The design concept of the Atrium Habitat derives from Marshal Savage’s notion of the small lunar dome habitat as well as examples of domed buildings in antiquity that employed the dome as a means of expanding the perceived dimensionality of space. In the original TMP, Savage described a lunar ‘homestead’ in the form of a small water shield dome set over a crater whose rim would be excavated into compartments and terraces housing the primary dwellings while the center would be made into a large garden –a prototype of the vast crater domes he envisioned as primary colonies. This parallels the organization of ancient domed temples that employed domes as a kind of false sky creating the impression of a different sacred space or microcosm. Lofting the the dome above the edge of perimeter colonnades, alcoves, and chambers obscures its edge, creating an impression of a horizon far beyond the actual dimensions of the space. This is a key visual trick helping to perceptually expand the dimensions of an indoor space and create the illusion of an ‘indoor outside’ –an atrium space- relative to the more enclosed perimeter spaces.
Such tricks of perception will be key to making subterranean habitats comfortable permanent homes while the dome shape is a very efficient way of maximizing the potential clear-space volume of excavated structures. Thus we envision this same basic form becoming the common form for human occupied excavated habitats; simple domes covered in a light-emitting/diffusing panel system (skysim) creating the appearance of a sky whose perimeter edges are elaborated and obscured by built-up structures and perimeter chambers used as primary dwellings while most of the interior area is relegated to naturalistic garden space. Perimeter structures may range from radial rings of simple vaults and, of course, entrances to linking tunnels to multi-storey terraces as well as artificial rock forms and sculptures intended to compliment the garden space and obscure portions of perimeter structure not needing openings into the garden area. In a few cases, large lakes may be created in these atriums serving as reservoirs or marine biomes, the domes made into a lenticular or spherical form and inadvertently creating even closer analogs to the Marine colonies of Aquarius.
The dome lighting panel system, or ‘skysim’, would be a key focus of engineering for these habitats, since they would need to provide not only a comfortable diffuse light in a healthy spectrum for humans and plants, but also provide it with a light modular component system that appears seamless from a distance, be highly energy efficient, integrate electric lighting with natural light piped from heliostats on the surface, and provide some effects, like clouds and star fields, to help enhance the illusion of a sky. These lighting systems may eventually become sophisticated enough to be used as graphic displays, allowing public information or status displays for habitat systems to be projected on the sky dome in clever ways. Laser pointers might even allow the smaller ones to be used as interactive computer displays. And in some cases residents may employ spherical surface cameras to allow them to project a live exterior view. Much work on this may already have been accomplished with the development of EvoHab orbital settlements that would employ a similar lighting system as part of their light-transmitting hull structures.
This basic form would be used for habitat chambers of many sizes, with the low gravity of the Moon and Mars allowing some of these domes to be kilometers in diameter. Such large chambers would support quite elaborate landscaping in their open area, allowing for Aquarian-style tectonic terrace complexes in their centers merging with landscape and simulated rock outcroppings. In addition, this same approach can be employed with arch-vaulted tunnels, producing broad and sometimes meandering garden avenues flanked by town-house-like buildings. These areas may have a more urban aspect and serve as hubs for long distance transit. Grid vaulted structures, just as employed for the telerobotic stage of settlement, would continue to be employed for industrial facilities and intensive automated farming.
Linked complexes of these atrium habitats would employ a fractal arrangement, sometimes dictated by the nature of the strata they are excavated from, with larger chambers serving as community centers and smaller chambers as neighborhood centers and finally personal dwellings. PRT systems would parallel the layout, providing automated transportation for humans and machines throughout the colony and often employing tunnels on separate levels. Early colonies would rely more on communal chambers where many modest perimeter dwellings share a common atrium. But with these structures built and maintained increasingly by automation, the creation of large personal chambers is likely. Though these colonies may always have something of an urban aspect, personal or family ‘homestead’ chambers may eventually become quite vast –perhaps a kilometer in area. As noted in the Life In Avalon article, the caretaking and aesthetics of atrium garden space will likely become a particular obsession for the Avalon colonists as these gardens would be key to quality of life in space and the personal realization of idealized lifestyles. Because –until the advent of robust in-situ nanofabrication methods- excavated chambers cannot be rebuilt to accommodate future changes –only expanded in size to subsume smaller chambers– great deliberation over expansion of the colony is likely in order to realize the maximum use flexibility over an indefinite period.
On the surface, atrium colonies would be supported by large arrays of radiators, solar collectors, and heliostats. Larger chambers would feature their own dedicated arrays, their heliostats concentrating light into a narrow shaft and light pipe penetrating to the top of the domed chambers and feeding light by fiber optic cable to the sky-like emitter/diffuser panels covering their inner surfaces.
This very simple form of habitat may see use for space colonies long into the future and have its counterparts in many environments. Only with the advent of NanoFoam and the ability to create BioZome habitats would this be supplanted –though, as we will later discuss, even the BioZome would be based on largely similar architecture, only with the addition of a much more adaptive structural matrix.