II. Construction

            The construction of Æther will call for unprecedented cooperation both on earth and in space, as massive funding and efforts will be required.  The first problem that came to mind was the establishment of a launch site capable of handling the massive traffic loads necessary.  Locating a materials source ready for large-scale utilization was also of concern, since Æther will be the largest 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, and nutritional needs.

            The first stage of construction will be the establishment of a launch site, then robotics miners would be sent to the moon to establish a lunar base consisting of launching, landing, and processing facilities.  There automated machinery would harvest and process lunar materials, stockpiling necessary resources. Then the inner spheres would be built in orbit around the moon, using materials launched from the lunar surface, and then propelled to L5 using ion thrusters or a magnetic driver. Thereafter, automated workers at L5 would catch materials sent to L5 from the moon, and use them to construct the remaining components of Æther.  Human participation in the construction should be delayed as much as possible, in order to keep down costs, but CELSS machinery would be shipped up from earth along with the human workers so that they can survive in the space environment.

 

II.A Launch Site

Just as essential as a well coordinated project in the sky is the equal efforts of resources, minds, and power on the ground. A monumental station such as Æther calls for a sister base on earth.  In order to complete and manage the extensive building and maintenance of the space station, we feel the requirement for a land base here on earth. This land station requires three main characteristics.  The first is clearly the ability to accommodate resources, personnel, and overall international support by sea and air.  The next requirement is a close proximity to some sort of major metropolitan area, yet still remaining somewhat distant.  Such closeness offers many advantages.  This prevents the project from total seclusion from society, as well as the ports of sea and air that also lay close by.  The metropolitan area gives a large pool of potential employees of the massive project.  The distance from such a major metropolitan area reduces potential for disaster in case of launch mishaps.  Natural factors, such as weather, play in as crucial aspects of the decision.

Precedence for selection of launch sites for projects of this scale can be found in the Apollo program.  NASA’s air force team put out information on their choices on possible launch cites.  They considered candidates from a panel of 8 United States locations.  They were, Cape Canaveral; offshore from Cape Canaveral; Mayaguana Island in the Bahamas; Cumberland Island, Georgia; a mainland site near Brownsville, Texas; White Sands Missile Range in New Mexico; Christmas Island in the mid-Pacific, south of Hawaii; and South Point on the island of Hawaii.  By breaking down the advantages and disadvantages of these locations, a better view of what is preferable for a launch site can be discovered.  To begin with, one barrier to most of these sites was the cost of purchasing land. In this project however, it wouldn’t be a limiting factor, but there were many other specifications, which can be deduced from more analyzation.  The White Sands area was deemed cheapest to develop and maintain, although its landlocked location was something that would inhibit and restrict goods from coming by sea, which is often the cheapest long transportation method.  The island sites of Mayaguana, Christmas, and Hawaii, were ruled out for the shear extensive cost over the other proposed sites. These islands also posed severe problems of logistics.  Such an isolated and small region of land would complicate building, launching, and maintenance.  The Brownsville site brings up the problem of relative proximity to large and densely populated areas.  Thus the ideal site would be close to the sea, close to an inexpensive energy source, and isolated from population centers, but close to key suppliers.  An additional criteria is for the area directly eastward of the launch site to be uninhabited, since most launches will be eastward to take advantage of the earth’s rotation.

With theses needs and specifications in mind, an ideal launch site could be developed in Alcantara, Maranhao in Brazil. Alcantara is located at 2.24º S and 44.24º W.  Actually, there is a small development of an already existing launch site at this location.  For this project, all that would be needed would be to further expand the current base.  Alcantara is a small city, of a population less than 20,000 that lays on the Baia de Sao Marcos.  On the coast of this body of water also lies Sao Luis, southeast of Alcantara.  This allows for relative closeness in proximity to a major Brazilian port city.  It is still isolated enough, located at a distance from any other major cities.  It is neither land locked, nor is it totally surrounded by water.  It is easily accessible to air, train, and water.  It has deep bays, just as Cape Canaveral does.  This site holds most of the advantages of the above-mentioned locales, and little of the disadvantages.  The weather, clearly an important factor for a launch site, is also ideal at Alcantara, being clear and containing little to no rainfall for most of the year.

Some of the facilities that would be built or expanded include: living quarters for participants in the project, a command center for monitoring of launches and construction, radio dishes for communication, an airport to accommodate supplies and people coming in by air, a port to facilitate large shipments, and work areas where the space ships would be readied.

 

II.B Automation/Remote Control

            Heavy automation will be key to the success of the construction and maintenance of Æther at a low cost in terms of money and human lives.  Fortunately, except for a few unfortunate incidences, the American space program has been relatively well-shielded from the dangers associated with human spaceflight.  However, with an increase in the number of launches and missions comes the increased risk that a calamity will ensue.  This fact should be weighted heavily when considering a multi-year, high workload project such as the construction of Æther.  Added to the need for a base on the moon to produce raw materials, the construction of Æther will call for heavy workloads involving many risks. By automating or remote controlling many tasks, the cost of construction will significantly decrease, since humans require food, air, entertainment, and rest, but machines only require recharging and repair.  While the death of a space construction worker due to a high-speed collision in space will be cause for much concern and debate, if a robot was in the place of the human, the manufacture of a new robot 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 the Lagrange point.  Additionally, Æther, the earth, and the moon will eventually form a trading triangle that necessitates a fluid transportation system. Transportation in between Æther, the earth, and the moon will be of vital importance to Æther’s economy as goods and raw materials will need to be able to be flow freely to and from each of the trading triangle’s vertices.

 

II.C.1 Space Tethers

            Space tethers utilize the momentum or electrodynamic transfer to propel objects through space.  Momentum transfer can be visualized by having two satellites connected by a tether, with one of the satellites 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 own kinetic energy.  This slingshot motion arises since the satellite with a lower orbit has a faster tangential velocity than the satellite with the higher orbit. Thus when the higher satellite is released it will embark on a more elliptical orbit than the one it was previously one.  A similar tradeoff between kinetic energy and electrical energy also 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 Æther.

 

II.C.2 Single Stage to Orbit (SSTO)

            Achieving SSTO 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 economically deliver a payload into LEO and be highly reusable, otherwise the cost for transporting 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 be decreased if payload capacities were increased, thus reducing the number of launches needed.  The SSTO requirement, however, does not rule out maglev-assisted launches, which would greatly aid in lowering costs.

 

II.C.3 Space Elevator

            Another interesting concept is that of a space elevator.  Built from geosynchronous orbit, the space elevator would be above the same place on earth at all times.  A counterweight that extends just as far radially outwards from earth would be needed to ensure that the elevator does not fall out of orbit because of its weight and crash into earth.  Such an elevator would require ultra-strong materials in order to be economically feasible, but would catalyze growth of space colonization; frequent, cheap, non-polluting launches would be possible.

 

II.D Material Sources

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

 

II.D.1 Terrestrial Resources

Generally utilization of terrestrial resources should be kept to a minimum since the transportation costs are prohibitively high. However, some elements, such as nitrogen, cannot be found elsewhere and must be shipped up from Earth.

 

II.D.2 Lunar Resources

Because of its weak gravity and n .onexistent atmosphere, the moon presents a more economical source of materials.  These materials can be easily transported to L5 using magnetically-powered mass drivers, in which the payload is given momentum by a bucket accelerated by strong magnetic fields.  The packet would then be caught at 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 and nonmetals such as titanium [ref 1]. Different methods can be utilized for obtaining these resources.

 

II.D.2.a Magnetic Separation

            Although the lunar soil is 42% oxygen by weight, it is in fact underoxidized.  Because of this, it contains a high percentage of iron powder that can be harvested with merely a magnet [ref 21].  Magnetic separation will also be important in other processing systems, where particles containing iron will need 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 hydrogen reduction of ilmenite.  The reaction is: FeTiO3 + H2 --> Fe + TiO2 +H2O.  Oxygen can be derived from the resulting water through electrolysis, and the hydrogen recycled for further reduction.  The process for reducing ilmenite with hydrogen starts with the crushing, grinding, and sieving of lunar ore; the ore must be reduced to powder with grains smaller than 150 μm.  The lunar ore could be volcanic glass or lunar soil, with volcanic glass being the optimum feedstock.  The powder is then poured into a hermetically sealed crucible, and subjected to high temperatures.  Hydrogen reduction requires temperatures greater than 1070 K for complete reduction. Reaction chamber temperatures of 1370 K are required for a turnover time of 30 minutes; however, the melting of volcanic glass at 1370K-1395K must be avoided since it reduces surface area and hence reaction rates [ref 22].  To achieve these high temperatures, solar heating or electrical heating could be used. A flow of H2 is then maintained over the heated ore, and also removes the water vapor created by the reduction process.  The water vapor is then fed to a hydrolysis cell that would produce hydrogen and oxygen. The hydrogen would be reused as the reduction agent while the oxygen would be liquefied and stored.  Oxygen weight yields average 3%-4% [ref 22]. Further processing of the solid remnants would separate TiO2 and Fe from the regolith.  Iron could be retrieved via the use of rotating magnetic drums that pass over a conveyor belt carrying the remaining powder.  The tailings would then be deposited in a dumpsite or sent to L5 for use as a radiation shield.

 

II.D.2.c Magma Electrolysis

            Magma electrolysis is an energy intensive process that requires approximately 13 MWh per tonne O2 [ref 23].  Magma electrolysis produces oxygen by immersing two electrodes in molten lunar rock and regolith.  Oxygen is then produced at the anode.  Several design parameters are important for the success of magma electrolysis.  If the magma flow to the electrodes is slow, then large voltages are needed to maintain acceptable reaction rates. Optimum magma flow could be achieved by buoyancy driven convection, and the viscosity of lunar magma will have to be accounted for.  Additionally, the presence of gas bubbles and the porosity of the electrodes will influence performance.  Free iron in the magma would collect at the bottom, 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 is required.

 

II.D.2.d Vacuum Distillation

            Vacuum distillation utilizes the different boiling points of ore components to separate them.  Ore is placed inside a vacuum chamber and then heated; the evaporated components are then collected during different temperature periods. This relatively easy process can be replicated on a large scale and can produce aluminum as well as iron and oxygen. Because of its simple and robust nature, vacuum distillation relies on facilities that are not easily damaged and can be easily furnished [ref 24].  The heat energy requirements for vacuum distillation can easily be met through waste heat recycling from other lunar processes or could be collected from the solar flux.  Barriers that trap radiation would also mollify heat loss concerns.  Since vacuum distillation is a reliable technology, it will be used for materials processing on the moon.

 

II.D.3 Asteroid and Comet Resources

            Asteroids and comets are known to contain vital substances such as water, platinum group metals, iron, nickel, as well as other valuable ores.  Of course, the composition of asteroids varies, but there are many valid targets, both small and large, that would be within close reach of Æther.  In the case of small (less than 3 meters) asteroids, they could possibly be retrieved in their entirety, while mining would be required to extract materials from larger asteroids.  To maximize gains, an efficient method of transportation should be considered; solar sails present an extremely efficient method of transportation, however, the long transit times dictated precisely because of their efficiency necessitates the use of automation to harvest and retrieve asteroid materials.  These solar sail miners would be equipped to network with each other and several would be equipped with radio dishes in order to communicate with controllers on Æther.  Others would be equipped with radar and would be networked together to collect and analyze the trajectory of the target asteroid.  After leveling with the asteroid, the automated miners would either go into asteroid-stationary orbits, or attempt to despin the asteroid. The first step of despinning an asteroid involves attaching two large masses on ropes and winding them around the asteroid.  Then the masses are allowed to unwind, thus reducing the angular velocity of the asteroid, since the overall system angular momentum must stay the same.  After the despin, the probe section of the miner would descend from the solar sail and onto the asteroid.  Special care will have to be taken after landing on the surface, since the weak gravity of most asteroids will mean that violent motions will cause objects to reach escape velocity and never be seen again.  Methods of attaching the miner probe to the asteroid may involve penetrators or magnets.  Similarly, during the mining stage, much material would be lost if there was no mechanism to retain them from going into orbit.  The easiest way may be to use a canopy that collects all the chips created from drilling and strip mining.  After being filled, the canopy can then be closed and towed back to Æther using solar sails.  Volatiles will be captured by heating the asteroid or drilling into volatile reservoirs that would be discovered via ground penetrating radar.

 

II.E Stucture

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

             Æther technically will be a composite shape containing both torus and sphere, with the torus housing the habitats of the colonists, while the central spheres will house docking facilities, industry, and research.  The torus will measure 2000 meters in major radius, and 250 meters in minor radius.  The “floor” of the habitat area would be in the shape of a cylinder with a radius of 2000 meters and a height of 500 meters inside the torus.  Thus, the volume of the torus would be approximately 2.47x109 m3, while the floor area available would be the area of the side of the cylinder, 2πRh or around 6.28x106 m2. A two-meter thick layer of soil would be placed on top of the primary floors so that aesthetic trees and grass can be grown.  Houses would then be anchored to the titanium floor with bolts.  An additional lower floor will be constructed to house CELSS machinery and supplementary agricultural modules.  The three inner spheres will be 270 meters in diameter and will possess a combined volume of 8.28x107 m3. Six “spokes” in the shape of cylinders with diameters of 24.5 meters will connect the torus to the central spheres.

 fig. 2.1

The torus would be made out of titanium plates welded to titanium ribs in the form of circles rotated about the center of the torus.  Initially, these plates would be very thin, but they would be strengthened after vacuum deposition techniques add more titanium to them.  Using thin plates is ideal, since titanium is very strong and hence hard to work with, reducing the thickness would mean that less powerful tools could be used to create the structure. The spheres would also be made using similar construction techniques. 

Although automated workers would build most of Æther, there will be a point when human workers will arrive at Æther and begin to construct parts of Æther.  Before this point, several steps such as providing radiation shielding, pseudogravity, and an atmosphere would be necessary to ensure the survival of those workers.

 

II.E.1 Structural Material

            The structural integrity of Æther will depend on the materials that constitute it.  Due to their abundances on the moon, the metals and alloys of titanium, aluminum, and iron were prime candidates.  Titanium was eventually chosen as the material of choice since it has a low coefficient of thermal expansion, one of the highest strength to mass ratios among the metals, 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.

            Titanium alloys should also be considered, titanium has three classes of alloys: Alpha, Alpha-Beta, and Beta.  Alpha alloys are not heat-treatable and are weldable, they also have excellent mechanical properties at cryogenic temperatures. Alpha-Beta alloys are heat-treatable, which strengthens the material by a sudden drop in temperature, and also have higher tensile strength than Alpha alloys.  Beta alloys can also be heat treated, and have excellent creep resistant properties.

 

II.E.2 Water Ballast System (WBS)

            To maintain proper rotation, a water ballast system will be incorporated into the structure.  This system will ensure that the colony’s center of mass closely correlates with the actual center of the torus.  Compromising of storage tanks interconnected with electronically controlled pumps, the WBS can also serve as water storage and additional radiation shielding.

 

II.E.3 Thermal Stress

            Since the glass of Æther’s sky will be subjected to a 14-hour day, 10-hour night sunlight schedule, it will experience expansions and contractions as it heats up and cools down.   Thermal stress played a major role in the materials selection process, but materials selection alone cannot prevent metal fatigue. Instead, using a multiple hull system like those found in submarines should combat both metal fatigue and enormous pressure differences at the same time.  The multiple hulls combined with the radiational shielding should insulate the inner metals and the multiple hulls provide superior strength to the torus walls.

 fig. 2.2

 

II.E.4 Radiators

            The excess heat caused by the CELSS, manufacturing, and research processes will have to dissipate their heat in some way.  Heat rejection can be achieved by exhausting coolant into space, but this method is mass-expensive when compared to radiator methods.  Radiating the heat into space as radiation is the most commonly used method of rejecting heat. Radiators operate on either passive or active principles.  In a passive radiator, heat reaches the fins of the radiator through conduction; in an active radiator, a fluid carries the heat directly to the fins, thus resulting in a radiator that requires less mass.  However, rapid loss of heat rejection 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 the probability that a micrometeorite puncture would rob Æther of its cooling capabilities.  The radiators will be mounted behind the solar panels, since they conveniently provide shade.

 

II.E.5 Mirrors

            In order to provide the requisite illumination needed, a method to propagate light so that it seems to come from the “sky” of the torus will have to be utilized.  One possible method is to use artificial lighting, however, this system would not be ideal since incandescent bulbs draw too much power and possesses a “harsh” light, while fluorescent lights possess a flicker that would contribute to the artificiality of the colony.  A LED-based lighting system may work, but would prove costly in terms of manufacturing and maintenance.  Thus, mirrors that reflect light into the torus will be considered for illumination.  A simple configuration consisting of a circular mirror with a diameter of 3.35 km angled at 45° to the plane of the torus reflecting light onto a section of a conical mirror also angled at 45°.

 fig. 2.3

The secondary mirror can be thought of as a surface of revolution, or the sides of a cone with bases of 2.35 km and 1.81 km.  It will be constructed of an aluminum framework containing glass inserts coated with reflective metal.  The individual panels can be rotated by electric motors, thus providing a way to create the 14-hour sunlight, and 10-hour night cycle.

 

II.F Location

            A particular orbit, that could be stable enough for the space colony, is the so-called Lagrangian Orbit, named after the French mathematician Joseph-Louis Lagrange. A Lagrangian orbit is the orbit of an object located at a Lagrangian point, or also libration point. In such an orbit the body will be in a station-keeping position, that is keeping it in orbit at the cost of less maneuvers. There are 5 Lagrangian points for the two body system Earth-Moon, three of which L1, L2 and L3 are gravitationally unstable These are points where the body is in a balance, because the gravitational pulls of the Earth and Moon cancel each-other. However, even small perturbations, such as solar wind will cause the body to lose its unstable equilibrium and plunge into chaotic motion, which will have to be constantly corrected with thrusters [ref 45]. Unlike the other three points, putting the colony in points L4 and L5 will make 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 be actually wobbling around the Lagrangian point, which is practical for putting bigger 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 60 degree Earth-Moon-Point angle and the colony would have the same angular velocity as the Moon does.

 

Life Support

Table of Contents