Scientific Prerequisites for the Human Exploration of Space, Executive Summary, NRC 1993

Status Report From: National Research Council
Posted: Friday, January 1, 1993

Full Report

Executive Summary

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 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.

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.

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.


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.

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.

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