Subterranean Cities

No one will be more excited about lunar settlement than architects. The Moon will free them from many of the constraints of design and construction on Earth. Most notably, gravity is one-sixth that of the home planet but materials are just as strong, which will allow imagineers to erect buildings with extraordinary architectural features. In addition, the Moon is more geologically stable, subject only to minor moonquakes. No need to worry about shaky foundations. In theory, Lunar habitations could be taller, lighter, airier, even phantasmagorical. 

But there tremendous drawbacks to lunar construction that could doom architects to bitter disappointment. One is the ever-present threat of radiation. All buildings must be heavily screened to block solar rays. The other is the ever-present threat of meteorites and micrometeorites. Walls, roofs, and windows will have to be constructed to withstand rocks hurtling through space at incredible velocities. Any penetration of a building would be doubly catastrophic if it leads to the loss of valuable, life-sustaining air. By necessity, surface buildings either will be buried in regolith or be embedded with massively redundant systems to make them safely habitable.

Surface cities

The first primitive habitations on the Moon will be surface-based, using modules transported from Earth. The next iteration of housing will use materials found on the Moon lunar surface, possibly fusing the material in the regolith into bricks. Protection from radiation and meteorites will be achieved by covering the structure with rocks and regolith. Habitation modules will be connected by tubes. It will be impossible to build large urban clusters this way, however. If the Moon is to accommodate significant population, it will be necessary to evolve new urban forms.

In “Dust Mites,” I describe two cities — Federal City and Mare Nubium — as they might be configured on the lunar surface. They are organized around pods, or cells, of 10,000 or so inhabitants. These self-contained neighborhoods are roofed with structural steel and covered by several feet of rock and regolith to protect against radiation and meteors. The outside walls have heavy, reinforced glass walls to permit views of the Moon outside. Each pod contains a mix of multi-story apartments, ground-level retail, and places of business — what urban planners on Earth might refer to as medium-density, mixed-use development. The streets are designed for walkability, and the pods are connected by rail. Division into self-sealing cells is critical to safeguard the city against loss of air supply and systemwide failure in the event a major breach in a wall occurs. Unlike the Earth, there is minimal green space — perhaps a handful of gardens, pocket parks and individual trees. Three classes of materials — cinderblocks derived from regolith, steel forged from abundant iron and titanium, and glass refined from the regolith — will provide the basis for construction. Wood will be a luxury item imported from Earth, far too expensive to use as a building material. Because glass, glass fiber and energy will be abundant, I expect that mature lunar settlements will make creative use of lights and digital displays.

Crater-based development

The colonies in “Dust Mites” are centered in craters, not the open maria, or “seas.” I anticipate two reasons for a crater-based pattern of development. First, colonists will locate where resources are most readily available to be extracted. Initially, this will be in the south polar regions where ice particles have been accumulating for hundreds of millions of years. Water, comprised of oxygen and hydrogen, will be one of the most precious resources on the Moon. Not only will it provide the fuel for next-generation rocketships, they are critical constituents of organic life. Early settlers extracting this ice will build “mining camps,” and cities will rise around them. Other settlements will exploit deposits of metals and other elements left by the meteors that formed the craters.

A second reason is for security. As the dynamics of great-power competition extends to the Moon, colonists will begin thinking about how to make their settlements defensible against occupation or destruction by hostile powers. Just as Medieval Europeans built castles and villages on defensible hilltops, so will Loonies build inside craters. Crater rims rise above the surrounding lunar plains by several hundred feet, creating natural fortifications. The escarpments on the inside of the rims can rise thousands of feet from the crater floor. Enemies descending into the crater will be exposed and vulnerable to fire from entrenched defenders below.

Underground, 3-D cities

Cities will move underground for all the reasons described above: protection against radiation, massive meteor strikes, and foreign invasion. If craters are defensible, cities burrowed under 200 or 300 feet of rock will be even more defensible and less vulnerable to catastrophic breaches. But the biggest driver of the move underground will be the discovery that three-dimensional cities are a fantastically efficient urban form.

One of the great challenges facing urban planners on Earth is accommodating the need for transportation, especially as cities grow in population and geographic expanse. The most efficient (and typically the most enjoyable) are neighborhoods that are highly walkable. But people are willing to spend only so much time walking between destinations — typically 15 to 20 minutes. If it takes longer, they are inclined to drive or take mass transit. Building these transportation systems consumes an enormous percentage of the urban space and considerable expense to operate and maintain. But a three-dimensional city enabled by 1/6th Earth gravity creates the potential to create urban centers in which people can reach destinations on multiple levels — akin to a cruise ship by availing themselves of stairs and elevators — above and below them.

“Dust Mites” takes place in Galileo Station, a three-dimensional underground city with four levels, or “decks,” as they’re called in the novel. The nuclear plant that powers the colony is located deep underground. Pollution-generating heavy industry is relegated to the lunar surface, while all other activities are located underground and movement between the city and the surface is enabled by the means of airlocks. Streets facilitate the flow of vehicles as well as pedestrians, whose speed is augmented by people-mover conveyer belts.