Moon Miners' Manifesto

#11 December 1987

SPACE OASES Part 1

By Peter Kokh

Part 1: FIRST LOCATIONS

"SPACE OASES" as used in this article are defined as durable free space structures providing:

1. artificial gravity through centrifugal force,
2. a closed life support system for air, water, and at least some food,
3. shielding against long term exposure to solar and cosmic radiation and micrometeorites, and
4. habitation for at least a transient community of people.

This is a more generous definition than "space colony" or "space settlement" which is conceived of as supporting a non-transient population of a size large enough ( minimum 10,000? ) to enjoy a respectable measure of self-sufficiency. The assumption is that smaller and cheaper space oases will pave the way.

Where in free space are we likely to find such oases for human life? Certainly in stable low Earth orbits ( 500km - 1000 km ) where they will support manufacturing and processing, tourist, convention, education, and hospital functions. But for most of us, these close-in possibilities only whet the appetite for real breakout. Even geosynchronous orbit ( 37,500 km ) does not deeply stir our space pioneering spirits.

The original space colony scenario outlined by Princeton physicist Gerard K. O'Neill proposed a semi-stable area which trails the Moon in its orbit some 60 degrees ( about 5 days ) behind in a sort of lockstep formation. Known as the fifth Lagrangian spot, or "L5", this location remains equidistant from the Earth and the Moon and is not difficult to reach. However, it is not as stable as once thought owing to perturbations by the Sun. It has since been found that a two week period highly elliptical orbit which would precess rather swiftly under the Moon's dominant influence, the so-called 2:1 resonant orbit, would not only be more stable, but easier to reach from both the Moon and the Earth. "L5" remains important as a Moon-synchronous location for communications relays, and as part of a long astrometric baseline together with "L4", but is otherwise a historical curiosity, good material for a trivia question.

A whole archipelago of space colonies at L5 was called for in a grand design to rescue an energy-starved Earth from a bottomless oil crisis. Unfortunately, there has been a very temporary respite in that crisis, but it was enough to squelch all political interest in this country which has raised short-term planning to the level of an art. Interest in solar power satellites, the anticipated principal export of these space colonies, remains strong in the U.S.S.R and Japan.

Meanwhile, a second energy gambit to a future space-anchored economy, mining lunar Helium-3 ( 600 times as abundant on the Moon as on Earth ) to fuel a very clean form of nuclear fusion plant that would essentially emit no neutrons, is under serious study at the University of Wisconsin in Madison. Both scenarios require a permanent return to the Moon, but the export tonnage in the newer scheme is far less. Yet a third possibility awaiting further dev elopment in high temperature superconductivity is a girdle of Moon-sited solar power stations linked by superconducting cable so that solar energy could be beamed by way of relay satellites to all parts of Earth at all times of the month. Neither of these newer energy schemes would drive substantial development of space colonies, settlements, or "oases". But any plan which calls for integration of the Moon into the economy of Earth will need at least some space-based manufacturing. Space oases will be built.

Once lunar resources form the major portions of oases' import tonnage ( not only raw materials but necessary provisions, etc. as well ) -- say 90% to 95% or more -- it will be far more logical to site them in low lunar orbit ( LLO ). Since it is far cheaper to build and maintain equal habitation on the lunar surface where everything is at hand and exposure to radiation is halved ( the lunar surface blocks half the sky ), these manufacturing and construction camp oases will be occupied principally by production workers on tours of duty from their homes on the Moon where their families remain. Since only production personnel are involved, and since what will be essentially dormitory space with condensed recreation facilities can be provided in significantly greater density, the productivity of such LLO oases per ton of structural mass should exceed that anticipated of the classical L5 colony by an order of magnitude ( 10 ) or better, making it far more economically viable. Since these workers would be adjusted to one-sixth Earth-normal gravity on the Moon, their construction camp oases would provide the same level. This is another enormous advantage since, given the supposed maximum spin rate of 1 rpm to avoid serious Coriolis problems, the lower gravity facility can be built with a proportionately reduced radius and would be subject to proportionately reduced structural stress. From LLO, finished products, even very large structures, could be sent on their way to destinations closer to Earth, just as easily and cheaply ( if not more so ) as the bulk raw materials from which they would be constructed. Nor is alleged reduced access to sunlight in LLO a real problem. Even at the equator, the boost available from lunar rotation is only nine miles an hour ( compared to 1,000 MPH on Earth ) so that positioning and launching to and from LLO oases in sun-synchronous lunar polar orbits along the terminator is no problem at all. Around the clock sunlight will be available except during eclipses which equally affect L5 and other proposed sites. And higher lunar orbits would provide the same solar access at lesser inclinations.

If Earth-Moon tourism ever develops volume sufficient for it, a cycling cruise oasis or transitel ( transit hotel ) would allow first-class travelers to spend at least the major portion of their journey in comparative comfort and luxury. At each end, short and cramped shuttle trips would probably always be their lot. A more elaborate and specially equipped transitel might someday allow emigrants to Mars a more tolerable sojourn. Such a transitel would not be a grand resort but probably provide on board education for the settlers about Mars and the technologies needed to render life possible there, and even assembly bays where they could assemble equipment that had been put aboard as parts to be used on Mars.

So much for the siting of space oases. Perhaps someday, space colonies in the now classical sense will be built, and the economic needs that drive their construction will determine where they are located. This we cannot now foresee clearly. - PK

Contents of this issue of Moon Miners' Manifesto