Fun With: SciFi Militaries

[Sea Skimmer]

Isn't that coming true arguably to a certain extent (the increasing amount of people moving to urban areas throuought the world and increasing oil prices giving more incentive for people to move closer to the city core, etc?)

Its true more people are living in urban areas, but they usually aren’t hyper dense like skyscrapers or even just 10 story tall ‘projects’ apartment buildings would be. Many of those urban areas also happen to be some of the worst places to live on earth with horribly inadequate services. We wont be running out of land on earth for devolopments anytime soon either, rule of thumb is we can fit 6 billion people into Texas alone at mere New York City level density.

[Ford Prefect]

Give me a break, the idea that the future of mankind is everyone living in giant space habitats is no more realistic then the 1930s projections that the future of life on earth would be nothing but mega cities and massive skyscrapers in which it would be an honor to live.

If human beings start living off the surface of the Earth, exactly where do you think people are going to live? No celestial body in this soalr system is particularly more suitable to live on compared to a habitat like an O'neill Cylinder, which is essentially able to replicate everything the earth has, albeit it on a much smaller scale. The point becomes moot if you can just zip over to Deneb V, as the OP would suggest, and stumble across a planet which supports your species (on a galactic scale, the prevalence of a world more or less like earth is going to be fairly significant).

However, if you really are stuck in one system, and you do start living off the surface of your home world, you have the choice of inhospitable rocks or you can build a habitat which has the same atmospheric mix and the illusion of the same surface gravity as your home planet.

[Sikon]

Give me a break, the idea that the future of mankind is everyone living in giant space habitats is no more realistic then the 1930s projections that the future of life on earth would be nothing but mega cities and massive skyscrapers in which it would be an honor to live.

The primary basic part of a space habitat is a large metal shell. Once that's created, filled with air, and rotating for artificial gravity, the construction environment for interior furnishing inside is relatively similar to that on earth.

What stands in the way of an advanced space civilization making large metal shells affordably? Materials? Energy? Labor? Consider them one by one.

It's not particularly materials, as spacestations could be made right by a convenient source, using the metal of a nickel-iron asteriod which is almost like a giant block of premade stainless steel ready to be melted or vapor deposited.

Energy? On earth, the multiple order-of-magnitude cost difference between a $100000 house of 1000-ft^2 area and a ~ $1000 giant tent of 1000 ft^2 area is in part due to the difference in sturdiness. Although current solar cells cost on the order of $500 per square meter, a flimsy sheet of aluminum foil can reflect sunlight for nominally as little as under $1 per square meter. Such flimsy reflectors aren't a workable method on earth, but, in the practically perfectly undisturbed environment of space, cheap and flimsy giant sail-like solar reflectors can survive.

Quite literally, on the order of 200 terawatts of concentrated solar power could be obtained with the first million tons of such reflectors alone. For perspective, today's world electricity generation is 2 terawatts.

Labor? Aside from possibilities such as thermal spraying, one manufacturing technique is to use vapor deposition. Such is impractical for large-scale usage on earth where only small expensive chambers of sufficiently high quality vacuum can be built, but the ambient vacuum and zero-g of space is where it shines.

Imagine making a large metal shell not by manual labor of many thousands of laborers welding together little pieces but by starting with a thin form (analogous to a giant balloon in cheapness although not technically such). Onto the interior area, a tiny thickness of metal would deposit per minute but with that adding up as such ran for hundreds of thousands of minutes in a year.

Such a manufacturing method can require few personnel, as part of the NASA 1975 giant spacestation study described:

In physical vapor deposition of metals, most alloy systems show a fall density, fine grained microstructure at a substrate temperature 0.3 times the melting point of the metal (ref. 32). As substrate temperature is increased, the grains become coarser, the yield strength decreases, and ductility increases. Because these properties correspond to those of rolled and annealed sheet, vapor deposited metals have been termed "a true engineering material (ref. 33). [...]

The equipment used in vacuum vapor fabrication can be very lightweight. It handles sunlight, thermal radiation, rarefied vapor, and an aluminum feed rod; forces on it are virtually nonexistent. The greatest mass in the system appears to be the solar furnace mirror area, which is directly proportional to energy consumption. This consumption is, in turn, driven by the efficiency of energy use (thermal radiation to heat of vaporization), efficiency of vapor use (aluminum vaporized to aluminum reaching substrate), and by the total quantity of aluminum deposited.

Ignoring efficiency factors, for a heat of vaporization of l.l X 10^4 J/g, a colony mass of 300 kt, a solar constant of 1.4 kW/m^2, and a fabrication time of I yr, the ideal mirror area is 7.4 X 10^4 m^2. An average flux deviation from perpendicular of 20 degrees probably represents adequate collimation; with proper evaporator design the inefficiency of vapor use should be less than 2.5 (unused vapor is condensed and recycled); even a poor energy efficiency should keep the total inefficiency below a factor of 10. Allowing a full factor of 10, the mirror area is 7.4 X 10^5 m^2 . At 100 g/m^2, this is 0.74 kt.

The remainder of the system includes refractory metal foil boxes for the actual solar furnace evaporation units, plastic film hoods to intercept scattered metal atoms, and a carefully made balloon in the shape of the desired structure. Including these masses, the total system is very likely less than 1.5 kt; if the fabrication time were extended over several years this mass would be less.

Because colony structures have rotational symmetry, the solar furnace evaporation units can cover different areas as the colony rotates beneath their beams. With proper arrangernent, complex shapes and structures can be created, and the direct human labor required for fabrication is very small. [...]

From here

The reality is the same as what really happened since, then, some of these big habitats will be built just like we kept building some skyscrapers, but for the average joe housing is going to remain much the same as it always did.

The natural tendency of most people is to sometimes overestimate change in the near-term but underestimate it in the long-term. The Roman shipbuilders of a couple thousand years ago would surely not have guessed that the world would go from having a few thousand tons of ships (like hundreds or so of ~ 75-ton Quinqueremes, etc.) to having more than 800 million tons total world merchant marine today, an increase of literally at least tens of thousands of times.

With the length of time that structures can last in space compared to earth, a situation where eventually more people lived in space than terrestrially could occur even if the number of space habitats was built up gradually by each century adding some more while still using the giant metal shells of the past century's habitats. Analogously, some 150-year-old cast iron pipes are still used today in places where corrosion has not been bad.

With that said, growth might not be that gradual anyway. For example, that NASA study also estimated that:

12 percent of the maximum population of one such sphere, working for 3 yr could duplicate the habitat. Automation is much better suited to the large scale, repetitious production operations needed for the habitat shell than to the details of interior architecture and landscape design. It seems quite likely, therefore, that the construction of new habitats will become an activity for specialists who supply closed shells, ready for interior finishing, to groups of prospective colonists.

Really, there's vastly more likelihood of the preceding than there is in getting to imagined habitable planets through FTL. Space habitats would be necessary for a number of goals regardless of cost. Besides, nothing fundamentally prevents an advanced space civilization from potentially producing such for less labor per occupant than a $200000 subdivision house today that may cost its owner the equivalent of a half-dozen years of wages.

[Ender]

So, like in The Humanist Inheritance, all permanent space colonies should be autocracies due to the fact they are hydraulic states?

That's quite a leap in logic you made there. He just said that space colonies were hydraulic states, which is true. How you went from that to accusing him of advocating autocracy is beyond me.

One can reasonably assume that a space colony, while it may or may not be autocratic (just as any country may or may not be autocratic) will invoke many trends of the panticopia or the nanny state. How much these policies will intrude on the life of the citizens will depend on their implementation. Really we can't say much at all about what system of government will be used. I do think a safe assumption is that as a culture, space stations will host a population that has precious little tolerance for those who think it is better to hang separately then to hang together.

Really? Spend much time on space habitats?

Do you take pride in being ignorant or something?

A plane can decompress in about 1 second flat and its not even being exposed to hard vacuum, a huge number of people would easily die from even a very small leak. Its going to decompress everything inside of the surrounding and hopefully air tight bulkheads before anyone can react. Anyone in that space is dead unless the leak is sealed and the area is depressurized in less then 2 minutes.

So despite the fact the equations were helpfully provided 9 hours ago, you decide to run with a no math fallacy rather than consider that things might go differently then you insist they will.

Never mind the threat of things like solar flares or major a

Yeah, we have this stuff called water that you need plenty of to support life. Makes pretty good shielding. Never mind using metals or rock.

So what, the earth is huge with plentiful materials too, that doesn’t mean building stuff is free. Building stuff in space cannot help but be more expensive then building on a planetary surface. You need way more complex systems to provide life support and safety backups and its just going to be inherently harder to do work.

Are you seriously contending that it will be harder to work in free fall, given the proper equipment, than it is to build a skyscraper (where you still need dedicated equipment)?

Right so that’s why everyone on earth already lives on a 6000 square foot apartment right? And huge apartment block projects in US inner cities worked out so damn well? Because all we need is space and materials? Give me a break, the idea that the future of mankind is everyone living in giant space habitats is no more realistic then the 1930s projections that the future of life on earth would be nothing but mega cities and massive skyscrapers in which it would be an honor to live. The reality is the same as what really happened since, then, some of these big habitats will be built just like we kept building some skyscrapers, but for the average joe housing is going to remain much the same as it always did.

Our population is currently expanding at a rate of 0.3% a year. Estimates I've seen peg the earth at being able to support 10^10 of us with its resources. Where are all the people going to live if the Earth can't provide for them? And if you are going to seriously contend that it is more realistic that people will voluntarily restrict the population growth rather then implement technology we've had since the 70's to expand towards space, let me start laughing in your face now.

Speaking of threats of living somewhere, let me quote part of a message I just got in the yahoo sfconsim-l mailing list:

How do I join this group?

[Commander 598]

I think you should keep in mind that birth/death rates aren't exactly the same across the globe and that if population growth is stabilized it won't make the general effects of overpopulation on the Earth any lighter. Resources are still going to be gobbled up at an unhealthy rate and we're already having issues with deforestation and pollution.

[Junghalli]

It's worth noting that global carrying capacity is very much a function of technology. Pre-modern technology could probably never have supported our current population. Likewise new technology may permit more people to be supported more sustainably in the future. A relatively cheap and clean energy source which isn't likely to run out anytime soon (like mature fusion) would go a long way to making human civilization more sustainable. Advancing technology could permit resources to be exploited that weren't economical to exploit before, and allow more people to be fed with less land. These are exactly the trends that led to the relative prosperity of modern First World civilization, and I doubt we've reached the end of the road with them yet.

My own feeling is that by the time we have the technology to send millions of people out into space we'll probably also have the technology to sustainably support a population of ten billion. Indeed, it's worth noting that the same technologies and techniques that allow you to support huge populations in space could probably be applied to supporting large numbers of people on Earth. Keeping lots of people alive in a space habitat is a matter of making highly efficient use of a relatively limited amount of land and biomass, after all.

[Sea Skimmer]

[ So despite the fact the equations were helpfully provided 9 hours ago, you decide to run with a no math fallacy rather than consider that things might go differently then you insist they will.

Actually the math you speak of does not address the issue of how great the local drop in pressure will be. That’s going to depend a great deal on just how the habitat is designed, the more open the better, but huge open spaces are their own engineering challenge.

Yeah, we have this stuff called water that you need plenty of to support life. Makes pretty good shielding. Never mind using metals or rock.

Its still more trouble for builders then having an atmosphere do the job for free. Now if planets with without thick atmospheres and solid useable ground are extremely uncommon then I’d see space habitats making a lot more sense, but looking in just the solar system I can’t see how we’d ever run out of places to build.

]Are you seriously contending that it will be harder to work in free fall, given the proper equipment, than it is to build a skyscraper (where you still need dedicated equipment)?

Are astronauts on space walks assembling the ISS more productive then high steel workers? I really doubt it. Simply being in a pressure suit makes working a lot more cumbersome on its own. I guess it will depend on the number of cost of available robots, but if we can build stuff in space with them, we can do it on the ground too. I guess once we have robot factories building robot factories conventional economics may cease to matter… build enough robots and the process could become totally self sustaining if given enough time.

Anyway, my whole point was we DON’T build skyscrapers because we actually need the space or they make much economic sense; we build them as prestige projects for companies and nations. This is why even in the densest cities most people by are in buildings only a few stories tall.

Our population is currently expanding at a rate of 0.3% a year. Estimates I've seen peg the earth at being able to support 10^10 of us with its resources.

Population growth is likely to slow in as the world become more developed, notice that among industrialization nations only a handful have growing populations and many have begun shrinking. The US isn’t likely to grow forever either, and no one would ever pay for third world breed like rabbit populations to live in space
,

Where are all the people going to live if the Earth can't provide for them?

Given a resource shortage we can import more resources, just like we’ll have to do that for a space habitat already now wont we? The initial assumption was after all that being stuck in a gravity well was no longer a major hurdle, so surely landing the resources won’t be a big deal either. Whatever you can do in the space habitat to recycle and conserve resources can also be applied to surface installations.

Anyway if we truly ran out of space I’d start building on Mars or some of the gas giant’s moons, right on top of other diverse sources of resources. Space is great for providing iron and nickel if you drag an asteroid up to some kind of space blast furnace, but how much other stuff are we going to find in asteroids? I honestly don’t know

I’ve never said we won’t develop space, just that I don’t see whole populations shifting up. If we ran out of space on a planet, then sure, start building spae habitaits if the moon is unpopular, but why abandon the planet?

And if you are going to seriously contend that it is more realistic that people will voluntarily restrict the population growth rather then implement technology we've had since the 70's to expand towards space, let me start laughing in your face now.

People already do voluntarily restrict population growth, because they can’t afford to pay or more kids or don’t want too. That’s why places like Russia and Japan are now shrinking. In the long term sure populations will go up, but if its restricts people don’t like then they sure wont like all the laws and regulations you’ll need for a space city either.

[Sikon]

Space habitats can be almost anywhere, including probably initially in convenient earth orbit nearby NEO asteroids towed there, before likely later more migration to the asteroid belt further out. In contrast, the main choices outside of space habitats are just the Moon or Mars, aside from the distant moons of the gas giants. With the exception of earth's moon, all of them take more travel time and more delta-v than going to earth orbit or to a NEO, especially so in the case of gas giant moons.

Earth's moon was formed from blasted-out ejecta when an object hit the proto-earth billions of years ago, with it having a shortage of volatiles like water ice left. There possibly may be some ice left from cometary impacts in the shadowed rims of some polar craters, but, aside from its existence still being uncertain, it would tend to be too limited to suffice for more than early colonies, not a huge number compared to mankind's population.

In contrast, NEOs or NECs include a number of undifferentiated objects which have never been subject to excessive heating since the formation of the solar system and have water ice, oil (kerogen) hydrocarbons, nitrogen amines, etc. Other bodies from the fractured cores of what once were larger, previously melted, differentiated asteroids can be different, being lumps of nickle-iron metal including some platinum-group metals that on earth mostly sank to earth's core. Other objects are good sources of aluminum, titanium, and magnesium in oxide form ... and so on. Such NEOs and later the asteroid belt can provide resources for space habitats.

It's possible in principle to support a large population on the Moon by shipping in volatiles from elsewhere, but the Moon being relatively resource poor is not in its favor.

While too thin at under 1% of earth's atmospheric pressure to prevent the need for habitation to be in pressure shells or to provide sufficient radiation shielding (requiring local habitats to be buried under dirt in event of prolonged stays), the Martian atmosphere is still far more than enough to rule out large-scale usage of manufacturing methods possible in space like vapor deposition, as convenient manufacture of semiconductors including solar cells, etc.

A huge disadvantage of the Moon or Mars is they are limited in exploitation of one of space's greatest resources, solar power. Although rotating in a manner presenting the same hemisphere to earth, the Moon's rotation means surface solar power would be in darkness for 2 week long lunar nights while temperatures plummet to as low as -200 degrees Celsius. Unlike space, local gravity prohibits construction of truly gigantic cheap flimsy solar reflectors.

None of this prevents some exploration and some colonies on the Moon and Mars, fascinating places to visit, but their overall potential is comparatively limited. For large numbers of people off-earth, space is a better location, like the NASA study concluded for colonies of 10000+ people each:

At first glance the Moon's surface seems a good choice, but any part of that surface receives the full force of the Sun's radiation only a small fraction of the time. Moreover, on the Moon there is no choice of gravity; it is one-sixth that of Earth and can only be increased with difficulty and never reduced. Space offers both full sunshine and zero gravity or any other value of simulated gravity one might choose to generate. An additional difficulty with a lunar location is related to the major product of the colonies, SSPS's. Transporting them from the Moon to geosynchronous orbit is not economically viable. For ease of exploitation of the properties of space, the habitat should be located in free space.

From here

Low gravity like the 1/6 g of the Moon or 1/3 g of Mars is not a problem for temporary visiting astronauts, but it is quite an issue if considering permanent residents spending their lives off-earth. Over a period of a number of years, either bone and muscle mass loss would continue to disaster, or, maybe, it might stabilize eventually but at a level likely making the colonists unable to ever walk on earth or in 1g gravity again.*

* The exception is that might potentially be countered if the moon or Mars-dwellers spent part of each day in centrifuges, but such could be a nuisance at least. Depending on the society, it is rather uncertain whether most of the local public would really do that with consistent discipline year after year, considering how few people on earth exercise much regularly.

In contrast, rotating space habitats a kilometer or more in dimension can easily have full 1g gravity, unlike the Moon or Mars. With variable artificial gravity as desired, they would also have low-g and microgravity areas for recreation (like human flight fun) and other purposes. Little interior construction is likely to be done in spacesuits but rather primarily in shirtsleeve environments (created once a large metal shell subsequently filled with air is formed primarily as one piece by a means such as vapor deposition). An easy system would be to have city residential zoning where all apartments had to be in the 1g section, to guarantee that everyone spent some time daily in 1g gravity.

[Sikon]

With the exception of earth's moon, all of them take more travel time and more delta-v than going to earth orbit or to a NEO

should be

With the exception of earth's moon, all of them take much more travel time and more delta-v than going to earth orbit or to a NEO

... since, of course, even going to the moon still takes a little more delta-v than earth orbit, especially including the braking deacceleration.

Early habitats would probably have the bulk of the immigrants just going from earth to orbit in a trip of minutes to hours, while only a handful of personnel would spend months on a longer trip towing a NEO (or a chunk of one) to earth orbit.

[Darth Smiley]

Back to the original topic, the organization of a military is dependent on political concerns as well.

As an example, if each planet in our hypothetical federation has a single government, than there might be no federal army except as a fairly small cadre of very well trained and equipped troops (or drones, whatever) more analogous to marines than a real army. Planetary defense might be handled entire by local troops, with their own structure dependent on local culture and terrain, especially if space transport is fairly long or difficult. The space forces, on the other hand, would be much more centrally controlled, and much bigger, relatively speaking, with almost all mobile units falling under the control of the federal military.

On the other hand, a star empire might have very real concerns about insurrection among its "member" planets, and consequently have a large, centralized army ready to stamp out insurgencies and rebellion, and heavily controlled from the capital.

[Commander 598]

That’s going to depend a great deal on just how the habitat is designed, the more open the better, but huge open spaces are their own engineering challenge.

Island 3: