Introduction

When most people think of worlds, they think of big balls of rock 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 might be locked in a perpetual ice age. But these are only worlds as nature has made 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 artificial worlds are collectively known as megastructures.

A megastructure is the ultimate setting for science fiction adventures. This article will cover creating, introducing, and using megastructures in science fiction campaigns, as well as give examples of such artifacts from various sources.

Basics

Before delving into specifics, we first have to cover some generalities that apply to all megastructures.

Definition

Basically, a megastructure is any single artifact that challenges human preconceptions of size, usually (but not always) constructed by technologically advanced civilizations. A terrestrial city is not 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.

Construction

Building even one of the "smaller" megastructures is an enormous undertaking. Megastructures require vast amounts of materials, capital, manpower, energy, and logistic planning to construct.

In campaigns that use realistic or near-realistic technology (Traveller or Shatterzone, for example), the ability to produce megastructures is rather limited. Individual nations, megacorps, or extravagantly wealthy individuals could produce the more modest kinds (O'Neil colonies', hollowed asteroids), but anything larger has to be the work of a significant portion of the entire civilization; no individual entity could have the resources or the research facilities to go it alone.

This in turn presents a further complication is it possible for the disparate elements in your campaign world to work together for something as resource -- consuming as a megastructure? Political infighting and maneuvering, intrigue, and sabotage by rival factions could greatly complicate an already complex undertaking.

Realistic technology also limits the kinds of megastructures possible to the smaller ones, like space elevators, orbitvilles, and O'Neil colonies. Anything larger is beyond the capabilities of known science, and more or less educated conjecture.

In campaigns with very advanced or fantastic technology (Star Trek, GURPS Uplift, or, appropriately enough, Chaosium's old Ringworld RPG), the field is more wide open. Though none of the civilizations in the settings mentioned above have produced significant megastructures (the Ringworld was a found arLLfact), they certainly have the technological capability to do so. Star Trek and Uplift especially, who both have large, resource-rich, and extremely stable political entities. The creation of smaller megastructures are probably routine and taken for granted. Entire-civilization projects are limited to the simpler of the large megastructures, like mech planets or gossamer spheres.

The creation of the largest megastructures can only be accomplished by using what would seem to us to be god-like or magical technology. Because of this, it is best that these (or any megastructure beyond your campaign civilizations' technical capabilities) are used as found artifacts. Intrepid explorers may stumble onto a Dyson Sphere, ringworld, or godwheel in unexplored space, created by some unknown or long-vanished super-race.

Rationale

Not all megastructures are created equal. No culture will spend the enormous resources and time constructing one. without very good reason. However, the reason for construction will vary from race to race and circumstance to circumstance.

One of the most compelling reasons may simply be living space. In game universes where interstellar travel is rare, difficult, or non-existent, most races will be forever trapped within their own star system. Unless draconian measures of control are used, burgeoning growth will eventually out-strip 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 areas of a ringworld or a dyson sphere, say, the problem could be circumvented.

Another rationale might be economic. A space elevator would make orbital travel as cheap as riding a surface train. O'Neil colonies could be sold to lessdeveloped races for various projects. A dyson sphere could be used to trap all energy output from a star, providing a near-unlimited power source. However, in some cases advances in technology might render the megastructure obsolete; cheap anti-gravity technology would undermine a space elevator, and advanced antimatter powerplants could possibly outstrip even the output of a sun if enough were put into operation.

In some cases, as in Niven's Ringworld and Malibu Comics' Godwheel, the larger inegastructures are used as enormous life 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. In campaigns with limited interstellar travel, this might be the only way for large numbers of species to interact with one another.

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

As many of the larger structures are likely to be found objects, the exact reason for their existence need not be revealed to your PCs right away, if ever. The makers are, after all, mysterious and long-vanished (or so everyone thinks), and their motives may remain unfathomable.

Impact

The existence of megastructures, whether constructed or found by your game's civilizations, will have far-reaching implications for your campaign. They will inevitably become centers for researchers, builders, colonists, curiosity seekers and fortunehunters from all over explored space. Many will become centers for civilization. They will almost certainly draw the jealous eye - and perhaps military might - of any neighboring power who will want the wealth, prestige, and potential of the structure for themselves.

Found artifacts, especially, will create profound and long lasting legacies, especially psychologically. These structures will be very dramatic proof that a vastly superior race exists somewhere out there in the universe, and may provoke intense culture-shock, paranoia, or outright fear among the general population.

Adventuring

A party's visit to a inegastructure should always be a significant event in a campaign. These are, after all, cosmic-scale artifacts, and the GM should do his best to convey the enormity of them. The potential for scenarios are as near,limitless as the structures themselves. The existence of a found structure will spark political intrigue and even wars as competing powers will do everything they can to lay claim to it. Construction of a structure may be opposed by fanatical factions, and sabotage may be perpetrated. Newly discovered megastructures will have to be explored, and the inhabitants contacted. The longvanished building race may be quested for, but if still extant they may not want to be found. Some spaceborne disaster, natural or otherwise, may threaten the megastructure and the billions who live there. New or mysterious technologies used for construction may have tremendous impact on interstellar society, A madman may find a way to use the structure to carry out a campaign of terror. A criminal or spy may flee into the vastness of a structure, sparking an epic manhunt. The party may find itself stranded in some remote sector of the structure and have to somehow make their way back to civilization. The only limit is imagination.

What follows are descriptions of individual megastructures. They fall into three general categories: freefloating, planet-centric, and star-centric.

MegaStructures Sci-fi Settings That Challenge the Scale of the Universe

Introduction
Free-Floating Structures
Planet-Centric Structures
Star-Centric Structures
Other Genres