II. Construction

            Theconstruction of Æther will call for unprecedented cooperation both on earth andin space, as massive funding and efforts will be required.  The first problem that came to mind was theestablishment of a launch site capable of handling the massive traffic loadsnecessary.  Locating a materials sourceready for large-scale utilization was also of concern, since Æther will be thelargest object to be created in space.Finally, the design of Æther should be honed to the needs of the colonists,and thus must take into account their spatial, visual, psychological, andnutritional needs.

            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 ofÆther.  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.

 

II.A Launch Site

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 Æther 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.  The first is clearly the ability toaccommodate resources, personnel, and overall international support by sea andair.  The next requirement is a closeproximity to some sort of major metropolitan area, yet still remaining somewhatdistant.  Such closeness offers manyadvantages.  This prevents the projectfrom total seclusion from society, as well as the ports of sea and air thatalso lay close by.  The metropolitanarea gives a large pool of potential employees of the massive project.  The distance from such a major metropolitanarea reduces potential for disaster in case of launch mishaps.  Natural factors, such as weather, play in ascrucial aspects of the decision.

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.  They considered candidates from a panel of 8United States locations.  They were,Cape Canaveral; offshore from Cape Canaveral; Mayaguana Island in the Bahamas;Cumberland Island, Georgia; a mainland site near Brownsville, Texas; WhiteSands Missile Range in New Mexico; Christmas Island in the mid-Pacific, southof Hawaii; and South Point on the island of Hawaii.  By breaking down the advantages and disadvantages of theselocations, a better view of what is preferable for a launch site can be discovered.  To begin with, one barrier to most of thesesites was the cost of purchasing land.In this project however, it wouldn’t be a limiting factor, but therewere many other specifications, which can be deduced from more analyzation.  The White Sands area was deemed cheapest todevelop and maintain, although its landlocked location was something that wouldinhibit and restrict goods from coming by sea, which is often the cheapest longtransportation method.  The island sitesof Mayaguana, Christmas, and Hawaii, were ruled out for the shear extensivecost over the other proposed sites.These islands also posed severe problems of logistics.  Such an isolated and small region of landwould complicate building, launching, and maintenance.  The Brownsville site brings up the problemof relative proximity to large and densely populated areas.  Thus the ideal site would be close to thesea, close to an inexpensive energy source, and isolated from populationcenters, but close to key suppliers.  Anadditional criteria is for the area directly eastward of the launch site to beuninhabited, since most launches will be eastward to take advantage of theearth’s rotation.

With thesesneeds and specifications in mind, an ideal launch site could be developed inAlcantara, Maranhao in Brazil.Alcantara is located at 2.24º S and 44.24º 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.  On the coast of this body of water also liesSao Luis, southeast of Alcantara.  Thisallows for relative closeness in proximity to a major Brazilian port city.  It is still isolated enough, located at a distancefrom any other major cities.  It isneither land locked, nor is it totally surrounded by water.  It is easily accessible to air, train, andwater.  It has deep bays, just as CapeCanaveral does.  This site holds most ofthe advantages of the above-mentioned locales, and little of thedisadvantages.  The weather, clearly animportant factor for a launch site, is also ideal at Alcantara, being clear andcontaining little to no rainfall for most of the year.

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 Æther 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.  However, with an increase in the number oflaunches and missions comes the increased risk that a calamity will ensue.  This fact should be weighted heavily whenconsidering a multi-year, high workload project such as the construction ofÆther.  Added to the need for a base onthe moon to produce raw materials, the construction of Æther will call forheavy workloads involving many risks.By automating or remote controlling many tasks, the cost of constructionwill significantly decrease, since humans require food, air, entertainment, andrest, but machines only require recharging and repair.  While the death of a space constructionworker due to a high-speed collision in space will be cause for much concernand debate, if a robot was in the place of the human, the manufacture of a newrobot will all that would be needed.

 

II.C Exterior Transportation

            Obviously,the robots and workers who will construct Æther will need a way to reach theLagrange point.  Additionally, Æther,the earth, and the moon will eventually form a trading triangle thatnecessitates a fluid transportation system.Transportation in between Æther, the earth, and the moon will be ofvital importance to Æther’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.

 

II.C.1 Space Tethers

            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 toÆther.

 

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.  SSTO systems should be able to economicallydeliver a payload into LEO and be highly reusable, otherwise the cost fortransporting thousands of people across space will be prohibitive.  SSTO systems should also be relatively safe,although accidents are bound to happen; the possibilities for failure would bedecreased if payload capacities were increased, thus reducing the number oflaunches needed.  The SSTO requirement,however, does not rule out maglev-assisted launches, which would greatly aid inlowering costs.

 

II.C.3 Space Elevator

            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.

 

II.D Material Sources

There are three main sources ofmaterials that can be considered for use in constructing Æther: the earth, themoon, and other orbiting bodies such as asteroids and comets.

 

II.D.1 Terrestrial Resources

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.

 

II.D.2 Lunar Resources

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.

 

II.D.2.a Magnetic Separation

            Althoughthe lunar soil is 42% oxygen by weight, it is in fact underoxidized.  Because of this, it contains a highpercentage of iron powder that can be harvested with merely a magnet [ref21].  Magnetic separation will also beimportant in other processing systems, where particles containing iron willneed to be separated from other particles.

 

II.D.2.b Ilmenite Reduction

Iron, oxygen,and titanium can readily be extracted from lunar ores through the hydrogenreduction of ilmenite.  The reaction is:FeTiO3 + H2 --> Fe + TiO2 +H2O.  Oxygen can be derived from the resultingwater through electrolysis, and the hydrogen recycled for furtherreduction.  The process for reducingilmenite with hydrogen starts with the crushing, grinding, and sieving of lunarore; the ore must be reduced to powder with grains smaller than 150μm.  The lunar ore could bevolcanic glass or lunar soil, with volcanic glass being the optimumfeedstock.  The powder is then pouredinto a hermetically sealed crucible, and subjected to high temperatures.  Hydrogen reduction requires temperaturesgreater than 1070 K for complete reduction.Reaction chamber temperatures of 1370 K are required for a turnover timeof 30 minutes; however, the melting of volcanic glass at 1370K-1395K must beavoided since it reduces surface area and hence reaction rates [ref 22].  To achieve these high temperatures, solarheating or electrical heating could be used.A flow of H2 is then maintained over the heated ore, and alsoremoves the water vapor created by the reduction process.  The water vapor is then fed to a hydrolysiscell that would produce hydrogen and oxygen.The hydrogen would be reused as the reduction agent while the oxygenwould be liquefied and stored.  Oxygenweight yields average 3%-4% [ref 22].Further processing of the solid remnants would separate TiO2 andFe from the regolith.  Iron could beretrieved via the use of rotating magnetic drums that pass over a conveyor beltcarrying the remaining powder.  Thetailings would then be deposited in a dumpsite or sent to L5 for use as aradiation shield.

 

II.D.2.c Magma Electrolysis

            Magma electrolysis is an energy intensive processthat requires approximately 13 MWh per tonne O2 [ref 23].  Magma electrolysis produces oxygen byimmersing two electrodes in molten lunar rock and regolith.  Oxygen is then produced at the anode.  Several design parameters are important forthe success of magma electrolysis.  Ifthe magma flow to the electrodes is slow, then large voltages are needed tomaintain acceptable reaction rates.Optimum magma flow could be achieved by buoyancy driven convection, andthe viscosity of lunar magma will have to be accounted for.  Additionally, the presence of gas bubblesand the porosity of the electrodes will influence performance.  Free iron in the magma would collect at thebottom, where it could be trapped, and in the case of anorthite electrolysis,aluminum silicon alloy floats to the top.An advantage of magma electrolysis is that virtually no preprocessing isrequired.

 

II.D.2.d Vacuum Distillation

            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.  Barriers that trap radiation would alsomollify heat loss concerns.  Sincevacuum distillation is a reliable technology, it will be used for materialsprocessing on the moon.

 

II.D.3 Asteroid and Comet Resources

            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 ofÆther.  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.  To maximize gains, an efficient method oftransportation should be considered; solar sails present an extremely efficientmethod of transportation, however, the long transit times dictated preciselybecause of their efficiency necessitates the use of automation to harvest andretrieve asteroid materials.  Thesesolar sail miners would be equipped to network with each other and severalwould be equipped with radio dishes in order to communicate with controllers onÆther.  Others would be equipped withradar and would be networked together to collect and analyze the trajectory ofthe target asteroid.  After levelingwith the asteroid, the automated miners would either go into asteroid-stationaryorbits, or attempt to despin the asteroid.The first step of despinning an asteroid involves attaching two largemasses on ropes and winding them around the asteroid.  Then the masses are allowed to unwind, thus reducing the angularvelocity of the asteroid, since the overall system angular momentum must staythe same.  After the despin, the probesection of the miner would descend from the solar sail and onto theasteroid.  Special care will have to betaken after landing on the surface, since the weak gravity of most asteroidswill mean that violent motions will cause objects to reach escape velocity andnever be seen again.  Methods ofattaching the miner probe to the asteroid may involve penetrators or magnets.  Similarly, during the mining stage, muchmaterial would be lost if there was no mechanism to retain them from going intoorbit.  The easiest way may be to use acanopy that collects all the chips created from drilling and strip mining.  After being filled, the canopy can then beclosed and towed back to Æther using solar sails.  Volatiles will be captured by heating the asteroid or drillinginto volatile reservoirs that would be discovered via ground penetrating radar.

 

II.E Stucture

            Differentshapes were considered as possible shapes of the space colony.  The main contenders were sphere, torus,cylinder.  The torus was the mostefficient, as rotating a sphere would produce only a small strip of habitableland at the expensive of a gargantuan volume.Cylinders also required too much atmosphere, of which 78% needed to beshipped up from earth in the form of nitrogen, thus the torus was selected asit provided the most habitable area per ton of nitrogen.

             Æther technically will be a composite shapecontaining both torus and sphere, with the torus housing the habitats of thecolonists, while the central spheres will house docking facilities, industry,and research.  The torus will measure2000 meters in major radius, and 250 meters in minor radius.  The “floor” of the habitat area would be inthe shape of a cylinder with a radius of 2000 meters and a height of 500 metersinside the torus.  Thus, the volume ofthe torus would be approximately 2.47x109 m3, while thefloor area available would be the area of the side of the cylinder, 2πRhor around 6.28x106 m2.A two-meter thick layer of soil would be placed on top of the primaryfloors so that aesthetic trees and grass can be grown.  Houses would then be anchored to thetitanium floor with bolts.  Anadditional lower floor will be constructed to house CELSS machinery andsupplementary agricultural modules.  Thethree inner spheres will be 270 meters in diameter and will possess a combinedvolume of 8.28x107 m3.Six “spokes” in the shape of cylinders with diameters of 24.5 meterswill connect the torus to the central spheres.

 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 Æther, there will be a point when humanworkers will arrive at Æther and begin to construct parts of Æther.  Before this point, several steps such asproviding radiation shielding, pseudogravity, and an atmosphere would benecessary to ensure the survival of those workers.

 

II.E.1 Structural Material

            The structural integrity of Æther 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 Æther,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.

 

II.E.2 Water Ballast System (WBS)

            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.

 

II.E.3 Thermal Stress

            Sincethe glass of Æther’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

 

II.E.4 Radiators

            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 a passive radiator, heat reaches the finsof the radiator through conduction; in an active radiator, a fluid carries theheat directly to the fins, thus resulting in a radiator that requires lessmass.  However, rapid loss of heatrejection abilities would follow a micrometeorite puncture of an active radiator,since the fluid would expeditiously leak out of the hole.  Shielding the coolant lines can reduce theprobability that a micrometeorite puncture would rob Æther of its coolingcapabilities.  The radiators will be mountedbehind the solar panels, since they conveniently provide shade.

 

II.E.5 Mirrors

            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.

 

II.F Location

            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].  There is no difference between L4 and L5,but for reference purposes Æther will be placed on L5.  The L4 and L5 points are located at a 60degree Earth-Moon-Point angle and the colony would have the same angularvelocity as the Moon does.

 

Life Support

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