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Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
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The Human Exploration of Space
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EXECUTIVE SUMMARY 15
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Executive Summary
"To expand human presence and activity beyond Earth-orbit into the solar
system"1 was the goal established by President Ronald Reagan in 1988 for the
nation's program of piloted spaceflight. This goal formed the basis for the
subsequent proclamation by President George Bush on July 20, 1989—the 20th
anniversary of the Apollo 11 lunar landing—in which he proposed that the
nation go "back to the Moon, . . . . And this time, back to stay. And then—a
journey into tomorrow—a manned mission to Mars."2 The resulting long-term
program to expand the human presence in the inner solar system has been called
many things, including the Human Exploration Initiative, the Space Exploration
Initiative (SEI), and the Moon/Mars program. The Advisory Committee on the
Future of the U.S. Space Program identified these objectives as Mission from
Planet Earth.3
It is a long way from the broad goals of human exploration to a program of
implementation, with many political, technological, and scientific hurdles to be
overcome. Do successive administrations and congresses, as well as the
American people, have the desire to dedicate necessary national resources to
support such an ambitious program? Do they have the will and patience to
support a program lasting for several decades? Can humans function effectively
on the Moon for long periods of time? Can they survive a lengthy mission to
Mars? What will they do when they get there? These are but a few of the
myriad questions to be addressed before our species can realize the ancient
dream of human voyages to, and eventual settlement of, our neighboring planets.
Copyright © National Academy of Sciences. All rights reserved.
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EXECUTIVE SUMMARY 16
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THE ROLE OF SCIENCE
The role of science in human exploration is paramount and its challenges
no less daunting than those facing the engineering community. New scientific
data concerning the health and safety of astronauts are essential prerequisites
for the human exploration of space. Research must be done to understand and
alleviate the deleterious effects of microgravity on human physiology, the risks
posed by radiation in space, and the environmental stresses humans will
experience travelling to and operating on and around other planetary bodies.
The U.S. scientific and engineering community is obliged to provide the best
and most constructive advice to help the nation accomplish its space goals, as
was stressed in a 1988 space policy report to the newly elected president by the
National Academy of Sciences and the National Academy of Engineering.4 To
that end the National Research Council's Space Studies Board established the
Committee on Human Exploration (CHEX) and charged it, as its first
responsibility, to determine what scientific questions need to be answered
before humans can undertake extended missions to the Moon and travel to Mars.
Defining these scientific prerequisites entails a degree of judgment about
both our current state of knowledge of the relevant science and the potential
modes of mission implementation. CHEX determined that some issues are
critical to the basic survival and elementary functioning of humans in space.
Other issues concern the effectiveness and efficiency of operations and their
impact on overall mission success. The line between the two is sometimes
fuzzy, and the committee anticipates that with time crossover will occur.
Beyond the information needed to provide for the basic health and well-
being of astronauts operating in extraterrestrial environments, the expansion of
human presence and activity into the solar system does not demand any a priori
scientific research component. Nor is a Moon/Mars program driven by any
demands for scientific discovery. The latter view is expressed in the National
Academies' 1988 space policy report, which states that "the ultimate decision to
undertake further voyages of human exploration and to begin the process of
expanding human activities into the solar system must be based on nontechnical
factors."5 Given a nontechnical decision, what then is the proper role of science?
That there is a role is not open to much debate. The Paine report,6 the Ride
report,7 the Augustine report,8 and the report of the Synthesis Group9 all
recommend, to varying degrees, that significant scientific research be conducted
in association with human exploration. In fact, "exploration" does not exist in
isolation from scientific research. There are, however, two distinctly different
categories of science that must be considered. There is the "enabling" science
required if we are to conduct human exploration at all. Then, there is the
''enabled'' science made possible, or significantly
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EXECUTIVE SUMMARY 17
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enhanced, because it is carried out in conjunction with a program of human
exploration. This report deals with the former topic. The latter is treated in a
preliminary fashion insofar as it impacts the scientific effectiveness of Moon/
Mars missions. For example, conducting certain preliminary robotic missions to
the Moon and Mars can result in a more effective scientific return from eventual
human exploration. This report also contains some preliminary discussion of
technology requirements, aspects of international scientific cooperation, and the
approach used to manage the scientific component of a program of human
exploration.
ENABLING SCIENCE
In establishing the scientific prerequisites for the human exploration of
space, CHEX has identified two broad categories of enabling scientific
research. This classification is based on the degree of urgency with which
answers are needed to particular questions before humans can safely return to
the Moon or travel to Mars.
Critical Research Issues
The lack of scientific data in some areas leads to unacceptably high risks to
any program of extended space exploration by humans. These critical research
issues concern those areas that have the highest probability of being life
threatening or seriously debilitating to astronauts and that are thus potential
"showstoppers" for human exploration. The areas in which additional scientific
information must be obtained prior to extended exploration of space by humans
include the:
1. Flux of cosmic-ray particles, their energy spectra, and the extent to which
their flux is modulated by the solar cycle;
2. Frequency and severity of solar flares;
3. Long- and short-term effects of ionizing radiation on human tissue;
4. Radiation environment inside proposed space vehicles;
5. Effectiveness of different types of radiation shielding and their associated
penalties (e.g., spacecraft mass);
6. Detrimental effects of reduced gravity and transitions in gravitational
force on all body systems (especially the cardiovascular and pulmonary
systems) and on bones, muscles, and mineral metabolism, together with
possible countermeasures;
7. Psychosocial aspects of long-duration confinement in microgravity with
no escape possible and their effects on crew function; and
8. Biological aspects of the possible existence of martian organisms and
means to prevent the forward contamination of Mars and the back
contamination of Earth.
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EXECUTIVE SUMMARY 18
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Optimal Performance Issues
The second category of research includes issues that, based on current
knowledge, do not appear to pose serious detriments to the health and well-
being of humans in space. They could, however, result in reduced human
performance in flight or on planetary surfaces and, thus, in a less than optimal
return from the mission. Some of these issues may become critical research
issues relative to long-term human spaceflight and return to terrestrial gravity
following extended flights, or when extraterrestrial habitation is considered.
Research issues related to optimal mission performance include the:
1. Vestibular function and human sensorimotor performance;
2. Effects of the microgravity environment on human immunological
functions;
3. Long-term effects of microgravity on plant growth;
4. Feasibility of closed-loop life support systems;
5. Interplanetary micrometeoroid flux and its time dependence;
6. Surface and subsurface properties of the Moon and Mars at landing sites
and at the locations of possible habitats;
7. Hazards posed by martian weather and other martian geophysical
phenomena;
8. Atmospheric structure of Mars relevant to implementing aerobraking
techniques; and
9. Microgravity science and technology relating to long-duration
spaceflight. Two additional issues, while not directly related to human
performance, are included for their potential to significantly enhance and
optimize the scientific return of the mission:
10. Methods of detecting possible fossil martian organisms and the chemical
precursors of life; and
11. Availability and utilization of in situ resources (e.g., ice/water and
minerals) on the Moon and Mars.
References
1. President Ronald Reagan, Presidential Directive on National Space Policy, 11 February, 1988,
(Fact Sheet, page 1), The White House, Washington D.C.
2. President George Bush, Remarks by the President at 20th Anniversary of Apollo Moon Landing,
20 July, 1989, The White House, Washington D.C.
3. Advisory Committee on the Future of the U.S. Space Program, Report of the Advisory Committee
on the Future of the U.S. Space Program (the "Augustine report"), U.S. Government
Printing Office, Washington, D.C., 1990.
Copyright © National Academy of Sciences. All rights reserved.
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EXECUTIVE SUMMARY 19
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retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution.
4. Committee on Space Policy, Toward a New Era in Space: Realigning Policies to New Realities
(the "Stever report"), National Academy Press, Washington, D.C., 1988.
5. See Ref. 4, p. 14.
6. National Commission on Space, Pioneering the Space Frontier, The Report of the National
Commission on Space, Bantam Books, New York, 1986.
7. Office of Exploration, Leadership and America's Future in Space, A Report to the Administrator
by Dr. Sally K. Ride, August 1987, NASA, Washington, D.C., 1987.
8. See Ref. 3.
9. Synthesis Group, America at the Threshold, Report of the Synthesis Group on America's Space
Exploration Initiative, U.S. Government Printing Office, Washington, D.C., 1991.
Copyright © National Academy of Sciences. All rights reserved.
