[A spin-off article from this talk has now been published in print in the British Interplanetary Society’s “Spaceflight” magazine, November 2015, p.432-33.]

Here is a summary of what I said at my British Interplanetary Society presentation “Building Selenopolis” on 5 March 2008.

I had an audience of about 25 people, who seemed satisfied by my talk, if not wildly enthusiastic. Of course 90 minutes is a long time to listen to one person’s voice, even though I had some nice pictures to show them.

I gave each person a summary sheet to take away, listing the key points. The following is an expanded version of that summary, which should give you a good idea of what it was all about.

NASA Deputy Administrator Hans Mark, 1983, predicted a permanent population of 1000 people living on the Moon by the year 2040, drawing an analogy with Antarctica.
Von Braun, 1973, had told Mark that the space station will be the enabling technology that allows regular access to the Moon. It will act as a refuelling terminal, following the early designs of Willy Ley (ca. 1945) and Guido von Pirquet (1928).
The lunar city “Selenopolis” is conceived of as – following Hans Mark – a lunar colony of 1000 residents (plus whatever short-stay visitors such a colony might attract). Starting with NASA’s planned Moon base in 2022, with a population of 4, our concept of Selenopolis can be reached after 30 years of continuous growth in population and supporting infrastructure, if the growth rate is 20% per annum.
The current American manned lunar strategy, Constellation (=Orion-Ares-Altair), copies the architecture of Apollo-Saturn. It does not use any space station as a refuelling terminal. Its high cost of operation and lack of versatility for any use other than government science and technology research make it intrinsically resistant to growth. It seems unlikely that Constellation can support 20% growth over 30 years, and we therefore need to question its basic assumptions.
A growing volume of traffic prompts the evolution of a linear architecture, which connects only two points, into a two-dimensional network, with many branches. A network is the type of transport infrastructure which we use on Earth, in which a number of services cycle between permanent nodes (bus/train stations, airports, seaports).
Space tourism offers better prospects of generating a large volume of space passenger traffic than does government space science. Virgin Galactic has already signed up almost 200 passengers for its spaceflights, even though they will be only the briefest of suborbital hops. There is a public hunger to fly.
A single institution such as government will only create a pillar architecture, but a large-scale economic system naturally forms a pyramid. The pillar is basically: one space station, one Moon base (with or more likely without the space station), one Mars base (with or more likely without the space station and the Moon base). The pyramid by contrast builds up a number of space stations before its first Moon base, then builds up more space stations and more Moon bases before its first Mars base, so at that point you might have 10 people on Mars, 1000 on the Moon and 10,000 in low Earth orbit. Consider the Antarctic analogy: when the first Antarctic bases were founded in the 1950s, they could call upon a vast global transport infrastructure.
The radiation threat from solar storms creates a fundamental design problem for lunar passenger transport. Its solution is an architecture based on Earth-Moon cycler stations. Once the massive radiation shielding has been placed into an Earth-Moon transfer orbit, it can stay there indefinitely.
The need for rocket propellants in space is another fundamental design problem. Its long-term solution requires the mining of water from near-Earth asteroids. This part of the argument rests on the well-known work of Professor John S. Lewis of the University of Arizona.
A 40-year asteroid mining scenario is sketched, during which a cumulative total of 50,000 tonnes of water is delivered to Earth orbit for sale. (This is my own attempt to reproduce Lewis’s reasoning, adapted to my own purposes.)
Asteroidal water has two important large-scale uses in orbit: for making rocket propellants, and in its raw state as radiation shielding, thus increasing its attractiveness. It can be marketed to government science programmes, commercial microgravity research and manufacturing projects, space tourism companies and space-based solar power companies.
By around 2050, a lunar colony of 1000 residents – Selenopolis – will be possible if it represents only a small fraction of total manned space activity by that time. But if it is conceived as a one-off project in splendid isolation from any supporting space economy, its continuing reliance upon public funding will make it unlikely that it will survive for long, even if it is started.
We are therefore no longer talking about flying a mission to the Moon, but about stimulating a growth-oriented economic system. The impetus to create this system is coming and presumably will continue to come from entrepreneurs, not from the established space agencies.
Economic access to Mars – building Areopolis – requires the same basic principles: permanent cycler spacecraft, asteroidal water mining, and the prior growth of a large supporting space infrastructure. Most of the mass of our Earth-Mars transport system – rocket propellants, radiation shielding and water for life-support systems – is already in interplanetary space, in orbits very similar to those we need.
Systematic industrial use of the near-Earth asteroids opens up the possibilities of large-scale space construction using the resources of the main belt, which are 10,000 times greater. This mass of material, combined with the almost inexhaustible flux of solar power, offers the material basis for a 21st-century space industrial revolution analogous to the 18th-century one, with analogous transforming possibilities for the whole of human society.

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