The Future of Manned Spaceflight

AARON COHEN

U.S. manned spaceflight, a program whose technical heritage encompasses years of research in both aeronautics and rocketry, in February 1992 marked the thirtieth anniversary of America's first orbital mission. This milestone offers an appropriate vantage point from which to review the lessons of the past and to offer an assessment of how the future might unfold for this very visible, public enterprise of research and exploration on the space frontier.

After more than three decades of space exploration, America's spacefaring enterprise has evolved steadily to new levels of maturity and expertise in manned and unmanned operations on the high frontier. Our exploration of space has involved sending manned expeditions to study the moon, unmanned probes to complete what has been called the first preliminary reconnaissance of the Solar System, development of the world's first reusable manned orbiters, and the deployment of observatory-class spacecraft to study the mysteries of the universe. These vessels of exploration, both manned and unmanned, have improved significantly over the past three decades, benefiting from both the steady advance of new technologies and our growing maturity as a spacefaring nation.



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The Future of Aerospace The Future of Manned Spaceflight AARON COHEN U.S. manned spaceflight, a program whose technical heritage encompasses years of research in both aeronautics and rocketry, in February 1992 marked the thirtieth anniversary of America's first orbital mission. This milestone offers an appropriate vantage point from which to review the lessons of the past and to offer an assessment of how the future might unfold for this very visible, public enterprise of research and exploration on the space frontier. After more than three decades of space exploration, America's spacefaring enterprise has evolved steadily to new levels of maturity and expertise in manned and unmanned operations on the high frontier. Our exploration of space has involved sending manned expeditions to study the moon, unmanned probes to complete what has been called the first preliminary reconnaissance of the Solar System, development of the world's first reusable manned orbiters, and the deployment of observatory-class spacecraft to study the mysteries of the universe. These vessels of exploration, both manned and unmanned, have improved significantly over the past three decades, benefiting from both the steady advance of new technologies and our growing maturity as a spacefaring nation.

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The Future of Aerospace Today that same spacefaring enterprise is undergoing subtle but fundamental changes as it prepares for more advanced and comprehensive forays on what John F. Kennedy called "this new ocean of space." In its program to sail that new ocean, the manned spaceflight community, in particular, is moving toward a space-based infrastructure in which a permanent presence in Earth orbit, habitation of the moon, and exploration of Mars will be possible. Making use of the unique environment of space is a hallmark of this planning effort, comprising a host of new technology applications to take advantage of the microgravity and ultravacuum conditions of space, as well as the abundant resources that await us on the moon. No longer limited to singular forays into space, the program will involve a wide range of missions and capabilities, all being brought to bear on the larger goal of expanding humanity's presence out into the Solar System. Predicting the specifics of how this enterprise will evolve over the next 10 to 20 years is difficult. A similar cautionary note occurred to Neil Armstrong when he addressed a joint session of Congress a few weeks after Apollo 11. "Science has not yet mastered prophecy," he said. "We predict too much for the next year and yet far too little for the next ten." So while explicit predictions are difficult, it is possible to focus with some precision on the trends and conditions that are likely to affect the course of manned spaceflight in the next two pivotal decades. It seems likely that Al Flax, whose contributions to aerospace the National Academy of Engineering is honoring in 1992, could identify with the notion that there are many, many variables to consider in attempting to forecast aerospace trends. That steady hum always audible during Al's 10 years with Air Force Research and Development in the 1960s was the sound of one technology after another whirring past in a continuum of new capabilities, and Al's job all that time was to sort among a vast set of options and match capabilities with requirements. Among the aerospace trends that Al Flax has witnessed in his career is the ever-advancing stream of choices and options facing program managers, both in the Department of Defense and in the National Aeronautics and Space Administration (NASA),

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The Future of Aerospace with regard to the technological possibilities for meeting a given mission requirement. ''Consider the changes which have taken place in the past 25 years,'' he told the Philadelphia section of the American Institute of Aeronautics and Astronautics in 1964. "Before and during most of World War II, the only aerospace vehicle of any interest or utility to the Air Force was the subsonic airplane with a reciprocating engine power plant. Today we have in the active inventory of strategic weapons subsonic and supersonic turbojet and fanjet bombers, supersonic cruise missiles, and liquid-fueled and solid-fueled intercontinental ballistic missiles. The future holds an even greater variety of possible strategic delivery systems." Al summarized what this meant back then, and what it means today, in an axiom that still holds true: "The management of this requires that we balance many conflicting factors and throughout there is the necessity for choice." What Al saw in 1964 is certainly still one of the overwhelming realities of the aerospace business a quarter century later, and promises to be even more of a challenge in the future. That is the remarkable characteristic of our industry—to be swept along in a constant stream of technological innovation. Almost anything we engineers can conceive of doing is, in the simplest sense, technologically possible. Whether a project is politically feasible or economically viable or even desirable is, of course, another matter. Al Flax's career straddled the decades of this century when the capabilities of our technology snowballed and our knowledge base increased geometrically. One of the reasons we pause to recognize his contribution today is that he was able to see the changes in our technological outlook as they were happening. During that same speech in 1964, Al said, "In the past, projections into the future have often been characterized by axioms of impossibility in the form of limitations on the future potential of science and technology that were thought to be inescapable consequences of physical laws." By way of example, he cited the general belief during the 1930s that there was a limiting subsonic speed for aircraft, and he described how this was based on what was then known

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The Future of Aerospace about transonic drag rise and the limitation of the powerplants of the day. Al also drew from the well of history the dubious proclamation of Lord Rutherford, one of the founding fathers of nuclear physics, who, only seven years before the first fission reaction, predicted that humankind would never harness the energy of the atom. Since that time, however—and Al was tapping into this as early as the mid-1960s—"the tendency has been in the opposite direction." "We now tend to believe," he said, "that science and technology can (still operating within the laws of physics) achieve almost any desired result, given enough money and competent people. And it is true that the range of technological possibilities open to us is now very large and steadily growing larger. The test that we now have to apply in making decisions to initiate new developments is increasingly not 'can it be done' but 'do we want it more than something else which is also doable?'" There, in one tidy nutshell in the spring of 1964, in the Pick-Carter Hotel in Cleveland, Al Flax put his finger on the reality of U.S. manned spaceflight—past, present, and future. There is, on the one hand, the purely technical consideration consisting of that which you can do and that which you cannot yet accomplish. On the other hand, there is the political process, which in the case of staging a program for human exploration of space, consists of that which you have the necessary national resolve to undertake and the appropriate political coalitions to accomplish. Those forces do not tend to interact gracefully, and that is one reason why America's space enterprise is often the subject of a contentious and rather high-pitched debate. Forging a consensus on space exploration is difficult. There are many interests and priorities competing for limited resources. This country's total investment in the civilian space program since the creation of NASA in 1958 has been, in 1990 dollars, $410 billion. That is a considerable sum to be sure, and I know history will judge that it has been money well spent. The White House Office of Science and Technology Policy recently concluded that at least one-third of America's economic growth in the past 50 years has been the direct result of investment in science and technology programs. There is a payoff to the

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The Future of Aerospace programs NASA pursues. But the payoff is not always immediate, nor is it always easy to assess. In these tight budget times, space exploration becomes an easy target for reductions. So if we are going to address the future of manned spaceflight, we have to recognize at the outset that here is an enterprise that not only has to navigate in outer space but also has to ply that somewhat murky realm where capabilities, budgets, policies, politics, and the media all meet. If I might suggest an axiom here, it would be that the greatest challenges of manned spaceflight, now and in the foreseeable future, do not begin at the launch pad. One must get to the launch pad first. Another truth that should be addressed in this discussion is the reality of what we are trying to accomplish with the program for human exploration of space. It is, at its heart, an engineering endeavor. Science is a part of it; scientific knowledge will come as a result of it; but first and foremost, this is an effort to engineer our way into the future. We are creating a transportation system and an exploration capability, and that is primarily an engineering task. We have a great deal more to learn and a great deal more work to do before the essential engineering challenges of spaceflight are comfortably behind us. Assessing the future of manned spaceflight in many ways depends upon how successfully we make the case for space exploration and how effectively we argue for the necessary tools to get the job done. That is a tall order, given the nature of the debate over spaceflight. Media coverage of the Space Shuttle Program, for instance, tends to concentrate on whether a mission departs five seconds or five days late, whether there are any aggravating technical glitches, and whether or not the flight crew is feeling well. All of these are important considerations, of course, and they are of understandable interest, but in a larger sense they are superficial to the broader panorama of what we are learning and accomplishing during these missions. There is a general lack of appreciation for the technical accomplishment involved in lifting four-and-a-half million pounds of machine straight up from a launch pad—and doing it safely—which in the minds of some are two mutually exclusive propositions. In assessing where we are going with manned spaceflight, it is important to understand where we have been and what

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The Future of Aerospace we have learned. Like any largescale engineering program of long duration, the manned spaceflight program is constantly building upon its own foundations. That is probably the single most compelling reason why, from a technical standpoint, we need a space station. But before considering the construction of a destination, a place to go in low Earth orbit, let us first consider how we get there. The shuttle, which is today the planet's most reliable launch vehicle, represents essentially the third generation of U.S. manned spacecraft, but as a reusable, winged space plane, it is also a first-generation design in its own right and something of a radical departure from the designs that preceded it into space. As a flying vehicle, the shuttle is much more than simply the product of 30 years of space-age engineering. It is primarily a result of America's aviation heritage as well. In that sense, the shuttle represents a technological leap beyond the Mercury spacecraft in the same way that a Boeing 767 represents a quantum leap beyond the DC-3. It took 50 years to make that kind of leap in large transport aircraft and about 25 years to make that same kind of improvement in our manned spacecraft. In that time, we increased the weight of the vehicle more than 75 times, expanded the habitable volume from 36 cubic feet to 1,765 cubic feet, and extended the number of engineering measurements—our insight, if you will, into how the vehicle performs—by a factor of 100. The fact that the U.S. manned spaceflight program had the tools and the knowledge to accomplish this in so short a time is the product of more than half a century of steady, prudent investment in basic aerospace research and development. Since the first flight in April 1981, the shuttle fleet has logged more than 100 million statute miles and more than 300 days in space. The distance traveled in the shuttle program—in excess of one astronomical unit—is more than was logged by all previous U.S. spacecraft combined. Yet for all of that, we are still just at the beginning of developing a robust spacefaring capability. It is interesting to note, as a gauge of our actual experience in space, that a total of 11,840 days have elapsed from October 1, 1958, the day NASA opened for business, until today. In all of that time, including the most recent space shuttle flight,

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The Future of Aerospace there have been 672 days when at least one American was aloft in space. That is not an overwhelmingly impressive number when one considers the scope of the challenge ahead and the nature of the lessons that still must be learned. In all the time that has elapsed in the 33 years since NASA began exploring space, we have actually had people in space only a little more than five-and-a-half percent of the time. Yet a fundamental truism of space exploration is that we learn by doing. Time aloft helps us hone our skills. Many of the tasks we accomplish routinely today would have been well beyond the scope of our capabilities in the 1960s. A more enduring presence in space, then, is considered to be the key to advancing many of the technologies, skills, and processes necessary to fulfill the agenda that now seems likely for manned spaceflight. That agenda was set by President Bush in the summer of 1989 as we paused to celebrate the twentieth anniversary of the first lunar landing. In marking that occasion, the President proposed a long-range space exploration program that set three goals for the U.S. space program. The first goal is the construction of Space Station Freedom, to be complete by the end of this decade. The second goal is to return to the moon and establish a lunar base. The third goal is to embark eventually on manned expeditions to Mars. In that speech, what the President proposed was expanding the human presence off-planet. That is certainly something to think about. NASA has made substantial progress in pioneering new technologies to take advantage of an expanded American presence on the space frontier. In fact there are three key technologies emerging from our research into Space Station and lunar base operations. Each of the three technology applications has the potential in the years ahead to exert a profound effect on our society and on American competitiveness in the global marketplace. One application is in the field of medicine and involves recent advances with a device called the rotating wall vessel, also known as the "bioreactor." Originally developed to take advantage of the microgravity environment aboard the Space Station, the device has shown tremendous promise on the Earth in helping to understand and emulate tissue growth. Today,

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The Future of Aerospace as we seek to learn about and treat diseases and disorders in the body, we are limited to a two-dimensional understanding of how cells grow and replicate in the body. We are limited by the way those cells can be grown in a petri dish, for example, or by the laborious process involved in taking skin samples and growing new skin for burn victims. With the bioreactor, we are now beginning to learn how to grow cells as the body grows them, in three dimensions and in the form of tissue, rather than simply a collection of cells. What this suggests, for the not-so-distant future, is astonishing. For example, it may even be possible to grow whole new organs, such as kidneys, for patients who need them. These tantalizing possibilities are more than dreams. They are real. We are making great strides in the bioreactor program even as we speak, and have already conducted the first test flight in space aboard the shuttle. It is also worth noting here that the President's Council on Competitiveness last year predicted that biotechnology will grow from a $2-billion-per-year industry to a $50-billion industry within a decade. A second promising technology would also take advantage of microgravity and the near-perfect vacuum of space to produce high-quality, thin films with immense potential to the nation's semiconductor industry and other applications. The Space Vacuum Epitaxy Center, working with NASA, is now preparing for the first flight of its Wake Shield Facility aboard the space shuttle next year. The goals of the program are to produce new electronic, magnetic, and superconducting thin films both in space and in terrestrial laboratories. The key to this approach is that it would be possible to conduct these processes in a vacuum chamber without walls. Researchers believe the approach has the potential to achieve defect-free performance in superconductor production by allowing atoms to do what atoms want to do. Defect-free chip performance implies smaller chips, and the smaller the microchip, the faster its performance. It is difficult to set limits for how this technology might be applied in the future. This is the first program to characterize and use the ultravacuum of low Earth orbit. It is the first program to yield advanced technologies in thin-film processing. It is the first program to develop a U.S. free flyer platform for ultravacuum and microgravity

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The Future of Aerospace applications. All the while, the worldwide semiconductor market is growing. It now stands in excess of $40 billion a year and is expected to increase by a billion dollars a year into the foreseeable future. The third promising technology application awaits us on the moon. We know from the Apollo lunar surface samples that metals such as iron, aluminum, magnesium, and titanium are on the moon in abundance. We also know that we can process silicon and oxygen from the lunar regolith. But one other item found on the surface of the moon could ultimately surpass all of these in importance. Over millions of years, the solar wind has deposited vast quantities of the isotope helium-3 onto the surface of the moon. This isotope, which is quite rare here on Earth, has in laboratory tests shown great potential for future fusion reactions with deuterium. The energy produced from such a reaction has been comparable to those produced by reactions using tritium, but the by-products using helium-3 are completely harmless. There would be no radioactive by-product and no long-term storage and disposal problems. Fusion, of course, is a long way off. The best guess is that we are 40 years away from a workable, widespread utility network based on fusion technology. But the fusion reaction last fall in England by a European team tells us that we are making progress. Since the best estimates are that the equivalent of one shuttle cargo bay of helium-3, using fusion technology, could provide the entire U.S. energy requirement for one year, it quickly becomes a topic for serious thought and planning. If we are going to take advantage of these and a host of other technological opportunities on the high frontier, we need to move ahead with developing and settling that frontier. In considering the future of manned spaceflight, I would argue that 50 years from now, in the year 2042, when our lunar laboratories have grown into small settlements and when humans are beginning to fan out onto the plains of Mars, history will regard the decision by President Bush to engage the nation in a program of large-scale space exploration as having a resonance across the decades, and perhaps as being fundamentally more important than any other public policy decision of our time. Yet the implications of all of this, technically speaking, are enormous. Shortly after the President announced these goals, I

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The Future of Aerospace was asked by NASA Administrator Richard Truly to lead a 90-day study examining our capabilities and our options for carrying out this program. The study determined that in order to return to the moon to set up permanent scientific facilities, we will have to be able routinely to place 500,000 pounds of equipment and provisions into low Earth orbit. We will have to be able to boost that up out of Earth's gravity well and then propel it to the moon. This is the kind of task space engineers often refer to as "nontrivial." Thus far in the space age, history's two largest boosters, the U.S. Saturn V and the Soviet Energia rocket, have achieved a rated capacity of less than 250,000 pounds to low Earth orbit. A second sobering number is apparent in scenarios for getting to Mars. For each expedition, it is estimated there will be the need to place about two million pounds of equipment and provisions in low Earth orbit before we can even start the journey to Mars. Thirty years ago, Wernher von Braun envisioned a super booster called Nova, which would have dwarfed the mighty Saturn V, and would have been able to loft half a million pounds to low Earth orbit, one quarter of what we need to get just one team of explorers to Mars. Many of the other critical variables we face today in preparing for such endeavors grow out of such requirements and out of the options we will choose from to meet those requirements. Just as Al Flax envisioned, there are always choices to be made, and each choice will have its own ripple effect downstream in the twenty-first century. Consider some of the choices we face. In sizing the launch vehicles we are about to build, we must first decide between in-space assembly or direct transport of habitats to the surface of the moon and Mars. We have to choose between chemical, electric, nuclear, or other forms of propulsion. We have to a decide whether these missions will evolve over time or take the form of full-blown expeditions. Do we have the capability to build closed life-support systems? How are we going to address the issue of radiation protection and shielding, and what level of weight penalties will that entail? Should we try to perfect artificial gravity for our Mars vehicles, or invest in physiological countermeasures so that humans can thrive in zero-g for two or three years? I believe that in time the scenario suggested by President

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The Future of Aerospace Bush will come to pass. The economic implications alone of making use of a perfect vacuum, of mixing substances at a molecular level in microgravity, of achieving a better understanding of the human body, and of the promise of using the abundant resources out there in space will cause us, as a nation, to embark on a series of greater, more complicated efforts in space exploration. I also believe that we as stewards of the nation's space exploration program can have some positive influence on the way in which that future unfolds. I believe the realities of the present day suggest five things we in the space program can do to help bring about the capabilities that are now on the drawing boards of NASA. Our first task must be to tell the story of spaceflight better. We have to help the taxpayers understand what it is they are investing in, and why. We have to share our vision for the future. The second thing we have to do is to help promote a consensus and a constituency for spaceflight and for exploration. A third goal must be to move ahead with Space Station Freedom in this decade. We have to cut through the politics and the indecision and get on with it. An orbiting research laboratory is essential to our future in space. Right now, we are limited in what we can do out there on the space frontier by two things: the human body and the space environment itself. Spaceflight has a pronounced effect on the body. It affects space travelers at the cellular level, and we see changes in the heart, the lungs, the kidneys, the blood vessels, the hormone-secreting glands, and the bones. Muscles lose protein, bones lose calcium, and metabolic processes such as the production of hormones, red blood cells, and white blood cells may be altered. We cannot prudently commit to the challenges ahead until we better understand how to keep people healthy and productive out there. We also need to learn more about space basics. Even after 30 years, we still have fundamental questions about such prosaic things as paints, coatings, metals, wiring, spacecraft design, and a whole host of other considerations. The shuttle, versatile as it is, can only do so much to help us in the learning process because its "stay time" in space is limited. For these

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The Future of Aerospace and other reasons, whatever exploration architecture we may ultimately chose, the Space Station is the first crucial engineering step that must be taken. The fourth goal is to reduce the cost of flying the shuttle. These are difficult financial times, and we have to seek greater efficiencies in our spaceflight operations. To that end, NASA has embarked on a five-year program to reduce the shuttle's operating costs by 15 percent. We intend to do this while also preserving our safety margins, whatever the cost. At the same time, there is a payback from flying reusable vehicles, and we must learn to take better advantage of it. One of the main values of the shuttle is its reusability. It is that quality which has helped make the shuttle so reliable. The more we fly the orbiter fleet, the more we learn and the more understanding we have of how each system performs in a given circumstance. As we get smarter, I believe we can safely take advantage of these insights and improve the overall efficiency and operation of the system. Finally, we must make a firm commitment within NASA to hold the line on cost growth of new programs. This is difficult to do, especially within government programs, because the uncertainties of the year-to-year congressional budget process expose new programs to a series of fits and starts. Some programs are turned off and on like a light switch for years before they finally achieve any sort of stable funding. By the same token, NASA must develop a better track record of meeting cost commitments if we are to enjoy congressional support in the future as these more costly and more ambitious projects are being debated. This is one area where we have to do better. And we will do better. The future of manned spaceflight, while promising, faces many challenges. We see various technical barriers on the horizon, but that is the rule, rather than the exception, in the business of aerospace. In time, we will solve those problems and then move on to the next set of challenges. In 1951, when Al Flax signed his affidavit of appointment to a subcommittee of the National Advisory Committee for Aeronautics, supersonic flight was still a rarity, wind tunnels were still unable to emulate flight in that regime, and the computational capabilities of the time were, by today's standards, almost prehistoric.

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The Future of Aerospace It was the year that Bell Telephone gave transistors their first commercial application in a new long-distance, direct-dial telephone service; the year that Chrysler first installed power steering in 10,000 Crown Imperial sedans; the year that CBS began broadcasting in color; and the same year that a new coaxial cable carried the first transcontinental television broadcast. Today, we are accustomed to live transmissions from Neptune, delayed only by the four-hour, one-way light time to Earth. Al Flax, and most of the rest of us here today, have been fortunate to live in a time when we see old barriers falling. We have witnessed firsthand the exciting changes that technological progress has brought. As we pause to mark the contribution Al Flax has made to aerospace, and to consider the future of this industry, we can be certain only that change will be our constant companion, and that the results of our efforts will never cease to amaze us.

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