Megastructures

One of my fav NGC programme..

By Paul Lucas

19 February 2007

When most people think of worlds, they think of big balls of rock or gas orbiting a star. Variations usually tend toward strange atmospheres, odd compositions, or exotic native life. One world might have a crimson sky and a dozen moons; another with a vibrant ring system may be locked in a perpetual ice age.

But these are only worlds as nature might make them. Just as mankind has created new, artificial chemical elements, so too is it possible for the human race to eventually create entirely new classes of worlds. Worlds that may stretch around planets or trap the energy output of entire stars. Worlds that may challenge the scale of the universe.

These new worlds are immense artifacts collectively known as megastructures.

This article is an overview of the many types of megastructures that have been featured in science fiction stories over the years. Megastructures are easily one of the most awe-inducing concepts in speculative fiction, and the musings of various creators have given birth to a startling variety of them.

Definition

Basically, a megastructure is defined as any single artifact that challenges human preconceptions of size. A modern city may not be considered a megastructure because it is composed of many smaller buildings. The Great Wall of China, however, could be considered one, because it is a single, unified structure.

Rationale

Megastructures require vast amounts of material, capital, manpower, energy, and logistic planning to construct. Some may take decades, centuries, or even thousands of years to construct. So why bother building one at all?

For some, form follows function. Some feats can't be performed by anything except the very large. Space elevators, for example, need to be tens of thousands of kilometers in length in order to propel cargoes into orbit. In order to trap all of the sun's radiative energy, a structure as large as a Dyson sphere is a necessity. The enormous expenditure of building such structures may be mitigated by the valuable services and resources they can provide.

Another reason to construct one may be as simple as the need for living space. Interstellar travel may turn out to be impractical because of one circumstance or another, meaning we may be forever trapped within our own star system. Unless draconian measures of control are used, burgeoning growth will eventually outstrip the capacity of terrestrial worlds to support their populations. However, if a civilization were to convert all of the material in the system to the job of supporting life, by creating the vast habitable surface area of, say, a Ringworld or Dyson sphere, the problem could be circumvented.
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In some cases, as in Niven's Ringworld and Malibu Comics's Godwheel, larger megastructures may be used as enormous life and cultural laboratories. Specimens from many thousands of worlds can be held and studied in detail on the vast surface of the artifact. Sociological and biological experiments can be conducted on a grand scale without endangering the source stock on distant homeworlds.

A megastructure can also act as a means of preserving or protecting a culture from disasters or outside influence. In the novels Farthest Star and Wall Around a Star by Frederick Pohl and Jack Williamson, a Dyson sphere is used as an intergalactic lifeboat to transport survivors away from an exploding galaxy. On a smaller scale, space-borne O'Neill Colonies could be used as refuges for cultures that wish to retain their ideological "purity" away from outside contact yet still remain self-sufficient.

But perhaps the most significant reason to build a megastructure is to simply prove that one can, to create some lasting and unforgettable monument to the power and ingenuity of its builders.

A number of megastructures, such as space elevators, rotovators, and O'Neill colonies, have already been discussed in detail in previous Strange Horizons articles. Links are provided at the end of this article.

Arcologies

The term "arcology" is a fusion of the words "architecture" and "ecology," first coined by Paolo Soleri in his landmark 1969 book, Arcology: City in the Image of Man. Arcologies have also been incorporated into many science fiction works since, such as the movie Blade Runner and novels like Neuromancer by William Gibson and Oath of Fealty by Larry Niven and Jerry Pournelle.
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Arcologies are envisioned as optimal human urban environments; large, self-enclosed mega-skyscrapers with volumes measured in the cubic kilometers that contain everything a human population could ever need. They would be miniature cities onto themselves, engineered for maximum comfort and efficiency. The structure would not only supply living space but would have its own commercial, industrial, and business districts. A resident would not only live within the structure, but also commute and work and shop all within its enclosed walls. The interior would also be configured with a great many windows, parks, and mirrors to give the illusion of much greater space in individual hallways and chambers.

Because space within the structure is used much more efficiently, an arcology would require only about two percent as much land as a modern city of equivalent population. Actual living space per person would be about the same, but the support structure can be built on a much more efficient three-dimensional scale, and the need for road infrastructure (which can consume as much as sixty percent of the space of modern urban sprawls) would be eliminated altogether. Arcologies of many different configurations have been proposed, many able to hold up to half a million residents or more.

Though arcologies today are seen primarily as an urban development, they can be built for nearly any environment. Cliffside arcologies, farmland arcologies, and even dam arcologies have all been proposed. Many see the development and perfection of Earth-bound arcologies as a necessary first step for engineering livable colonies in the oceans and in space.

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