Table of Contents
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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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
byproducts.
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.
- Continue development of the space transportation system
(shuttle) and of Spacelab.
- Start development of the shuttle-derived Heavy-Lift Launch
Vehicle.
- Construct a large space laboratory for placement in low-Earth
orbit in which experiments necessary to space colonization can be
carried out.
- Establish a lunar base to explore and to test for the
availability of lunar resources.
- 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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