����������� Theconstruction of �ther will call for unprecedented cooperation both on earth andin space, as massive funding and efforts will be required.
����������� Thefirst stage of construction will be the establishment of a launch site, thenrobotics miners would be sent to the moon to establish a lunar base consistingof launching, landing, and processing facilities.� There automated machinery would harvest and process lunarmaterials, stockpiling necessary resources.Then the inner spheres would be built in orbit around the moon, usingmaterials launched from the lunar surface, and then propelled to L5 using ionthrusters or a magnetic driver.Thereafter, automated workers at L5 would catch materials sent to L5from the moon, and use them to construct the remaining components of�ther.� Human participation in the constructionshould be delayed as much as possible, in order to keep down costs, but CELSSmachinery would be shipped up from earth along with the human workers so thatthey can survive in the space environment.
Just asessential as a well coordinated project in the sky is the equal efforts ofresources, minds, and power on the ground.A monumental station such as �ther calls for a sister base onearth.� In order to complete and managethe extensive building and maintenance of the space station, we feel therequirement for a land base here on earth.This land station requires three main characteristics.
Precedence forselection of launch sites for projects of this scale can be found in the Apolloprogram.� NASA�s air force team put outinformation on their choices on possible launch cites.
With thesesneeds and specifications in mind, an ideal launch site could be developed inAlcantara, Maranhao in Brazil.Alcantara is located at 2.24� S and 44.24� W.� Actually, there is a small development of an already existinglaunch site at this location.� For thisproject, all that would be needed would be to further expand the currentbase.� Alcantara is a small city, of apopulation less than 20,000 that lays on the Baia de Sao Marcos.
Some of thefacilities that would be built or expanded include: living quarters forparticipants in the project, a command center for monitoring of launches andconstruction, radio dishes for communication, an airport to accommodatesupplies and people coming in by air, a port to facilitate large shipments, andwork areas where the space ships would be readied.
II.B Automation/Remote Control
����������� Heavy automation will be key to the success of theconstruction and maintenance of �ther at a low cost in terms of money and humanlives.� Fortunately, except for a fewunfortunate incidences, the American space program has been relativelywell-shielded from the dangers associated with human spaceflight.
����������� Obviously,the robots and workers who will construct �ther will need a way to reach theLagrange point.� Additionally, �ther,the earth, and the moon will eventually form a trading triangle thatnecessitates a fluid transportation system.Transportation in between �ther, the earth, and the moon will be ofvital importance to �ther�s economy as goods and raw materials will need to beable to be flow freely to and from each of the trading triangle�s vertices.
����������� Spacetethers utilize the momentum or electrodynamic transfer to propel objectsthrough space.� Momentum transfer can bevisualized by having two satellites connected by a tether, with one of thesatellites is in a higher orbit than the other.� The larger of the two satellites then uses the tether to�slingshot� the other satellite into a different orbit, at a cost of its ownkinetic energy.� This slingshot motionarises since the satellite with a lower orbit has a faster tangential velocitythan the satellite with the higher orbit.Thus when the higher satellite is released it will embark on a moreelliptical orbit than the one it was previously one.� A similar tradeoff between kinetic energy and electrical energyalso exists in electrodynamic transfers.Space tethers would be used for assisting objects in low earth orbit(LEO) into a transfer orbit that would take them either to the moon or to�ther.
II.C.2 Single Stage to Orbit(SSTO)
����������� AchievingSSTO is one of the crucial elements of not just constructing a space colony,but also the continuation and expansion of current spaceflight.
����������� Another interesting concept is that of a spaceelevator.� Built from geosynchronousorbit, the space elevator would be above the same place on earth at alltimes.� A counterweight that extendsjust as far radially outwards from earth would be needed to ensure that theelevator does not fall out of orbit because of its weight and crash intoearth.� Such an elevator would requireultra-strong materials in order to be economically feasible, but would catalyzegrowth of space colonization; frequent, cheap, non-polluting launches would bepossible.
There are three main sources ofmaterials that can be considered for use in constructing �ther: the earth, themoon, and other orbiting bodies such as asteroids and comets.
Generallyutilization of terrestrial resources should be kept to a minimum since thetransportation costs are prohibitively high.However, some elements, such as nitrogen, cannot be found elsewhere andmust be shipped up from Earth.
Because of itsweak gravity and n .onexistent atmosphere, the moon presents a more economicalsource of materials.� These materialscan be easily transported to L5 using magnetically-powered mass drivers, inwhich the payload is given momentum by a bucket accelerated by strong magneticfields.� The packet would then be caughtat L5 and then utilized in construction.The Moon is an excellent source of oxygen (42% by weight), silicon(21%), iron (13%), calcium (8%), aluminum (7%) in addition to other metals andnonmetals such as titanium [ref 1].Different methods can be utilized for obtaining these resources.
����������� Althoughthe lunar soil is 42% oxygen by weight, it is in fact underoxidized.
Iron, oxygen,and titanium can readily be extracted from lunar ores through the hydrogenreduction of ilmenite.� The reaction is:FeTiO3 + H2 --> Fe + TiO2 +H2O.
����������� Magma electrolysis is an energy intensive processthat requires approximately 13 MWh per tonne O2 [ref 23].
����������� Vacuumdistillation utilizes the different boiling points of ore components toseparate them.� Ore is placed inside avacuum chamber and then heated; the evaporated components are then collectedduring different temperature periods.This relatively easy process can be replicated on a large scale and canproduce aluminum as well as iron and oxygen.Because of its simple and robust nature, vacuum distillation relies onfacilities that are not easily damaged and can be easily furnished [ref24].� The heat energy requirements forvacuum distillation can easily be met through waste heat recycling from otherlunar processes or could be collected from the solar flux.
����������� Asteroidsand comets are known to contain vital substances such as water, platinum groupmetals, iron, nickel, as well as other valuable ores.� Of course, the composition of asteroids varies, but there aremany valid targets, both small and large, that would be within close reach of�ther.� In the case of small (less than3 meters) asteroids, they could possibly be retrieved in their entirety, whilemining would be required to extract materials from larger asteroids.
����������� Differentshapes were considered as possible shapes of the space colony.
�����������
�fig. 2.1
The torus would be made out oftitanium plates welded to titanium ribs in the form of circles rotated aboutthe center of the torus.� Initially,these plates would be very thin, but they would be strengthened after vacuumdeposition techniques add more titanium to them.� Using thin plates is ideal, since titanium is very strong andhence hard to work with, reducing the thickness would mean that less powerfultools could be used to create the structure.The spheres would also be made using similar constructiontechniques.�
Althoughautomated workers would build most of �ther, there will be a point when humanworkers will arrive at �ther and begin to construct parts of �ther.
II.E.1 Structural Material
����������� The structural integrity of �ther will depend on thematerials that constitute it.� Due totheir abundances on the moon, the metals and alloys of titanium, aluminum, andiron were prime candidates.� Titaniumwas eventually chosen as the material of choice since it has a low coefficientof thermal expansion, one of the highest strength to mass ratios among themetals, and also has a high melting point.These properties make using titanium attractable in building �ther,since it will be subjected to varying temperatures and high stresses.
����������� Titaniumalloys should also be considered, titanium has three classes of alloys: Alpha,Alpha-Beta, and Beta.� Alpha alloys arenot heat-treatable and are weldable, they also have excellent mechanicalproperties at cryogenic temperatures.Alpha-Beta alloys are heat-treatable, which strengthens the material bya sudden drop in temperature, and also have higher tensile strength than Alphaalloys.� Beta alloys can also be heattreated, and have excellent creep resistant properties.
����������� Tomaintain proper rotation, a water ballast system will be incorporated into thestructure.� This system will ensure thatthe colony�s center of mass closely correlates with the actual center of thetorus.� Compromising of storage tanksinterconnected with electronically controlled pumps, the WBS can also serve aswater storage and additional radiation shielding.
����������� Sincethe glass of �ther�s sky will be subjected to a 14-hour day, 10-hour nightsunlight schedule, it will experience expansions and contractions as it heatsup and cools down.�� Thermal stressplayed a major role in the materials selection process, but materials selectionalone cannot prevent metal fatigue.Instead, using a multiple hull system like those found in submarinesshould combat both metal fatigue and enormous pressure differences at the sametime.� The multiple hulls combined withthe radiational shielding should insulate the inner metals and the multiplehulls provide superior strength to the torus walls.
�fig. 2.2
����������� The excessheat caused by the CELSS, manufacturing, and research processes will have todissipate their heat in some way.� Heatrejection can be achieved by exhausting coolant into space, but this method ismass-expensive when compared to radiator methods.� Radiating the heat into space as radiation is the most commonlyused method of rejecting heat.Radiators operate on either passive or active principles.
����������� In order to provide the requisite illuminationneeded, a method to propagate light so that it seems to come from the �sky� ofthe torus will have to be utilized.� Onepossible method is to use artificial lighting, however, this system would notbe ideal since incandescent bulbs draw too much power and possesses a �harsh�light, while fluorescent lights possess a flicker that would contribute to theartificiality of the colony.� ALED-based lighting system may work, but would prove costly in terms ofmanufacturing and maintenance.� Thus,mirrors that reflect light into the torus will be considered forillumination.� A simple configurationconsisting of a circular mirror with a diameter of 3.35 km angled at 45� to theplane of the torus reflecting light onto a section of a conical mirror alsoangled at 45�.
�fig. 2.3
The secondary mirror can bethought of as a surface of revolution, or the sides of a cone with bases of2.35 km and 1.81 km.� It will beconstructed of an aluminum framework containing glass inserts coated withreflective metal.� The individual panelscan be rotated by electric motors, thus providing a way to create the 14-hoursunlight, and 10-hour night cycle.
����������� Aparticular orbit, that could be stable enough for the space colony, is theso-called Lagrangian Orbit, named after the French mathematician Joseph-LouisLagrange. A Lagrangian orbit is the orbit of an object located at a Lagrangianpoint, or also libration point. In such an orbit the body will be in astation-keeping position, that is keeping it in orbit at the cost of lessmaneuvers. There are 5 Lagrangian points for the two body system Earth-Moon,three of which L1, L2 and L3 are gravitationally unstable These are pointswhere the body is in a balance, because the gravitational pulls of the Earthand Moon cancel each-other. However, even small perturbations, such as solarwind will cause the body to lose its unstable equilibrium and plunge intochaotic motion, which will have to be constantly corrected with thrusters [ref45]. Unlike the other three points, putting the colony in points L4 and L5 willmake it stay in a stable equilibrium, that is even if there are perturbations,the body will tend to go into its original orbit. Actually, the body will beactually wobbling around the Lagrangian point, which is practical for puttingbigger constructions in this point, such as our space colony [ref 46].