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INTRODUCTION 20
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1
Introduction
THE HUMAN EXPLORATION OF SPACE
On July 20, 1989, President George Bush set an ambitious vision before
the American people: to go "back to the Moon, . . . . And this time, back to stay.
And then—a journey into tomorrow—a manned mission to Mars."1 This
proposal to expand human presence in the solar system has been given a
number of different names, including the Human Exploration Initiative, the
Moon/Mars program, Mission from Planet Earth, and, most recently, the Space
Exploration Initiative (SEI). In this report, the term "Moon/Mars program" is
used to refer generically to any future program directed toward the human
exploration of the Moon and Mars.
In the last decade, many committees, commissions, and studies have
assessed the future of the U.S. space program and have come to broadly similar
conclusions regarding the future of human spaceflight. The most recent major
assessment, performed by the Stafford Commission (or Synthesis Group) in a
report2 submitted to Vice President J. Danforth Quayle on May 3, 1991, set
forth six defining themes to guide human exploration:
1. Increase our knowledge of the solar system and the universe;
2. Rejuvenate interest in science and engineering;
3. Refocus the U.S. position in world leadership away from the military to
the economic and scientific spheres;
4. Develop technology that has terrestrial application;
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INTRODUCTION 21
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5. Facilitate further space exploration and commercialization; and
6. Boost the U.S. economy.
The fundamental premise of a Moon/Mars program, given the overarching
goal of human presence and activity beyond Earth, is directly articulated by the
first theme, an increase in knowledge of the universe. Thus "the Space
Exploration Initiative is an integrated program of missions by humans and
robots to explore, to understand and to gain knowledge of the universe and our
place in it."3
As its name suggests, the Synthesis Group's report was the distillation of a
nationwide outreach campaign to ascertain the nation's space exploration
aspirations. The group devised four broad concepts, or architectures, each
embodying an alternative goal. The first emphasizes an accelerated human
mission to Mars, with an intermediate return to the Moon. The second
concentrates on scientific research on the Moon and Mars. The third provides
for long-term habitation on the Moon, accompanied by a Mars exploration
phase. The final architecture envisages the utilization of in situ lunar and
martian resources to expand human capabilities in the inner solar system.
The report of the Synthesis Group proposed a strategic approach with its
use of "waypoints." Each waypoint describes a level of capability that is, in
itself, a significant achievement. At each waypoint the accumulation of
infrastructure, technology, and knowledge would allow selection of both the
emphasis and detailed implementation needed to achieve the next waypoint.
The architecture is thus an assemblage of successive waypoints.
While not intended as detailed blueprints for the execution of a program of
human exploration, the architectures characterize broad alternative goals for a
Moon/Mars program. Science plays a major, albeit different, role in each
concept. However, certain recurring scientific elements are found in all four
architectures and, incidentally, in previous studies of the human exploration of
space. These common themes include the following:
• The principal barriers to human exploration, particularly of Mars, are
uncertainties in medical science. These uncertainties include, in
particular, the physiological and psychological burdens placed on the
crews and the acceptable level of risk that can be assumed;
• A mix of robotic and human exploration missions. The former
(precursors) may provide information necessary for the planning and
successful execution of the latter or may undertake purely scientific tasks
(although the report of the Synthesis Group did not emphasize their
scientific potential);
• Initial human activities on the Moon. Some are specifically preparatory
for Mars missions. Others deal with study or use of the Moon for science;
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INTRODUCTION 22
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• The prime objectives of the Mars missions are exploration and science; and
• Significant technical advances are required if humans are to return to the
Moon and travel on to Mars. These are primarily engineering
developments of existing or understood technologies rather than the
development of totally new scientific or technological approaches.
The Space Studies Board's Committee on Human Exploration (CHEX)
presumes that, eventually, one of these architectures, or perhaps even a new
theme, could be selected to provide a focus for Moon/Mars exploration. Once
this is done, the subordinate objectives can be deduced and mission planning
begun.
Regardless of which specific architecture is ultimately selected, human
exploration of the Moon and Mars will be a long-term program of progressively
more complex and demanding missions. These will challenge the nation's
technical capabilities, management skills, and, perhaps, financial resources.
SCIENCE AND THE HUMAN EXPLORATION OF SPACE
Ever since the successes of the Apollo program 20 years ago, the future
directions of the U.S. program of human spaceflight have been a matter of
discussion, debate, and controversy within the government and the scientific
community and among the public. A report on space policy by the National
Academy of Sciences and the National Academy of Engineering stated 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."4 Nevertheless, the U.S. research community is
obliged to provide the best and most constructive scientific advice it can to
shape the political and technical decisions regarding piloted flight. This role is
consistent with the recommendation of the Augustine Committee that science is
"the fulcrum of the entire space effort."5
Part of the task facing the scientific community is determining what
knowledge is prerequisite for prolonged human space missions. However, these
prerequisites depend on the goals of such missions. If the goal of future space
missions were solely to satisfy the "human imperative" to explore or to enhance
national prestige or other nontechnical and nonscientific objectives, there would
be a limited set of requirements. There would, for example, be relatively little
need for precursor robotic missions to characterize the martian surface, because
sufficient data are at hand from the Viking mission to allow selection of a safe
landing site. But because the goals of most Moon/Mars concepts to date do
include the expansion of
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INTRODUCTION 23
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knowledge and other objectives such as long-term habitation and utilization of
in situ resources, the set of prerequisites is larger. For example, a martian
landing site must not only be safe but must also be desirable from a scientific
perspective. This creates a need for precursor robotic missions and provides
linkages between the scientific knowledge that is prerequisite for human
exploration and the scientific opportunities deriving from such a program.
The relative role of humans and robotic probes in space exploration has
long been a contentious issue. If the acquisition of knowledge were the only
goal, then the criteria for selecting between humans and robots would be clear:
select the most cost-effective method of obtaining the desired results. The
Augustine report recognized the important role humans can play in exploration.
However, it went on to say that "in hindsight . . . it was . . . inappropriate in the
case of the Challenger to risk the lives of seven astronauts and nearly one fourth
of NASA's launch assets to place in orbit a communications satellite."6 A
rational approach is to use robots until we can define objectives for which
humans are essential. We could also conduct experiments to determine the
contribution to field exploration that is gained by having humans in situ. No
compelling case has yet been made that human exploration is necessary to
accomplish the goals of lunar and martian science or, for that matter, any other
goal except the "human imperative" to explore. The report of the Synthesis
Group gives five visions other than science. However laudable these other
visions are, there has been no cost-benefit analysis to show that human
exploration is the best way of achieving them.
The tension between the science and nonscience goals suggests the
following criteria for selection between human and robotic options. Robotic
probes should be used to provide enough information to:
1. Optimize the sites chosen for human exploration. Mars especially, but
also the Moon, presents varied environments, and the number of sites
astronauts can visit will be limited, as will be the range of their traverses
at each site; and
2. Define a set of scientifically important tasks that can be well performed
by humans in situ.
The first criterion should not be interpreted to mean that there is currently
a scientific justification for human exploration. Nor does the second demand (at
least initially) that scientific tasks would be best and most cost-effectively
performed by humans. It is possible that future experiments and flight
experiences will show that some tasks are better, and perhaps more cost-
effectively, performed by humans, given the state of the art of robotic
technology. If this should turn out to be the case, a scientific justification for
human exploration might evolve.
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INTRODUCTION 24
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The inclusion of science goals in a Moon/Mars program raises two serious
concerns for the scientific community. The first is that human exploration may
displace other programs and initiatives that have a higher scientific significance
or priority. The second concern is that the scientific objectives be of high
quality and be competitive with other scientific opportunities. Toward this end,
the scientific component of human exploration should be managed so that:
1. The stated scientific objectives of the human exploration program are
achievable with a high probability of success;
2. The architecture is flexible and able to respond to new scientific
discoveries and, thus, to ensure that the scientific benefits of the program
are maximized;
3. Scientific advice is included in day-to-day decisions on the strategy and
implementation necessary to execute the programs; and
4. All goals (e.g., scientific research, human presence, utilization of
resources) of a Moon/Mars program are clearly stated and represented in
project management in such a manner that open and effective decision
making can be accomplished.
Management issues will be dealt with in depth in the third CHEX report;
they are mentioned here to emphasize the necessity to deal with the approach to
science management ab initio.
ENABLING SCIENCE
A Moon/Mars program requires the acquisition of scientific data either
prior to, or in conjunction with, actual piloted flight and planetary surface
activity. Establishing the requirements for such data is, to a major extent, a task
for the scientific community. This entails both a responsibility and an
opportunity. The responsibility is to state clearly what scientific data are
essential to enable a Moon/Mars program and to propose programs and
mechanisms to acquire, analyze, and interpret data, and to assure the overall
quality of the scientific research. An opportunity arises because some enabling
data will have a value over and above that immediately required by a program
of human exploration. Such information might, however, be accorded a
different priority in the absence of a program of human exploration.
Developing the full set of requirements for enabling data is an iterative
process that will depend eventually on the specific architecture selected. If, for
example, establishing astronomical observatories on the Moon becomes a goal,
particular information on the lunar environment that might otherwise not be
needed will become essential. Similarly, if long-term habitation becomes a goal
of lunar or martian exploration, then the search for in situ
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INTRODUCTION 25
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resources such as water becomes a high priority simply because of the major
impact that easily recoverable resources would have on the entire program.
Conversely, consideration of a set of enabling requirements derived from a
particular architecture, and the ability to satisfy those requirements, could
produce changes in the architecture. For example, if it turns out to be
impossible to devise countermeasures to the deleterious effects of long-term
exposure to microgravity, then the development of a vehicle that incorporates
artificial gravity or the development of advanced propulsion systems with
decreased transit times may be the only practical options.
Scientific information is clearly needed to assure the safety of humans and
the effectiveness of human and machine operations. Although the Apollo
missions have proven that humans can undertake brief expeditions to the Moon,
the prospect of long-term or permanent habitation raises serious safety issues,
particularly where current knowledge is only rudimentary. Apollo data provide
some clues as to areas in which our ignorance harbors the greatest potential
dangers. These areas include the long-term and short-term prediction of solar
flares,7 the character of the interplanetary meteoroid flux, the detailed nature of
the lunar subsurface, and the possible detrimental effects of long-term
interaction with the ubiquitous lunar dust.
Some of the basic knowledge about the atmosphere and surface of Mars
required for human exploration is already in hand. The United States
successfully operated two robot landers for more than one martian year. Yet,
despite the wealth of data gathered by the Viking probes, extensive human
activities on Mars will require the acquisition of significant amounts of new
information. The variability of the martian atmosphere, the planet's surface and
subsurface characteristics, and the risk of volcanic activity must be studied. The
existence or abundance of significant, life-critical resources needs to be
determined. Attention must be given to avoiding the transport of
microorganisms from Earth and vice versa. The identification of likely abodes
of any past life will follow from a better understanding of the martian
environment and its history.
Precursor robotic missions (including sample return missions) can permit
analyses that would greatly improve the selection of landing and exploration
sites that could, in turn, enhance the science to be accomplished by human
exploration. A Mars sample return mission may be desirable to settle questions
of forward contamination and back contamination. Indeed, the Space Studies
Board has recommended that "the next major phase of Mars exploration for the
United States involve detailed in situ investigations of the surface of Mars and
the return to Earth for laboratory analysis of selected martian surface samples."8
In examining the enabling science for the human exploration of space,
CHEX identified two categories of research topics, each with differing de
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INTRODUCTION 26
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grees of urgency. Critical research issues are those related to conditions known
to be life-threatening or seriously debilitating: they are the potential
''showstoppers'' of human exploration. The other category, research for mission
optimization, includes issues that, based on current knowledge, do not appear to
represent immediate threats to the health and well-being of humans in space.
They could, however, result in reduced astronaut performance in flight or on the
surface of the Moon or Mars, leading to a suboptimal mission. They could also
impact the health of astronauts long after a mission is completed. In addition, it
must be recognized that our current state of ignorance about prolonged human
spaceflight leaves open the possibility of phenomena that cannot be anticipated.
CHEX emphasizes that, as new information is acquired, some optimal
performance issues could become critical to ensuring the well-being of
astronauts. If, for example, it is necessary to minimize payload mass,
development of a partially closed, if not fully closed, life support system could
become mandatory for missions to Mars.
The exploration of Mars by humans will be one of the most complex,
challenging, and expensive technical endeavors ever attempted. These missions
will, however, be carried out by even more complex entities—humans. It is
therefore vital that as much effort be put into understanding the effects of the
space environment on humans as has been put into understanding the
mechanisms of getting a spacecraft to Mars and back.
It is widely assumed that since a small number of astronauts have survived
and operated for as long as a year in space, there are no major physiological
problems that would prohibit long-term human exploration. This assumption is
unwarranted. An assessment of current research in space biology and medicine
shows that the major problems posed by prolonged exposure to microgravity
remain no nearer solution in 1993 than they were in 1961, the year of the first
human spaceflight. For reasons outlined in earlier reports,9 space biology and
medicine are in the very earliest stage of development as rigorous scientific
disciplines. These fields must mature if any attempt is made to send humans on
extended missions to Mars.
The danger posed by biomedical uncertainties is related to another
important matter, not often publicly stated—the role of courageous individuals.
Humans who venture into space must accept a degree of personal risk. But, as
the Challenger accident made clear, the public will not accept losses that can be
anticipated and avoided. A sustained program of human exploration must adopt
the prudent strategy of reducing to an acceptable minimum both the immediate
and long-term risks astronauts will face. Thus, the potential hazards of exposure
to radiation and microgravity must be addressed within the context of a
comprehensive program of health and safety. To do otherwise imposes
unacceptable risks on the entire human exploration enterprise.
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INTRODUCTION 27
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SPACE STATION FREEDOM
What role does Space Station Freedom play in the future human
exploration of space? The Augustine report recommended that the primary
objective of a space station should be life sciences research.10 The Space
Studies Board strongly affirms the position that a suitably equipped space-based
laboratory is required to study the physiological consequences of long-term
spaceflight.11 The 1987 report of the Space Studies Board's Committee on
Space Biology and Medicine laid out the critical requirements for such a space
station.12 They include:
1. A dedicated life sciences laboratory with adequate crew to conduct
research;
2. A variable-speed centrifuge of the largest possible dimensions;
3. Sufficient numbers of experimental subjects (humans, plants, and
animals) to address the stated scientific goals; and
4. Sufficient laboratory resources, including power, equipment, space,
computational facilities, and atmosphere, to support the above research
requirements.
NASA's current plans for Space Station Freedom are the subject of much
controversy because of the project's escalating cost, lengthening construction
schedule, and declining capabilities. On several occasions, the Space Studies
Board has expressed concern that the current, descoped design of Space Station
Freedom does not meet all the basic research requirements outlined above13 and
therefore will not fulfill its role as the first and necessary step in the human
exploration of space. This is especially true if we are to use Space Station
Freedom to perform the necessarily long program of enabling biomedical
research and still meet the oft-stated goal of landing humans on Mars by 2019.
The prudent strategy is, as the Augustine report recommended, to be flexible
and not set a rigid schedule for the exploration of Mars by humans. However,
the difficulties currently being experienced by the space station project do not
negate the essential need for such a facility to perform the enabling research on
human adaptation to the microgravity environment necessary for a Moon/Mars
program.
INTERNATIONAL CONSULTATION AND COLLABORATION
The magnitude and comprehensive nature of a Moon/Mars project will
present unprecedented opportunities for cooperation with other nations. Just as
other countries will play important roles in building the spacecraft and systems
to support human exploration, so too will they be intimately involved in both
the scientific research necessary to enable human explora
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INTRODUCTION 28
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tion of the Moon and Mars, and in the enabled science opportunities arising
from such explorations.
To a great degree, space science is already broadly international. A
multitude of mechanisms exist for involving the most creative minds around the
world in space science, from canvasing the international community to
determine scientific objectives to inviting participation in specific missions. Just
as the space hardware programs of other countries have matured, so also have
their space science capabilities; thus they will expect to be treated as equal, not
junior, partners in the human exploration enterprise. CHEX believes, therefore,
that a consensus of the international space research community on the scientific
goals and objectives of a Moon/Mars program, and on a strategy for their
implementation, is essential to the development of any framework for
cooperation in the overall human exploration program.
NOTES AND REFERENCES
1. President George Bush, Remarks by the President at 20th Anniversary of Apollo Moon
Landing, 20 July, 1989, The White House, Washington D.C.
2. 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.
3. See Ref. 2, p. 2.
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, p. 14.
5. 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, p. 5.
6. See Ref. 5, p. 3.
7. It is worth noting that the crews of Apollos 16 and 17 were very lucky in that their flights
bracketed the large flare of August 4, 1972. If the mission timings had not been so fortuitous,
the astronauts could have suffered potentially fatal exposure to radiation.
8. Space Studies Board, International Cooperation for Mars Exploration and Sample Return,
National Academy Press, Washington, D.C., 1990, p. 1, p. 3, and p. 25. See also, Space Studies
Board, 1990 Update to Strategy for the Exploration of the Inner Planets, National Academy
Press, Washington, D.C., 1990, p. 40, and Space Science Board, Strategy for Exploration of the
Inner Planets: 1977–1987, National Academy of Sciences, Washington, D.C., 1978.
9. See, for example, Space Science Board, A Strategy for Space Biology and Medical Sciences
for the 1980s and 1990s, National Academy Press, Washington, D.C., 1987.
10. See Ref. 5, p. 29 and p. 47.
11. Space Studies Board, Assessment of Programs in Space Biology and Medicine 1991,
National Academy Press, Washington, D.C., 1991.
12. See Ref. 9, pp. 13-16.
13. See Space Studies Board, Space Studies Board Position Paper on Proposed Redesign of
Space Station Freedom, March 1991, and Space Studies Board Assessment of the Space Station
Freedom Program, March 1992.
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