## Introduction

While the prior page was more about colonization motivation and methods, this page is more about good planets, hell-hole planets, scouting good planets, and changing hell-hole planets into good planets.

## Galactic Neighborhood

First off, galactic empires tend to be spherical. This is because they generally start from a point (the homeworld) and expand in all directions like blowing up a balloon.

Which means they are subject to a sort of cube law. This means if the radius of an empire expands a teeny-tiny bit, the volume of the empire will expand lots and lots. Specifically if the radius doubles the volume will increase about eight times (23). This is because the equation for a volume of a sphere is 4/3 πr3, but the dramatic increase in volume is not obvious by just eye-balling the equation.

If you are mapping your empire, you will need to figure some sizes. If you decide upon the empire's radius and want to know how many stars and stars with Terran-type planets, use the rules of thumb:

Nstars = Rly^3 * 0.01

NhStars = Rly^3 * 0.0022

where

• Rly = empire radius in light years
• Nstars = number of stars
• NhStars = number of stars with human habitable planets

If you decide upon the number of stars in the empire and want to know it's radius:

Rly = cubeRoot(Nstars * 97)

Rly = cubeRoot(NhStars * 464)

(If your calculator does not have a cube root button, you can use the "Xy" button instead. Type in the number, hit Xy, type in 0.333333333 then hit the equal button.)

Note: the above equations are based upon the work of Jill Tarter and Margaret Turnbull. They were not trying to figure out which stars could host a human habitable planet. They were trying to figure out which stars could host a planet that was not so hideously uninhabitable that no possible form of life could live there. In other words, many of these planets could host alien life forms but would quickly kill an unprotected human being. The equations were derived by me using an analysis of the Habcat database, and thus could be wildly inaccurate. If you can find better figures, use them, but these are better than no figures at all.

If my slide rule isn't lying to me, this works out to an average distance between adjacent stars of 9.2 light years, and an average distance of 15.4 light years between adjacent habitable stars.

## Galactic Survey

This section has been moved here.

## Colonizable Worlds

If your first-in scouts have given you the luxury of lots of human-habitable worlds to choose your colony sites from, naturally you will pick the ones closest to being paradise planets.

If you are really outta luck and all the planets range from miserable hell-holes to utterly uninhabitable you have roughly five options:

Which option you chose will depend upon just how badly do you want to have colonies. If you just want some show-planets so you can claim you have an honest to Asimov interstellar empire, well, there are cheaper ways to get some status. However if the Blortch Hegemony has decided to exterminate the human race lock, stock, and laser emitter; well, you might have no choice but to ensure that our species does not have all its eggs in one basket.

### Hostile Planets

If one is dealing with near-future colonization of the non-shirtsleeve planets of the solar system using weak chemical rockets, the difficulties are overwhelming. It is vastly easier to colonize hypothetical human-habitable garden worlds around other stars using handwaving faster than light starships (because the author said so).

The sad fact of the matter is that it is about a thousand times cheaper to colonize Antarctica than it is to colonize Mars. Antarctica has plentiful water and breathable air, Mars does not. True, the temperature of Mars does occasionally grow warmer than Antarctica, but at its coldest Mars can get 50° C colder than Antarctica. In comparison to Mars, Antarctica is a garden spot.

Yet there is no Antarctican land-rush. One would suspect that there is no Martian land-rush either, except among a few who find the concept to be romantic.

#### Dome Colony

As a general rule colonists like places with breathable atmospheres, so they don't immediately die upon stepping out of the transport spacecraft. Unfortunately, if there are no starships, the only naturally occurring place like that in the solar system is Terra. Everywhere else is a non-shirtsleeve environment, the colonists will have to build and maintain a large pressurized volume to live in.

This might be a purpose-build operation that is part of a grand plan to colonize the place. Or it might be unplanned, usually by some organization establishing some kind of base; then as other bases and boomtowns spring up nearby, the entire establishment morphs into a colony. As previously mentioned: the main difference between a base and a colony is that the members of a colony do not expect to ever leave.

Functionally a colony on an airless world is a space habitat that is sited on the ground instead of floating in orbit. Structurally they will be different. A ground based colony will have access to lots of local resources that a space colony will have to import. In other words: a space colony will probably be constructed out of metal shipped in, while a ground colony will be a series of underground tunnels.

Why? Because radiation from galactic cosmic rays (GCR) and solar proton storms is not healthy for children and other living things. It heinously expensive to ship radiation shielding to a space habitat under construction, but planet-based naturally-occurring lava tubes are practically free.

Planets with no atmospheres will need to build underground for radiation protection. Not counting Terra, Venus and the Gas Giants, the only planets with appreciable atmospheres are Mars and Titan. The Mars Radiation Environment Experiment discovered that the pathetic Martian atmosphere would let through enough radiation to expose the colonists to 73 milliGrays per year (mGy/a, where "a" {per annum} = 8760 hours = 365 days). On Terra people suffer about 0.4 mGy/a from GCR, and close to zero from proton storms. Translation: the Martian atmosphere is not going to do diddly-squat to protect the colonists from deadly radiation sleeting from the sky, so you'd best build the colony underground anyway. Or pile lots of Martian dirt on top of the buildings. Titan got lucky, it actually has a denser atmosphere than Terra.

Old illustrations of lunar colonies liked to depict them under transparent domes, because the artist did not know about the radiation hazard.

Since all the living spaces have to be pressurized and otherwise equipped with life support, they will be limited and the colony will feel cramped. Much the same as any underground building or rabbit burrow. Cubicles will be minuscule, and the connecting corridors will be narrow. If the colony is lucky enough to have the luxury of connecting corridors. Since pressurized volume is at a premium the cubicles may wind up doing double duty as corridors, with the associated loss of privacy.

#### Terraforming

Terraforming is using planetary engineering to make a planet's environment more like a prime vacation spot on Terra, or a least one where an unprotected human being won't instantly die.

It generally takes hundreds to thousands of years for the process to be complete. It also requires access to incredibly large amounts of advanced technology, planetary-sized stocks of raw materials, and an energy budget comparable to all of Terra combined.

Martyn J. Fogg wrote the definitive book on the topic, sadly out of print. His web page has lots of terraforming information.

In some science fiction colonists on Mars want to make the planet shirt-sleeve habitable. However, the martian colonists commonly chafe under the heavy-handed rule of Terra or have recently concluded a bitter revolutionary war of independence. So patriotic martians are loath to use the term Terraforming. Instead they'll use a term like "habitablization" or something planet-neutral like that. Such a term will also be needed if Terra's climate changes such that it is no longer habitable.

Technically, when aliens try to transform a planet's environment into something that their species finds comfortable, the proper term is Xenoforming. Which is a kind of parochial term, but being more specific brings the same mess as apohelion, apohermion, apogee, aposelene, apoareion, apojove, and apochron. Astronomers soon gave up and adopted the generic term apsis.

Xenoforming or Terraforming a world inhabited by sentient beings is considered to be attempted genocide, biological warfare, or at the least very rude. Extreme moralists go to the point of only allowing terraforming on planets that are totally lifeless. Examples include Sir Arthur C. Clarke's The Songs of Distant Earth, Star Trek: The Wrath of Khan, and sort of in Roger Zelazny's "The Keys to December". Examples of terraforming used as biological warfare can be found at the above link.

##### Transplant Ecosystem

Colonists are going to want to grow local food they can eat, the native plants and animals can be unsuitable as food in so very many ways. Since plants and animals depend upon a circle of life, terraformers will have to transplant a minimal but viable Terran ecosystem that is self-sustaining. And try to avoid importing anything that is a threat to said ecosystem, such as potato blight. Just on general principles you want to avoid a monoculture to prevent a repeat of the potato famine.

And of course also import useful things that are not food, such as Bamboo.

There are some science fiction novels where aliens invade not by full-blown terraforming but simply by introducing alien hyper-invasive species to alienoform the Terran ecosystem (the functional equivalent of introducing xenomorph-bunnyrabbits to Australia).

#### Pantropy

If changing an entire planet to suit human colonists is out of the question, the next best thing is changing the colonists to fit the planet (much cheaper as well). This is done by extreme genetic engineering, James Blish coined the term "pantropy". This can go beyond humans engineered to handle slightly hotter or colder temperatures: it can theoretically lead to engineering "people" with totally different biochemistries, breathing methane and having bones composed of water ice.

This appears in James Blish's Pantropy series, Roger Zelazny's "The Keys to December ", Charles Sheffield's Proteus in the Underworld and Olaf Stapedon's Last and First Men.

Understand this is not taking a person and giving them a treatment to transform their bodies into something that can breath methane and survive sub-sub-zero cold. This is about genetically engineering their as yet unborn children. You take a person's germ cells into the lab, and genetically engineering the living daylights of the the cells so they will grow into a child that can breath methane and survive sub-sub-zero cold. Maybe someday Mommy and Daddy can wear a space suit and visit their offspring, happily walking around in their shirt-sleeves on a planet that would instantly kill an unprotected standard human being.

There are a few older science fiction story about transforming a standard human into something else for purposes of colonizing an inhospitable world, but nowadays that seems far fetched. In The Impossible World they have the miracle drug "adaptene". In Farthest Star they have teleportation by duplication. But the duplicate can be "edited" e.g., a water breather can be transformed into a air breather. And in Enchanted Village I guess the astronaut can adapt into a life form suitable for the Martian villiage because the village is, well, enchanted.

### Space Colony

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

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

It sounds very utopian, and it is.

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

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

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

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

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

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

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

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

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

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

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

#### Space Colony Problems

##### Air Is Not Free

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

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

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

##### Lurkers

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

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

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

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

##### Society Rules

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

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

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

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

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

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

##### Three Generation Rule

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

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

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

##### Death by Civil Unrest

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

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

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

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

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

##### Technological Decline

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

If an asteroid civilization falls into barbarism, everybody dies.

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

#### Asteroid Bubble

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

### But It Probably Won't Work

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

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

But it gets worse:

#### Tensegrity

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

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

Compression members push, while tension members pull.

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

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

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

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

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

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

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

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

## Boom Town

A "gold" strike in an asteroid belt, a large industrial operation, 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 for entrepreneurs to sell them whiskey, prostitutes, gambling, tattoo parlors, and other hard to find luxuries at inflated prices.

Not to mention simple supplies and tools, also at inflated prices. 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 or to stabilize part of the ground to make an impromptu landing field. For an amusing look at the development and economy of a boomtown watch the movie Paint Your Wagon. Then simply transpose the situation from the North American frontier into the asteroid belt.

But remember that boomtowns can wither away into ghost towns overnight, if mineral strike dries up or the military base is closed. This is called a "bust".

## Ghost Town

A ghost town is the abandoned skeletal remains of a space or planetary station that was formerly a boomtown. This happens when whatever money source that was fueling the boom dries up. The boom has gone bust.

### Example: Depot into Story Plot

For the science fiction author writing about a solar system future, things like orbital propellant depots might be more than just the background of the story. With a little effort, they can help a bit with the plot as well. A good way to start is to remember "everything old is new again", that is, find a historical analogy and set it in the science fiction future. Keeping in mind that current events are "historical" as far as the future is concerned. Here is an example:

This is an article from Medium.com magazine, about how self-driving trucks are going to decimate the economies of small towns in suddenly non-strategic locations.

To transpose this situation into one's science fiction future, you have to look for analogies. Cargo spacecraft are obviously trucks, orbital propellant depots are gas stations. The positioning of the depots is like Route 66, optimized for the spacecraft and destinations. The small towns are boomtowns that grew up around the depots, maybe even growing into orbital colonies.

Then we transpose the historical events:

1. Orbital propellant depots are established so as to allow cheap chemical rockets access to transport goods too and from points in the inner solar system. This is the network of automobile gasoline stations on Route 66.

2. boomtowns spring up to relieve spacecraft crews of accumulated flight pay burning a hole in their pockets.

3. The boom-towns grow into Star-Towns, maybe even becoming a full orbital colony. The gas stations on Route 66 have become small towns.

4. Now some disruptive technology throws a monkey wrench into the works.
Historically it was the network change of switching from Route 66 to the national highway system, bypassing the gas station towns.
Currently it is the self-driving trucks that need less gasoline, and certainly do not need sleeping motels, restaurants, or brothels.
In our science fiction future, the network can be changed by, say Beams-R-Us setting up routes for cheap laser thermal rockets. The self-driving trucks are similar to the advent of nuclear rockets (requiring less propellant) or unmanned rockets (requiring no sleeping, fancy food, or prostitutes).

5. Deprived of their revenue stream, the boom-towns and orbital habitats start dying, becoming ghost towns like Glenrio, Texas.

Such an emotionally-charged situation can drive a science fiction story plot.

The locals are going to be very angry at whoever invented the disruptive technology which doomed their town. An employee of Beams-R-Us who is stupid enough to visit such a dying boom-town is likely to get beat up in some dark corridor, maybe even suffer a tragic air-lock "accident."

Hot-heads living in the town might be tempted to stage something drastic in order to draw media attention to their plight. Terrorist actions are easy when one has access to so many concentrated forms of energy.

On the street, it is "rats deserting a sinking ship" time. Desperate individuals will do almost anything to board a spacecraft bound for someplace better. On the other hand, squatters with nowhere else to go will move into abandoned habitats.

The local government will be frantic to find a new revenue stream. If they cannot find a legal one, the solar system underworld has lots of illegal ones.

And of course there will be a few stubborn crazy-coot old-timers who refuse to leave, haunting the empty modules.

In my effort to transpose the situation, I had to play fast and lose with some inconvenient particulars. Master Artist William Black's pointed out a few items I swept under the rug. But the point is the technique of finding analogies allowing one to transpose a past or current situation into the future. Try reading a few historical or current news items with this in mind and see what you can come up with.

## Solar System Colonization

This section has been moved here.

### Mercury

This section has been moved here.

### Venus

This section has been moved here.

#### Sol-Venus Lagrange Points

This section has been moved here.

### Cis-Lunar Space

#### Terra Orbit

This section has been moved here.

##### Terra-Luna Lagrange Points

This section has been moved here.

#### Luna

This section has been moved here.

#### Near-Terra Asteroids

This section has been moved here.

### Sol-Terra Lagrange Points

This section has been moved here.

### Mars

This section has been moved here.

### Sol-Mars Lagrange Points

This section has been moved here.

### Asteroid Belt

This section has been moved here.

#### Ceres

This section has been moved here.

### Jovian System

This section has been moved here.

#### Sol-Jupiter Lagrange Points

This section has been moved here.

### Saturnian System

This section has been moved here.

#### Titan

This section has been moved here.

### Uranian and Neptunian Moons

This section has been moved here.

#### Neptune Trojans

This section has been moved here.

### Trans-Neptuian Objects

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## Interstellar Colonization

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## Atomic Rockets notices

This week's featured addition is MONOCLE FIGHTER

This week's featured addition is GASEOUS CORE SPACECRAFT