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Through consecutive evolutionary steps tending over billions of years the Universe is now able to contemplate itself. We humans stand in awe at the majesty of creation surrounding us. Can there be a grander perspective than the long evolution of intelligent life from the violent flash of the Big Bang? Can there be a greater challenge than using our access to space to understand the Universe and humanity's place within it? With faith in our Nation's ability to meet this challenge, we propose that the United States, through a vigorous program of space science, undertake a unified and comprehensive effort to understand the origin and evolution of the cosmos by integrating the findings of many diverse disciplines. This can lead to great new discoveries while increasing our ability to forecast future phenomena, including most importantly those that affect or ate affected by human activities.

Our current knowledge is summarized in the boxes on pages 26 and 55, but much remains to be done. Essential to our planning of future space science endeavors is an assessment of the most pressing fundamental questions now facing scientists-questions that if answered would lead to dramatic advances in our comprehension of the Universe around us. What follows is a condensed version of a list of such questions provided to us by the Space Science Board (SSB) of the National Academy of Sciences:

• What laws of nature govern the Universe? More specifically, what laws governed the birth and growth of the Universe and now govern large-scale phenomena like the formation of galaxies, neutron stars, and black holes that cannot be duplicated in laboratories on Earth?

• How do stars and planets form? How did the Sun, planets, satellites, and small bodies of the Solar System form; how have they evolved? Why are the giant planets so different from the terrestrial planets?

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

The Universe is the true home of humankind. Our Sun is only one star in the billions that comprise the Milky Way Galaxy, which in turn is only one of the billions of galaxies astronomers have already identified. Our beautiful planet is one of nine in our Solar System. Understanding our Universe is not just an intellectual and philosophical quest, but a requirement for continuing to live in, and care for, our tiny part of it, as our species expands outward into the Solar System.

In the 1920s scientists concluded that the Universe is expanding from its origin in an enormous explosion-the "Big Bang"-10 to 20 billion years ago. In the future, it could either expand forever or slow down and then collapse under its own weight. Recent studies in particle physics suggest that the Universe will expand forever, but at an ever decreasing rate. For this to be true, there must be about ten times more matter in the Universe than has ever been observed; this "hidden matter" may be in the form of invisible particles that are predicted to exist by modem theory. Thus, in addition to normal galaxies there may be invisible "shadow galaxies" scattered throughout space.

The Universe contains 100 billion or more galaxies, each containing billions of stars. Our Galaxy, the Milky Way, is the home of a trillion sun, many of which resemble our Sun. Each of these stars, when it is formed from an interstellar cloud, is endowed with hydrogen and helium-simple chemical elements that formed in the Big Bang, as well as with heavier elements that formed in previous ste1lar furnaces. Hydrogen is consumed by a thermonuclear fire in the star's core, producing heavier chemical elements that accumulate there before becoming fuel for new, higher temperature burning. In massive stars, the process continues until the element iron dominates the core. No further energy-producing nuclear reactions am then possible,

• How does energy flow from the interior of the Sun through its outer layers and into interplanetary space? How does it interact with the planets? How does the solar output vary? Does this cause Ice Ages and other changes in Earth's climate?

• What are the composition, structure, and dynamics of the interior and crust of Earth, and how did these layers form and evolve? What is the source of Earth's magnetic field?

• What are the structure, dynamics, and chemistry of the oceans, atmosphere, and polar

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so the core collapses suddenly under its own weight, producing vast amounts of energy in a stellar explosion known as a supernova. The temperature in a supernova is so high that virtually all of the chemical elements produced are flung into space, where they are available to become incorporated in later generations of stars. About once per century a supernova explosion occurs in each galaxy, leaving behind a compact object that may be a neutron star-as dense as an atomic nucleus and only a few miles in diameter-or a stellar black hole, in which space-time is so curved by gravity that no fight can escape.

Our Solar System consists of the Sun, nine planets, their moons and rings, the asteroids, and comets. Comets spend most of their time in the "Oort cloud," located 20,000-100,000 astronomical units from the Sun (an astronomical unit is the distance from Earth to the Sun, 93 million miles). The Solar System formed 4.5 billion years ago near the edge of our Galaxy. Heir to millions of supernova explosions, it contains a full complement of heavy elements. Some of these, like silicon, iron, magnesium, and oxygen, form the bulk of the composition of Earth; the elements hydrogen, carbon, and nitrogen are also present, providing molecules essential for life.

The Universe has evolved from the Big Bang to the point we see it today, with hundreds of billions of galaxies and perhaps countless planets. There is no evidence that the processes which govern the evolution from elementary particles to galaxies to stars to heavy elements to planets to fife to intelligence differ significantly elsewhere in the Universe. By integrating the insights obtained from virtually every branch of science, from particle physics to anthropology, humanity may hope one day to approach a comprehensive understanding of our position in the cosmos.

ice caps, and how do these components interact with the solid Earth? Why are the atmospheres of Mars, Earth, and Venus so different, and how did they evolve?

• What is the origin, evolution, and distribution of life in the Universe? Are we alone? What processes and environmental interactions spawned and now sustain life on Earth?

• What effect is life, and particularly human activity, having on the composition, dynamics, and evolution of the oceans, atmosphere, and crust of Earth?

• What is the importance of gravity in physical, chemical, and biological processes?

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Our nearest large galaxy: M31, Andromeda: if we were within this spiral galaxy, we would be near its outer edge. (COURTESY CALTECH AND CARNEGIE INSTITUTION)

No one can predict the dramatic scientific advances that will come in the next 20 to 50 years, but imagine what headlines might appear in the papers of the future as we expand our scientific activities in space (See page 29).

To answer all of our questions will take the efforts of generations of scientists in the United States and throughout the world, but current rapid progress in space science encourages the befief that one day the answers will be known. We believe that a well-planned, long-term program of space science along these fines will be a noble legacy for our descendants. New combinations of scientific disciplines, from theoretical physics to experimental biology, are needed to answer these complex questions. Coordination of these efforts across such a broad front may require new arrangements both in academia and in the Government. (See pages 149-151 for a description of the activities needed to realize our goals.)

The space science program of the United States has been guided since its inception by the Space Science Board. Their work, as cited in the bibliography, has laid out an excellent

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• IDENTIFICATION OF THE MISSING MATTER THAT MAKES UP 90 PERCENT OF THE UNIVERSE'S MASS.
• GRAVITATIONAL WAVES DETECTED.
• SOURCE OF HUGE ENERGIES IN EXPLODING GALAXIES DISCOVERED.
• IMAGE OF THE IMMEDIATE SURROUNDINGS OF A BLACK HOLE AT THE CENTER OF OUR GALAXY.
• AMINO ACIDS DISCOVERED IN THE URANIAN OCEAN.
• SUPERNOVA DEBRIS RECOVERED FROM COMET ICE.
• METHANE VOLCANOES DISCOVERED ON PLUTO.
• FIRST PLANET DISCOVERED OUTSIDE OF THE SOLAR SYSTEM.
• SIGNAL DETECTED FROM EXTRATERRESTRIAL INTELLIGENCE.
• MONTHLY SOLAR FLARE PREDICTIONS ACCURATE TO WITHIN HOURS.
• LINKS BETWEEN SOLAR ACTIVITY AND OUR WEATHER UNDERSTOOD.
• EARTH'S ENTIRE RADIATION BELT IMAGED.
• MONTHLY HURRICANE PREDICTIONS ACCURATE WITHIN 12 HOURS AND 100 MILES.
• THREE CONSECUTIVE EARTHQUAKES PREDICTED WITH 24-HOUR AND 50-MILE ACCURACY.
• SPACE STATION PROJECT TEAM CELEBRATES FIRST YEAR WITHIN A SYNTHETIC BIOSPHERE.
• BONE THINNING IN ASTRONAUTS HALTED WITH TREATMENT APPLICABLE TO PEOPLE ON EARTH.
• PERFECT GALLIUM ARSENIDE CRYSTALS PRODUCED IN SPACE STATION.
• THIRTY-DAY WEATHER FORECAST NOW 95% ACCURATE
• NEW STATE OF MATTER PRODUCED IN A SPACE LABORATORY.
• ICES DISCOVERED AT THE LUNAR POLES.
• FOSSILS FOUND IN ANCIENT MAR11AN RIVERBED.
• VENUS VOLCANOES VERIFIED.

program for the next decade. We have built upon their recommendations and those of other National Academy of Sciences committees. The SSB is currently preparing a study called Major Directions for Space Sciences: 1995-2015 whose preliminary findings and recommendations were extremely helpful in plotting our course beyond the year 1995. The study delineates exciting new possibilities for fundamental research in every area of space science,

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

using future space technology of the type described elsewhere in this report. This supports our recommendation that: The United States launch a vigorous space science program aimed at (1) understanding the evolutionary processes in the Universe that led to its present characteristics (including those leading to the emergence and survival of life), and (2) using our new understanding to forecast future phenomena quantitatively, particularly those that affect or am affected by human activity.

For the first time in history we can observe the entire Earth as we would another planet, from its core to its outer atmosphere, both as it is now and as it has been over the eons. Advances in the technology of observing systems and computers promise to revolutionize terrestrial science. Moreover, advances in theoretical understanding and the availability of the supercomputer are providing detailed models that can be tested experimentally.

We propose that a long-range global study of planet Earth be undertaken. It is essential that studies of Earth be carried out in parallel with studies of other planets, for insights into the evolution of any planet throw fight on the evolution of all. This study should be carried out with major international collaboration from 1995 to 2015 through a global satellite-based observing system, complementary measuring devices and surveys on Earth, computational facilities for modeling, and a system for archiving and disseminating data, all to be coordinated at the national level by the Federal agencies involved. Dynamic phenomena should be investigated over a wide range of time scales, with particular attention to processes that affect, or are affected by, human activities. Examples include continental drift, volcanic activity, earthquakes, ocean currents, events like El Niño, the response of the upper atmosphere to changes in radiation from the Sun, and potentially critical changes in the amounts of important gases such as carbon dioxide in Earth's atmosphere.

This global study of planet Earth will be based upon a strategy of observation, data handling, and research markedly different from that prevailing today, owing to new opportunities for an integrated approach and for increasing use of artificial intelligence techniques. Many, but not all, relevant measurements are best done from satellites. Simultaneous global coverage is essential to many observations, and the observing system must produce continuous and consistent records over long periods of time. This with require a number of geostationary satellites carrying a wide variety of instruments for long-term measurements. These satellites will be large high-powered spacecraft carrying unproved versions of refurbishable or replaceable instruments currently in use or being developed.

Polar orbiting satellites will also be required to provide coverage of high latitudes and platforms for instruments that must operate at lower altitudes. Spacecraft now under development will increase our understanding of the "middle atmosphere," including the stratosphere, mesosphere, and lower thermosphere. These layers are just above the lower atmosphere, or troposphere, in which our weather is produced. Chemical changes like the production and

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The mean surface temperature for November 1979-a mosaic of data taken by a NOAA satellite. (COURTESY M. CHAHINE AND J. SUSSKIND)

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Graft W of the world’s oceans-a mosaic: of Seasat data. (COURTESY W. HAXBY)

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

destruction of ozone take place in this middle atmosphere, with considerable consequences for living things on Earth. Other spacecraft in polar orbits will provide information on the differences between the northern and southern hemispheres and their responses to solar-terrestrial events. Starting in the 1990s, the Space Station and its co-orbiting and polar-orbiting platforms will provide even greater opportunities for probing the upper atmosphere. A tether system mounted on the Space Station will allow measurements at altitudes as low as 72 miles-a region only intermittently probed now by sounding rockets. Occasional special purpose missions will require other orbits to test instruments and ideas for incorporation into the satellites described previously and to provide key one-time measurements. For example, "current buoys"–small satellites in selected orbits-wil1 measure electrical currents with sufficient coverage to enable the construction of a global map of the currents that carry the ebb and flow of energy in Earth's magnetic field.

This global study of planet Earth is geared toward greater understanding of the physical and biological processes on our planet and their interactions. A vigorous and systematic study of the structure, dynamics, and evolution of the biosphere (i.e., living organisms and their

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A false-color image obtained by the Einstein Observatory of the x-rays emitted by hot gas in the M87 galaxy. This gas, with a temperature of 10 million degree, is invisible in optical pictures. The distribution of the gas enables astronomers to deduce that the galaxy has a mass of at least 3 trillion suns. (COURTESY D. FABRICANT AND P. GORENSTEIN)

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interaction with the solid Earth, oceans, atmosphere, and polar ice caps) from the Space Station complex in low Earth orbit will be an essential component of the project. There is particular interest in the quantities that are changing rapidly, perhaps because of human activity, such as concentrations of ozone, methane, and carbon dioxide in the atmosphere.

To understand the early evolution of life on Earth requires the continued search for the oldest microfossils. This ground-based work should be supported by continued laboratory studies of the synthesis of key biological molecules under conditions approximating primitive Earth, as well as by further studies of meteorites and by the components of the space program that are concerned with studies of chemical processes on planets, asteroids, comets, and satellites. In view of the evidence that collisions with asteroids and/or comets have severe effects on Earth's biosphere, astronomical studies of such objects and continued geological studies of their effects are crucial.

The environment near Earth must also be studied carefully as part of the global attack. This requires not only major missions of the type described earlier, but also smaller-scale activities, including satellites, balloons, and sounding rockets.

Ground-based measurements will be a crucial part of the global study of Earth, since some effects cannot be detected by remote sensing from space. Ground-based surveys can provide high spatial resolution over limited areas and critically important calibrations, or "ground truth," for observations from space. Continuing studies of Earth's geological record are important to clarify long-term trends in geological processes, geochemical abundances, and climatic factors. From the global study of planet Earth, a rich harvest of knowledge will result, laying the groundwork for an increasing capability to observe and predict our terrestrial environment.

Human Biology in Space

The study of the response of organisms to conditions in space is vitally important if we are to undertake long-duration space flights by astronauts in Earth orbit and on missions to other bodies in the Solar System. The environment for living things in space differs from that on the ground, especially in the strength of gravitational fields, compositions and pressures of atmospheres, and radiation fluxes. Our knowledge of the effects of these factors is still primitive, owing to the paucity of experimental opportunities in the post Apollo era. Substantial time and laboratory space must be made available for such experiments on the Space Station.

For the most effective experimentation, it is possible to simulate gravity from less than a hundred-thousandth to greater than one Earth gravity by using centrifugal force in a rotating system or by a gravity-gradient fixed tether. The atmospheric pressure should be variable from essentially zero to several times the pressure at sea level on Earth. We recommend a new administrative entity, the National Space Laboratory as described on pages 149-151 and the development of a Variable-g Research Facility as discussed in Part.

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

Unshielded radiation fluxes pose potential problems both to the survival of organisms in space and to the interpretation of data. One concern requiring further study in this area is the high-energy high-charge component of the cosmic ray flux, which can damage non-dividing cells, including those of the central nervous system. Current practices regarding measurement of radiation doses should be reviewed, especially in view of the large range of particle energies encountered in space.

Of paramount practical importance are human safety and performance. Long-duration flights on the Space Station will increase our understanding of the effects of the space environment on people and other living systems. Problems of bone demineralization and loss of muscle mass persist, and effective empirical solutions are unlikely to be found soon. The impact of this problem becomes clear if we envision the response of a weakened skeletal structure to increased gravity when, for example, humans emerge on a planetary surface after a prolonged period of weightless flight. It is imperative that basic research on this problem continue, both on the ground and in space.

As opportunities for longer flights become available, new research should be undertaken with careful monitoring and evaluation of subjects. This will require more detailed monitoring of the environment than in the past, including gravity, radiation exposure, environmental toxicology, nutrition as it affects performance, microbial environment, epidemiology, functioning of the body's defense mechanisms, and dynamics of 1 interpersonal interactions in a closed environment.

Remote health-care delivery in space must be developed as well. This will be a major issue as plans are made to send astronauts to the planets, since a rapid return to Earth will be virtually impossible. Little is known of the dynamics of drugs administered in a space environment, and the evaluation of even a small "space pharmacopoeia" will be a major undertaking; similar considerations apply to surgery under microgravity conditions. The importance of the latter is highlighted by recent estimates that one of a crew of seven astronauts selected from the general population for a Mars expedition would probably experience a medical problem normally requiring surgery. The selection process for astronauts must mitigate, but cannot completely eliminate, this problem.

The permanently occupied Space Station will, for the first time, permit relatively long-term laboratory experiments to be performed in the nearly weightless environment, or microgravity, of space and in controlled artificial gravity at levels between zero and one g (See page 35). A wide array of biological problems that have little direct bearing on human performance or safety can also be addressed by research in space. The vestibular system, for example, which is the part of the central nervous system concerned with bodily orientation, evolved over billions of years under Earth-gravity conditions. Studying its response in detail to microgravity should yield valuable new information about the central nervous system. This will require mammals (including primates) and facilities for their long-term care in space, as well as a centrifuge and, if possible, a sled to produce variable accelerations. Valuable experiments can also be undertaken on the long-term sensitivity of both plants and animals to gravity.

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A Nobel Prize-winning theory predicts the change in beat capacity of liquid helium at uniform pressure as it makes a transition to the superfluid state. Although equipment has been developed to hold samples at a steady temperature within one part in 10 billion, the variation of pressure through the sample due to gravity is so large that experiments have yielded far less accurate results than desired. Reducing gravity by a factor of 100,000, as is possible in the Space Station, can provide a high-quality test of the theory.

Research is also proceeding on "fractal aggregates," structures that have the remarkable property that their mean density literally approaches zero the larger they become. Such structures are neither solid nor liquid, but represent an entirely new state of matter. So far, experiments on such structures are limited by the fact that the aggregates tend to collapse under their own weight as soon as they reach .0004 inches in size. In a microgravity environment, it should be possible to develop structures 100,000 times larger, or three feet across. Such sizes are essential if measurements of the physical properties of fractal structures are to be made.

Research on many other processes, including fractal gels, dendritic crystallization (the process that produces snowflakes), and combustion of clouds of particles, will profit substantially from the microgravity environment of the Space Station. It is not unlikely that novel applications will develop from basic research in these areas; just as the transistor grew out of basic research on the behavior of electrons in solids.

On Earth, laboratory experiments have shown that many of the bio-chemical compounds that are essential for life as we know it can be synthesized under conditions that we believe simulate those on primitive Earth. In space, we can investigate the effects of gravitational force on the behavior of these life-related compounds. Astronomers have found evidence for the existence of simple and complex compounds of carbon in interstellar space. In a microgravity laboratory in space we can investigate the apparently universal processes that form these compounds, which were no doubt present in the matter from which the Solar System was formed, and were probably the precursors to life on Earth.

To accomplish the goals of life science research in space will require Space Station facilities for growing plants, animal care and husbandry, for chemical and other types of analysis, and for neurobiological research focused initially upon the vestibular function. Since the Space Station's available volume, weight, and power will be limited, it is important that equipment be utilized for multiple purposes wherever possible, and that faclitities essential for health-care delivery be adapted for basic biological research as well.

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

Fundamental Biology, Physics, and Chemistry in Earth Orbit

On Earth, the effects of gravitational forces on complex living systems are profound. We know this because of the so-called space sickness that strikes more than half the people who venture into space, apparently as a result of weightlessness. Experiments in space will allow us to identify and quantify the effects of gravity on the development, adaptation, and functions of plant and animal biological systems as well, on the biology of cells, and on the chemistry of complex biological molecules.

In the physical sciences, studies of the laws of gravitation are especially significant. For most purposes, the laws discovered by Newton are sufficiently accurate, but Einstein's more precise theory of general relativity predicts more subtle effects, including new states of matter, black holes, and a new form of energy called gravitational radiation. Although the general theory of relativity has passed all the experimental tests to which it has been subjected so far, more sensitive tests should now be carried out (See page 37).

We recommend that: Flexible and rapid access be provided to a microgravity facility for researchers who will continue to devote the bulk of their effort to ground-based research in normal gravity; and new tests of general relativity be carried out wherever possible using facilities in space.

The orange dots are the positions where individual x-ray photons from the Cassiopeia A supernova remnant were recorded by the Einstein Observatory. The photons were emitted by a shock wave propagating into the interstellar medium from the supernova explosion. (COURTESY S. MURRAY)

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WAS EINSTEIN RIGHT?

An especially promising avenue of research in space is the pursuit of new tests of Einstein's theory of general relativity. It has long been recognized that because deviations from the Newtonian theory of gravitation within the Solar System are minute, extremely sensitive equipment is required to detect them. Many experiments require the ultraquiet conditions of space. Because Einstein's theory is fundamental to our understanding of the cosmos-in particular, to the physics of black holes and the expanding Universe-it is important that it be experimentally verified with the highest possible accuracy.

Relativity predicts a small time delay of radio signals as they propagate in the Solar System; the accuracy in measuring this effect can be continuously improved by tracking future planetary probes. A Mercury orbiter would further improve the accuracy of measurement of changes in Newton's gravitational constant, already shown to be less than one part in 100 billion per year. An experiment in Earth orbit called Gravity Probe B will measure the precession of a gyroscope in Earth orbit with extreme precision, permitting verification of another relativistic effect.

Einstein's theory also predicts that a new type of radiation should be produced by masses in motion. There is great interest in detecting this so-called gravitational radiation, not only because it would test Einstein's theory in a fundamental way, but because it could open a new window through which astronomers could study phenomena in the Universe, particularly black holes. Gravitational radiation detectors are in operation, or are being built, on the ground, but they are sensitive only to wave periods less than 0.1 second because of Earth's seismic noise.

The radiation predicted from astronomical objects would have much longer periods if it is due to orbiting double stars and black holes with masses greater than 10,000 Suns, such as are believed to exist in the nuclei of galaxies. An attempt will be made to detect such radiation by ranging to the Galileo spacecraft en route to Jupiter. A more powerful approach for the future is to use a large baseline detector based upon optical laser ranging between three spacecraft in orbit about the Sun; detecting minute changes in their separations would indicate the passage of a gravitational wave.

Finally, instruments deployed for more general purposes can make measurements to test general relativity. For example, a 100-foot optical intederometer in Earth orbit designed for extremely accurate determination of stellar positions could measure the relativistic bending of light by the Sun with unprecedented precision. A spacecraft that plunges close to the Sun to study plasma in its vicinity could measure the gravitational red-shift of the Sun to high precision. In summary, a variety of space-based experiments on the shuttle and Space Station, in free flyers, and in orbit around the Sun and other planets have the capacity to test general relativity with a high degree of accuracy. Gravitational radiation from certain astronomical sources can be detected only in space. When that happens, astronomers will have an exciting new tool with which to study the Universe.

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Our Sun is the only star that is near enough for detailed study. It is a complex and highly variable object whose variations cause changes on Earth. We need to understand how solar activity is produced, how this activity is linked to changes on Earth, especially to the changes that impact our environment. Space technology allows us to study the Sun and its effects on the rest of the Solar System, especially solar effects on Earth. Pluto, the most distant planet in the Solar System, orbits the Sun at a distance of about 3.5 billion miles, but the region affected by the Sun, called the heliosphere, may extend as far as 10 billion miles from the Sun. It is filled with an electrical plasma called the solar wind that flows from the Sun at about 300 miles per second.

A plasma, as the term is used here, consists of electrically charged particles, atomic nuclei and electrons, in electromagnetic fields. Nearly all of the matter found in the Universe exists as plasma in one or another state. Consequently, the study of plasmas has a number of branches, of which space physics is one. By using rockets and spacecraft, space physicists have learned that Earth's magnetic field extends far beyond our atmosphere, permeating a region of space referred to as Earth's magnetosphere. This region is filled with a complex mixture of space plasmas.

Understanding near-Earth space and the effects of solar activity is vital not only to the understanding of our weather and climate, but also to the safety of People in space. The effective operations of space-based facilities, especially electronic units and power systems, can also be adversely affected by the behavior of plasmas in their vicinity. Protecting humans from radiation outside the protective shield of the lower-altitude region of the magnetosphere requires that we develop sufficient understanding of the Sun and its effects to permit us to predict conditions in this region of space. Our recommendations for pursuing this area of space research are described on page 40.

Magnetospheres similar in many respects to those enveloping Earth and some of the other planets appear to exist in many other places in the Universe, from neutron stars to exploding galaxies. Consequently, studies of phenomena within our Solar System also increase our understanding of universal processes.

A program for solar and space physics from now until the mid-1990s has been developed in a number of studies under the auspices of the National Academy of Sciences and NASA. Beyond the initial operation of the Space Station, we recommend a program with four major components: (1) Spaceborne instruments to obtain observations from sets of orbits that are both closer to the Sun and global in their coverage; (2) Remote sensing of the plasmas in Earth's magnetosphere and the heliosphere using large-scale detectors in Earth orbit, at libration points, and on the surface of the Moon, in combination with directed energy sources as appropriate, and complemented by spacecraft to obtain direct measurements of the plasmas; (3) Active experiments designed to take advantage of the near vacuum of space in the study of the behavior of plasmas in the absence of confining walls that are

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Image of the Aurora Borealis obtained by the Dynamics Explorer spacecraft as It orbited above the North Pole. (COURTESY NASA)

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Photograph of an aurora in the southern hemisphere taken by the Spacelab 3 crew in may 1984. (COURTESY NASA)

CIVILJAN SPACE G OALS FOR 21^ST-CENTURY AMERICA

The objective of this field of study is to understand the physics of the Sun and the heliosphere, the vast region of space influenced by the Sun. Other regions of interest include the magnetospheres, ionospheres, and upper atmospheres of Earth, the planets, and other bodies of the Solar System. With this in mind, studies of the basic processes which generate solar energy of all kinds and transmit it to Earth should be emphasized, both because the physical mechanisms involved are of interest, and because there are potential benefits to life on Earth.

There are a number of sub-goals within this discipline: To understand the processes that fink the interior of the Sun to its corona; the transport of energy, momentum, plasma, and magnetic fields through interplanetary space by means of the solar wind; the acceleration of energetic particles on the Sun and in the heliosphere; Earth's upper atmosphere as a single, dynamic, radiating, and chemically active fluid; the effects of the solar cycle, solar activity, and solar-wind disturbances upon Earth; the interactions of the solar wind with Solar System bodies other than Earth; and magnetospheres in general. Without assuming specific direct connection, the possible influence of solar-terrestrial interactions upon the weather and climate of Earth should be clarified.

A number of near-term activities are essential to the advancement of solar and space physics. Advanced solar observatories will study detailed energy production mechanisms in the solar atmosphere, while the European Space Agency's Ulysses spacecraft will make measurements of activity at the poles of the Sun. Spacecraft with sufficient velocity to leave the inner Solar System will make possible measurements in the outer heliospbere, including its transition to the interstellar medium of the Galaxy. The International Solar-Terrestrial Physics program, which wilI be carried out jointly by the United States, Japan, and Europe, will trace the flow of matter and energy from the solar wind through Earth's magnetosphere and into the upper atmosphere; investigate the entry, storage, and energization of plasma in Earth's neighborhood; and assess how time variations in the deposition of energy in the upper atmosphere affect the terrestrial environment. Interactions of solar plasma with other planets and with satellites and comets will be investigated by a number of planetary probes already in space or on the drawing boards.

Up to now, information about Earth's magnetosphere has been based upon measurements made continuously as various spacecraft move through the plasma and

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magnetic field in that region. An instantaneous global image of the entire magnetosphere can be made using ultraviolet emissions from ionized helium in the magnetosphere. It may also be possible to form an image of energetic particles by observing energetic neutral atoms as they propagate from various regions, having exchanged charge with other atoms there. Innovative experiments will be conducted from the shuttle to investigate the effects of waves, plasma beams, and neutral gases injected into Earth's magnetosphere.

To date, our knowledge of the outer atmosphere of the Sun has been based upon remote sensing from the distance of Earth. In a new concept, a spacecraft would be sent on a trajectory coming to within 4 solar radii of the surface of the Sun, only 1/50th of Earth's distance. The spacecraft would carry instruments to measure the density, velocity, and composition of the solar-wind plasma, together with its embedded magnetic field, in an attempt to discover where the solar wind is accelerated to the high velocities observed near Earth. Possible trajectories include a Jupiter swingby or a hypersonic flyby in the upper atmosphere of Venus. Such a mission would yield precise data on the gravitational field of the Sun with which to study its interior, and would test general relativity with higher precision. If a thruster were fired at the closest approach to the Sun, the energy change would be so great that the spacecraft would leave the Solar System with high velocity, reaching 100 times the distance of Earth in only nine years. This would provide measurements where the solar wind makes a transition to the local interstellar medium.

To acquire high-resolution information about the poles of the Sun over a long-period, a solar polar orbiter should be flown. A network of four spacecraft at the distance of Earth, but positioned every 90 degrees around the Sun, would provide stereoscopic views of solar features which are otherwise difficult to locate in space, and would also monitor solar flare events over the whole Sun. Such a network would also give early warning to astronauts outside the protective shield of Earth's magnetic field.

Finally, plasmas in space should be studied for their own sake. Plasma is an inherently complex state of matter, involving many different modes of interaction among charged particles and their embedded magnetic fields. Our understanding of the plasma state is based upon theoretical research, numerical simulations, laboratory experiments, and observations of space plasmas. The synergy among these approaches should be developed and exploited. If neutral atoms and dust particles are present, as in planetary ring systems and in comets, novel interactions occur; they can be studied by injecting neutral gases and dust particles into space plasmas.

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Photograph of a solar flare taken by the crew of the Skylab 4 mission (Courtesy NASA)

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Voyager 2 flyby of Neptune in 1989. in the foreground is Neptune's moon, Triton. (COURTESY RON MILLER)

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With the exception of the samples returned from the Moon by the Apollo astronauts and the Soviet robotic Luna spacecraft, and meteoritic materials that are believed to have fallen naturally on Earth from the asteroids, the Moon, and Mars, we have no samples of materials from bodies elsewhere in the Solar System for analysis in Earth-based laboratories.

Decades of study of meteoritic materials and lunar samples have demonstrated that vast amounts of information can be learned about the origin, evolution, and nature of the bodies from which samples are derived, using laboratory techniques which have progressed to the point where precise conclusions can be drawn from an analysis of even a microscopic sample.

The laboratory apparatus involved is heavy, complex, and requires the close

involvement of people. Thus, given the substantial round-trip travel time for radio signals between Earth and these objects, it appears impractical to operate this equipment effectively under radio control on the bodies of greatest interest. The best method is to acquire and return samples, as was done by Apollo and Luna. Robot vehicles will be "the most cost-effective approach to sample acquisition and return in the foreseeable future.

Unlike meteoritic materials, the samples will be obtained from known sites, whose location in an area which has been studied by remote sensing makes it possible to generalize the results to the body as a whole. Because of the variations among different provinces, samples are required from several sites in order to develop an adequate understanding of a specific object.

Considerable thought has been given to which targets are the most promising.

-velocity spacecraft to be sent out of the Solar System on a trajectory to the nearest star.

The Solar System is of great interest not only because it is our extended home, but also because it represents a system, so far as we know unique, in which small solid bodies-the planets, satellites, comets, and asteroids-orbit a central star that interacts vigorously with them. In pursuing the question of the origin and evolution of the Sun and planets, we hope to discover other such systems and, by comparative studies, learn more about both.

Space techniques make it possible to make measurements throughout the Solar System using automated spacecraft. The overarching goal of planetary exploration enunciated by the

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They must be reachable, and samples must be able to be returned with technology that can be developed in the near future. Their surfaces must be hospitable enough so that collecting devices can survive on them, and they must be well-enough understood that a complex sample-return mission can be planned and successfully executed. For these reasons, as well as others noted in the text, we recommend that a sample return from Mars be accomplished as soon as possible.

Though at present no individual comet meets the criteria discussed above, comets in general are promising targets for sample return. A start on the study of comets has been made by the 1985 encounter with Comet Giacobini-Zinner, and the 1986 encounters with Comet Halley. The proposed mission to a comet and an asteroid in the Solar System Exploration Committee's core program wi1l yield much more information. Comets are probably composed of ices of methane, ammonia, and water, together with silicate dust and organic residues. The evidence suggests that these materials accumulated very early in the history of the Solar System. Because comets are very small (a few miles in diameter), any heat generated by radioactivity readily escaped, so they never melted, unlike the larger bodies in the Solar System. It is quite possible, therefore, that the primitive materials which accumulated to form the Sun, planets, moons, and asteroids are preserved in essentially their original form within comets. It is even possible that comets contain some dust particles identical to those astronomers have inferred to be present in interstellar clouds. If so, a comet could provide a sample of the interstellar matter that pervades our Galaxy. The Space Science Board has given high priority to determining the composition and physical state of a cometary nucleus. No mission short of a sample return will provide the range and detail of analyses needed to definitively characterize the composition and structure of a comet nucleus.

Space Science Board is to determine the origin, evolution, and present state of the Solar System. Two additional goals are to understand Earth better through comparative studies with the other planets and to understand the relationship between the chemical and physical evolution of the Solar System on the one hand, and the origin and evolution of life on the other. The SSB has developed a systematic strategy for this in which a program of reconnaissance of various types of objects in the Solar System is first carried out by telescopic observation and spacecraft which "fly by" the object. This is followed by more detailed exploration, for example by orbiters and landers. Finally, intensive studies are undertaken involving the return of a sample for analysis, and exploration by astronauts.

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

NASA's Solar System Exploration Committee (SSEC) has developed a plan to implement part of the strategy articulated by the SSB. The SSEC recommendations include an initial sequence of four missions: To Venus, to Mars, to a comet and an asteroid, and to

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An automated spacecraft prepares to take a sample of the material on a comet's nucleus. (COURTESY WILLIAM HARTMANN)

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Saturn's moon, Titan. Later missions include a Mercury orbiter, additional probes to Mars, a

probe into the atmosphere of Venus, a lunar orbiter, a mission to obtain a sample of debris

from a comet, an asteroid mission, and missions to Saturn, Uranus, and their moons.

The missions mentioned here, like others in NASA's planetary exploration program, will

provide measurements focused on critical questions about each target. For example, the Titan J

mission will focus on Titan's atmosphere, which is known to contain organic molecules of the

type biologists believe played key roles in the origin of life on Earth. Measurements will be

designed to tell us whether Titan's atmosphere has evolved so that primitive life is possible

there, or whether lower temperatures or other factors on Titan have prevented the formation

of life.

The attainment of many of the goals of the SSB will require new technology. Some of

these requirements are discussed on pages 95-106. A highest-priority initiative is the returning of samples from various bodies in our Solar System, as described on page 44.

Mars is of particularly great scientific interest for a variety of reasons. It has experienced

a complete range of geological and atmospheric processes, including vulcanism, the formation

of canyons, dust storms, regional flooding, glaciation, and sedimentary deposition. Although

some of these are similar to their Earth counterparts, there are important differences that can

teach us much about our own planet. In contrast to Venus, which is highly inhospitable to life A

as we know it, we believe that Mars is an alternative home for humanity.

In keeping with our program and the recommendations of the Space Science Board for

the study of Mars, a Mars sample return mission should be carried out early in the first decade of the 21st century. It is conceivable that Mars samples would include fossil evidence showing that life once existed on the planet; one can hardly imagine a more exciting discovery. In addition to their great scientific value, these samples can provide the basis for our initial steps in the development of Martian resources.

Asteroids and comets are of particular interest in our quest for knowledge about the origin of the planets. Because they may contain primitive materials that have been held in a deep freeze since the origin of the Solar System, they are accorded high priority for scientific investigation. These investigations will begin with flybys, and culminate with a sample return (See page 44).

The outer planets and their satellites, especially Uranus and Neptune, are difficult to

explore because of their large distances from Earth. They are, nevertheless, of great scientific

interest (See page 48). A long-term strategy for scientific study of the outer Solar System will

depend upon the findings from missions to the outer planets in the Solar System Exploration

Committee's core program, and upon technology developments recommended in this report

(See pages 95-106).

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

EXPLORATION OF THE OUTER PLANETS

Beyond the asteroid belt he four giant ringed planets (Jupiter, Saturn, Uranus, and Neptune), the curiously small world Pluto, more than 40 moons (two of which-Titan and Ganymede-are larger than the planet Mercury), and two planetary magnetospheres larger than the Sun itself. The center of gravity of our planetary system is here, since these worlds (chiefly Jupiter and Saturn) account for more than 99 percent of the mass in the Solar System outside of the Sun itself. The outer planets, especially Jupiter, can provide unique insights into the formation of the Solar System and the Universe. Because of their large masses, powerful gravitational fields, and low temperatures, these giant planets have retained the hydrogen and helium they collected from the primordial solar nebula.

The giant worlds of the outer Solar System differ greatly from the smaller terrestrial planets, so it is not surprising that different strategies have been developed to study them. The long-term exploration goal for terrestrial planets and small bodies is the return of samples to laboratories on Earth, but the basic technique for studying the giant planets is the direct analysis of their atmospheres and oceans by means of probes.

Atmospheric measurements, which will be undertaken for the first time by Galileo at Jupiter, provide the only compositional information that can be obtained from a body whose solid surface (if any) lies inaccessible under tens of thousands of miles of dense atmosphere. Atmospheric probe measurements, like measurements on returned samples, will provide critical information about cosmology and planetary evolution, and will permit fundamental distinctions to be made among the outer planets themselves.

The outer Solar System provides us with a special challenge, one that can be described as an embarrassment of scientific riches. It presents an overwhelming number of potential targets beyond the planets: The larger moons (Titan and Triton), the smaller moons (including the diverse Galilean satellites),-the rings, and the magnetospheres.

Exciting possible missions include: (1) Deep atmospheric probes (to 500 bars) to reach the lower levels of the atmospheres of Jupiter and Saturn and measure the composition of these planets; (2) hard and soft landers for various moons, which could emplace a variety of seismic, heat-flow, and other instruments; (3) close-up equipment in low orbits; (4) detailed studies of Titan, carried out by balloons or surface landers; (5) on-site, long-term observations of Saturn's rings by a so-called "ring rover" spacecraft able to move within the ring system; and (6) a high-pressure oceanographic probe to image and study the newly-discovered Uranian Ocean.

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Galileo probe descending into the atmosphere of Jupiter in the late 1980s (COURTESY RON MILLER)

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

Astronomy is based upon the collection of faint electromagnetic radiation from distant objects in the Universe, using sensitive telescopes operating at various wavelengths; cosmic-ray particles also yield important information. Answering the fundamental questions posed in this chapter requires the study of objects ranging from interstellar dust clouds, for which radio and infrared techniques are most appropriate, to extremely hot gas orbiting black holes in exploding galaxies, for which x-ray and gamma-ray telescopes are required.

Instruments must be launched into space to observe the complete spectrum of infrared sources, and ultraviolet, x-ray, and gamma-ray radiation from celestial sources, since these wavelengths do not penetrate Earth's atmosphere. Although optical and radio astronomy can be done from the ground, these disciplines also gain from space observations-optical astronomy by eliminating atmospheric blurring of the image that plagues ground-based observations and radio astronomy by providing extremely long baselines for ultra-high angular resolution.

Astronomical instruments in space can be located in low Earth orbit, geostationary orbit, solar orbit, or on the surface of the Moon. With a few notable exceptions, most of them have so far been in low Earth orbit, and in the near future will continue to be located there because of lower cost and direct support from the Space Station. As a lunar base is developed, astronomers will take advantage of the ability to build rigid telescope mounts, of the freedom from contamination by propellants, of the longer and colder nights, and of the shielding from Earth light and radio interference which are available on the far side of the Moon. If gravitational radiation is detected (See page 37), they wil1 want to study the feasibility of locating gravitational radiation detectors on the Moon, where seismic noise is far lower than on Earth.

Virtually the whole electromagnetic spectrum his now been explored to some degree. Major new facilities, covering the gamma-ray, optical, ultraviolet, x-ray, and infrared bands of the spectrum, will permit exciting studies of faint and distant objects at wavelengths across the entire radiation spectrum. Orbiting astronomical observatories will remain in space for extended periods, with maintenance and refurbishment by astronauts on the space shuttle and Space Station. A program of "great observatories," which responds to the 1982 recommendations of the National Academy of Sciences, will address virtually all of the major questions now challenging astronomers and astrophysicists, with even more capable observatories now on the horizon (See page 52).

The stage is set for several decades of extraordinary accomplishments in space science. Using advanced, technology, it will be possible to address the fundamental question of the origin of the Universe, the evolutionary steps which led to the galaxies, stars, planets, and fife on Earth. We should be able to discover whether there is life elsewhere in the Universe. To bring about these accomplishments will require the dedicated effort of the world scientific community, continuing teamwork among university, industry, and government researchers,

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Probe descending into the atmosphere of Titan, a moon of Saturn. (COURTESY RON MILLER)

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

The size of the current generation of "great observatories" reflects the limitations on weight, size, and power of facilities that can be launched into low Earth orbit by the space shuttle. In the future, the permanently occupied Space Station will furnish a vitally important new capability for astronomical research-that of assembling and supporting facilities in space that are too large to be accommodated in a single shuttle launch.

Such large facilities will increase sensitivity by increasing the area over which radiation is collected, and will increase angular resolution using the principle of interferometry, in which the sharpness of the image is proportional to the largest physical dimension of the observing system. Though one or the other goal will usually drive the design of any particular instrument, it is possible to make improvements in both areas simultaneously. When we can construct very large observatories in space, these improvements wil1 be achieved over the whole electromagnetic spectrum. Although the Moon will also offer advantages for astronomical facilities once a lunar base becomes available, we focus our remaining discussion upon facilities in low Earth orbit.

A large deployable reflector of 65 to 100 feet aperture for observations in the far infrared spectrum, that is, diffraction limited down to 30 microns wavelength (where it would produce images of a fraction of an arc second across), will permit angular resolutions approaching or exceeding that of the largest ground-based optical telescopes. This project would yield high-resolution infrared images of planets, stars, and galaxies rivaling those routinely available in other wavelength ranges. Assembly in Earth orbit is the key to this observatory.

A large space telescope array composed of several 25-foot-diameter telescopes would operate in the ultraviolet, visible, and infrared. The combination of larger diameter telescopes with a large number of telescopes would make this instrument 100 times more sensitive than Hubble Space Telescope. Because the image would be three times sharper, the limiting faintness for long exposures would increase more than 100 times. Such an instrument would with exquisite angular and spectral resolution enable detailed studies of the most distant galaxies and studies of planets.

A set of radio telescopes 100 feet or more in diameter could be constructed in Earth orbit by astronauts to provide a very long baseline array for observing radio sources, with the radio signals transmitted to a ground station. Such radio telescopes in space could greatly extend the power of the ground-based Very Long Baseline Array now under construction. The angular resolution of the latter, 0.3 milliarcseconds (the size of a person on the Moon as seen from Earth), could be improved 300-fold by putting telescopes in orbits ranging out as far as 600,000 miles. The resulting resolution of 1/1000th of a milliarcsecond-or one microarcsecond, would enable us to image activity in the center of our Galaxy-believed to be due to a black hole-very nearly down to the black hole itself. It would also provide images of larger, more massive black holes suspected to he at the centers of several nearby galaxies.

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A long-baseline optical space interferometer composed of two or more large telescopes separated by 300 miles would also provide resolution of 1 microarcsecond, although not complete information about the image. This resolution would permit us to detect a planet no lager than Earth in orbit around a nearby star (by means of its gravitational pull on the star) and to measure the gravitational deflection of light by the Sun as a high-precision test of general relativity.

A high-sensitivity x-ray facility, having about 100 times the collecting area of the planned Advanced X-ray Astrophysics Facility, could be assembled in orbit. A space station-serviced x-ray observatory would make possible the detection of very faint objects, such as stellar explosions in distant galaxies, as well as high-spectral resolution of brighter objects. This would make possible a study of x-ray signatures of the composition, temperature, and motion of emitted gases. For example, the theory that most heavy elements are produced in supernovae can be tested by studying die gaseous ejecta in supernova, remnants. A hard x-ray imaging facility with a large (1,000 square feet) aperture is needed to study x-rays with energies in the range from 10 KeV to 2 MeV. Sources of such radiation are known, but are too faint for smaller-aperture instruments to analyze in detail. It is important to find out whether the known faint background radiation at these energies is coming from very distant objects, such as exploding galaxies, or from gas clouds heated by the stellar explosions that accompany galaxy formation.

The future development of gamma-ray astronomy will depend upon the results of planned gamma-ray observatory, but it is anticipated that larger collecting areas and higher spectral and angular resolution will be needed to sort out the sources and carry out detailed spectroscopy. Cosmic-ray studies will require a superconducting magnet in space with 1,000 square feet of detectors to determine the trajectories of individual particles and hence their energy and charge.

The great observatories of the next century will push technology to its limits, including the capability to assemble large structures in orbit and on the Moon, the design of extremely rigid structures that can be tracked and moved with great precision, and the development of facilities on the Space Station for repairing and maintaining astronomical facilities in orbit. Because of the huge information rates anticipated from such observatories, great advances in computing will be required, especially massive data storage (up to 100 billion bits) accessible at high rates. The preliminary analysis of the data will be performed by supercomputers in orbit, transmitting only the results to the ground. The program will require a long-term commitment to education and support of young scientists, who will be the life blood of the program, as well as the implementation of high-priority precursor missions, including first-generation great observatories and moderate-scale projects.

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

(MISSING PICTURE)

Astronomers use a variety of instruments to study events and objects in the universe. Some of these are visible to the naked eye, but many can be seen and understood only by Studying images derived from other segments of the electromagnetic spectrum, (COURTESY RON MILLER)

and leadership at every level. The result will be a prize worthy of the ages, one which integrates the findings of many diverse disciplines of science into a comprehensive understanding of the cosmos which will provide humankind with a new perspective on our place in the Universe.

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Earth is the only one of our Solar System's nine planets that we know harbors life. Why is Earth different from the other planets? Life as we know it requires tepid liquid water, and Earth alone among the bodies of the Solar System has had that throughout most of its history.

Biologists have long pursued the hypothesis that living species emerge very gradually, as subtle changes in the environment give decisive advantages to organisms undergoing genetic mutations. The recent discovery that the extinction of the dinosaurs (and many other species as well) some 65 million years ago appears to have coincided with the collision of Earth with a large object from outer space-such as a comet or asteroid-has led to new interest in "punctuated equilibrium."According to this concept, a drastic change in environment, in this case the pall cast upon Earth by the giant cloud of dust that resulted from the collision, can destroy some branches of the tree of life in a short span of time, and thereby open up new opportunities for organisms that were only marginally competitive before. The story of the evolution of life on Earth-once the sole province of biology–us depends in pan upon astronomical studies of comets and asteroids which may collide with our planet, the Physics of high-velocity impact, and the complex processes that govern the movement of dust in Earth’s atmosphere.

Atmospheric scientists are finding that within such short times as decades or centuries the character of life on Earth may depend upon materials originating in the interior of the planet (including dust and gases from volcanoes), chemical changes in the oceans and the atmosphere (including the increase in carbon dioxide due to agricultural and industrial activity), and specific radiations reaching us from the Sun (such as the ultraviolet rays which affect the chemical composition of Earth's atmosphere). Through mechanisms still not understood, changes in Earth’s climate may in turn depend upon the evolution of life. It has become apparent that fife on Earth exists (in a complex and delicate balance not only with its own diverse elements, but with Earth itself, the Sun, and probably even comets and asteroids. Interactions among climatology, geophysics, geochemistry, ecology, astronomy, and solar physics are all important as we contemplate the future of our species; space techniques are playing an increasing role in these sciences.

Space techniques are also valuable for studying Earth's geology. The concept of continental drift, according to which the continents change their relative positions as the dense rocks on which they rest slowly creep, is proving to be a key theory in unraveling the history of Earth as recorded in die layers of sediments bud down over millions of years.

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CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

Are we alone in the Universe? Virtually all stars are composed of the same chemical elements, and our current understanding of the process by which the Solar System formed suggests that all Sun-like stars are likely locales for planets. The search for life begins in our own Solar System, but based on the information we have gleaned from robotic excursions to Mercury, Venus, the Moon, Mars, Jupiter, Saturn, and Uranus, it now appears that Mars, and perhaps Titan, a moon of Saturn, are the most likely candidates for the existence of rudimentary fife forms now or in the past.

The existence of water on Mars in small quantities of surface ice and in atmospheric water vapor, and perhaps in larger quantities frozen beneath the surface, leaves open the possibility that conditions on Mars may once have been favorable enough to support life in some areas. Samples returned from regions where floods have occurred may provide new clues to the question of life on Mars.

Titan has a thick atmosphere of nitrogen, along with methane and traces of hydrogen cyanide–one of the building blocks of biological molecules. Unfortunately, the oxygen atoms needed for other biological molecules are missing, apparently locked forever in the ice on Titan's surface.

How do we search for planets beyond our Solar System? The 1983 Infrared Astronomy Satellite discovered that dozens of stars have clouds of particles surrounding them emitting infrared radiation; astrophysicists believe that such clouds represent an early stage in the formation of planets. Another technique is to track the position of a star over a number of years. Although planets are much less massive than stars, they nevertheless exert a significant gravitational force upon them, causing them to wobble slightly. Through a principle called interferometry, which combines the outputs of two telescopes at some distance apart to yield very sharp images, it should be possible to detect planets-if they exist-by the perturbations they cause as they orbit nearby sun similar to our Sun. With sufficiently large arrays of telescopes in space we might obtain images of planets beyond the Solar System. By searching for evidence of water and atmospheric gases we might even detect the existence of life on those planets.

If life originated by the evolution of large molecules in the oceans of newly-formed planets, then other planets scattered throughout our Galaxy could be inhabited by living species, some of which may possess intelligence.

If intelligent life does exist beyond our Solar System, we might detect its messages. The Search for Extraterrestrial Intelligence, or SETI, is a rapidly advancing field. For several decades it has been technically possible to detect radio signals (if any) directed at Earth by alien civilizations on planets orbiting nearby stars. It is now possible to detect such signals from anywhere in our Galaxy, opening up the study of over 100 billion candidate stars. Such a detection, if it ever occurs, would have profound implications not only for physical and biological sciences, but also for anthropology, political science, philosophy, and religion. Are we alone? We still do not know.

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An optical image of the disk of dust around the nearby star Beta Pictoris. The disk may represent the first stage of the formation of a planetary system around the star. (COURTEST R. TERRILE AND B. SMITH)

EXPLORING, PROSPECTING, AND SETTLING THE SOLAR SYSTEM

Our drive to explore comes first from our human curiosity, a central attribute of intelligence. Closely following that urge to know, to understand, to see and touch with our own senses, there comes the practical desire to make use of what we learn.

Exploration, settlement, and enterprise are closely connected actions. Throughout the history of all three activities on Earth, we have explored both to search for scientific truth and to find valuable resources. We settled new territories not just to "be there," but to extend our presence on a permanent basis, generally to work at productive enterprises. In exploring and settling the inner Solar System, we expect the same close connections to prevail, because they make as much sense in space as they continue to do on Earth.

In the next section, Space Enterprise, we discuss commercial activities in space and the productive benefits of using the energy and material resources of space. This section focuses on discovery and exploration. We must keep in mind that space resources are already benefiting exploration and will do so even more in the future. Solar energy is a full-time resource everywhere in space except in the shadows of planets. Supplemented by nuclear generators when necessary, it powers the sensors, the computers, and the radio transmitters of the robotic spacecraft that we have sent ahead of us as our scouts to examine the planets and moons of our Solar System. Future research outposts, like today's major observatories in remote regions of Earth, will use local resources wherever possible to minimize costs. Once again by analogy to Earth's history, most of the people who pioneer the inner Solar System in the 21st century will do so to work at jobs based on the resources of space.

We must therefore transform the way that we operate in space both for science and for industry. The few short forays of humans beyond low Earth orbit repeated in method and

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

spirit the early polar expeditions. Each was a quick dash, lasting only a few days, supported entirely by stores of food, water, air, and fuel lifted from the home base. As we move out farther, stay longer, and establish first outposts, then bases, then long-term settlements, some for scientific goals and others for production based upon space resources, we must "live off the land" for both energy and materials in order to reduce our costs of operation. In testimony before the Commission, there was remarkable unanimity on the need to develop indigenous resources to sustain the flow of settlement and enterprise stemming from initial periods of exploration. As phrased in one presentation to the Commission:

For exploration and settlement, cutting the apron string to Mother Earth is necessary because we must otherwise support operations at the end of an increasingly long supply line. The logistics problem in space has its analog in the challenge of climbing Earth's highest mountains. Here on Earth, we five at the bottom of one of the deepest gravitational wells of the inner Solar System. Everything we hoist into space from Earth must be lifted out of a gravitational well 4,000 miles deep. By contrast, lifting materials from the Moon requires climbing a well only 180 miles deep. In recent years asteroids have been discovered which can be reached with even less cost in energy than traveling to the Moon. Finding them confirmed that the inner Solar System is a treasure trove of materials, available to support pioneers on the space frontier, Lunar, asteroidal, and planetary materials are valuable where they are found, and valuable also in "free space" which is the modem analog to the high seas (See page 61).

Exploration and settlement have an additional close connection because the distances we must traverse to reach all objects in space beyond our Moon are so great, and the times required to reach them are so long, that humans can best travel to them in ships that are much like movable settlements. What we learn about long-term fife support in space will therefore be of value to us not only to support our exploration of the Solar System, but also for building the settlements necessary to support the space industrial activities of the 21st century. Explorers throughout Earth's history could see only short distances ahead. The unknown, and with it often unknown dangers, lay just beyond the next headland or over the next mountain range. For that reason the charts of our nearly spherical Earth were built up only slowly and painfully over centuries, until flight wits achieved. In space exploration we are already past that stage, because we can look outward in any direction through the transparent medium of space itself. There will be many surprises in detail, but we know in general which bodies are of potential interest. From the smallest to the largest, with some overlap of size, they are cornets, asteroids, moons, and planets.

EXPLORING, PROSPECTING, AND SETTLING THE SOLAR SYSTEM

To lift payloads in Earth's gravitational field and place them in orbit, we must expend energy. We generate it first as the energy of motion-hence the great speeds our rockets must attain. As rockets coast upward after firing, their energy of motion converts, according to Newton's laws, to the energy of height. In graphic terms, to lift a payload entirely free of Earth's gravitational clutch, we must spend as much energy as if we were to haul that payload against the full force of gravity that we feel on Earth, to a height of 4,000 miles.

To reach the nearer goal of low Earth orbit, where rockets and their payloads achieve a balancing act, skimming above Earth's atmosphere, we must spend about half as much energy-still equivalent to climbing a mountain 2,000 miles high.

Once in "free space," the region far from planets and moons, we can travel many thousands of miles at small expenditure of energy.

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CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

Astronaut Gene Ceman walking in the Taurus-Littrow region of the Moon in December 1972. (COURTESY NASA)

To obtain a great value in knowledge from a small investment, we should send robotic explorer probes to the Moon equipped with sophisticated sensors. It is a first priority to search the permanently shadowed craters near the lunar poles, where ices containing carbon, nitrogen, and hydrogen may be found. We therefore recommend: A robotic lunar polar prospector to examine the entire surface of the Moon from low orbit. The prospector spacecraft should be equipped with remote sensors to examine the polar craters. We also recommend: Probe

EXPLORING, PROSPECTING, AND SETTLING THE SOLAR SYSTEM

missions to drive penetrators into the lunar surface, for on-site analysis at particularly interesting or valuable locales and missions to return samples for analysis from regions selected from prospector and probe date. It win then be time for people to return.

Only 24 individuals have traveled as far from Earth as our nearest neighbor in space, and only 12 have landed upon it; The total time spent by humans on the lunar surface was less than two weeks, all of it in the Apollo years from 1969 to 1972. In those brief journeys a remarkable amount was learned: more than 800 pounds of soil and rock were returned to be analyzed on Earth; equipment was set up to measure heat flow from the Moon's interior, and to report Moonquakes, and meteorite impacts. Laser reflectors were set up, which have allowed us to measure changes in the Earth-Moon distance to a few inches. Metal foils were stretched like sails to catch the wind of protons and heavier elements streaming from the Sun. And with electric roving vehicles, astronauts explored outward from their landing sites. But the 12 men who trod the lunar surface in the course of six Apollo missions could not venture more than five miles from their landed spacecraft. Quite literally, they could do no more than scratch the surface of the Moon. We therefore recommend that: We return to the Moon, not only for brief expeditions, but for longer, systematic explorations; eventually, we should come to stay.

As in the exploration of Earth, our exploration of the Moon can best proceed by a combination of visits to specific points, and the establishment of permanent outposts at locations of continuing interest. Separation of sites by purpose is more likely than the concentration of all activities at one "lunar base." Seismologists will need locations remote from mining, to achieve seismic quiet. Prospectors will need to make a series of land traverses, as is customary in resource exploration, and the promise of the lunar poles may draw prospectors at an early stage of lunar exploration. The first expeditions will make use of transfer vehicles as temporary camps on the Moon, just as the shuttle serves on each flight as a temporary space station. As more is learned and we find reasons to zero in on specific points, the temporary camps will be enlarged. Caches of food, fuel, water, and oxygen will be left there between visits and, finally, explorers will "overnight" at outposts through the lunar darkness that lasts 15 Earth days. We will return to the Moon for diverse reasons. As the first stage of the 'return to the Moon, we recommend: Establishing human-tended lunar surface outposts, primarily for a variety of scientific studies.

As revisits to the Moon become more frequent, the need will certainly grow for larger

permanent "base camps," to serve as supply centers, local research laboratories, and medical

centers for explorers taken ill or injured. One important facility will be located in lunar polar

orbit. This will give excellent access to operations, particularly near the lunar poles or on the

far side of the Moon, and good access to solar energy. Both before and after such facilities are

established, we will have reason to visit specific points on the Moon for their scientific or resource interest. Volcanic features have been observed from Earth, and may yield vital

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

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Lunar activities in the 21st century could include astronomy, both optical and radio wave, and the use of lunar material to manufacture products in space in the foreground, a mass-driver is propelling baseball-size pieces of lunar material into space. (COURTESY ROBERT MCCALL)

information on the Moon's interior. The far side of the Moon offers locations for radio astronomy, shielded from the noise of earthly radio interference by 2,000 miles of rock.

In the development of technology for more distant travels, the Moon will serve as a laboratory. Because of its very slow rotation and consequent long nighttime, nuclear plants are likely to be necessary for power to provide life support on the lunar surface. They will be tested there before similar plants are sent as far as Mars. The movable space settlements which are likely to be used for journeys to Mars and the asteroids will be put through their proving voyages by trips around the Moon. All that we learn about long-term life support and medical service to astronauts in the relatively nearby environments of lunar orbit and the lunar surface will be put to good use when we venture farther into space.

EXPLORING, PROSPECTING, AND SETTLING THE SOLAR SYSTEM

A special group of asteroids, almost unknown until the past decade, is particularly promising for exploration and resource utilization: the "Earth-crossing" group, whose orbits bring them closer to the Sun than Earth itself. About 40 such asteroids are now known, and we propose an intensive search for more members of what is believed to be a large family of these potentially valuable celestial bodies. The Earth-crossers are of more than academic interest-about five miles across, may have been responsible for our existence. About 65 million years ago that body, traveling perhaps 20 times faster than a bullet, is believed to have drilled through Earth's atmosphere and buried itself deep in Earth's surface. The resulting splash of material spread throughout the atmosphere in the form of finely powdered dust, cutting off sunlight to such a degree that, it is thought, plants died and the dominant fauna, the dinosaurs, were wiped out by starvation. That astronomical event allowed a tiny creature, the ancestral mammal, to grow, differentiate, and fill vacated ecological niches, giving rise eventually to homo sapiens.

A small number of the Earth-crossing asteroids have orbits that so nearly match Earth's that they can be reached more easily, in energy terms, than the lunar surface. Others are of interest for enterprise and settlement because they appear to contain the life-giving elements carbon, nitrogen, and hydrogen.

We have seen and tracked some of the Earth-crossers, but another group of asteroids, whose existence is still unproven, could be of even greater importance. Orbital theory suggests that asteroids may be trapped at other locations in Earth's own orbit, 600 million miles in circumference, around the Sun. Because of the unfavorable viewing angles from Earth, these "Earth-Trojan" asteroids are exceedingly difficult to spot. None has been seen. If they exist, material from them could be returned to the Earth-Moon system with almost no expenditure of energy. We therefore recommend: Expanded Earth-based and space-based searches for readily accessible asteroids; continued telescopic characterization of their surfaces; and robotic prospector missions to particularly promising asteroids.

After the accessible asteroids, the next easiest objects to reach in our Solar System are our neighboring planets Venus and Mars. Several decades of science fiction picturing Venus as a wet, steamy jungle planet were laid to rest when astronomical observations and Pioneer, Mariner, and Soviet Venera spacecraft confirmed that Venus has a poisonous atmosphere, a crushing pressure at the surface, and a temperature hot enough to melt lead. It is no place for humans. But Mars, our other nearest neighbor, is far more hospitable. Even more celebrated in science fiction than Venus, Mars turns out to be rich in surprises, mysteries, and promise.

The distance from Earth to Mars, averaging about 1,000 times as far as to our Moon, is great enough that we are more likely to visit the planet for exploration than for enterprise.

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

(MISSING PICTURE)

Olympus Mons, a mountain on Mars, is 15 miles high and 375 miles across at its base-the distance from Los Angeles to San Francisco (COURTESY JPL)

The exploration of Man therefore offers an excellent potential for cooperation between nations. Discussions have occurred looking toward cooperative U.S. soviet mars missions. In voyages to Mars orbit and to Mars itself, we can make good use of two techniques already proven in both piloted and unpiloted space travel: gravitational assists and aerobraking. A simple form of aerobraking was used for the safe return of Apollo astronauts, and the technique is also applied to reduce the orbital speed of shuttles before landing. Gravitational assists, in which the dose passages of spacecraft around planets provide a "slingshot" effect to change directions and speeds, were used in the Apollo journeys and have been essential in the Voyager encounters with the outer planets. Mars has sufficient atmosphere to provide aerobraking, and the red planet is massive enough to provide useful gravitational assists.

Comparisons of the energy required to reach the Martian moons with that required to reach the surface suggest that Phobos and Deimos, the moons of Mars, should be investigated

EXPLORING, PROSPECTING, AND SEITLING THE SOLAR SYSTEM

and some of their materials used before crews descend to the planetary surface. The Soviet Union plans to launch an international robotic prospector mission to Phobos and Deimos in 1988. Phobos, the larger moon, circles Mars at a distance of only 6,000 miles, closer than New York is to Australia. The period of time taken for one orbit of Mars by Phobos is correspondingly short, less than eight hours. Deimos orbits about three times as far away, with a period of 30 hours. Phobos is so dose that it can become a natural space station, a potential location for an early base camp. Its color is very dark, suggesting that it may be a captured asteroid rich in carbon. Similar meteoritic material indicates that nitrogen and hydrogen are found with the carbon. If that is true in the case of Phobos, it could become an ideal refueling depot for descents to the planetary surface and for the return of spacecraft to the Earth-Moon system. Both moons are tiny, just 12.5 and 7 miles across; their gravities are weak and their shapes are lumpy and irregular. By contrast, Earth's Moon is about 250 times bigger than Phobos, with more than 15 million times its mass. A weak gravity can be an advantage: one need not "land" on Phobos or Deimos, but rather "dock" with them, as with an asteroid.

Mars has remarkable similarities to Earth, but in other respects is more like our Moon or Mercury. The Martian day is just over 24 hours long. Mars has polar caps of carbon dioxide (dry ice) and water ice which advance and retreat with the seasons, and its gravity is about one-third -of Earth's, intermediate between -our own and our Moon's. The U. S. Viking landers that set down on Mars in 1976 transmitted television images showing a pinkish sky, rolling hills covered by a reddish-gray soil, and a foreground scattered with numerous rocks. One could find in desert regions of the American Southwest, Australia, or North Africa, landscapes reminiscent of Mars.

The red planet retains a thin atmosphere with less than one percent of the density at Earth's surface. The atmosphere is mainly carbon dioxide, with traces of argon and nitrogen. Thin as it is, the Martian atmosphere supports winds powerful enough to carry dust and sand, and there are years when dust storms persist for months over-much of the planet. Clouds, fog, and frost have been seen, and wisps of clouds frequently trail from the top of the highest Martian peak, giant Olympus Mons. Surface temperatures on the planet range from + 68 degrees Fahrenheit in winter at the poles, to a summer record high of + 68 degrees in an oasis" near the equator, but at most places Martian temperatures are perpetually far below freezing.

Mars has impact craters, but it is also a world of immense canyons, volcanoes, sand dunes,

and polar caps of water ice and dry ice. Television images from robot spacecraft orbiting Mars found vast erosional features, quite possibly formed by the swift flow of liquid water. If so, Mars must once have been far warmer and wetter than it is now. Its carbon dioxide atmosphere may have been much thicker in its early history, trapping the Sun's heat by "the greenhouse effect." There is evidence for the existence of. permafrost and of liquid water about a mile below the surface at high latitudes, and water ice appears to underlie the northern dry ice polar cap.

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

The two Viking landers carried out chemical and biological experiments which detected no organic compounds. Although this tended to deny that life as we know it exists at those landing sites, the chemical reactions of the Martian soils resembled those which, it is now believed, may have been the precursors to life on Earth. As we learn more about Mars, we are likely to gain further insights to an important question: Is the origin of life commonplace in the Universe, and does it occur under a wide range of conditions? Or is it an extraordinarily rare event, which takes place only when everything about a planet is just right for it?

The distance of Mars, its gravity and atmosphere, and its tiny moons suggest a relatively

complex Plan for its exploration. The beginnings of that program have already been carried

out by spacecraft in the 1960s and 1970s. A major step forward wi1l be taken in 1989 when

the Soviet space probe approaches Phobos and Deimos, firing laser beams at them to blast off

tiny Puffs of vapor for chemical analyses. Someday in the future, a new generation of robotic

spacecraft, aerobraking in the Martian atmosphere to circularize their orbits, can return to

Earth extremely detailed television images of the surface. Later, robotic hard landers can be

targeted to potential Mars landing sites to carry out more detailed analyses of surface and

subsurface soils in a search for water and other materials to support human habitation. It will

be necessary to follow up these remote sensing missions by returning samples from Mars and

its moons.

One Of the most revealing exploration opportunities on Mars would be a journey by an automated rover vehicle down the length of one of the sinuous, water-carved channels that abound on the planet. Visual examination of the strata on the channel walls, or, even better, chemical examination, would yield information of a richness and complexity paralleling the data from an oil well drill core or the record of tree rings on Earth. This would be a Particularly rich area in which to renew the search for evidence of fife on Mars.

Sometime in the early decades of the 21st century we will establish permanent base camps either on the Martian surface or in orbit, possibly on Phobos. Exploratory journeys from Earth will then become routine, and will involve a series of cargo and crew transfers between vehicles considerably more complex than the maneuvers carried out for each Apollo mission. The people chosen for a mission will ride to an Earth-orbiting space station. From the space station they will move to a Libration Point Spaceport and then into a transfer vehicle capable of matching orbits with a cycling spaceship, repeatedly shuttling between the Earth and Mars systems. On the "cycler" they will experience a rotational gravity somewhere between that of Earth and Mars, possibly starting at an Earth-normal gravity and shifting to that of Mars in the List weeks before the cycler reaches its dose encounter with the red planet.

Nearing Mars after a half-year voyage, the expedition will move into another transfer vehicle to make the transition to an orbiting spaceport or a base camp. There, after meeting and exchanging information with a crew that can provide current advice on Martian conditions, the expedition will transfer to a lander. The short trip to the surface will have as its destination either

EXPLORING, PROSPECTING, AND SETTLING THE SOLAR SYSTEM

a major base camp or an outpost with a cache of supplies and equipment. Once on the surface, the expedition members may separate to carry out individual missions:

(MISSING PICTURE)

A Mars settlement in the 21st century with a Mars lander (in the foreground) arriving from the Mars Spaceport; and another Mars lander (in the background) departing. (COURTESY ROBERT MCCALL)

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

A biosphere is an enclosed ecological system. It is a complex, evolving system within which flora and fauna support and maintain themselves and renew their species, consuming energy in the process. A biosphere is not necessarily stable; it may require intelligent tending to maintain species at the desired levels. Earth supports a biosphere; up to now we know of no other examples. To explore and settle the inner Solar System, we must develop biospberes of smaller size, and learn how to build and maintain them.

In order to grow food crops and the entire range of plants that enrich and beautify our lives, we need certain chemical elements, the energy of sunlight, gravity, and protection from radiation. All can be provided in biospheres built on planetary surfaces, although normal gravity is available only on Earth. These essentials are also available in biospheres to be built in the space environment, where Earth-normal gravity can be provided by rotation. Both in space and on planetary surfaces, certain imported chemicals will be required as initial stocks for biospheres.

Within the past two decades biospheres analogous to habitats in space or on planetary surfaces have been built both in the U.S.S.R. and in the United States. An example of biosphere technologies can be seen at the "Land" pavilion at the EPCOT Center (Experimental Prototype Community of Tomorrow) near Orlando, Florida.

Specialists in biospheres are now building, near Tucson, Arizona, a fully dosed ecological system which will be a simulation of a living community in space. It is Called Biosphere II. Its volume, three million cubic feet, is about the volume over a land area of four acres with a roof 20 feet above it. Biosphere II is much more than greenhouse agriculture. Within it will be small versions of a farm, an ocean, a savannah, a tropical jungle and other examples of Earth's biosystems. Eight people will attempt to live in Biosphere II for two years.

The builders of Biosphere II have several goals: to enhance greatly our understanding of Earth's biosphere; to develop pilot versions of biospheres, which could serve as refuges for endangered species; and to prepare for the building of biospheres, in space and on planetary surfaces, which would become the settlements of the space frontier.

geological, with instruments newly brought from Earth; exploratory, using roving vehicles permanently left on Mars; or atmospheric and geographical, using remotely piloted or passenger-carrying aircraft capable of much closer passes over the terrain than would be prudent for machines guided only by computers.

Nearly all of the spacecraft and habitation modules needed for Martian expeditions and

EXPLORING, PROSPECTING, AND SETTLING THE SOLAR SYSTEM

for eventual permanent human settlements on Mars will have been proven out in the much closer environment of the Earth-Moon system. Enclosures containing an atmosphere like Earth's and covered over by soil as protection against solar flares, will satisfy the same needs on Mars as on the Moon (See page 70). Greenhouse biospheres for growing food will have been tested on the Moon or in Earth orbit, where a failure will mean only the call for a resupply mission, taking just a few days. Nuclear reactors, which are appropriate sources of energy during planetary nighttimes, will have been checked out both on the Moon and in orbit. Transfer vehicles are likely to be identical at both ends of the Earth-Mars transportation link, and even landers for the Moon and for Mars may differ only in minor details.

Mars has been for centuries a magnet to our curiosity and our imagination. Within the next few decades it will become a relatively familiar outpost of human civilization, comparable perhaps to the Antarctic settlements now maintained permanently by several countries. The permanent settlement of Mars, even if by a relatively small number of people, win be a later milestone, though not the last, in the human settlement of the inner Solar System. In that sense it will be, in Winston Churchill's phrase, "the End of the Beginning."

In the early years of pioneering the space frontier, people will go to specific sites of action for specific assignments. The choice of carrying out assignments by tele-operation, by autonomous robots, or by human crew members is likely to be governed both by economics and by subjective and national pressures, as in the past. By the terms of treaties which the United States has signed, no claims of national sovereignty are to be made on the planets, moons, or asteroids, so "Planting the flag" does not have the same symbolism in space as on Earth.

When the enabling technologies are in place for the private sector to begin substantial operations in space, political motives for the choices among piloted, robotic, or remotely controlled methods of carrying out operations are likely to become less important, and economy and efficiency are likely to dictate to a greater degree how things are done.

For survival and good health, humans who must work in space or on planetary surfaces for long periods of time will have five material requirements: air, water, food, gravity, and protection from cosmic and solar radiation. The water cycle has been partially closed already on Soviet space stations, and they have made progress toward recycling air. For long-duration voyages of at least several months, it will be economic to grow rather than carry food.

The equivalent of Earth gravity, in which our bodies have evolved and probably work best, can be provided relatively easily in free space, but not on the surfaces of any of the moons or planets accessible to humans in the inner Solar System. In space, gravity's equivalent can be provided by connecting a spacecraft or habitat to a tether cable and counterweight, and rotating one about the other (See page 126). Once set rotating, the dual-mass system requires no further

CIVILIAN SPACE GOALS FOR 21^ST-CIINTURY AMERICA

energy to maintain its rotation. We recommend that: Relatively simple experiments in space be performed soon to find the effects of various rotation rates and levels of artificial gravity on people so we can establish practical design parameters.

The fifth and last requirement for human survival and safety is protection from damaging radiation. Large amounts of shielding are needed to reduce radiation to the levels common on Earth. Fortunately, any material whatever is suitable as a shield. The surface material from any moon, asteroid, or planet will do. The slag from industrial processing activities is equally usable. For the short trip to the Moon, it was common practice in the Apollo years, and will be again, to rely on solar flare forecasting rather than shielding. For the half-year voyages to Mars or the asteroids, astronauts will retreat to shielded "storm shelters" in their spacecraft when solar flares occur. The need for heavy shielding on long voyages is one of the reasons for using "cycling spaceships" on what may come to be called the "Mars Run."

On or near an asteroid, and on the surfaces of the Moon and Mars, there should be no difficulty in providing ample shielding using the local surface material. In orbital space, the same level of shielding can be provided economically when material transporters with very low operating costs and high capacities are available. The electromagnetic "mass-driver," described on page 103, is one candidate for that service. It seems likely that settlements in space itself, built to house the workforce needed to control industrial activities, will be shielded by the slag from industrial operations. With such shielding orbital settlements can be made as safe from cosmic and solar radiation as the surface of Earth.

There will be a need for long-term human settlements in orbit and, at some point, on the surfaces of the Moon and Mars. The five requirements for human health can be provided at any of those locations, with the one caveat that Earth-normal gravity can be provided easily in space, but not on the Moon or Mars.

We have focused. on the "mechanistic" questions of air, water, food, gravity, and protection from radiation. For the space frontier to become attractive to human pioneers it will be necessary to bad settlements with additional Earth-like characteristics: Normal intensities of sunshine and gravity, a normal day/night cycle, the same area and volume per Person that are normal in comfortable urban environments, and plenty of area and volume for growing flowers, grass, and trees. Conceptual engineering studies confirm that attractive settlements of this kind can be built in orbital space, where full-time solar energy is available for power and where the day/night cycle of sunshine can be provided by shading incoming sunlight on a regular schedule. Settlements in orbit will not be locked into planetary rotations, and will therefore be able to "point" toward the Sun at all times. When all the questions of health, safety, economy, and comfort are considered, the optimal shape for settlements in orbit appears to be spherical, with a pressure shell rotating within a non-contacting outer spherical shell of shielding. Such habitats could accommodate thousands of people.

As we look forward to pioneering the space frontier, we can speculate on the far-reaching human consequences, which many people see as loftier than the economic and scientific Payback from all space missions. This is the extension of life itself beyond the precious and fragile planet where it was born, to the far reaches of the inner Solar System. As in all previous pioneering, only the adventurous will choose to leave the familiar territory of

EXPLORING, PROSPECTING, AND SETTLING THE SOLAR SYSTEM

home and strike out for the frontier. Historians have written that many of the characteristics we are proudest to call "American" were shaped by the frontier environment of our ancestors. Many children and young people today expect and anticipate that they will five and work in space. We can be confident that they will be fully as capable of taming that new frontier environment as were our ancestors who built America.

The space frontier will be viewed by the financial and business communities in the same way that other investment opportunities are viewed. For any space products or services similar questions will be raised: How big are the markets? Are they stable and predictable, or vulnerable to arbitrary decisions by our own or other governments? What is the competition? Is that competition bound by the same rules that bind U.S. business, or will American companies be playing against a stacked deck? What are the technical and financial risks? What are the investments required? How much will delayed returns be devalued? What incentives can be provided to reduce investment risks in the event that potential financial backers perceive them as too high? Is the payback great enough to provide, as venture capital sources may require, a five-fold return on investment when returns are three or four years away?

These are all difficult questions. None can be answered by NASA or other Government agencies; they fall within the province of the entrepreneur. Government agencies are well suited to the development of enabling technologies, however. As the history of the National Advisory Committee on Aeronautics (NACA) in the 1930s showed, participation by industry can help Government select productive technologies.

Although the Government continues to be the primary source of funding for space technology advances, a small but growing and cost-effective infusion of private investment will be attracted if new financial mechanisms are established to overcome the high barriers of risk and delay that are endemic to space enterprises. The payoff for the United States from the development of such financial mechanisms is potentially very great, because the private sector has a keen "nose" for cost effectiveness, and the United States must maintain, for economic, social,. and political reasons, its leadership in the commercial application of space science and technology.

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in the foreground, two astronauts are improving the capability of a large communications platform by installing a new dish antenna. Below them is a commercial space station in geostationary orbit (COUFRRESY ROBERT MCCALL)

SPACE ENTERPRISE

It is worth recalling that the "joint stock company," now the basis for most world commerce, was originally invented four centuries ago during the Age of Discovery to solve similar problems of high risks and delayed returns that were characteristic of early attempts to obtain value from the resources of the East Indies and the New World of the Americas. The Hudson Bay Company is still operating on the Canadian frontier.

Some of the largest corporations in the United States are involved in private satellite communications activities, exploiting a mature space technology with well-defined risks. Start-up firms are beginning to invest in developing their own space transportation, remote sensing, and microgravity materials processing systems. If current trends continue, the potential will exist for a wide array of privately financed space activities by the late 1990s. The United States should encourage these trends by maintaining an aggressive science and technology program to bolster U.S. competitiveness, by developing creative partnerships with the private sector that emphasize joint research programs and timely procurement practices, by ensuring that domestic and international regulatory approvals and other essential governmental decisions are processed rapidly, by transferring Government activities to the private sector wherever possible, and by striving to open international markets to U.S. space goods and services.

As the U.S. space program advances from Earth orbit to the Moon and then on to the planets, opportunities for the private sector will increase markedly. Like the early settlers who took advantage of wilderness forts to open the American West, we believe the private sector can make productive use of space infrastructure established by the Government.

At present, private space activities are limited to four general categories: satellite communications, space transportation, remote sensing, and microgravity materials processing. As we look forward to the 21st century, a broader definition of space enterprise will emerge. In the world of 2035, three categories of space enterprise will exist: supporting industries on Earth, space industries with markets on Earth, and space industries with markets in space.

In coming decades, privately owned and operated space vehicles may be departing on frequent flights from each of several terrestrial launch facilities to orbiting space stations and factories. The Earth launch facility will become a hub of private sector activity similar to that at today's major international airports. A full range of commercial services will be available to support launch operations.

As a result of the operational rather than research nature of future space vehicles, only small crews of specialized technicians will be required to support their launch and in-orbit operations. These services, along with vehicle maintenance and repair, may be performed by the companies that operate them. Other services and products like propellants, communications, and tracking may be provided by supporting industries. The same companies that operate and supply the

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

"Orient Express" intercontinental aerospace plane may be the companies that operate and supply Earth-to-orbit transportation using these vehicles.

Educational and recreational visits to space are likely to develop as an offshoot of the space transportation industry. The need to work in space by scientists, educators, private commercial developers, and their technicians will make the public aware of the accessibility of space, just as the early barnstormers made flight available to the public. This, and greatly reduced costs, will open the way for a full-fledged Earth-to-orbit passenger travel industry based on vehicles with higher passenger volumes, a range of amenities, and mature safety features. The number of such trips over the next 50 years is difficult to project, but the public displays a high degree of interest in space travel. Early visits will involve transportation to and from space stations or orbital trips of a few hours for observation of Earth and the heavens, eventually leading to the construction of educational, recreational, and resort facilities by private industry.

In addition to large industries based on space technologies, it is important to consider more diverse individual endeavors. Many people from non-aerospace fields are turning to space as a career. In the 21st century, young professionals will view space as a new arena in which to develop their careers. Space doctors and medical researchers will be challenged by the Physiological effects of prolonged weightlessness on the human body. Researchers in the interactive human sciences will study human adaptation to alien worlds and environments. Space architects, environmental engineers, and human factors engineers will join together to design remote living and working quarters. Virtually every trade and discipline will be involved in space endeavors, from obstetrics to insurance.

Launch insurance is an extremely serious problem now. U.S. launch service companies using current vehicles may have to compete with foreign launch services that offer Government-backed launch insurance. In the long run, we feel that the best solution to this problem lies 'in developing launch vehicles to a high degree of reliability.

As the viewpoint for observation or radio transmission moves farther away from Earth, more of the planet's surface can be covered. For those Earth businesses such as television broadcasting, which must reach a large audience, a viewpoint in space has important advantages.

The first space enterprise to reach economic viability was satellite communications. Most communication satellites are in geostationary orbit, the position where their orbital rotation equals the rotation rate of Earth. In that orbit they seem to lock into position over one equatorial spot from which they can relay electronic messages from one point on Earth to another, including telephone calls, electronic mail, and television broadcasts.

SPACE ENTERPRISE

Future developments in space-based communications and information systems will continue to revolutionize our daily lives at home and at work. The large backyard communications dishes of the 1980s will give way to small unobtrusive antennas. Space communications and direct broadcast equipment, which we already take for granted in the 1980s, will be augmented by electronic mail and miniature navigational terminals relatively soon. Within the next few years it will become possible to equip a car, boat, or airplane with a receiver and a display to pinpoint its exact location by satellite, allowing the provision of navigation, collision warning, fleet dispatch, emergency location, and two-way communications via satellite. These services can even be provided to small hand-held terminals powered by penlight batteries.

In addition to using generally available communication, information, and entertainment services, 21^st-century companies will be important consumers of specialized products and services. Product researchers in corporate laboratories on Earth will be in constant contact with their colleagues in space as they jointly develop new products and manufacturing techniques. Companies will own specialized terminals to control the behavior of remote factories and experiments hundreds of miles overhead. Businesses will use advanced video and teleconferencing equipment in their offices to conduct video meetings with employees or customers on Earth and in space.

Another space industry currently in the early stages of development is remote sensing from Earth-orbiting satellites. These satellites produce images of Earth as seen from orbit with state-of-the-art cameras, radars, and other special sensors. From the vantage point of space, they facilitate the observation and management of crops, mineral resources, demographic patterns, forests, fisheries, pollution, water resources, and other terrestrial activities. The United States is not alone in realizing the potential of remote sensing. International competition in the business of selling specially-tailored remotely sensed data to customers is developing rapidly. The major contender is now the French SPOT program.

In the future, remote sensing technologies will enhance our ability to produce specialized maps, manage forest reserves, fight pollution, manage natural resources, forecast potentially destructive natural phenomena, and prospect for minerals. In doing so, new industries will be created to manage, process, market, and distribute products yielded from satellite remote

sensing.

Because of the exciting benefits already demonstrated but not yet fully realized from this technique, the Commission believes that the cognizant Federal agencies must assume the responsibility of maintaining a U.S. civilian remote sensing satellite system by public or private means, or some combination thereof it is essential that the U.S. scientific and business communities have access to the data base of such a system and not be dependent upon foreign

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

remote sensing operations. The Commission therefore recommends that: The United States maintain and improve this country's civilian Landsat remote sensing system (See page 82).

(MISSING PICTURE)

Landsat image of Death Valley, California. (COURTESY NASA)

SPACE ENTERPRISE

The Commission is impressed with the power of a close partnership among Government, academia, and industry. In the case of remote sensing, the EOSAT Corporation represents a new private enterprise approach to managing the Nation's civilian remote sensing operation. We strongly believe, however, that America's success in this competitive arena will require continuing Government and academic support. We therefore recommend, that NASA and NOAA continue a strong research and development program in the field of remote sensing and that their budgets include funds for establishing five university centers to promote and support academic research in this critical field. This support should encompass providing modem image analysis systems to develop new software, funding research projects to improve remote sensing systems, and establishing fellowships to encourage graduate students to enter the field.

A third potential civilian growth industry, space-based navigation, will develop in the late 1980s and 1990s. In our highly mobile society, space-based navigation could be utilized by millions of travelers. It is possible that the growth rate of this industry will be limited only by price, product planning, and competition. The concept is a departure from the model of Government-funded technology and demonstrations preceding and leading to "commercialization." Today, while the Department of Defense is developing the NAVSTAR Global Positioning System of navigation satellites, commercial efforts are proceeding with entirely different system concepts, although the underlying principles are similar.

These early industries will be aided by advances in space transportation technology and on-orbit servicing, which will provide new options for advanced, more cost-effective designs for space hardware. It is difficult to determine today the direction that future orbital facility design may take. It is widely believed, however, that the ultimate configuration win consist of large platforms in orbit, of modular design to simplify maintenance, and with increased power to reduce the size of ground terminals.

In addition to communication, information, and navigation, which are virtual certainties for commercial growth, space may offer advantages for manufacturing unique new products. For example, some alloys cannot be produced on Earth because one metal is heavier than the other and gravity causes separation into two layers. These alloys could be manufactured in space, however, because the effects of gravity are reduced there a millionfold. Controlled gas bubbles could be dispersed throughout a heavy metal to produce a new or fight weight material, or other new techniques developed. The future products of microgravity manufacturing are still difficult to visualize, but many ideas exist. High transportation costs may limit the opportunities to low volume, low weight, high value products initially, like drugs and pharmaceutical products, high-performance electronic chips, new composites and specialty alloys, and similar products.

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

A strong interest exists in the materials community for research and development using

In the early 1960s, the Government, through NASA, developed and launched the first weather satellites. When the operation of weather satellites matured, they were turned over to the Department of Commerce's Environmental Science Services Administration, which became pan of the newly-established National Oceanic and Atmospheric Administration (NOAA) in 1970. Today, NOAA continues to operate and manage the U.S. civilian weather satellite system, comprised of two polar-orbiting and two geostationary satellites.

The Landsat remote sensing system had similar origins. Developed initially by NASA, the first Landsat satellite was launched in 1972; the most recent spacecraft in the series, Landsat 5, was orbited in 1984.

So successful was the Landsat concept that a nationwide and worldwide group of users quickly grew, encouraged by NASA and the Agency for International Development (AID). A global network of ground stations now receives and processes Landsat transmitted data, and many countries incorporate Earth remote sensing in their development projects. Over the years, Landsat has proven to be one of the most Popular forms of American foreign aid.

Although remote sensing data are provided by the United States at re1atively low cost, many user nations have installed expensive equipment to directly receive Landsat data. Their investments in Landsat provide a strong indication of the data's value.

Successive administrations and Congresses wrestled with the question of how

microgravity, but little space research has been focused on the development of commercial products. As a result, there is only a small data base of research results available to private companies. This will change as large corporations intensify their space research investment programs and as NASA and the private sector work together to make the space station effective as a research site.

The ideal space enterprise would have a stable, predictable, very large market on Earth, a potential for export sales, and once established, would not be dependent on Earth-to-orbit transportation costs to generate continuing revenues. The commercial satellite communications industry satisfies all those conditions except the first; its potential market size of several billion dollars per year is not large enough to make a substantial impact on the U.S. Gross National Product.

One highly speculative space enterprise would, if technically and economically feasible, satisfy all of the ideal conditions, including large market size. This enterprise would provide electric energy for Earth from satellites intercepting solar energy in geostationary orbit.

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best to deal with a successful experimental system that had, in fact, become operational. Following exhaustive governmental review, President Carter decided in 1979 that Landsat would be transferred to NOAA with the eventual goal of private sector operation after 7 to 10 years. Following several years of transition between NASA and NOAA, the latter formally assumed responsibility for Landsat 4 in 1983. By that time, the Reagan Administration had decided to accelerate the privatization of Landsat, but despite the rapid growth in the demand for these services, no viable commercial entity appeared ready to take it over without some sort of Government subsidy. In 1984, Congress passed the Land Remote Sensing Commercialization Act to facilitate the process.

Seven qualified bidders responded to the Government's proposal to establish a commercial land remote sensing satellite system, and two were chosen by the Department of Commerce for final competition, One later withdrew after the Reagan Administration indicated that it would provide a considerably lower subsidy than anticipated. The remaining entrant, EOSAT, negotiated a contract that included a Government subsidy and requires them to build at least two more satellites in the series. In the fall of 1985, EOSAT, a joint venture between RCA Astro-Electronics and Hughes Santa Barbara Aerospace, assumed responsibility for Landsat.

The Government's capital assistance to EOSAT is in limbo at this time because of the current budget situation, even though EOSAT was contractually targeted for such financial support. It is, therefore, too soon to say whether the Landsat privatization process will provide a successful model for the transfer of a Government-developed space enterprise to the private sector.

The total market for electricity, at the prices now common for coal or nuclear power plants, is on the order of $400 billion per year worldwide. Capturing such a market would make a substantial impact on the U.S. GNP and balance of payments.

The basic concept of solar power satellites was studied in the 1970s. Space technologies that will become available within the next 20 years offer the potential to make these systems less difficult to achieve in the 2lst century. These include improved space transportation systems, the use of lunar materials from the top of Earth's gravity well, and advanced robotics and tele-operation. There would, of course, be competition; the largest conference so far held on solar power satellites was held in Japan. The Soviet Union has announced the goal of building the first solar power satellite to supply energy to Earth in the 1990s. We feel that the United States would have sufficient technological skills and leadership to be able to dominate such a market if it develops, provided that U.S. research efforts continue.

From an environmental viewpoint, we suspect that the continued dumping of fossil fuel emissions into the atmosphere (particularly carbon dioxide) may have significant effects on Earth's biosphere. If so, nuclear power and solar power satellites would become economic competitors. It is far too early to predict that solar power satellites can undersell nuclear power, but the possibility is significant enough that we endorse a strong continuing program of research.

Sometime in the next decades, space business will begin cutting its umbilical cord with Earth. The process may begin on a small scale, for example, with the production of lunar derived oxygen to reduce the costs of operating chemical rockets beyond low Earth orbit. It win come to fruition when the first self-sustaining economy is established free of dependence on Earth for agricultural or principal industrial products. The transmission of information and entertainment, and the sale of small, complex high-value products, will link Earth to the space economies long beyond that time.

As we have noted, the Solar System is rich in raw materials, and we anticipate the eventual practicability of mining the Moon, asteroids, and the moons of Mars. This can provide future profitable opportunities for private enterprise. Non-terrestrial materials are attractive for use in space because on Earth we stand at the bottom of a gravity well 4,000 miles deep (See page 61).

If historical precedents for mining and materials purification are followed, the easiest and closest resources will be developed first, and the more sophisticated processing and distant sources developed later. The historical analog is terrestrial mining, in which minerals near the surface of the ground were used first, then deeper mines were dug. There is also a natural progression from simple processing of materials to more complex operations. In using materials found in space, at each stage of sophistication there will have to be a direct economic Payback, if "enterprise" is to have real meaning.

In addition to these natural resources, there is a potentially valuable artificial space resource that is now going to waste: the shuttle's external tanks. At present, with each successful flight of a shuttle, an empty tank with mass greater than the full payload of the shuttle itself is brought to 99 percent of orbital speed and then discarded to bum up in the atmosphere. The shuttle fleet's flight schedule suggests that over a 10-year period about 10,000 tons of that tankage will be brought almost to orbit and then discarded. At standard shuttle rates, it would cost about $35 billion to lift that mass to orbit. There are reasonable arguments, involving potential hazards and the costs of maintaining tanks in orbit over time, against saving this resource, but we feel that so great a resource cannot be ignored, and Propose that a new look be taken. We cannot set limits now on what uses could be made of shuttle tanks in orbit; ingenuity and the profit motive might produce useful ideas. One obvious use is as shielding against radiation; another possibility is mass for tether anchoring. We therefore recommend that: The potential value, risks, and costs of stockpiling shuttle external tanks in orbit be reviewed again in light of increased orbital activities to determine whether preserving a large tonnage of fabricated aluminum, steel, and other materials is desirable in the next 10 to 15 years.

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Thanks to the priceless legacy of Apollo, we already know a great deal about the nearest source of materials on the "high ground" beyond Earth. The Moon is our partner in gravitational lock. To reach it we need no "launch opportunities"-it is always there waiting for us. Here, in rough order from the simplest and earliest to the most distant and complex, is one possible progression in our use of the lunar resources: first raw lunar soil, for shielding against radiation and as propellant for mass-driver engines in space; then oxygen for rocket propellant, as the main constituent of water and our "breath of life"; next raw lunar glasses, treated physically and thermally to become strong composites for structures; next iron, to be sintered (compressed in molds and heated) into precision products; and then Silicon, for solar cell power arrays. Hydrogen is in low concentration on the Apollo sites, but its relatively higher concentration in the fine-grained lunar soils may allow its extraction. If so, it will be used both as rocket fuel and as a constituent of water. Finally there will be the separation of lunar soils into the full range of elements useful for industrial manufacturing and construction.

Apollo astronauts were the first prospectors of another world, All of the common elements they found on the Moon turn out to be useful. Oxygen is about 40 percent by weight in the lunar soils. Some have called the Moon a "tank farm in space" for that reason. Lunar oxygen solves 6/7ths of the problem of getting propellants from the top rather than the bottom of Earth's gravity well; our best rocket engines bum six pounds of oxygen for each pound of hydrogen they consume. When lunar oxygen is available for transfer vehicles operating to the Moon, the situation will be much like that of 19^th-century railroad locomotives and steamships--"transfer vehicles" which refueled with local wood and water.

Next after oxygen, in order of richness in the lunar soils, is silicon, the "power element" useful for building solar energy ways. The lunar surface soils are 20 percent silicon. Fortunately, techniques have now been developed on Earth for producing large solar arrays at low cost by the automated manufacture of thin films of amorphous silicon. Ranking behind silicon in abundance on the Moon are calcium and a number of metals. The ratios between various metals depend on the site (Mare, Highland, or other), but-typical values are 14 percent aluminum and 4 percent iron, with smaller percentages of titanium, manganese, magnesium, and chromium.

Iron is abundant at every Apollo landing site. Much of it is in the form of fine powder deposited by meteorite bombardment over millions of years. Relatively pure metallic iron -can, therefore, be readily recovered by simple magnetic separation of fine-grained lunar soils passing on a conveyor belt. The technology of powdered-iron metallurgy is wen developed on Earth, where it is used regularly to manufacture strong, high-precision machinery parts such as gears. It lends itself well to automated manufacturing.

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Hydrogen is in very low concentration in the bulk lunar soils, but as noted earlier, it is in higher concentration in the lunar "fines" (the portion of the bulk soil that passes through small-mesh sieves). The higher concentration of hydrogen was deposited in the lunar fines by

CIVILIAN SPACE GOALS FOR 21^ST-CENTURY AMERICA

millions of years of bombardment by the solar wind. Physical separation to concentrate the fines requires very little energy; heating the fines then releases small but usable amounts of hydrogen. For higher concentrations of hydrogen, and for carbon and nitrogen, we need to discover the lunar equivalent of Earth's concentrated ore deposits, if they exist. As noted previously, such deposits are most likely to be found in frigid craters, never exposed to sunlight, near the lunar North and South Poles.

The elements found on the Moon and on other bodies in space are familiar, but relatively little of our industrial experience on Earth is applicable to separating them from the lunar minerals in which they are found. To extract oxygen, several processes, both electrolytic and chemical, have been studied in the laboratory. The early results are promising enough to suggest that even a modest program of development would lead to satisfactory processes for oxygen extraction. We therefore recommend: A continuing program to test, optimize, and demonstrate chemical engineering methods for separating materials found in space into pure elements suitable as raw materials for propellants and for manufacturing. Studies should also be carried out to allow choices to be made of the most cost-effective power sources for these processes at various locations in space and on selected bodies of the inner Solar System.

The surface soils of the Moon and of many asteroids are mainly glass. Recent research indicates that those materials can be processed into structural composites-fibers in a softer matrix, analogous to fiberglass-without the need for chemical separation. Such processing would require far less energy than chemical separation processes for aluminum, titanium, or magnesium. We therefore also recommend: Research to pioneer the use, in construction and manufacturing, of space materials that do not require chemical separation, for example, lunar glasses and metallic iron concentrated in the lunar fines.

The Moon is not the only attractive site for extraterrestrial mining. Of all the material that could be found in space, the easiest to recover would be asteroids trapped in Earth's orbit around the Sun as discussed previously, but we do not yet know whether they, exist. The next most accessible mineral lodes in space are probably the Earth-crossing asteroids. We know far less about the composition of those asteroids than we do about the soils of the Moon's equatorial region, but their reflected sunlight at different wavelengths leads us to suspect -that many are stony or metallic. The most valuable would be the few thought to contain large amounts-of carbon and hydrogen.

Phobos and Deimos are potential material resources of particular interest to resupply missions to Mars. orbit or to the planetary surface. Tantalizing glimpses of the Martian moons were transtnitted back to us from NASA's Viking spacecraft. The two moons seem to be quite different in composition, and Phobos, the larger, appears to be rich in water, carbon, and nitrogen. If so, there is an orbiting fuel depot just 6,000 miles above the red planet to top off the hydrogen and oxygen tanks of visiting spacecraft.

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(MISSING PICTURE

Mining propellant on Phobos, a moon of Mars. (COURTESY ROBERT MCCALL)

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Main belt asteroids, in orbits between Mars and Jupiter, contain a rich variety of material, much of it carbonaceous. The largest asteroid, Ceres, appears to be abundant in life supporting elements as judged by reflection spectra. A total of 3,200 main belt asteroids have been catalogued so far. In the long run, the abundance of material in the main asteroid belt is enough to support a civilization many thousands of times larger than Earth's population. Those resources are so distant in miles and in energy that we have no economic drive to begin using them within the next few decades-but it is good to know that they are there waiting for our descendants in future centuries.

The best locations for processing materials into useful end products to be used in space

will be dictated not by our present imperfect guesses, but by the hard economic facts of resource locations, transport costs, energy sources, and points of utilization. Some processing might be done better in high orbit than on planetary surfaces. One reason is that solar energy for processing is at best only a half-time resource on any moon or planet because of the

day/night cycle. By contrast, solar energy is abundant and available full-time in high orbit.

Another reason is that the energy required to lift materials into orbit from a body even as

massive as the Moon is less than the energy required to process most materials. Since

planetary surfaces are resource rich, but energy poor, low-energy processes like making

composites out of indigenous glass, or extracting powdered iron magnetically, are particularly

suitable for end products to be used there.

In successful frontier nations like the United States, Canada, and Australia, both industry and

agriculture began from imported "seeds." They grew exponentially in a "culture medium"

rich in energy and materials, guided by the hard work and creative intelligence of the pioneers. Space is a similarly rich culture medium. That suggests an economical way to develop large-scale industry in space without lifting massive quantities of equipment from Earth; we call it "bootstrapping."

Robotic factories, so advanced as to operate for one or two shifts out of three without

human attendance, have been in successful operation on Earth for more than five years. One

of the earliest was a Japanese factory located near Mt. Fuji. Significantly, the factory produces

components for the robots that "man" the factory. That profitable plant requires a human

workforce to carry out maintenance on one shift, but except for that it comes dose to

realizing John von Neumann's dream of self-replicating industrial systems (See page 89).

Other factories with the same degree of autonomous operation are now operating, most of

them in Japan or the United States.

For exponential growth from an industrial seed in space, we believe that three basic

principles will apply:

(1) Replicate the same designs, as in mass production, rather than developing a complex machine and then only building a few;

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(2) Don't try for 100 percent self-replication; it is enough to use local materials for the

Factories that could replicate themselves would be attractive for application in space because the limited carrying capacity of our rocket vehicles and the high costs of space transport make it difficult otherwise to establish factories with large capacities. The concept of self-replicating factories was developed by the mathematician John von Neumann. Three components are needed for industrial establishment in space: a transporting machine, a plant to process raw material, and a "job shop" capable of making the heavy, simple parts of more transporting machines, process plants, and job shops. These three components would all be tele-operated from Earth, and would normally be maintained by robots. Intricate parts would be supplied from Earth, but would be only a small percentage of the total. Here is an example of how such components, once established, could grow from an initial "seed" exponentially, the same way that savings grow at compound interest, to become a large industrial establishment:

Suppose each of the three seed components had a mass of 10 tons, so that it could be transported to the Moon in one piece. The initial seed on the Moon would then be 30 tons. A processing plant and job shop would also be located in space-20 tons more. After the first replication, the total industrial capacity in space and on the Moon would be doubled, and after six more doublings it would be 128 times the capacity of the initial seed. Those seven doublings would give us the industrial capacity to transport, process, and fabricate finished products from over 100,000 tons of lunar material each year from then onward. That would be more than 2,000 times the weight of the initial seed-a high payback from our initial investment.

heavy, simple, repetitive components of production machinery. Small, complex, labor-intensive items like computers and precision machine tool components weigh very little. Transport costs for them do not add significantly to the total budget because those components represent only a small percentage of the total mass required; and

(3) Wherever practical, use tele-operation from-Earth to control and guide production, maintenance, and transport. Because of signal travel times, tele-operation is practical in the Earth-Moon system, but not far beyond.

Several basic components are needed for industrial growth in space; a "transporting machine," a processing machine" to convert raw materials into useful form, and a "job shop" capable of building heavy, simple, repetitive components of more "transporting machines ... .. processing machines," and "job shops." In the highly competitive world of the 1990s and beyond, when no single nation will retain any monopoly on access to space, the

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(MISSING PICTURES)

An automated spacecraft flys past an asteroid. (COURTESY PAUL HUDSON AND JPL)

winning opportunities will be those that can be developed most rapidly at lowest cost. Bootstrapping is almost surely a way to keep competitive.

Private industry is driven by its needs for return on investment to find opportunities for the fastest return. In a new business venture perceived by the financial community to be of high investment risk, future returns may be devalued by 50 percent or more for each year of interval between investment and returns. A venture which required five years from investment to returns must, in those conditions, be able to demonstrate future returns more than seven times the needed investment capital to get started at all.

That financial reality means that in practice, new business ventures can best achieve success by assembling technological building blocks industrially available at that time in novel ways rather than by investing in wholly new technologies. Such new ventures must carefully protect their proprietary rights, usually including patent protection. If protection for their contributions cannot be obtained, their financing sources will dry up. Making productive use of cast-off shuttle tankage in orbit or supplying lunar oxygen, hydrogen, or shielding mate

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(MISSING PICTURE)

An astronaut has departed a transfer vehicle for a close-up look at an asteroid. (COURTESY ROBERT MCCALL)

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rials could Provide future opportunities for entrepreneurial companies or for entrepreneurial divisions within large companies. They can do so only when the basic elements of space transportation to low orbit, and beyond to the Moon, have been developed to a reliable level under Government sponsorship.

The financial scale of new ventures has severe limits. Today a start-up requiring $10 million is large, a venture requiring $25 million is very large, and a new venture requiring over $50 million is so nearly impossible that there have been only two successful examples during the past 15 years. Yet; entrepreneurial drive tends to be found in just the small companies that face these odds and must work within such comparatively tiny resources.

These realistic limitations give us a useful insight into the new business ventures that are likely to succeed in space. They will probably make heavy use of existing robotic technology. They are almost certain to use tele-operation to reduce costs and liability. They will depend, if they are to be successful, -on ingenious new short-cuts to reach their goals. They will, if they happen at all, happen quickly. And if they are successful, they will grow rapidly, draw imitators, serve as models for later ventures, and provide material for 21^st-century business school textbooks. Every success will make it easier for future ventures to obtain financing; failures will reduce the chances for subsequent ventures. To reduce the risks to a level that will allow new ventures to attract investors, the Government could serve as a "pump-primer" as it did in the days of the early air mail contracts. NASA would-gain substantially by reducing its costs for space operations, if through contracts for lunar materials or space services it drew in the talents of companies with entrepreneurial talents.

NASA has developed, and is now providing, a financial mechanism called the Modified Launch Services Agreement, which is effective in assisting the start-up of new space ventures without becoming a drain on Federal funds. In this Agreement, launch services are provided to the leading entrant in new commercial space services, and payments are deferred to a period following launch. We recommend that: The NASA Modified Launch Services Agreement be extended, as space operations grow, to include interorbit transport services, base camp support services, and other services as appropriate.