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IV
Space Science and the
Human Exploration Initiative
The NASA 90-Day Study reflects an initial attempt to identify the
scientific components of the HEI. It identifies five themes around which
the science elements of the initiative are developed and states that the
"fundamental scientific themes . . . can be uniquely addressed by the
Human Exploration Initiative." Several specific examples are presented of
scientific objectives in precursor flights to the Moon and Mars. The 90-Day
Study provides evidence of NASA's intention that scientific research be an
integral part of the HEI. Nevertheless, it is clear that much of the research
in the NASA scientific themes does not require an HEI.
It is useful to divide the scientific research issues into three broad
categories. First, there are scientific studies to enable the initiative-
those that must be done before humans can travel to Mars, perform
useful tasks, and return safely. Second are studies and experiments that
can only be conducted as a result of the envisioned long-term human
missions. Third are studies that may be undertaken in association with those
missions, but could be carried out otherwise if necessary. Any scientific
knowledge that might be obtained in association with long-term human
missions should be evaluated in competition with other modes of gathering
the same information (e.g., human-tended, telerobotics) and with other
scientific research goals. This competitive category of scientific research
should not be used as, nor considered to be, the primary justification for a
national commitment to human exploration of space.
21
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22
HUA~1N EXPLORATION OF SPACE
SCIENTIFIC KNOWLEDGE AS A
PREREQUISITE FOR HUMAN EXPLORATION
The most important issues of prerequisite scientific knowledge concern
those matters that are critical to human health and safety, including micro-
gravity effects on physiologic functions, the effects of radiation, controlled
environment life support systems, site-selection and contamination issues,
and the psycho-social aspects of prolonged exposure in a confined habitat.
In every pioneering effort there are risks, known and unknown, that are
intrinsic to the endeavor. Those responsible must make the fullest efforts
to reduce the known risks to reasonable levels and make clear the levels of
risk that remain. Potential hazards must be explored and countermeasures
devised to reduce risk. Research is required to explore the range of risk
and to devise reasonable countermeasures.
Life Sciences
Microgravity Issues
Data are incomplete regarding the effects of the microgravity environ-
ment on human physiology (including the cardiovascular, vestibular, and
immune systems); more research is also necessary on adequate counter-
measures. As noted in the NRC Strategy for Space Biology and Medical
Science, "If this country is committed to the future of humans in space,
particularly for long periods of time, it is essential that the large number of
uncertainties about the effects of microgravity on humans and other living
organisms be recognized and vigorously addressed." The 90-Day Study
envisions research to develop countermeasures to the effects of very low
gravity and to promote the basis for designing artificial gravity environ-
ments, if required. A rigorous research program would be based largely on
facilities available in an Earth-orbiting station, designed to gain an under-
standing of the effects of a microgravity environment on humans. As NASA
indicates, the results of this research will have significant implications for
mission architectures and mission time profiles.
Radiation Issues
Radiation from solar and galactic sources poses serious potential haz-
ards to human health. Predictions of solar flares and of solar flare particles
remain uncertain, but successful predictions are not prerequisites to human
spaceflight, if adequate shielding is provided. Research on prediction tech-
niques, one of NASAs objectives, should be vigorously pursued in parallel
with human exploration programs. The intent would be to provide the
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SPACE SCIENCE AND THE HUMAN EXPLORATION INITL4TTVE
23
earliest possible warnings, with minimal false alarms, of impending solar
flares and flare particles.
As the 90-Day Study indicates, it is important to learn more about the
relative biological effects of radiation fluences, particularly high-, galactic
cosmic rays and solar flare electrons and protons, and their relationship
to cancer and cataract induction, for example, in order to set meaningful
guidelines for radiation protection. The question of appropriate shielding
in flight, at an Earth~rbiting station, and on the Moon and Mars is complex
and requires further study. For example, NASA suggests that for modest
thicknesses of shielding, the secondary radiation arising from the interaction
of galactic cosmic radiation may be more harmful to living tissue than the
primary dose. Consideration should be given to undertaking early flights
during solar minimum conditions.
Controlled Environment Life-Support Systems
The 90-Day Study recognizes the challenge of providing a reliable,
cost-efficient life-sustaining environment in locations that are devoid of
food, air, water, and nutrients. NASA's vision of the HEI uses closed-
loop systems where practical to reduce logistic requirements and open-loop
systems where limitations in technology or operational capabilities dictate.
It would be useful, but not mandatory, to have fully-closed life-support
systems for brief visits to the Moon and to Mars. However, even for a
brief visit, it is desirable to recycle water. For prolonged stays on the
Moon and Mars, a completely closed regenerative system would be highly
desirable to reduce requirements for resupply. Several terrestrial closed-
loop experiments are under way and must be reviewed in the context of
the HEI and refined until they are successful. The next step should be
a test bed of a closed life-support system in micro~ravitv on or near an
Earth-orbiting station.
Contamination and Back Contamination
, "7 ,
Evidence from the Viking missions to Mars suggests that terrestrial
microorganisms have little or no probability of growth on that planet, but
that does not rule out the possibility that life exists or may have existed
there in the past. Although organic compounds and liquid water have not
been detected on Mars, there is no basis for precluding their existence.
There is, moreover, strong evidence that liquid water in large quantities
existed in the Martian past. Furthermore, new discoveries about unusual
biological niches on Earth, such as deep ocean thermal vents, illustrate the
diversity of biological habitats.
International law requires that activities in space be conducted to
avoid the harmful contamination of celestial bodies as well as introduction
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HUMAN EXPLORATION OF SPACE
of changes in the Earth's environment by extraterrestrial matter. For
example, a Mars robotic lander raises concerns about contamination of
Mars (referred to as forward contamination), while a Mars sample return
mission must deal with concerns about contamination of Earth (called back
contamination).
The NASA 90-Day Study envisions a series of unmanned precursor
missions to Mars to determine characteristics of the planet The knowledge
to be obtained is necessary for detailed mission planning, including dealing
with the contamination issue. The Great Exploration concept does not
include such precursor missions. The committee believes that, before
humans go to Mars, there will have to be a highly capable set of precursor
missions, whose precise definitions, numbers, and configurations require
detailed research strategy development. Such precursor missions will allow
assessment and management of some of the risks of carrying out a manned
mission. The risks are not limited to concerns simply with pathogens. While
the risk of Pathogens is admittedly low. the Potential cost.c are nn~.~iblv Vera
high.
, ~ ~ - ~ ~ r-~~~~~~~~ ~~~~ ~~~ rid ~ ~~~
Psychological Issues
As noted in the 90-Day Study, psychological effects arising during long-
duration sequestering of humans have been documented, for example, in
nuclear submarines and research programs in Antarctica. Although these
terrestrial analogs are useful, they do not adequately simulate conditions of
long-duration missions to Mars. NASA appropriately envisions continuing
research in the selection process for spacefarers. Issues of spacecraft
habitability, training and command structure, as well as crew mix require
study, including simulation. A review of research results to date indicates
that more is known about avoiding undesirable crew characteristics than is
known about selecting crew for desirable traits. Clearly, the psychological
profiles for individuals and for crew composition should be well understood,
to reduce risks on long voyages. As is the case with most risks to humans
arising from long stays in the microgravity environment, technological
advances in nuclear and other propulsion systems could alleviate some
adverse effects by reducing mission duration.
Physical Sciences
Because the use of local resources is likely to be an essential feature
of the mission architecture, additional scientific knowledge will be required
about surface materials, features, and structures, both on the Moon and
Mars. Four of the five reference approaches in the 90-Day Study incorpo-
rate extraction of oxygen from lunar materials.
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SPACE SCIENCE AND THE HUMAN EXPLORATION INITL4T[VE
25
Present knowledge of lunar and Martian surface features is adequate
for lander modules, provided that high-resolution imagery is incorporated
for terminal guidance to a landing that can be directed over a sufficiently
large target radius. Additional knowledge will be required for site selection,
however, if the astronauts will be expected to carry out significant research
while on the surface. Uncertainties also exist concerning the bearing
strength of the Martian surface in areas of possible landing sites.
In the case of the Moon and a possible long-term lunar base, the flux
of micrometeorites and its variability are major uncertainties that can affect
the livability of a lunar station. As described in both the Sunday Study
and The Great Exploration, covering the station with lunar regolith is one
possible way to reduce the hazards from micrometeorites and radiation.
A fuller examination of research emphases in this area is needed before
precursor mission concepts are developed.
RESEARCH OPPORTUNITIES TO BE DERIVED FROM
PROLONGED HUMAN SPACE MISSIONS
The NASA 90-Day Study describes a variety of opportunities presented
by the HEI to advance scientific understanding through both the robotic and
human exploration phases of the HEI. The opportunities are organized into
a series of scientific themes. Several themes pose questions that challenge
astronomers, and NASA notes, for example, that the Moon offers a number
of advantages as a site for astronomical observatories.
The committee believes the Moon could offer potentially unique re-
search opportunities for a number of space science disciplines, including
astronomy. However, the concept of an astronomical observatory on the
Moon needs to be examined more critically than was suggested in the
NASA report. Specifically, lack of seismic activity does not seem to be a
major feature in determining whether the Moon should be used for inter-
ferometry. Attractive features include the dark and cold sly advantages
that come from being away from the Earth, and the advantages of building
large structures in fractional gravity.
Before establishing a lunar base to be used for scientific research, a
number of significant issues need to be understood in order to ensure the
long-term utility of the base for research purposes. For example, depending
upon the specific research objectives, evaluations should be made of the
effects on instrumentation of such features as the micrometeorite flux,
the solar wind and solar flare particles, and the electric and magnetic
environments on the surface at different lunar phases. In addition, attention
will have to be given to the interactions between a human presence and
specific scientific instrumentation (e.g., outgassing, vibration, dust, and
electromagnetic interferences).
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HUMAN EXPLORATION OF SPACE
Additional research opportunities on and from both the Moon and
Mars are sketched in the 90-Day Study. There will undoubtedly be op-
portunities for the HEI and the space sciences to advance together. Each
scientific opportunity to be derived from human space exploration should
be defined and evaluated, with consideration of its relative priority in the
research strategy of the appropriate discipline, and an assessment of the
most effective means to achieve it.
Representative terms from entire chapter:
space science
