The Dimming of Starlight
Exploration and Future Opportunity
In any event, the appraisal of how much space exploration has done for us pales by comparison with the appraisal of how much more it may do in the years to come. The change of perspective is significant: whereas until now we have only tried to reach outer space and survive there for short periods, we will soon be in a position to live in space, industrialize it, and really put it to work for our benefit. Space presumably has two main advantages for industrialization: low gravity and a nearly perfect vacuum. These two advantages combined can bring us a treasure of new materials, including metal alloys, super-crystals, and extremely pure semiconductors and pharmaceuticals.
Consider the technological promise of low gravity ("microgravity" in the jargon of the trade). Under the influence of gravity objects have weight. The denser an object, the heavier it is. When we mix substances of different densities, gravity pulls the heavier to the bottom and leaves the lighter on top. In a similar fashion gravity creates openings between molecules – openings that allow impurities into the mix. Remove gravity and we can mix the substances evenly and without impurities.
The prospects for new technologies dependent on microgravity are said to be very encouraging. One of those technologies is levitation melting, in which molten metals can solidify without the use of a container (further reducing the problem of impurities). By injecting gases into the heated mixtures we can produce alloys that are not possible on Earth. Some of those alloys may have extraordinary properties; we may, for example, produce a form of steel as light as balsa wood. In medicine, the new purification techniques may be valuable in the investigation of new drugs or in the mass production of some drugs that are currently too expensive to manufacture.
Some of these possible new products would have to be manufactured in space, but others could be developed in space and then made on the planet. Once the feasibility and practicality of these products has been demonstrated through space research, earthbound industry would be more willing to get around the obstacles that gravity presents to their manufacture down here. The vacuum of space combines with microgravity to provide further opportunity for this sort of industrial research in metallurgy, thin-film coating, and welding, among others.
I must point out, however, that these exciting possibilities have been proclaimed almost from the beginning of the space program. It is at least worrisome that over forty years later industrialists do not yet seem to be flocking to take advantage of them. Part of the problem may well be that the Space Shuttle, instead of reducing launching costs, which was the main purpose for building it, has increased them dramatically.
If the costs of transportation can be reduced, setting up factories in space may have several advantages. Large structures can be built in space without many of the problems of foundation and support that gravity forces us to solve down on Earth. Without atmosphere, to say nothing of bad weather and pollution, machines can work for extremely long periods of time. And the energy they require can be obtained cleanly and efficiently from the sun.
All the industrial and technological advantages mentioned so far suggest how space exploration may play a major part in solving some of the most urgent problems of the Earth. Our world faces a double jeopardy: increasing demand for energy and dwindling of resources. In trying to obtain more energy we use up even more resources and, to make matters worse, produce greater amounts of pollution, which in turn affects some of our other resources, as well as our health and general well-being. For example, fossil fuels are the usual source of industrial energy. As we use them, we release ever-greater amounts of carbon dioxide (CO2) into the atmosphere. If the amount of CO2 continues to increase, some observers fear, the resulting greenhouse effect might raise the temperature of the planet enough to change the weather and melt much of the water now frozen in the polar caps. In the worst-case scenario, large areas millions of humans inhabit will be flooded out of existence.
To forestall these dire consequences (which I will discuss in Ch. 4), supporters of exploration have made proposals that range from the building of solar power satellites to the mining of the Moon, the asteroids, and eventually other planets. About thirty years ago, Peter Glaser proposed a solar power satellite to collect sunlight, transform it into electrical energy, and beam that energy down to Earth. In space, sunlight is plentiful and likely to last for billions of years; solar power satellites release no CO2; and environmental studies indicate that beaming this energy would be less harmful to plant and animal life than the existing alternatives. One solar power satellite the size of Manhattan would provide as much power as ten nuclear power plants without the attendant risks of radioactive leaks and meltdowns. With advances in photovoltaics (e.g., solar cells) and other fields, a collector about the size of half a football field might be able to produce one megawatt of power. Other space exploration supporters have suggested moving some of the most polluting industries to space. The promise of space exploration is then very enticing: abundant energy and a safer, cleaner environment.
Critics of these proposals have argued that the mining of the enormous quantity of materials required to build such structures would cause major environmental headaches, while the many thousands of flights by giant rockets to haul the materials into orbit might damage the atmosphere and are certain to cost far too much – in the hundreds of billions of dollars, at least for the system as presented to the U.S. Congress in the late 1970s. Congress found the proposal technologically feasible but accepted the criticisms and refused funding.
These criticisms seemed misleading at the time. The late physicist Gerard O'Neill, one of the most vocal proponents of the idea, had said all along that most of the required materials (e.g., aluminum, oxygen, and silicon) could be rather easily extracted from the Moon, placed in lunar orbit and processed there. The gravity pull of the Moon is only one sixth that of Earth, and thus the materials could be shot into lunar orbit, at great savings of energy and money, by what O'Neill called "mass drivers": long superconducting rails that use powerful electromagnetic fields to accelerate metal buckets full of lunar soil.
This project would be the beginning of the eventual colonization of the solar system, for no insurmountable technological barriers would then keep us from the abundant resources available in the asteroids, nor from building large habitats in space (Figure 2.3). To paraphrase O'Neill, the closing of the Earthly frontiers would be compensated for by the opening of the “high frontier” to the needs and hopes of humankind.
Whether projects of such magnitude are truly feasible in the next few decades remains a matter of controversy, while the enthusiasm for building O’Neill’s cities in the Lagrangian points between our planet and the Moon seems to have dissipated. A sobering sense of reality developed in the late 1980s when people realized that the Shuttle would never be the transportation system that O’Neill had assumed. Instead of fifty inexpensive flights a year, we were lucky to get five, and at astronomical costs (pun intended). This was no system for colonizing and mining the Moon. More recent proposals for solar power satellites suggest much smaller projects, though still large, for considerably less money, even though all materials would come from Earth.
To summarize, from the supporters of exploration we get an impression of great accomplishments in the past and even greater possibilities in the future. Their case, which by now is pretty much standard in the pro-exploration literature, seems quite impressive. It points out to social critics that space exploration reduces human misery and improves life on Earth. It tells ideological critics that space technology helps in controlling pollution and in monitoring the environment as a whole; and to both it promises that the new coming golden age of space exploration will do much to solve some of our most serious problems.
. Satellites may prove crucial in monitoring the effect on the polar caps of the average global temperature rise.
. Of course the change in weather may also be beneficial to some areas. A warm Siberia, for example, may become one of the largest gardens of the world.
. For details see Gerard O'Neill's The High Frontier, Anchor Press/Doubleday, 1982 (2nd edition). See also T. Heppenheimer, Colonies in Space, Stackpole Books, 1977.
 These are points where the gravitational pulls of the Earth and the Moon on a body balance with the centrifugal force – with a zero net force. A city placed in one of them would be in a stable orbit and would not require frequent corrections in its motion.
. Feingold, Harvey et al, “Space Solar Power: A Fresh Look at Generating Solar Power in Space for Use on Earth,” Rpt, SAIC-97/1005, 4 April 1997.