On Colonization

A post at SFConsim-l leads me to revisit a trope I have commented about here before. Space colonization, as imagined in SF and 'nonfiction' space speculation, is - surprise! - a riff on the English colonization of America, an experience shared by Clarke and Heinlein, albeit from different perspectives. Historically sort of colonization was driven first and foremost by cheap land.

This should be no surprise, any more than the American colonial analogy itself. It is like hydraulics. Provide a cheaper place to live and people will drift toward it, sometimes even flood toward it.

And the heart of the nutshell, as Heinlein once put it, is that there is no cheap land in space because there is no land at all. Land doesn't just mean a solid planetary surface (those are dirt cheap). Land means habitat, and in space the only way to have any is to build it youself. Which makes it expensive, especially since you have to build it up front.

Water can be pumped uphill, and people can be pulled toward expensive places to live by compensating attractions, or pushed there by pressures. But it is not a 'natural' process, and it can easily be reversed, hence ghost towns in rugged, played-out mining regions.

The sort of colonization envisioned in the rocketpunk era, most explicitly in books like Farmer in the Sky, but implicit in the consensus future history of the genre, is just plain unlikely, almost desperately unlikely, this side of the remote future or the Singularity, whichever comes first.


This is not the only possible sort of colonization. People have traveled afar, often spending their adult lives in some remote clime with no intention to settle there, marry, and raise a family, hoping instead to make their fortune and return home. The ones who don't make their fortune may end up staying, but that was not the plan.

Political colonialism often follows this pattern. The British colonized India, but I've never heard that any significant number of Britons settled there. (Human nature being what it is they did leave an Anglo-Indian population behind.)

A similar pattern has been common for trading outposts through the ages, whenever travel times have been prolonged. Even today, with one day global travel, people live abroad for years or even decades as expatriates, not emigrants. This, I believe, is a far more plausible scenario for the long term human presence in space than classic colonization. (And human nature being what it is, a mixed population will leave someone behind.)


Meta to this discussion - and not all that meta - is the delicate cohabitation of 'nonfiction' space speculation and science fiction. Space colonization has been driven first and foremost by story logic. For a broad range of story possibilities we want settings with a broad range of human experience. For this we want complete human communities, which means colonization in something like the classic SF sense.

But who are we trying to kid? Science fiction, particularly hard SF, is not known for engaging the whole range of human experience. This is no knock on it; all the branches of Romance are selective. The truth is that we want space colonies so that they can rebel against Earth, form an Empire, and generally play out History with a capital H, with lots of explosions and other cool stuff along the way.

I've suggested before on this blog that you can, in fact, get quite a lot of History without classical colonies. But another thing to keep in mind is that story logic doesn't necessarily drive real history. We may have an active spacefaring future that involves practically none of the story tropes of the rocketpunk era.

As a loose analogy, robotic diving on shipwrecks has done away with all those old underwater story tropes about divers trapped in a collapsing wreck, or bad guys cutting the air hose, but it has not at all done away with the somber magic of shipwrecks themselves, something the makers of 'Titanic' used to effect.


On the other hand, Hollywood has made two popular and critically acclaimed historical period pieces about actual space travel, and the stories are both an awful lot like rocketpunk.


Related posts: A Solar System for This Century.

Cold and Dry

This seems to be the current forecast for the Moon's polar craters, as it presumably has been for the last few billion years, and will continue to be for the next few billion.

Not much (only one heavily processed image) has come out officially from the L-CROSS team since their mission scored a lunar bull's eye, minus the photogenic plume that was supposed to be the media highlight of the show. But in the grand old aerospace industry tradition of using Aviation Leak to get the story out, the L-CROSS team dropped some hints in the online Sky & Telescope about what is going on behind the scenes.

The impact did produce a plume, but it was about 10 times less massive than expected. Why it was so sparse is not yet known and may never be fully known, but new hypervelocity impact modeling suggests that debris may have gone more 'out' than 'up.'

There's also mention of the Centaur booster stage 'collapsed into itself when it hit.' I am not quite sure what to make of that last part. You'd expect any tank structure to 'collapse into itself' when it slams into the Moon at 1.5 km/s. But fans of kinetic weapons, including me, take note: There is a lot that we do not know about uber-fast impacts.

As for what was in the faint plume, Sky & Telescope gives contradictory hints, noting that the IR signature of water vapor is conspicuous (and implicitly absent), but also broadly hinting that when an L-CROSS public announcement comes, in a couple of weeks, the team may reveal that it did detect water. But not, I suspect, very much of it. What they did detect, rather oddly, is mercury.

The article also has one other interesting tidbit, though not from L-CROSS. Apparently an instrument aboard the Lunar Reconnaissance Orbiter determined that the surface temperature on the floor of those permanently shadowed are only about 35 K - much lower than anticipated, and making those spots the coldest known place in the entire Solar System.

And right in our local 'hood. How cool is that?

Spaceship Design 102: Life Support

Human life support is complicated, bulky, and it smells bad. If we only sent robots we would not have to mess with it. But if we go in person we have to deal with it. First, go to the life support page at Atomic Rockets.

To begin with we will need a cabin. Here there is a big difference between short missions, up to a day or two, and longer ones. Short term passengers can sit in airliner style seats, crew at their work stations, and the galley needn't be much more than a refrigerator and microwave oven. But as missions get longer you need bunk space for off duty crew, and at some point cabins or bunkrooms and a real galley.

From a comparison of railroad sleeping cars versus coaches, sleeping accommodations take up about 10 cubic meters per person, 2-4 times as much room as airliner style seating. Add a galley and dining compartment, storage space, and some this and that brings the minimum requirement to around 15 cubic meters per person, give or take.

(The ISS is much roomier, Wikipedia claiming a 'living volume' of 358 cubic meters for a crew of six, or nearly 60 m3 per person. But I don't know how living volume is defined, for example whether it includes working spaces. Total pressurized volume of the ISS is reported as about 1000 m3.)


Man does not live by bread alone, but along with water and oxygen it is a start. Human beings need about 5 kg/day in food, water, and oxygen, food accounting for about half the total. Unless you have regenerative life support you will need to carry it all with you. This does have the advantage of simplicity - we know how to do it, which is not the case for regenerative life support. For missions up to a few months the mass penalty is not excessive; 200 days' provisions and supplies come to about a ton per person, requiring about 3 cubic meters of storage space.

With storerooms, equipment bays, and assorted plumbing, our hab compartment for deep space transports may thus have a volume around 20 cubic meters per person. This in turn equates to about a ton or two per person for the basic hab pressure vessel, plus another ton or two of fittings and equipment, and for a 6 month mission a ton of consumables. So, altogether, each person (passenger or crew) carried by a transport class ship accounts for 3-5 tons of payload capacity.

In the rocketpunk era the standard way to reduce this was to carry passengers in Cold Sleep. But at our current level of knowledge this is magitech. We haven't a clue how to drastically slow down human metabolism, or even produce mere hibernation, let alone how to do it safely.


Another rocketpunk era classic was regenerative life support, those famous hydroponics tanks somewhere aft/below decks. Details were sometimes vivid, occasionally charming (fresh flowers in the wardroom of PRS Aes Triplex), rarely quantitative.

There is a rule of thumb that it takes 10 kg of food source biomass to support 1 kg of whatever is eating it: thus, for a purely vegetarian diet, about 0.75 tons of plant biomass per person. Biochemistry conveniently sees to it that the plants we eat also replenish our oxygen.

On this basis the break even point for regenerative life support is about 150 days. A 1953 (!) source cited at Atomic Rockets says 145 days. But this ignores the penalty mass of the hydroponics tanks. (Or aeroponics, whateva.) Greenhouse hydroponics on Earth seems to achieve yields of about 30-35 kg per square meter. One source mentions a 4 month growing season, suggesting that with year round operation we might do three times better, approaching 100 kg/m2.

Since we eat about a ton of food per year, this corresponds to about 10 square meters of growing surface per person. With access and working space perhaps 20 cubic meters per person - comparable, that is, to our estimate for living space, and probably with a comparable mass, about 3-5 tons per person, including a ton or so of biomass.

The structure and equipment mass needed to grow food shifts the tradeoff point: For missions less than about 2 years, the mass of stores plus storeroom capacity is less than the mass of a regenerative system. Most transport class ships - which for this purpose includes most military craft - are used for shorter missions that that, so they will dispense with the extra bulk and mass of full regenerative life support. They might have a garden deck, more for human factors than for its modest life support contribution.

There's also the little detail that we don't yet know how to do regenerative life support. This is one type of space research that can be done on Earth, and as space research goes it does not require a lot of expensive hardware. The Biosphere 2 fiasco doesn't prove a lot in and of itself, given the possible flake factor, but building a human supporting ecohab cannot be easy, or someone would have done it by now.

But we won't really need regenerative life support until we are establishing long term stations or bases. And my guess is that we'll learn the techniques gradually, in the process of reducing dependence on costly supplies from Earth. Regenerative life support is, on some level, a sophisticated form of gardening, and gardening has always called for patience.


Two other life support considerations: Radiation, and heat.

Without shielding, the cosmic radiation dose in deep space is about 400-900 millisieverts per year, where 1 Sievert = 100 old fashioned rems. The current career limit is 4 Sieverts for astronauts, 2 Sieverts and change for nuclear industry workers. Thus for long term habitation we will need enough shielding to diminish the penetrating radiation by about tenfold. This requires about 100 grams per square centimeter - a ton per square meter. And this shielding has to be applied all around, because cosmic rays can come at you from any direction.

This is not a problem for big permanent habs, but it is far too massive for transport class ships. This is one more reason to favor fast orbits for human travel. A ship's habitat might provide enough shielding to cut radiation by half, so that a 3 month tranfer mission provides about the same radiation exposure as a year living aboard a shielded hab.

And don't forget plain old heat management. An object at room temperature radiates about 400 Watts per square meter, which you will have to replace - but at 1 AU you are also exposed to a solar flux of 1400 W/m2 on surfaces directly facing the Sun. Managing heat, both from onboard power and solar flux, to keep the hab in the human comfort zone will be a constant task.


In fact, all of life support will be a constant task. In rocketpunk days maintaining the life support system was treated as an afterthought to the cool space stuff like astrogation and engineering. This is unlikely to be the case.

This being All Hallows' Eve, I'll just leave you with this thought for your contemplation: Cascading life support malfunction.


Related post: Spaceship Design 101.

History, From Above

This image from Astronomy Picture of the Day - see it here in magnificent full size - gives a whole new meaning to 'overview of history.' Seen from the Shuttle Endeavor, the International Space Station passes above Sicily and heads east over the Ionian Sea, with the instep and heel of the Italian boot seen just to its left.

The Ionian Islands are the group above and to the right of the ISS, just off the coast of Greece. One of them is Odysseus' Ithaca (though it is uncertain whether his home was the same as modern Thiaki). The site of Troy is also hazily visible, straight up from the Ionian Islands about two thirds of the way to the limb of the Earth. The ISS will cover this distance in about 100 seconds, some three million times faster than Odysseus' trip home.

History's three greatest galley battles all took place within this field of view. Salamis (480 BC) is only hazily visible on the Aegean coast of Greece, but Actium (33 BC) was fought just off the lagoon to the left of the Ionian Islands, and Lepanto (1571) in the gulf just behind them.

In fact these waters are the Belgium of Mediterranean naval history: A disproportionate number of seafights have taken place here over the centuries, from Corcyra, the opening round of the Pelopponesian War in 31 BC, to Navarino (1827), the last fleet battle under sail, and Cape Matapan (1941). Also visible here is Taranto, Italy, where the British staged the first successful air raid against an anchored fleet more than a year before Pearl Harbor.

And in the time it has taken you to read this, the ISS will already be far to the east, gliding across the skies above the Silk Road.

Spaceship Design 101

A lot of us would like some system for designing spaceships, at least in outline, for use in games, detailed fictional settings or physical or virtual 3D modeling.

The procedure I have seen most often begin by defining a hull. This gives you the main dimensions of the spacecraft, its surface area and volume capacity, perhaps along with constraints such as maximum load and drive acceleration. This is a natural approach. I used it for my battleship-era warship specification sim, SpringStyle, and it is retained by its independent offspring, SpringSharp.

But for deep space craft it is seriously misleading. Ships and aircraft, says Captain Obvious, move through a fluid medium that shapes and constrains their design. Deep space craft do not. Their overall design constraints are more architectural: supporting the craft against its own thrust, along with stresses from attitude change maneuvers, the thump of docking, thermal flexing, spin loads, and the various other kinds of abuse that spacecraft are subject to.

This is as good a time as any to point you to the Atomic Rockets pages on basic and advanced design.

I will argue that deep space craft have essentially two sections that can largely be treated separately from one another. One section is the propulsion bus - drive engine, reactor if any, solar wings or radiator fins, propellant tankage, and a keel structure to hold it all together. The other is the payload section that it pushes along from world to world.

There are both conceptual and economic reasons to treat them separately. Conceptually, because a propulsion bus might push many different payloads for different missions, such as light payloads on fast orbits versus heavy payloads on slow orbits. A little noticed but important feature of deep space craft is that you cannot overload them. They do not sink, or crash at the end of the runway, or even bottom out their suspension. They merely perform more sluggishly, with reduced acceleration and (for a given propellant supply) less delta v.

A very large station or hab might well have a modified ship drive as its main stationkeeping thruster. Or it may rely on a ship coupling to it, as the ISS is shunted by Soyuz craft docked to it.

Conceptual logic is also economic logic. The outfits that build drive buses would like to sell them to lots of different customers for a broad range of assignments.

This is not necessarily an argument for true modular construction, with drive buses hitching up to payloads on an ad hoc basis like big-rig trucks and trailers. Building things to couple and uncouple adds complexity, mass, and cost - plug connectors, docking collars, and so forth. Moreover, drive buses intended for manned ships need to be human-rated, not just with higher safety factors but provision for supplying housekeeping power to the hab, etc. But these things, along with differing sizes or number of propellant tanks, and so forth, can all be minor variations in a drive bus design family.


The payload we are most interested in is, naturally, us. The main habitat section of a deep space ship closely resembles a space station. It is likely that habs intended for prolonged missions will be spun, for health, efficiency, and all round convenience. (Flush!) The design of a spin hab is dominated by the spin structure and - unless you spin the entire ship - the coupling between the spin and nonspin sections.

Because ships' spin habs have the features of stations they may be used as stations, and again we can imagine design families, with some variants intended for ships and others as orbital platforms having only stationkeeping propulsion. Habs are the one major part of a deep space ship that correspond fairly well to our concept of a hull. Spin habs are entirely different in shape, but the shape is constrained; once you build it you can't easily modify it, beyond adding another complete spin section.


Pause to question another familiar convention here. Since at least Heinlein days spinning ships have typically been given a control room located on the spin axis, and perhaps nonspinning, where the astrogators can use their instruments unhampered. But isn't this equivalent to the circular astrogation slide rule? The navigators will do their normal work on monitors. In the inevitable space emergency there will no doubt be coelostats available, or other workarounds. But there's no reason not to locate the ship's main operating control room in the spin section, closer to the people who work there.

Though I'd be happy to be persuaded otherwise. I have always liked Heinlein's penthouse style control rooms at the forward/top end of the ship (plus the fact that he never called it a bridge). If Hollywood came calling I'd bend realism here in a nanosecond, not least because a 'top' control station is visually easy to understand, a sort of Aha! moment for viewers. But I suspect it is a minor cheat.


For those with bank cards at the ready, buying a deep space ship might be not unlike buying a computer. If your mission needs are fairly standard, you check off options on a menu. Those with more specialized requirements can select major components - perhaps a drive bus from one manufacturer, a main crew hab from another, along with custom payload sections, service bays, and so forth, assembled to your specifications.

In fact, both technology and probable historical development suggest that fabrication and overall assembly will be two distinct phases, carried on in different places, quite unlike either shipyard or aircraft assembly practice. In the early days, large deep space craft will be built the way the ISS was, assembled on orbit out of modules built on Earth and launched as payloads. In time fabrication may move to the Moon, or wherever else, but final assembly (at least of larger craft) will continue to be done at orbital facilities. I call them cageworks, on the assumption that a cage or cradle structure provides handy anchoring points for equipment.


For game or sim purposes, my advice would be to treat drive buses and hab sections as the primary building blocks for ships, whether these components are permanently attached to each other or simply coupled together. Both approaches might be in use.

A couple of provisos. All of the above applies mainly to deep space craft, especially with high specific impulse drives. Ships for landing on airless planets have some similar features. Ships that use rapid aerobraking, however, are aerospace craft and broadly resemble airplanes, even if they never land or even go below orbital speed.

And I have said nothing of warcraft. Kinetics are essentially just another payload. Lasers, and other energy weapons such as coilguns, probably draw power from the drive reactor, calling for some modifications in the drive bus. These things don't much affect the overall configuration. Armor protection would, but discussions here have left me doubtful of its value against either lasers or kinetics. Laser stars and other major warcraft may not be dramatically different in appearance from civil craft of similar size.

Thirty Planets

That is how many new discoveries are being reported at the Extrasolar Planets Encyclopedia website, along with three new brown dwarfs.

I was tipped off by a political blog, which linked to this CNN article. Yes, the article says 32 planets, but I'll go with the Paris Observatory. It may be a matter of updated information, since the observatory site links an email that references 29 plus 1.

No details yet about the newly reported planets - the image above, from the CNN site, seems to show a planet orbiting a double star, but it may just be a generic exoplanet from file footage, so to speak.

But thirty new planets (at least!) have swum into our ken. Wow.


Related posts: The California planet search team reported a haul of 28 planets in 2007.

A Plume After All

As it turns out, the L-CROSS mission did create a visible plume. Neener neener neener, says the Moon and the L-CROSS science team. I saw the news in the Los Angeles Times, dead tree edition, and it is online at Space.com. Apparently the plume was imaged by a camera aboard L-CROSS itself, just not the imagery everyone was watching in real time. Judging from the stark contrast, they had to tweak up the contrast value to see it.

According to Anthony Colaprete, head of the team, the plume brightness was 'at the low end of our predictions.' (Do'h - that's why you didn't give us our show!)

Because I think of ice crystals as being bright, this does not seem positive for water, but that is probably an extremely naive interpretation. Much more to the point, the L-CROSS team evidently got plenty of good data, and over the next few weeks we may start to hear what they are learning from it.