Nick Nielsen today tackles an issue we’ve often discussed in these pages, the space-based infrastructure many of us assume necessary for deep space exploration. But infrastructures grow in complexity in relation to the demands placed upon them, and a starship would, as Nick notes, be the most complex machine ever constructed by human hands. Are there infrastructure options, including building such vehicles on Earth, and what sort of societies would the choice among them eventually produce? You’ll find more of Nielsen’s writing in his blogs Grand Strategy: The View from Oregon and Grand Strategy Annex. In addition to his continuing work for the space community, Nick is a contributing analyst with strategic consulting firm Wikistrat.
by J. N. Nielsen
Although we have spacecraft in orbit around Earth, as well as on the moon and other planets and their moons, and even spacecraft now in interstellar space, so that the products of human industry are to be found throughout our solar system and beyond, we have as yet no industrial infrastructure off the surface of the Earth, and this is important. I will try to explain how and why this is important, and why it will remain important, potentially shaping the structure of our civilization.
Made on Earth
All our spacecraft to date have been built on Earth where we possess an industrial infrastructure that makes this possible. The International Space Station, of course, was assembled in orbit from components built on the surface of the Earth and boosted into space on rockets. It has long been assumed, if we were to build a very large spacecraft (say, for a journey to Mars or beyond), that it would be constructed in much the same way: the components would be engineered on Earth and assembled in space. There is an obvious terrestrial analogy for this: we build our ships on land, where it is convenient to do the work, and then launch them only when the hull is seaworthy. Once the hull is in the water it is fitted out, and then come sea trials, but it would not be worth the trouble to try to build the hull of a ship in the water.
The analogy, however, seems misleading when applied to space. In space, we could build very large spacecraft in microgravity environments that would considerably ease the task of manipulating awkwardly large and heavy components. Also, large spacecraft never intended to enter into planetary atmospheres could be built in the vacuum of space with no concern for the aerodynamics that are crucial for a craft operating in a planetary atmosphere. The stresses of transiting a planetary atmosphere would be an unnecessary requirement for most deep-space vehicles. But what would it take to really build a spacecraft in space, in contradistinction to the assembly of completed modules in orbit?
Image: One take on building starships in space. This view of the Project Icarus orbital construction ring prototype design shows resupply from the Skylon single stage to orbit spacecraft now under development by Reaction Engines. Credit: Adrian Mann.
Even a “basic machine shop” in orbit would not come close to providing the kind of industrial infrastructure we have been building on the surface of the Earth for more than two hundred years now. Production processes ripple outward until they involve much of the planet’s industrial production capacity, a lesson that can be illustrated by Adam Smith’s famous example of the day-laborer’s woolen coat or by what Austrian economist Eugen Böhm von Bawerk called round-about production processes.  I suspect that many will argue that the advent of 3D printing is going to change everything, and that all you need to do is to boost a 3D printer into orbit and then you can produce anything that you might need in orbit. Well, not quite.
The Growth of Infrastructure
As civilization grows more complex, infrastructure becomes more complex, and more precursors are necessary to achieving the basic functionality assumed by the institutions of society. We see this in the increasing complexity of our cities. There was a time when cutting edge technology meant bringing water into a city with aqueducts and having underground sewers to carry away the waste. To the infrastructure of water supplies we have added fossil fuel supplies, electricity supplies, telecommunications lines, and now fiber optic cables for high speed internet access. (On the growing infrastructure of civilization cf. my post The Computational Infrastructure of Civilization.) All of these infrastructure requirements have been continually updated since their initial installation, so that, for example, the electricity grid is significantly more advanced today than when introduced.
For the lifeway of nomadic foragers, no infrastructure is necessary except for a knowledge of edible plants and available game. Since the geographical expansion of nomadic foragers is slow, change in requisite knowledge is also slow, as a moving band of foragers only very gradually sees the diminution of traditional dietary staples and only very gradually sees the emergence of unfamiliar plants and animals. Much greater infrastructure characterizes agrarian-ecclesiastical civilization, and much greater still industrial-technological civilization. The extraterrestrialization of industrial-technological civilization (yielding extraterrestrial-technological civilization) requires an order of magnitude of increase in infrastructure for the necessary maintenance of human life.
How to Build a Starship
The spacecraft requisite to the achievement of extraterrestrialization are today, and are likely to remain, the most complex and sophisticated machines ever built by human beings. To produce not only their components, but the machines required to produce the components, requires the entire advanced infrastructure that we now possess in our most developed centers of manufacturing. A useful analogy for understanding the industrial requirements for the production of spacecraft is to think of building the spacecraft of the future as we think today of building a nuclear-powered submarine. Like a nuclear submarine, an SSTO (single stage to orbit) spacecraft will be one of the most technically difficult and demanding engineering tasks ever attempted; it will involve parts suppliers from all over the world; it will involve millions of individual parts that each have to fitted in place by a human hand, and the assembly itself is likely to require many years of painstaking construction.
There is another sense in which spacecraft probably will be like nuclear submarines: a spacecraft is going to have significant power demands, and the most compact way to address this with our current technology is what we now do with your biggest submarines: nuclear power. The compact reactors on submarines (and aircraft carriers, which typically have two reactors for redundancy) have proved themselves to be safe and serviceable, and they can keep generating power for 25-30 years without refueling – possibly a sufficient period of time to make an interstellar journey. We can, of course, readily make use of solar power in space, though this is not compact and would not be suitable for a starship, which would be operating for extended periods of time far from the light of the sun or any other star.
I think it is clear that once we attain the ability to produce technologies commensurate to the challenge of a practicable starship, we are likely going to want to employ more than one propulsion technology, so that the drive system is highly hybridized. By “hybridized” I mean two or more forms of propulsion on a single spacecraft, and if these multiple forms of propulsion can share structures of the propulsion system, the more they do so the more truly “hybrid” the propulsion design. We may want to have one drive system for use in planetary atmospheres, another for orbital maneuvering, a third for interplanetary travel, and lastly a drive for interstellar travel. Later that list may need to be lengthened for a drive for intergalactic travel.
Hybrid propulsion systems are already in development, and these innovations could greatly improve the efficiency of chemical rockets. I have written many times about the Skylon spaceplane with its “combined cycle” SABRE engines that operate as conventional jet engines in the atmosphere, and which are able to transition to rocket propulsion for exoatmospheric operation. (Cf., e.g., Skylon spaceplane engine concept achieves key milestone, Key Tests for Skylon Spaceplane Project, Move to Open Sky for Skylon Spaceplace, and Addendum on Jet Propulsion Technology) This is a truly hybrid propulsion system, as the jet engine and chemical rocket share structures of the propulsion system, though it remains within the parameters of chemical rockets.
For faster travel to farther destinations, we will need hybrid propulsion systems of exotic technologies that do not exist today except in theory. A spacecraft with an Alcubierre drive and some basic form of chemical or nuclear or ion thrusters might be able to do the job, and this might well be the first step in building a starship that give us access to the galaxy in the way that we now have access to the surface of Earth. However, a spacecraft with an Alcubierre drive and a fusion or antimatter drive, or with Q-thrusters, would be much better. If, for example, you traveled to our closest cosmic neighbor, Alpha Centauri, you might want to travel the greater part of the distance with the Alcubierre drive, but once you get there you would probably want to make your passage between Proxima Centauri, Alpha Centauri A, and Alpha Centauri B with your fusion or antimatter drive, and you would definitely want to explore the planets of these stars with this “slower” drive. (And you probably wouldn’t want to use something like a Bussard ramjet for transit within a solar system.)
Two Responses to the Infrastructure Problem
A spacecraft mounting the kind of hybridized propulsion systems outlined above would represent an order of magnitude complexity even beyond the example of assembling a nuclear submarine. For the next few decades at least, and perhaps for longer, there will be no machine tools and no industrial plant in space. All the facilities we need to build a large and complex engineering project that is likely to occupy many years of painstaking effort, are earth-bound. Moreover, such technical assembly work would probably need to be performed by skilled craftsmen in a familiar environment conducive to careful and patient work. While there are significant advantages to constructing spacecraft in orbit, as noted above, the world’s most advanced industrial plant and best construction teams are on the earth and will be for some time, so that there remain compelling reasons for continuing to construct spacecraft on Earth, despite being at the bottom of a gravity well. This, in a nutshell, is the infrastructure problem.
There are two obvious responses to the infrastructure problem: (1) we accept the limitations of our industrial plant at face value and organize all space construction efforts around the assumption that spacecraft will be built on Earth, or (2) we begin the long task of constructing an industrial infrastructure off the surface of Earth. This latter approach may take as long as or longer than the building of our industrial infrastructure on Earth. While we have the advantage of higher technology and knowing what it is we want to produce, we also face the disadvantage of the harsh environment of space, and the need to initially boost from the surface of Earth everything not only required for industry, but also everything required for human life.
Almost certainly any human future in space will consist of some compromise between these two approaches, with the compromise tending either toward Earth-based industry or space-based industry. The model of extraterrestrialization that eventually prevails will not only be a matter of socioeconomic choice, but also a function of what is technological possible and what is technologically practicable. This latter requirement is insufficiently appreciated.
The Role of Contingency
The large-scale structure of human civilization, once it expands into space (provided we do not languish in permanent stagnation) will depend upon technological innovations that have not yet happened, and therefore the parameters of which are not yet known. That is to say, humanity as a spacefaring civilization is not indifferent to how we are able to travel in space, and how we are able to travel in space will be a result of the sciences we develop, the technologies that emerge from this science, and which among these technologies prove to be something that can be engineered into a practical vehicle, in terms of extraterrestrial transportation.
Just as we as a species are subject to contingencies related to the climatological conditions that shaped our evolution, the geography that has shaped our civilization, the gravity well of the Earth as a function of its mass that constrained our initial entry into space, and eventually the layout of our solar system as it will shape the initial spacefaring civilization that we can build in the vicinity of our own star, so too we are subject to contingencies that will arise out of our own actions (and inactions). These latter contingencies include the sciences we pursue, the technologies we develop, and the engineering of which we are capable. The human contingencies that determine the structure of our civilization in the future also include unknowns such as exactly which science, technology, and engineering projects get funding (cf. my recent post Why the Future Doesn’t Get Funded).
If it turns out that the science behind the Alcubierre drive concept is sound, and that this science can be the basis of a technology, and this technology can be engineered into a practicable starship, we may never construct an industrial infrastructure in space. It may prove to be easier to construct starships not as massive works slowly assembled in Earth orbit, but rather as relatively compact spacecraft constructed in the convenience of a hangar, which, once finished, can be rolled out onto the tarmac, fired up, and blasted into space, thence to activate its Alcubierre drive once in orbit in order to fly off to other worlds. If, in addition, habitable planets (or planets that can be made habitable) are not too rare in the Milky Way, and human beings prefer to spend their time planetside, the industrialization of space may never occur. In this scenario, space-based industry always remains marginal, even as we become a spacefaring civilization.
As it is, we already today seeing the beginnings of the gradual transition of our industrial infrastructure into something cleaner than the smoke-belching chimneys of the early industrial revolution. As this process continues, and we continue to improve the efficiency of solar cells, there may be little or no economic benefit for moving industry into space. We may pass a threshold, beyond which Earth-based industry can be made entirely benign, therefore obviating the need to move industry into space. But all of this hinges on unknowns of an eminently practical sort, and which we cannot predict until we have actual experience operating the technologies in question.
Space-Based Infrastructure and Planetary-Based Infrastructure
If the Alcubierre drive turns out to be impracticable, or even not practicable at technological levels of development obtainable in the next few hundred years, then the need to construct different kinds of spacecraft will be more pressing. The idea of building a sleek spacecraft in a hangar and blasting off to other worlds directly from Earth’s surface may be impossible. In this case, becoming a spacefaring species, and especially becoming a starfaring species, will likely mean the construction of enormous industrial works off the surface of the Earth, initially assembling large spacecraft in Earth orbit or beyond, but gradually providing more and more goods and services in space without having to boost them all from the ground, which means the industrialization of space.
The industrialization of space, in turn, would mean a very different kind of large-scale spacefaring civilization than a spacefaring civilization that had no need of the industrialization of space, as described in the examples above. A spacefaring civilization of primarily space-based industry would be distinct from a spacefaring civilization of primarily planetary-based industry. Distinct social, political, and economic institutions and imperatives would emerge from these distinct industrial infrastructures.
If, as Marx claimed, ideological superstructures follow from the economic infrastructure that the former emerge to justify,  then it is to be expected that space-based economic infrastructure will produce an ideological superstructure distinct from planetary-based economic infrastructure. In the distant future, when we have occasion to survey many different spacefaring civilizations, this may prove to be a fundamental distinction that divides them.
 At the Icarus Interstellar Starship Congress last year, a member of the audience asked a question of Kelvin Long in which the questioner used the phrase, “the infrastructure problem,” which strikes me as the perfect formulation for the topics I am covering today.
 On Adam Smith’s example of the day-laborer’s woolen coat cf. Smith’s The Wealth of Nations, the final paragraph of Book I, chapter 1; on round-about production processes in the work of Eugen Böhm von Bawerk, cf. Thesis 22 of my book Political Economy of Globalization.
 The locus classicus for this Marxian view is to be found in Marx’s A Contribution to The Critique of Political Economy, translated from the Second German Edition by N. I. Stone, Chicago: Charles H. Kerr & Company, 1911, Author’s Preface, pp. 11-12: “In the social production which men carry on they enter into definite relations that are indispensable and independent of their will, these relations of production correspond to a definite stage of development of their material powers of production. The sum total of these relations of production constitutes the economic structure of society — the real foundation, on which rise legal and political superstructures and to which correspond definite forms of social consciousness. The mode of production in material life determines the general character of social, political, and spiritual processes of life. It is not the consciousness of men that determines their existence, but, on the contrary, their social existence determines their consciousness.” Note that Marx usually refers to the “economic base” of a society rather than to its “economic infrastructure.”