Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
Research for a
Future in Space
The Role of Life and Physical Sciences
Copyright © National Academy of Sciences. All rights reserved.
ISBN 978-0-309-26103-6
32 pages
8 1/2 x 11
PAPERBACK (2012)
Research for a Future in Space: The Role of Life and Physical
Sciences
Committee for the Decadal Survey on Biological and Physical Sciences in
Space;Space Studies Board; National Research Council
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
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, ndings, conclusions, or
recommendations expressed in this publication are those of the author(s) and do not necessarily
reect 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.
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, Pacic Northwest National Laboratory
GAYLE E. WOLOSCHAK, Northwestern University Feinberg School of Medicine
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:
Research for a
Future in Space
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
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
2
Research for a Future in Space
The Issues of Bone Loss & Nutritional Needs in Space
Preventing Bone Loss
Shifts in Astronaut Health During Long Periods in Space
Chronic Sleep Loss in Space
Coping with Conned Space Environments
Monitoring Brain and Behavioral Functions in Astronauts
Group Dynamics in an Extreme Environment
The Roles of Plant & Microbial Growth
Up-Rooted: Plant Growth in Space
Managing Microbes as Spaceight Companions
The Risk of Cellular & Genetic Changes in Long-Term Space Travel
Muscle Weakness and Protein Degradation
The Nature of Fluid Physics in Space
Recycling Air and Water in Spacecraft
Addressing Other Aspects of Fluid Physics in Space
Issues in Fire Behavior & Safety: Prevention, Detection, Suppression
Combustion and Fire Behavior in Reduced Gravity
Fire Safety and Prevention in Space
The Matter of Materials & the Relativity of Time
Weighing the Matter of Materials
Essential Technologies for Space Suits
Engineering a Personal, Portable Atmosphere
Exploration Enabled by Space Suit Technology
Living Off the Land: Using In-Situ Materials

Harnessing Non-Terrestrial Resources for Exploration Technologies
Space Construction with Earth-Tested Methods
Report Recommendations
About the Report
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):
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 benets for humankind as it embarks on
a new era of space exploration.
Recapturing a Future

for Space Exploration
Life and Physical Sciences Research for a New Era
Contents
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
3
Research for a Future in Space
The Issues of Bone Loss & Nutritional Needs in Space
Preventing Bone Loss · Nutrition and Space Foods
Shifts in Astronaut Health During Long Periods in Space
Chronic Sleep Loss in Space · Shifts in Cardiovascular Health
Coping with Conned Space Environments
Monitoring Brain and Behavioral Functions in Astronauts ·
Group Dynamics in an Extreme Environment
The Roles of Plant & Microbial Growth
Up-Rooted: Plant Growth in Space ·
Managing Microbes as Spaceight Companions
The Risk of Cellular & Genetic Changes in Long-Term Space Travel
Muscle Weakness and Protein Degradation · Radiation During Spaceight
The Nature of Fluid Physics in Space
Recycling Air and Water in Spacecraft ·
Addressing Other Aspects of Fluid Physics in Space
Issues in Fire Behavior & Safety: Prevention, Detection, Suppression
Combustion and Fire Behavior in Reduced Gravity ·
Fire Safety and Prevention in Space
The Matter of Materials & the Relativity of Time
Weighing the Matter of Materials · Exploring Space and Time
Essential Technologies for Space Suits
Engineering a Personal, Portable Atmosphere ·
Exploration Enabled by Space Suit Technology

Living Off the Land: Using In-Situ Materials
Harnessing Non-Terrestrial Resources for Exploration Technologies ·
Space Construction with Earth-Tested Methods
Report Recommendations
Contents
4-5
6-7
8-9
10-11
12-13
14-15
16-17
18-19
20-21
22-23
24-25
26-28
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
4
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 spaceight 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 scientic and engineering research accomplishments. These
milestones and future developments are made possible through ongoing advances in
life and physical sciences research.
Looking to the future, signicant 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 connement 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. Specically, NASA’s compelling future in space exploration
will ow 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
identies these research opportunities
and imperatives that can be achieved most rapidly and efciently 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 signicant barriers to
extended human spaceight 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 ame growth and impact re behavior in reduced-gravity conditions?
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
5
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 eld of
medicine from access to data on physiological changes, such as heart muscle atrophy
and decreasing bone mass, in astronauts during spaceight.
But discovery is just one component of a comprehensive research program. To
generate progress in all relevant areas needed for human spaceight, 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 efcient, making human spaceight
more accessible than was possible in these last few decades. More specically, 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
spaceight?
Overcoming these specic challenges, as well as the more general scientic
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 benet 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 spaceight still remain?
These examples of enabling research, and descriptions of scientic 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 .
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
6
© 2011 by Lindsay Davidson, under a Creative Commons
Attribution-NonCommercial-ShareAlike license.
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.
Based on information from previous missions, some common vitamin and mineral deciencies
have been identied in astronauts. In particular, several deciencies or insufciencies 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 ight, they require a vitamin D supplement. This
nutrient, which is the only vitamin routinely supplemented in spaceight, is required for
calcium absorption—an important consideration when bone loss is a clearly documented
negative consequence of spaceight.
In order to predict and mitigate any decits 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 specic 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 insufcient information on the ways in which these same processes affect foods in space,
including the effects of space radiation.
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 uctuations
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.
Background edited from “Osteoporotic Bone”
© 2008 by Alan Boyde, Bone Research Society, UK.
Image Credit: NASA
Nutritional Needs in Space
The Issues of Bone Loss &
Over millions of years, the structures of organisms on Earth have
evolved under the constant inuence 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 nutrition-
ally adequate diet in space must be maintained for proper body func-
tion. 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 understand-
ing of the effects of reduced gravity on the many and complex sys-
tems of the human body.
Preventing 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.
After being in space for six months, astronauts typically need more than two and a half
years for their BMD to return to pre-ight 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 benets when coupled with imposing
negative pressure to the lower-body during both 30- and 60-day periods of bed rest.
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.
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
7
© 2011 by Lindsay Davidson, under a Creative Commons
Attribution-NonCommercial-ShareAlike license.
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.
Based on information from previous missions, some common vitamin and mineral deciencies
have been identied in astronauts. In particular, several deciencies or insufciencies 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 ight, they require a vitamin D supplement. This
nutrient, which is the only vitamin routinely supplemented in spaceight, is required for
calcium absorption—an important consideration when bone loss is a clearly documented
negative consequence of spaceight.
In order to predict and mitigate any decits 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 specic 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 insufcient information on the ways in which these same processes affect foods in space,
including the effects of space radiation.
Physiological interactions with micro-
gravity conditions are largely unpre-
dictable, including our understanding
of the effects on vitamin levels. Dietary
supplements and nutritionally evalu-
ated space foods are approaches to

combating deciencies and ensuring
the health of astronauts.
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 uctuations
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.
Background edited from “Osteoporotic Bone”
© 2008 by Alan Boyde, Bone Research Society, UK.
Image Credit: NASA
Nutritional Needs in Space
The Issues of Bone Loss &
The skeletal system of animals provides a solid framework for structural support, protection,
). 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
After being in space for six months, astronauts typically need more than two and a half
years for their BMD to return to pre-ight 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—
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 benets when coupled with imposing

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
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
8
Shifts in Astronaut Health
Adequate sleep—obtained on a regular schedule reecting the
brain’s natural (circadian) sleep/wake rhythm—is necessary for
maintaining optimal health, alertness, and performance. Cardio-
vascular functioning depends on the delivery of blood to all organs
at optimal perfusion pressure. In space, however, factors that de-
termine various physiological rhythms and efciencies, 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 condi-
tions will be critical to the success of extended missions in space.
Chronic Sleep Loss in Space
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 difcult 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 specic incidents, such as the Mir–

Progress collision on June 25, 1997.
Scientic 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 inuence 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 “ghting against” Earth’s gravity.
More precisely, uids 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 rst few days, the body attempts to get rid of this uid and there is a decrease in total
blood volume in the astronaut. In-ight 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.
© 2006 by Dr. S. Girod, Anton Becker, under a
Creative Commons Attribution-Share Alike license.
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 spaceights in particular, which have raised the question of a
clinically serious problem. Rigorous quantication of the frequency and variability of
irregular heartbeats both before and during ight—along with non-invasive assessments
of cardiac electrophysiological properties—will be necessary to determine the magnitude
and signicance 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 y 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 ight 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
sufciently reduce the risk of cardiovascular events prior to and during spaceight.
With little gravity resistance for the heart to pump against, signicant 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 can
not 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.
Image Credit: NASA
During Long Periods in Space
During Long Periods in Space
Shifts in Astronaut Health
Background image “Gyrus Dentatus” © 2005 by MethoxyRoxy,
under a Creative Commons Attribution-ShareAlike license.
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
9
Shifts in Astronaut Health
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 difcult 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 specic incidents, such as the Mir–
Scientic 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
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 inuence 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 “ghting against” Earth’s gravity.
More precisely, uids 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 rst few days, the body attempts to get rid of this uid and there is a decrease in total
blood volume in the astronaut. In-ight 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.
© 2006 by Dr. S. Girod, Anton Becker, under a
Creative Commons Attribution-Share Alike license.
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 spaceights in particular, which have raised the question of a
clinically serious problem. Rigorous quantication of the frequency and variability of
irregular heartbeats both before and during ight—along with non-invasive assessments

of cardiac electrophysiological properties—will be necessary to determine the magnitude
and signicance 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 y 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 ight 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
sufciently reduce the risk of cardiovascular events prior to and during spaceight.
Astronauts in space experience a vari-
ety of sleep difculties that can be as-
sessed by tracking their brain waves
during each phase of sleep. Electroen-
cephalograph machines monitor and
measure electrical impulses from the
brain, muscles, eyes, and heart; dur-
ing spaceight, a cap of electrodes is
secured to the astronaut’s head to re-
cord electrical activity as brain waves.
With little gravity resistance for the heart to pump against, signicant 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 can-
not 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.
Image Credit: NASA

During Long Periods in Space
During Long Periods in Space
Shifts in Astronaut Health
Background image “Gyrus Dentatus” © 2005 by MethoxyRoxy,
under a Creative Commons Attribution-ShareAlike license.
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
10
Monitoring Brain and Behavioral Functions in Astronauts
Long-duration space missions require a crew to perform at peak health in every respect,
overcoming obstacles that may arise from living in a conned, 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.
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 mission-
related tasks as well as their temporary sense of well-being.
Astronauts selected and trained for spaceight 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 identied or
developed to assess astronauts’ capacity for sustaining performance in the face of signicant

stressors, particularly in the context of challenging situations such as docking.
Space Environments
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, evidence-
based methods for preventing a breakdown in communication, or the identication of
methods for promoting group cohesion, will be important. Rigorously designed experimental
simulations—mirroring actual mission parameters like isolation, connement, and
workload—are needed to provide further insights into group dynamics and cooperation.
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.
Image Credit: NASA
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 uctu
ate. It is important to identify individual characteristics that facilitate coping with the space
environment and that contribute to healthy group dynamics during extended missions.
Image Credit: NASA
One of the many challenges faced by astronauts in space is connement in close quarters with
their crew, coupled with limited contact with friends and family. This type of connement is not

unique to space, but research exploring the group dynamics experienced by current astronauts
could benet 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 radia-
tion 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 impli-
cations on Earth, these inquiries could guide healthy group dynamics and individual well-being
in space.
Background Image “Star Trails in Space” Credit: NASA (ISS).
Coping with Conned
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
11
Long-duration space missions require a crew to perform at peak health in every respect,
overcoming obstacles that may arise from living in a conned, 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.
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 mission-
Astronauts selected and trained for spaceight 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 identied or
developed to assess astronauts’ capacity for sustaining performance in the face of signicant
Space Environments
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, evidence-
based methods for preventing a breakdown in communication, or the identication of
methods for promoting group cohesion, will be important. Rigorously designed experimental
simulations—mirroring actual mission parameters like isolation, connement, and
workload—are needed to provide further insights into group dynamics and cooperation.
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.
Image Credit: NASA
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 uctu-
ate. It is important to identify individual characteristics that facilitate coping with the space
environment and that contribute to healthy group dynamics during extended missions.

Image Credit: NASA
One of the many challenges faced by astronauts in space is connement in close quarters with
their crew, coupled with limited contact with friends and family. This type of connement is not
unique to space, but research exploring the group dynamics experienced by current astronauts
could benet 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 radia-
tion 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 impli-
cations on Earth, these inquiries could guide healthy group dynamics and individual well-being
Background Image “Star Trails in Space” Credit: NASA (ISS).
Image Credit: NASA
Coping with Conned
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
12
It has taken eons for Earth to develop its current physical state, and its biosphere’s characteris-
tics 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 uids 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 move-
ment 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 space-
ight? 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.
Up-Rooted: Plant Growth in Space
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 dene 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.
Space environments, however, present factors other than microgravity that could potentially
alter these specialized functions. Components of the spaceight 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 spaceight 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 ltered and compressed CO
2
(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 conrm 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 beneting 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 at to the ground.
Managing Microbes as Spaceight Companions
Microbes are a unique component of the spaceight environment. Attempts to broadly

eradicate bacteria in spacecraft would not only be extremely difcult, 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 benecial 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.
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
ights in which evacuation may not be an option. Research has indicated that bacteria
such as E. coli can form protective biolms in microgravity conditions just as they do
on Earth.
Research on the effects of the spaceight environment on microbes is limited. The gap
in knowledge is partly due to a lack of isolation technology, such as alternative platforms
called free-yers, 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 Credit: NASA
A biolm 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 difcult to eradicate.
Microbial GrowthThe Roles of Plant &
© 2005 CDC/Rodney M. Donlan, Ph.D.; Janice Carr (PHIL #7488) Background Image “Roots” © 2008 by sebarex via Stock.XCHNG.
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
13

It has taken eons for Earth to develop its current physical state, and its biosphere’s characteris-
tics 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 uids 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 move-
ment 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 space-
ight? 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
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 dene the structure
of the root and shoot systems. This mechanism, along with other physiological functions, is
Space environments, however, present factors other than microgravity that could potentially
alter these specialized functions. Components of the spaceight 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,
Pressure is one consideration in the spaceight 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
(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 conrm minimums that can be

Controlled crop cultivation in this capacity could provide insights into optimizing plant growth
conditions and responses, potentially beneting human life and health on Earth as well. For
example, research into plant responses to gravity could contribute to innovations in crop recovery
Managing Microbes as Spaceight Companions
Microbes are a unique component of the spaceight environment. Attempts to broadly
eradicate bacteria in spacecraft would not only be extremely difcult, 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 benecial 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.
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
ights in which evacuation may not be an option. Research has indicated that bacteria
such as E. coli can form protective biolms in microgravity conditions just as they do
on Earth.
Research on the effects of the spaceight environment on microbes is limited. The gap
in knowledge is partly due to a lack of isolation technology, such as alternative platforms
called free-yers, 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.
Space travel will likely require strategies for self-suf-
ciency 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 ights, is the devel-
opment of bioregenerative life support systems. A self-
sustaining system could utilize plants and microbes to
recycle waste and supply food, oxygen, and water to crew
members.
Image Credit: NASA
A biolm 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 difcult to eradicate.
Microbial GrowthThe Roles of Plant &
© 2005 CDC/Rodney M. Donlan, Ph.D.; Janice Carr (PHIL #7488) Background Image “Roots” © 2008 by sebarex via Stock.XCHNG.
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
Image Credit: NASA
14
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 physi-
ological 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 condi-
tions 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 de-
pends 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?
Muscle Weakness and Protein Degradation
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 inuences of gene expression. Previous studies on
the effects of spaceight on muscle mass, strength, and contraction have focused more
directly on protein changes. For example, studies on rodent muscle immediately following
spaceight 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 long-
duration studies on the effects of countermeasures. For example, an ISS exercise facility
could simultaneously test equipment designed for spaceight 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.
Radiation During Spaceight
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.
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 spaceight, such as the biological consequences of protons
and high LET radiation.
Image Credit: NASA
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 pro
tons, which are similar in their radiobiological effects to the low LET radiation in conventional
medical x-rays or gamma rays used in radiation therapy.
Background Image “Potato Amyloplasts” © 2004 by Mnolf, under a Creative Commons Attribution-Share Alike license.
The Risk of Cellular & Genetic Changes in Long-Term Space Travel
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
Image Credit: NASA
15
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 physi-
ological 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 condi-
tions 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 de-
pends 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
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 inuences of gene expression. Previous studies on
the effects of spaceight on muscle mass, strength, and contraction have focused more

directly on protein changes. For example, studies on rodent muscle immediately following
spaceight 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,
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 long-
duration studies on the effects of countermeasures. For example, an ISS exercise facility
could simultaneously test equipment designed for spaceight exercise while monitoring
the functioning of multiple organ systems on a metabolic level. This also has the potential
Radiation During Spaceight
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.
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 spaceight, such as the biological consequences of protons

and high LET radiation.
Image Credit: NASA
DNA is found in forms of life from bac-
teria to humans. Exposure to radia-
tion can damage DNA and cause major
health problems, including cancer. This
is a clear example of why radiation re-
search is important for long-duration
space missions.
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 pro-
tons, which are similar in their radiobiological effects to the low LET radiation in conventional
medical x-rays or gamma rays used in radiation therapy.
Background Image “Potato Amyloplasts” © 2004 by Mnolf, under a Creative Commons Attribution-Share Alike license.
The Risk of Cellular & Genetic Changes in Long-Term Space Travel
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
16
Spacecraft operate in highly isolated environments and as mis-
sions 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 ight to, or
even on, Mars. The space environment, however, represents a
unique factor inuencing the storage and processing of such
vital resources: Microgravity affects these consumables
in unexpected ways that make them all the more challeng-
ing 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 signicant reduction of Earth gravity.
For example, both environments are known to have very dusty surfaces with extensive depths
of very ne 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 ne particulate
material that then settles very slowly as a coating on any nearby surfaces.
Reduced gravity poses another unique problem in uid physics: Small forces that are often
masked by gravity on Earth can dominate uids in otherwise unexpected ways in space.
For example, in closed-circuit heating, cooling, and power generation cycles, the uids 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 ow 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.
One revolutionary and mission architecture-changing system involves on-orbit depots for
cryogenic rocket fuels. The scientic foundations required to make this Apollo-era notion a
reality center around understanding ows 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 scientic understanding of
how to retrieve and rene 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 scientic understanding.
Such advances point the way to a new era in dening space exploration.

With a growing body of data suggesting that water is almost universally prevalent in the solar system,
with signicant resources having been identied 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
The Nature of Fluid Physics in Space
Background Image of a bubble formed as a result of a Zeolite Crystal Growth experiment on ISS: NASA.
In physics, uid refers to any substance that continually responds to a shear stress; in addition
to liquids, particles like dust and gasses can ow as well, as do particulate materials such as
sand and dust. Martian soil nes are also signicantly 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 uid-like effects, both in space and
on planetary surfaces.
Recycling Air and Water in Spacecraft
Increasing stay times on the moon and Mars, as well as in-situ independence inside
the spacecraft, depend on efcient managing of uids. 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 benet signicantly from the use of a system for recycling both air
and water on long-duration spaceights. It is also proposed that any such mission would also
endeavor to produce a signicant proportion of its own food supply, during both legs of the
spaceight 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.
During spaceight, 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 m
2

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, uid-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.
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
17
Spacecraft operate in highly isolated environments and as mis-
sions 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 ight to, or
even on, Mars. The space environment, however, represents a
unique factor inuencing the storage and processing of such
vital resources: Microgravity affects these consumables
in unexpected ways that make them all the more challeng-
ing 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 signicant reduction of Earth gravity.

For example, both environments are known to have very dusty surfaces with extensive depths
of very ne 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 ne particulate
material that then settles very slowly as a coating on any nearby surfaces.
Reduced gravity poses another unique problem in uid physics: Small forces that are often
masked by gravity on Earth can dominate uids in otherwise unexpected ways in space.
For example, in closed-circuit heating, cooling, and power generation cycles, the uids 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 ow 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.
One revolutionary and mission architecture-changing system involves on-orbit depots for
cryogenic rocket fuels. The scientic foundations required to make this Apollo-era notion a
reality center around understanding ows 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 scientic understanding of
how to retrieve and rene 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 scientic understanding.
Such advances point the way to a new era in dening space exploration.
With a growing body of data suggesting that water is almost universally prevalent in the solar system,
with signicant resources having been identied 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.
The Nature of Fluid Physics in Space
Background Image of a bubble formed as a result of a Zeolite Crystal Growth experiment on ISS: NASA.
In physics, uid refers to any substance that continually responds to a shear stress; in addition
to liquids, particles like dust and gasses can ow as well, as do particulate materials such as
sand and dust. Martian soil nes are also signicantly 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 uid-like effects, both in space and
on planetary surfaces.
Increasing stay times on the moon and Mars, as well as in-situ independence inside
the spacecraft, depend on efcient managing of uids. 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 benet signicantly from the use of a system for recycling both air
and water on long-duration spaceights. It is also proposed that any such mission would also
endeavor to produce a signicant proportion of its own food supply, during both legs of the
spaceight and during the stay time on Mars—that is, if the crew was there long enough to
During spaceight, 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
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
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, uid-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.

Image Credit: NASA
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
18
The study of microgravity combustion has enabled
research designed specically for space explora-
tion, while also providing new insights into funda-
mental combustion processes for terrestrial appli-
cations. When combined with theory and numerical
models, microgravity combustion experiments have
enhanced our knowledge of basic combustion phe-
nomena, contributed to greater re safety for pres-
ent and future space missions, and provided insights
to practical industrial applications on Earth. Com-
bustion research typically focuses on the process by
which energy is released into a surrounding medium
in the form of ames; however, when studying re on
Earth, the effects of gravity are difcult 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 charac-
teristics that are important to combustion systems.
This knowledge can be used to select better materi-
als and to detect and suppress res more efciently.
Combustion and Fire Behavior in Reduced Gravity
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
res. 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 re.
Research on ignition and ammability 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 re 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 re. Because ame growth is a major concern in spacecraft
re safety, fundamental studies on solid fuel ammability of these materials are essential
to re safety in space.
Previous fundamental research has been applicable to re safety measures both in space
and on the ground. NASA free fall facilities have been used to eliminate, for eeting
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 ammability,
re prevention systems, and even suppression agents used to extinguish a re.
Fire Safety and Prevention in Space
The rst line of defense for stopping a re is prevention. NASA has developed screening
methods to identify acceptable materials and reduce their ammability. Currently, a
normal gravity test used for solid materials considers upward ignition and ame growth
where, if the ame 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.

In case of a re, early detection will minimize the damage it can cause. Relevant
questions are: what products of a re can be sensed faster and produce a more reliable
re detection? How can the sensor information be used to effectively ght the re? For
example, early investigations showed that the size of smoke particles emerging from
ames 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 re on-board a spacecraft, crewmembers could contain the ames
using standard suppressant methods, such as releasing gas spray or droplets, in addition
to approaches developed specically for this environment: Cutting off air ventilation
and depressurizing the spacecraft cabin. Fire suppressants used in spacecraft should be
efcient 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 identied for a variety of specic space applications.
Image Credit: NASA
Issues in Fire Behavior & Safety:
Background image © 2006 by B.J. Bumgarner, under a Creative Commons Attribution-NonCommercial-ShareAlike license.
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.
Pr event ion , D et e ct ion , Suppr e ssion
Image Credit: NASA
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
19
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
res. Flames are controlled by energy released from exothermic chemical reactions

and the interaction of this energy with the atmosphere. The microgravity combustion
a force that dominates terrestrial
effects in space to understand some of the more subtle and less-understood
Research on ignition and ammability 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
For this reason, an improved knowledge of combustion in reduced gravity is necessary
for adapting re 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 re. Because ame growth is a major concern in spacecraft
re safety, fundamental studies on solid fuel ammability of these materials are essential
Previous fundamental research has been applicable to re safety measures both in space
and on the ground. NASA free fall facilities have been used to eliminate, for eeting
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 ammability,
Fire Safety and Prevention in Space
The rst line of defense for stopping a re is prevention. NASA has developed screening
methods to identify acceptable materials and reduce their ammability. Currently, a
normal gravity test used for solid materials considers upward ignition and ame growth
where, if the ame 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.
In case of a re, early detection will minimize the damage it can cause. Relevant
questions are: what products of a re can be sensed faster and produce a more reliable
re detection? How can the sensor information be used to effectively ght the re? For
example, early investigations showed that the size of smoke particles emerging from
ames 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 re on-board a spacecraft, crewmembers could contain the ames
using standard suppressant methods, such as releasing gas spray or droplets, in addition
to approaches developed specically for this environment: Cutting off air ventilation
and depressurizing the spacecraft cabin. Fire suppressants used in spacecraft should be
efcient 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 identied for a variety of specic space applications.
Image Credit: NASA
An important observation made in space was
that the absence of buoyancy caused a ame
to reshape into a sphere. Buoyancy is the driv-
ing force in the plume because of high temper-
atures and density differences. Verifying and
understanding analytical and experimental
results, as well as identifying and clarifying
the interactions among suppression agents,
ames, and surfaces in reduced gravity, will
provide insight into the fundamental differ-
ences in balances between buoyancy and oth-
er forces. This basic research could contribute
to the development of improved re-suppres-
sion systems.
Issues in Fire Behavior & Safety:
Background image © 2006 by B.J. Bumgarner, under a Creative Commons Attribution-NonCommercial-ShareAlike license.
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.

Pr event ion , D et e ct ion , Suppr e ssion
Image Credit: NASA
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
20
Weighing the Matter of Materials
Every pound launched into space translates immediately into overall mission costs, in
both the nancial and spatial sense; therefore, any opportunity to safely reduce the total
spacecraft mass provides better economy and exibility 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.
Image Credit: NASA
Materials science successfully exploits the benets of inves-
tigating fundamental physical processes and phenomena
that are made more visible by the absence of gravity in
space. The research claried some of the roles of buoy-
ancy-driven convection, sedimentation, and hydrostat-
ic pressure in the processing of a range of materials,
including metals, alloys, glasses, ceramics, poly-

mers, 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 im-
provements in terrestrial production process-
es and the development of new benchmarks
for advanced quality. In the future, research in
this area might lead to new fabrication meth-
ods and materials synthesis—contributing
to the efcient manufacturing and design of
more products. The next stage of this research
should also reect the need to develop materi-
als that can help make long-duration spaceight
more affordable and safer.
Background Image “Dumbbell Nebula” Credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA.
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 uids 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 uids 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.
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.
The Matter of Materials
& the Relativity of Time
Image Credit: NASA
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
21
Every pound launched into space translates immediately into overall mission costs, in
both the nancial and spatial sense; therefore, any opportunity to safely reduce the total
spacecraft mass provides better economy and exibility 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
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

A test cell for the Mechanics of Granular Ma-
terials (MGM) experiment on STS-89 is com-
pressed 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 condi-
tions, 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.
Image Credit: NASA
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.
Background Image “Dumbbell Nebula” Credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA.
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 uids 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 uids 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.
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.
The Matter of Materials
& the Relativity of Time
Image Credit: NASA
Copyright © National Academy of Sciences. All rights reserved.
Research for a Future in Space: The Role of Life and Physical Sciences
22
for Space Suits
The human body has a resting core temperature of 37°C ± 1°C (98.6°F ± 1.8°F), with overheat-
ing being more of a concern than overcooling. The development of the space suit allows astro-
nauts 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.
Essential Te chnolo gie s
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 rst 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.
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.
Background Image
“SAFER Rescue System Tested” Credit: NASA.
Image Credit: NASA
Historically, space suits have included a portable life support system, articial atmosphere,
communications subsystem, and tools that enable crew members to accomplish critical mis
sion 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.
Image Credit: NASA
Engineering a Personal, Portable Atmosphere
The human body’s internal temperature uctuates 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 efcient 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 uctuations. 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.
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.