NASA SP-413 Space Settlements - Saint Ann's School

NASA SP-413 — SPACE SETTLEMENTS — A Design Study
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View to the Future
In earlier chapters conservative projections are made on the
possibilities of space colonization. The view is that the
potentialities of the concept are substantial even if no
advanced engineering can be employed in its
implementation. Abandoning a restriction to near-term
technology, this chapter explores long-term development in
space, mindful of a comment made many years ago by the
writer Arthur C. Clarke. In his view, those people who
attempt to look toward the future tend to be too optimistic in
the short run, and too pessimistic in the long run. Too
optimistic, because they usually underestimate the forces of
inertia which act to delay the acceptance of new ideas. Too
pessimistic, because development tends to follow an
exponential curve, while prediction is commonly based on
linear extrapolation.
What might be the higher limits on the speed and the extent
of the development in space? First, consider some of the
benefits other than energy which may flow from space to the
Earth if the road of space colonization is followed. To the
extent that these other benefits are recognized as genuine,
space colonization may take on added priority, so that its
progress will be more rapid.
From the technical viewpoint, two developments seem
almost sure to occur: progress in automation, and the
reduction to normal engineering practice of materials
technology now foreseeable but not yet out of the
laboratory. Those general tendencies, in addition to specific
inventions not now foreseen, may drive the later stages of
space colonization more rapidly and on a larger scale than
anticipated in the other chapters of this report.
BENEFITS NOT RELATED TO ENERGY
Space colonization is likely to have a large favorable effect
on communication and other Earth-sensing satellites.
Already communication satellites play an important role in
handling telex, telephone, computer, and TV channels.
They provide data-links and track airplanes and ships as well
as rebroadcast TV to remote areas. In the future even more
of these data-link applications can be expected. Not only
will planes and ships be tracked and communicated with by
using satellites, but trains, trucks, buses, cars, and even
people could be tracked and linked with the rest of the world
continuously. Currently, the main obstacle blocking direct
broadcasting of radio and TV to Earth from orbit is the lack
of low-cost power in space. SSPS’s would produce such
power. In addition, their platforms could be used to provide
stability. Currently, up to 40 percent of the in-orbit mass of
communication satellites consists of equipment used to
provide power and maintain stability. Finally, colonists
could carry out servicing and ultimately build some of the
components for such satellites.
Space manufacturing such as growing of large crystals and
production of new composite materials can benefit from
colonization by use of lunar resources and cheap solar
energy to reduce costs. Space manufactured goods also
provide return cargo for the rocket traffic which comes to L5
to deliver new colonists and components for SSPS’s.
Within the past half-century many of the rich sources of
materials (high-grade metallic ores in particular) on which
industry once depended have been depleted. As the size of
the world industrial establishment increases, and low-grade
ores have to be exploited, the total quantity of material
which must be mined increases substantially. It is necessary
now to disfigure larger sections of the surface of the Earth in
the quest for materials. As both population and material
needs increase, the resulting conflicts, already noticeable,
will become more severe. After the year 2000 resources
from the lunar surface or from deep space may be returned
to the Earth. Much of the lunar surface contains significant
quantities of titanium, an element much prized for its ability
to retain great strength at high temperature, and for its low
density. It is used in the airframes of high performance
aircraft, and in jet engines. Given the convenience of a
zero-gravity industry at L5, a time may come when it will be
advantageous economically to fabricate glider-like lifting
bodies in space, of titanium, and then to launch them
toward the Earth, for entry into the atmosphere. The
transportation of material to the Earth in this form would
have minimum environmental impact, because no rocket
propellant exhaust would be released into the biosphere in
the course of a descent. (Some oxides of nitrogen would be
formed as a result of atmospheric heating.) Titanium may
be valuable enough in its pure form to justify its temporary
fabrication into a lifting-body shape, and its subsequent
retrieval in the ocean and towing to port for salvage and use.
If such lifting-bodies were large enough, it might be practical
to employ them simultaneously as carriers of bulk cargo, for
example, ultra-pure silicon crystals zonerefined by melting
in the zero-gravity environment of the L5 industries. It has
been suggested that the traditional process of metal casting
in the strong gravitational field of the Earth limits the
homogeneity of casts because of turbulence due to thermal
convection. Quite possibly, in space, casting can be carried
out so slowly that the product will be of higher strength and
uniformity than could be achieved on Earth. A titanium
liftingbody might carry to the Earth a cargo of pure silicon
crystals and of finished turbine blades.
Chapter 7 — View To The Future