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Recommendations and Conclusions

8. Recommendations and Conclusions

In the course of the 10-week study, it became apparent that there are many aspects of the design of a space colonization project for which the necessary data are not available. Many are critical to the design so that, in the absence of firm data, conservative assumptions had to be made. This forced the overall design in a conservative direction with considerable weight, size and cost penalties compared with what might be an optimum design.


Before a detailed practical design of a space colony can be undertaken, the following subjects must be researched to fill in the gaps in current design-related data.

  1. Acceptable Radiation Dose. The 0.5 rem per yr radiation dose is achieved in this design study by accepting a considerable penalty in weight and system complexity. This dosage rate is the upper limit allowed for the general population in the United States and is chosen arbitrarily as a conservative measure. Extensive biological testing should be undertaken to establish a realistic dose limit taking into consideration the colony's population distribution and the scenarios for habitation of the colony. The effect of radiation on agricultural specimens also needs study to assure stable food supplies.
  2. Acceptable g Levels. The physiological effects of zero-g are serious for long-duration exposure in space. For this reason and since little is known about exposure at intermediate g levels, 1 g was chosen as the design standard. The 1-g choice has significant influence on the design and may be unnecessarily high. An examination of physiology under partial g is required in the Spacelab and subsequent space station missions to determine the minimum g value for which there are no serious long-term physiological effects upon humans.
  3. Maximum Acceptable Rate of Habitat Rotation. The rate of rotation required to achieve the desired pseudogravity has substantial impact on the design. Since the g-level and rate of rotation determine colony dimensions to a large extent (and thus the weight) determination of an acceptable rate of rotation is important. While it is difficult to test human vestibular functions in a realistic way on Earth, it is critical that a better understanding of the subject be obtained by studies both on Earth and in space.
  4. Closure of the Life Support System. The critical role of agriculture in providing food and regenerating the atmosphere in the colony requires that it be undertaken with utmost confidence and understanding. The components of the agricultural system require study to determine their detailed characteristics and their suitability. While possible in theory, large living systems have never been operated in a closed loop. First on a small scale, and finally on a large scale, complete closure of a demonstration life support system should be accomplished before colonization begins. The requirements for microbial ecology need to be studied.
  5. Intensive Agriculture. The support of the colony's inhabitants on the agricultural output from 150 acres is based on highly intensive photosynthetic production, beyond that realized to date. The exact enhancement of yields from lighting, increased carbon dioxide, and regular irrigation needs to be determined, and actual prototype farming needs to be conducted prior to closed life support system tests.
  6. Methods of Radiation Shielding. The requirement for 10 million tonnes of passive shielding resulted from uncertainty in the effectiveness and the complications of active shielding techniques. In particular, it is recommended that studies be undertaken with the plasma shield to achieve the acceptable dose with a workable system.
  7. Productivity in Space. The size, cost, and schedule for colony (and SSPS) construction are critically dependent upon the number of workers and their productivity. Terrestrial examples of worker productivity may be unrealistic for colony construction. Significantly greater definition of worker productivity is required for the colony design and should be accompanied by actual experimentation in space to derive realistic quantitative data.
  8. Processing of Lunar Surface Material. The aluminum and titanium extraction and refining processes suggested by this study are novel and largely unstudied because of the unusual nature of the lunar ores compared to terrestrial ores. The need to develop these processes in the laboratory, the terrestrial pilot plant, and eventually the space pilot plant is critical to the success of the program. Efficient production of glass from lunar rock is also required under the limitation of minimal additives. Physical and optical properties of the resulting glass need to be determined.
  9. Lunar Mass Launcher. The efficient transfer of lunar ore to a space processing facility is essential to the success of the space colonization concept. Alternative methods (such as the gas gun) need further study so that a careful design analysis can be made of the entire subsystem. A scaled prototype should be tested. More detailed engineering analysis of the baseline system is required.
  10. Mass Catcher. The location and operational principle of the mass catcher are critical to space colonization and weakly substantiated in this study. The entire subsystem needs much greater study and eventually testing in space.
  11. Minimum Acceptable Partial Pressure of Nitrogen and Oxygen in the Space Colony Atmosphere. To minimize the quantity of nitrogen brought from Earth, the problems resulting from oxygen-rich atmospheres need detailed study to determine the minimum amount of nitrogen required in the atmosphere.
  12. Satellite Solar Power Station Design. This study did not focus on the details of the SSPS design. The method of energy conversion (photoelectric vs. thermalmechanical) needs to be selected on the basis of detailed comparative study and perhaps on the basis of fly-off testing on small-scale prototypes. The methods of construction need careful examination from the viewpoint of efficient material and manpower utilization.
  13. Transportation System. In addition to the main transportation elements (the HLLV, the mass launcher, and mass catcher), the rotary pellet launcher and the ferrying ion engines require research and development. While the HLLV is proposed within the current baseline, even more advanced vehicles with larger payloads and lower launch costs would be of enormous benefit to the space colonization program at any time in the program.
  14. Environmental Impacts. The frequency of launches needed and the products from rocket combustion need to be studied to determine the impact upon the Earth. The high power microwave beam from the SSPS may have effects on certain biota in or near the beam, and rf interference with communications, terrestrial navigation and guidance systems, and radio astronomy should be examined.
  15. Human Physical, Psychological, Social, and Cultural Requirements for Space Community Design. The diversity of options and the uncertainty of absolute requirements for various human factors require considerable study, elaboration, and agreement. Factors governing design include habitat configuration, efficient utilization of area, methods and diversity of construction, visual sensations, and colonist activities. All need to be thoroughly evaluated.
  16. Political, Institutional, Legal, and Financial Aspects of Space Colonization. The space colonization effort is of such magnitude that it requires careful analysis with respect to organization and financing. For this analysis competent, realistic, and thorough study is needed. National versus international, and governmental versus private or quasi-governmental organization, requires study and evaluation. The operational organization for space colony implementation is of sufficient magnitude to merit this study being made very early in consideration of a program to establish human habitats in space.
  17. Economic Analysis of Space Colonization Benefits. A more sophisticated analysis is needed to determine whether the benefits of space colonization do or even should justify the costs. In particular, studies are needed which compare space colonization and SSPS production with alternate methods of producing electricity.

  18. Additional Topics for Later Study. Space colonization in general covers such a wide spectrum of diverse topics as to allow many fruitful studies with varying depths of analysis. Examples of subjects that need to be investigated are:

    a. Method of immigrant selection. 
    b. Effect of "deterrestrialization" of colonists. 
    c. Effects of large-scale operations on the lunar, cislunar, and 
       terrestrial environment, and effects on the solar wind. 
    d. Disposal of nuclear waste on the lunar surface. 
    e. Alternate colony locations (such as lunar orbit, L2, LEO inside Van
       Allen belt, free orbit, near asteroids, Jupiter orbit). 
    f. Detailed metabolic requirements (input and output data) for plants 
       and animals. 
    g. Suitability of condensed humidity for human consumption, for fish, 
       and for crop irrigation. 
    h. Recycling of minerals from waste processing. 
    i. Production of useful products from plant and animal processing 
    j. Characterization of trajectories from lunar surface to the various 
       loci of potential activity. 
    k. Analysis of the potential foreign market for electric power. 
    l. Quantitative analysis of nonelectrical space benefits, for example, 
       benefits from production of communication satellites in space. 
    m. Development of alternative mission profiles which increase emphasis 
       on SSPS production or on colony production. 
    n. Effect of an established space colony on future space missions, their 
       feasibility and cost.  
    o. Application of learning curves to space colonization. 
    p. Ecological balance within the colony, microbial and insect ecologies 
       (including role of nitrogen fixation). 
    q. Chemical processing with nonaqueous or even gaseous techniques. 
    r. Determination of the proper safety margins for various systems. 
    s. Detailed design of windows and their optical properties. 
    t. Dynamics of atmospheres in rotating structures. 
    u. Tools and techniques for working in zero g. 
    v. Rendezvous with asteroids. 
    w. Remote assembly of large structures. 
    x. Halo orbits. 
    y. Description of everyday phenomena in a rotating environment. 
    z. Fire protection. 
   aa. Synthetic soils.
   bb. Space manufacturing. 
   cc. Extension of economic geography to space. 
   dd. Adaptable and evolutionary aspects of habitat design. 
   ee. Atmospheric leakage rates and gaskets. 
   ff. A zero-g colony. 
   gg. Studies of work organization in remote locations. 
   hh. Studies of social and economic interdependence among communities in 
       remote locations with respect to transportation. 
   ii. Studies of functional division of labor within human communities. 
   jj. Study of methods for transporting and storing gaseous materials such 
       as hydrogen and nitrogen in various chemical forms such as ammonia, 
       ammonium salts, or other compounds. 
   kk. Space viticulture and enological techniques. 
   ll. Heterogeneity as a desired or required characteristic. 
   mm. Rotation of habitat within the shield. 
   nn. Colony governance. 
   oo. Requirements for interior illumination. Is sunlight really needed in 
       living and even agricultural areas? 
   pp. A detailed list of colonist activities and the land area usage 
       dictated by analysis of interior illumination needs. 
   qq. Composite material fabrication techniques in space. 
   rr. Construction of lunar mass launcher from lunar materials using 
       bootstrapped pilot plants. 	
   ss. Detailed study and list of materials to be imported from Earth to 
       support the everyday needs of the colony. 
   tt. Extrusion techniques for space. 
   uu. Alternative diet components. 
   vv. An acceptable name for the first colony. 


A principal recommendation of this summer study is that a major systems study be made of space industrialization and space colonization. In addition, it is recommended that the following space ventures be undertaken as necessary preludes to space colonies.

  1. Continue development of the space transportation system (shuttle) and of Spacelab.
  2. Start development of the shuttle-derived Heavy-Lift Launch Vehicle.
  3. Construct a large space laboratory for placement in low-Earth orbit in which experiments necessary to space colonization can be carried out.
  4. Establish a lunar base to explore and to test for the availability of lunar resources.
  5. Send an unmanned probe to the asteroids to determine their chemical composition.


Space colonization is desirable because of the hope it offers humanity. A sense of the limits of Earth has been heightened in recent years by growing awareness of the delicate ecological balance of the planet, its finite resources and its burgeoning human population. The sense of closure, of limits, is oppressive to many people. In America, growth has been the vehicle of rapid and often progressive change; it has been the source of opportunity for millions of people and has played an important role in fostering American democracy and political freedoms. To have opportunities restricted and to be forced to devise political institutions to allocate equitably, resources insufficient to meet demand, are unpleasant prospects. Space offers a way out, with new possibilities of growth and new resources. Space offers a new frontier, a new challenge, and a hope to humanity, much as the New World offered a frontier, a challenge, and a hope to Europe for more than 4 centuries.

Space also offers riches: great resources of matter and energy. Their full extent and how they might be used are not altogether clear today. It is likely that solar energy collected in space, converted to electricity, and beamed to Earth would be of great value. The manufacture of the satellite power stations to bring this energy to Earth and of other commercial activities that use the abundant solar energy, the high vacuum, and the weightlessness available in space, might bring substantial returns to investors. It seems possible that the historic industrialization of Earth might expand and go forward in space without the unpleasant impacts on the Earth's environment that increasingly trouble mankind. On the other hand, the potential of space must not detract from efforts to conserve terrestrial resources and improve the quality of life on Earth.

On the basis of this 10-week study of the colonization of space there seems to be no insurmountable problems to prevent humans from living in space. However, there are problems, both many and large, but they can be solved with technology available now or through future technical advances. The people of Earth have both the knowledge and resources to colonize space.

It is the principal conclusion of the study group that the United States, possibly in cooperation with other nations, should take specific steps toward that goal of space colonization.

Units and Conversion Factors

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