Islands in Space

In his 1977 publication The High Frontier: Human Colonies in Space, particle physicist Gerard K. O’Neill outlined his vision for the colonization of space in Earth’s orbit. It concluded nearly a decade of intensive research and academic collaboration, resulting in a detailed outline for the colonization of outer space based on the technology of the Apollo and Skylab programs. Although much has transpired to update the technology humanity would employ in its colonization of outer space, Professor O’Neill’s “Island” typology has proved enduring. Jeff Bezos’ Blue Origin is only the latest example of the typology at work on the present day space market, with advances in computing, engineering, and materials manufacturing doing much to clarify many of the questions O’Neill could not answer in 1976, and in the case of his Island-3 design, those advances have only strengthened its viability.

Exterior of Island Three type colony as seen from above the “south end,” illustrating a closer look at the cables connecting the pairs of colonies; these are wide enough to accommodate electromagnetic trains running between the two cylinders. Note large structural supports present within the cylinder, elements which were not present in O’Neill’s original design. Credit: Blue Origin.

In the universe of 2100 CE, a variety of space colonies exist alongside one another, with some becoming obsolete with the passage of time and new ones being constructed to replace them. O’Neill’s general typology is used throughout, with a few basic modifications. What follows is a brief overview of colony types at the outbreak of war between the international Confederation and the Galilean League, 1 Jan 2119:

Island One

Two types –nearly identical but for size — characterize the earliest design of space colony. Engineered to house a population of 10,000, these original colonies were used as test-beds for future endeavors, serving the long-term needs of the construction and support personnel engaged in the construction of larger designs.

Interior of an Island One Bernal sphere demonstrating the reflected sunlight entering via windows surrounding structures at the axis; the bicycle-windglider demonstrates the zero-gravity nature of the colony’s rotational axis, permitting human-powered flight. Credit: NASA Ames Research Center (art by Rick Guidice).

The Bernal sphere design was the most common of the Island-1 type, consisting of a spherical living area rotating about its axis at 2 rotations per minute (rpm). The resulting centrifugal forces produce simulated terrestrial gravity along the sphere’s equator, with steadily declining artificial gravity as one approaches the zero-gravity environment at the colony’s axis. Sunlight is fed to the colony’s interior by way of mirrors which orient the reflected sunlight in through massive windows located on either end of the colony. Although an initial six were ordered, only four of these types of space colony were constructed.

Cutaway view of a Bernal sphere. Illustrated here in gold are the windows through which the distant Sun’s light is reflected from the externally-mounted mirrors. Credit: NASA Ames Research Center (art by Rick Guidice).

At the outbreak of the war, no colonies of the Island-1 design remained in use across the solar system, having been broken up and their parts reused in the construction of later colonies.

Island Two

Interior of a Bernal sphere with a river spanning the colony equator; note the large ring of windows near the axis reflecting sunlight into the interior. Credit: NASA/National Space Society.

An enlarged version of the Bernal sphere design, the Island-2 version proved more economically viable to its smaller cousin. With a spherical diameter of nearly four miles (6,500 meters) to the Island-1 ‘s one (1,600 meters), the colony could theoretically house a maximum population of 40,000. The explosion in space colonization which this spurred quickly pushed the design to its limits, with the colony of Clearwater reaching a population of nearly 60,000 before its annexation by the neighboring Commonwealth of Alba.
Of the twenty Island-2 types which were originally constructed, two were still in use at the outbreak of war, Clearwater at the Earth-Lunar Lagrange point 5 and Mahon, an Island-2 colony converted for use as a military base in Io orbit.

This Bernal sphere colony clearly illustrates the system of mirrors attached to the exterior of the space station, reflecting sunlight to the colony interior. Credit: Ben Margolis.

Island Three

Designed by Gerard K. O’Neill himself, this type of colony has proved the most successful in the expanding humanity’s reach in outer space. The station is designed around a colony of individuals living within an O’Neill cylinder, a hollow artificial construction rotated about its length to simulate full terrestrial gravity along the length of the cylinder. Large-scale zero gravity facilities delineate either end of the cylinder, with the exterior of the south end connecting the cylinder to its petal-like mirrors. These “strips” of mirrors run the length of the colony cylinder, reflecting sunlight into the colony exterior via matching strips of windows on the colony cylinder.

Exterior of paired Island Three type colonies as viewed from their “north end”; note the mirrors connected to the sound ends angled out like petals on a flower. In the foreground, smaller cylinders rotate independently, housing the colony’s agricultural facilities. Credit: NASA Ames Research Center (art by Rick Guidice).

Three windows reflect sunlight down on matching strips of habitable land which run the length of the cylinder interior. Each portion of land is divided into three basic environments: a mountainous region at either end of the colony rising to the cylindrical axis, with large metropolitan areas at the foot of each “mountain”; a piedmont region of rolling hills and suburban neighborhoods; and finally wilderness at the cylindrical center, with some colonies opting for open plains, others for seas and beaches, still others for walls of forest, jungle, or artificial mountains to bisect the colony.

Interior of an Island Three O’Neill cylinder looking from the artificial mountaintop on the colony’s “south end,” nearing the cylindrical axis. In the distance a metropolis extends an artificial bay. Credit: NASA Ames Research Center.

The Island-3 design proved even more efficient than its predecessors, with early versions capable of housing populations of three million being quickly eclipsed by versions capable of supporting populations in the tens of millions. This was helped by the simple mechanics of keeping a rotating cylinder in stable orbit, requiring the coupling of cylinders into binary pairs, effectively doubling the support systems for the combined double-colony. By the outbreak of war, the Island-3 design continued to house the majority of space settlers living within the Terresphere.

Interior of an O’Neill cylinder looking from the mountainous region of the “south end.” Note the structural supports running the length of the colony cylinder and accompanying towers, elements not present in O’Neill’s original design. Credit: Blue Origin.

Island Three/Closed (Island-3C)

A modification of the basic O’Neill design, the O’Neill closed-type eliminates the window panels from the cylinder in exchange for a series of mirrors similar to those of a Bernal sphere or entirely artificial sunlight. A full-scale version would theoretically be capable of housing twice the population of its corresponding “open-type” O’Neill cylinder, although only smaller versions have been constructed.

Interior of a closed-type colony illustrating the disorienting nature of such a design. Note the use of artificial lighting to simulate sunlight running along the cylindrical axis. Credit: NASA/National Space Society.

At the outbreak of the war, these smaller versions of the Island-3C type are common among asteroid mining colonies, where innovations in 3D-printing have allowed the cylinders to be constructed entirely within the confines of an asteroid, providing the colony’s residents with shielding against solar radiation. At the outbreak of war, these colonies typified the mining operations administered by corporations on Ceres and Juno, and were on the whole isolated communities. An engagement fought between the Confederation escort carrier Leopard and separatist warships permanently disabled the use of one such colony in the Gitano mining cluster, resulting in hundreds of deaths and a subsequent reconsideration of this colony type.

Illustration of an unpaired, full-scale Island Three/Closed type colony as viewed from above its “north end,” illustrating the attached semi-torus of agricultural facilities and zero-gravity port facilities at the cylindrical axis. Credit:

Island Three/Extended (Island-3E)

An innovation on the standard O’Neill cylinder, Island-3E lengths the cylinder to the design’s structural limits, fielding a design capable of supporting a population of 70 million, greater than the population of entire nation-states on Earth. Initially merely a proof-of-concept, the population boom which followed the first wave of extraterrestrial settlers turned the design into a reality, coming to replace the Island-3 type outside the confines of the Terresphere.

Exterior view of pairs of Island Three/Extended colonies illustrating the additional cable supports necessary for the over-sized mirrors attached to each space station. Credit: Don Davis.

When the war began, the majority of Island-3E colonies resided in high Martian orbit, with clusters at the Sun-Earth Lagrange points 4 and 5, Delos and Tenedos respectively.

Island Four

A hypothetical design proposed for deep-space colonization. Populations would range in size from 70 to 120 million, intended to be used in reconstituting an entire nation-state with its own government and independent economy. The colonies would be placed in distant orbits at the solar-planetary Lagrange points 4 and 5 of Venus, Earth, Mars, and Jupiter. The design would incorporate heavy radiation shielding through advances in the processing of lunar and asteroidal byproduct.
A prototype was begun by the government of Europa in the years leading up to the war, a portion of which the Confederation assault carrier Santa Monica encountered over Jupiter. This hypothetical design would become an urgent reality for the Confederation at the war’s end.