## 5 ## A Tour of the Colony
During the final stages of construction of the habitat, colonists begin immigrating to L5. Within a few years a small but thriving human community is established. Its architecture, agriculture, commerce, culture, and even the individual people reflect a dedicated emphasis on productivity.
Imagine that you are a visitor on a tour of this colony. Your experiences during such a visit are shown in italics in this chapter to act as counterpoints to the continuing technical descriptions which conform with the arrangement of the other material in this report.
EARTH TO LOW EARTH ORBIT
Preparation for your trip is a difficult period; it eliminates those who are not serious about their intention of going to the space colony. You undergo weeks of quarantine, exhaustive physical examinations, stringent decontamination, and interminable tests to make sure that you do not carry insects, bacteria, fungi, or mental problems to L5. Only then are you permitted to board a personnel module of a heavy-lift launch vehicle which everyone refers to as the HLLV, along with 99 prospective colonists who have gone through even more rigorous tests than you have as a mere visitor.
In the following hour events move at breakneck speed. Your vehicle is launched. Acceleration thrusts you into your contoured seat. Minutes later it ceases and you are in orbit 240 km above the Earth and having your first experience of being weightless. The orbit is a staging area at which an entire section of the HLLV, the personnel carrier containing you and the colonists, is transferred to an inter-orbital transport vehicle known as the IOTV. This is the workhorse transporter that moves people and cargoes between points in space, and never lands upon any planetary body. Its structure seems frail and delicate compared with the airplane-like structure of the HLLV.
During the construction phase of the colony, the staging area handled replacement supplies at the rate of 1000 t a year. The growth and increasing population loading of the colony required transshipment of an average of 50 people per week together with their personal belongings and the additional carbon, nitrogen, and hydrogen needed to sustain them in space. Oxygen, and other elements, are obtained from the Moon. Later the big demand was for lightweight, complex components fabricated for satellite solar power stations. Initially the resupply of the lunar base also came from Earth. The 150 people on the Moon require 250 t of supplies and rotation of 75 people to Earth each year. Furthermore, there is traffic from the colony to Earth. Studies of past colonizations on Earth have shown that discontent with frontier life is usually such that many colonists wish to return home.
Cargo was brought up on earlier flights of HLLV's so that you do not have to wait long in the staging orbit. This reduces the amount of consumables needed to support the people between Earth and the colony. Every effort is made to get you to the colony as quickly as possible once you have attained Earth orbit. The freight had been transferred to the IOTV before your arrival, so no time is lost in moving the personnel carrier from the HLLV to the IOTV. The rocket engines of the IOTV begin to thrust and the vehicle breaks from Earth orbit and begins its 5-day journey to L5. You find that conditions within the personnel carrier are crowded somewhat like the transcontinental charter flights you experienced on Earth.
THE HABITAT AT L5
Like countless other tourists over the years you look for the first view of your destination. Just as European immigrants looked for the concrete towers of New York and the torch-bearing statue, you now anxiously await your first glimpse of the wheel-like structure spinning amid the black backdrop of space. Only in the last day before your arrival is your search rewarded. And then you are surprised at how small the space colony looks. Since you cannot judge distance in space, the colony appears first as a mere point of light that gradually exceeds the other stars in brightness, and then it forms into a narrow band of sunlight reflected from the radiation shield. Later you see the spokes and the hub. But still the 10 million tonnes of slag and Moon dust that have been compacted and placed around the habitat like a bicycle tire, seem no larger than the rim of a balance wheel in a ladies' watch.
Only in the last few hours of the trip, when the IOTV has matched its orbit with that of the colony and is waiting to dock, do you see the true extent of the habitat and begin to comprehend the immense nature of this man-made structure in space.
The View From the Outside
The space colony appears as a giant wheel in space. Still you cannot comprehend its size, but you know it must be huge. One of the other passengers who has been on the trip before tells you it is 1800 m in diameter. He points to the six spokes connecting the wheel rim to its hub and tells you each is five times as wide across as is the cabin of your space transport. You look in awe. He tells you that the rough-looking outer "tire" is really a radiation shield built of rubble from the Moon. It protects the colony's inhabitants from cosmic rays.
In reply to your question about the burnished disc that hangs suspended above the wheel of the space colony, he explains that it is a big mirror reflecting sunlight to other mirrors which, in turn, direct the light rays through several other mirrors arranged in a chevron form to block cosmic rays.
As you watch you become aware that the spokes are rotating, but you cannot see any motion in the rim. Again your companion explains; the habitat rotates within the outer shield. Rotation is needed to simulate gravity, but rotating the massive shield would produce high stresses that would require a much stronger structure. The inner habitat tube is accurately positioned within the outer shield so that the two do not scrape against each other.
He points to the hub of the wheel and tells you that is where your transport is heading to dock with the space colony, explaining that local custom has named the docking area the North Pole.
Figure 5-1 presents a general perspective of the principal components of the habitat. The torus provides the space for housing, agriculture, community activities, and light industry within a 130-m-diam tube bent into a wheel approximately 1800 m in diameter. Six spokes, each 15 m in diameter, connect the torus to a central hub and accommodate elevators, power cables, and heat exchange pipes between the torus and the hub. The spokes also act as diametric crossties to resist excessive deformations of the torus from internal concentrations of masses on opposite parts of the wheel. Glass windows mounted on aluminum ribs cover 1/3 of the surface of the torus and admit sunlight "downward" onto the agricultural and residential areas. The remaining 2/3 of the shell of the torus is constructed of aluminum plates. Details are given in appendix A.
Figure 5-1 — Colony configuration.
<!-- image -->Figure 5-2 — Cross section of the torus.
<!-- image -->Figure 5-3 — Hub configuration.
<!-- image -->Figure 5-4 — View of the interior.
<!-- image -->Figure 5-5 — Terrace housing application exterior views.
Image
Passive shielding against cosmic rays is a separate, unconnected shell with a gap of approximately 1-1/2 m between it and the torus. The shield, 1.7 m thick, is constructed from large "bricks" of fused undifferentiated lunar soil held together by mechanical fasteners. Over the window region the shield is shaped in the form of "chevrons" with mirrored surfaces which pass light by a succession of reflections but block cosmic rays. The shield and chevron configuration is illustrated in figure 5-2. (For a more detailed explanation see appendices E and K.)
If the shield is used as a reaction mass during spin-up of the torus it would counter-rotate at approximately 0.07 rpm; the relative velocity between the shield and the torus, would thus be about 100 m/s. The torus is prevented from scraping against the shield by a positive positioning device.
The stationary main mirror located above the docking area of the space colony reflects sunlight parallel to the axis of rotation onto the rotating ring of secondary mirrors which illuminate the windows (see figs. 5-1 and 5-2). The secondary mirrors are segmented and each segment is individually directed to regulate the amount of light entering the habitat. The flux of light in space is 1400 $W/m^2$, but requirements in the torus vary from 200 $W/m^2$ in the residential areas to 1000 $W/m^2$ in the agricultural areas. Furthermore, a diurnal cycle is required in residential and some agricultural areas, while other agricultural regions require continuous solar radiation. This is achieved by directing the light away from certain windows to obtain darkness and by concentrating the light from several mirrors onto other windows to meet the high flux demands.
As your ship moves smoothly toward the docking area, you become aware of the details of this gigantic wheel-like structure. You see the 100-m-diam fabrication sphere on the "south" side of the central hub. Your companion tells you this is where metals are shaped and formed and where much of the assembly and construction takes place. To one side of the fabrication sphere is a 200 MW solar power plant and furnace used in fabrication; in the opposite direction you see the dimly visible $4.9 \times 10^5$ $m^2$ expanse of the habitat's radiator with its edge toward the Sun. It radiates into space the waste heat of the habitat delivered to it by a complex of heat exchangers passing through the spokes from the torus to the hub. Like the docking area at the North Pole, the fabrication sphere and radiator do not rotate. (See fig. 5-3.)
As the IOTV passes over the spokes toward the hub you see areas of silicon solar cells suspended between the spokes, central hub, and secondary mirrors. Because they look northward toward the main mirror, these cells are sheltered by the other mirrors from the degrading effects of the solar wind. Your fellow passenger tells you they supply 50 MW of electric power required by the habitat. If control of the main mirror were accidentally lost or some other accident should cause loss of solar power, the 200 MW solar power station at the extraction facility, some 10 km from the South Pole, would supply emergency power.
The IOTV moves almost imperceptibly through the last few meters and gently attaches itself to one of the docking ports. All people and equipment for the habitat pass through these ports. There is an unexpected lack of officials and there are no landing formalities. One agent oversees unloading; a second acts as a guide to the passengers. Labor is scarce so that the colony cannot support a bureaucracy, explains your companion.
Passing from the docking module, you see the walls of the central hub moving slowly by you as you float freely under zero-g. You are now in the rotating habitat, but because you are near the axis of rotation, the rotation rate of 1 rpm gives no appreciable sensation of weight. In fact, a few workers on their lunch break can be seen cavorting in the almost zero-g of the central hub playing an unusual type of ballgame, invented by earlier construction workers.
The hub is, however, much more than a playground, it is a crucial crossroads for the whole colony. Six spokes converge from the torus to this 130-m-diam sphere and emerge from its walls. They carry the power cables and heat exchangers that connect the interior of the habitat to the external power supplies and the radiator. They also serve as elevator shafts through which several thousand commuters travel each day to and from their work in the fabrication sphere or outside the habitat. Now with the other new arrivals you enter an elevator in one of these spokes and begin the 830-m trip out to the torus. As the elevator moves and the sense of "gravity" begins, you realize that "out" is really "down."