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.

The Hill Sphere

It is greatly desired that satellites and space stations stay in stable orbits, because corporations and insurance companies become quite angry if hundred million dollar satellites or expensive space stations with lots of people are gravitationally booted into The Big Dark.

A good first approximation is ensuring that the orbiting object stays inside the parent's Hill Sphere. This is an imaginary sphere centered on the parent planet (the planet or moon the satellite is orbiting). Within the sphere, the planet's gravity dominates any satellites.

For first approximation you have three players: the space station (e.g., Supra-New York), the planet or moon it is orbiting (e.g., Terra), and the object the planet is orbiting (e.g., Sol) otherwise known as the planet's "primary".

The point is that Sol cannot gravitationally capture Supra-New York as long as all of the space station's orbit is inside Terra's Hill Sphere.

You can calculate the approximate radius of a planet's Hill Sphere with the following equation:

r ≈ a * cbrt( m / (3 * M) )


r = Radius of Hill Sphere (kilometers)
a = Distance between the planet and its primary (kilometers)
m = mass of the planet (kilograms)
M = mass of the primary (kilograms)
cbrt(x) = cube root of x (the ∛x key on your calculator)

Actually you can use any desired unit of distance for r and a as long as you use the same for both. The same goes for units of mass for m and M.

This equation assumes that the planet is in a near-circular orbit. If it has some weird eccentric orbit the Hill Sphere link has the more complicated equation. The above equation also assumes that the mass of the station or sattelite is miniscule compared to the object it is orbiting. It further assumes that the mass of the primary is quite a bit bigger than the mass of the planet.

In practice, for long term stability, the station should not orbit its planet further than one-half the Hill sphere radius. No further than one-third the Hill sphere radius if you are ultra-cautious.


What is the Hill sphere radius of Terra?

In this case, the planet is Terra, the primary is Sol, the mass of Terra (m) is 5.97×1024 kg, the mass of Sol (M) is 1.99×1030 kg, the distance between Terra and Sol (a) is 149.6 million kilometers (149,600,000 km).

r ≈ a * cubrt( m / (3 * M) )
r ≈ 149,600,000 * cubrt( 5.97×1024 / (3 * 1.99×1030) )
r ≈ 149,600,000 * cubrt( 5.97×1024 / 5.97×1030 )
r ≈ 149,600,000 * cubrt( 0.000001 )
r ≈ 149,600,000 * 0.01
r ≈ 1,496,000 kilometers

So the ultimate Hill sphere radius is 1.496 million kilometers from Terra's center. Luna is at 0.384 million kilometers, safely inside the Hill sphere. The implication is that all of Terra's stable satellites have an orbital period of less than seven months. Supra-New York would do well to stay inside.

The long term stable radius is 0.748 million kilometers from Terra's center (1/2 Hill sphere). The ultra-cautious radius is 0.499 million kilometers (1/3 Hill sphere).

If you were interested in Lunar satellites, the planet would be Luna, the primary would be Terra, and a would be the distance between Terra and Luna.

Any object (like a spaceship) which enters a planet's Hill sphere but does not have enough energy to escape, will tend to start orbiting the planet. The surface of the Hill sphere is sometimes called the "zero-velocity surface" for complicated reasons.

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.

Space Station Problems

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Air Is Not Free

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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. Spaceguard 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."

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 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.

Space Outpost

By "Space Outpost" I mean a space station whose purpose is more like as a remote base for military, corporation, exploration or scientifc observation purposes; and less as a space colony or infrastructure for an inhabited planet. A base located far away from the civilized parts of the solar system or galaxy, in other words.


If a base or space station has 12 crew or less they can manage to get their tasks done without any need for people to oversee activities and and providing for smooth operations and the well-being of everybody. But above that population oversight rapidly becomes vital. If this is more a space colony than a base, the limit is closer to 150 (Dunbar's number)

NASA technical memorandum TM X-53989 Fifty-man space base population organization has some suggestions. This is a 1970 study about how to organize a scientific research space station around Terra with a crew of fifty.


In general, people behave differently as members of a group than they do as individuals. Members of a group relate to each other in many ways — friendly, indifferent, or hostile. If a group is unstructured, that is, without a leader, these different attitudes can build up and ultimately either make the group ineffective or destroy it. If a group is or becomes structured, then it can become a closely formed organism by resolving negative attitudes and reinforcing positive ones, thus becoming an effective team.

Group Size

Experience in numerous organizations and with a great variety of teams has shown that group coherence requires a certain optimum group size. Large groups, such as 50 people, are generally unable to function as a closed entity because communication problems between members are too great. As a result, subgrouping occurs. A small group, such as three to five people, also suffers under insufficient bases for communication; as a result pairing occurs. The optimum size of an effective group lies between 7 and 12 individuals.

Group Relations

A structured group of people in confinement (prison, submarine, exploration team, Space Base) can quickly develop the following important characteristics of a good team, as long as the number of people is within the optimum size range:

1. Unquestioning acceptance of themselves and others.
2. Natural behavior.
3. Problem centering; feeling of responsibility, duty, or obligation.
4. Aloofness and calm; independent judgement.
5. Autonomy — Independence of the physical and social environment.
6. Interpersonal Relations — Tendency to be patient with everyone of suitable character, regardless of class , education, political belief , race, or color.
7. Creativeness, originality, inventiveness.

It is concluded that a 50-man Space Base population needs to be structured into subgroups of nearly optimum size, and that an overall social., structure should be established in order to provide for the well-being and efficient performance of the Space Base population.

To their surprise, the study authors found that with the space outpost organization there were no similiarities with either strictly military-discipline-oriented crew operations or with civilian science-administration-oriented institutions. So they had to make a mix of military-type discipline and a free scientifically oriented organization.

They divided the crew into three groups:

Base Command and Management

The Base Commander has full authority on all matters concerning the Base, its operations and the scientific planning. The two Deputy Commanders have full authority within their respective areas of operations and science; they are in full command if representing the Commander. The four Directors have full authority and responsibility in their areas — logistics, communication, maintenance, and personnel.

Base Operations Group

Communications, Navigation, and Data Handling personnel report to the Director Communications. Power, Computer, Environmental Control / Life Support (EC/LS), and Maintenance personnel report to the DirectorMaintenance, Flight Controllers and the Medical Staff report to the Director Logistics.

Science Faculty Group

The Scientific Faculty is under the administration of the Deputy Commander Science.

Shift Operations

The Base Command and Management Group and the Base Operations Group work three shifts, continuously rotating responsibilities within these two groups.

I. First Shift — This is the main "day" shift. The Commander and his four Directors are on duty. One each of the Base Operations Group will be on duty. One each (but two earth resources) of the Scientific Faculty will be on duty. A total of 21 persons are on "day" shift.

2. Second Shift — The Deputy distribution. Commander Operations is in command. The number two men from Base Operations will be on duty. (The computer man does duty on power. ) The number two men from Scientific Faculty will be on duty (but numbers three and four of earth resources ). Seventeen persons form Shift Two.

3. Third Shift — The Deputy Commander Science is in command. The Base Operations Group is represented by four specialized maintenance personnel as follows: one — communication; one — navigation; one — data and power; and one — EC/LS. The Science Faculty is represented by their number three men (numbers five and six of earth resources), with no biomedical and physics. There are 12 persons on the third shift.

This provides the necessary safety and functional readiness of the Base. The Scientific Faculty's tour of duty will depend on its specific program, earth or sky visibilities , observation times, etc.

In general, there should be one common day of rest for all, with only critical systems being monitored, but without specific internal operations or any external flight operations. The day of rest has the following personnel and their alternates on duty for a three-shift tour of duty: commander; one — communication; one — power; one — EC/LS; and one — navigation.


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 OLS

This is North American Rockwell's 1971 study for an Orbital Lunar Station. The data is from a report Orbiting Lunar Station (OLS) Phase A Feasibility and Definition Study, Vol. V.

The OLS was an eight man space station in Lunar polar orbit. The various componets would be boosted into orbit on Saturn INT-21 boosters and moved into Lunar orbit with resusable nuclear shuttles.

The False Steps blog explained why the concept sank without a trace.


What happened to make it fail: Like the rest of the Integrated Program Plan (IPP) with which it was associated (with the partial exception of the Space Shuttle) the OLS ran into the avalanche that was the early 1970s. As well as major budget cuts and indifference on the part of the government and the American public toward space ventures, it had the additional problem of no high-level advocate. NASA administrator Tom Paine in particular was critical of the “stations everywhere” approach and preferred Wernher von Braun‘s more audacious Mars mission. There it would be only a minor part, if it existed at all.

The core module had six decks, but only decks 1 through 4 were pressurized. Pressurized decks were connected by openings at deck centers (on the core module's long axis). Openings have a diameter of 0.9 meters. Opening between deck 2 and 3 can be closed by a pressure hatch.

Among other things the OLS would serve as a staging area for space tugs equipped with Lunar Landing kits.

Deck two contains the anti-radiation storm cellar. It is designed to protect the crew for up to three days in the event of a solar proton storm. The goal is to keep the crew radiation dosage below 0.4 Sieverts. Given a solar proton storm with a probability of 2 sigmas, the shielding will have to be 16.6 gm/cm2. Since the basic station structure gives a "free" 2.0 gm/cm2, the storm cellar proper will require 14.6 gm/cm2. This can be provided by 14.7 centimeters of water. The shielding will be about 7260 kilograms of water and 900 kg of food.

If station mass is really tight, it is possible to get by with less. The storm cellar shielding will be reduced to only 6.5 gm/cm2, the crew will wear anti-radiation eye shields, and after the mission the crew will permanently grounded (career limit of radiation reached).

As with all storm cellars, it will contain the (backup) control panels, food (backup gallery), and toilet facilities.

During a storm, two crew will be on duty, the rest will spend the time in sleeping bags.

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 Soviet 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.

Sputnik is the reason that schoolchildren in the US have homework.

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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