Research for a Future in Space: The Role of Life and Physical Sciences [1 ed.] 9780309261043, 9780309261036

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Research for a Future in Space

Copyright © 2012. National Academies Press. All rights reserved.

The Role of Life and Physical Sciences

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

This booklet is based on the Space Studies Board (SSB) report Recapturing a Future for Space Exploration: Life and Physical Sciences Research for a New Era, available for free online at www.nap.edu. Details about obtaining copies of the full report, as well as information on SSB and the Division on Engineering and Physical Sciences activities, can be found online at www. nationalacademies.org/ssb and www.nationalacademies.org/deps, respectively.

Recapturing a Future for Space Exploration was authored by the Committee for the Decadal Survey on Biological and Physical Sciences in Space:

Copyright © 2012. National Academies Press. All rights reserved.

ELIZABETH R. CANTWELL, Lawrence Livermore National Laboratory, Co-chair WENDY M. KOHRT, University of Colorado, Denver, Co-chair LARS BERGLUND, University of California, Davis NICHOLAS P. BIGELOW, University of Rochester LEONARD H. CAVENY, Independent Consultant, Fort Washington, Maryland VIJAY K. DHIR, University of California, Los Angeles JOEL E. DIMSDALE, University of California, San Diego, School of Medicine NIKOLAOS A. GATSONIS, Worcester Polytechnic Institute SIMON GILROY, University of Wisconsin-Madison BENJAMIN D. LEVINE, University of Texas Southwestern Medical Center at Dallas RODOLFO R. LLINAS, New York University Medical Center KATHRYN V. LOGAN, Virginia Polytechnic Institute and State University PHILIPPA MARRACK, National Jewish Health GABOR A. SOMORJAI, University of California, Berkeley CHARLES M. TIPTON, University of Arizona JOSE L. TORERO, University of Edinburgh, Scotland ROBERT WEGENG, Pacific Northwest National Laboratory GAYLE E. WOLOSCHAK, Northwestern University Feinberg School of Medicine The SSB is a unit of the National Research Council of the National Academies, which serve as independent advisers to the nation on science, engineering, and medicine. Support for this publication was provided by the National Academy of Sciences and the National Aeronautics and Space Administration. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the agency that provided support for the project. The SSB acknowledges Chase Estrin, Sandra Graham, Katie Kline, and Duke Reiber for contributing to the text of this booklet. Booklet design by Katie Kline. Cover image and title page image (right) of the NASA Desert RATS program are courtesy of NASA. Copyright 2012 by the National Academy of Sciences.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Research for a Future in Space

Copyright © 2012. National Academies Press. All rights reserved.

The Role of Life and Physical Sciences

based on the National Research Council report

Recapturing a Future for Space Exploration Life and Physical Sciences Research for a New Era

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

About the Report

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In May 2009, the NRC Committee for the Decadal Survey on Biological and Physical Sciences in Space began a series of meetings initiated as a result of the following language in the explanatory statement accompanying the FY 2008 Omnibus Appropriations Act (P.L. 110-161):

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Recapturing a Future for Space Exploration

Copyright © 2012. National Academies Press. All rights reserved.

Life and Physical Sciences Research for a New Era

Achieving the goals of the Exploration Initiative will require a greater understanding of life and physical sciences phenomena in microgravity as well as in the partial gravity environments of the Moon and Mars. Therefore, the Administrator is directed to enter into an arrangement with the National Research Council to conduct a “decadal survey” of life and physical sciences research in microgravity and partial gravity to establish priorities for research for the 2010-2020 decade.

In response to this language, a statement of task for an NRC study was developed in consultation with members of the life and physical sciences communities, NASA, and congressional staff. The guiding principle of the study was to set an agenda for research in the next decade that would use the unique characteristics of the space environment to address complex problems in the life and physical sciences, so as to deliver both new knowledge and practical benefits for humankind as it embarks on a new era of space exploration.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Copyright © 2012. National Academies Press. All rights reserved.

Contents Research for a Future in Space

4-5

The Issues of Bone Loss & Nutritional Needs in Space Preventing Bone Loss · Nutrition and Space Foods

6-7

Shifts in Astronaut Health During Long Periods in Space Chronic Sleep Loss in Space · Shifts in Cardiovascular Health

8-9

Coping with Confined Space Environments Monitoring Brain and Behavioral Functions in Astronauts · Group Dynamics in an Extreme Environment

10-11

The Roles of Plant & Microbial Growth Up-Rooted: Plant Growth in Space · Managing Microbes as Spaceflight Companions

12-13

The Risk of Cellular & Genetic Changes in Long-Term Space Travel Muscle Weakness and Protein Degradation · Radiation During Spaceflight

14-15

The Nature of Fluid Physics in Space Recycling Air and Water in Spacecraft · Addressing Other Aspects of Fluid Physics in Space

16-17

Issues in Fire Behavior & Safety: Prevention, Detection, Suppression Combustion and Fire Behavior in Reduced Gravity · Fire Safety and Prevention in Space

18-19

The Matter of Materials & the Relativity of Time Weighing the Matter of Materials · Exploring Space and Time

20-21

Essential Technologies for Space Suits Engineering a Personal, Portable Atmosphere · Exploration Enabled by Space Suit Technology

22-23

Living Off the Land: Using In-Situ Materials Harnessing Non-Terrestrial Resources for Exploration Technologies · Space Construction with Earth-Tested Methods

24-25

Report Recommendations

26-28

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Research for a Along the way to becoming a space-faring species, humanity has faced enormous challenges. Despite these many initial hurdles, however, the United States has contributed to the progress of human spaceflight by delivering the lunar landings, the space shuttle, and, in partnership with other nations, the International Space Station (ISS). NASA’s rich and successful history has been enabled by, and responsible for, a strong backbone of scientific and engineering research accomplishments. These milestones and future developments are made possible through ongoing advances in life and physical sciences research.

Copyright © 2012. National Academies Press. All rights reserved.

Looking to the future, significant improvements are needed in spacecraft, life support systems, and space technologies to enhance and enable the human and robotic missions that NASA will conduct under the U.S. space exploration policy. The missions beyond low Earth orbit, to and back from planetary bodies, and beyond will involve a combination of environmental risk factors such as reduced gravity levels and increased exposure to radiation. Human explorers will require advanced life support systems and will be subjected to extended-duration confinement in close quarters. For longer missions conducted farther from Earth, for which resupply will not be an option, technologies that are self-sustaining and/or adaptive will be necessary. To prepare the U.S. for its future as an enduring and relevant presence in space, both basic and applied research in the life and physical sciences within NASA will need to be reinvigorated. Specifically, NASA’s compelling future in space exploration will flow in large part from the implementation of a strong life and physical sciences program. The NRC decadal survey Recapturing a Future for Space Exploration: Life and Physical Sciences Research for a New Era identifies these research opportunities and imperatives that can be achieved most rapidly and efficiently by establishing a multidisciplinary and integrated research program within NASA itself. Such a program is needed to span the gaps in knowledge that represent the most significant barriers to extended human spaceflight exploration. A successful program will depend in part on the results of research that can only be performed in the unique environment of space; in other words, the program should draw on research that is enabled by access to space. This type of fundamental research addresses questions that exist at the very core of discovery: What factors contribute to flame growth and impact fire behavior in reduced-gravity conditions?

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Future in Space What underlying biological mechanisms are revealed when the fundamental force of gravity is stripped away? From these questions, new technologies can emerge in seemingly unrelated sectors. For instance, discoveries might emerge in the field of medicine from access to data on physiological changes, such as heart muscle atrophy and decreasing bone mass, in astronauts during spaceflight. But discovery is just one component of a comprehensive research program. To generate progress in all relevant areas needed for human spaceflight, a program should also yield new insights into the space environment that can be applied to exploration mission needs. This enabling research could contribute to innovative technologies that are more reliable, cheaper, safer, and more efficient, making human spaceflight more accessible than was possible in these last few decades. More specifically, how could a better understanding of the space environment enable engineers to design technologies that harness the unique conditions of space instead of competing with them? For example, are there techniques or materials yet to be developed that could use reduced gravity to enhance, rather than complicate, the transfer of fuels during spaceflight?

Copyright © 2012. National Academies Press. All rights reserved.

Overcoming these specific challenges, as well as the more general scientific and engineering obstacles that are present in space exploration, will require an understanding of biological and physical processes, as well as their intersections, in the presence of a range of reduced gravity conditions. The examples presented in the following pages illustrate only some of the mechanisms, uncertainties, and unique phenomena that are a part of the space environment. These are select areas that could benefit from fundamental research in the life and physical sciences, but they also provide a glimpse into the possible applications for this research both in space and for society as a whole. These brief vignettes raise questions—such as, what discoveries still await humanity in the space environment that would not be possible to make on Earth, and what barriers to human spaceflight still remain? These examples of enabling research, and descriptions of scientific insights enabled by access to space, are explored in greater detail in the full NRC report Recapturing a Future for Space Exploration. This publication and the full report are available online at http://www.nap.edu.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Over millions of years, the structures of organisms on Earth have evolved under the constant influence of the planet’s gravity. When living in microgravity, however, organisms attempt to adapt to a new hierarchy of forces. For humans, understanding how bones can change in space, particularly when that change relates to bone loss, is crucial to allowing longer missions. Much as on Earth, a nutritionally adequate diet in space must be maintained for proper body function. How many calories are needed while in space? What types of physical activity or exercise can promote bone and muscle growth? Such questions can be answered only through a better understanding of the effects of reduced gravity on the many and complex systems of the human body.

Preventing Bone Loss

© 2011 by Lindsay Davidson, under a Creative Commons Attribution-NonCommercial-ShareAlike license.

The Issues of Bone Loss &

The skeletal system of animals provides a solid framework for structural support, protection, and mobility in Earth’s gravity (1 g). It is not surprising, then, that the skeletal system changes in the absence of gravity. Reports show that the rate of bone loss in microgravity can be roughly 10 times greater than the rate of bone loss that occurs in women after menopause. Bone mineral density (BMD) is the measurement used to determine how much bone loss has occurred.

Copyright © 2012. National Academies Press. All rights reserved.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Backg round ed ited from “Osteoporotic Bone” © 2008 by A lan Boyde, Bone Research Societ y, UK.

Over the past 15 years, drugs like biophosphonate have been developed for the prevention of osteoporosis, and the ISS provides a unique platform for testing their effectiveness. Research has shown that biophosphonate injections maintained a slightly increased BMD in the spine and hips of rodents during 90 days of hindlimb unloading, which is also used as an analog of microgravity. One concern is that suppression of resorption—the breakdown and release of bone minerals to the blood stream—will also suppress bone formation. With such drugs, consequently, further research is needed to ensure that bone fractures will be able to heal as expected.

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After being in space for six months, astronauts typically need more than two and a half years for their BMD to return to pre-flight levels, while the changes in bone structure that also occur in microgravity can be irreversible and actually mimic many of the changes associated with advanced aging. Such issues are currently a barrier to long periods in space, so it is important for future research to focus on such issues as whether a partial-gravity environment—for example, one-third gravity for Mars or one-sixth gravity for the Moon— will provide some degree of protection from the bone loss that occurs in microgravity. The U.S. and Russia have used exercise in space as a loading mechanism to counter the effects of microgravity, but these activities have not been reliably effective for maintaining bone mass and there is evidence that previous exercise loading on devices failed to adequately maintain BMD. However, ground-based research that uses long-term bed rest to mimic the effects of sustained lowered gravity have suggested that bone may be somewhat protected by certain activities, including exercise time. Supine treadmill exercise—that is, running while suspended horizontally—has shown positive benefits when coupled with imposing negative pressure to the lower-body during both 30- and 60-day periods of bed rest.

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Nutritional Needs in Space

© 2011 by Lindsay Davidson, under a Creative Commons Attribution-NonCommercial-ShareAlike license.

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Osteoporosis is a bone disease marked by the steady decrease of BMD, contributing to an increased risk for fracturing. Women are particularly at risk due to the hormonal fluctuations experienced during and after menopause. Research enabled by access to space could provide insights on bone loss prevention in astronauts and, back on Earth, contribute to advances in the prevention, diagnosis, and treatment of osteoporosis.

Nutrition and Space Foods Nutrition is another method by which scientists have tried to mitigate astronaut bone loss. While it is well known that inadequate nutrition disrupts proper functioning of the human body, the extent of these effects in microgravity is not well understood. Long periods in space may make astronauts particularly susceptible to bone and muscle loss, compromised immune systems, and neurological changes that can affect cognitive functioning and contribute to sleep deprivation conditions likely exacerbated by suboptimal nutrition.

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Based on information from previous missions, some common vitamin and mineral deficiencies have been identified in astronauts. In particular, several deficiencies or insufficiencies are consistently reported, including inadequate energy intake and a depressed vitamin D and K status. Data from individual Skylab missions show that length of mission is a factor in vitamin D status; the longer the mission, the more depressed the vitamin D status. Because astronauts are not exposed to UV light in flight, they require a vitamin D supplement. This nutrient, which is the only vitamin routinely supplemented in spaceflight, is required for calcium absorption—an important consideration when bone loss is a clearly documented negative consequence of spaceflight. In order to predict and mitigate any deficits experienced by astronauts, short- or long-term, it is critical to study any changes to the antioxidant capacity of space foods as a function of processing and space conditions. NASA has therefore instituted effective measures to ensure that all food consumption and specific nutritional needs are met. NASA’s Johnson Space Center has developed a wide selection of foods for use in space that have been analyzed and well documented for their nutritional content. On Earth, preparing and storing foods for long periods can lead to loss or depletion of the foods’ nutritional value; however, there is still insufficient information on the ways in which these same processes affect foods in space, including the effects of space radiation.

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Backg round ed ited from “Osteoporotic Bone” © 2008 by A lan Boyde, Bone Research Societ y, UK.

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Physiological interactions with microgravity conditions are largely unpredictable, including our understanding of the effects on vitamin levels. Dietary supplements and nutritionally evaluated space foods are approaches to combating deficiencies and ensuring the health of astronauts.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Chronic Sleep Loss in Space

Scientific evidence is mounting that the effects of chronic sleep loss are not limited to impaired brain function (such as, alertness, psychomotor performance, situational awareness, and problem solving). For example, it is now thought that chronic sleep loss exacerbates unhealthy weight gain by altering leptin and ghrelin levels, which are hormones that mediate hunger and metabolism. Also of particular interest is the possibility that chronic sleep loss in space could lower psychological resilience and increase the incidence of stressor-induced symptoms and illness.

Shifts in Cardiovascular Health Developed over millions of years in the constant presence of gravity, the cardiovascular system is used to dealing with rapid shifts in gravitational gradients: lying down, standing up, and exercising all change the influence of gravity on the blood and circulation. One such response is the shift in blood volume from the lower extremities to the head and neck because, in space, the circulatory system is no longer “fighting against” Earth’s gravity. More precisely, fluids shift away from the lower extremities and migrate toward the head, causing the astronaut’s appearance of thin “bird legs” and a puffy face. The heart initially becomes quite full, and the blood vessels of the head and neck become distended. Within the first few days, the body attempts to get rid of this fluid and there is a decrease in total blood volume in the astronaut. In-flight plasma volume can decrease by 10%-17%, and the circulation seems to adjust to a level about half-way between lying down and standing up.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Backg round i mage “Gy r us Dentat us” © 2005 by Methox yRox y, under a Creative Com mons Attr ibution-ShareA l i ke l icense.

Copyright © 2012. National Academies Press. All rights reserved.

Historically, NASA has recognized the importance of sleep and circadian rhythms for sustaining cognitive functioning in space and, accordingly, has supported related research efforts. Such studies have generally revealed that sleep is disrupted during space missions, with reductions in time spent asleep and disturbances of the circadian sleep/wake rhythm. These detrimental effects typically become more severe after 90 days in orbit, leading to greater fatigue. Although it is difficult to specify the extent to which sleep loss and fatigue have contributed to actual errors or accidents during space missions, these issues have been recognized as factors that likely contributed to specific incidents, such as the Mir– Progress collision on June 25, 1997.

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Adequate sleep—obtained on a regular schedule reflecting the brain’s natural (circadian) sleep/wake rhythm—is necessary for maintaining optimal health, alertness, and performance. Cardiovascular functioning depends on the delivery of blood to all organs at optimal perfusion pressure. In space, however, factors that determine various physiological rhythms and efficiencies, such as gravity and exposure to the Earth’s light/dark cycle, are altered or absent. A thorough understanding of the interactions between human physiology and long-term exposure to non-terrestrial conditions will be critical to the success of extended missions in space.

© 2006 by Dr. S. Gi rod, A nton Becker, under a Creative Com mons Attr ibution-Share A l i ke l icense.

Shifts in Astronaut Health

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With little gravity resistance for the heart to pump against, significant atrophy can occur just as it would with other muscles. For example, one study of four astronauts found a 7%-10% atrophy in cardiac muscle following just 10 days in space. Actual microgravity conditions cannot be simulated for extended periods of time on Earth, but bed rest studies can provide some insights into the effects of a long period of “reduced resistance” on the heart.

Bed rest studies have consistently shown a reduction of about 1% per week in bed, though this loss of heart muscle seems to be reduced, or in some cases eliminated, by exercise while in bed or in space. Cardiac rhythm irregularities have been recorded during long-duration spaceflights in particular, which have raised the question of a clinically serious problem. Rigorous quantification of the frequency and variability of irregular heartbeats both before and during flight—along with non-invasive assessments of cardiac electrophysiological properties—will be necessary to determine the magnitude and significance of these observations. Astronauts could also carry heart problems with them into space. During a prolonged mission to Mars, astronauts would not have access to comprehensive healthcare services for two to three years at a time, aside from assigned crew expertise. Although astronauts are now carefully screened prior to selection, they often must wait a decade or longer to fly select missions. The resulting age range—the average age of astronauts is 46— puts them at greater risk for developing life-threatening cardiac issues. NASA invests considerable resources in training astronauts, so the NRC has recommended that screening and monitoring strategies be implemented to follow astronauts from selection to flight as a method of identifying individuals whose short term (two- to three-year) risk for a cardiovascular event may have increased. It will also be important to develop pharmacological or physiological risk mitigation strategies that will effectively and sufficiently reduce the risk of cardiovascular events prior to and during spaceflight.

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Backg round i mage “Gy r us Dentat us” © 2005 by Methox yRox y, under a Creative Com mons Attr ibution-ShareA l i ke l icense.

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© 2006 by Dr. S. Gi rod, A nton Becker, under a Creative Com mons Attr ibution-Share A l i ke l icense.

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During Long Periods in Space

Astronauts in space experience a variety of sleep difficulties that can be assessed by tracking their brain waves during each phase of sleep. Electroencephalograph machines monitor and measure electrical impulses from the brain, muscles, eyes, and heart; during spaceflight, a cap of electrodes is secured to the astronaut’s head to record electrical activity as brain waves.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

One of the many challenges faced by astronauts in space is confinement in close quarters with their crew, coupled with limited contact with friends and family. This type of confinement is not unique to space, but research exploring the group dynamics experienced by current astronauts could benefit our understanding of fundamental behavioral and cognitive processes. Future studies could help to guide practices regarding the optimum number of crew members needed to foster healthy group dynamics during long-duration missions. Using ISS experience, data on behavioral and neurological changes resulting from stress factors—such as exposure to radiation or a lack of privacy/personal space—could also contribute to research on physiological and cognitive responses to traumatic events on longer missions. In addition to possible implications on Earth, these inquiries could guide healthy group dynamics and individual well-being in space. Image Cred it: NASA

Monitoring Brain and Behavioral Functions in Astronauts

Copyright © 2012. National Academies Press. All rights reserved.

During astronaut selection, candidates submit to a series of tests that go beyond the bounds of physical performance measures. In general, these include self-report personality inventories and formal psychiatric interviews. In addition, NASA’s cognitive performance tests are only administered for the purpose of informing the astronaut selection process and then providing meaningful data for detecting trends in the astronauts’ status during actual missions. This process includes a projection of their capacity to perform missionrelated tasks as well as their temporary sense of well-being. Astronauts selected and trained for spaceflight produce a baseline of health data against which testing performed in space can later be compared. Certain environmental conditions could have an impact on cognitive processes that are critical to coping with issues in a spacecraft. For example, a decline in executive functioning, perhaps as a result of sleep loss, could impair an astronaut’s reaction time, memory retrieval, problem-solving abilities, general alertness, and judgment. Measures of cognitive resilience should be identified or developed to assess astronauts’ capacity for sustaining performance in the face of significant stressors, particularly in the context of challenging situations such as docking.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Backg round Image “Star Tra i ls i n Space” Cred it: NASA (ISS).

Long-duration space missions require a crew to perform at peak health in every respect, overcoming obstacles that may arise from living in a confined, isolated environment. Even small errors in judgment or coordination can have profoundly adverse consequences in the unforgiving environment of space. While research on Earth continues to expand the use of functional magnetic resonance imaging (fMRI) procedures for mapping the physiological basis for behavioral and cognitive functioning, currently the only way to determine cognitive performance capacity for astronauts is to administer cognitive tests.

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Coping with Confined

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Space Environments

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Group Dynamics in an Extreme Environment Analog studies that involve simulating some of the most salient aspects of the space environment, and surveys of astronaut personnel, have contributed to our understanding of factors that affect social compatibility. Some of these include goal orientation, kindness, and a lack of hostility. Crews of future long-duration missions will likely include a diverse mix of national, organizational, and professional cultures, all of which produce characteristics that have been found to affect group functioning in space. Leadership is always an important predictor of team functioning and may be especially important during space missions. Additional research is required to determine how leadership styles across different nationalities will affect crew tension. Similarly, evidencebased methods for preventing a breakdown in communication, or the identification of methods for promoting group cohesion, will be important. Rigorously designed experimental simulations—mirroring actual mission parameters like isolation, confinement, and workload—are needed to provide further insights into group dynamics and cooperation.

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Backg round Image “Star Tra i ls i n Space” Cred it: NASA (ISS).

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Image Cred it: NASA

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On Apollo 13, the carbon dioxide removal system malfunctioned and, with the help of ground crew specialists, the crew was able to devise a replacement unit that brought the system back online. This worked to save the astronauts and also strengthen the community supporting the mission. In addition to everyday stressors, the extreme conditions of the space environment can pose life-threatening risks. Astronauts should be able to rely on both their own unimpaired judgments and the support of the crew when resolving these issues.

Astronauts face continuing stress throughout their mission, such as in the period between the end of training and when selected for a mission, and their cognitive performance may fluctuate. It is important to identify individual characteristics that facilitate coping with the space environment and that contribute to healthy group dynamics during extended missions. Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Image Cred it: NASA

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Up-Rooted: Plant Growth in Space

Space environments, however, present factors other than microgravity that could potentially alter these specialized functions. Components of the spaceflight environment are complex and dynamic; they range from intrinsic and natural (radiation and gravity) to highly engineered factors developed for and in the spacecraft habitat itself (atmospheric composition, pressure, variations in light spectrum, noise, and vibrations). Pressure is one consideration in the spaceflight environment. While Earth’s atmosphere is approximately 100 kPa (14.5 pounds per square inch), the lower limit of pressure used to maintain human comfort during routine activities is about 34 kPa (5 psi). Plants, on the other hand, can tolerate much lower pressures—well below 25 kPa (3.6 psi), depending on the plant and its stage of growth. This suggests that plants could potentially be grown in low pressure habitats, and even in plant habitats with filtered and compressed CO2 (the principal component of the martian atmosphere), thereby reducing the high demand of consumable resources needed to maintain human-accommodating atmosphere and pressure in spacecraft or plant farming facilities on Mars. Research is needed to confirm minimums that can be sustained for long periods or perhaps perpetually while in space or on other planets. Controlled crop cultivation in this capacity could provide insights into optimizing plant growth conditions and responses, potentially benefiting human life and health on Earth as well. For example, research into plant responses to gravity could contribute to innovations in crop recovery after lodging—damage done when weather has bent a crop down flat to the ground.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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H ce pa fl su on Backg round Image “Roots” © 2008 by sebarex v ia Stock.XCHNG.

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As plants have evolved in a constant 1 g environment, they have adapted to detect gravity and respond accordingly by adjusting directional—or gravitropic—growth. This allows the plant to maintain the correct orientation of its organs and, in turn, helps to define the structure of the root and shoot systems. This mechanism, along with other physiological functions, is driven by forces and processes that are constant on Earth.

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Image Cred it: NASA

It has taken eons for Earth to develop its current physical state, and its biosphere’s characteristics are intrinsically connected with terrestrial life. These factors are tied with other processes that are critical for supporting all terrestrial organisms. For example, on Earth, the phenomenon called gravity-driven buoyancy causes the settling and separation of fluids of different densities and is responsible for natural convection: the movement of molecules en masse within liquids and gases. This phenomenon is involved in such diverse processes as the formation and movement of ocean waves and molecular signaling in bacteria. The pervasive force of gravity has had profound and myriad effects on the evolution and development of terrestrial organisms, but what happens when these organisms are removed from the gravitational environment in which they evolved? Since plants can sense changes in gravity, do they grow differently during spaceflight? Can microbes survive and thrive far from Earth? In addition to addressing topics that are fundamental to all biological processes, research on these questions will be central to having plants and microbes as useful partners to support humans on long-term space missions as part of a biologically-based, regenerative life support system.

© 2005 CDC/Rod ney M. Don lan, Ph.D.; Jan ice Car r (PHIL #7488)

The Roles of Plant &

A biofilm is a collection of cells adhered together on a living or inert surface; this often involves the secretion of a protective substance, making the pathogen very difficult to eradicate.

Managing Microbes as Spaceflight Companions Microbes are a unique component of the spaceflight environment. Attempts to broadly eradicate bacteria in spacecraft would not only be extremely difficult, they would also eliminate microbiota essential for human health. There are more bacterial cells in and on the human body than there are human cells. As a result, it would be all but impossible to prevent crew members from continually reintroducing microbes into their spacecraft or habitat. The human microbiome is beneficial for important physiological functions, such as food digestion by humans. When antibiotics alter bacteria in the gut, these helpful microbial communities need to repopulate the intestine in order to restore and sustain its function. In the isolated spacecraft environment, it is unclear how this repopulation would occur if the environment was continually subjected to antibiotic decontamination.

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Backg round Image “Roots” © 2008 by sebarex v ia Stock.XCHNG.

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However, some amount of microbial decontamination is necessary since the presence of certain microbes in a closed environment can pose a threat to human health. Bacterial pathogens can be particularly dangerous, especially for astronauts on long-duration flights in which evacuation may not be an option. Research has indicated that bacteria such as E. coli can form protective biofilms in microgravity conditions just as they do on Earth. Research on the effects of the spaceflight environment on microbes is limited. The gap in knowledge is partly due to a lack of isolation technology, such as alternative platforms called free-flyers, that could isolate pathogens from ISS astronauts while allowing research on bacterial virulence to be conducted safely in space. Discoveries in this area could potentially contribute to innovations in how best to focus preventative measures on particularly resilient bacterial pathogens known on Earth.

Image Cred it: NASA

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Microbial Growth

© 2005 CDC/Rod ney M. Don lan, Ph.D.; Jan ice Car r (PHIL #7488)

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Space travel will likely require strategies for self-sufficiency as the duration and distance of missions increase. In those instances, disposing of waste would no longer remain cost-effective, and resupplying crew members with oxygen, water, and food from Earth would no longer be feasible. One of the main requirements for sustaining life in space, such as on the lunar surface or on Mars, and as a strategy for long-duration flights, is the development of bioregenerative life support systems. A selfsustaining system could utilize plants and microbes to recycle waste and supply food, oxygen, and water to crew members.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Image Cred it: NASA

The Risk of Cellular & Genetic

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In the past decade, major technological advances in genome sequencing, and developments in research on gene-environment interplay, have expanded our understanding of multigenerational and environmental influences of gene expression. Previous studies on the effects of spaceflight on muscle mass, strength, and contraction have focused more directly on protein changes. For example, studies on rodent muscle immediately following spaceflight have shown degradation in myosin heavy chain and actin proteins, which are the principal proteins involved in muscle contraction. Muscle genes affecting these proteins are rapidly downregulated within 24 hours of simulated microgravity exposure, thereby impacting muscle remodeling and function. Ground-based research on animal models, such as rats and mice, has played a major role in generating fundamental knowledge about the effects of microgravity on muscle alterations and in developing countermeasures to microgravity-induced alterations in features such as muscle mass and function. In turn, the ISS is a critical platform for conducting longduration studies on the effects of countermeasures. For example, an ISS exercise facility could simultaneously test equipment designed for spaceflight exercise while monitoring the functioning of multiple organ systems on a metabolic level. This also has the potential to aid in our understanding of the processes behind muscle wasting on Earth.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Muscle Weakness and Protein Degradation

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While the safe return of a crew from space historically marks the end of a successful mission, the process of evaluating astronaut health continues in the form of determining what physiological changes might have arisen in space. The levels of radiation in space are high enough, and the missions long enough, to require shielding to minimize carcinogenic, cataractogenic (cataract-causing), and possibly neurological effects on crew members. Microgravity conditions also can affect astronauts via changes in the metabolic pathways and patterns of protein expression that regulate muscle strength. Therefore, the long-term health of astronauts depends on research exploring such questions as, what amount of radiation is safe and for how long? How does a relatively short stay in a microgravity environment alter basic processes and functioning, like muscle contraction?

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Because the radiation types and effects are distinct from those found following exposure to more conventional radiation sources, it has been necessary to train biologists in the physics, and other unique properties, of space radiation and to develop novel approaches to address problems that might be associated with radiation exposure in space. NASA has worked to develop a cadre of scientists and facilities that can be used to study the effects on biological systems of these unique radiation types. The focus of NASA’s radiation biology program during the coming decade will be the development of a better understanding of radiation risks associated with spaceflight, such as the biological consequences of protons and high LET radiation.

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There is a huge body of existing literature on the effects of low LET radiation on biological samples, including long-term animal studies and clinical studies. However, information on the biological consequences of the radiation encountered in space—for example, high energy protons and high LET radiations, such as heavy charged ions—is much less detailed. About 90% of the particles in galactic cosmic rays, for instance, are composed of high energy protons while the remaining 10% are helium, carbon, oxygen, magnesium, silicon, or iron ions. While protons are used in some forms of radiotherapy, their use is relatively new and biological consequences of exposure are not clearly understood. Heavy ions have features that are very different from the conventional radiotherapy qualities of radiation and may have unique biological effects on the host.

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Exposure to radiation in space predominantly involves two types of radiation: low linear energy transfer (LET) and high LET radiation. Solar particle events involve exposures to energetic protons, which are similar in their radiobiological effects to the low LET radiation in conventional medical x-rays or gamma rays used in radiation therapy.

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DNA is found in forms of life from bacteria to humans. Exposure to radiation can damage DNA and cause major health problems, including cancer. This is a clear example of why radiation research is important for long-duration space missions.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

The Nature of Fluid

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Spacecraft operate in highly isolated environments and as missions range further from low Earth orbit, the resupply of their consumables, like water and air, becomes virtually impossible. Any missteps in handling life-dependent consumables—often breathable constituents of air or liquids like water—could have serious consequences for a human crew in flight to, or even on, Mars. The space environment, however, represents a unique factor influencing the storage and processing of such vital resources: Microgravity affects these consumables in unexpected ways that make them all the more challenging to sustain and process. In the case of water and air in a closed environment, every means possible to reliably stretch and sustain them as recyclable resources needs to be taken— progress should be made to study, understand, and exploit them relative to the absence or significant reduction of Earth gravity.

Recycling Air and Water in Spacecraft

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During spaceflight, a closed-loop system could remove carbon dioxide, water vapor, and contaminates from the air, including any other airborne foreign particulates that could be harmful to the crew. This technology, which would supply clean air and water to astronauts and collect waste products, could be provided to groups in extreme and dangerous terrestrial environments as well, such as miners. Past research has shown that 50 m2 of plants per person will provide the necessary nutrients and calories to sustain life with air revitalization occurring by default. In order to supplement the energy required for continuous plant growth, research suggests solar panels to generate power for LEDs. Research will be needed to assure that the emerging lighting technologies will be able to provide adequate radiant energy to promote productive plant growth.

Addressing Other Aspects of Fluid Physics in Space Much as on Earth, lunar or martian surface materials interact with and often foul tools, preventing their proper functioning. Understanding the altered granular physics of these en masse, fluid-like behaviors is critical for enabling both human and/or robotic explorations on those surfaces. Fortunately, successful missions on the Moon and on Mars have indeed characterized the surface materials, such that they can be well-modeled for research.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Increasing stay times on the moon and Mars, as well as in-situ independence inside the spacecraft, depend on efficient managing of fluids. If no in-situ resource mining or recycling technology is employed, the spacecraft mass and launch energy requirements grow substantially to accommodate the transport of the consumables manifest to provide life support for the crew for the total time of their round trip to Mars. For these reasons, the mission and crew would benefit significantly from the use of a system for recycling both air and water on long-duration spaceflights. It is also proposed that any such mission would also endeavor to produce a significant proportion of its own food supply, during both legs of the spaceflight and during the stay time on Mars—that is, if the crew was there long enough to make food production on the surface a viable component of the mission.

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For example, both environments are known to have very dusty surfaces with extensive depths of very fine particles that can seep into mechanical components and cause operational failures. When using powered vehicles to get around on surface topography, this kind of failure could strand astronauts performing extra vehicular activities (EVA) at dangerous distances from their primary lander habitats. These issues are complicated in a reduced gravity environment where electrostatic forces and even wind can easily propagate clouds of fine particulate material that then settles very slowly as a coating on any nearby surfaces.

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One revolutionary and mission architecture-changing system involves on-orbit depots for cryogenic rocket fuels. The scientific foundations required to make this Apollo-era notion a reality center around understanding flows in cryogenic systems. For example, for some lunar missions, such a depot could produce the major cost savings by dramatically reducing the necessary size of the launch system. The highly publicized potential collection or production of large amounts of water from the Moon or Mars will require scientific understanding of how to retrieve and refine water-bearing materials from the extremely cold, rugged regions on those bodies. Once produced, that water could be transported to surface bases or to orbiting facilities for conversion into liquid oxygen and hydrogen by innovative solar-powered cryogenic processing systems and then be stored in the on-orbit depots. All of these hardware and systems implementations require or will be enhanced by new scientific understanding. Such advances point the way to a new era in defining space exploration. With a growing body of data suggesting that water is almost universally prevalent in the solar system, with significant resources having been identified on the moon, Mars, and other smaller bodies, it becomes increasingly possible to produce smaller supplies of hydrogen for lesser applications from the water resources space explorers will be able to mine and process as an in‑situ resource.

In physics, fluid refers to any substance that continually responds to a shear stress; in addition to liquids, particles like dust and gasses can flow as well, as do particulate materials such as sand and dust. Martian soil fines are also significantly magnetic, as the Viking landers clearly demonstrated at their two landing sites on Mars more than 35 years ago. By conducting granular physics and physical properties research on the Moon and Mars, accurate models can continue to simulate methods for understanding and minimizing these fluid-like effects, both in space and on planetary surfaces.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Reduced gravity poses another unique problem in fluid physics: Small forces that are often masked by gravity on Earth can dominate fluids in otherwise unexpected ways in space. For example, in closed-circuit heating, cooling, and power generation cycles, the fluids boil into buoyant vapors that are readily controlled by gravity. But in space, vapor bubbles do not rise, but grow in size. This dries out surfaces, restricts flow passages, and renders such equipment useless. Condensing systems face similar challenges. New, highly reliable means with which to control such processes in the absence of gravity need to be developed for use in life support, thermal control, power production and liquid fuels storage and handling.

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Studies of combustion in reduced gravity can lead to a greater understanding of terrestrial combustion in a wide range of settings, including industrial processes and uncontrolled fires. Flames are controlled by energy released from exothermic chemical reactions and the interaction of this energy with the atmosphere. The microgravity combustion program was able to successfully eliminate buoyancy—a force that dominates terrestrial combustion—effects in space to understand some of the more subtle and less-understood characteristics of fire. Research on ignition and flammability limits are fundamental combustion topics. These limits refer to the critical conditions beyond which combustion is not possible. They primarily depend on factors such as fuel type, pressure and temperature of the environment, concentrations of oxygen, and gravity level. For this reason, an improved knowledge of combustion in reduced gravity is necessary for adapting fire safety concepts and systems to the more challenging conditions in space. For example, certain materials used extensively in space could potentially serve as solid fuel sources for a spreading fire. Because flame growth is a major concern in spacecraft fire safety, fundamental studies on solid fuel flammability of these materials are essential to fire safety in space. Previous fundamental research has been applicable to fire safety measures both in space and on the ground. NASA free fall facilities have been used to eliminate, for fleeting seconds, the effects of buoyancy that occur in the terrestrial environment. By varying or eliminating gravitational forces, this research has led to technologies for space exploration and contributed to insights into the fundamental processes involved in combustion. Future advances in these areas could improve understanding of material flammability, fire prevention systems, and even suppression agents used to extinguish a fire.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Combustion and Fire Behavior in Reduced Gravity

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The study of microgravity combustion has enabled research designed specifically for space exploration, while also providing new insights into fundamental combustion processes for terrestrial applications. When combined with theory and numerical models, microgravity combustion experiments have enhanced our knowledge of basic combustion phenomena, contributed to greater fire safety for present and future space missions, and provided insights to practical industrial applications on Earth. Combustion research typically focuses on the process by which energy is released into a surrounding medium in the form of flames; however, when studying fire on Earth, the effects of gravity are difficult to isolate and can only be individualized through analysis and simulation. By varying or eliminating the effects of gravity, it is possible to observe fundamental characteristics that are important to combustion systems. This knowledge can be used to select better materials and to detect and suppress fires more efficiently.

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Issues in Fire Behavior & Safety:

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In case of a fire, early detection will minimize the damage it can cause. Relevant questions are: what products of a fire can be sensed faster and produce a more reliable fire detection? How can the sensor information be used to effectively fight the fire? For example, early investigations showed that the size of smoke particles emerging from flames in reduced gravity can be different from those in Earth gravity. So detector design and data interpretation still needs to evolve. In the instance of a fire on-board a spacecraft, crewmembers could contain the flames using standard suppressant methods, such as releasing gas spray or droplets, in addition to approaches developed specifically for this environment: Cutting off air ventilation and depressurizing the spacecraft cabin. Fire suppressants used in spacecraft should be efficient and nontoxic, and they should cause little or no damage to the equipment. They also should be easy to clean up with on-board resources and have the ability to reach any corner of the ship. An aqueous gel or foam was used for Apollo, Skylab, Mir, and the ISS; bottled carbon dioxide is also on the ISS, and halon was used on the shuttle. Even with these in hand, the most effective suppressant agent and deployment methods have yet to be identified for a variety of specific space applications.

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The first line of defense for stopping a fire is prevention. NASA has developed screening methods to identify acceptable materials and reduce their flammability. Currently, a normal gravity test used for solid materials considers upward ignition and flame growth where, if the flame spreads more than six inches without self-extinguishing, the material itself fails to qualify. Continued improvement of the screening methods suitable for environments in present and future spacecraft is needed.

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In space, evacuation is not always a viable option so fire prevention is vital; if it occurs, fire cannot be allowed to grow. Fire safety encompasses prevention, detec tion, suppression, and post-fire recovery.

Fire Safety and Prevention in Space

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An important observation made in space was that the absence of buoyancy caused a flame to reshape into a sphere. Buoyancy is the driving force in the plume because of high temperatures and density differences. Verifying and understanding analytical and experimental results, as well as identifying and clarifying the interactions among suppression agents, flames, and surfaces in reduced gravity, will provide insight into the fundamental differences in balances between buoyancy and other forces. This basic research could contribute to the development of improved fire-suppression systems.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Every pound launched into space translates immediately into overall mission costs, in both the financial and spatial sense; therefore, any opportunity to safely reduce the total spacecraft mass provides better economy and flexibility in transporting additional supplies and equipment. Using high-tech materials, lightweight structures can be fabricated for terrestrial and space applications, but the materials design and fabrication processes require a deep understanding of the relationship between a material’s properties and structure. Ultimately, this research is applied to a wide variety of manufacturing processes based on the ways in which they affect the material’s microstructure and quality. For instance, high-strength, low-density materials can be produced using manufacturing processes that combine vapor phase reactants with reactants in gas, liquid, or solid phases. This process is used to produce solar cells, along with coatings and lubricants, that can withstand the extreme temperatures and harsh conditions present in the space environment. Materials can be designed with protective properties for deep space exposure to temperatures on the verge of absolute zero (2.7 Kelvin) or up to 2200°C and higher; these qualities are of particular importance when manufacturing such parts as rocket nozzles.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Weighing the Matter of Materials

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Materials science successfully exploits the benefits of investigating fundamental physical processes and phenomena that are made more visible by the absence of gravity in space. The research clarified some of the roles of buoyancy-driven convection, sedimentation, and hydrostatic pressure in the processing of a range of materials, including metals, alloys, glasses, ceramics, polymers, semiconductors, and composites. These are processes that include melting raw materials and then allowing them to solidify by crystallization in controlled ways; it is possible to isolate and study the growth of crystals in microgravity with much greater clarity to determine how well the process works and how it can be improved. Past research generated knowledge leading to improvements in terrestrial production processes and the development of new benchmarks for advanced quality. In the future, research in this area might lead to new fabrication methods and materials synthesis—contributing to the efficient manufacturing and design of more products. The next stage of this research should also reflect the need to develop materials that can help make long-duration spaceflight more affordable and safer.

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The Matter of Materials

Exploring Space and Time High-precision measurements in space can test relativistic gravity and fundamental physics in ways that are not practical on Earth. Einstein’s theory of general relativity suggests that clock rates vary with velocity and gravitational potential but should not depend on clock position or orientation. This fundamental theory can be further tested with cold atoms and access to a wider gravity gradient spectrum in space. Atomic clock performance has been improved due in part to research supported by NASA. Space-based precision measurements could contribute to space exploration through improved navigation and communication based on this greater precision. Complex fluids and soft condensed matter are excellent candidates for study in the microgravity environment due to their susceptibility to gravity. Just as they are useful for exploring basic phenomena, complex fluids and soft matter are ubiquitous in food, chemicals, petroleum, pharmaceuticals, and the plastics industries. The direct contribution of these materials and related processes amounts to about 5% of the U.S. GDP and about 30% of the manufacturing output of the U.S. alone.

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The NASA Materials International Space Station Experiment (MISSE) mounted trays of materials outside the ISS to assess the ways in which the materials reacted to a number of conditions, including atomic oxygen, hard vacuum, UV radiation, thermal cycling, and debris impact. Materials data, such as those gathered from MISSE, can be incorporated into computer models that allow for virtual synthesis and processing of new materials, drastically decreasing the time and cost of developing new materials that are unique to NASA’s needs. Pores and voids often form in metal castings on Earth. Microgravity conditions allow for exploring the way metals behave at the microscopic scale and at a macroscopic level on Earth. This will help show the process with which voids form and can provide insights into preventing them.

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A test cell for the Mechanics of Granular Materials (MGM) experiment on STS-89 is compressed approximately 20- and 60-minutes after the start of an experiment. Sand and soil grains have surfaces that can cause friction as they roll and slide against each other—they can even cause sticking and form small voids between grains. This particle-force interaction can cause soil to behave like a liquid under certain conditions, such as loose sediment in an earthquake or powders handled during industrial processes. These experiments use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Engineering a Personal, Portable Atmosphere The human body’s internal temperature fluctuates daily based on hormonal cues that regulate functions such as food intake, sleep, and immune response. For example, resting heat production for a woman is approximately 18% lower than the average male measurement of 1824 kcal/day. Another factor—in this case, unique to the space environment—is the secondary effect of a drop in body temperature due to bone and muscle atrophy. Data on this type of information is critical when designing efficient and effective environmental systems. An individual’s circadian rhythm is programmed by a 24-hour Earth day, but in orbit, astronauts speed through the day/night cycle every 90 minutes on average. Evidence suggests that this change delays circadian temperature fluctuations. For example, as reported in ground-based studies, circadian de-synchronization was linked to disruptions in sleep and eating cycles, altered insulin regulation, and elevated levels of stress hormones. Research in this area contributes to engineering solutions in the design of sleeping quarters and provides insight into potential methods for maintaining normal sleep cycles during long-duration trips, either on Earth or in space.

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Exploration Enabled by Space Suit Technology Advances in thermoregulation technologies are due in large part to innovative engineering concepts, some of which are the result of safety adjustments following tragic engineering failures. Since the Challenger accident, crew members are required to wear a pressure suit during space shuttle launch and landing that consists of a pneumatic counterpressure garment, a cooling garment, and an outer, multilayer protective shell. Despite the liquid cooling garment, crew members report feeling hot during re-entry; this is a concern because increasing body temperature could reduce their orthostatic tolerance during re-entry.

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The human body has a resting core temperature of 37°C ± 1°C (98.6°F ± 1.8°F), with overheating being more of a concern than overcooling. The development of the space suit allows astronauts to maintain homeostasis, shielding their bodies from the harsh conditions of space and maintaining a comfortable pressure. The carefully engineered environment provides oxygen supply, pressure mediation, and temperature control. Precise thermoregulation is particularly relevant when performing an EVA on a planet with a thin atmosphere. On Mars, for instance, the temperature difference between the ground and a few feet off the ground is quite large; a space suit, however, could stabilize the internal environment regardless of the extreme and dynamic space conditions surrounding the astronaut on the outside.

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Essential Technologies

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Historically, space suits have included a portable life support system, artificial atmosphere, communications subsystem, and tools that enable crew members to accomplish critical mission tasks during EVA. The total EVA time has increased by an order of magnitude with each new generation of space suit, outlining a notable pattern in emerging exploration missions.

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Research in this capacity could be focused on establishing vehicle mobility that is equal to the performance of ground-use geological survey equipment. Other studies could explore protection from environmental hazards such as debris and micrometeorites and could incorporate new technologies, such as variable pressure regulation, into designs.

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The requirements for future EVA systems include crew safety and mobility, EVA capability when tethered to the spacecraft umbilical, and surface EVA performance. A two-suit design has been proposed for EVAs: the first suit optimized for launch, entry, ascent, and initial EVA capability, and the second suit optimized for surface EVA capability. By partnering with other systems engineering experts in academia, industry, and the U.S. Department of Defense, NASA could leverage innovative designs even further.

Space suits have many layers and play an important role in keeping the astronaut safe in the harsh space environment. The most limiting piece of equipment is the glove, as the many layers restrict important but delicate hand manipulations. New glove designs will aid in enabling astronauts to explore new regions of space as geologists would on Earth.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Living Off the Land:

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Conditions on Mars are closer in many respects to the terrestrial nature of Earth than those on any other planet in our system. For years, both popular fiction and scientific visualization has projected human life on Mars. So it is easy to picture humans constructing outposts block-byblock and even utilizing martian resources for the production of oxygen and water. In-situ resource utilization (ISRU), more generally referred to as “living off the land,” as well as space construction techniques, are both being explored as an avenue for long-term settlements on planetlike bodies elsewhere in our solar system. The real challenge is not envisioning the possibilities of these goals; rather it is the development of methods for exploiting any available resources to sustain human habitation. In addition, there remains the question of how to build structures to withstand the environment of Mars using materials and methods that have been tested only on Earth. Similar considerations apply to our Moon.

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A number of modeling studies have demonstrated that, when all life-sustaining system elements are included, the amount of oxygen that could be produced from lunar resources in one year exceeds, by more than an order of magnitude, the mass of equipment that would need to be brought from Earth to produce oxygen on the Moon. The most accessible and abundant source of energy on the surface of Mars or the Moon is solar power, but there are restrictions in current technologies. Very advanced ISRU systems in the future could potentially produce photovoltaic arrays for energy production systems using materials processed from lunar or Mars soil, as well as solid materials for fabrication of spare parts and construction components, materials for radiation shielding, and so forth. In advanced applications, ISRU may play a role in the construction of pressurized structures for planetary surface operations.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Just as confirmed techniques of construction on Earth likely will not carry over to Mars, it would be costly and somewhat impractical to manufacture and transport materials to other celestial bodies. ISRU would include harnessing the molecules found in regolith or soil, or in the atmosphere, for synthesis of materials to be used as manufacturing components. Initial needs for ISRU will likely include propellant synthesis, energy storage, and life support consumables. If hydrogen is collected from solar wind or manufactured from water, methane for use as a rocket fuel can be synthesized from the CO2 available in the martian atmosphere. By using resources found at the destination site, enormous mass and volume can be conserved on the spacecraft traveling from Earth.

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Harnessing Non-Terrestrial Resources for Exploration Technologies

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The length of mission, purpose, initial crew size, and resupply period affect the habitat design. Maintenance should minimize impact to a mission with respect to time, power, complexity, safety, and mass. Advanced structures, the design of which should be informed by extensive research, will be required to reduce mass, enhance radiation protection, and operate in the extreme conditions found on the surface of the Moon or Mars. For example, research into dust-tolerant mechanisms and fluid connectors is important to prevent failures that may be caused by the environment.

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To date, no large structures have been assembled in partial gravity; however, Desert Research and Technology Studies (RATS) is a research initiative sponsored by NASA that evaluates variables such as technology, human-robotic systems, and extravehicular equipment in the high desert near Flagstaff, Arizona. Their systems include rovers, EVA timelines, and ground support.

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Planetary surface construction covers site preparation, equipment, construction, and habitat design. Materials would likely be unpacked, transported some distance, and assembled. Construction on the Moon and Mars will likely include assembly and deployment of modules. Experience constructing and assembling structures on the surface of the Moon is lacking, with the exception of small experiments conducted during the Apollo program. Those experiments demonstrated the challenges for astronauts due to the mobility limitations created by spacesuits and tools.

Backg round Image “Chur ned-Up Rocky Debr is and Dust“ (Mars) Cred it: NASA.

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Space Construction with Earth-Tested Methods

During DesertRATS excursions, rovers, spacesuits, and other prototypes—such as the electric tractor with a backhoe to simulate martian regolith digging—aid in understanding the limits of astronaut mobility. Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Report Recommendations: Establishing a

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The examples presented in the previous pages illustrate only some of the mechanisms, uncertainties, and unique phenomena that are a part of the space environment. These are select areas that could benefit from fundamental research in the life and physical sciences, but they also provide a glimpse into the possible applications for this research both in space and for society as a whole. These examples of enabling research, and descriptions of scientific insights enabled by access to space, are explored in greater detail in the full NRC report Recapturing a Future for Space Exploration. This publication and the full report are available online at http://www.nap.edu.

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Areas of Highest-Priority Research NASA has a strong and successful track record in human spaceflight made possible by a backbone of science and engineering accomplishments. Decisions regarding future space exploration, however, will require the generation and use of new knowledge in the life and physical sciences for successful implementation of any options chosen.

Copyright © 2012. National Academies Press. All rights reserved.

Recapturing a Future for Space Exploration identifies and prioritizes research questions important both to conducting successful space exploration and to increasing the fundamental understanding of physics and biology that is enabled by experimentation in the space environment. These two interconnected concepts—that science is enabled by access to space and that science enables future exploration missions—testify to the powerful complementarity of science and the human spaceflight endeavor. It is not possible in this brief summary to describe or even adequately summarize the highestpriority research recommended by the committee. However, these recommendations, which were selected as having the highest overall priority for the coming decade, are listed briefly as broad topics below. The committee considered these recommendations to be the minimal set called for in its charge to develop an integrated portfolio of research enabling and enabled by access to space and thus did not attempt to further prioritize among them. In addition, it recognized that further prioritization among these disparate topic areas will be possible only in the context of specific policy directions to be set by NASA and the nation.

Plant and Microbial Biology Plants and microbes evolved at Earth’s gravity (1 g), and spaceflight represents a completely novel environment for these organisms. Understanding how they respond to these conditions holds great potential for advancing knowledge of how life operates on Earth. In addition, plants are important candidates for components of a biologically based life support system for prolonged spaceflight missions, and microbes play complex and essential roles in both positive and negative aspects of human health, in the potential for degradation of the crew environment through fouling of equipment, and in bioprocessing of the wastes of habitation in long-duration missions. The highest-priority research, focusing on these basic and applied aspects of plant and microbial biology, includes: • Multigenerational studies of International Space Station microbial population dynamics; • Plant and microbial growth and physiological responses; and • Roles of microbial and plant systems in long-term life support systems.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

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Behavior and Mental Health The unusual environmental, psychological, and social conditions of spaceflight missions limit and define the range of crew activities and trigger mental and behavioral adaptations. The adaptation processes include responses that result in variations in astronauts’ mental and physical health, and strongly stress and affect crew performance, productivity, and well-being. It is important to develop new methods, and to improve current methods, for minimizing psychiatric and sociopsychological costs inherent in spaceflight missions, and to better understand issues related to the selection, training, and in-flight and postflight support of astronaut crews. The highest-priority research includes: • Missionrelevant performance measures; • Long-duration mission simulations; • Role of genetic, physiological, and psychological factors in resilience to stressors; and • Team performance factors in isolated autonomous environments.

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Animal and Human Biology

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Human physiology is altered in both dramatic and subtle ways in the spaceflight environment. Many of these changes profoundly limit the ability of humans to explore space, yet also shed light on fundamental biological mechanisms of medical and scientific interest on Earth. The highest-priority research, focusing on both basic mechanisms and development of countermeasures, includes: • Studies of bone preservation and bone-loss reversibility factors and countermeasures, including pharmaceutical therapies; • In-flight animal studies of bone loss and pharmaceutical countermeasures; • Mechanisms regulating skeletal muscle protein balance and turnover; • Prototype exercise countermeasures for single and multiple systems; • Patterns of muscle retrainment following spaceflight; • Changes in vascular/interstitial pressures during long-duration space missions; • Effects of prolonged reduced gravity on organism performance, capacity mechanisms, and orthostatic intolerance; • Screening strategies for subclinical coronary heart disease; • Aerosol deposition in the lungs of humans and animals in reduced gravity; • T cell activation and mechanisms of immune system changes during spaceflight; • Animal studies incorporating immunization challenges in space; and • Studies of multigenerational functional and structural changes in rodents in space.

Crosscutting Issues for Humans in the Space Environment Translating knowledge from laboratory discoveries to spaceflight conditions is a two-fold task involving horizontal integration (multidisciplinary and transdisciplinary) and vertical translation (interaction among basic, preclinical, and clinical scientists to translate fundamental discoveries into improvements in the health and wellbeing of crew members during and after their missions). To address the cumulative effect of a range of physiological and behavioral changes, an integrated research approach is warranted. The highest-priority crosscutting research issues include: • Integrative, multisystem mechanisms of post-landing orthostatic intolerance; • Countermeasure testing of artificial gravity; • Decompression effects; • Food, nutrition, and energy balance in astronauts; • Continued studies of short- and long-term radiation effects in astronauts and animals; • Cell studies of radiation toxicity endpoints; • Gender differences in physiological effects of spaceflight; and • Biophysical principles of thermal balance.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Report Recommendations (Continued) Fundamental Physical Sciences in Space The fundamental physical sciences research at NASA has two overarching quests: (1) to discover and explore the laws governing matter, space, and time and (2) to discover and understand the organizing principles of complex systems from which structure and dynamics emerge. Space offers unique conditions in which to address important questions about the fundamental laws of nature, and it allows sensitivity in measurements beyond that of groundbased experiments in many areas. Research areas of highest priority are the following: • Study of complex fluids and soft matter in the microgravity laboratory; • Precision measurements of the fundamental forces and symmetries; • Physics and applications of quantum gases (gases at very low temperatures where quantum effects dominate); and • Behavior of matter near critical phase transition.

 Applied Physical Sciences

Copyright © 2012. National Academies Press. All rights reserved.

Applied physical sciences research, especially in fluid physics, combustion, and materials science, is needed to address design challenges for many key exploration technologies. This research will enable new exploration capabilities and yield new insights into a broad range of physical phenomena in space and on Earth, particularly with regard to improved power generation, propulsion, life support, and safety. Applied physical sciences research topics of particular interest are as follows: • Reduced-gravity multiphase flows, cryogenics, and heat transfer database development and modeling; • Interfacial flows and phenomena in exploration systems; • Dynamic granular material behavior and subsurface geotechnics; • Strategies and methods for dust mitigation; • Complex fluid physics in a reduced-gravity environment; • Fire safety research to improve screening of materials in terms of flammability and fire suppression; • Combustion processes and modeling; • Materials synthesis and processing to control microstructures and properties; • Advanced materials design and development for exploration; and • Research on processes for in situ resource utilization.

Translation to Space Exploration Systems The translation of research to space exploration systems includes identification of the technologies that enable exploration missions to the Moon, Mars, and elsewhere, as well as the research in life and physical sciences that is needed to develop these enabling technologies, processes, and capabilities. The highest-priority research areas to support objectives and operational systems in space exploration include: • Two-phase flow and thermal management; • Cryogenic fluid management; • Mobility, rovers, and robotic systems; • Dust mitigation systems; • Radiation protection systems; • Closed-loop life support systems; • Thermoregulation technologies; • Fire safety: materials standards and particle detectors; • Fire suppression and post-fire strategies; • Regenerative fuel cells; • Energy conversion technologies; • Fission surface power; • Ascent and descent propulsion technologies; • Space nuclear propulsion; • Lunar water and oxygen extraction systems; and • Planning for surface operations, including in situ resource utilization and surface habitats. For each of the high-priority research areas identified above, the committee classified the research recommendations as enabling for future space exploration options, enabled by the environment of space that exploration missions will encounter, or both.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, 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. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of 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 achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering.

Copyright © 2012. National Academies Press. All rights reserved.

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. Harvey V. Fineberg 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 government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. www.nationalacademies.org

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,

Copyright © 2012. National Academies Press. All rights reserved.

This booklet is based on the National Research Council report Recapturing a Future for Space Exploration: Life and Physical Sciences Research for a New Era, available online at www.nap.edu.

Research for a Future in Space : The Role of Life and Physical Sciences, National Academies Press, 2012. ProQuest Ebook Central,