We presnet analysis of main objectives and technical challanges which industrial space facilities will have to solve in order to faccilite perspective industrial processes. We suggest possible solutions which seems to be most feasible and efficient from point of view of contemporery technolgy and ecconomy. To do so we design system of modules from which industrial space outpost can be assebmled. The main motivation is to maximaly utilize and promote favourable features of space invironment for industrial processes which are particualarily advantagenous and therefore profitable to conduct in space environemnt. We try to relate our concept of industrial hub to much more common studies of habitats for people living in space. While industial and humane space architecture shares may common aspects such as atempt to provide enclose protected evironment, we think that industrial motivations are much more relevant for space develoment, as it is currently uncertain wheather human presence in space will be required and economically justified.
Collonization of space is often considered as great technical and economic challenge with rather ideological justification (i.e. expansion of humanity to space). For hunderts of years the topic provides ground for adventurous sci-fy storries, social utopias as well as architectectural and other artistic visions of building modern version of Atlantis or Elysium. The basic plot of these visions is to achieve magnificient and noble goals at the cost of huge effort and capital investemnt.
However for self-sustained space colonization driven predominantly by privite sector the reasoning must be reversed. We have to consider only such bussineses which are profitable on purely economical basis with return on investment in reasonable time period. In other words we search for such procesess or egineering projects which are actually in a sense easier to conduct in space than on the Earth. Commonly asteroid mining is reffered as such industry, due to abundant presence of e.g. platinum group metals (PGMs) and certain precious semiconductor elements in relatively high concetration. However, due to large development and capital cost as well as considerable risk involved economic feasibility of space economy driven prurely by mining or rare resources sold on Earth is dubious. Asteroid mining can be perhaps economically justified only when majority of the mined resources is consumed directly in space, where cost o raw material is considerably higer due to high transport cost of the material from Earth. Some of the in-space demand on raw materials can be justified by service of current facilities on Eath orbit such as comunication and sciencetific satailites and ISS, or perhaps of future sciencetific or recreational facilities and sciencetific missions. Nevertheless, such demant is relatively limited and from large part dirctly or indirectly dependent on govermental support. Really self-sufficient, exponetitally growing space ecconomy must be therefore based on industrial processes conducted in space.
While PGMs and other minaral resources alone probably cannot motivate rage scale industrialization of space, there is huge demand some features of space environment which are scarce on Earth. This involve either physical aspect such as vacuum, cryogentic temperatures, microgravity, un-occluded solar light, large un-interupted building space as well as socio-political aspect such as lack of enviromental protection and govermental control. All these features of Earth environmnet consideraly interfere and complicate many hi-tech industrial processes. Perhaps better to say, most favourable features of space environment are due what it lack rather than what it provides. Lets us now discuss these features of space environemnt in detail together with particular industrial processes which can make advatages of it.
We briefly discuss several particular technological processes in order to identify demands imposed of space architecture which should facilitate them, and to support assumption what it is ecconomically advantagenous to conduct these processes in space. Technological details of those processes as well perticular realization of correspoding technolgical production facility in space is beyond the scope of this paper. We rather assume that industrail architecture (MISO) discussed in this paper will provide protected and controled space for 3rd party companies, and that choice and realiation of paticular facility or technology is on them. This allows us to discuss more general features of industrial space architecture which are incommon fto broader variety of technologies.
Radiation mostly in form of protons and light atom nuclei is harmful not only to life, but also to electronics and other devices. The damage mechanism s (i) itroducing defect into material and (ii) launching electric avalanches discharges. Deffects are especially problatic for technologies and materials which realy on ideal crystaline structure. The discharges endanger any devices with high gradients of electric field, which include both microscopic low-voltage devices such as computer chips as well as macroscopic high-voltages devices such as capacitors, marx generators and radiofrequency cavities of accelerator, electron microscopes and other electron and ion beam optics.
There are two basic approaches to radiation shielding: (i) using thick layers of raw material such as water or regolith (ii) using magnetic fields. The obvious disadvantage of using thick shield is enormous weight of such shield. This concern is very serious in case of manuevering space craft, but in case of static facility it is much less of a problem. Still the ammount of material required to build large enclosed room protected by thick shield may be limiting factor. For a spherical room of radius 100-1000m covered by 1m of regolith thi accounts for 0.7-75 milion tons which is comparable to total mass of smaller asteorides.
While the raw material is abundant and cheap, the mining, processing and anchoring in huge quntities is challanging. Let us disscuss technologies with lowest per-mass cost.
In order to reduce total mass of shielding magnetic deflection of most energetic particles, which would considerably reduce thickness of the raw material layer. For example if from orginal spectrum of up to 250 MeV protons are removed or slowed all particles above 100MeV, the penetration depth is reduced from 400mm to 50mm, which means 8x lighter shield. The main problem of this approach is that perticles of high energetic cosmic radiation comes from all direction, and even those originating from sun (e.g. from sloar flares) are rather badly collimated. In case of well colimated particle beam it would be sufficient to deflect the beam by small angle, which can be done using relatively weak magnetic field positioned far in front the facility. In case of randomly distributed incident directions the facility must be immersed in the center of the field and the field must be strong enough to deflect the particles by 60-180 degrees. This means that gyro radius of the particles in the field should be smaller than the distance between onsed of field and outer boundary of the protected room. It is also required that in the area between the onset of field and shield is empty, as any solid object could scatter the particles toward the facility.
Massive radiation shilds would certainly provide good protection also against micrometeorites. The only problem remains protection of those facilities which are not covered by radation shield and minimization of ware of radiation shield.
Cryogenic technolgoies based on super-conductivity, super-fluidity, and other quantum-coherent states comprise most attractive opportunities for space ecconomy. While temperature of outer space is approximately given by temperature of background radiation (2.73K) the equlibrium temperature of natural bodies at NEA or in asteroid belt is not sufficiently low for those cryogenic applications due to sun radiation. There are nevertheless very efficient measures how to reduce equilibirum temperature of properly designed artifical bodies.
A navie prospect would be to situate cryogecic industrial facility into shadow of celestial body (planets or asteoriedes). In that case it should be considered that even the dark side of shielding body has temperature considerably higer than background radiation. Thus the cryogenic facility must be situated in sufficient distance from the shielding body to minimize capture thermal radiation radiated from the shield. Also the facility must be kept by propper position with respect to shielding body by active manuevering, perhaps using ion thrusters. In case of planetary heat shield only lagrange point L2 is feasible position. Such constrains on position of facility with respect to masive shielding body may limit access to raw materials, which would be mined from that body or imported from other body. For example in case of asteroide it would be advantagenous to place facility as close as possible.
For these reasons natural shield may be quite inpractical in comparision to lightweight artificial heat shield made of thin metalic foil. Artificial shiled can be designed to optimally fullfil all industrial requirements of minal weight, and temperature as well as optimal placement with respect to raw resources and orbital trade-rotes. The heat shiled tipically comprise of tilted planes (sails) separated by larger distace which fill as solid angle in direction from sun (i.e. the sail closest to sun is largest). The side directed toward the sun is always highly reflective to minimized ammount of captured radiation. The equlibrium temperature of the sail is further reduced by tilt under sharp angle which increase ratio between are from which heat is radiated to outer space and the crossectional area for sun irradiation. Larger spacing between the sails ensure that only small percentage of heat radiated from sail closer to sun is captured by the sail behind. Major optimization criterial for the heat shield are reduction of weight for given temeprature gradient. Theoretically the most efficient way is to prolong spacing between sails, since the weight of structural scafold on which sails are fixed is very small since the scaffold does not have to bear almost any force. Due to limits of building technology and impracticality of manipulation of fragile long girders the total lengrh of shield should be perhaps limited to max. several kilometers.
Active heat-pumps and radiators - By passive shiled equlibirum temperature can be efficiently reduced toward tens of kelvins. For even lower temperatures passive cooling by irradiation is extremely inefficient ($P \propto T^4$) - especially when heat is generated inside cryigenic facility by ongoing industrial processes. Since efficiency of heat pump at criogenic tempeatures is fundamentally limited by Carnot-cycle the waste heat which should be dumped to space by radiators will be typically orders of magnitude higher than energy disipated in the cryogenic process. It is crucial to ensure to minimize radiative cupling between heat shields and radiators and to ather structural components of the ships, otherwise radiative cooling would be inefficient. Even worse would be scattering of some termal radiation from shiled and radiators toward cryogenci area. Radiators should be aligned in paralel with zero cossection toward to sun.
Heat scattering on other components - Some components should be situated in place and oriented in direction which can cause scattering either dirct solar radiation or indirect termal radiation from heat shields and cooling radiators. For example solar arrays constitue large area which has to be irradiated by sun as much as possible. If they would be situated in wrong position (behind or to the side of cryogenci are), they would scatter huge amout of heat to the back-side of the shiled and to the radiators. Therefore only feasible position of solar arrays is in front of solar shild, which may however complicate transfer of generated electricity and services. Mass drivers have to be oriented tangentially to orbit (of sun) in order to efficiently assist orbital transfer in asteroid belt - therefore cannot be hidden behind heat shield. If they are placed in front of the heat shield it inertial of the cryogenic facility is not utilized to absorb recoil of acceleration of vessels. Also the transport of cargo between cryogenic facility and mass driver on distance of hudert meters or kilometers arround the shild would be complicated. Also the asteoride from which the facility my mine raw material scatter light and theat in various direction. Even if the body is hidden behind sunshade, it will radiated heat for hunderts of years due to its large heat capacity. Therefore such body must be situated in front of shiled, and material must be transported around the shield.
due to large scale industrial facilities (such as heat shileds or mass drivers) iterdepenent industrial processes will be separated by considerable distances. We have to ensure efficient transport of comodities, components and products as well as of workforce (robots) between those nodes.
While in initial phase of space-industrialization spacecrat should be able to arrive and leave outpost without any assistance, in later phases it will be probably advantageneous to supplent the station by facilities such as mass-drivers and sky-hooks for acceleration and de-acceleration of transport vessels. These faccilities will considerably reduce ammount of consumed propelant by substituing its inertial mass by the mass of the whole facility.
Composites
Metalic
