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HUMS EXPLORATION OF SPACE A Review of NASA ts 90 Day Study and Alternatives Committee on Human Exploration of Space National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1990

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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of dis- tinguished scholam engaged in scientific and engineering msearch, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Frank Press is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National _ Academy or Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievemcuts of engineers. Dr. Robert M. White is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Samuel O. Thier is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the govemment, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Frank Press and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council. This study was supported by Contract NASW4003 between the National Academy of Sciences and the National Aeronautics and Space Administration. Available from: Committee on Human Exploration of Space National Research Council Room HA 292 2101 Constitution Avenue, NW Washington, DC 20418 Printed in the United States of America

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COMMITTEE ON HUMAN~EXPLORATION OF SPACE -Members H. GUYFORD STEVER, Corporate Director and Science Advisor (Ret.), Washington, D.C., Chairman ROBERT H. CANNON, JR, Charles Lee Powell Professor and Chairman, Department of Aeronautics and Astronautics, Stanford University JOSEPH G. GAVIN, Senior Management Consultant, Grumman Corporation, Bethpage, New York JACK L. KERREBROCK, R.C. Maclaurin Professor of Aeronautics and Astronautics, Massachusetts Institute of Technology LOUIS J. LANZERO11I, Distinguished Member of Technical Staff, Physics Division, AT&T Bell Laboratories, Murray Hill, New Jersey ELLIOTT C. LEVINTHAL, Associate Dean for Research, Stanford University JAMES W. MAR, J. C. Hunsaker Professor of Aerospace Education, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology JOHN H. McELROY, Dean of Engineering, University of Texas at Arlington DUANE T. McRUER, President and Technical Director, Systems Technology, Inc., Hawthorne, California WILLIAM J. MERRELL, JR., President, Texas A&M University, Galveston ROBERT H. MOSER, Vice President for Medical Affairs, The NutraSweet Company, Deerfield, Illinois EBERHARDT RECHTIN, Professor of Engineering, University of Southern California, Los Angeles, California THOMAS P. STAFFORD, Defense Technologies, Inc., Oklahoma City, Oklahoma; Stafford, Burke, and Hecker, Alexandria, Virginia LAURENCE R. YOUNG, Professor of Aeronautics and Astronautics and Director, Man-Vehicle Laboratory, Massachusetts Institute of Technology Advisors to the Committee JAY BOUDREAU, Ballena Corporation, Los Alamos, New Mexico PETER DEWS, Harvard Medical School, Boston, Massachusetts ANDREA K. DUPREE, Center for Astrophysics, Cambridge, Massachusetts JONATHAN LUNINE, University of Arizona, Tucson, Arizona . . .

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THOMAS ~ POTEMRA, Johns Hopkins University, Laurel, Maryland THOMAS SHERIDAN, Massachusetts Institute of Technology Staff JOANN C. CLAYTON, Study Director CHRISTINA ~ WEINLAND, Project Secretary ANNA L. FARRAR, Administrative Coordinator 1V

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In Memoriam General Samuel C. Phillips, who had agreed to serve on the Committee on Human Exploration of Space and who had begun preparatory work for the study, died on January 31, 1990. He had a long and distinguished career that included directing the Apollo program from 1964 through the lunar landing in 1969, commanding the US Air Force Space and Missile Systems Organization, directing the National Security Agency, and heading the Air Force Systems Command. General Phillips later served as a Vice President for 1'RW. He performed many analyses of critical US space issues, and only recently was a valued member of a National Academy of Sciences/National Academy of Engineering study of US space policy. General Phillips' death is a great loss to the nation and to his colleagues who worked with him through the years. v

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Acknowledgments The committee wishes to thank the many individuals from industry, academia, and federal agencies and laboratories who took the time either to meet with the committee or to make their views available in other ways. NASA Administrator Richard Duly, his associate administrators and staff, along with National Space Council Executive Secretary Mark Albrecht and his staff, were very frank and forthcoming with information concerning the President's human space exploration initiative. In addition, the following individuals presented their ideas and tech- nical concepts to the committee: Lowell Wood and his associates from the Lawrence Livermore National Laboratory, who briefed us on The Great Exploration; General Richard C. Henry of Brown & Root, who discussed the Workhorse Launch System; Maxwell W. Hunter, who made a presenta- tion on the SSX, a single-stage-to~rbit launch system; Peter Wilhelm of the Naval Center for Space Technology, who explained the SEALAR concept, involving launching recoverable vehicles at sea; Michael D. Gri~n, Deputy for Technology of the Strategic Defense Organization, who discussed project management techniques; and Lt. Colonel Roger Lenard, who described a nuclear propulsion concept. A full list of invitied presenters and guests is contained in Appendix B. Thanks are in order as well to the staffs of the National Research Council (NRC) Space Studies Board and the Aeronautics and Space En- gineering Board for their help and cooperation in putting together the . . V11

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~ . VU1 ACRNOVVLEDGMEN7S study. Last, we would especially like to thank the study's Executive Direc- tor JoAnn Clayton for her thoughtful guidance at every stage and NRC Assistant Executive Officer for Special Projects Myron F. Uman for his wise counsel and constructive reviews of the draft report. H. Guyford Stever, Chairman, Committee on Human Exploration of Space

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Summary President George Bush on July 20, 1989, announced a US commitment for humans to return to the Moon and to journey to Mars; the Vice Presi- dent in his capacity as Chairman of the National Space Council (NSC) was charged with making specific recommendations about how the President's initiative could best be achieved. The National Aeronautics and Space Ad- ministration (NASA) then prepared a document, based on earlier NASA analyses, to aid in the decision-making process. Subsequently, the Vice President requested that the National Research Council (NRC) assess the scope and content of the NASA document as well as alternative approaches and various technology issues. The Vice President presented the NRC with a challenging set of questions that resulted in this report. In examining the NASA Report of the 90-D``y Study on Human Ex- ploration of the Moon and Mars and alternative concepts, the committee concluded that the appropriate framework in which to consider alternative approaches to meeting the President's initiative has at least four compo- nents. The committee's major findings and conclusions follow, presented in that framework. MISSION CONCEPTS Questions arise about the appropriate pace for the President's ini- tiative; the scope of initial human exploration missions; and the level of long-term support that will be required for what could be an unprecedent- edly long commitment to a national space goal. Development of policy, 1X

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x SUMMARY advanced technologies, and mission concepts will probably be a continu- ing and iterative process. However, there is a need for guidance at an early date regarding the scope and pace of the early stages of the Human Exploration Initiative (HEI). As directed by the President, the space station is an integral first step in the HEI, but its present design may not meet all of the requirements for the HEI. The mission concepts in the NASA 90-Day Study prudently build on proven concepts and methodical research, development, and demonstration of new technology. The concepts are comprehensive and robust, implying relatively low risk. The Great Exploration, a concept developed by the Special Projects Office of the Lawrence Livermore National Laboratory, proposes to use available terrestrial equipment, accelerated administrative and procurement procedures, and a potentially feasible technology (inflatable modules) in an aggressive approach to reach Mars at the earliest possible time, but entails relatively high risk. The concept contains technical ideas Hat should be pursued, but the committee believes it underestimates the many practical and difficult engineering and operational challenges involved. It appears likely that the eventual choice of mission architecture will incorporate the ideas from a variety of concepts, some that now exist and others that will arise in the future. One concept, for example, would place the permanent human habitat in orbit, rather than on the surface of Mars. The variety of concepts should be regarded as a "menu" of opportunities. lIUMANS IN SPACE Significant unanswered scientific questions exist concerning the fea- sibility of long-duration human spaceflight in a low-gravity environment. While it has been demonstrated that the human body adjusts remarkably well to the absence of gravity for short-duration flights, it has not been demonstrated that after long-duration spaceflight individuals can readjust rapidly to gravity without serious physiological consequences. The capa- bility to send humans into space, maintain them in a physical condition that permits them to work productively, and return them to Earth in good health is central to the HEI. A program of scientific research on the effects of microgravity on human performance and welfare is critical for determining the mission architecture for the HEI.

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SUMMARY X1 Development of technology for artificial gravity and countermea- sures to mitigate zero-g exposure should proceed in parallel with studies of the physiological effects of microgravity. An emphasis on advanced human/machine systems can enhance the productivity of humans in space and increase their safetr. TECHNOLOGY DEVELOPMENT Strategies are needed to develop and employ new technologies that will enable more rapid or cost-effective access to and habitation in space. Developing these strategies implies making trade-offs among alternative approaches. An important factor in these decisions is the level of human and technical risk that is acceptable. While major aerospace undertakings usually entail risk;, recognizing them early in the planning stages of a major initiative may help identify choices that offer opportunities to manage the risks. A balanced technology development program with emphasis on critical long-term technologies can help to reduce risks and provide important options for the future. Second to the need for scientific research and technology develop- ment to support humans in space is the need to advance national space transportation capabilities. . A new generation of heavy lift launch vehicles is needed to transport massive cargoes to low Earth orbit (LEO). ~ transport humans to space, the nation must rely on the space shuttle for at least 10 years, and it is essential that the existing shuttle fleet be maintained in a fully operable condition. A new vehicle eventually will be required to transport humans and other precious cargo to LEO, emphasizing high reliability, robustness, and efficient ground operations. Nuclear rocket propulsion could make an important contribution to the HEI if it proves feasible and safe and can gain public acceptance. 1b meet the heavy demands for power on the Moon or Mars, nuclear electric power eventually will be essential. SCIENCE GOALS Another set of considerations concerns the expansion of knowledge. While the cardinal goals for the HEI may be related to leadership im- peratives and to revitalizing the national research and development effort, important information can be gained about ourselves and our planet, about ongoing and past physical and biological processes, and about the history of the universe.

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~ . X11 SUMMARY Scientific research required to enable the initiative Includes robotic precursor missions to learn more about the Moon and Mars as well as critical studies in the life sciences. Other research opportunities can be enabled by the HEI, for ex- ample, astronomical studies from a lunar base and geological studies of the Moon and Mars. Research that may become possible because of the HEI should be evaluated in the context of research strategies for the respective scientific disciplines, and with consideration of alternative ways of conducting the research. This analysis should be based on detailed scientific discussions and strategy development. Before defining scientific research for a lunar base, evaluations are needed on the effects of an inhabited lunar environment on scientific objectives and on instrumentation. ADDITIONAL CONSIDERATIONS The committee assumed that, independent of a program for human exploration of space, a vigorous base of civil space programs will exist, including astronomical research, solar and space physics, unmanned plan- etary exploration, and Earth remote sensing, supported in the near term by both expendable launch vehicles and by the space shuttle. In addition, technology will be developed, operational experience gained, and valuable scientific information obtained by the space programs of Europe, the USSR, and Japan, as well as by our own military space programs. The climate for international cooperation is changing and is likely to continue to change. A detailed assessment is needed of the opportunities for international cooperation that may be available and the means to overcome technical and institutional barriers. It would be prudent to remain alert to future opportunities that may arise. At the same time, care must be taken that any enabling agreements are supported at the highest possible levels in the participating governments, with as much breadth as feasible, and that detailed technical agreements are not made final before all parties understand and agree on the requirements for the HEI or missions associated with it. Finally, the nation is at a very early stage in the development of an HEI. None of the analyses to date the NASA 90-Day Study, The Great Exploration, or, indeed, this reportshould be regarded as providing anything other than a framework for further discussion, innovation, and debate. The HEI is an ambitious undertaking that requires development and implementation of new technology. Accurate cost estimates are only practical in circumstances where experience with the technology exists. Currently, the technologies and the HEI mission architectures are unknown.

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SUMMARY xiii While the nation has experience with estimating costs of some aspects of HEI, derived from experience with the costs of past space systems, at this time mission cost estimates should only be taken as suggesting the rough order of magnitude of the eventual costs.

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Contents INTRODUCTION Background, 1 Procedure, 2 Approach, 3 I. ALTERNATIVE MISSION CONCEPTS The Space Station as a First Step, 5 The NASA Report of the 90-Day Study on Human Exploration of the Moon and Mars, 6 The Great Exploration, 7 Other Architectures for the Human Exploration Initiative, 9 II. SPACE TRANSPORTATION: LAUNCH SYSTEMS, PROPULSION, AND POWER Human Transportation to and from Orbit, 12 Unmanned Launch Systems, 12 Nuclear Thermal Propulsion, 14 Nuclear Electric Power, 15 III. OTHER CRITICAL TECHNOLOGIES FOR THE HUMAN EXPLORATION INITIATIVE The NASA 90-Day Study, 17 1 s 11 17

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xvi Artificial Gravity, 18 Advanced Human/Machine Systems, 19 IV. SPACE SCIENCE AND THE HUMAN EXPLORATION INITIATIVE Scientific Knowledge as a Prerequisite for Human Exploration, 22 Life Sciences, 22 Physical Sciences, 24 Research Opportunities to be Derived from Prolonged Human Space Missions, 25 V. NONTECHNICAL CONSIDERATIONS Infrastructure Considerations, 27 The Responsible Federal Entity, 27 The NASA Infrastructure, 28 International Considerations, 29 Cost for the Human Exploration Initiative, 30 VI. SUMMARY RESPONSES TO QUESTIONS POSED BY THE VICE PRESIDENT Scope of the Report of the NASA 90-Day Study, 33 Content of the Report of the 90-Day Study, 35 BIOGRAPHICAL SKETCHES OF COMMI l lE;E MEMBERS BIBLIOGRAPHY ACRONYMS, ABBREVIATIONS, AND TECHNICAL TERMS APPENDIXES A December 4, 1989, Letter from Vice President Dan Quayle to Dr. Frank Press and Dr. Press' Response B List of Participants C Excerpts from the President's July 20, 1989, Speech and the November 2, 1989, National Space Policy CONTENTS 21 27 33 39 45 49 53 58 61