CHAPTER III

 

External and internal structure

of the space settlement

IV.1. Shape

 

We have studied the advantages and disadvantages of different shapes for the space settlement.

While choosing the most suitable shape we considered more shapes like the sphere, the cylinder, the dumbbell, the belly cone, the cylinder with spherical endcaps and the torus.

 

The biggest disadvantage of the sphere is producing only a small strip of habitable land at the expensive of a gargantuan volume. Another disadvantage of the sphere shape is that it can be very hard compartmented and administered.

 

The cylinder has a very large living area but a very important disadvantage is the psychological one, because it is very unusual too see persons up your head. Another disadvantage is the too large amount of material used to create the necessary radius for the pseudogravity creation. Rotating cylinders also require too much atmosphere, of which 78% needed to be shipped up from earth in the form of nitrogen.

 

The dumbbell has the advantage of creating the necessary radius with saving material but it has very little volume for living in comparison with the material quantity needed.

 

The belly cone it is not a suitable shape because of the variable pseudogravitational illustrated in the figure below.

A cylinder with spherical endcaps has many advantages but for little dimensions, that‘s why we will user this shape for the 0 gravity center. We have the advantage of strict 0 gravity in the center of the cylinder, and constant pseudogravity on the endcaps. It can be easy segmented and it can contain a big amount of atmosphere, thus it can be also a temporary location for the colonists in case of the torus evacuation.

Cylinder with spherical endcaps

 

Studying all the possible shapes for the colony, we found that the torus is the most suitable shape for the space settlement habitat. It allows to control the radius which generates the atmosphere  volume separately from the radius of rotation which is a very important element in the creation of pseudogravity in good biological conditions. Moreover, the torus can distribute its habitable area in a large ring. Moreover a well rounded shape distributes equally and radially all the pressure forces. Another advantage of the torus is that it assures maximum habitable area requiring minimum amounts of materials. The torus also provides the largest habitable area per ton of nitrogen.

 

Volume of the torus

 

 

LEDA will have a composite shape containing both a torus and a cylinder with spherical endcaps. The torus will house the habitat of the colonists, while the cylinder with spherical endcaps will house docking facilities, industries, and research.

 

IV. External and internal structure of the space settlement

 

2. Dimensions

 

The dimensions of the settlement must be certainly calculated according with the assumed number of occupants, their average habitat needs and the requirements of the different activities they will develop onboard the orbital colony. Therefore, all estimations regarding the scale of the Settlement must be made by equally balancing comfort with maximum efficiency of the artificial habitat. We can allow no waste of space and materials, thus errors occurring within the design phase can severely affect the later development of the colony. Of course, we must also take into account the esthetical and homelike needs of the colonists, but efficiency in using, exploiting and distributing space inside the torus must overlook the less vital aspects.

 

As said, we must assure a comfortable and pleasant habitat for orbital colonists, considering their average needs and combining them with maximum efficiency in distributing space. The following calculations indicate the habitable volume of the torus according to a person’s average needs and to the minimum dead space (unused space) inside the torus.

 

We consider:  - the average inhabitable volume needed by a person

                        - the total number of persons onboard the settlement

                         - the total residential volume inside the torus

- the fraction of volume representing unusable space (related to the total residential volume )

                        - the uninhabitable volume part of the total residential volume (occupied by walls, buildings etc.)

                         - the volume of the torus;

                        - the rotation period

                        R- the large radius of the torus

                        r- the small radius of the torus

                        - the angular speed of the torus

                        L- the outer circumference of the torus

                        Ah – the habitable area

                        - the habitable area per person

                       

The needed total residential volume is:

 

  [1]

 

 

 

 

 

 

 

 

 

 

x2 + (y-R)2= r2 – the equation for the circle  C(O,R)

 

 

=R+

 

Vrotation – the volume of the rotation body obtained by rotating the graphic representation of the function around Ox

Vcylinder – the volume of the cylinder having R as radius of the base and r as height

Vdifference = Vrotation-Vcylinder

 

 

Vcylinder=

 

Vrotation =

 

 

We also know that

 

 

 

 

 

We can observe an interesting fact about the volumes:

 

 

 

                   

[2]

 

 

 

 

 

 

 

 

 

 

 

 

Taking into account the rotation motion of the orbital colony, we must determine the radius (R) for which   the simulated gravitational constant along the residential area is optimum ().

  [3]

 

 

 

 

The graphic representation above shows the relation between the radius and the angular speed of the torus for which the simulated gravitational constant along the inhabited circumference is.

 

 

Considering the reaction of the human body to different angular speeds, we have chosen a rotation period of 127 s to be most suitable for the Space Colony. Therefore we can now determine the major radius (R) of the torus.

  

   [4]

 

As the feasibility of the Space Settlement strictly depends on the available technological possibilities, its structure and dimensions must well accord to precise construction and engineering norms. The most economical solution would be building a torus in which the ratio between the major radius and the minor radius allows the minimum residential area and volume per person. Still we have to consider the psychological needs of colonists; as in this case the minor radius will be too small to simulate a realistic sky and to minimize the sensation of an enclosure we must choose another option. Respecting the different proportion laws we reached the conclusion that the minor radius of the torus (r) should be 1/8 of its major radius. That means about 500m, a distance large enough to prevent the colonists from feeling somehow secluded. 

 

    [5]

  

 

Therefore we can now determine the residential volume inside the torus ()

 

   [6]

 

We consider a minimum habitable volume per colonist of about 2000m3. For creating superior life conditions and better reproducing the demographic density on Earth and for avoiding possible overcrowding due to the population growth we must supplement this volume with an average of 28000m3 per person. In this case, the residential area per person will be of about 100m2.

 

 / person  [7]

 

/ person     [8]

 

By combining relations [1] and [6] we can estimate the initial number of colonists.

 

 

 

   [9]

 

 

We can now determine the other numeric dimensions of the torus:

 

 

All calculations are made in the perspective of a dynamic demography which could lead to the doubling of the population in less than ten years. 

 

Because of its industrial use, the central body of the torus (or the 0 gravity center) has a larger fraction of inaccessibility (f=60%). As the 0 gravity center is the main industrial core of the settlement, providing it with all required goods, it must dispose of sufficient space for efficiently carrying its activity. With the development of different technologies, the need for new industrial facilities will surely appear; wherefore we must provide enough space for the future expansion of industry onboard the Settlement. Concurrently, the 0 gravity center will be the only sheltering place in case of emergency evacuations caused by the different damages that can occur in the structure of the ring. Its life sustaining system will be independent and it will be able to temporary accommodate more than 250000 people; still, it must maintain the current industrial production to ensure life onboard the undamaged part of the settlement. Therefore, its dimensions must consider both its industrial and emergency use.

 

Taking into account the eventuality of a considerable population growth and that of a future industrial expansion we designed an initial volume of about 1304m3/person inside the central body (considering both functional and emergency aspects). As the residential norms assure1740 m3/person, this space is enough to be efficiently used in constantly developing industrial activities and in recreating all conditions, facilities, even commodities in case the habitable ring of the Space Settlement becomes unavailable for a longer period of time. In normal circumstances, this space could use as extra-storage room for goods produced inside the industrial core or even as leisure site.

 

We consider:

f’- the fraction of inaccessibility

r – the larger radius of the central body

Vcb – the volume of the central body

Asp1 – the surface of the solar panels on the 0 gravity center

Asp2 – the surface of the solar panels around the 0 gravity center

Aspt- the total surface of the solar panels

- initially, the functional and emergency volume / person should be of about 1304m3

Rsp – the radius of the solar panels around the central body

 

Small evacuation modules must also be provided in case the 0 gravity center is damaged and can not sustain life anymore. We studied the spacecraft habitats which have been already used in different space missions and reached the conclusion that the average minimum volume required by a person is 2.5m3. Therefore the dimensions of the evacuation modules must afford at least 2.5m3/person; the chemical composition inside must be 72% O2 / 28% N2 at 5psi. (The evacuation procedures are explained in chapter VII.9 – “Risk factors”). A Spacecraft habitat summary is listed below:

 

 

 

Summary of spacecraft habitats

Effective volume (m3)

Pressure

Chemical composition / Pressure of the gaseous environment

Number of crew members

 

Russian spacecrafts

 

 

 

 

 

 

Vostock

2 m3

sea level pressure

21% O2, 79% N2

1

Voskhod / Soyuz

5 m3

13.7-16.4 psia

2.7-3.9 psi ppO2

3

Salyut Space Station

81 m3

13.5-18.5 psia

3.1-4.6 psi ppO2

 

MIR Space Station - Base block, Kvant 1, Kvant 2, Kristall, Spektr, Priroda

~90 m3 ea.

sea level pressure

6.8 psia ppO2 (21-40%)

 

Mercury

1 m3

5 psi

100% O2

1

Gemini

3 m3

5 psi

100% O2

2

Apollo

7 m3

5 psi

100% O2 on orbit

3

 

 

 

60% O2 / 40% N2 during launch

 

 

US Spacecrafts

 

 

 

 

 

 

Lunar Module

5 m3

 

 

2

Command and Servicing Module

7 m3

 

 

 

Skylab Orbital Workshop

approx. 300 m3

5 psi

72% O2 / 28% N2

 

Orbiter

71 m3

sea level pressure

3.1 psi ppO2 (21%)

 

 

 

 

10.2 psia pre-EVA, 30% O2

 

Spacelab

~70 m3

 

 

 

SPACEHAB

~31 m3

 

 

 

ISS

~1200 m3

 

 

 

 

 

 

The internal structure of the settlement must serve both as residential and productive environment. As it should maintain life for very long periods of time there must be tight relations between the different structural parts of the artificial environment.

 

The two main components of the space settlement must assure appropriate conditions of life within their exterior walls. Therefore the interior of the torus must be properly divided to ensure an efficient use of space and materials. In the perspective of population growth and industrial expansion enough space space must be set apart for future developments inside the Settlement.

 

As we said the interior of both torus and central body must be used for two main purposes: the building of spaces designed for living and spaces designed for life maintaining activities. Therefore, the ring of the torus will be divided into two main volumes. The volume closest to the center will be the one designed for residential purposes, while the one in the exterior will serve for industrial, agricultural and transportation purposes, as shown in Annex a.

 

For main elevators carrying a maximum of 100 persons each will permanently connect the extreme points of the Colony: the lower floors of the exterior volume with the 0 gravity center. For maximum efficiency, they will be situated symmetrically towards the 0 gravity center, at approximately equal distances from the main residential and utilitarian areas. The inner residential volume will shelter a detailed inventory of facilities and structures required for individual and community activities: residences, schools, shops, libraries, administrative offices, recreational areas, work places etc. 

 

The outer volume will also be divided into 12 floors attending different purposes. The first floor (I), situated right between the residential areas, will shelter all pipe lines providing houses with water. The next floor (II) will accommodate the different storage facilities, the interior transportation system and two Gravitational Cosmodromes.

 

As the tangential speed reaches its maximum on the exterior circumference of the torus, the outer side of the Settlement ring can be used for launching space modules and shuttles on orbit without having to ignite their motors and thus using energy. They will burst forth from the torus with a speed equal to the tangential speed on the outer circumference of the settlement. The launching moment will be determined depending on the direction in which the modules must be headed. Therefore, the two Gravitational Cosmodromes on the exterior ring will be the basic launching facilities onboard the Settlement. Still, they will be less sutiable for docking maneuvers because of the high rotation speed of the exterior ring. The principle is detailed below:

 

- the tangential speed on the outer circumference of the torus equal to the launching speed

 

 

 

 

 

 

Levels III, IV, V, VI, and IX, X, XI will serve exclusively for agricultural purposes. Providing the specific formula for the area of a level is (where R is the major radius of the torus, r is the minor radius of the torus, x is the hight of the floor) we can determine the approximate value of the total agricultural surface, which is 26.7 Km2.   Plant growing will take place according to the different plant metabolisms and needs. Therefore, the temperature, the light intensity and specter and the CO2 concentration inside the different “flats” will vary depending on the different crop types.  

 

The livestock growing facilities and some of the primary food production installations will be found on floors VII and VIII. The main reason why they are situated between plant growing floors is that the livestock growing facilities cannot be placed in the immediate proximity of human residences because they could represent a serious factor  of discomfort (source of odor and noise). On the other hand, livestock cannot be placed near the High-Gravitational Industry because of the noise produced by the different industrial facilities there. Being near the main sources of vegetal food, it will be very easy to supply the livestock growing facilities with the needed forage.

 

The main water pumping station , as well as the High-Gravitational Industry will be found on floor XII. The pumping station will resend water reaching the lower floors towards the central body of the Settlement, where it will be treated and reintroduced in the water supplying system.

 

The simulated gravitational constant on this floor can easily be determined.

 

  

 

The high gravitation environment can be exploited by using it in different industrial activities, such as the intensification of the chemical processes, the recovery of diluted components from large aqueous streams, the crystal growth by solidification or the different adsorption systems.

 

A small empty space will be maintained in the extreme point of the torus; the reason why no installation or device can be used within this last floor (XIII) is that it is too close to the electro-magnetic coils.

 

Most of the floors are disserved by emergency and utilitarian elevators to ensure a rapid and fluent transit inside the industrial  part of the torus.

 

The central body of the torus (Annex b) will shelter the industrial core of the Space Settlement. As it ensures a low gravity environment, it would be an ideal place to develop all industrial activities requiring the lifting of heavy or dense materials. The absence of wind and the 0 gravity conditions will allow the handling and assembling of huge components. Zero gravity also means the absence of convection currents in the different molten materials. Therefore, the material separation process, the crystallization progress and the mixing of materials will become much easier to achieve. Creating new types of alloys and crystal forms inexistent on Earth will surely be possible within 0 gravity conditions. The main water tank used in supplying the rest of the Colony with fresh water and the main water treatment station will be situated in the center of the central body, so that they will be evenly distant from all points inside the torus. 95% of the industries onboard the Space Settlement will develop their activity within the 0 gravity center (chemical compounds, solar power plants, ore smelting and metal processing facilities etc.)

 

Recreational areas will also be placed inside the central body of the Settlement, providing colonists with the chance to experience different entertainment activities in microgravity conditions (sports fields, small amusement parks)

 

Considering the diversity of activities taking place within the central body of the colony, the space inside it must be efficiently compartmented and isolated, so that the industrial processes would not interfere with the recreational ones. In the same time, industrial designers must provide efficient solutions for creating a rapid and fluent circuit of materials throughout the processing phase involving minimum amounts of energy. 

 

Another important part of the central structure consists in the main docking facility of the Colony, situated below the inferior surface of the 0 gravity center. As the tangential speed near the center of the torus is null, the docking procedures will be safe and will not entail complicated maneuvers. From here, the space modules will be transported using a rail system to the Gravitational Cosmodromes outside the ring for further launching.  

 

 


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