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Science in NASA’s Vision for Space Exploration 3 Relevance of the Decadal Strategies and Related Reports In 1960, astronomers in the United States first undertook the task of developing consensus strategies that spanned the full range of interests of the discipline and that recommended explicit programmatic priorities for the field.1 That community has revisited the effort every decade thereafter, with its most recent work reported in Astronomy and Astrophysics in the New Millennium (NRC, 2000). Each of these efforts has surveyed the status of the field and has taken a long-term look at the most compelling directions for the field over the coming decade. This thorough planning process, now commonly known as the preparation of decadal surveys, has been applied recently to the field of solar system exploration and to solar and space physics as well, with the results presented in New Frontiers in the Solar System: An Integrated Exploration Strategy (NRC, 2002) and The Sun to the Earth—and Beyond: A Decadal Research Strategy in Solar and Space Physics (NRC, 2002), respectively.2 A decadal survey for Earth science and applications from space, now being conducted by an NRC committee to develop long-range goals and priorities for the field, is expected to be published in 2006. In addition to the decadal surveys noted above, the recent report Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century (NRC, 2003) assesses long-range scientific directions for research at the interface between fundamental physics and astrophysics.3 Several attributes of the decadal-survey process are important for this discussion: The decadal-survey process is inclusive, engaging many members of the relevant science community in open discussions and thereby building a broad consensus across that community. The scientists engaged in these discussions will be the users of data generated in research programs selected for future implementation. The decadal-survey process defines a short list of critical scientific questions or goals that should guide research and that, if addressed successfully, would have major impacts on progress in the field. That is, the surveys have identified the most notable opportunities for achieving transformational or paradigm-altering advances—opportunities that therefore should be considered in setting priorities for future research. The decadal-survey process develops priorities for future investments in research facilities, space missions, and/or supporting programs. These consensus priorities are explicit, and the surveys rank competing opportunities and ideas, clearly indicate which ones are of higher or lower priority in terms of the timing, risk, and cost of their implementation, and make the difficult adverse decisions about other meritorious ideas that cannot be accommodated within realistically available resources. 1 Their work was reported in Ground-based Astronomy: A Ten-Year Program (NRC, 1964). All of the National Research Council reports cited in this chapter were published by the National Academy (later Academies) Press, Washington, D.C., in the year indicated. 2 The surveys for the decades of the 1970s, 1980s, and 1990s were Astronomy and Astrophysics for the 1970’s (1972), Astronomy and Astrophysics for the 1980’s. Volume I: Report of the Astronomy Survey Committee (1982), and The Decade of Discovery in Astronomy and Astrophysics (1991), respectively. 3 This report, which complements the astronomy and astrophysics decadal survey, differs from a full decadal survey in the eyes of the scientific community in that it stops short of recommending specific mission and ground-based research facilities, but its treatment of science priorities is at the same level as in the other surveys.
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Science in NASA’s Vision for Space Exploration DECADAL AND OTHER STRATEGIES To illustrate the role of the decadal surveys in identifying the top-priority scientific questions for the future,4 the committee points out that Astronomy and Astrophysics for the New Millennium lists a set of five major scientific objectives to be addressed in the first decade of the 21st century. These include, “Determine the large-scale properties of the universe: the amount, distribution, and nature of its matter and energy, its age, and the history of its expansion,” and “understand the formation and evolution of black holes of all sizes” (p. 3). New Frontiers in the Solar System presents 12 key scientific questions that fit within four crosscutting themes. The questions include, How did the impactor flux decay in the early solar system, and how did this affect the timing of life’s emergence on Earth? What planetary processes generate and sustain habitable worlds, and where are the habitable zones in the solar system?, and, What hazards do solar system objects present to Earth's biosphere? (p. 3). In a similar manner, the priorities presented in the solar and space physics survey, The Sun to the Earth—and Beyond, were narrowed to eight scientific questions, including, “What is the nature of the interstellar medium, and how does the heliosphere interact with it?” and “How does Earth’s global space environment respond to solar variations?” (p. 2). Likewise, Connecting Quarks with the Cosmos posed 11 fundamental questions, including, “What is dark matter? What is the nature of dark energy?” and, “How did the universe begin?” (p. 2). In setting priorities among an array of recommended missions, the capacity to address these kinds of questions was an explicit criterion. For example, the judgments on the scientific merit of competing mission concepts reflected in New Frontiers in the Solar System were made on the basis of how missions could provide new knowledge as measured by application of the following criteria: Will answering the scientific question create or change an existing scientific paradigm? Might the new knowledge gained strongly direct future research? Will the new knowledge gained substantially strengthen understanding? Consequently, the committee concludes that the most recent NRC decadal surveys for the fields of astronomy and astrophysics, solar system exploration, solar and space physics, and the interface between fundamental physics and cosmology remain valid in the context of NASA’s new exploration vision because they do identify the critical science questions to be addressed in the next decade of space exploration. The committee recommends that these reports—Astronomy and Astrophysics in the New Millennium (2000), New Frontiers in the Solar System: An Integrated Exploration Strategy (2002), The Sun to the Earth—and Beyond: A Decadal Research Strategy in Solar and Space Physics (2002), and Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century (2003)—be used as the primary scientific starting points to guide the development of NASA’s strategic roadmaps that include these areas. In addition, the first-of-its-kind decadal survey-style study for Earth sciences and applications from space mentioned above represents a fresh opportunity to look forward as the era of the Earth Observing System program comes to an end and to consider the implications of NASA’s exploration vision for NASA’s Earth science program. Prior to the completion of that study there will also be an opportunity to apply the criteria listed above as NASA prepares its roadmap for research to understand the Earth system. Several other reports are particularly relevant for the critical scientific goals and priorities for research that must be conducted to enable human exploration. In the life sciences, the conclusions and 4 The complete sets of major scientific questions posed in the surveys are presented in Appendix A.
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Science in NASA’s Vision for Space Exploration recommendations presented in A Strategy for Research in Space Biology and Medicine in the New Century (NRC, 1998)5 remain valid today. That report surveyed the current state of research on the physiological and psychosocial responses of humans to spaceflight and identified the highest-priority questions that require attention to improve the feasibility of extended-duration human spaceflight missions. Priority areas included “research aimed at understanding and ameliorating problems that may limit astronauts’ ability to survive and/or function during prolonged spaceflight” (p. 2) and crosscutting research on musculoskeletal and vestibular physiology, radiation hazards, psychological and social issues, and plant and animal sensitivity to gravity. Finally, but equally importantly, two key studies are available that provide timely guidance about the major research issues for physical science research in reduced gravity. Microgravity Research in Support of Technologies for the Human Exploration and Development of Space and Planetary Bodies (NRC, 2000) addresses critical aspects of research to enable development of technologies that will be needed for the human exploration of space. This topic was also a key element of the study Assessment of Directions in Microgravity and Physical Sciences Research at NASA (NRC, 2003), which prioritized areas of microgravity research in terms of their strategic importance with respect to NASA’s long-term capability to pursue human space exploration. Both reports cited the need for enabling research in areas such as combustion and fire safety, multiphase flow and heat transfer, interfacial phenomena, and indirect effects of reduced gravity. Consequently, the committee concludes that already-published National Research Council studies provide highly relevant discipline-specific guidance for prioritizing critically important research that must be conducted to enable the human exploration of space. The committee recommends that these reports—A Strategy for Research in Space Biology and Medicine in the New Century (1998), Safe Passage: Astronaut Care for Exploration Missions (2001), Factors Affecting the Utilization of the International Space Station for Research in the Biological and Physical Sciences (2002), Microgravity Research in Support of Technologies for the Human Exploration and Development of Space and Planetary Bodies (2000), and Assessment of Directions in Microgravity and Physical Sciences Research at NASA (2003)—be used as a starting point for setting priorities for research conducted on the International Space Station so that it directly supports future human exploration missions. PRIORITY SETTING IN THE CONTEXT OF HUMAN EXPLORATION In NASA’s new exploration vision, the relevance of the studies cited above must be judged in the light of the presence of humans in space. The studies for astronomy and astrophysics, fundamental physics and cosmology, solar system exploration, and solar and space physics were prepared before the vision for space exploration appeared and were conducted without regard to scientific opportunities provided by human exploration beyond low Earth orbit. For example, they do not address what scientific research is required before sending explorers far from Earth, nor do they consider either the new opportunities for research made possible by human exploration or the potential incompatibilities of already-identified research with human missions. Given these new perspectives, some individual research discipline communities have begun to consider whether current priorities should be reexamined. The answers to questions about potential reassessments of priorities are likely to vary from discipline to discipline. For example, the committee does not find any compelling arguments for changing the priorities for the period 2000-2010 set forth in Astronomy and Astrophysics in the New Millennium; a forthcoming report of the NRC is expected to address the question in more detail.6 5 See also National Research Council, Review of NASA’s Biomedical Research Program (NRC, 2000) and Safe Passage: Astronaut Care for Exploration Missions (NRC, 2001). 6 “Progress in Astronomy and Astrophysics Toward the Decadal Vision,” letter report, in preparation.
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Science in NASA’s Vision for Space Exploration In the case of solar and space physics there is now an expanded rationale for using the tools and knowledge from that discipline to understand, predict, and mitigate the exposure of human explorers to harmful space radiation. Aspects of the fundamental science needed to understand the problem of space radiation were addressed in a special report that concluded that the priorities recommended in The Sun to the Earth—and Beyond (NRC, 2002) remained timely and appropriate and that there was no reason to change the recommended near-term mission sequence.7 However, a specific mission set required to develop the capability to predict the space radiation environment through which humans will fly will have to be dealt with as an aspect of crosscutting studies of enabling science called for below. It is instructive to ask how scientific priorities for exploration of the Moon and Mars might change in view of the plans to send humans to these bodies in the next few decades. Whereas scientific activities enabled directly by the presence of astronauts on the Moon or Mars are not an immediate consideration in terms of the current solar system exploration decadal planning horizon (2013), an active human exploration program will have an indirect but important impact. For example, technologies developed to support a human return to the Moon in 2020 (e.g., heavy-lift launch vehicles or nuclear power sources) could make it possible to conduct desired robotic exploration that in the most recent decadal survey was deferred beyond 2020 because the relevant technology was not available. Similarly, scientific activities undertaken by astronauts on the Moon (e.g., resolution of issues surrounding the terminal phase of accretion of material left over from the formation of the solar system) might bring into focus new scientific questions to be addressed by robotic activities conducted on Mars long before humans first set foot on the Red Planet. Finally, it is conceivable that attention to human exploration will create an imperative for additional studies of terrestrial analogs of lunar or martian environments. Thus, the likely impact of a human exploration program on solar system exploration priorities will be complex and multifaceted. In the short term there is a need to conduct a crosscutting study to define the necessary enabling activities for, and to scope the likely impacts of, the human exploration program on the scientific priorities for the robotic exploration of the Moon, Mars, and Earth, and possibly even Venus. Although efforts will have to be made to seek out new areas of research that are specifically enabled by human space exploration, or that can facilitate its success, these two categories of science will need to be treated differently. Science that is enabled by human exploration is properly competed directly with “decadal-survey” science and evaluated and prioritized according to the same rigorous criteria. Science to enable human exploration must compete on the basis of the criticality of the problem it addresses (not necessarily a science issue) and the likelihood that it will resolve the problem. Put another way, for the former kind of science, greater understanding is an end in itself, and science that seeks to contribute to such understanding must compete in this metric with decadal-survey science. For the latter science, understanding is a means to the end of resolving a particular problem, and the degree of understanding needed depends on the problem. For example, in the life sciences area, past NRC studies have recognized the need to precisely define the specific risks faced by astronauts exposed to radiation hazards and microgravity. Additional fundamental research on basic cellular and physiological mechanisms is required; the knowledge needed will not be gained in a focused engineering and development program alone. Development of clinical countermeasures to protect human explorers is currently constrained by the lack of access to critical astronaut data, as well as a paucity of data due to the small numbers of humans who have flown for extended periods in space. All of these problems will require much greater focus in the future if long-duration human spaceflight is to become a reality. Another essential consideration is that science to enable human exploration is inherently crosscutting, involving insights from many fields of science and technology. All of the decadal surveys and other studies cited above were, by design, discipline-based. That is, they provide scientific strategies for a particular field or set of related disciplines. This approach to setting scientific goals for breakthroughs in individual fields is effective, and the current reports remain timely and relevant today in their respective areas. However, NASA’s new vision for exploration opens up novel and previously 7 Solar and Space Physics and Its Role in Space Exploration (NRC, 2004).
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Science in NASA’s Vision for Space Exploration unexplored issues whose nature can best be illustrated by the question, How, and by whom, is the decision to be made that we have acquired the necessary relevant medical, scientific, and technological knowledge needed before we actually send humans to Mars? No single decadal survey or combination of surveys provides the type of advice needed for the new programs that are anticipated under the new vision for exploration. Also, no single scientific or engineering discipline can provide the expertise and knowledge necessary to optimally solve these problems. Therefore, a reexamination of the decadal surveys would not provide ideal guidance for enabling science. Instead, crosscutting advice needs to come from cross-disciplinary groups of experts representing diverse scientific fields rather than from the traditional single-discipline survey committees. Such crosscutting studies will identify fundamental, problem-oriented research in a number of key areas of enabling science. For example, understanding and mitigating the deleterious effects of space radiation on both astronauts and operational systems is a complex, multifaceted problem. Progress in countering the harmful effects of different space radiation environments will have to draw on advances in solar and space physics, radiation monitoring, risk assessment, materials science, biomedical science, medical systems engineering, space systems design, and more; it also may be facilitated by the use of robotic “guinea pigs” rather than human subjects. A piecemeal approach to planning research and setting priorities under the guidance of individual scientific disciplines is unlikely to produce robust, reliable solutions. Other examples of crosscutting problems for which interdisciplinary planning will be appropriate are the assessment of measures needed to counter the physiological effects of partial gravity on humans in spaceflight, techniques for life detection on planetary bodies, approaches to prevent and/or control the cross-contamination of Mars by human missions, and the design of self-sustained habitats. This list is not meant to be definitive or all-inclusive, but rather to illustrate the point. Importantly, these interdisciplinary challenges, by definition, encompass more than one of NASA’s new 13 roadmap areas (see Chapter 2), and so NASA will have to take special care to foster and advance these efforts. Finally, all enabling science, regardless of whether the topics fall within a particular disciplinary area or are broadly crosscutting, should be evaluated and planned with the same scientific rigor, openness, and thoughtful prioritization that have characterized the decadal surveys, and should be executed according to a process that provides for incremental successes to sustain momentum, use resources efficiently, enforce priorities, and enable future breakthroughs. In many cases, paralleling the decadal-survey approach in which the users of information participate in setting priorities for obtaining it, it would be appropriate to have representatives of organizations that put forward operational requirements and/or will have to deliver operational systems participate in the evaluation of enabling science. Therefore the committee recommends that NASA identify scientific and technical areas critical to enabling the human exploration program and that it move quickly to give those areas careful attention in a process that emphasizes crosscutting reviews to reflect their interdisciplinary scope, generates rigorous priority setting like that achieved in the decadal science surveys, and utilizes input from a broad range of expertise in the scientific and technical community.
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Representative terms from entire chapter: