Archipel

Prospective of space exploration

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© Olivier Boisard - 2006-2013

 

2 - General Description


The city is composed of :


• three habitats, protected from cosmic radiation and solar particles emitted by the Sun, with residential areas in “terrestrial” conditions : temperature, atmosphere and gravity.

• the industrial and logistic area, highly automated (human supervision only) and operating partly in space environment: vacuum, low temperature, 0-g, radiation. They include “docks” and main access points to the city.

• agricultural greenhouses lit and heated by the Sun (atmosphere and lighting optimized according to the kind of crop).


And :

• the solar power station,

• the radiating panels for thermal regulation,

• the cables connecting these elements.


Elevators and traffic corridors provide appropriate carrying and communication capacities between these elements. Each zone has an access adapted to its functions (sas).


The three habitats, situated at the apexes of an equilateral triangle, are connected by cables to the central industrial area and between them. The whole structure has a spin of one rotation per minute, to recreate Earth's gravity in the habitats located at a distance of 900 m from the axis. This solution, very constraining compared to the absence of gravity (as in the ISS International Station) or a reduced gravity (like the Moon or Mars), seems an essential condition for maintaining long-term health for inhabitants and the possibility of their return to Earth.


The greenhouses are located in the plane of the triangle, at an intermediate distance (a minimum gravity is needed in agricultural areas). This is the case too for solar panels. This means maintaining the rotation axis of the city "pointed to the Sun" throughout the year, while the “gyroscope effect” of rotation has a tendency to keep it in a fixed direction relative to the stars. An "attitude control system" (SCA) has thus to be used in order to rotate the city 360 degrees a year, and correct continuously the orientation of the main axis.


This architecture is not arbitrary. It focuses on three basic forms - sphere, torus, and triangle - to optimize structural constraints:


• the sphere (for residential areas and greenhouses of vegetable crops) has the best surface/volume ratio, and minimizes the mechanical structural constraints (forces related to containment of pressurized areas, control of low frequency vibrations).

• the torus, with less interesting mechanical properties than spheres, appears however to be the best solution for large areas (20 ha of extensive fields for agricultural production) on a circumference at intermediate gravity.

• the triangle, forming isostatic structures for stretched cable bundles. Greenhouses’ tori are in the incircle of the triangle structuring the general form of the city.


Habitats


Each habitat is composed of four main areas interconnected by bushings composed of cylinders or truncated cones. The length of the whole is about 400 m with a maximum diameter of 100 m.


The structure resists to internal pressure, and protects inhabitants against ionizing radiation and micrometeorites. It includes an aluminum alloy frame coated with an aggregate of lunar regolith and epoxy resin 50 cm thick. In this structure is added a liner internal elastomeric sealing.

Inside, the usable surface is about 350,000 m2, spread over several levels for private areas, social activities and public facilities (education, health, sports, leisure,… ). The population density is comparable to the density in a contemporary metropolitan area (about 100 m2 per inhabitant).


Habitats are pressurized at 800 mbar. The composition of the atmosphere is the same as on the surface of the Earth, with the average temperature (20°C) and the humidity rate (60%) of a tempered zone.


Unlike O'Neill Space Islands using only the Sun, the light in habitats is partly artificial. The potential for adaptation to different situations (day / night cycle, annual variations, physiological optimization, etc..) are virtually endless, without requiring a direct capture of sunlight, technically complex.


Spheres are linked by three sections. In these sections are anchored stiffened cables connecting habitats with the central area. Large transparent bays are provided on the inner faces of truncated cones, offering a panoramic view to the rest of the station.


At this stage of the project, we do not preconize any interior design in the habitats. Do we have to be inspired by cruise ships, troglodyte villages or Asimov's Caves of Steel ? We do think that it should be the choice of the inhabitants. Their architects, planners and decorators will design and build living areas and, subsequently, adapt and change their choices in the respect of basic technical standards (masses, structures, networks, health, security, ..). The challenge will be to provide spatial diversity and temporal change in this confined space, and compensate the absence of wide horizons.


However, we may start looking at ways to solve these questions. For instance, residential areas could be located in the two largest areas of each habitat, each one accommodating about 1700 inhabitants. In the center of the habitat, the two smaller spheres would contain various public spaces, including "natural areas" in transparent hemispherical domes (gardens with water and vegetation) lightened by mirrors oriented 45 ° outside the habitat.


Industrial Zone


This zone includes:


  1. Small industry: food processing and packaging, production of components and equipment (including furniture, clothing, .., excluding art and crafts.), maintenance and repair of the city, testing laboratories and control, etc…


  1. Storage of materials, shipping containers, equipment, liquid and gaseous elements, silage and conservation of agricultural products,


  1. Transport of passengers and freight: docks, transit areas, maintenance and repair of the vehicles, storage and refueling of propellants and fluids.


• Leisure center in zero-g, which could by used as a shelter in case of a serious accident in a habitat requiring the evacuation of all or part of the population.


The industrial area is composed of two large hemispheres, with a pressurized volume of approximately 100,000 m3 each. Except low gravity (maximum 0.3 m/s2 to the periphery), the industrial area has the same characteristics as habitats in terms of atmosphere and protection. Containers and materials requiring neither atmosphere nor protection can be stored on an external parking area.


Greenhouses


Trying to transpose terrestrial food production methods would be unrealistic, as the ecosystems of the city couldn’t survive, and because of the “low yield” of usual agriculture and animal husbandry. Ecosystems of the city should be as simple as possible, isolated from each other, and strictly controlled. At least at the beginning, the staple of the diet will be purely vegetable, produced in high-efficiency greenhouses. Given the current progress in this field, we may assume that the inhabitants of Apogeios will draw balanced diet and delicious meals.


In addition to food production, greenhouses ensure regeneration of the atmosphere in habitats (CO2 absorption and oxygen regeneration by photosynthesis). They are of two types:

• 20 hectares of "fields" for the extensive culture of cereals (wheat, corn, sorghum) and various protein (soy, flax, rape).

• 10 hectares of "garden" for fruit and vegetable farms.


These surfaces have to be increased by about 10% due to the immobilization required for the periodic regeneration of greenhouses. Every three years, a greenhouse should be fully cleaned, the ecosystem destroyed, and equipment sterilized by vacuum and UV sunlight. The greenhouse will be then cultivated again with strictly controlled seeds. This is the price to pay to ensure the sustainability of these closed ecosystems.


The greenhouses are designed to:


• provide a wide variety of fruits, vegetables and cereals (at least the 120 most important produced), on the basis of 0.62 kg of food per person per day [2], 2300 T / year for 10,000 people (6 t per day).

• provide flax and cotton for clothing (quantity to be defined).

• provide the basis of vegetable cosmetics and pharmaceuticals (quantity to be defined).

• recycle carbon dioxide on the basis of 1 kg per person per day [2], about 4000 t / year for 10,000 people (10 t per day).


Culture is essentially aeroponic / ultraponic. The plants are fixed to metal grids and immersed in a light nutritious mist: water, fertilizer, micronutrients, and pesticides.

• optimum lighting (intensity, spectrum)

• 1/6 g minimum

• Atmosphere: T = 32 ° C, O2: 168 mbar, N2 and humidity to define, CO2 : 300 to 1300 ppm.


This kind of agriculture allows, in some cases, an increase of the yield by a factor of 8 compared to the culture on substrate (130 inhabitants / ha). We take the factor of 2.5, 30 m2 / person.



Toroidal (extensive culture) or spherical (fruit and vegetable farms), the greenhouses are inflatable transparent polyethylene structures. Because of the gravitropism of plants, cultivated areas should be perpendicular to the direction of gravity. This implies reflecting sunlight with mirrors. For a Sun about 45 ° to the zenith, like in tempered latitudes, we may optimize the surface of usable floor thanks to a terraced arrangement.


All greenhouses consists in three torus with a mean radius of 455 meters for extensive culture (two 20 m section, one  30 m),  and 228 spheres of 25 m diameter divided into 12 clusters of 2 x 19 greenhouses. The level of gravity is about 0.5 g, atmospheric pressure is low (corresponding to a terrestrial altitude > 4000 m).

The atmosphere is tropical, with a high rate of CO2. GCR protection is reduced, the plants being more tolerant to ionizing particles than human organism. Only robots work there. When necessary, men operate with mask and full-body suit, slightly pressurized to compensate the low atmospheric pressure.




Water


While important, the water issue was not addressed at this stage of the project. We believe that this raises no major problem, neither for supply, storage or recycling. We can estimate the global consumption for all needs (individual and collective, agricultural and industrial) at about 2000 m3/day. The water can be recycled quite easily and almost entirely by simple physico-chemical processes (steam condensation, nano-filtration and reverse osmosis of liquid waste [2]) .


Water is also a very effective protection against Solar Particles Events (SPE) [3].  Therefore, it is conceivable to use it as a protection for inhabited area exposed to the sunlight, in a double wall enclosing a layer a few centimeters thick.  This protection would also be a provision of water of a few thousand m3.


Solar Power Station


Based on current French consumption in 2010, 500 TWh / year (60% for the residential and tertiary sector), the average power required for the city is about 5 MW. Adding industrial and agricultural applications and taking into account peak demand, the power requirement of about 7 MW, an order of magnitude between the ISS (100 kW) and SPS projects (at least 1GW).


At L5, the power radiated by the Sun is the same than on Earth, about 1400 W/m2. But photovoltaic panels still have a poor performance. Based on a power output of 65 W/m2, more than 10 ha of panels are needed to provide the required 7 MW. It is likely, however, that this performance will be improved.


Many types of structures are possible. One of the simplest is a ring of panels centered on the axis of the city, with a small outside radius to be as light as possible.


Radiators


The city produces heat mainly from electricity consumption. The only way to dissipate this heat is to radiate into space.


As habitats are very well insulated thanks to GCR protections, there must be specific radiating surfaces using diphasic fluids in a cooling circuit (vaporization exchangers in the habitat, liquefaction in the external "radiator").  Using ammonia (NH3) which liquefies at -33 ° C (under a pressure of 1 bar), about 4 hectares are needed to radiate the 7 MW of energy consumed.


Unlike the solar power station, this surface is distributed on the three habitats and the central area, allowing shorter circuits and therefore reducing the power of pumps. Each habitat is surrounded by a cylindrical sector of radiant panels at a temperature of 240 ° K, in such a way the radiation is perpendicular to sunlight. In the central area, radiant panels are only on one hemispheric sector, on the side opposed to the Sun.


Cables


Each housing is connected to the central area with cables (like suspension bridges) of metal or carbon fiber. 24 cables of high strength steel, 60 cm in diameter and 900 m long, can hold twice the weight of a habitat, estimated at 150,000 T.


Cables grouped in sets of four are rooted in the structures connecting the spheres, distributing the important constraints concentrated at the attachment points, and limiting the mechanical freedom of habitats.


These cables also support light structures of communication tunnels, solar panels, and other devices such as hoists. By cons, a specific system is designed for greenhouses. Habitats are also linked together for reasons of dynamic stability and / or safety.


During the construction, a scaffold will be used to connect the cables, and removed once the structure, gradually rotating, will have a sufficient rigidity.

 

Pierre Marx & Olivier Boisard

© Olivier Boisard & Pierre Marx - 2011

APOGEIOS, a concept of space city

Introduction - Main Principles - General Description - Other Issues - Plans of Apogeïos - 3D Animation - Prize of the J.Rougerie Foundation
Apogeios_1_eng.htmlApogeios_2_eng.htmlApogeios_4_eng.htmlApogeios_5_eng.htmlhttp://www.planete-a-roulettes.net/MEDIATHEQUE/Videos/Entrees/2011/12/11_APOGEIOS.htmlApogeios_6_eng.htmlshapeimage_5_link_0shapeimage_5_link_1shapeimage_5_link_2shapeimage_5_link_3shapeimage_5_link_4shapeimage_5_link_5shapeimage_5_link_6
Introduction - Main Principles - General Description - Other Issues - Plans of Apogeïos - 3D Animation - Prize of the J.Rougerie Foundation
Apogeios_1_eng.htmlApogeios_2_eng.htmlApogeios_4_eng.htmlApogeios_5_eng.htmlhttp://www.planete-a-roulettes.net/MEDIATHEQUE/Videos/Entrees/2011/12/11_APOGEIOS.htmlApogeios_6_eng.htmlshapeimage_6_link_0shapeimage_6_link_1shapeimage_6_link_2shapeimage_6_link_3shapeimage_6_link_4shapeimage_6_link_5shapeimage_6_link_6