we didn't have—they'd shoot at anything that broached their engagement zones. We had to stay clear of those. We'd been lucky once.

Some that looked like hell-beamers weren't; they were decoys or legitimate R&D space telescopes. The sensor signatures were the same. If you wanted to find out if one was indeed a hell-beamer, you had to make a hands-on inspection which was very risky not only because of the auto-defenses but also because some of them were booby-trapped.

Nobody liked the hell-beamers, especially the League of Free Traders. But the low-powered ones in LEO were no threat to people on the ground. And nobody had been burned in space by them, so they were tolerated as a necessary evil.

Think of Earth as being at the bottom of a funnel-shaped well whose walls become less steep as you climb away from Earth.

Paint the walls of the funnel in zones of different colors to represent the various space traffic control center jurisdictions. The ones nearest Earth at the bottom of the funnel are controlled from national centers that are, you hope, in communication with one another and swapping data. The ones further out are watched by seven other centers located in GEO. And the ones in the nearly-flat upper part of the funnel are four in number centered on L-4, the Moon, L-5, and a huge "uncontrolled sector" stretching around lunar orbit from 30-degrees ahead of L-4 to 30-degrees behind L-5 where there wasn't anything then.

Now spin the funnel so the bottom part representing a distance up to 50,000 kilometers goes around once in 24 hours. Spin the top part from 50,000 kilometers altitude out to a half-million kilometers at the lunar rate of 29.5 days.

Located on the walls of this madly turning multi-colored funnel are marbles spinning around its surface fast enough so they don't fall down the funnel. Some of them are deadly marbles; come close and you'll burn. Others are big and fragile, but massive enough to destroy your ship if you hit one. Still others are ships like your own, plying space for fun, profit, or military purposes. An unknown number of the last are capable of whanging you with various and sundry weapons.

Your mission: without coming afoul of any of this, get to the flat tableland on top, then locate and dock to a group of fly-specks called L-5.

Try it on your computer. Good luck.

We'd run a gauntlet of low-orbit facilities and were coming up on geosynchronous orbit. Although we were several degrees above equatorial GEO where most of the civilian facilities were, we had to get through the web of military satellites in inclined geosynchronous orbit, weaving paths around the planet like a ball of yarn.

Omer asked the computer to enhance the very weak returns from these stealthed facilities. We were going to come close to some Japanese and European targets, but not within their engagement zones unless they'd changed them and we didn't know it.

From Manna by Lee Correy (G. Harry Stine) 1983 ]

Spacecraft Certification

If a spacecraft is flying far away from anything else, and only has weak rockets fueled by puny chemical fuels or innocuous solar panels, nobody cares if the ship is a hunk-of-junk suffering from decades of deferred maintenance. If it blows up, that's too bad about the people on board, but it's their problem.

Things change radically in the more civilized areas of space. In the crowded orbital space around a heavily populated planet, with dozens of space stations, zillions of expensive satellites, hundreds of other spacecraft in tight traffic lanes, and ship using antimatter fuel; the authorities will demand that all spacecraft be up to code with perfect maintenance records.

This means periodic inspections by the Spacecraft Agency, in order for the ships to keep their certification current. No certification means the ship ain't allowed in our orbital space.

For example, in the US, this is the responsibility of the Federal Aviation Administration's Aviation Safety Inspectors. They inspect aircraft and related equipment for airworthiness. They are a Designated Airworthiness Representative (DAR), appointed in accordance with 14 CFR 183.33 who may perform examination, inspection, and testing services necessary to the issuance of certificates. There are two types of DARs: manufacturing, and maintenance. The maintenance type are the ones inspecting aircraft.

The manufacturing type inspect the aircraft before it is even made. Aircraft require a type certificate to signify the airworthiness of an aircraft manufacturing design. This means it is almost impossible to certify an aircraft built from blueprints that lack a type certificate. Or built from no blueprints at all.

Customs Police In Space

(ed note: there was a news story about how the Volkswagen company was selling diesel automobiles containing a "defeat device" used to fraudlently pass emissions testing)

Tobias Klausmann

     This got me thinking: in an SF universe with spaceships (and possibly FTL), there probably is minimum standard for what is allowed to zip around at kilometers per second, as soon as space stations and the like are involved. Who does the certification? Even if there isn't an official body that tries to keep everyone safe, there will be a consensus, however muddy, about what (not) to do.
     When steam engines proliferated around the industrial revolution, there were quite a few horrendous boiler explosions, leading to the formation of standard bodies that would certify (and spot check, after initial approval) boilers.*
     Naturally, enforcing these standards is very difficult, especially if ad-hoc repairs are somewhat common on long missions. What you flew out with may have been certified, but what you came back with is just a mess of chicken wire and duct tape.
     In the case of only grass-roots "standardization", justice for endangering others with your hunk o' junk may be swift and airlock-shaped.

     * Historical side note: The organization that (among other things) checked vehicles for road safety in Germany (TÜV) was a descendant of such an organization (DKÜV, Dampfkesselüberwachungsverein, boiler inspection association), but these days there are various orgs that do this.

Ron Fischer

     Border or port inspections. Out system you'd be on your own, but as you got nearer populated colonies or Earth you'd be bored for an inspection, before proceeding. If I may say so this feels like a GREAT idea for some stories. Basically "Customs Police" in space.

Tobias Klausmann

     This naturally hinges on how the drive systems work. With choke points (like jump gates), this is easy, but with arbitrary-location jump drives, this becomes tricky. Naturally, arbitrary jump points are also a strategic nightmare, unless you can somehow see them coming, like jump-pre-echoes, for example.
     A problem I see with arrival inspections is that most ships can not be thoroughly inspected without a dock, and even then, testing all the fail-cutout machinery could easily take weeks, so short of having those components sealed, I don't see this as feasible, unless travel times are already in the neighborhood of months.
     It's also a question of system throughput: in a place where a hundred ships arrive a day and an inspection takes at least two days, you need an enormous amount of manpower to just do checks. And this manpower needs to be away from stations/ports, and thus becomes quite expensive.

Ron Fischer

     Interesting points. I wonder how its done now? Some of the inspection is done at the port of departure or even when a container is closed, no?

Tobias Klausmann

     There is a huge discrepancy between the two trades that come to mind first: aircraft and ships. For the former, airworthiness is a serious cost factor and it is baked into the manufacturing process of aircraft. For the latter, nobody gives a sh*t until something happens.
     The thing with space craft on mid- to long-haul service is that modification will probably be much more common. In a sense, they bridge the gap: they are as dangerous-delicate as aircraft, yet have away-from-port times as long as ships do (possibly longer).
     The problem is: a pilot is not expected to repair the aircraft mid-journey and there is often (but not always) a place to go in emergencies. A ship does not have that luxury, which, combined with a "healthy" dose of tradition and business sense means that repairs underway are somewhat common. The basic idea seems to be: if it floats, is not on fire or carrying disease, we're good.
     I am not sure how to solve the discrepancy when it comes to spacecraft. 

From a thread on Google+ (2015)

Space Habitat

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 orbit guard 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 hydralic 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 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.

Eclipse Phase


  • 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.

Mos Eisley Space Station 1


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
Mos Eisley Space Station 2

“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*****’ 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 s***.”

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 s***-house sewerslum right off station-end. Tell whoever’s hidin’ back there and breathe deep while y’can.”

“Close it up, boys. Message delivered.”

O'Neill Cylinder

    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)
Space Monasteries

(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

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
Asteroid Athens 1

(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.)

From Spomelife: The Universe and the Future by Isaac Asimov (1965)
Asteroid Athens 2

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)
Greek Republic

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)
Thalassocracy 1

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)
Thalassocracy 2

(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)
Habitat Lasers And Military Adventurism

(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 jt 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

Sample Space Habitat

Long-term plan: large modular 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.

From Long-term plan: large modular habitats by Chris Wolfe (2015)

Asteroid Bubble

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

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 ()

Space Superiority Platform

Many early SF stories fret about the military advantage an armed space station confer upon the owning nation. Heinlein says trying to fight a space station (or orbiting spacecraft) from the ground is akin to a man at the bottom of a well conducting a rock-throwing fight with somebody at the top. One power-crazed dictator with a nuclear bomb armed station could rule the world! Space faring nations would need space scouts for defense.

But most experts nowadays say that turns out not to be the case. A nation can threaten another with nuclear annihilation far more cheaply with a few ICBMs, no station is required. And while ground launching sites can hide in rugged terrain, a space station can hide nowhere. Pretty much the entire facing hemisphere can attack the station with missiles, laser weapons, and propaganda.

Phil Shanton points out that you don't need a huge missile to destroy an orbiting space station, either. In 1979, the U.S. Air Force awarded a contract to the Vought company to develop an anti-satellite missile. It was not a huge missile from a large launch site. It was a relatively small missile launched by an F-15 Eagle interceptor in a zoom-climb. Vought developed the ASM-135 Anti-Satellite Missile (ASAT), and on 13 September 1985 it successfully destroyed the solar observatory satellite "P78-1". This means that an evil-dictator world-dominator nuke-station not only has to worry about every ground launch site, but also every single fighter aircraft.

It has also been modeled that the U.S. Navy could take out a satellite with a Standard Missile 3.

Things are different, of course if the situation is an extraplanetary fleet that remotely bombs the planet to destroy all the infrastructure. The fleet can construct a space superiority platform while the planet is struggling to rebuild its industrial base. Then the platform can bomb any planetary site that is getting too advanced in rebuilding. This is known as "not letting the weeds grow too tall.


This section has been moved here.


Space Logistics Base

James Snead has written a few paper about space infrastructure. Most interesting is Architecting Rapid Growth in Space Logistics Capabilities. On page 23 he gives an example of an orbiting space logistics base, including a space dock. Refer to that document for larger versions of the images below.

...the space logistics base’s functions are: (1) housing for travelers and operating crews; (2) emergency care; (3) in-space assembly, maintenance, and repair; and (4) materiel handling and storage.

The example space logistics base consists of four elements. At the top in Fig. 10 is the mission module providing the primary base control facility, emergency medical support, and crew and visitor quarters. The personnel quarters are located inside core propellant tanks that are retained from the SHS used to launch the mission module. The overall length of the mission module and propellant tanks is approximately 76 m (250 ft). Solar arrays and waste heat radiators (shown cut-away in Fig. 10) are mounted on a framework surrounding the mission module to provide additional radiation and micrometeoroid protection.

The second element consists of twin space hangars. These serve as airlocks for receiving spaceplanes and provide a pressurized work bay for conducting on-orbit maintenance of satellites and space platforms.

As shown in Fig. 11, the space hangar consists of a structural cylindrical shell 10 m (33 ft) in diameter, a forward pressure bulkhead containing the primary pressure doors, and an aft spherical work bay. These elements, which define the primary structure, would be manufactured as a single unit and launched as the payload of an SHS. The large, nonpressurized, space debris protection doors would be temporarily mounted inside the hangar for launch and then demounted and installed during the final assembly of the hangar at the LEO construction site. All of the other hangar components would be sized for transport to orbit in the cargo module of the RLVs and then taken through the hangar’s primary pressure doors for installation.

Future logistics supportability is a key feature of this hangar design. The size, weight, location, and access of the internal hangar components enables them to be inspected, repaired, and replaced without affecting the primary structural / pressure integrity of the hangar. With the exception of the space debris protection doors, this would be done inside the hangar when it is pressurized. The ISS-type airlock and space debris protection doors, although mounted externally, would be demounted and brought into the hangar for inspection, maintenance, and repair. For the repair of the primary pressure doors, they would be demounted and taken into the spherical work bay or the other hangar for servicing.

The hangar’s design enables both pressurized and unpressurized hangar operations to be undertaken simultaneously. When the main hangar deck is depressurized to receive cargo or spaceplanes, for example, pressurized maintenance operations would continue inside the 9.8 m (32 ft) diameter spherical work bay and the 2.8 m (9 ft ) diameter x 4.3 m (14 ft ) work compartments arranged along the top of the hangar.

Hangar operations in support of the passenger spaceplanes, as shown in Fig. 12, highlight the improvement in on-orbit logistics support enabled by the large hangars. After entry into and repressurization of the hangar, the passengers would disembark from the spaceplane. Support technicians, working in the hangar’s shirtsleeve environment, would inspect the spaceplane and, in particular, the thermal protection system for any damage to ensure that it is ready for its return to the Earth. While at the space base, the spaceplane would remain in the hangar to protect it from micrometeoroid or space debris damage. Minor repairs to the spaceplane could also be undertaken to ensure flight safety.

The third element is the air storage system. The prominent parts of this system are the large air storage tanks that are the reused core propellant tanks from the two SHS used to launch the twin space hangars. Besides storing air from the hangars, this system also: manages the oxygen, carbon dioxide, and moisture levels; removes toxic gases, vapors, and particulates; and, controls the temperature and circulation of the air within the hangar and its compartments.

The fourth and final element is the space dock. It would be constructed from structural truss segments assembled within the space hangars using components transported to orbit in the RLVs. The space dock would provide the ability to assembly and support large space logistics facilities, such as the space hotels and large manned spacecraft described in the following. It could also used to store materiel and as a mount for additional solar arrays.

The space hangars and space dock would enable traditional logistics operations of maintenance, assembly, and resupply to be routinely conducted in Earth orbit. This is an enabling capability necessary to become spacefaring and achieve mastery of operations in space.

The space logistics base would have approximately 20 personnel assigned. The tour of duty would be 90 days with half of the crew rotating every 45 days. Crew rotation and base resupply would require approximately 32 RLV missions per year per base with 8 spaceplane missions and 24 cargo missions. This would provide approximately 12,000 kg (26,000 lb) of expendables and spares per person per year. At $37M per mission, a ROM estimate of the annual transportation support cost per base would be approximately $1.2B.

While the LEO space logistics base would have sufficient housing capacity to support the 20 assigned personnel and a modest number of transient visitors, it would not be a primary housing facility. Since people cannot simply pitch a tent and “camp out” in space, establishing early permanent housing facilities is an important and enabling element of opening the space frontier to expanded human operations. The architecture of the Shuttle-derived heavy spacelifter and the LEO space logistics base was selected so that the first large space housing complexes, referred to as space hotels, could be constructed using the same space logistics base modules.

A composite illustration of the design, assembly, and deployment of the example space hotel is shown in Fig. 13. This hotel design is configured as a hub and spoke design with a long central hub and opposing sets of spokes attached to the central hub module. This configuration makes it possible to use variants of the space base’s mission modules and space hangars as the primary elements of the space hotel’s design.

Element 1, in Fig. 13, shows the start of the hotel assembly sequence. The central hub module, shown with the SHS’s core propellant tanks still attached, is being positioned at the space logistics base’s space dock. The central hub module would be a version of the mission module used in the space logistics base. Its design would include 12 docking ports around its circumference for attaching the spokes.

Element 2 shows the completed hub and one attached spoke. Two space hangars are located at the ends of the hub and the first spoke is shown attached to the central hub module. In assembling the hub, the core propellant tanks from the two SHS missions used to launch the hangars would be incorporated into the hub to provide additional pressurized volume. This approach would be also used for the spokes. Each spoke would consist of a generalpurpose mission module with the SHS’s core propellant tanks reused for additional pressurized volume. As with the mission module on the space logistics base, the spokes would be surrounded by solar arrays and waste heat radiators. This is what provides their “boxy” appearance.

Element 3 shows the completed 100-person space hotel with two pairs of spokes on opposing sides of the hub. This is the baseline space hotel configuration. Seven SHS missions would be required to launch the hub and spoke modules for the baseline hotel. One additional SHS cargo mission would be used for the solar arrays and waste heat radiators.

This design enables the hotel to be expanded to 6, 8, 10, or 12 spokes. Each spoke would require one additional SHS mission. The 12-spoke configuration would accommodate up to approximately 300 people. Each additional spoke would be tailored to provide a specific capability, such as research and development facilities, tourist quarters, office space, retail space, etc.

Element 4 shows the completed space hotel after being released from the space dock. It also shows how the hotel would rotate about the long axis of the hub to produce modest levels of artificial gravity in the spokes. At about two revolutions per minute, a Mars gravity level is achieved at the ends of the spokes. This use of artificial gravity enables the spokes to be organized into floors (Element 5 in Fig. 13). Each spoke would contain 18 floors with 14 of these available for general use and the remaining 4 floors used for storage and equipment. The spokes would be 8.4 m (27.5 ft) in diameter. This would provide a useful floor area of approximately 42 m2 (450 ft2) per floor. The total available floor area in the baseline configuration would be 2,340 m2 (25,200 ft2). The 12-spoke configuration, having 192 floors total, would have 3 times this floor area—7,026 m2 (75,600 ft2) or about 23 m2 (250 ft2) per person.

An estimate can be made of the number of guests visiting the hotel each year. Assuming a 3:1 ratio of guests to staff, approximately 76 guests would be staying each night in the baseline configuration and 228 guests in the full configuration. With one third of the useful floors configured as guest cabins, two cabins to a floor, each cabin would have a useful area of approximately 21 m2 (225 ft2).* With an average stay of one week, approximately 4,000 guests and 12,000 guests would visit the 4- and 12-spoke hotels each year, respectively.

If each passenger spaceplane carries 10 guests, approximately 400 and 1,200 RLV flights would be required each year. With an additional 25% required for staff transport and resupply, the 4-spoke hotel would require about 10 flights per week and the 12-spoke hotel would require about 30 flights per week. If the RLVs could achieve a one-week turnaround time, and allowing for one in five RLVs being in depot for maintenance, 12 RLVs would be required to support the 4-spoke hotel and 36 RLVs for the 12-spoke hotel.†

At the $37M per flight cost discussed previously for first generation RLVs, the per passenger transportation cost would be approximately $3.7M. With this transportation cost structure, a sustainable space tourism or space business market may not be possible. However, if a second generation RLV could reduce this cost by a factor of 10 to $0.37M per passenger, as an example, then an initial market demand for the baseline hotel may develop and be sustainable. In such case, the annual transportation revenue for the baseline hotel would be $3.7M x 500 = $1.9B and the 12-spoke hotel would be $5.6B.‡ This improvement in transportation costs would also yield a savings of 90%—approximately $1B per year—in the transportation costs to support the LEO space logistics bases. Human space exploration missions would also realize a significant cost reduction.

While developing a conceptual design of a space hotel would appear premature at this early stage of considering the architecture of an initial space logistics infrastructure, several important conclusions emerge that indicate otherwise:

1) Careful selection of the initial space logistics architecture can also establish the industrial capability to build the first space hotels necessary to enable the expansion of human enterprises in space.

2) A commercially successful space hotel will require second generation RLVs to lower further the cost of transportation to orbit.

3) In order for these second generation RLVs to be ready when the first space hotel is completed, the technology research investment would need to begin concurrently with the start of the detailed design of the initial space logistics systems. Conversely, for private investment to seriously consider building the first hotels, significant science and technology progress in developing the second generation RLVs must be demonstrated by the time the initial hotel construction contracts are made.

4) The benefits of reduced space transportation costs will also substantially lower the cost of operation of the initial elements of the space logistics infrastructure, leading to a likely increase in demand for more in-space logistics services.

5) Space hotels and second-generation RLVs may become an important new aerospace product for the American aerospace industry, establishing American leadership in this new and growing field of human astronautical technologies.

6) It is not unrealistic to expect, with the building of an integrated space logistics infrastructure, that hundreds of people could be living and working in space by 2020, growing to thousands of people by 2040 with many of these living in the first permanent orbiting space settlements.

* A standard cabin on the new Queen Mary 2 cruise ship has an area of 18 m2 (194 ft2). A premium cabin has an area of 23 m2 (248 ft2).

† Launch sites for these RLVs would be distributed around the world. This would allow operations at the space hotel to run 24 hours per day since there is no day and night in LEO.

‡ This further reduction could come about through the introduction of a spiral version of the first-generation RLVs where improvements to the high maintenance cost subsystems, e.g., engines, could substantially reduce the recurring costs. Another approach would be development of entirely new RLV configurations—perhaps a single-stage configuration—that would also result in a substantial reduction in recurring costs per passenger through subsystem design improvements and the ability to carry more passengers per trip. A key issue in both approaches is the amortization of the development and production costs. High flight rates, probably dependent on space tourism, would be required to yield an overall transportation cost sufficiently low to enable profitable commercial operations.

Rocketpunk Manifesto Patrol Base

The comment thread on my previous post about space patrols raised the issue of base stations for more prolonged missions, extending to years.

This has application far beyond military or quasi-military patrols. In fact it is fairly fundamental to any extensive, long term human presence in deep space. Whether or not we put permanent bases on the surface of Mars, Europa, or wherever, we will surely place permanent or semi-permanent stations in orbit around them. Particularly because the stations can be built in Earth space, where the industry is (at least initially), and flown out to where they will serve.

Hab structures intended for prolonged habitation should be fairly large, if only because if you are going to live for years in a can it should be at least be a roomy one. And they must be thoroughly shielded against radiation, much more than ships that you only spend a few months aboard every few years.

So let us play with some numbers. Make our spin hab a drum, 200 meters in diameter and 100 meters thick. Volume is thus about 3.14 million cubic meters. The ISS has about 1200 m3 of pressurized volume and a mass of some 300 tons, for an average density near 0.25, but the mass includes exterior structures such as keel and wings. Let average interior density be about 0.16, for a mass of 500,000 tons.

If we allow 100 cubic meters per person the onboard population (whether 'crew' or simply residents, or a mix) can be up to 30,000 people. This is about twice the density of a middle class American urban apartment complex. Given that much of the usable volume must be working areas, public spaces, and so forth, the actual crew or population might be more on the order of 10,000 people, equivalent to a decent sized small town or a fairly large university or military base. Thus the hab has 10 times the volume of an aircraft carrier and twice as many people.

Spin the hab at 3 rpm and you get almost exactly 1 g at the rim.

By my standard rule of thumb the cost of this hab is on order of $500 billion. That is a steep price tag, but on the other hand it is only five times the cost of the ISS, and you need very few of these unless you are engaged in outright colonization.

Now, shielding. The standard for indefinite habitation is about 5 tons per square meter of cross section. (Earth's atmosphere provides about 10 tons/m2.) Portions of the hab where people do not spend much time, and exterior to where they do spend time, can be counted toward the shielding allowance. So let us say that the outer 10 meters of the interior (about 35 percent of the volume) are used for storage, equipment rooms, and the like. This provides about 2 tons per square meter of shielding, 40 percent of the requirement.

The remaining 3 tons per square meter of exterior shielding must cover about 125,000 square meters of surface, so shielding mass is about 375,000 tons, adding 75 percent to the mass of the hab, now 875,000 tons. This shielding need not be 'armor.' As I recall, water provides pretty good shielding against GCRs, your biggest radiation problem, and water is so useful that having 375,000 tons of it on hand in a reservoir will never be amiss.

Moreover, to move the hab you can vent off the water (or pump it out) and not need to lug the mass, assuming you can replace it wherever you are going. The deep interior of the hab, more than 25 meters from the surface (about 28 percent of the volume) is still shielded by the rest of the hab structure, so the hab can carry a reduced population during the transfer.

You are still moving a half million ton payload, so don't expect to rush it unless you have a really badass drive bus handy. Habs being repositioned across the Solar System probably travel on Hohmann orbits, and have drive accelerations of a few dozen microgees, good for about 1 km/s per month of steady acceleration.

For a smaller hab structure, scale down the linear dimensions by half, to 100 meters diameter and 50 meters thick. Structural mass, volume, and capacity are all reduced by a factor of 8, to 400,000 cubic meters, 60,000 tons, and a crew / resident population of about 1500-4000. Our 'mini' hab is now broadly comparable in volume, mass, and crew to an aircraft carrier.

Surface area is only reduced, however, by a factor of four, to about 30,000 square meters. Moreover, the smaller hab provides less interior self-shielding. If we keep the same proportions our internal reserved zone is just 5 meters deep and provides only 20 percent of the needed protection, not 40 percent.

We now need about 120,000 tons of shielding — twice the unshielded mass of the hab. If we move the hab fully shielded our payload mass is 180,000 tons. Remove the shielding and payload mass is just 60,000 tons, but no part of the smaller interior is fully self-shielded, so any crew on board during a 'light' transfer must be relieved every few months. On the bright side, if you have a 100 gigawatt drive bus floating around, or about $100 billion to buy one, you can take a fast orbit and get there in a few months.

The image shows a drum-hab station ship with a spin hab of the full sized type described above, 200 meters in diameter by 100 meters thick, fitted with a heaviest class drive bus for transfer. I am delicately ignoring details of the connection between the spin drum and the hub structures.

The shuttles approximate the NASA Shuttle, as a visual size reference. The deep space ships docking up to it are large fast transports, 300 meters long, ten times heavier than the patrol ship discussed last post. The station ship itself is about 675 meters long by 450 meters across the outrigger docking bays.

In my image the station ship is no aesthetic triumph. Allowing for my limitations as an graphic artist (compare to commenter Elukka, from the last comment thread), the transport class ships don't look too bad, but the station ship merely looks tubby instead of grand. Some modest architectural improvements might yield a more impressive appearance with little change in overall configuration.

Of course the interior will matter immeasurably more to the people on board. Mostly, presumably, it will resemble the interior of a very large oceangoing ship, corridors and compartments, probably including some fairly imposing public spaces, comparable to the grand saloon of a 20th century ocean liner or even larger. It can be as elegant or as sterile as you like (or both, depending on deck and sector). The third popular choice, rundown industrial gothic, is constrained by how far you can go in that direction before the algae dies or the air starts leaking out.

From Home Away From Home by Rick Robinson (2010)

NASA Space Station: Key to the Future

This is from a 1970 brochure from NASA called Space Station: Key to the Future, as documented by David Portree. The station is cylindrical with a diameter of ten meters, and houses a crew of 12. The station is somewhat extravagant, down to the wood panelling on the crew quarters.

North American Rockwell Phase B

In 1969, NASA awarded Phase B Space Station study contracts to McDonnell Douglas Aerospace Company and North American Rockwell. This is the from the NA Rockwell study, described in detail in David Portree's blog.

The station was to have a crew of 12, launched into a 500 kilometer high orbit by a two-stage Saturn V, with a lifespan of 10 years (the ISS is in an altitude that varies between 330 and 435 km). The orbit is inclined at 55° to the equator, approximately the same as the ISS.

The station is 10 meters in diameter and 15 meters tall (not including the power boom).

The station was designed to serve as a modular building block for larger projects. Several modules could be joined to make a huge 100 crew space base. A half module could be used as an outpost space station or as the habitat module for a Mars mission spacecraft.

The design was solar powered, to enhance modularity. RTGs could power a 12 man station, but not a 100 crew base. A nuclear reactor suitable for a 100 crew base cannot be economically scaled down to a 12 man station. Solar power is easily scaleable.

The solar power boom carries four collapsible steerable solar arrays. Total area of solar array is about 900 square meters, power output is 25 kilowatts. Power boom is attached to conical airlock in upper equipment bay.

Decks 1+2 and decks 3+4 are independent living volumes, for crew safely. They are joined by an inter-volume airlock adjacent to the repair shop on deck 3. So if, for instance, a fire broke out on deck 4, the crew in decks 3 and 4 would evacuate through the inter-volume airlock into decks 1+2. They would then seal the airlock and call NASA for help.

Krafft Ehrickes Atlas Space Station

Back in late 1957, the United States was feeling very smug. They were the most powerful nation on Earth, had the biggest and the best of everything, and above all were the most technologically advanced. Their biggest rivals were the Soviet Union. But their technologists were a bunch of stupid farm boys who wouldn't recognize a scientific innovation if it flew straight up their behind. Life was good for the U.S.A.

The US was even ready to meet the challenge of the International Geophysical Year. The IGY officials had adopted a resolution for something straight out of science fiction: create something called an "artificial satellite" and launch it into something called an "orbit" in order to map Earth's surface duntDah DUUUHHHH! from Spaaaaaaace!. The US had been working with the Martin Company since 1955 on the Naval Research Laboratory's Vangard satellite. The US was looking forwards to yet again demonstrating the unstoppable advantage of good old US know-how.

Then one fine day the Soviets quietly told a few people to watch the skies that night. Oh, and tune your radio to 20 megacycles while you are at it.

On 4 October 1957 at 19:28:34 UTC, the Soviets launched the world's first artificial satellite into orbit, called Sputnik 1. No propaganda lie was this, you could see the blasted thing orbiting with a low powered telescope, and there was that accursed BEEP-BEEP-BEEP coming clearly at 20 megacycles. The Space Age had started.

The United States freaked out.

The reaction was a mix of stunned incredulity, incandescent rage, and hysterical panic. Incredulity that the "backwards" Soviets could beat the US at its own game. Rage at being demoted to "also ran" status in the race. And panic because it would be just a matter of time before those evil Soviets put nuclear warheads on their satellites. Yes, Sputnik was a miserable half meter sized ball that couldn't do more than make beep-beep noises. But the US couldn't even do that much.

Sputnik directly caused the US to create NASA. And ARPA (which later became DARPA). ARPA's mission statement was "See that Soviet Sputnik? DON'T LET THAT HAPPEN AGAIN, EVER!" (although the actual command was worded something like "help the US regain its technological lead"). The National Science Foundation also got a $100 million dollar budget increase and was told to start cranking out as many new engineers as it could possibly make. Right Now.

Things got worse when the US tried to launch its answer to Sputnik. On December 6, 1957, Vanguard TV3 was launched from Cape Canaveral. The event was carried live on US TV, which in hindsight was a rather poor decision. Viewers across the nation witnessed Vanguard's engines igniting, the rocket's rise to an altitude of almost 1.2 meters, the fall back to the launch pad, and the spectacular fiery explosion.

The smoking remains of the Vanguard satellite rolled across the ground, pathetically still sending its radio beacon signal. In the radio shack, the crew was unaware of the explosion, and were troubled that they could no longer receive the signal. Somebody picked up the charred remains of Vanguard and walked into the shack. As he entered, the radio operators excitedly announced that they were suddenly picking up the signal loud and clear!

Meanwhile on Wall Street, they had to temporarily suspend trading in Martin Company stock as it plummeted in value. The news media was not kind, calling Vanguard uncharitable names such as "Flopnik", "Kaputnik", "Oopsnik", and "Stayputnik". To say this was an international humiliation was putting it mildly. A few days after the incident, a Soviet delegate to the United Nations inquired solicitously whether the United States was interested in receiving aid earmarked for "undeveloped countries”. Ouch.

Then in April 25, 1958, in the middle of all this gloom and doom, Dr. Krafft Ehricke goes to Washington. He was one of the genius scientists from Nazi Germany who was scooped up by Operation Paperclip. In 1958 he was working for Convair.

Part of Dr. Ehricke's genius was his practicality. He knew if you had to get something developed quickly, the design time had to be minimized. Indeed, you could cut the time drastically if you can find a way to modify some off-the-shelf technology instead of starting from scratch. As it happened, Convair had created the SM-65 Atlas rocket which was the US's first ICBM and the largest rocket it had at the time. Dr. Ehricke noticed that the Atlas could boost a small payload into orbit. In fact, it could boost itself into orbit.

What if you stop looking at the Atlas' giant fuel tanks as fuel tanks and instead saw them as a ready-made space station hull? Why, you would have the Soviets sputtering in rage as the unmanned Sputnik 1 and the dog-manned Sputnik 2 were savagely upstaged by the Man-manned US space station!

Dr. Ehricke's design was a four-man nuclear powered space station that could be built using existing Atlas rockets. As the cherry on top of the sundae, it could be spun for artificial gravity. It could be bulit in five years at a cost of about half a billion 1958 dollars.

The station was never built, which was a pity because it would have worked! Years later in 1973 Dr. Ehricke's concept was used for NASA's Skylab. It too was a space station build out of a spent upper stage. Technically Ehricke's design was a wet workshop while Skylab was a dry workshop, but the basic idea is there.

The Hawk plastic model company wasted no time making a model kit of Ehricke's space station. It was first issued in 1960, and later re-issued in 1968 (which was when I got my copy of the kit).

The Station is 32 meters long with a mass of 6.8 metric tons. It can house a four man crew. It orbits at an altitude of 640 kilometers. Power is from a SNAP-2 nuclear reactor with an output of 55 kilowatts. Each glider carries two men. The vernier rockets will spin up the station around the entry port spin axis at a rate of 2.5 times per minute, to provide artificial gravity of 0.1 to 0.15g. Pretty darn impressive for 1958. Actually it would be quite impressive today, the International Space Station has no artificial gravity nor nuclear power.

The nose end of the station is for the habitat module. Outside of the sanitary room on the tip of the nose is a condenser cooler for the water regeneration system and a waste disposal outlet (yes, when you flush the toilet you are spraying sewage into a wide arc like a water-sprinkler. Take that, Khrushchev!). Oxygen is from a tank in the rear end, but the habitat module has a small emergency oxygen tank.

Naturally there are some drawbacks to using an Atlas. One of them is the dimensions. While the Atlas is 22.8 meters long, it is only 3 meters in diameter. So the living spaces are going to be a bit cramped. Especially since the pointed nose section grows even narrower than 3 meters.

The rear end is to store heavy equipment. It would hold oxygen tanks, water supply, emergency power supply (batteries), vernier rocket propellant tanks (to start and stop the artificial gravity spin), tools, reserve equipment, and instrumentation.

The entrance is located near the midpoint, at the spin axis. It is surrounded by a basket-funnel to aid astronauts to enter and exit. It leads to the unpressurized interior. The habitat module in the nose has an airlock above the control room.

Construction of the station will take about one week. Once operational, the station will initially rotate crews back to Terra after every two weeks, later once a month. A cargo ship will deliver 3,600 kilograms of supplies once a year. A total of 13 to 20 launches a year would be required to maintain the station.

The station can be expanded with the upper stage tanks of cargo and passenger vessels. Small satellites can be added to the system — with or without rotation — for housing telescope and other instruments.

Space station functions:

  • As a test bed for long-term evaluation of development of equipment and living conditions in advanced manned satellites, lunar and interplanetary spacecraft.
  • To teach crews to live in space and to prepare for flights to other planets.
  • To serve as a base for launching improved interplanetary research probes to Venus, Mars, and the outer solar system.
  • As a base for weather observation (the transistor had just been invented) and to monitor terrestrial activities (i.e, spy on enemies of the US, like those vile Sputnik-launching Soviets)
  • As a base for geophysical and astrophysical research.
  • As a maintainance base for satellites in suitable orbits.
  • As a base for assembly, testing, and launching of lunar reconnaissance vehicles.

Construction of the station should take about one week.

  1. An Atlas is boosted into a 640 kilometers high orbit, arriving with empty tanks. It will become the hull of the station.
  2. One personnel vehicle (carrying four man alpha crew and two gliders) and one cargo vehicle (carrying equipment for rear of station) are launched, and rendezvous with the empty Atlas.
  3. Using the gliders, the alpha crew moves the equipment from the cargo vehicle to the empty Atlas.
  4. The alpha crew installs in the Atlas emergency power (batteries), water, and oxgen supply systems.
  5. One personnel vehicle (carrying a four man beta crew and two gliders) and one cargo vehicle (carrying equipment for nose of station) are launched, and rendezvous with the Atlas.
  6. The alpha crew returns to Terra via their two gliders.
  7. Beta crew places rubber nylon balloon inside nose of station, and inflates it to create pressurized habitat module. The four decks are installed, with all the insulation, furnishings and equipment. Water recycling system installed in sanitary room. Food is stored and the water & air cycles are tested using emergency battery power.
  8. One personnel vehicle (carrying a four man gamma crew and two gliders) and one cargo vehicle (carrying SNAP-2 nuclear reactor, shadow shield, and heat radiator) are launched, and rendezvous with the Atlas.
  9. The beta crew returns to Terra via their two gliders.
  10. The gamma crew installs the nuclear reactor. Water and air cycles would be started using reactor power. Vernier rockets are fired to spin the station for artificial gravity.
  11. The station is now operational.
  12. Crews are rotated once a month.

Krafft Ehrickes Astropolis

This is another interesting design from Dr. Krafft Ehricke.

Astropolis was to be an orbital hotel and space resort, that is, yet another desperate attempt to monetize space/discover some MacGuffinite. The details can be found in Space Tourism by Krafft Ehricke (1967), collected in Commercial Utilization of Space, Volume 23 Advances in the Astronautical Sciences. It is available to patrons of the Aerospace Projects Review Patreon campaign.

The entire idea is based on the exceedingly optimistic assumption that boosting payload and passengers into LEO could be brought down to $10 US per pound ($22 per kilogram) in 1967 dollars (about $150/kg in 2015 dollars). By way of comparison NASA's space shuttle never got below $10,416/kg, and the Russian Proton-M is lucky to only cost $4,302/kg. So we still have some work to do in that department.

The primary attraction seems to be the variable gravity.

The station has a (residential) radius of about 122 meters, which means it can have one full gravity at the rim with a safe spin of only 2.7 revolutions per minute. Above 3 RPM the customers will start suffering from Coriolis nausea and Astropolis' Yelp score will fall off a cliff.

At the core, the yellow Zero-G Dynarium offers free-fall fun, with 3-D tennis, artificial flying wings, three-dimensional swimming pool and everything. The yellow Asteroid Room contains a simulated asteroid the customers can observe through windows or suit up and explore first hand. Both are about 61 meters in diameter.

The Mars Room, Mercury Room, Moon Room, and Titan Room are all set at distances from the spin axis such that their ground levels are under the same gravity as their namesake. Each is a flat plate covered in a hemispherical dome, with support equipment hidden under the plate. They contain carefully created simulations of the various planets with duplicated atmospheres and all the details. The domes are animated with projectors to create the illusion of the sky. Again customers can observe the rooms through windows, or don space suits for some real-life exploration.

The 0.35 g Dynarium and the Orbital Ballet Theater allows experiencing the fun to be had under one-third of a g. I'm sure the ballet will be amazing, with truly heroic leaps.

There are extensive space boat docks for touring the exterior of the station in little putt-putt spaceships. And for the stick-in-the-muds guests, there is a theater, beauty salon/barber shop, restaurant/ball-room, and a casino all at a conventional 1 g. And no doubt a tourist trap gift shop selling cheap crap at inflated prices.

Don't forget the incredible ever-changing view of Terra, the various photos taken from the International Space Station show the view is sufficiently awesome that it is probably worth the price of the trip all by itself. For maximum global sight-seeing, the hotel will probably be in a polar "ball-of-twine" orbit (the one used by military spy satellites) so every centimeter will be covered. These might be viewed by TV cameras instead of by direct vision windows, to compensate for the fact the station is spinning.

The guest quarters modules ("hotels") are cylinders with 9 meter inner diameter and about 48 meters tall. There are 13 floors, each floor a cylinder with a 9 meter diameter and 3.7 meters tall. 11 floors have four beds, 2 floors (uppermost and lowermost) have only two beds, for a total of 50 beds. Complete floors are rented as four-bed suites, other floors are divided in half to create a pair of two-bed hotel rooms. One floor has a area of about 64 square meters, and four-bed suite has a volume of about 235 cubic meters.

Naturally each floor has a lower gravity than the floor below it. The bottom floor will have 1 g, the top floor will have the same 0.35 g as the orbital ballet theater.

There are six hotel modules side-by-side in a "wing", and Astropolis has four wings. This is a total of 24 hotel modules, for a total of 1,200 beds. Reserving 100 beds for the station service personnel leaves 1,100 beds for guests.

The hotel could hold 1,100 guest at a time, for about 400,000 guest-days per year. Dr. Ehricke estimated a rent of $80 per guest-day with a profit of $5 (in 1967 dollars) or $5,500 profit per day when fully booked (about $39,000 per day in 2015 dollars). See the original report for a detailed break-down of the business expenses.

Nowadays such a resort would be a liability-lawsuit nightmare. It contains far to many ways that a clumsy or stupid guest could accidentally kill themselves. Space suits can malfunction, and the little space boats might accidentally ram the station or pass to close to the radioactive nuclear reactors. Guests will have to sign iron-clad release forms, and even then Astropolis will have trouble obtaining liability insurance.

This design was copied for the regrettably abysmal TV movie Earth II in 1971.

Self-Deploying Space Station

This clever design solves the problem of how to quickly assemble a wheel space station, with one tiny little drawback. You see, there is a reason that wheel space stations are shaped like, well, wheels and not like hexagons.

The amount of centrifugal gravity experienced is determined by the distance from the axis of rotation (the greater the distance, the stronger the gravity). So if you want the amount of gravity to be the same, the station has to be a circle.

Now, look at the image below. The segment labeled "SPACE STATION RIGID MODULE" is one of the hexagonal sides. The green lines lead to the axis of rotation (i.e., that is the direction of "up". Note the little dark men figures, they feel like they are standing upright). And the red lines are lines of equal gravity. You will note that they do not align with the module.

In the module, centrifugal gravity will be weakest at the center of the module, and strongest at the ends where it joins with the neighbor modules. Even though the module is straight, the gravity will feel like it is a hill. If you place a marble on the deck in the center, it will roll "downhill" to one of the edges.

As you see, the designers tried to compensate for this by angling the decks, but it really doesn't work very well. They also put in secondary floors where the angle got too steep. The metric was to try and keep the variation in gravity across one module to within 0.02-g.

The problem this design was intended to solve was that of a lack of experience in free-fall construction. In the 1960's Langley Research Center concluded that assembling a space station out of component parts in orbit would not be practical until after 1975 or so. You need to gain expertise in the orbital rendezvous of many seperatly launched sections, gain skills in making mechanical, fluid, and electrical connections in free fall, and other problems. This space station was to do an end-run around the problems. No need to rendezvous or making connections if the thing is launched as one part. The only problem is figuring out how to fold the station up so it will fit in the rocket, and how it transforms into the full station.

Historically, NASA figured out how to make mechanical, fluid, and electrical connections in free fall by 1998 at the latest. The International Space Station was indeed assembled in orbit out of component parts launched separately.

The station was 150 feet across the hexagonal corners, central hub 12.8 feet in diameter and 29 feet high. When folded for launch it was 33 feet in diameter and 103 feet high (not counting the Apollo spacecraft on top. Total mass (including the Apollo) was 170,300 pounds. The rim modules were cylinders 10 feet in diameter and 75 feet long. They are hinged where they connect. When operational, the station would rotate at 3 rpm to generate 0.2-g artificial gravity at the rim. The spokes were 5 feet in diameter and 48 feet long. It would hold 21 crew members.


Somewhat more elaborate in conception is the 94 ft wheel-shaped satellite prepared by two design engineers of the Lockheed Missile Division. This celestial laboratory for a crew of 10 weighs 400 tons, and is intended to orbit at a height of 500 miles. Each pre-fabricated section is 10 ft in diameter and 20 ft long, fitted with airlocks, and weighs 10 tons delivered into orbit. Powerful 3-man "astro-tugs" would round up the orbiting packages and couple them up. The entire operation should not take more than a month. The whole design has been investigated in exceptional detail, and is complete with nuclear power reactor and propulsion unit for changing orbit, astronomical telescopes, computer room, space-medical laboratory, airlocks for access, etc. All gravitational worries would be relieved by rotating the vehicle about its hub, which would remain stationary for observational purposes.

The Lockheed space station made an apperance on the 1959 TV show Men into Space. I have not seen this show, but from what I've read it was astonishingly scientifically accurate. Certainly more accurate than most anything from TV or movies in the last couple of decades. Thanks to Drake Grey for bringing this to my attention.

McDonnell Douglas Phase B

In 1969, NASA awarded Phase B Space Station study contracts to McDonnell Douglas Aerospace Company and North American Rockwell. This is the from the McDonnell Douglas study, described in detail in David Portree's blog.

The design goal was a 12-person space station that could be lofted into orbit atop a two-stage Saturn V rocket, have a 10 year operational life span, and serve as a building block for a future 100 person Terran Orbital Space Base.

Because it was to be lofted by a Saturn V, the station had a maximum diameter of 9.2 meters. In launch mode, the station is 34 meters long. It would be placed in a 456 kilometer high circular orbit inclined 55° relative to the equator.

The station is remotely monitored for 24 hours to check the vital systems. If it passes, the crew will be delivered. A space shuttle carrying a Crew/Cargo Module (CCM) containing the 12 crew will arrive at the station. The CCM will deploy and dock with the station. All the docking ports are standarized at 1.5 meters in diameter.

The shuttle will hang around for about 25 hours (after deploying CCM) while the crew manually checks out all the station systems. That way the shuttle can evacuate the crew if the station turns out to have a major malfunction. If everything checks out, the shuttle will return to Terra.

The shuttle will deliver a logistics load eveyr 90 days: 13,000 kilograms of supplies and a new crew. While the new CCM is docking on a station side docking port, the old CCM will load up with the old crew and travel to the shuttle's cargo bay. Then the shuttle will transport the old CCM and crew back to Terra.

Each crew would contain eight scientist-engineers and four Station flight-crew. The crew work round the clock, with six people on duty and six off at all times. Two flight-crew and four scientist-engineers will work during each 12-hour shift.

One scientist-engineer would serve as principal scientist. They would work closely with the flight-crew commander, who would have responsibility for the safety of the entire crew, to ensure that science interests were taken into account during Station operations.

Two scientist-engineers would serve as principal investigator representatives. They would use the Station's considerable communications capabilities to work directly with scientists on Earth.

Station's orbital altitude is maintained by low-thrust resistojets utilizing hydrogen for propellant. Hydrogen is obtained by electrolyzing waste water. It was calculated that the water delivered in the food supplies was sufficient to maintain the station's altitude.

Pratt and Whitney Space Station

Herman Potocnik Design

This is from those innocent days before the discovery of nuclear power. The station uses solar power in the form of mercury boilers, since these were also the days before the discovery of the photoelectric effect.

Smith and Ross Design

Station desgined by R.A.Smith and H.E.Ross (circa 1940). Again, the station is powered by mercury boilers. The telescope uses a coelostat to counteract the spin of the station. The antenna support arm is de-spun to allow a spacecraft to dock, then is spun up to allow the air-lock module to mate with the station habitat module.

Space Shuttle External Tanks

RocketCat sez

NASA had a fleet of Space Shuttles. Because the sob sisters were screaming too loud NASA was not allowed to make them nuclear powered like they should have been. Forced they were to make them use chemical fuel, which makes about as much sense as powering an earth-moving caterpillar tractor with a huge wind-up spring.

The The Tyranny of the Rocket Equation demanded big fuel tanks. Really really big. As in "bigger than the Shuttle Orbiter" big. Forty-six point nine freaking meters long big.

And what did the shuttle do when it had dragged this 26 metric ton eleven-story tall external tank through Terra's gravity well to the edge of LEO?

It ditched the tank into the ocean, that's what. Along with the priceless one metric ton of liquid hydrogen and the priceless six metric tons of liquid oxygen left over. Per tank.

Have you any idea what sort of huge space city we could have built up there with 133 empty Shuttle tanks? One that has the habitable volume equal to 297 International Space Stations, that's how huge. At 17 cubic meters per person living space that's enough for a population of 16,000.

Now was this the most idiotic waste of materiel that ever boggled the mind or was it justified. I suspect the former, but NASA does make some good points in its defense (abet a bit stridently). You decide.

The space shuttle external tank (ET) is 46.9 meters long, 8.4 meters in diameter. It has a dry mass of 26,500 kilograms. It has two internal tanks, one for liquid hydrogen and one for liquid oxygen. The LH2 tank has an internal volume of 1497 cubic meters, the LOX tank has a volume of 553 cubic meters. Total volume of 2,050 cubic meters.

Once the shuttle was 97% of the way to LEO, it does an OMS burn in order to ditch the external tank into the Indian ocean.

NASA studied several concepts in the 1980's using the 'wet workshop' approach to the capacious External Tank carried into orbit with every shuttle flight.

Despite the incredible logic of this, NASA management never pursued it seriously — seeing it as an irresistible low-cost alternative to their own large modular space station plans.

According to NASA the main reason they never boosted shuttle external tanks into orbit was that this would decrease the payload capacity. Even when you figure the shuttle will no longer have to perform the OMS burn to ditch the tank into the ocean. More fuel will be used overall.

NASA says the secondary reason is that the tank is totally coated with foam insulation. In LEO this will fall off in huge massive chunks creating a major space debris problem. An expensive total redesign could fix this (putting the foam inside the shell), but this too would probably reduce the payload capacity. Remember that NASA stopped painting the tanks after the second shuttle mission in order to save on mass.

NASA says the third reason is nobody wanted the tanks in orbit.

What does NASA have to say about this ?

NASA operates the Shuttle, so NASA is the authority/boss. Prodded by outside inquiries, NASA eventually supported a study into retaining the tank in orbit, and the result was more positive than expected at first.

However, NASA has taken on a policy of relying on business to take the initiative in this area instead of government, which most of us will probably agree with. (NASA is not much of a leadership agency anymore.) Indeed, an external tanks space station would be a direct competitor to the NASA space station Alpha and the joint US-Russian space station effort that has gained so much political support and money for NASA.

NASA doesn't want to spend its limited budget on the infrastructure required to bring these tanks to orbit and handle them. NASA has offered to deliver the tank to orbit for free, but at the same time has pointed out a number of complications and costs involved to the Shuttle program and established understandable conditions for delivery, mainly for a third party to be waiting to collect it for at least safety reasons.

There is no system in orbit to collect these tanks, and NASA can't be expected to modify its clients' launch schedules and orbits to accommodate putting all the tanks in close orbits to each other.

Nonetheless, NASA has stated what is needed to utilize the tanks, e.g., a system to collect the tanks and control them so that they don't become a hazard, a way to pump the residual fuel out of the tanks, a way to outfit the tanks with the desired contents (by teleoperated robots or human extravehicular activity), and various infrastructure. NASA is not willing to launch the material to be moved inside the tank, but is willing only to give an empty tank which anyone can dock with later, on their own. NASA is not willing to devote much shuttle astronaut time or resources on behalf of the tank client, and any client requests to the manufacturer of the tank to redesign the tank must not entail any risk to the mission at all, i.e., probably no significant redesigns of the tank will be acceptable.

Fair enough. NASA has done its part; now it's up to business to come up with a best scheme to capitalize upon such an opportunity, without using U.S. taxpayers' dollars and without interfering too much with the Space Shuttle's agenda.

(ed note: but no business did.)

From Mark Prado (1997)
Wet Workshop

Wet workshop is the idea of using a spent rocket stage as a makeshift space station. A liquid-fuel rocket primarily consists of two large, airtight fuel tanks; it was realized that the fuel tanks could be retrofitted into the living quarters of a space station. A large rocket stage would reach a low Earth orbit and undergo later modification. This would make for a cost-effective reuse of hardware that would otherwise have no further purpose, but the in-orbit modification of the rocket stage could prove difficult and expensive.

A wet workshop is contrasted with a "dry workshop", where the empty upper stage is internally outfitted on the ground before launch with a human habitat and other equipment. Then the upper stage is launched into orbit by a sufficiently powerful rocket.

Shuttle-derived concepts

Several similar conversions of the Space Shuttle's external tank (ET) were also studied. During launch the ET accelerated to about 98% of orbital speed before being dropped and deliberately spun in order to increase its drag. A number of people proposed keeping the ET attached to the Shuttle all the way into orbit, bleeding off any remaining fuel through the Space Shuttle Main Engines, which would have been "left open". One such test had been scheduled, but was canceled after the Space Shuttle Challenger disaster dramatically changed safety rules.

The ET would have provided a huge working space, and one major problem with various wet workshop designs is what to do with all of it. The oxygen tank, the smaller of the two tanks inside the ET, was itself much larger than the entire Space Station Freedom even in its fully expanded form. Additionally, getting access to the interior was possible though "manholes" used for inspection during construction, but it was not clear if realistic amounts of building materials could have been inserted into the tank after reaching orbit. Nevertheless the problem was studied repeatedly.

A similar concept, the "Aft Cargo Carrier", was studied by Martin Marietta in 1984. This consisted of a large cylindrical cargo container bolted onto the bottom of the ET, which offered the same volume as the Space Shuttle orbiter's cargo bay, but would be able to carry wider, bulkier loads. The same basic layout was also used as the basis for a short-duration station design. Although not a wet workshop in the conventional sense, the station piggybacks on the fuel tank and is therefore related to some degree.

From Wet Workshop Wikipedia

Tank-Farm Dynamo

(ed note: the space station is composed of numerous cast-off Space Shuttle external tanks)

Imagine six very long parallel wires, hanging in space, always aimed toward the surface of the Earth 500 kilometers below.

At both ends the wires are anchored to flat rows of giant cylinders — forty in the upper layer, A Deck; and sixteen in the lower, B Deck. An elevator, consisting of two welded tanks, moves between the two ends, carrying people and supplies both ways.

I've lost count of the number of times I've explained the curious structure to visitors. I've compared it to a double-ended child's swing, or a bolo turning exactly once always high. It's been called a skyhook, and even a bean-stalk, though the idea's nowhere near as ambitious as the ground-to-geosynchronous space-elevators of science fiction fame.

The main purpose of the design is simply to keep the tanks from falling. The two massive ends of the Farm act like a dipole in the gradient of the Earth's gravitational field, so each deck winds up orbiting edge-forward, like a flat plate skimming. This reduces the drag caused by the upper fringes of the atmosphere, extending our orbital lifetime.

The scheme is simple, neat, and it works. Of course the arrangement doesn't prevent all orbital decay. It takes a little thrust from our aluminum engines, from time to time, to make up the difference.

Since our center of mass is traveling in a circular orbit, the lower deck has to move much slower than it "should" to remain at its height. The tethers keep it suspended, as it were.

The upper deck, in turn, is dragged along faster than it would normally go, at its height. It would fly away into a high ellipse if the cables ever let go.

That's why we feel a small artificial gravity at each end, directed away from the center of mass. It creates the ponds in my garden, and helps prevent the body decay of pure weightlessness.

The super-polymer tethers that held the Tank Farm together were sheathed in an aluminum skin to protect them from solar ultraviolet radiation. Unfortunately, this meant there was an electrical conducting path from B Deck to A Deck. As the Farm swept around the Earth in its unconventional orbit, the cables cut through a changing flux from the planet's magnetic field. The resulting electrical potentials had caused some rather disconcerting side effects, especially as the Tank Farm grew larger.

"Well, sir," Emily said, almost without a trace of accent, "I wasn't able to find a way to prevent the potential buildup. I'm afraid the voltage is unavoidable as the conductive tethers pass through the Earth's magnetic field.

"In fact, if the charge had anywhere to go, we could see some pretty awesome currents: One deck might act as a cathode, emitting electrons into the ionosphere, and the other could be an anode, absorbing electrons from the surrounding plasma. It all depends on whether ..."

Emily went on single-mindedly, apparently unaware of my split attention. "... so we could, if we ever really wanted to, use this potential difference the tethers generate! We could shunt it through some transformers here on A Deck, and apply as much as twenty thousand volts! I calculate we might pull more power out of the Earth's magnetic field, just by orbiting through it with these long wires, than we would ever need to run lights, heat, utilities, and communications, even if we grew to ten times our present size!"

"Emily." I turned to face the young woman. "You know there ain't no such thing as a free lunch. Your idea certainly is interesting. I'll grant you could probably draw current from the tethers, maybe even as much as you say. But we'd pay for it in ways we can't afford."

Emily stared for a moment, then she snapped her fingers. "Angular momentum! Of course! By drawing current we would couple with the Earth's magnetic field. We would slow down, and add some of our momentum to the planet's spin, microscopically. Our orbit would decay even faster than it already does!"

For an instant I saw the Earth not as a broad vague mass overhead, but as a spinning globe of rock, rushing air, and water, of molten core and invisible fields, reaching out to grapple with the tides that filled space. It was eerie. I could almost feel the Tank Farm, like a double-ended kite, coursing through those invisible fields, its tethers cutting the lines of force — like the slowly turning bushings of a dynamo.

That was what young Emily Testa had compared it to. A dynamo. We could draw power from our motion if we ever had to — buying electricity and paying for it in orbital momentum. It was a solution in search of a problem, for we already had all the power we needed.

The image wouldn't leave my mind, though. I could almost see the double-ended kite, right there in front of me ... a dynamo. We didn't need a dynamo. What we needed was the opposite. What we needed was ...

"What seems to be the problem, Colonel?"

"You know damned well what the problem is!" the man shouted. "Colombo Station is under acceleration!"

"So? I told you over dinner to have your crew check their inertial units. You knew that meant we would be maneuvering."

"But you're thrusting at two microgees! Your aluminum engines can't push five thousand tons that hard!"

I shrugged.

"And anyway, we can't find your thrust exhaust! We look for a rocket trail, and find nothing but a slight electron cloud spreading from A Deck!"

"Nu?" I shrugged again. "Colonel, you force me to conclude that we are not using our aluminum engines. It is curious, no?"

"Rutter, I don't know what you're up to, but we can see from here that your entire solar cell array has been turned sunward. You have no use for that kind of power! Are you going to tell me what's going on? Or do I come back up there and make myself insufferable until you do?"

"Oh, there won't be any need for that." I laughed. "You see, Colonel, we need all that solar power to drive our new motor."

"Motor? What motor?"

"The motor that's enabling us to raise our orbit without spending a bit of mass — no oxygen, not even a shred of aluminum. It's the motor that's going to make it possible for us to pull a profit next year, Colonel, even under the terms of the present contract."

Bahnz stared at me. "A motor?"

"The biggest motor there is, my dear fellow. It's called the Earth."

The voice faded behind me as I drifted up to the crystal port. Outside, the big, ugly tanks lay like roc eggs in a row, waiting to be hatched. I could almost envision it. They'd someday transform themselves into great birds of space. And our grandchildren would ride their offspring to the stars.

Bright silvery cables seemed to stretch all the way to the huge blue globe overhead. And I know, now, that they did indeed anchor us to the Earth ... an Earth that does not end at a surface of mountain and plain and water, nor with the ocean of air, but continues outward in strong fingers of force, caressing her children still.

Right now those tethers were carrying over a hundred amps of current from B Deck to A. There, electrons were sprayed out into space by an array of small, sharp cathodes.

We could have used the forward process to extract energy from our orbital momentum. I had told Emily Testa earlier today that that would solve nothing. Our problem was to increase our momentum.

Current in a wire, passing through a magnetic field ... You could run a dynamo that way, or a motor. With more solar power than we'll ever need, we can shove the current through the cables against the electromotive force, feeding energy to the Earth, and to our orbit.

A solar-powered motor, turning once per orbit, our Tank Farm rises without shedding an ounce of precious mass.

From Tank-Farm Dynamo by David Brin

Fortress on a Skyhook


High Crusade

Apparently the artist who did the book cover had seen this old Soviet space station design. I have not been able to discover any details about the station, except that the model is apparently hanging in some Russian museum.

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